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Guidelines for the design, construction, and operation of manual sanitary landfills

By: Jorge Jaramillo
Adapted and edited by: Francisco Zepeda
Washington, D.C. 1993


Contents

bbull.gif (150 bytes) 1. Backround
1.1 The importance of the solid waste problem
1.2 Solid waste effects on human health
1.3 Solid waste effects on the environment
1.4 Administrative aspects
1.5 Public cleaning service
1.6 Waste treatment systems
1.7 Waste final disposal
bbull.gif (150 bytes) 2. Sanitary landfill
2.1 What is a sanitary landfill?
2.2 Sanitary landfill methods
2.3 Basic principles of a sanitary landfill
2.4 Advantages of a sanitary landfill
2.5 Disadvantages of a sanitary landfill
2.6 Leachate
2.7 Gases
2.8 Cover material
bbull.gif (150 bytes) 3. Manual sanitary landfill
3.1 Panning
3.2 Selection of the site
3.3 Steps in design, construction and operation
3.4 Timetable of activities
3.5 Basic project
bbull.gif (150 bytes) 4. Site preparation and construction
4.1 Preparation of the site
4.2 Construction
bbull.gif (150 bytes) 5. Design of manual sanitary landfills
5.1 Basic information
5.2 Calculation of the volume needed
5.3 Calculation of the area required
5.4 Selection of the construction method
5.5 Calculation of the cell
5.6 Labor calculation
5.7 Cost analysis
bbull.gif (150 bytes) 6. Operation and maintenance
6.1 Operation
6.2 Maintenance
bbull.gif (150 bytes) 7. Administration and control
7.1 Administration
7.2 Control of the manual sanitary landfill
bbull.gif (150 bytes) Glossary of terms
bbull.gif (150 bytes) References
bbull.gif (150 bytes) Annexes
I. Examples from the design of manual sanitary landfills
II. Concepts in drawing and topography
III. Monitoring water quality
IV. Draft of a municpal act

Preface

In Latin America and the Caribbean, demographic growth, industrial development, urbanization, and other processes and consequences of economic development are producing a significant increase in the quantity and variety of solid waste that is being generated by the population of this Region.

Poor management of wastes is affecting both large cities and its marginal areas, and small rural populations. In many municipalities, the empirical management of urban cleaning services without technical, economic, and social standards leads to poor service planning and organization. As a consequence, public cleaning entails high operating costs that municipalities are forced to subsidize, allocating a substantial part of their budgets to this purpose.

The result is that most cleaning services are in permanent economic shortfall. Besides, due either to lack of resources, interest or technical knowledge, refuse is inappropriately disposed of inside or outside urban areas, creating scattered open dumps that constitute, inter alia, a social problem and a threat to public health.

Scavengers who sort and sell wastes from open dumps are a social problem since they work under precarious and risky conditions. These open dumps are a threat to public health because in addition to bad odors and aesthetic problem, are a breeding site for flies, rats, and other disease vectors, as well as a source of air pollution and contamination of surface and ground waters.

These problems could be controlled if final disposal could be carried out in a properly run landfill, which would also help to prevent pollution.

Urban cleaning service consists basically of sweeping, storage, collection, transportation, and final sanitary disposal of solid waste. Since disposal is the last step and economic resources are scarce, final disposal is the critical point in urban cleaning services in the Region.

The Pan American Health Organization, considering that manual sanitary landfills are available to municipalities since they do not require much technical or financial resources for their operation, has been promoting them as a final disposal practice in the countries.

To continue the effort and taking into account the need of numerous small cities and rural towns in the Region, the Environmental and Health Division, HEP/PAHO/WHO, through CEPIS, considered the preparation of this manual, which is particularly aimed at towns with less than 40.000 population.

The methodology presented in these guidelines was used successfully during the first phase of the urban cleaning program for municipalities of the Government of Antioquia, Colombia. We acknowledge the collaboration of the Planning Administrative Department of the Government of Antioquia for their collaboration, and for giving us permission to use the document they produced as the basis for these guidelines.

Through the dissemination of this document we want to contribute to improve the operation of cleaning services and, as a result, to enhance the environmental conditions and health of the population of the countries of Latin America and the Caribbean.

Horst Otterstetter
Director
Environment and Health Division

Presentation

This guide contains the basic principles for a manual sanitary landfill and is largely based on field experience from the first phase of the urban cleaning program for municipalities conducted by the Government of Antioquia, Medellín, Colombia. As well, it is based on the experiences I shared with technicians from different countries during visits to sanitary landfills in 1989, when I participated in the program for resident professionals of the Pan American Center for Sanitary Engineering and Environmental Sciences (CEPIS).

The main audience of this guide are local administrators and sanitation technicians. It is based on "Relleno Sanitario Manual", published by the Government of Antioquia, Planning Administrative Department, Medellín, the unit I work for and which authorized the use of this document. I would like to thank them for their collaboration.

I am also grateful to Mr. Francisco Zepeda Porras, Regional Advisor in Solid Waste of the Environmental Health Program (HPE), for his valuable orientation and to Mr. Alberto Flórez Muñoz, CEPIS Director, for the encouragement and support I received during my residence at that Center.

Finally, I would like to express that the purpose of preparing this guide was to facilitate the decision-making process to build manual sanitary landfills. Although these basic sanitation facilities are small in scale, they play an important role in improving community quality of life, preserving the environment and protecting natural resources.

Jorge A. Jaramillo
Sanitary engineer

1. Backround

1.1 The importance of the solid waste problem

In most countries, especially in certain regions, the problem of solid wastes is worsening due to rapid population growth, industrial development, changes in consumer patterns, higher life standards, and other factors that lead to environmental contamination and deterioration of natural resources.

Economic development is generally accompanied by increased generation of solid wastes, which plays an important role among the various factors that affect the health of the community. This reason triggers the search of solutions to the problem of waste management and final disposal.

1.2 Solid waste effects on human health

The importance of solid wastes as a direct cause of diseases has not been established yet. Nevertheless, concomitant with other factors, they are blamed for the transmission of certain diseases through indirect routes.

To better understand the effects of solid wastes on human health, it is necessary to distinguish between direct and indirect risks.

1.2.1 Direct risks to health

Direct risks are posed by contact with refuse containing human and animal excreta and hazardous materials. Those most at risk are garbage collectors that handle containers unsuitable for refuse storage, use inappropriate equipment, or do not wear clean clothes and protective gloves and shoes. People who make the sorting and separation of wastes are also under risk since their working conditions are the worst. The incidence of intestinal parasites is higher in both collectors and separators than among the general population. Besides, the rate of injuries in hands, feet and back, as well of hernias, wounds, respiratory diseases, and skin problems is higher than in industrial workers.

1.2.2 Indirect risks to health

Vector proliferation. Risks caused by unsuitable handling of refuse are mainly indirect and affect the public in general. They stem from the proliferation of vector diseases, such as mosquitoes, rats, and cockroaches that find food and adequate conditions for reproduction in solid wastes. Figure 1.1.

Examples of vector diseases are the following:

VECTOR

DISEASE

 

VECTOR

DISEASE

Flies

Typhoid fever
Salmonellosis
Dysentery
Infant diarrhea
Other infections

 

Mosquitoes

Malaria
Yellow fever
Dengue
Viral encephalitis

 

 

 

Cockroaches

Typhoid fever
Gastroenteritis
Intestinal- infections
Dysentery
Diarrhea
Leprosy
Food- poisoning

 

Rats

Bubonic plague
Murine typhus
Leptospirosis (Weil's disease)
Harverhill fever
Vesicular rickettsiosis
Diarrheal diseases
Dysentery
Rabies

 

 

 

FIGURE 1.1
Life cycle of the fly and its importance
in disease transmission

  • eeding refuse to animals (pigs, poultry, etc.) is not advisable as a final disposal practice, since it entails public health risks. Consuming pork fed with refuse causes trichinosis, cysticercosis, etc.

  • Air and land accidents due to decreased visibility caused by smoke and birds from garbage dumps near to airports and highways.

1.3 Solid waste effects on the environment

The most obvious environmental effect of inadequate refuse management is the aesthetic deterioration of cities and natural landscapes. This increasing problem is destroying the beauty of our few parks, beaches and landscapes. Figure 1.2.

1.3.1 Water pollution

The most serious but least recognized environmental effect of solid wastes is water pollution caused by dumping refuse into rivers and streams, and leachate from open dumps.

FIGURE 1.2
Disposal of solid wastes in open dumps

The dumping of refuse into streams produce organic load and depletes dissolved oxygen. It increases nutrients and algae causing eutrophication; kills fish; and generates unpleasant odors and color. As a result, this resource which is so important to water supply and recreation is being destroyed.

Refuse dumping into watercourses or along the streets obstructs gutters, and reduce the flow of channels. In the rainy season this can cause floods that may result in loss of crops, material goods, and even human lives.

1.3.2 Soil contamination

The accumulation of solid wastes in open dumps contaminates the soil, creates a public nuisance and reduces the value of the surrounding land. Uncontrolled disposal of hazardous wastes also pollutes the soil.

1.3.3 Air pollution

Smoke from frequent fires in open dumps reduces visibility, causes nasal and eye irritation, increases respiratory problems, and creates unpleasant odors.

1.4 Administrative aspects

In a community, one of the best indicators of health and quality of life is the cleanliness and beauty of the locality.

The management of solid wastes and its final sanitary disposal shows the quality of the local administration and the efficiency of its leaders, in particular, of the mayor. Through public cleaning services it is possible to evaluate political will, managerial capability, and responsibility toward public health and cleaning workers, as well as commitment to protect the environment.

It is important to emphasize that with appropriate technology and adequate planning and administration it is possible to reduce service costs, charging a tariff according to the payment capacity of the users.

"EVERYBODY TAKES PRIDE IN SHOWING A CLEAN CITY"

1.5 Public cleaning service

The public cleaning service consists of the following activities: separation, storage, in-house containerization, collection, sweeping, transportation, treatment, and final sanitary disposal of solid wastes, the latter one is indispensable in waste management. The user or waste producer is responsible for the first two activities, while the others are responsibility of the municipality or cleaning facility (Figure 1.3). In developing countries, refuse collection is one of the environmental sanitation problems that requires greater attention by governmental authorities and by research and financial agencies.

The following factors contribute to ill public cleaning services:

  • The service is in charge of personnel or politicians without technical training.

  • There is no awareness that solid waste management requires knowledge, research, projects and suitable structures and facilities that should be well operated and maintained.

  • There is the common belief that solid wastes have an economic value.

  • Local governments have economic limitations and meager financial resources earmarked for public cleaning.

  • Authorities have traditionally given little importance to public cleaning service.

Currently, waste management entails the evaluation of local and regional conditions to face it as a sanitary engineering problem that requires the cooperation of other professionals. It is also important to point out the role played by mid-level technicians, operators, cleaning service supervisors, and promoters of sanitation in solving solid waste problems.

FIGURE 1.3
Process of municipal solid wastes and urban cleaning

The first step, however, is in the hands of the government at all levels. The activities of international cooperation agencies are also of great importance.

At the national level it is necessary to take appropriate measures to regulate the management of solid wastes and also to promote the establishment of a national urban cleaning system.

At the regional level, plans, programs, and projects should be prepared to provide municipalities technical advisory services and support according to national sanitation policies.

At the local level, municipal governments should take action to improve cleaning service quality and to provide sanitary final disposal methods for their wastes. This should be one of the main concerns of local administrations, not only for sanitary reasons, but also to improve the beauty of the community. The old maxim: "Clean city, civilized city" should always be considered.

1.6 Waste treatment systems

The main objective of solid waste treatment is to decrease the risk of contamination and to protect the health of the population.

Among the alternatives considered, the best solution should be chosen according to local technical and socioeconomic conditions, bearing in mind contamination issues.

The main treatment methods to reduce waste volume are incineration, composting, and recovery. They are not considered, however, as final disposal methods since a sanitary landfill is required to dispose of the wastes produced.

1.6.1 Incineration

The incineration of solid wastes reduces the volume to about 10%, it produces inert material (scoria and ashes) and releases gases during combustion. This reduction is completed in special furnaces that require combustion air, turbulence, retention periods, and suitable temperatures. Poor combustion will generate smoke, ashes, and undesirable odors.

Incineration, except for hospital wastes, is not recommended for developing countries, even less for small communities for the following reasons:

  • Large initial capital is required.

  • Operational costs are beyond the capability of the communities.

  • Qualified technicians are required and they are not always available.

  • Its operation and maintenance are complex.

  • It is not flexible enough to treat additional quantities.

  • At times, auxiliary fuel is required when the calorific value of the refuse is low and contains high humidity.

  • Control equipment is needed to avoid air pollution, since no incinerator produces emissions completely free of pollution.

1.6.2 Composting

Composting is the process by which the organic content of the refuse is reduced by bacteriological action of the microorganisms contained in the refuse. The product of this process is the compost, which is a soil conditioner (not a fertilizer). Its commercial value, however, is less than the cost of production.

Composting could be an effective waste treatment method for developing countries because the organic content of the refuse is recovered. It also requires separation from other solid wastes, providing a good opportunity to initiate the recycling of other materials. Before deciding the construction of a composting plant, careful consideration should be given to whether there is a market for selling the product. Many plants in the world have failed because marketing issues were neglected.

In our Region, composting has had little success due to:

  • It requires waste separation.

  • It is not flexible enough to treat additional quantities.

  • The market for compost is not stable.

  • It demands large capital investment.

  • The cost of operating and maintaining the plant is high.

  • It requires qualified technicians to operate the plant.

  • The cost of transportation to rural areas is high.

Composting of organic market wastes may be advisable in some small communities where solid wastes may be processed manually. Care should be taken with the distribution costs, since they may increase total production costs.

1.6.3 Recovery

Up to now, the purpose of waste management systems has been to move materials from one place to another and dispose of them at the least cost. However, new ways to manage solid wastes are now under consideration due to the increasing generation of solid wastes, the complex treatment of new materials, the pressure to comply higher environmental standards, and the over exploitation of natural resources.

At the present time, in industrialized countries there is increasing awareness that the supply of raw materials is limited and that waste recovery may become an essential factor in natural resource conservation.

Recovery may be divided into three categories:

  • Direct reuse of a product or material that has been cleaned, repaired (bottles, containers, cardboard boxes) or reassembled (motors).

  • Recycling of wastes as raw material to produce new products of the same composition (broken glass, paper, cardboard, metals, plastics, etc.).

  • Use and transformation of wastes into different products (land recovery through sanitary landfill, conversion of organic wastes into compost) or into new sources of energy (biogas derived from anaerobic digestion of organic wastes, or heat recovery from incineration).

The materials found in refuse are traditionally separated manually at the place of origin, on the sidewalks, in the collector trucks, or at the final disposal site. In the Region, the latter practice is frequent in nearly all open dumps in large cities and even in small communities. Poor people working under risky conditions without sanitary protection and social security benefits usually perform this activity. For this reason, this practice should be avoided and an integral program with extended community participation should be promoted.

On the other hand, several countries in the world, especially in Europe, have a large number of facilities using mechanical separation with sophisticated equipment, however, operational and maintenance problems are common and efficiency is bellow the expected considering the high investment costs.

To date, the experience in developing countries with industrial plants for solid wastes has not been very encouraging and has often result in a complete failure.

Therefore, recovery at the source where wastes are generated is recommended for small communities. This offers the greatest benefits for manual labor and does not require large investment.

The municipality gains the following benefits from recovery or recycling of materials at the source:

  • Creation of organized employment through cooperative groups.

  • Reduction of solid waste volume to be collected and transported.

  • Less collection equipment is needed.

  • Useful life of sanitary landfills is expanded, therefore, there is less demand for land, which is getting scarcer and more expensive.

  • Income generation to partially cover cleaning service costs.

  • Less cost for providing cleaning services.

  • Conservation of natural resources and environmental protection.

The local administration and central government should foster the recovery of resources creating the market for recycled products through purchase centers or collecting points. Municipalities should increase public awareness on problems that stem from waste collection and should establish suitable ways to make such collection.

There must be environmental education campaigns aimed at the community to improve collection service and to facilitate the recovery of materials through waste separation. On the other hand, the market for recovered materials should be studied since no recovery system would be successful if the products can not be sold.

Worldwide, the trend is to maximize the recovery or recycling of refuse as the best solution to face this problem.

"The success of the recycling program depends on community participation and its main objective is environmental awareness to make recycling a general habit, with emphasis on the new generations." National Recycling Program (PRONARE), Ministry of Health, Colombia.

1.7 Waste final disposal

The main methods for waste final disposal are:

  • sanitary landfill

  • dumping into water streams or into the ocean

  • open dump

  • open burning

  • animal feed.

Sanitary landfill is considered the only environmentally sound alternative, since it does not involve major annoyance or hazards to public health.

The dumping of refuse into water streams, lakes, or oceans is unacceptable because it produces ecological imbalance and excessive nutrients and organic load to the water.

Open dumps are a serious public health problem because they favor the proliferation of insects and rodents that transmit diseases. Besides, the smoke produced by fires causes respiratory problems and the view of an open dump deteriorates the beauty of the surrounding area.

The feeding of animals with wastes should be prohibited due to the high risk of transmitting diseases to man. The feeding of animals with food wastes from hotels and restaurants may be allowed only if it is guaranteed that such wastes will be cooked at 100 oC for at least 30 minutes.

2. Sanitary Landfill 

Sanitary landfills have been, technically and economically, the best-suited technique for sanitary disposal of wastes in our Region. 

2.1   What is a sanitary landfill?

The sanitary landfill is a technique used for the final disposal of solid wastes that does not cause annoyance or threat to public health. It does not deteriorate the environment during its operation or after its closure. This technique uses engineering principles to deposit the waste in the smallest area possible, daily covering it with layers of soil, and compacting it to reduce its volume. Problems related to liquids and gases generated by the degradation of organic material are also dealt with in a landfill. 

2.2 Sanitary landfill methods

The construction and the sequence of operation in a sanitary landfill are mainly based on the topography of the land. They also depend on the source of the covering material and the depth of the water table. There are two different ways to construct a sanitary landfill: the trench method and the area method. 

2.2.1 Trench or ditch method

The trench or ditch method is used in flat regions and consists of periodically digging trenches two or three meters depth with an excavator or tracked dozers. It should be noted that there have been trenches dug up to seven meters depth. The soil taken out is stockpiled for later use as covering material for a subsequent trench. Wastes are placed in the trench, and then they are spread, compacted and covered with soil.

Care must be taken when it rains because the water may flood the ditches. Therefore, canals must be built on the perimeter to collect and divert the water and to provide internal drainage. In extreme cases, it may be necessary to pump out the accumulated water. The sidewalls of the ditches have to keep the slope of the excavated soil.

Ditch excavation requires favorable conditions regarding water table depth and adequate soil. Lands with a high water table or very close to the surface are not suitable because groundwater would be contaminated. Rocky soil is not adequate since excavation is very difficult. (Figure 2.1). 

FIGURE 2.1
Trench method for constructing a sanitary landfill

 

2.2.2 Area method

In flat areas where pits or trenches cannot be dug, refuse can be deposited directly on top of the original soil, elevating the level a few meters. Cover soil should be brought in or extracted from the surface layer. In both cases, the first cells are constructed with a smooth gradient to prevent slides and create stability as the landfill rises. Figure 2.2. 

FIGURE 2.2
Area method for constructing a sanitary landfill

This method can be used for filling natural depressions or abandoned quarries a few meters depth. The cover material is dug from the slopes or from a nearby place to avoid increased transportation costs. The unloading operation and construction of the cells should be done from the bottom up.

The cells of the landfill are supported on the natural gradient of the land, the incoming refuse is spread and compacted at the base of the slope and covered daily with a layer of 0,10 m to 0,20 m of soil. The operation continues along the terrain maintaining a smooth gradient of about 30 degrees on the slope and 1 to 2 degrees on the surface.

  

FIGURE 2.3
Area method to fill depressions 

FIGURE 2.4
Combination of both methods for constructing a sanitary landfill

2.2.3 Combination of both methods

Since these two methods of constructing sanitary landfill are similar, they may be combined to better use the land and cover material and to increase operation performance. 

2.3 Basic principles of a sanitary landfill

It is important to emphasize some basic principles:

  • Good supervision assures that the refuse is unloaded, covered and compacted efficiently to keep the landfill in good conditions. A manager should be responsible for the operation and maintenance of the landfill.

  • The height of the cell is also an important factor. For a manual sanitary landfill, a height between 1,0 m and 1,5 m is recommended to diminish land settlement and to achieve greater stability.

  • It is essential that refuse be covered daily with a layer of 0,10 m to 0,20 m of soil or similar material.

  • Solid wastes should be compacted into layers of 0,20 m to 0,30 m thick and then the entire cell must be covered with soil. The success of daily operations depends on it. It will also assure greater density and longer useful life for the site. A simple rule states that when a sanitary landfill has greater density, it is more efficient and environmentally sound.

  • Runoff should be diverted whenever possible to prevent its entry into the sanitary landfill.

  • Leachate and gases must be controlled and drained to maintain the best operating conditions and to protect the environment.

  • The final cover, 0.40 to 0.60 m width, is placed using the same method for daily covering. It should sustain the vegetation and should facilitate the integration of the landfill in the natural landscape.

2.4 Advantages of a sanitary landfill

  • Sanitary landfills, as a final disposal method for urban solid wastes, are the best alternative for the countries of our Region. However, it is essential to provide the financial and technical resources for planning, design, construction, operation, and maintenance.

  • The initial capital investment is lower than that required to implement either incineration or composting methods.

  • Low costs of operation and maintenance.

  • It is a complete and final method that can receive all types of municipal solid wastes, eliminating the problem of ashes from incineration and materials that do not degrade during composting.

  • It generates employment for unskilled laborers, who are readily available in developing countries.

  • In large sanitary landfills that receive more than 200 tons of refuse per day, methane gas may be recovered and used as an alternative source of energy.

  • It can be located near an urban area if there is available land. The costs of transportation are then reduced and the landfill can be better supervised.

  • It reclaims lands that can be used for the construction of parks, recreational areas, or sports fields.

  • A sanitary landfill can begin to operate in a short time.

  • It is very flexible since it does not require permanent nor fixed installations and can accept additional amounts of waste with few increases in personnel.

2.5 Disadvantages of a sanitary landfill 

  • The acquisition of land is the first barrier to construct a sanitary landfill as opposition from the public may be strong due to factors such as:

  • - Lack of knowledge of the sanitary   landfill technique.

  • - The term "sanitary landfill" is associated with an "open refuse dump."

  • - Mistrust of local administrations.

  • - Rapid urbanization has increased land cost. This means that a sanitary landfill has to be located far from collection routes,
            rising the cost of transportation.

  • Construction must constantly be supervised to maintain a high level of quality. In small communities, the cleaning service should make the daily supervision but should have the advisory of a knowledgeable professional with experience to oversee the progress of the work from time to time.

  • The landfill may become an open dump if municipal administrators are reluctant to invest in operation and maintenance.

  • Contamination of nearby surface and groundwater may occur if proper precautions are not taken.

  • The most significant settlement occurs in the first two years after the landfill is completed, making the use of the land difficult. Settlement time will depend upon the depth of the landfill, type of solid wastes, degree of compaction, and the amount of rainfall in the area.

2.6 Leachate

The degradation or natural putrefaction of wastes produces a black, foul-smelling liquid known as leachate which is similar to domestic wastewater, but much more concentrated. In addition, rainwater passing through the layers of refuse increases leachate in a proportion much larger than the waste moisture itself. Therefore, intercepting and diverting runoff before the beginning of the operation is important. If leachate increases too much it can cause problems not only in the operation of the landfill but will also contaminate nearby water streams, springs, and wells.

If we consider that in small communities the average area to be filled with solid wastes is not very large (see Annex I), the amount of leachate will also be small. We can then opt for its infiltration into the soil because along time, the leachate contaminant load diminishes once the landfill is completed and the soil acts as a natural filter (ref. 23). To protect surface and ground waters, however, the following measures should be taken: 

  • Confirm that nearby ground and surface waters are not being used for human or animal consumption.

  • Establish a minimum height of 1,0 to 2,0 m (depending on the soil characteristics) between the lower part of the landfill and the water table.

  • Use clay soil, 0,30 to 0,60 m thick, or a layer of impervious material at the bottom of the landfill.

  • Intercept, channel, and divert surface runoff and small streams to reduce leachate volume and keep landfill operation in good condition.

  • Construct a drainage system to collect leachate and facilitate its treatment if necessary.

  • The parts of the landfill that have been completed should be covered with a top soil layer of 0,40 to 0,60 m and then grass should be planted to decrease rainwater infiltration.

2.7 Gases

A sanitary landfill is, indeed, an anaerobic digester that produces liquids, gases and other compounds due to the natural degradation or putrefaction of organic wastes. Degradation by microorganisms occurs in two stages: aerobic and anaerobic.

The aerobic stage occurs when the oxygen present in the interstices of the mass of buried wastes is rapidly consumed.

The anaerobic stage predominates in sanitary landfills and produces appreciable amounts of methane (CH4) and carbon dioxide (CO2), as well as traces of stinking gases such as hydrogen sulfide (H2S), ammonia (NH3), and mercaptans.

Methane gas is important, though odorless, it is flammable and explosive if the proportion of its concentration in the air ranges between 5% to 15%. Gases tend to accumulate in empty spaces within the landfill and escape through any fissure in the soil or cover material. High concentrations of methane may build up causing explosions in the surrounding areas. It is therefore necessary to adequately control the generation and migration of these gases.

Gases can be controlled by constructing a vertical system of gravel vents placed at different points of the sanitary landfill so that gases can be released into the atmosphere. Since methane is combustible, it can be burned simply by setting it afire at the exit of the vent once the sanitary landfill is closed. This gas can be used as energy for a small stove to heat food or to light the landfill. It should be noted that the recovery and use of methane gas for commercial purposes is only recommended for sanitary landfills that receive more than 200 tons of refuse per day (ref. 7) and when local conditions are favorable. 

2.8 Cover material

One of the major differences between a sanitary landfill and an open dump is the use of cover material to separate the wastes from the external environment at the end of every working day.

Daily covering is of vital importance to the success of the sanitary landfill since it performs the following functions: 

  • Avoids the proliferation of flies, rodents and buzzards.

  • Prevents fires and smoke.

  • Minimizes bad odors.

  • Decreases the amount of rainwater entering into the refuse.

  • Conveys gases toward vents to evacuate them from thesanitary landfill.

  • Improves the aesthetic of the sanitary landfill.

  • Serves as a base for internal access roads.

  • Creates conditions for vegetation growth.

3. Manual sanitary landfill 

The manual sanitary landfills is a viable technical and economic alternative for urban and rural communities with less than 40,000 inhabitants and for urban marginal areas that generate less than 20 tons of refuse daily.

If the cost of transportation is low, a single manual sanitary landfill can be used for two or more communities.

When the manual operation technique is used, heavy equipment is required only to adapt the site, build internal roads, and to excavate trenches or cover material, in accordance with the landfill's method and advance.

Since all the remaining operations can be carried out manually, low-income communities unable to acquire and maintain heavy equipment can dispose of their refuse adequately using labor force easily available in developing countries.

Manual sanitary landfills can be used for up to 20 tons of refuse per day. A thorough analysis of the local conditions of each region is required to determine the most appropriate method to use. Depending upon the cost of labor, type of landfill, climatic conditions, etc., it may be better to use heavy equipment in the sanitary landfill in a partial or permanent way.

Based on previous experience, it is preferable to use such equipment when 40 or more tons of solid waste are produced per day.

A collection system using an agricultural tractor with a trailer (hydraulic tipping) and an agricultural tractor with a compactor trailer is being tested and evaluated in Antioquia (Colombia) to provide urban cleaning services in small communities.

This system offers collection and transportation services and supports the final disposal of refuse.

The agricultural tractor can work as an independent unit and accessories such as bulldozer blades, front loaders, backhoes, and rollers to compact solid wastes can be adapted to operate sanitary landfills. This increases the performance of the landfill because larger amounts of refuse can be disposed of daily. This more versatile device brings technical and economic benefits to the entire system of urban cleaning. In special cases, the tractor can also be used for other public works, taking advantage of the investment already made by the municipality. Figure 3.1.

Collection and transportation
of solid wastes.

Movement of soil and solid wastes
in a sanitary landfill.

FIGURE 3.1
Use of an agricultural tractor in cleaning services 

In Mexico, after 18 months of experiments with prototype tractors, the Secretariat of Urban Development and Ecology concluded that an adapted 31 HP tractor can confine the waste of communities up to 80,000 population, i.e., approximately 40 tons of refuse per day, in eight hours of work with one day laborer. Ref. 25. 

3.1 Planning

Although it is a small work, a manual sanitary landfill is an engineering project in which most potential problems are prevented through careful planning in the initial stages. It is simpler and more economical to plan well than to make corrections once it is in operation.

The initial planning lays the groundwork for site selection, design, construction, operation and maintenance. Basic information that should be examined includes the population served, the origin, quality, and amount of solid waste to be disposed of, possible available sites, future use of the land once the landfill is completed, resources for its financing, and the advisory of a competent professional.

It is important to have the advisory of a sanitary engineer with experience in landfill design, construction, and operation at the initial stage of a project.

Support of the public is needed, otherwise, it is quite probable that the project will not be successful. The initial planning should include a public information program that explains the pros and cons of establishing the landfill to the community. Every community should realize that a manual sanitary landfill, as any public work, requires resources for its financing, design, construction, operation, and maintenance. 

3.2 Selection fo the site

Appropriate selection of the site for a sanitary landfill will eliminate many operational problems in the future. In selecting a site, places where the operation of the sanitary landfill will improve the land should be considered first.

3.2.1 Community participation

3.2.1.1 Local authorities

Local planners, health, and water protection authorities should be consulted when choosing a site. Figure 3.2. 

  

FIGURE 3.2
Presentation of the project to local authorities

Only on few occasions will a site meet the ideal conditions for building a sanitary landfill. The pros and cons should be analyzed according to the technical and financial resources available. The following steps are recommended:

  • First, a sanitation technician and a member of the local administration (chief of planning, public works, etc.) responsible for the cleaning services will determine what areas are adequate and available as sites. Whenever possible several alternatives should be noted.

  • Second, the sanitary engineer from the regional or central office should make the preliminary site selection, (establishing an order of preference), perform necessary calculations, and make rapid designs of the final configuration of the land. Whenever possible, costs and useful life should be determined.

  • Third, the final decision will be subject to administrative and policy considerations, bearing in mind public opinion. The project should then be presented to the municipal council for approval. If the land does not belong to the government, the municipality should approve negotiations and authorize the mayor to make budgetary transfers to acquire and construct the sanitary landfill and related works (Appendix IV).

  • Fourth, make calculations, complete final designs of the sanitary landfill, evaluate costs, seek financing, and proceed with its execution.

3.2.1.2 Public opinion

Public relations are frequently neglected by municipal authorities and technicians during site selection. From the beginning of the selection process, the public should have an opportunity to participate in, comment on, and question the proposals made. It is essential to ensure that all sectors of the community give their support during all phases of the selection, design, construction, operation, maintenance, and future use of the sanitary landfill.

In many communities people believe that a sanitary landfill is an open dump. Because of this confusion, it is recommended that an educational and informational campaign be conducted in schools, associations, cultural centers, clubs, and through the local media. 

3.2.2 Technical aspects

The sanitary engineer should consider the following aspects: 

Location. The location of the site plays an important role in the system operation. The distance and even more the time it takes to reach the urban center affect the cost of solid waste transportation. It is recommended, thus, that the landfill be nearby (i.e. not more than 30 minutes for a round trip). This will reduce transportation costs and will allow the community to supervise that the landfill is being operated and maintained in the best possible way (figure 3.3).

Texto de la figura 3.3.
Site selection
Key to success

  

FIGURE 3.3
Location of a sanitary landfill near an urban area 

  • It should be noted that there are no fixed rules. It will mostly depend on land availability, topography, useful lifespan of the landfill, and number of nearby facilities. It is recommended to establish the landfill boundaries at 200 meters away from the nearest households.

  • Access roads. The land should have access to a main road so that solid wastes can be transported easily. Internal roads in the landfill should allow collection vehicles safe and rapid access to the working face all the year under different weather conditions (figure 3.4).

FIGURE 3.4
Access roads

  • Hydrogeological conditions. If the are water springs it would be necessary to drain them by lowering its level; it is also necessary to evaluate the water table depth and maintain at least 1 to 2 m between groundwater and solid wastes. The permeability and absorption capacity of the soil must also be evaluated.

  • Useful lifespan. The site capacity should be large enough for its long-term use (more than five years) and consistent with the management, preparation costs, and infrastructure. Obviously, it all depends on land availability.

  • Cover material. The land should have abundant cover material, be easy to extract, and if possible, have a good proportion of clay due to its low permeability and high capacity to absorb contaminants. When it is not available at the site, transportation cost should be considered to obtain it from a nearby site. If it were not possible, it is better to reject the site before beginning any work since this may become an open dump. Figure 3.5.

FIGURE 3.5
Availability of cover material

  • Conservation of natural resources. A sanitary landfill should not be located near a water source. Ideally, it should be located in an isolated area of low commercial value where it will not contaminate surface or ground waters. In other words, it should protect both natural resources, and animal and plant life.

  • Climate conditions. Wind direction is important because it may cause nuisances do to blow dust and paper and the spread of bad odors to nearby areas. Therefore, the sanitary landfill should be located in such a way that wind blows from the urban area towards it (figure 3.6). If this is not possible, planting trees and thick vegetation along the entire landfill is another measure to counteract this problem.

  • Costs. Before making calculations and designs for a sanitary landfill, it is necessary to know the cost of the land and if it is available. An estimate should be made of the investment required for its preparation and infrastructure. Costs are sometimes so high that the municipality can not afford it, hence, other sites should be considered.

FIGURE 3.6
Wind direction 

  • Land ownership. A sanitary landfill project should began only when the entity responsible for the landfill (usually the municipality) has a legal document (municipal agreement) acknowledging ownership of the land and authorizing its construction. The document should also specify future use, since the site may be later used as a recreational or reforestation area.

  • Master plan. When evaluating the landfill site, it is important to consult with the local urban planning office about the master plan to delimit the urban perimeter and define the present and future land uses. It is recommended to orient the urbanization growth toward the site but not immediately, since once the sanitary landfill useful life is over the land can be used to benefit the community. Figure 3.7.

FIGURE 3.7
Compatibility with land uses

  • Future use. Every sanitary landfill project should consider its future integration into the natural environment. Once its useful lifespan is over, a manual sanitary landfill can be transformed into a park, sports area, garden, nursery, or small forest. Figure 3.8.

SITE SELECTION IS EQUALLY OR MORE IMPORTANT FOR SMALL COMMUNITIES!

 FIGURE 3.8
Future use of the site

3.2.3 Methodology for site selection

3.2.3.1 Preliminary analysis

Field visits will be carried out with local authorities and those responsible for water and environmental protection. Topographic plans of the region on a scale of 1:10,000-1:25,000 should be available to locate possible access roads and exits from the urban area, the nearest streams, and the distribution of typical soils.

Back to the local planning office, land use and restrictions, as well as the future expansion of the urban area should be discussed to analyze whether or not the landfill is compatible to those sites.

3.2.3.2  Field research

For the sites selected, additional details should be analyzed such as the likelihood of groundwater contamination, soil and water table characteristics, and the identification of reference points, topographic irregularities, water springs, roads, and buildings.

With an urban map on a scale of 1:2,000-1:5,000, the advantages and disadvantages of each site, preliminary useful lifespan, and cost calculation can be evaluated. This information will be submitted to local authorities for the final decision. 

3.3 Steps in design, construction and operation

 

        FIGURE 3.9
        Field studies and design

3.3.2 Land preparation and construction of works

 

FIGURE 3.10
Land preparation and construction of civil works

3.3.3 Operation and maintenance

FIGURE 3.11
Operation and Maintenance

3.4 Timetable of activities

The following timetable may be useful for programming the execution of activities of a manual sanitary landfill.

TABLE 3.1
Manual Sanitary Landfill - Timetable of activities 

ACTIVITIES

1ST
month

2ND
month

3RD
month

4TH
month

5TH
month

6TH
month

  • Identification of the landfill and surroundings

- Site selection

- Topographic survey

- Studies and design

  • Peripheral infrastructure

- Access roads

- Rain drainage

- Deviation and eventual isolation of water streams

  • Landfill infrastructure

- Cleaning and clearance

- Sections

- Preparation of the supporting base

- Drainage of percolated liquid

- Gas drainage

- Internal access

- Internal rain drainage

  • Auxiliary constructions

- Peripheral fence

- Tree planting

- Porter’s booth

- Signal

- Booth

- Sanitary facilities

- Monitoring well

  • Dump(s) closure

- Eradication of rodents and arthropods

- Land cover and compaction

- Fencing

- Notices

  • Beginning of landfill operation

3.5 Basic project

3.5.1 Topography survey

Once the site has been defined and the municipality has acquired the land, a detailed topographic survey should be completed to make the calculations and prepare the final design of the sanitary landfill. Its scale should be of 1:250-1:500, with contour intervals at every meter and marked every 5 meters.

The topographic survey of the land and preparation of plans (drawings and sections) can be contracted out by the municipality. The Ministry or Secretariat of Public Works, Health, or Community Development may also be able to provide this service.

However, if such facilities are not available and the community lack topographic equipment to determine the area and capacity of the land, the topographic survey may be carried out with a measuring tape and hand level, or even a hose, since this small work does not require much precision. 

3.5.2 Design of the sanitary landfill

The design embodies the conception of the landfill and planning of the construction. It is presented to the local authorities and the community for its promotion and financial analysis.

Whenever possible, the basic design should include the total space and land area to be filled, the construction method, the source of cover soil, and the layout of infrastructure works.

The report should also include the lifespan of the landfill, its future use and estimated cost of the project.

3.5.3 Details of the project

The design should be presented in maps with drawings and profiles of the project containing at least:

  • delimitation of total area;

  • land configuration;

  • initial site preparation;

  • details of access works, main drains, and auxiliarystructures;

  • partial configuration of landfill; and final configuration of the landfill with landscape improvement.

Basic information studies, estimations, and design of the manual sanitary landfill are presented in Chapter 5. The following chapter deals with landfill site preparation and infrastructure required for receiving solid wastes, as well as its construction, operation, and maintenance.

4. Site preparation and construction

  4.1 Preparation of the site

This stage includes engineering projects, landscaping, and construction details. They should fulfill sanitary requirements and be performed with simplicity and speed.

4.1.1 Construction of the perimeter 

4.1.1.1 Access roads

The sanitary landfill should have access to a main public road that meets design standards whether or not it is paved. Figure 4.1.

It should be noted that the time it takes to transport refuse to and from the landfill site is more important than the actual distance.  

 

FIGURE 4.1
Access roads to the sanitary landfill

 4.1.1.2 Rainwater drainage

It is important to study the amount of rainfall to foresee drainage characteristics and the works required to lessen the production of leachate. By doing this, water contamination will be prevented and it will be possible to select the areas of operation and facilities for workers.

Rain falling nearby the sanitary landfill often drains into it, causing serious operational problems. Intercepting and diverting this runoff outside the sanitary landfill helps reduce the volume of leachate and improves the operation. A soil or soil-cement trapezoidal channel must then be constructed according to local precipitation pattern, the tributary area, soil, vegetation, and topographic characteristics. Figure 4.2.

Texto de la figura 4.2:
Área a rellenar: Area to be filled
Canal perimetral en tierra o suelo cemento: Perimetric channel made of soil or soil-cement
Cerca y arborización perimetral: Fence and tree planting
Vía principal: Main road 

FIGURE 4.2
Rainwater drainage in the perimeter 

For a small basin, a channel with the dimensions shown in Figure 4.3 is recommended. However if greater precision is required and the engineer recommends it, the inflow can be calculated through the rational method and the dimensions of the channel.

Qp =  K i Ad
          3.6 x 106

where:

Qp = inflow or maximum runoff [m3/sec]
K = runoff coefficient
i = rain intensity for a duration equal to tc [mm/hour]
Ad = basin area [m2]
tc = concentration time [min]

FIGURE 4.3
Cross sectional detail of the trapezoidal channel

The channel should be plotted along the maximum level curve of the landfill, and should guarantee an average maximum speed (0.5 m/sec) that does not cause excessive erosion. The size of the channel section can be calculated using the following equation:

A = Qp
         v

where:

A = area of the ditch section [m2]
v = maximum average speed [m/sec]

Once the area of the section is determined, the dimensions are decided based on the previous recommendations.

4.1.2 Infrastructure of the landfill

Site preparation is important to improve its conditions, to facilitate the reception of solid wastes, to build the cells, and for the general operation of the sanitary landfill. The following activities should therefore be carried out:

4.1.2.1 Cleaning and clearance

A supporting base for the landfill should be prepared in the site. It is usually necessary to fell trees and shrubs because they could be an obstacle to the operation. This cleaning should be done in stages, in accordance with the progress of the operation to avoid soil erosion. Figure 4.4.

 FIGURE 4.4
Land cleaning and clearance

4.1.2.2 Solid base preparation

Before beginning the landfill, it should be decided whether to remove the bottom layers of soil. This will depend on the availability of cover material. In some cases, it may be advantageous to leave the land intact to use its absorption and filtration capacity to remove leachate contaminants.

To level the soil and slope sections, it is advisable to move the earth in stages so that the rain will not cause soil erosion and the earth can be used as cover material. On the other hand, topsoil should be stored and preserved to be used as final cover to support vegetation as some areas of the landfill are completed.

To level the soil and to excavate ditches, heavy equipment (a caterpillar tractor and/or backhoe) should be used because manual excavation is too inefficient. Similar equipment should be used for building internal roads or extracting and storing cover material (the latter is recommended only in dry periods). Figure 4.5.

Texto de la figura 4.5
Adecuación del suelo de soporte: Adequacy of supporting soil
Excavación de zanjas: Ditch excavation

      FIGURE 4.5
      Earth movement for preparing the site

A municipality may request heavy equipment as a loan or lease from a regional or national public works agency, a regional corporation, or even a nearby municipality. The municipality may defray the fuel costs and the wages and food of the operator. In general, earth movement will not take more than a week because the preparation for the manual sanitary landfill should be conducted in stages.

One of the greatest difficulties that small communities have to face, apart from acquiring the land for the sanitary landfill, is the loan or lease of heavy equipment to carry out the initial earth movement. This task challenges the managerial ability of the responsible staff member.

4.1.2.3 Lands with high water table

When only marshy or swampy lands are available, they can be used to construct a manual sanitary landfill by lowering the water table permanently through the following procedures:

  • Dig one or several drainage ditches, according to the depth required, in the lower part of the lot until the first layers of refuse are at least 0.60 m to 1.00 m above the highest level of the water.

  • Install a perforated concrete pipe and fill the ditch with stone, as filter media, along its length.

  • Cover the stone drainage with a geotextile or similar material to prevent clogging.

  • Place a 0.60 m to 1.00 m layer of clayey material on the geotextile to isolate the upper surface of the drain from the solid wastes. This will avoid possible water contamination. Figure 4.6.

  • Care should be taken not to cross the leachate fluid drainage with the drainage ditch to abate the water level.

Texto de la figura 4.6
Superficie del terreno: Land surface
Nivel freático: Water table
Dren secundario: Secondary drainage
Dren principal: Main drainage

      FIGURE 4.6
      Drainage for lands with high water table

4.1.2.3 Sections

Slopes are constructed to avoid erosion ant to provide landfill stability. Depending on the type of soil, slopes may range from vertical to 3:1 (H:V) and sections may range from one to three meters. Platforms should have a gradient of 2% toward the interior slopes to drain leachates and to prevent ponding when used as temporary access roads. This also provides a greater stability to the area. Figure 4.7.

Constructing a manual sanitary landfill over a small water stream or spring without first lowering its level, channeling it, and encasing it should be avoided to prevent direct contact with leachate.

4.1.2.4 Leachate drainage

Managing leachate is one of the greatest problems in a sanitary landfill. In many cases, despite the perimeter channels which intercept and divert runoff, the volume of leachate increases significantly by rain falling directly on the landfill surface (see operation in rainy seasons).

Texto de la figura 4.7
Método del área: Area method
Futuro corte para vía interna: Future section for internal road
Superficie original del terreno: Original surface land
Corte: Section
Pendiente del talud del terreno: Slope
Cuneta: Ditch
Pend 2%: 2% slope
Vía temporal interna: Temporary internal road
Drenaje de percolado: Leachate drainage
Método de trinchera: Trench method
Corte: Section
Superficie original del terreno: Original surface land
Talud de la trinchera: Trench slope 

 FIGURE 4.7
Sections of slopes and landfill base

It is essential, therefore, to build a drainage system for the sanitary landfill before wastes are discharged. Whenever possible, this system should keep the leachate inside the landfill to allow more time for infiltration and reduce its appearance on the surface. This is to avoid leachate treatment as much as possible, which is complex and expensive for small localities.

To increase efficiency, it is recommended to build these drains at the base of the interior and exterior slopes of the landfill platforms or terraces to prevent runoff over the surface of the lower slopes and to connect them with vertical gas vents.

  • Construction of the drainage system

The drainage system consists of a horizontal network of gravel ditches that interrupts the continuous flow of leachate through screens made of mud and wood or even features of the land.

Drains can be constructed as follows:

  • A sketch, similar to that of a sewerage system fish spine, has to be prepared showing where the drains will be located. Figure 4.8.

  • Ditches are dug and screens are built every 5 to 10 m, with 0.20 to 0.30 m width or small land spaces are left intact in the ditch. They will have a 2% gradient at the bottom and a free border of about 0.30 between the screen and the surface level to allow leachate drainage without overflowing the ditches.

  • Ditches are filled with stones of 4 to 6 inches to offer more free space to prevent clogging. Once the ditches are filled with stone, a material should be placed to filter liquids and retain fine clogging particles. Dry branches, hay, and even grass, can be used to replace the geotextile. Figure 4.9.

Texto de la figura 4.8
Canal perimetral de aguas lluvias: Rainwater peripheral ditch
Talud: Slope
Drenaje de percolado: Leachate drainage
2do. nivel o terraza: 2nd platform or terrace
1er. nivel: 1st platform or terrace
Percolado a campo de infiltración: Leachate infiltration field

Gra27.gif (172700 bytes)

Another way to build this drainage at the base of the site is to use discarded automobile tires. This takes advantage of a material that is difficult to manage in the landfill and creates a greater storage capacity for leachate. After tires have been buried vertically –one against the other- a layer of 0.20-0.30 m of stone and dry branches (as in the previous example) is placed. It should be noted that the ditch should have a special shape for the tires. Figure 4.9.

Texto de la figura 4.9
Pantalla: Screen
Borde libre 0.20-0.30: 0.20-0.30 free border
Llantas de desecho: Discarded tires
Zanja: Ditch
Piedra: Stone
Borde libre: Free border
Pantalla: Screen
Piedra: Stone

FIGURE 4.9
Details of leachate drainage

During heavy rainfalls and when the amount of leachate exceeds the drainage capacity of the landfill, the drainage system should be extended by creating an infiltration field outside the landfill to store this fluid at least during rainy days. Figure 4.10.

Texto de la figura 4.10
Viene del relleno: From the landfill
Futura extensión: Future extension
Tierra: Soil
Plástico: Plastic
Piedra: Stone
Detalle de zanja: Ditch detail
A lagunas de estabilización o filtro percolado: To stabilization pond or percolating filter
Curvas de nivel: Contour line
Tubería perforada: Perforated tube

 FIGURE 4.10
Filtration systems in ditches or trenches

In this drainage area outside the landfill, alternating sections without stones can be left between screens. This is done for several reasons:

  • To estimate the volume of leachate coming from the landfill.

  • To check the amount of solid material that has settled. This determines when the landfill's exterior drainage needs to be cleaned.

However, there are regions with heavy rains (more than 3,000 mm/year) that create large amounts of leachate, which are difficult to handle. In such cases, according to calculations, the volume of leachate may be such that even the land available for leachate drainage, storage and infiltration may be insufficient or its construction may not be economically feasible.

In these cases, to manage and control the leachate production it is recommended: 

  • To build an oversized drainage system.

  • To build the landfill with narrow working faces, i.e., it is preferable to have overlapping cells supported on the slope or on completed cells. In other words, the landfill grows vertically rather than horizontally.

  • To cover daily the cells and temporarily completed areas with plastic to avoid rainwater filtration through wastes. This practice reduces the amount of leachate significantly. It is useful to remember that the amount of plastic required is rather small, depending on the extension of the landfill and the working method.

  • To use plastic covers discarded from large greenhouses.

  • To apply the final cover and immediately plant grass on the completed areas of the landfill.

Depending on the type of wastes and the field capacity, in regions where the annual precipitation does not exceed 300 mm and there is a channel for intercepting and diverting rainwater, no significant problems with leachate would appear. However, it is recommended to build drains in the bottom of the landfill and in the platforms or terraces. The size of the ditches will be smaller, though.

  • Treatment

When the soil does not permit filtration or when the aquifer is being used as a water supply source, leachate will have must be treated.

Due to the high concentration of solid materials in leachate, treatment solely by chemical processes is too expensive. Since leachate from municipal solid wastes is similar to domestic wastewater (with a high proportion of biodegradable organic matter difficult to settle), treatability studies should be done to select the adequate biological treatments to improve leachate quality whenever possible.4 Among those processes that can be used to treat leachate are trickling filters and stabilization ponds. 

4.1.2.6 Gas venting

Gas venting consists of a ventilation system in stone or perforated concrete pipe (lined with stone) which operates like a chimney or vent and passes through the entire landfill vertically from the bottom to the surface (figure 4.11). These vents are constructed vertically as landfill advances and a good compaction around it should be provided. The installation of vents every 20 or 50 m with a diameter of 0.30 and 0.50 m each, is recommended.

The method for constructing gas vents or chimneys is illustrated in Figure 4.11.

Texto de la figura a)
Construcción de filtros de gases: Construction of gas filter
Base compacta: Compacted base
Malla de gallinero: Chicken wire
Alambre de púas: Barbed wire
Piedras: Stones
Estacas de madera: Wooden stakes

 

Gra30.gif (24151 bytes)

a. Vent construction using wooden stakes,
barbed wire, or chicken wire and stones

Texto de la figura b)
Ventila de gases: Gas vent
Celda diaria: Daily cell
Tubo metálico o plástico: Plastic or metal tube
Drenaje de percolado: Leachate drainage
Piedras: Stone
Superficie de celda: Surface of the cell
Extracción del tubo: Tube extraction

b. Vent construction using a plastic or metal tube and stones.
The tube is extracted as the landfill grows.

FIGURE 4.11
Gas venting construction

Drains should be interconnected to increase the efficiency of fluid and gas drainage in the sanitary landfill. Figure 4.12. 

 FIGURE 4.12
Interconnection of drainage systems (section of platforms)

Once the last cell is almost completed, two connected pipes must be placed. The first one should be perforated to facilitate gas capture and release; to avoid the obstruction by solid wastes or cover soil it must be filled with stones like a protective "sleeve". The second pipe should not be perforated so as to collect gas and burn it, eliminating odors produced by other gases. Figures 4.13 and 4.14.

Texto de la figura 4.13
Bien compactado: Well compacted
Tubería de concreto 04"A6" rodeado de plástico como sello: 04"A6"concrete tube lines with plastic as a seal
Grama: Grass
Cobertura final: final cover
Desechos sólidos: Solid wates
Cobertura diaria: Daily cover
Drenaje de piedras: Stone drainage
Tubo perforado: Perforated tube
Celda: Cell
Suelo de soporte: Supportive soil
Pantalla: Screen

FIGURE 4.13
Construction detail of the gas venting filter

Texto de la figura 4.14
Canal de tierra: Channel in the soil
Canal interno: Internal channel
Drenaje en piedra: Stone drainage 

  

FIGURE 4.14
Vent distribution in the landfill

4.1.2.7 Internal accesses and rain drainage

When planning a sanitary landfill, internal access roads within the site should be examined carefully since the continuos use of these roads may cause serious problems during the rainfall season.

A small road of 6 m width with drains should be built and kept in good conditions to unload wastes to the working face throughout the year. The maximum gradient can be between 7 to 10%, depending on the condition of the vehicle and whether they are going upward loaded or empty.

Although the access roads to the working face a manual sanitary landfill can be made of soil, stone and debris, such roads should be well maintained and drained. 

4.1.3 Auxiliary structures

The proposed auxiliary structures are small and low-cost, although they must be compatible with the useful lifespan of the landfill and should meet sanitary requirements and intensive labor use in all its activities, while minimizing temporary investments. 

4.1.3.1 Perimeter fence

A four-strand barbed wire fence with an entry gate should be built for safety. This will also stop livestock from entering the landfill, since it does not only hinder the operation but destroys cells, especially when workers leave at the end of the working day. Figure 4.15. 

FIGURE 4.15
Perimeter fence

A live fence of trees and shrubs should be constructed to hide solid waste from neighbors and passersby, as an esthetic measure. It will also stops pieces of paper and plastic blown by the wind. Planting of fast-growing trees (pine, eucalyptus, laurel, bamboo, etc.) is recommended. Figure 4.16. 

FIGURE 4.16
Planting trees along the periphery

 4.1.3.2 Booth

The construction of a booth (10-15 m2) is important to be used as a porter's lodge, a place to keep tools, for workers washing and changing (before and after work), a toilet facility, a kitchen for heating food on a burner, and as a shelter in case of heavy rain. A prefabricated booth can also be adapted and used for these purposes. The municipal administration can request it as a donation and give the company publicity in return. Figure 4.17. 

Gra37.gif (17334 bytes)

FIGURE 4.17
Booth and sanitary facilities

4.1.3.3 Sanitary facilities

The landfill should have minimal sanitary facilities to ensure workers comfort and well-being. Water should be carried to the landfill for sanitary services and at the very least a latrine or cesspool must be built (Figure 4.17). During dry periods water should be sprinkled on the landfill surface with a hose to obtain better compaction and to prevent dust.

Information and advisory services about how to construct sanitary facilities can be obtained in the environmental sanitation offices of the municipality's health unit. 

4.1.3.4 Maneuvering area

An area of approximately 200 m2 (10 x 20) should be prepared so that collection vehicles can maneuver and discharge refuse at the working face without problems. 

4.1.3.5 Signs

A sign announcing the landfill must be placed to make it known by the community. The sign can be made of two sheets of tin and a wood frame. It will be painted first with anticorrosive, and then with a paint of the desired color; a brief description of the project and a civic legend must be written. A commercial company may also prepare this sign. Figure 4.18. 

  

FIGURE 4.18
Sign announcing the landfill

An official name for the sanitary landfill should be chosen at the beginning of the project. This name should then be used in all documents and relevant correspondence.

4.1.3 Landscaping

In order to integrate the sanitary landfill into the natural environment, not only the landfill's final surface but also the entrance and contour of the area should be landscaped.

For vegetation, the final compacted cover with a 0.40 to 0.60 meters as minimum, gas venting, and runoff drainage are needed. However, few species are recommended until the landfill stabilizes. Grasses and short-rooted plants, which do not exceed the cover, should be used on the whole area of the landfill. Pits filled with fertilized soil can also be used for planting.

To prevent erosion and leachate increase, it is important to plant grass while parts of the landfill are being completed rather than waiting until the operation is finished. This task is simpler if topsoil is stored when initial earth moving is done. 

 4.2 Construction

Construction begins immediately after designing the sanitary landfill. The best design will mean nothing if the administration does not have political will to execute it properly. The construction of a sanitary landfill is of great importance compared to other public work projects because of the time it requires for its execution and the continuous maintenance it demands.

To plan the progress of the operation, it is necessary to have topographic maps of the project with longitudinal profiles and cross sections profiles indicating the partial configuration of the areas filled at every stage. The advancement of the operation and of the working face is tracked by calculating the volumes and heights occupied according to the contour lines and elevations. 

4.2.1 Construction method

The trenching or area construction method depends on topographic conditions, soil characteristics and water table. These factors will determine whether or not the cover soil can be extracted from the landfill; extraction from the landfill itself is the most economic alternative. 

4.2.2 Cell construction

The daily cell is defined as the basic construction unit of a sanitary landfill. It is similar to a small block and is formed by the wastes buried in one day and the soil required to cover them. 

4.2.2.1 Cell size

The size of the daily cell varies in each case and is theoretically defined as a parallelepiped. Its width is the working face required by collection vehicles (usually no more than two) to unload wastes. The length is determined by the amount of wastes that arrives at the landfill in a day and the height is limited to one meter or a meter and a half to facilitate compaction. Figure 4.19. 

Texto de la figura 4.19
Altura: Height
Ancho: Width
Avance: Length
Material de cobertura: Cover material
Desechos sólidos: Solid wastes

FIGURE 4.19
Typical daily cell

4.2.2.2 Construction

Wastes should be unloaded at the working face. The workers spread them over the slope of the cells already completed in successive layers of 0.20 to 0.30 m, using pitchforks (a three-pronged fork) or rakes (eight or ten prongs). The upper surface is leveled and compacted with a roller, while the lateral surfaces are compacted using manual tampers.

The spreading and compaction is done in horizontal or inclined layers with a 1:3 gradient (height: length). This provides more compaction, better surface drainage, less cover soil, better containment and landfill stability.

At the beginning of the construction, the landfill should always be contained by supporting every cell against the natural land slope or trench walls and, as the landfill increases in height, on the completed cells.

 4.2.2.3 Cover

To complete the cell, it is covered with a layer of soil of 0.10 to 0.15 m. The layer is spread with a wheelbarrow, shovels and large hoes, and compacted with a roller and hand tampers. It is important to remember that the daily cover prevents the presence of insects, rodents, and buzzards, as well as fire, smoke, bad odors, moisture, and scattered garbage.

Cover should be applied at least once per every collection day. At the end of the working day, no solid wastes should be exposed to the air, much less on weekends.

There is no need to be demanding about the quality of a cover material for a manual sanitary landfill. It is recommended to use the available soil, since the basic objective is to cover wastes.

With regard to the amount of cover material required, 1 m3 of soil should be used for every 4 to 5 m3 of compacted solid waste, i.e., between 20% and 25%.

For the final cover, it is recommended to place two layers of 0.40 to 0.60 m each in two phases with an interval of approximately a month between layers to cover the settlements produced in the first layer. 

  • Area method

If cover soil is dug at the site itself, the transportation cost for soil cover is minimal. It is recommended to extract it from the land slopes forming platforms to prevent erosion. It is advisable to expand the site's capacity and useful lifespan or take advantage of soil excavations for new buildings in the urban area. This can be done by publicizing that soil cover is needed at the landfill or through direct contact with builders who may assume the transportation cost.

In dry periods, extracting and accumulating the cover soil with a tractor or backhoe will generate better yields. The soil can be stored upon the finished cell and then be used for completing the other cell.

In rainy periods, the opposite will happen, since the accumulated material is dragged and is heavier because of moisture; hence, it will be more difficult to transport. Under these circumstances, it is necessary to extract the amount of soil needed to cover the cell on a daily basis.

  • Trench method

When the trench method is used, cover material is readily available. It is recommended to accumulate it near the ditch being excavated or on the top of a completed cell. 

4.2.2.4 Compaction

Since the purpose of this basic sanitation operation is to use technology available at the region and to promote extensive labor force, cell formation and compaction will be made with masonry tools. Densities achieved in the manual sanitary landfill will therefore be relatively low (400-500 kg/m3) but sufficient for the proposed objectives. However, the following factors may affect solid waste compaction.

  • Transit of vehicles over completed cells; this practice should be promoted in dry periods.

  • Decomposition of solid wastes. In developing countries organic matter accounts for a high proportion of its physical composition (between 40% and 70%) and is transformed into humus, water, and gases.

  • The weight of the upper cells on the lower ones produces a load that increases the amount of compaction.

  • Storage of cover material on the already completed cells.

"The complexity of every project depends on the circumstances, size, resources, and uses of the future sanitary landfill"

4.2.3 Landfill construction plan

Construction of the sanitary landfill should be guided and controlled, according to its design and future use. It is recommended to build the manual sanitary landfill in platforms of three meters high, which in turn will be formed by three one-meter cells. Each platform will correspond to a phase of the landfill's construction. Between each platform, a berm of about three to six meters wide should be left to give major stability to the operation.

When the trench and area methods are combined to take better advantage of the land, each construction phase will correspond to an operation method.

Figures 4.20 to 4.24 illustrate the operation plan for a sanitary landfill, depending on the method. 

Texto de la fig. 4.20
Ancho: Width
Separación entre zanjas: Separation between ditches
Avance del relleno: Completing the landfill
Vía interna de circulación: Internal road.

FIGURE 4.20
Land management plan for building
a manual sanitary landfill using the trench method

Texto de la fig. 4.21
Ventila de gases: Gas vent
Rampa de acceso: Access ramp
Talud: Slope
Caseta: Booth 

 FIGURE 4.21
Finished sanitary landfill combining the trench and area methods

 Texto de la fig. 4.22
Vía principal: Main road
Vía de acceso interno: Internal road
1er. nivel : 1st level
Planta: Plant
Curva de nivel cada 5 metros: Contour line every 5 meters
Perfil terreno original: Original soil profile
1er. nivel: 1st level
Perfil A-A: A-A profile

FIGURE 4.22
Operation plan for a deep quarry 13/

Texto de la fig. 4.23
No. de fajas y celdas: No. of lifts and cells
1ª. celda : 1st cell
1ª. faja: 1st lift
Avance: Completing the landfill
Vía: Road

 FIGURE 4.23
Formation of landfill levels in a quarry/

Texto de la fig. 4.24
Vía principal: Main road
Vía interna: Internal road
Área cerca de la entrada reservada para época de lluvia: Area near the gate reserved for the rainy season
Frente de trabajo: Working face
1ª faja: 1st lift
Avance del relleno: Completing the landfill
Etapa: Phases
Área de ingreso y adecuación de la entrada con material inerte: Preparing the entrance area and gate with inert material
Vía interna formada con desechos de demolición: Internal road built with debris
Primera faja- desechos cubiertos: First lift-Covered wastes
Secuencia de la formación de fajas: Sequence of lifts

Corte : Section
Una superficie plana puede ser fea e interrumpir el paisaje: A flat area may interrupt the landscape
Una superficie suave armoniza con el paisaje: A gentle slope creates a nice landscape

FIGURE 4.24
Operation plan for a flat area13/

5. Design of manual sanitary landfills

 Once the site has been selected, the technician should complete several field studies. First, a thorough recognition of the site has to be done with a topographical map, notes, graphics, or tables showing the quantities of solid wastes and soil accumulated. This will be used to evaluate land depressions and slopes. The future use of the sanitary landfill has to be considered.

The field visit is essential for creating a good design. Thus, plans can be adapted to the land by identifying the area to be filled and its surroundings, internal access routes, drainages, construction method, and the source of cover soil.

5.1 Basic information

5.1.1 Demographic  aspects

5.1.1.1 Population

The number of inhabitants to be served is required to define the quantity of solid waste that will be disposed of. A difference should be made between rural and urban production of solid wastes. Rural wastes present fewer requirements due to its low production, but its collection is more difficult. On the other hand, solid waste production in urban areas due to its concentration, population increase, and technological development is more complex and is the topic of these guidelines. 

5.1.1.2 Population Projection

During the design process, it is extremely important to estimate waste future production to define the quantity of solid wastes that will be disposed of. As with any public service, population projection should be estimated. Table 5.1 summarizes the basic information needed.

Population growth can be estimated using mathematical methods or a curve projection using census data.

Among the mathematical methods, geometric growth (i.e., biological population expansion at a constant rate) is presented as a guide. The following expression shows its calculation:

TABLE 5.1
Volume and Area Required

 

Year

Population (persons)

PCP

kg/persons-day

SOLID WASTE QUANTITY

SOLID WASTE VOLUME

AREA REQUIRED

Daily (kg)

Annual (ton)

Accumulated (ton)

Compacted

Stabilized annual (m3)

Landfills

Landfill ASL (m2)

Total AT (m2)

Daily (m3)

Annual (m3)

(SW + CM) annual

Accum. (m3)

 

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

1

                       

2

                       

3

                       

4

                       

5

                       

6

                       

7

                       

8

                       

9

                       

10

                       

11

                       

12

                       

13

                       

14

                       

15

                       

(6) The SW production in a week is disposed of in the SL in "x" collection days (7 days/x workdays).
(9) V sanitary landfill = solid waste + soil (20-25%)
(11) ASL = VSL/HSL (ASL = Area to be filled).
(12) AT = F ASL F (factor for additional area).

Area/persons ------------- current (m2/persons)

REFUSE DENSITY
- Loose - 200-300 kg/m3
- Compacted - 400-500 kg/m3
- Stabilized - 500-600 kg/m3

 

Fp = Po (l + r)n                                                                 [5-1]

where:

fP = Future population
Po = Current population
r = Growth rate
n = (tf – t0) = range in years

 However, it is recommended to compare the results obtained with other projection methods.

5.1.2 General aspects of solid wastes

Among the most important factors that should be considered for adequate handling of solid wastes are composition and quantity. 

5.1.2.1 Waste Composition

Solid wastes in urban areas can differ according to its source: residential, commercial, industrial, street sweeping and markets, and institutional.Table 5.2. 

a) Wastes from the Residential Sector

Domestic refuse consists mainly of paper, cardboard, tins, plastics, glasses, rags, and putrescent organic matter.

In studies carried out on refuse production in small localities (less than 40,000 persons) no larger differences were found among socioeconomic strata.

b) Wastes from the Commercial Sector

With some exceptions, businesses do not produce large amounts of solid waste. In small localities, they are not well developed and in general, commercial activity is combined with housing.

Wastes from the commercial sector are similar to domestic wastes but contain a higher quantity of packing material (paper, cardboard, glass, and plastics).

c) Wastes from the Industrial Sector

Industrial activities in small communities are usually low and labor-intensive, compatible with residential use. Therefore, its solid wastes do not have special characteristics and its influence in the general production of wastes is not significant. However, there are some exceptions.

d) Wastes from Markets

Wastes from markets have a defined character and are composed of rests of meat, fish, vegetables, fruits, and other food. Most are organic matter and packing materials. Compost production by manual methods is recommended for these wastes.

e) Wastes from Street Sweeping

Street sweeping and cleaning of public areas, such as central parks, fairgrounds and beaches contribute to waste production. These are composed mainly of leaves, grass, fruits, and peels, as well as paper, plastics, tins, glass, sticks, and a large amount of soil.

TABLE 5.2
Projection of Solid Waste Production and Composition (*)

Year

Annual population (persons)

Total PCP (kg/person-day)

Household

Commercial

Industrial

Sweeping

Markets

Others

Total

1

                 

2

                 

3

                 

4

                 

5

                 

6

                 

7

                 

8

                 

9

                 

10

                 

11

                 

12

                 

13

                 

14

                 

15

                 

(*) ton/year

f) Wastes from the Institutional Sector

In case of special institutions, such as schools, it can be assumed that the amount of solid wastes produced is not significant compared to other sectors and its composition is similar to others.

Health centers and hospitals do not affect total waste production since in most cases bed capacity is generally low or medium. It is necessary, though, to distinguish between domestic wastes (cleaning, cooking, and common refuse) and those generated by specific activities that produce infectious or hazardous wastes, such as sharp materials, gauzes, bandages, cotton, and organs from operating rooms, called "pathogenic or infectious wastes".

These wastes should be stored separately in closed polyethylene bags (of a special color), avoiding spillage and contact with the collection personnel, even if they wear gloves and protective clothing. The final disposal of these wastes should be local whenever possible and by incineration or bury in a pit of appropriate depth, at least two meters above the water table to avoid groundwater contamination.

If the municipality collects hospital wastes, it should be handled as described and disposed of in the manual sanitary landfill. As soon as the wastes arrive at the site, they should be placed at the bottom of the slope and covered with other refuse and soil.

Wastes produced in small communities do not present significant differences in physical composition to deserve an exhaustive study and they can be considered as domestic wastes. To calculate production, the residential sector is the most significant; the others are so minor that they do not appreciably affect the quantity of total waste. The exception are market wastes.

For this type of solid waste and for such small quantities, chemical composition is not of great importance since they are disposed of in a sanitary landfill.

5.1.2.2 Per Capita Production of Wastes

The per capita production of solid waste can be estimated as follows:

pcp = SWc in one weeek                          [5-2]
                 Pop   x 7 x Cov

Where:

pcp = Production per person per day (kg/person/day)
SWc = Quantity of solid wastes collected in one week (kg/week)(*)
Pop = Urban area population (person)
7 = Week days
Cov = Collection service coverage (%)

It is also possible to calculate the amount of solid waste produced by household, i.e. kg/household/day, since refuse is collected house by house, which makes possible to determine the number of houses.

Based on solid waste sampling in some small, rural, and marginal areas of Latin America, it was found that the pcp ranges between 0.2 and 0.5 kg/person/day. These values are representative and can be assumed for almost all populations.

It is recommended to consider this assumption because in most cases a field research (sampling) is not justified. The difference in the use of equation 5-2 is not significant since the quantities of solid wastes are small. In tourist areas, wastes left by the floating population should be considered.

5.1.2.3 Total Production of Wastes

According to solid waste production, it is possible to determine the collection equipment required, number of personnel, routes, collection frequency, final disposal area, costs, and urban cleaning tariff.

The production of solid wastes can be estimated using the following relation:

SWp = Pop x pcp                [5-3]

where:

SWp = Quantity of solid wastes produced (kg/day)

Pop = Urban population (person)

pcp = Per capita production (kg/person/day)

Note: See example 1 in Annex I.

5.1.2.4 Total Production Projection of Wastes

The annual production of solid wastes should be estimated based on population projections and per capita production.

As indicated below, population projections can be estimated by mathematical methods. However, regarding the pcp growth, it is difficult to find figures related to the annual variation of the pcp growth in order to evaluate changes. Since production indexes increase with urban and commercial development and population growth, it is recommended to calculate the total per capita production using an incremental rate of 1% per year (see Table 5.1).

5.1.2.5 Density of Wastes

The following estimates of density can be used to determine the size of the daily cell and the landfill volume:

  • Daily cell: density of refuse recently compacted
          400 to 500 kg/m3

  • Landfill volume: density of stabilized refuse
        500 to 600 kg/m3

These densities are achieved through homogeneous compaction as landfill stabilizes, which affects the stability and lifespan of the site.

Solid waste density in the manual sanitary landfill can be increased by the following ways:

  • The passing of the collection vehicle over the completed cell.

  • The manual tampering of wastes using a roller or tamper.

  • Separation and recovery of materials, such as paper, cardboard, plastics, glass, and scrap metal since they cannot be compacted easily. In addition to its economic benefit, recycling generates a smaller quantity of solid wastes to be buried and a longer lifespan of the site. Moreover, when separation is done at the source, more organized jobs may be generated.

  • Organic matter decomposition processes and the weight of the layers or cells are other factors that increase solid waste pressure and reduce volume.

5.2 Calculation of the volume needed

The requirement of space in the sanitary landfill depends on:

  • Daily production of solid wastes if 100% coverage is expected or the quantity of solid wastes collected.

  • Density of stabilized solid wastes in the manual sanitary landfill.

  • Quantity of cover material (20 to 25%) of the stabilized volume of solid wastes.

5.2.1 Solid waste volume

The first two parameters provide the daily and annual volumes of solid wastes that must be disposed of (Table 5.1, columns 6, 7, and 8), i.e.:

Vdaily =   SWp                                                                                                [5-4]   
              Dsw                      

Vannual = Vdaily x 365                                                                         [5-5]

where:

Vdaily = Volume of solid wastes to be disposed of in a day (m3/day)
Vannual = Volume of solid wastes in a year (m3/year)
SWp = Quantity of solid wastes produced (kg/day)
365 = No. of days in a year
DSW = Density of solid wastes, recently compacted (400-500 kg/m3) and stabilized (500-600 kg/m3)

5.2.2 LANDFILL VOLUME

The sanitary landfill volume for the first year can be estimated by adjusting the previous value with the cover material as follows:

VSL = Vannual x CM                   [5-6]

where:

VSL = Landfill volume in one year (m3/year)

CM = Cover material factor (1.2 to 1.25)

Data obtained are entered in Table 5.1, column 9. The following equation is used to estimate the total volume occupied during the landfill lifespan:

VSLLS = S VSL                               [5-7]
                 i =1

where:

VSLLS = Sanitary landfill volume during its lifespan (m3)
n = Number of years

which would be the data on Table 5.1, column 10, i.e., amounts accumulated annually.

5.3 Calculation of the area required

With this volume, the area required for the construction of the sanitary landfill can be estimated only if the depth or height of the landfill is known according to the topography of the site.

A manual sanitary landfill should be planned for a minimum of five years, although 10 years would be preferable. Sometimes it is necessary to plan it even for less than five years if land is not available. This period is called the lifespan or design period of the landfill.

The area required for the construction of a manual sanitary landfill depends mainly on factors such as:

  • Quantity of solid wastes to be disposed of

  • Quantity of cover material

  • Density of compacted solid wastes

  • Depth or height of the landfill

  • Volumetric capacity of the land

  • Additional areas for complementary works.

Based on equation 5-6, the area required can be estimated as follows (see Table 5.1, column 11):

ASL = Vsl                       [5-8]
                 Hsl

where:

VSL = Volume required for the sanitary landfill (m3/year)
ASL = Area to be filled successively (m2)
HSL = Average height or depth of the sanitary landfill (m)

and the total area required (Table 5.1, column 12) will be:

AT = F ASL                      [5-9]

where:

AT = Total area required (m2)
F = Incremental factor of the areas required for access roads, isolation areas, gatehouse, sanitary facilities, operation yard, etc. This is considered between 20% and 40% of the area to be filled.

Table 5.1 includes the parameters for calculating the sanitary landfill volume. The area should be estimated for every alternative site when the average depth of the landfill is known. See example 2 in Annex 1.

5.4 Selection of the construction method

As it was mentioned, the sanitary landfill design depends on the construction method adopted (trench, area, or a combination of both) according to the site topography, soil characteristics, and water table depth.

The design should consider the construction plans of the sanitary landfill:

  • Plan of the original land

The plan of the original land is obtained from the topographical survey of the landfill. It is required for the calculations and design of the work.See Figure 5.1.

FIGURE 5.1
Plan of the Original Land

  • ALTURA (m) = HEIGHT (m)
  • TERRENO ORIGINAL = ORIGINAL LAND
  • PERFIL = PROFILE
  • DISTANCIA (m) = DISTANCE (m)
  • Initial configuration of the supportive soil

Generally, the selected site should be prepared not only for the construction of the infrastructure but also to provide an adequate support base for the sanitary landfill and for obtaining cover material. This should accompany the topographical map to help the construction engineer in soil movement. Figure 5.2.

FIGURE 5.2
Initial Configuration of the Supportive Soil

  • ALTURA (M) = HEIGHT (M)
  • CORTES = SECTIONS
  • TERRENO NATURAL = NATURAL LAND
  • SUELO DE SOPORTE = SUPPORTIVE SOIL
  • DISTANCIA = DISTANCE
  • Final configuration of the landfill

The final configuration of the landfill is the conformation of the land once its useful life is over. It is important to represent it in a topographical map to show the maximum levels of the landfill, according to the planner. Figure 5.3.

FIGURE 5.3
Final Configuration of the Sanitary Landfill

  • CURVA DE NIVEL = CONTOUR LINE
  • SUPERFICIE FINAL = FINAL SURFACE
  • BASE = BASE
  • BERMA = BERM
  • SUELO DE SOPORTE – BASE = SUPPORT SOIL – BASE
  • Partial configurations of the landfill

The partial configuration(s) of the landfill represent(s) the progress of the landfill and serve(s) as a guide to the builder for the corresponding controls.

5.4.1 Trench or ditch method

Since small communities frequently do not have a caterpillar tractor or a backhoe, a lease or loan is recommended for the periodic excavation of trenches. Trenches should have a lifespan of 30 to 90 days. Excavation should be planned for the entire year, depending on the availability of the equipment.

Before the sanitary lifespan of the trench is over, the equipment should be available for the excavation of a new trench to continue the final disposal of solid wastes and to protect the environment. Otherwise, the service would be interrupted and the site may become an open dump.

According to the lifespan of the trench, the volume to be excavated and the required time of the machinery are calculated as follows:

5.4.1.1 Trench Volume (see Example 3 in Annex I)

VT = t X SWc x CM                                               [5-10]
                          Dsw
where:

VT = Trench volume (m3)
t = Lifespan (days)
SWc = Quantity of solid wastes collected (kg/day)
CM = Cover material factor, between 1.2 and 1.25 (or 20 to 25%)
DSW = Solid waste density in the landfill (kg/m3)

5.4.1.2 Trench Size

For manual operation, the size of the trench will be limited by:

The trench depth should be between two and three meters depending on the water table, type of soil, type of equipment, and excavation costs.

A width between three and six meters (according to the width of the equipment) is convenient to avoid transporting refuse and cover material over long distances, which makes the operation more efficient. The operation can be planned in such a way that soil can be stockpiled on one side and solid wastes can be unloaded on the other. Depending on the compaction degree and climate, the surface of a completed trench can be used to unload wastes.

The length is related to the lifespan of the trench. The formula is as follows:

l    =   Vt                                      [5-11]
            w x dr

where:

l = Trench length (m)
VT = Trench volume (m3)
w = Width (m)
dT = Depth (m)

5.4.1.3 Machinery Time

In general, the time required for trench excavation and soil movement will depend on the soil type, type and capacity of the machine, traction system (either caterpillar or wheel), and the operator skill (see example 3 in Annex I).

texc = Vt                             [5-12]
             P x WD

where:

texc = Time required for the machinery to excavate the trench (days)
VT = Trench volume (m3)
P = Excavation performance of heavy equipment (m3/hour)
WD = Workday (hours/day)

5.4.1.4 Lifespan of the landfill

Following Table 5.1, column 12, the area required may be estimated only if the average depth of the sanitary landfill is known. In practice, it is necessary to calculate the lifespan of the site (see example 4 in Annex I).

With regard to the trench method, once the trench volume is calculated, a factor for additional areas (separation between trenches(*), access roads, isolation areas, etc.) is assumed. The number of trenches that could be dug in the land is then estimated as follows:

n =  Al                                             [5-13]
                 F x AT

where:

n = Number of trenches
Al = Land area (m2)
F = Additional area factor, between 1.2 to 1.4 (20 to 40%)
AT = Area per trench (m2)

Then the lifespan will be given by:

L= ti x n 
            365

where:

L = Lifespan of the site (years)
tt = Service time of the trench (days)

FIGURE 5.4
Trench Distribution in the Site

- AREA DE CIRCULACIÓN = CIRCULATION AREA

5.4.2 Area Method

As mentioned before, the area method is used to build the sanitary landfill on the land surface or to fill depressions. A method for evaluating the volumetric capacity of the site is presented below.

5.4.2.1 Volumetric Capacity of the Site/

The volumetric capacity of the site is the total volume available to receive and store the refuse and cover material that forms the sanitary landfill. It is the volume between the surface of the soil base and the top surface of the landfill. It is essential to determine the volumetric capacity of the land.

There are two methods for calculating the volume:

  • For long, narrow volumes

  • For extensive volumes (in both directions)

a) Long Volumes (Around an Axis)

To determine the volume, the fieldwork includes the measurement of cross sections at regular ranges along an axis (polygonal). The areas/ of these sections are calculated and then, the volume of the material to be removed or placed can be estimated using the Simpson's rule for volumes or the prismoid rule.

Method 1. Volume Calculation Using the Simpson's Rule

Once the area of the different cross-sections is calculated, the volume of the material contained in the section or landfill can be determined by the Simpson's rule, which is the same used for areas, except that the areas of the sections replace those in the formula. (See Figure 5.5 and example 5 in Annex I).

Volume =   d  [A1 + A5 + 2 x A3 + 4 (A2 + A4)] m3                  [5-14]
                          3

If we call the medium section "M", the volume according to Simpson's rule will be:

Volume = 1   - (d/2) [A1 + A2 + 2(0) + 4M]                              [5-15]
                      
3

=   d  [A1 + A2 + 4M]                                                                 [5-16]
          6

FIGURE 5.5
Longitudinal Volume Around an Axis

This is the prismoid rule, which can be used to determine the volume of any prismoid, provided the area of the medium section is known (see example 6 in Annex I).

Note: The area of "M" is not the average of areas A1 and A2.

Method 2. Volume Calculation Using the Prismoid Rule

A prismoid is defined as a solid with two parallel flat faces of regular or irregular form, joined by flat or curved surfaces where straight lines can be drawn from one parallel face to the other. Figure 5.6 gives some examples of prismoids.

FIGURE 5.6
Prismoids

To determine the volume using the Simpson's rule, it is necessary to divide the figure in such a way that it results in an odd number of equidistant sections, where three is the lowest number.

FIGURE 5.7
Trench Volume

Method 3. Volume Based on the End Areas

From the project axis and lift leveling, the volume between two consecutive cross sections can be calculated by multiplying the cross sections average by the distance that separates them. Lengths of 20 meters are recommended.

The volume between sections A1 and A2 (see Figure 5.7) is given by:

                   (A1 + A2) x d
Volume = _____________                               [5-17]
                             2

where:

A1 and A2 = Cross section areas (m2)
d = Distance between sections A1 and A2 (m)

This formula will be more precise if A1 and A2 are similar. In general, this method is enough since it is assumed that the land will be leveled uniformly between the two sections, although the actual volume may be slightly different. (See example 7 in Annex I).

b) Extensive Volumes

Method 1. Graticule Method

To find the volume of a large, non-deep area, the fieldwork consists in covering the soil base surface with a graticule of squares to obtain the levels of its vertices. The total volume can be calculated as the total volume of all prismoids that have a graticule square as a cross-sectional area and the distance to the final landfill surface as height. This height will be given by the distance average between the final configuration surface of the landfill and the square vertices. For example, if the elevations of the vertices of a square are e1, e2, e3, and e4, the final surface elevation in that point is ef, and the area of every graticule square is A, then the volume would be:

Vi = A (ef - (e1 + e2 + e3 + e4)/4)                         [5-18]

The greater the precision degree obtained, the smaller the graticule squares (see example 8 in Annex 1).

Method 2. Based on Contour Lines

It consists in determining the capacity of the land between horizontal planes. Thus, it is necessary to calculate the intersection areas of those planes with the land, to calculate the average of them, and then multiply it by the height difference that separate them. Equation 5-19 must be followed.

V = (A1 + A2)            D h                                    [5-19]
                              
                       2

where:

V = Volume between two contour lines (m3)
A1 and A2 = Areas of the horizontal planes (m2)
D h = Height difference of the planes (m)

The volumetric capacity of the site is generally given by the following equation:

V =  (A1 x A2)D h1        (A2 + A3) D h2      (A3 + A4)  D h3                [5-20]
              2                             2                          2

When the areas taken are equidistant:

wpe4.gif (1333 bytes)

The smaller the increment of ?h, the more accurate the method. It is easier when a topographical map with contour lines at one-meter intervals is available and a planimeter is used for calculating the areas. In large sanitary landfills, this is the most common method.

Texto de la figura 5.8

  • Talud del terreno = Land slope
  • SECCIÓN A-A = SECTION A-A
  • NIVEL 4 = LEVEL 4

FIGURE 5.8
Top View and Cross Section of a Site

When contour lines are quite separated, the prismoid formula can be used to calculate the volume with certain precision. To apply the formula, it should be bear in mind that the planes of the contour lines divide the depression into several prismoids. The volume of every prismoid can be estimated by applying the prismoid rule or, in some cases, the Simpson's rule.

When using the prismoid formula, the areas of three contour lines are taken each time and the middle one is used as the medium section. The precision of the result depends mainly on the level difference among contour lines. In general, the smaller the interval, the greater the accuracy of the volume calculated.

5.4.2.2 Calculation of the Site Lifespan

The landfill volume or the volume between the initial and final configuration of the land, calculated by any of the methods described, will give the total volume available. Table 5.3 can be used to collect this information. The lifespan calculation is described below.

The available total volume of the land is compared to the values in Table 5.1, column 10, where the cumulative volumes of the landfill are specified, until an equal value or one slightly higher is found. The number of years equal to the lifespan of the landfill will be found on the same line in column 0.

5.5 Calculation of the cell

Cells are formed by solid wastes and cover material and the size should economize land and provide sufficient working face for unloading and maneuvers of collection vehicles.

The dimension and volume of the daily cell depend on factors such as:

  • Daily quantity of solid wastes to be disposed of.

  • Compaction degree.

  • Height of the most appropriate cell for manual work.

  • Working face required for waste unloading

TABLE 5.3
Volumetric Capacity for the Sanitary Landfill

 

LEVEL

HEIGHT OF THE SLOPE (m)

AREA (m2)

H (m)

VOLUME (m3)

 

SW QUANTITY

(ton)

 

LIFESPAN (months)

FOR EACH CONTOUR

LINE

AVERAGE BETWEEN CONTOUR LINES BETWEEN CONTOUR LINES ACCUM. SECTION ACCUM.
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
  • TOTAL LAND CAPACITY:                                                    ___________________ m3
  • SW VOLUME = TOTAL LAND CAPACITY 0.8:                      ___________________ m3
  • SW QUANTITY = SW VOLUME (m3) x DENSITY (ton/m3):    ___________________ ton
  • TOTAL LIFESPAN:                                                             ___________________ years

A height of 1.0 m, with a maximum of 1.5 m is recommended for the daily cell due to the low compaction of manual operations. This provide greater mechanical stability and the narrowest working face, which together with the cell length will be calculated depending on the daily waste volume as follows:

  • QUANTITY OF SOLID WASTES FOR DISPOSAL

The quantity of refuse required for designing the daily cell can be calculated in two ways:

- The quantity of solid wastes produced daily:

SWsl  =  SW p x      7                                            [5-22]
                             dw

where:

SWsl = Daily average quantity of solid wastes in the sanitary landfill (kg/workday)(*)
SWp = Quantity of solid wastes produced per day (kg/day)
dw = No. of workdays in a week (usually dw = 5 or 6 days, and even less in small municipalities)

  • VOLUME OF THE DAILY CELL

Vc  =   SWsl  x  CM                                                                      [5-23]
           Dmsl


Where:

Vc = Volume of the daily cell (m3)
Dmsl = Density of solid wastes recently compacted in the manual sanitary landfill, 400-500 kg/m3
CM = Cover material factor (1.20-1.25)

It should be noted that the density used for recently compacted refuse is less than the stabilized refuse used for volume calculation.

  • CELL DIMENSIONS

- Cell area

Ac  =     Vc                                                       [5-24]
              hc

 

where:

Ac = Cell area (m2/day)
hc = Cell height (m) - limited to 1.0 m to 1.5 m. Flintoff reports heights between 1.5 and 2.0 m for manual sanitary landfills, which reduces the amount of cover material required.

- Cell length (m)

l  =    Ac                                                                    [5-25]
          w

 w = Width set according to the working area required for refuse unloading by collection vehicles (m). In small communities, one or two vehicles will discharge at the same time, which determines the width of 3 to 6 m.

Since the slope (perimeter) must also be covered with soil, the relation between the width and length of the cell that would require less cover material will be a square one. This measure would be the square root of the cell area:

w = l = Ö Ac                                                                [5-26]

When this is not possible because the width is too narrow for vehicle unloading, the width is set and the length is calculated using the equation [5-25].

5.6  Labor calculation

The labor required in a manual sanitary landfill to form the daily cell depends on:

  • The quantity of solid wastes to be disposed of.

  • The availability and type of cover material.

  • Workdays at the landfill.

  • Working hours at the landfill.

  • Climatic conditions.

  • Unloading of wastes directly at the working face or at some distance from it.

  • Workers performance.

- Number of workers

The following calculations are presented to determine the number of workers required for the manual sanitary landfill, assuming eight-hours per day with an effective time of six hours. These figures are for normal working conditions and can vary according to the place and the factors already described. 

(*) To be adapted according to the region. 

Flintoff reports the following labor requirements for three sanitary landfills operated manually.

Site 1 30 tons/day 2 men/15 tons/man-day
Site 2 50 tons/day 6 men/8 tons/man-day
Site 3 100 tons/day 10 men/10 tons/man -day

The density of wastes found in these sites was between 250 and 400 kg/m3. For a given tonnage, the volume handled could be equal or greater than in developing countries.

The following table indicates the probable labor requirements and cover material for typical waste generation and density rates in Latin America. 

   

V O L U M E (m3/day)

Population

Ton/day (pcp=0.5 kg/persons/day)

Loose refuse
(330 kg/m3)

Comp.
refuse
(500 kg/m3)

Cover material

 

Men

20,000

10

30

20

4

4

50,000

25

75

50

10

10

100,000

50

150

100

20

19

SUPERVISOR ¡VERY IMPORTANT!

In addition to the number of workers who will construct the manual sanitary landfill, it is necessary to have a supervisor to direct the operation.

Since hiring a professional trained in solid waste management is expensive, it is recommended to have a person with the following characteristics for the position of supervisor:

  • Sanitation technician, or

  • Sanitation promoter with experience.

It should be noted that the presence of the supervisor in the sanitary landfill is important during almost all working hours, especially during the first months. As the work advances, it is possible to reduce the time on site to two hours per day: one hour in the morning and one in the afternoon. Thus, it will be possible to supervise urban cleaning in general and monitor the service quality.

Ultimately, supervisory tasks can be carried out by the chief of public works of the municipality with the support of sanitation promoters.

5.7 Cost analysis

As in every design, a cost evaluation or budget for the project should be included. The costs are divided into:

  • capital costs

  • operating costs.

To determine capital costs, each item must be associated with the landfill lifespan as infrastructure works will be constructed for the design period.

  • Capital costs

a) Studies and designs

b) Land acquisition

c) Land preparation and complementary works

- Cleaning and clearance

- Soil movement (machinery leasing)

- Internal and external access roads

- Perimeter drainage

- Leachate drainage system

- Site enclosure

- Tree-planting around the perimeter

- Booth

- Sanitary facilities

- Signs

- Others

d) Closure of the old garbage dump

- Studies and design

- Rent of equipment

- Purchase of cover material (if not available on-site)

- Vegetation planting.

  • Operating costs

- Labor

- Tools

- Safety clothing and equipment

- Gas and secondary drainage

- Maintenance

- Periodic adaptation of the site (roads, drainage, excavation, etc.).

  • Final closure costs

- Final cover

- Drainage

- Grass or vegetal cover.

5.7.1 Budget preparation

The planner or person who has designed the landfill should prepare a capital budget for the mayor or institution responsible for the work. The capital cost categories are listed in column (a) in Table 5.4, and its costs in columns (b) and (c). The total of column (c) will give the initial or capital investment required to initiate the work. Each work category is described below.

a) Studies and designs. The previous studies and the executive project of the landfill will involve costs for the municipality. They will vary depending on whether a consultant would be hired or if an institution could provide support for this type of technical assistance. In other cases, the municipality may pay only the per diem or the topographical survey.

b) Land acquisition. In column (b), the cost of the land will be considered if it is private, but it will be zero if the land belongs to the municipality. If the land is rented, then the value in column (b) will be zero and the cost will be considered under recurring or operating costs.

c) Land preparation and complementary works. This category is estimated by quantifying the working volumes for each component, such as cleaning and clearance, soil movement, and access roads, which should be placed in column (b) of Table 5.5 (Table 5.7 is used as a reference to facilitate the completion of Table 5.4). To estimate the amount of work, construction maps similar to those in Figures 5.1 and 5.2 and detail maps are used.

Column (c) contains the units in which the working volumes are measured. They can be changed if necessary. 

TABLE 5.4
Investment Costs

CONCEPT (a)

INITIAL INVESTMENT

UNIT INVESTMENT COSTS ($)

Partial (b)

Total (c)

Lifespan (years) (d)

Annual cost ($/year) (e)

IMA ($/year) (f)

Capital cost ($/year) (g)

Annual performance (t/year) (h)

(i)

a) Studies and designs

               

b)Land acquisition

               

c) Facilities and preparation works

               

- Cleaning and clearance

               

- Soil movement

               

- Access routes

               

- Rain drainage

               

- Leaching

               

- Fences and gate

               

- Tree planting

               

- Booth

               

- Sanitary facilities

               

- Sign

               

- Others

               

d) Dump closure

               

- Studies and design

               

- Rent of machinery

               

- Cover material

               

- Vegetation planting

               

TOTAL

               

In column (d) unit work costs are entered. Engineers, foremen, and persons related to the construction of public or private works usually know the local costs. Many ministries, development corporations, and other organizations have unit cost catalogs that are updated periodically. If such data are not available it will be necessary to calculate them using manuals or data from manufacturers.

Finally, in column (e) of Table 5.5 the cost of each component, which is equal to the product of columns (b) and (d), is introduced. The costs obtained are entered in column (b) of Table 5.4.

d) Closure of the garbage dump

Closing an open garbage dump is relatively easy if machinery and cover materials are available. However, to estimate the amount of work and prevent environmental damage or health risks, it is necessary to establish a plan including the future use of the site. In this case, Table 5.5 should be used and some categories may be added, if necessary.

TABLE 5.5
Costs of Landfill Opening and Garbage Dump Closure 

CATEGORY

(a)

Work quantity
(b)

Unit (m, m2, m3, hr)
(c)

Unit cost
($/unit)
(d)

Cost
(e)

c) Landfill opening

- Cleaning and clearance
- Soil movem
- Access roads
- Storm drainage
- Leaching drain.
- Fences
- Tree-planting
- Booths, warehouse, etc.
- Sanit. facilities
- Signs
- Gate
- Others

d) Dump closure

- Studies and design
- Rent of machinery
- Cover material
-        Vegetation

 

 

 

 

 

   

TOTAL

       

 

Finally, once Table 5.5 is completed, its results should be transferred to Table 5.4 where the total of column (c) will give the initial investment required. This capital can be obtained through a loan including interest payments.

5.7.2 Estimate of the unit capital costs

The unit capital costs and interests are calculated to be included in the total costs of the sanitary landfill and in the calculation of the user fee. Thus, it is necessary to calculate the annual or hour cost and afterwards the unit cost according to the production or performance:

Cn  =     Ctotal                                                            [5-27]
                 n

 where:

Cn = Cost per year or hour according to n

Ctotal = Total cost of the concept

n = Lifespan of the work or concept (for example, 5 or 10 years for a sanitary landfill)

For the unit cost:

Cu  =     Cn                                                                [5-28]
             P

where:

Cu = Unit cost (for landfills, $/ton)
P = Performance per year or hour (for example, for a manual landfill receiving 10 tons per day that works 300 days in the year, it would be 10 x 300 = 3,000 tons per year).

In Table 5.4 the total costs are in columns (b) and (c). The "n" times of equation [5.27] are given in column (d) of the same table. In general, "n" is the lifespan of the sanitary landfill; however, there are some elements that could have a shorter life than that of the landfill. It is recommended to depreciate everything in the lifespan of the landfill. The annual cost, which is also called annual depreciation, is calculated in column (e) using the equation [5-27], i.e., by dividing the value in column (c) by that in column (d).

Column (f) of Table 5.4 shows the annual average interest for capital recovery. The interest can be calculated with an approximate formula:

AAi  =  Ctotal     (n + 1)     i                                                             [5-29]

 

where:

AAI = Annual average interest ($/year)
Ctotal = Total cost of the concept
n = Lifespan in years (landfill)
i = Annual interest

The total of columns (e) and (f) gives the corresponding values for column (g), i.e., annual capital costs. The annual capital cost (g) can also be calculated directly from the total cost (d), using the tables or formulas for capital recovery. Engineering economics texts include tables that give the capital recovery factor (CRF) in relation to the annual interest and lifespan. The calculation can also be done using the following formula:

Cc = Ctotal (CRF)                                                 [5-30]

crf  =        i                                                                         [5-31]

         1  -      1  
                  (1 + i)n

where:

Cc = Capital cost ($/year)
Ctotal = Total cost ($)
i = Annual interest of the loan or municipal bank interest (if the interest is 13%, i = 0.13)
n = Lifespan in years

Once the capital cost is calculated by any of the above methods (column (g), Table 5.4), it is divided by the annual production or performance R (see column 5, Table 5.1) to obtain the unit cost in column (i) of Table 5.4. As it can be observed, annual performance or the number of tons received in the landfill will increase annually as the unit capital cost decreases. To avoid this, a performance "R" average can be assumed for all the lifespan of the landfill.

5.7.3 Estimation of operating costs

Based on the operating or recurring costs, the annual budget can be estimated to properly operate the landfill and to collect an equitable tariff.

5.7.3.1 Annual Labor Cost

The amount of personnel is calculated as in Section 5.6. The performance suggested can be modified according to the experience and conditions of the site.

Generally, the cost will be given by:

alC = 12 N (sbF mW) + 12 Q (sbF mW)                                                        [5-32]

where:

alC = Annual labor cost ($/year)
N = Number of workers in the landfill according to Section 5.6
mW = Local legal minimum wage ($/month)
sbF = Social benefits factor, generally between 1.4 and 2.0. It includes items such as social security, pension fund, and vacations.
Q = Quantity of time or day that the supervisor devotes to the landfill (0.2 to 0.25 in small landfills)
sW = Monthly wage of the supervisor ($/month).

5.7.3.2 Tools and Protective Clothing

The tools used will depend on the landfill size and are described in Section 6.1.4. It is assumed that they have a lifespan of one year.

The protective clothing may include two uniforms per year, one pair of boots, spectacles, mask, and gloves. The costs will depend on local prices.

5.7.3.3 Drainages, roads, machinery, and others

Each year, an evaluation should be done according to the plans and progress of the work, costs of drainages and roads that should be constructed, number of hours that machines should be rented, materials, and temporary labor required.

The total of the three previous categories will give the annual cost or annual operation budget:

aoC = lC + tC + mC + Others                        [5-33]

where:

aoC = Annual operation cost ($/year)
lC = Annual labor cost ($/year)
tC = Annual tool cost ($/year)
mC = Annual machinery cost, etc. ($/year)
Others = Other annual costs ($/year).

5.7.3.4 Unit Operation Costs

The unit operation cost will be the annual cost previously calculated divided by the number of tons buried during the year.

uoC   =  aoC                                                                                                    [5-34]
               P

where:

uoC = Unit operation cost ($/ton)
aoC = Annual operation cost ($/year)
P = Annual performance (tons/year).

5.7.4 Total costs and rates

5.7.4.1 Total Costs

The total annual and unit costs would be:

taC = nC + aoC                                                                                     [5-35]
tuC = uC + uoC                                                                                      [5-36]

where:

taC = Total annual cost ($/year)
tuC = Total unit cost ($/ton)
nC = Annual capital cost according to the equation [5-27], ($/year)
uC = Unit capital costs according to the equation [5-28], ($/ton)
aoC = Annual operation costs according to the equation [5-33], ($/year)
uoC = Unit operation costs according to the equation [5-34], ($/ton).

5.7.4.2 Tariffs

The tariffs applied to the population vary according to the policies established by the municipality or local jurisdiction and can be determined as follows:

a) Total recovery without cross subsidy. In this case, families pay for the actual cost of the service, regardless of their economic situation. The average monthly rate would be:

Ttr  =  taC                                               [5-37]
         12 Frs

where:

Ttr = Monthly tariff per family for total recovery ($/family/month)
taC = Total annual cost of the service according to the equation [5-35], ($/year)
Frs = Number of families receiving the service in the population.

b) Total recovery with cross subsidy. In this case, service tariffs are collected according to the status of the family, provided the total income through tariffs covers the capital and operation costs, i.e., taC. One way of doing this is to associate tariff collection with another service, preferably electric service, which has greater coverage, or to the real estate tax or water tariff. The percentage that would have to be applied to the charge for other service would be:

Inc  =   taC  (cc¦) (100)                                               [5-38]
            osL

where:

Inc = Increase in the household rate (%)
taC = Annual cost of the urban cleaning service ($/year)
osI = Annual income from household charges for other services
cc¦ = Collection cost factor, i.e., costs that the other service should charge for additional personnel, etc.

The other services almost always include a cross subsidy. The urban cleaning tariffs to industries and special centers would have to be separated, especially for large consumers of other services. For example, industries consuming a great deal of electricity and producing little refuse could be adversely affected if adequate care is not taken.

c) Recovery of operating costs. In many cases, municipalities would have obtained support or a subsidy to cover the initial investment; in this case, the annual service cost would be the operating costs and in the equations [5-37] and [5-38] taC would be replaced by aoC.

The average tariffs could also be calculated in the following way, according to production:

MTi   =   30 (PCPi) (tuC) (N)                                                             [5-39]
                        1000

where:

MTi = Monthly tariff per family for the socioeconomic stratum "i" ($/month/fam.)
PCPi = Refuse generation in the socioeconomic stratum "i" (kg/person/day)
tuC = Total unit cost ($/ton). It can be replaced by aoC if the service is subsidized
N = Average number of persons per family
30 and 1,000 = Dimensional parameters in (days/month) and in (kg/ton), respectively.

5.7.5 Tariff collection

In the previous section, it was stated that the sanitary landfill tariff can be collected together with other services. In general, the cost of collecting the tariff for waste collection and sanitary landfill should range between 10 and 20% of the total tariff.

Urban cleaning tariffs can also be collected separately from other services. This is usually very expensive and does not have any coercive measure because if the refuse service is cut off, the user is less concerned than when electricity or drinking water services are suspended.

6. Operation and maintenance

6.1 Operation

6.1.1 Closure of the municpal dump.

For the successful operation of the system, all dumps in the municipal area should be closed.

To close a dump, the following steps should be taken whenever possible:

  • Publicize the dump closure and announce that refuse disposal will no longer be permitted. Advise the community of the existence of the sanitary landfill and its location to obtain cooperation.

  • Inform merchants that sporadically generate great amount of refuse and hire a private service, to dispose of their refuse at the sanitary landfill.

  • Place notices of the penalties that will be applied to anyone who does not comply with the regulations.

  • Build a fence to block the entrance of strangers and animals.

  • Implement a program to exterminate rodents and arthropods (Figure 6.1). The advisory of the environmental sanitation division of health services is important in this activity. If this program is not implemented, vermin migration to nearby dwellings will create health risks and problems.

FIGURE 6.1
Extermination of rodents

  • Immediately after the extermination, cover all dumps with a layer of well-compacted soil of 0.20 m and 0.40 m thick. Provide drains to prevent erosion.

  • Plant vegetation on the cover soil all over the area.

6.1.2 Operation control

The work of the sanitary landfill should be strictly organized and supervised to accomplish the proposed objectives. This is achieved through:

  • Control of solid waste at the entrance (porter's booth) (Table 6.1).

  • Control of vehicle (porter's booth).

  • Traffic and waste unloading direction (operation area).

  • Unloading at the working face (supervisor).

  • Control of the size and shape of cells and cover material (supervisor).

  • Adequate distribution of the work program (supervisor).

  • Appropriate maintenance of tools and provision of protective clothing to workers (supervisor).

  • Surveillance to impede the entry of animals and strangers, and excavation of solid waste materials in the already formed cells.

TABLE 6.1
Control of solid waste entrance

Month:

Day

Date

SOLID WASTE

COVER MATERIAL m3

OBSERVATIONS

No. of trips

Volume m3/day

Quantity kg/week

Monday

           

Tuesday

           

Wednesday

           

Thursday

           

Friday

           

Saturday

           

Subtotal

           

Monday

           

Tuesday

           

Wednesday

           

Thursday

           

Friday

           

Saturday

           

Subtotal

           

Monday

           

Tuesday

           

Wednesday

           

Thursday

           

Friday

           

Saturday

           

Subtotal

           

TOTAL

           

Weight = Volume x density

6.1.3 Labor

In a manual sanitary landfill all operations are based on the work performed by the municipality or community workers. The number of workers depends on the amount of solid waste to be buried, climatic conditions, and landfill construction method (see Chapter 5, item 6).

In addition, it is necessary to have a sanitation chief or supervisor to direct the operation. 

6.1.4 Tools

The equipment used to operate a manual sanitary landfill are masonry tools such as wheelbarrows with pneumatic tires, shovels, pikes, large hoes, crowbars, wood tampers, as well as pitchforks or rakes and a compacting roller. Figures 6.2 to 6.4 

  • Pala = Shovel
  • Azadón = Large hoe
  • Barra = Crowbar
  • Pica = Pike
  • Pisón de mano = Tamper
  • Horquilla = Pitchfork
  • Rastrillo = Rake
  • Tablones = Planks

FIGURE 6.2
Work tools

- Llanta neumática = Pneumatic tire

  

FIGURE 6.3
120-liter wheelbarrow with pneumatic tires

  • Cuchilla de limpieza = Cleaning blade
  • Nivel de aceite = Oil level
  • Eje = Axis
  • Tapón de llenado = Plug
  • Radios = Radius
  • Rodillo rígido de bolas = Rigid ball roller

 FIGURE 6.4
55-gallon barrel equipped as a roller-compactor

The number of tools depends on the number of workers and the amount of solid waste buried in the landfill.

To carry cover material or refuse, it is recommended to place a few planks across the already constructed cells on the surface of the landfill to facilitate wheelbarrow movement, specifically in rainy periods to improve productivity (Figure 6.5).

  • Drenaje = Drainage
  • Frente de trabajo = Working face
  • Primera celda = First cell
  • Horquilla = Pitchfork
  • Pisón = Tamper
  • Pala = Shovel

FIGURE 6.5
Wheelbarrow over the landfill

6.1.5 Construction of a sanitary landfill

The manual sanitary landfill should be built according to a general plan. The supervisor, however, will be empowered to act according to his judgment when unexpected situations arise such as weather changes or emergencies.

The landfill infrastructure should be built before refuse is unloaded.

Unlike a landfill operated with mechanical equipment, in a manual sanitary landfill it is recommended to unload refuse and cover material from the upper part of the already completed cell. This will help the workers to form the cell and maintaining a narrow working face.

It is important to train all workers from the sanitation service in the construction, operation, and maintenance of the sanitary landfill, as well as in the entire process of waste management. The role of the personnel to achieve good results and the relevance of each activity should be emphasized.

The sanitation supervisor should remember that a worker would be more productive if there are good working conditions.

The steps for constructing the cells are the following:

  • For constructing the first cell, limit the area according to the amount of waste and compaction degree. This will provide precise information to the workers.

  • Unload refuse at the working face to keep a single and narrow area uncovered during the day and to avoid long-distance transportation.

  • Spread refuse in thin layers of 0.20 m to 0.30 m thick and compact it until it reaches the recommended height in the working face.

  • Use enough soil to cover the compacted refuse completely and fill any surface irregularities. This should be done once a day and at the end of the working day.

  • Compact the entire cell uniformly.

Once the first cell basis is completed, a vehicle should drive over it during dry periods to achieve larger compaction. Waste is unloaded at the working face and spread downward maintaining a gradient of 3:1 (H:V).

Figures 6.6 to 6.24 show the construction method and manual operation of a landfill.

  • Area method  

  • 1ª. CELDA = 1ST. CELL
  • 2ª. CELDA = 2ND. CELL
  • 3ª. CELDA = 3RD. CELL
  • AVANCE DEL RELLENO = LANDFILL GROWTH
  • TALUDES = SLOPES
  • VÍA DE ACCESO INTERNA= INTERNAL ACCESS ROAD
  • SUELO DE SOPORTE = SUPPORT SOIL

 

FIGURE 6.6
Land prepared for landfill construction

- UBICACIÓN PRIMERA CELDA = LOCATION FIRST CELL

FIGURE 6.7
Solid waste unloading

 FIGURE 6.8
Spreading refuse in the cell

 

FIGURE 6.9
Waste compaction with a manual tamper

FIGURE 6.10
Soil extraction to cover refuse

  

FIGURE 6.11
Solid waste covering

 FIGURE 6.12
Compaction of a finished cell (first cell)

 

  

FIGURE 6.13
Construction of gas vents

FIGURE 6.14
Construction of the second cell supported on the first one

  • TIERRA PARA COBERTURA = COVER SOIL
  • CHIMENEA = VENT
  • FRENTE DE TRABAJO = WORKING FACE
  • VÍA ARTIFICIAL CON TRONCOS DE MADERA = ARTIFICIAL ROAD WITH LOGS
  • TOPE DE CONTENCIÓN = BARRIER
  • 2DO. NIVEL DE CELDAS = 2ND. LEVEL OF CELLS
  • COBERTURA DIARIA = DAILY COVERAGE

FIGURE 6.15
Construction of first terrace

  • CUNETA DE LA VÍA = DITCH
  • BERMA EN CADA TERRAZA TERMINADA = BERM IN EACH TERRACE FINISHED
  • FRENTE DE TRABAJO = WORKING FACE
  • TALUDES PROTEGIDOS CON GRAMA = SLOPES PROTECTED WITH GRASS
  • DRENAJE OPCIONAL PARA AGUA DE LLUVIA = OPTIONAL DRAINAGE FOR RAINWATER
  • CHIMENEA = VENT
  • AVANCE = LANDFILL GROWTH

 

FIGURE 6.16
Construction of the final terrace

  • DRENAJE EN PIEDRA = STONE DRAINAGE
  • TOPE O BARRERA DE PROTECCIÓN = PROTECTION BARRIER
  • MATERIAL DE COBERTURA = COVER MATERIAL
  • CANAL PARA AGUA DE LLUVIA = RAINWATER CHANNEL
  • DESECHOS SÓLIDOS = SOLID WASTE

 

FIGURE 6.17
Solid waste unloading

  

  • PEND 2%= SLOPE 2%
  • DRENAJE EN PIEDRA = STONE DRAINAGE

FIGURE 6.18
Waste spreading

Filling the daily cell

FIGURE 6.20
Manual compaction

 

FIGURE 6.21
Landfill trenching

  • TOPE = BARRIER

  

  • MATERIAL DE EXCAVACIÓN = EXCAVATION MATERIAL
  • TOPE = BARRIER
  • 2ª. ZANJA = 2nd. TRENCH
  • ZANJA TERMINADA = FINISHED TRENCH

FIGURE 6.23
Second trench

  • MATERIAL DE LA EXCAVACIÓN DE LA TRINCHERA = MATERIAL FROM TRENCH EXCAVATION
  • COBERTURA = COVERAGE
  • FUTURAS TRINCHERAS = FUTURE TRENCHES
  • ESTACAS DE SEÑALIZACIÓN = SIGN POSTS
  • TRINCHERAS TERMINADAS = FINISHED TRENCHES
  • VÍA CIRCULACIÓN INTERNA = INTERNAL ROAD
  • CANAL = CHANNEL

FIGURE 6.24
Ditches or trenches growth

6.1.6 Operation in rainy periods

Most problems related to the operation of a sanitary landfill occur during rainy periods due to the following reasons:

  • It is difficult for collection vehicles to transit on the already formed cells. There are possible obstructions due to the low density of manual compaction.

  • It is hard to extract and transport cover material and to form the cells which result in lower worker productivity.

  • During heavy rain periods, the unloading of refuse and cover material can be done only on the terrace, which slows down the cell formation and compaction. Therefore, if appropriate measures are not taken, the landfill appearance deteriorates because of scattered refuse and the presence of buzzards.

  • Greater production of leachate because rain falls directly on filled areas.

These factors oblige the following precautions:

  • Reserve a few areas less affected by rains, with access roads to operate under the worst conditions.

  • Construct a road with logs of three meters length to form a "floor". These logs should be bound together by a thick wire of 1/8" diameter. After assembling the module, it should be covered with gravel to prevent vehicles from skidding.

  • This artificial road is constructed according to the landfill's requirements and growth in modules of three meters length by three meters width. This is the commercial size of the logs and they can be reused in the future.

  • It is recommended to assemble the modules at the site. The soil must be well compacted to minimize settling and good drainage should be provided. Figures 6.25 and 6.26.

  • Use debris to build and maintain some internal roads.

- MÓDULO TERMINADO = FINISHED MODULE

  

FIGURE 6.25
Construction of the log floor

 

FIGURE 6.26
Placing gravel on the logs

  • During one or several days of the week, hire two or three more workers to maintain the landfill in good condition under bad weather

  • Plan soil movement operations during dry periods, whether for extracting cover material or for opening trenches and leave only refuse burial for rainy periods.

  • As a routine practice, cover the cells with plastic material to prevent rainwater from filtering through the refuse.

  • Maintain narrow working areas by supporting the cells on the land slope. Overlap three or more cells near the internal road to achieve vertical rather than horizontal growth. Figure 6.27.

  • VIA INTERNA = INTERNAL ROAD
  • VIA PRINCIPAL = MAIN ROAD
  • CASETA = BOOTH
  • NIVEL DE CELDAS DEL RELLENO SANITARIO = CELL LEVEL OF THE SANITARY LANDFILL
  • CANAL PERIMETRAL = PERIMETRIC CHANNEL
  • AVANCE DEL RELLENO = LANDFILL GROWTH
  • DESCARGA DE DESECHOS = WASTE UNLOAD
  • MATERIAL DE COVERTURA = COVER MATERIAL
  • VENTILAS DE GASES = GAS VENTS

 

FIGURE 6.27
Landfill operation in narrow rainy areas

 6.1.7 Work safety

The personnel working in urban cleaning services (collection, transportation, and final disposal of wastes) are constantly exposed to accidents on the road as well as to infectious diseases. Such accidents may have two causes: unsafe working conditions or worker negligence.

The main unsafe working conditions are:

  • Collecting refuse manually, without using gloves not dustpans that may result in cuts on handsdue to broken glass or sharp metals.

  • Handling very large receptacles that demand excessive effort by the worker causing cuts, dislocations, sprains, and lacerations.

  • Long workdays causing fatigue.

  • Lack of adequate uniforms and protective equipment.

Negligent workers usually commit the following:

  • They do not use protective clothing.

  • They drink alcoholic beverages during the workday.

  • They lift containers or heavy objects improperly.

  • They do not pay attention to vehicle traffic.

All unsafe working conditions as well as the most common causes of occupational accidents and risks should be carefully identified to solve them adequately. Recommendations for minimizing these problems are indicated below:

  • Evaluate the causes of the most common accidents and adopt the corresponding preventive measures.

  • Prepare work safety standards with instructions for the use of equipment.

  • Provide workers with a place with lockers and showers where they can wash and change clothes after work to avoid taking home any kind of contamination.

  • Establish a medical examination program to identify potential contamination risks.

  • Improve the quality of equipment and tools. Standardize the shape, size and weight of receptacles. Require, at least in the commercial sector, the use of plastic containers of 60 to 100 liters capacity. For the residential sector, conduct a good promotional awareness campaign.

  • Provide workers with gloves, boots, and at least two uniforms a year. Figure 6.28.

  • OVEROL = OVERALL
  • GUANTES = GLOVES
  • BOTAS = BOOTS

FIGURE 6.28
Protective clothing

"THE SUPERVISOR SHOULD CONTROL SAFETY STANDARDS COMPLIANCE"

6.2 Maintenance

6.2.1 Resources

Unlike other works, the construction of a sanitary landfill requires permanent supervision and maintenance. This implies expenses which, though minimal, should be made on a timely basis. These resources should be considered in the municipality's annual budget.

6.2.2 Supervision

One of the most important persons at a sanitary landfill is the sanitation chief or supervisor, who should organize, direct, and control the operation on the site. He should have full support of the municipal administration.

If a manual sanitary landfill does not have good supervision or adequate technical and financial maintenance, it can easily become an open dump.

"A sanitary landfill requires constant supervision to prevent future deficiencies"

6.2.3 Access roads

Access roads, the working face, rain drainage networks, and completed landfill areas should be maintained in good working conditions.

The cost of maintaining access roads is lower than repairing a collection vehicle. Therefore, stones, debris, and soil should be stored for that purpose. The working face should be neat and clean. 

6.2.4 Supply of material and tools

At the end of the workday tools should be cleaned. If they are damaged or broken, they should be repaired or replaced as soon as possible.

One of the greatest administrative problems is material supply, which must be planned. Spare parts and other materials should be kept in the municipality's warehouse. It is also important to monitor the supply of tools and implements to workers. This is done for two reasons; for inventory purposes and to determine when replacement is required because of damage. See Table 6.2.

6.2.5 Fly control

Fly control in the landfill should not be carried out with insecticides, since its excessive use not only causes environmental pollution, but builds up fly resistance. Instead, soil coverage should be the main method to control flies. However, flies come to the site in the collection vehicles and when their presence become annoying, it is recommended to fumigate the landfill area. Figure 6.29.

 

FIGURE 6.29
Fumigation in the sanitary landfill area

6.2.6 Spread material

It is important to keep clean the areas adjacent to the daily working face. Pieces of paper accumulated and blown out by the wind provide a poor aesthetic appearance to the landfill. One of the workers should collect all these scattered materials at the end of the workday using a sack or bag and deposit them at the site where the cell is constructed. Figure 6.30.

  

FIGURE 6.30
Collection of material spread over the landfill area

6.2.7 Fire control

Paper, cardboard, plastics, etc. should not be burned in the landfill area, because the decomposition of refuse produces methane, a combustible gas, which can start fires. Also, burning these materials makes the site look like an open dump.

6.2.8 Water control

Peripheral rain drainage (channels, culverts) and landfill surface should be kept in good conditions. In addition, the working face should have drains to facilitate vehicle movement.

6.2.9 Seepage drainage

The large amount of fine material in water clogs the drains progressively, making it necessary to clean them periodically. Such material should be extracted from the trench that conducts the leachate to the filtration field. Otherwise they will clog and overflow on the surface.

 6.2.10 Gas drainage

Because of landfill settlements, motor vehicle transit on the cells, and other reasons, gas vents are deformed and inclined. It is necessary to keep them vertical as the level of the landfill rises to prevent their obstruction and loss.

6.2.11 Final finishing and settlement

The placement of the final cover and grass layer requires great care since it affects both the operation and final appearance of the completed landfill.

Solid waste decomposes (a part is transformed into gas and part into fluid) over time and the cover soil and moisture penetrate through its gaps, settling it. After two years there is less settlement and after five years there is practically none. Since the settlement is not uniform, depressions occur in the landfill surface, where rainwater accumulates. Therefore, the soil should be leveled and a drainage should be constructed.

The local administration should make sure that once the lifespan of the sanitary landfill is over, it should receive the final finishing and maintenance required, for its further use by the community. If this is not done, the community will not benefit from this basic sanitation work. This could be a cause for rejecting new sites. It could mean locations more distant from urban areas which will increase waste transportation and sanitation service costs.

It is recommended to place a sign with the name of the work, park, or sports field, indicating that it has been built on a sanitary landfill.

7. Administration and control

  7.1 Administration

An administration is required to construct and operate a manual sanitary landfill according to the specifications and recommendations given in the study or final report of the project and to ensure that the objectives are fulfilled. Since the final disposal of solid wastes depends on a cleaning service, the landfill must be responsibility of the administrator of this public service. In our society, this administrator is usually a member of the cleaning service office or public works area of a municipality.

The sanitary landfill administration should consider public relations as a priority during both the construction and landfill closure. Public opinion plays a definitive role in promoting and publicizing this basic sanitation work in areas where a new landfill is required.

 7.1.1 Supervision

To improve the cleaning service quality in small municipalities, a sanitation technician or promoter should be contracted as chief or supervisor of the urban cleaning service.This person will then be responsible for coordinating both the landfill and the entire cleaning service and will serve as liaison between users, workers, and the administration.

The administrators of the cleaning service should be informed about the quality of the sanitary landfill operations on a regular basis.

Among other functions, the cleaning supervisor will carry out the following specific activities:

  • Give instructions and assign tasks based on the administration program for each of the services (refuse collection, transportation, and final disposal).

  • Monitor the efficiency and quality of the service and plan the supply and maintenance of materials, tools, and equipment required.

  • Exercise appropriate control of both collection and the sanitary landfill itself.

  • Report periodically on the execution of activities and possible problems.

When possible, it is recommended that the turnover of the staff trained in the different urban cleaning aspects –especially construction and operation of sanitary landfills– be the lowest possible, since this reduces efficiency and increases costs.

7.1.2  Productivity indicators

To manage the different activities adequately, the administrator of the cleaning service has to analyze two main factors: costs and productivity.

The sanitary landfill is under continuous construction and operation, thus, it is necessary to have comparative indicators with other sanitation service activities and similar works. With these indicators it is possible to evaluate productivity and costs, promoting maximum use of available resources.

It is necessary to implement several measures and controls to identify deficiencies, apply corrective measures, and evaluate their effectiveness. This is done to achieve the best productivity and provide an efficient service at the lowest possible cost.

A few indicators used to direct and manage a manual sanitary landfill (MSL) are indicated below

UNITS

-Total production of refuse
  =
Urban population x production per capita

(kg/day)

-Cost of financing a sanitary landfill
   
Initial investment for sanitary landfill
=  Total municpal budget

x100 (%)

- Final disposal coverage
= Tons disposed of in MSL 
     Tons collected

x 100 (%)

- Personnel efficiency in final disposal
  =  Tons disposed in MSL x dcay
          Sanitary landfill workers

x 100 (tons/man/day)

- Final disposal cost
   =  Cost of operating MSL x year

x 100 ($/ton)

- Capital cost per ton of refuse
  =  Estimate in column (g) of Table 5.1)

($ton)

- Total unit cost of landfill
  =  formula [5-36]

($ton)

7.2 Control of the manual sanitary landfill

Despite the small size of this sanitation work, it represents an essential activity in the solid waste management for any community. It should, therefore, be carried out in the best possible manner.

It is important to make periodic evaluations to maintain appropriate control in the following areas:

7.2.1 Operation control

  • Admittance of materials (refuses and soil):

. Amount (weight and estimated volume)

. Origin (urban area sector)

Solid wastes not authorized by the administrator will not be accepted.

Entrance of vehicles and visitors

  • Personnel schedule

  • Tool maintenance

  • Unusual situations

7.2.2 Construction control

By maintaining the alignment of the platforms and the height specified for the cells it is possible to control the construction of the manual sanitary landfill using the project's design plans or even by simple observation. The slope gradients should provide the stability required for the work according to the topography of the land.

7.2.3 Cost control

One of the aspects constantly neglected by municipal administrators is the cost analysis of urban cleaning service. This is one of the greatest problems because in general this service is subsidized by the municipality and consumes most of its budget.

The importance of collecting information related to the manual sanitary landfill cost during investment, construction, operation, and maintenance must be emphasized. The analysis of these costs increases productivity and provides more effective cost controls. The accounts of each public service must be dealt with separately.

It can be demonstrated that the overall cost of the manual sanitary landfill ranges between 10% and 20% of the municipal budget for cleaning services. This demonstration changes the wrong image of local administrators regarding the costs of this work. As well, the urban cleaning rate or tariff, essential for its sustainability, can be calculated more realistically optimizing quality and efficiency.

Among the factors to be considered as operational costs are:

  • Labor

  • Tools

  • Cover material

  • Maintenance

  • Indirect costs.

7.2.4 Environmental control

Initially, the ground and surface water quality will be checked monthly. After confirming that there is no contamination by the landfill, it can be checked less frequently. The parameters to be analyzed will be those required by the local or regional water pollution control authority. Appendix III.

Gas vents should be checked.

Glossary of terms

Aerobic

Relative to life or to processes which occur in presence of oxygen.

Anaerobic

A condition without free oxygen. Absence of air or oxygen for organic matter degradation.

Commercial solid waste

Waste generated in commercial facilities, such as warehouses, depots, hotels, restaurants, cafeterias, and market places.

Density of htre refuse

Relationship between the weight and the volume occupied (weight per volume unit). The density of the refuse depends on the compression. The following values can be adopted:

Dr = 150 - 300 kg/m3 = density in refuse container.
Dv = 250 - 500 kg/m3 = density in collecting vehicle.
DSW = 400 - 600 kg/m3 = density in manual sanitary landfill. 

Domestic solid waste

Waste that by its nature, composition, quantity, and volume is generated in households or in any similar dwelling. 

Field capacity

Moisture existing in a porous environment after the gravitational water has been eliminated.

Final disposal

Last operation of the urban cleaning service, by which waste reach final destination.

Industrial solid waste

Waste generated in the activities of the industrial sector as a result of production processes.

Institutional solid waste

Waste generated in educational, governmental, military, prison, and religious establishments, transportation terminals, and in office buildings, among others.

Leachate

Liquid that percolated through solid wastes, carrying dissolved or suspended materials. The infiltration of a portion of the rain is the main generator of leachate in sanitary landfills and refuse dumps. Other factors are the water content of the refuse itself, water resulting from decomposition, and groundwater infiltration.

Pathogenic solid waste

Waste that by its characteristics and composition may serve as a reservoir or vehicle of infection.

Permeability

This is defined as the velocity of the water in the soil under a unit hydraulic gradient. The dimension of permeability is that of the velocity, since the dimension is length divided by time.

Precipitation

Atmospheric water that falls on the soil in liquid or solid form, such as rain, snow, or hail. The intensity and frequency of the precipitation should be considered in the construction of the sanitary landfill to provide adequate drainage systems.

Recovery

Obtaintion of secondary materials from solid wastes, either by separation, unpacking, collection, or any other way for recycling or reuse.

Recycling

Process by which certain refuse materials are separated, collected, classified, and stored to incorporate them into the production cycle as raw material.

Refuse

Refuse is understood to mean all solid or semisolid waste that lacks value for its immediate owner except excreta of human or animal origin. Included in the same definition are rubbish, wastes, ashes, street sweepings, and industrial wastes and those from hospital establishments and market places, among others.

Reuse

Returning of a good or product to the economic flow to be used exactly in the same form as it was before, without any change in its shape or nature.

Runoff

Water that does not penetrate the soil or does so slowly and runs on the surface of the land after a rain. 

Sanitation

Control of the physical environmental factors that may have a harmful effect on man physical development, health, and survival.

Treatment

Physical, chemical, or biological transformation of solid wastes to obtain health or economic benefits, or to reduce or eliminate harmful effects to man or the environment.

Vector

Any organism that carries the disease agent from a patient or a reservoir to a healthy person.

Usefull life

Period over which the sanitary landfill will be able to receive refuse on a continuous basis. The volume to be filled is the volume of refuse deposited between the original surface of the land after preparation of the site and the final surface of the landfill. The calculation of the useful spanlife involves a series of variables that should be evaluated to achieve a technically and economically

Bibliographic references

1. AIDIS. Vigilancia de rellenos sanitarios, gestión ambiental en el caso del relleno La Feria. IV Congreso Chileno de Ingeniería
    Sanitaria y Ambiental. Concepción, Chile. November, 1985.

2. ASOCIACION DE INGENIEROS SANITARIOS DE ANTIOQUIA (AINSA). Desechos sólidos: Generación, almacenamiento,
    recolección, disposición, reciclaje. Memorias del Curso de Desechos Sólidos y Reciclaje. Medellín, Colombia. September, 1987.

3. ARMSTRONG, Christian. Confección de rellenos sanitarios con maquinaria agrícola y operación manual. Departamento de Ingeniería
    Civil, Universidad de Chile. Santiago, Chile. 1982.

4. CETESB. ORTH, María Elena de; KIYUSHI T., Celso. Aterros sanitários. Sao Paulo, Brazil. 1982.

5. CETESB. Aterro sanitário. Consejo Nacional de Desenvolvimento Urbano. Sao Paulo, Brazil. May, 1979.

6. CETESB. Manual de operaçao de resíduos sólidos No. 2, disposiçao de lixo em vala. Sao Paulo, Brazil. 1983.

7. CETESB. Recuperación de gas metano de relleno sanitario. Módulo Programa Regional OPS/EHP/CEPIS de Mejoramiento de los
    Servicios de Aseo Urbano. Ciclo: Aspectos Técnicos del Servicio de Aseo. November, 1982.

8. COLLAZOS, Héctor, and Leoncio HERNANDEZ. Relleno sanitario manual. Revista ACODAL No. 87. Bogotá, Colombia. April, 1979.

9. DEPARTAMENTO ADMINISTRATIVO DE PLANEACION DE ANTIOQUIA. Diseño relleno sanitario manual "El Chagualo", I Etapa.
    Medellín, Colombia. 1986.

10. DEPARTAMENTO ADMINISTRATIVO DE PLANEACION DE ANTIOQUIA. Guía para el diseño, construcción y operación de un
     relleno sanitario manual. Imprenta Departamental. Medellín, Colombia. 1988.

11. EMPRESAS VARIAS DE MEDELLIN. Diseño relleno sanitario "Plaza de Ferias", Informe Final. Compañía Colombiana de
      Consultores. Medellín, Colombia. 1984. 

12. ENVIRONMENTAL PROTECTION AGENCY. Sanitary landfill design and operation. U.S. Government Printing Office. Washington
      D. C., 1972.

13. FLINTOFF, Frank. Management of solid wastes in developing countries. WHO. Regional Publications. Southeast Asia. 1984.

14. FOSTER, S., et al. Determinación del riesgo de contaminación de aguas subterráneas. CEPIS/OPS/OMS. Lima, Peru. 1988.

15. HADDAD, José. Módulo de disposición final de residuos sólidos. CEPIS/HPE/OPS. Lima, Peru. 1981.

16. HANSEN, Israelem. Principios y aplicaciones del riego. Editorial Reverté, S.A., 2nd edition. Barcelona, Spain. 1973.

17. IRVINE, William. Topography. Areas and Volumes. McGraw Hill. 1975.

18. MINISTERIO DE SALUD. Decreto 2104 de 1983, Residuos Sólidos. Bogotá, Colombia.

19. OROZCO, A. Desechos sólidos. Una aproximación racional para su recolección, transporte y disposición. Universidad de Antioquia
      Medellín, Colombia. 1980.

20. PENIDO, José. Recuperación semi-mecanizada de materiales. Aspectos técnicos del servicio de aseo. Programa Regional
     OPS/HPE/CEPIS de Mejoramiento de los Servicios de Aseo Urbano. Lima, Peru. 1982.

21. RIVERO, F. J. Aterro sanitário. Simposio Paranaense de Destinaçao Final das Resíduos Sólidos Urbanos em Curitiba. Sao Paulo,
    Brazil. 1983.

22. SAKURAI, K. Cálculo del volumen del relleno. Technical note. CEPIS. Lima, Peru. 1980.

23. SAKURAI, K. Diseño de zanja de intercepción. Technical note. CEPIS. Lima, Peru. 1980.

24. SAKURAI, K. Disposición final de residuos sólidos. CEPIS. Lima, Peru. 1980.

25. SECRETARIA DE DESARROLLO URBANO Y ECOLOGIA, et al. Programa estatal de control de residuos sólidos municipales.
      Talleres gráficos del Banco Nacional de Obras y Servicios Públicos. Mexico. June, 1985.

26. SECRETARIA DE SALUBRIDAD Y ASISTENCIA. Instructivo sanitario. Ed. Limusa. Mexico. 1980.

27. STECH, Pedro José, et al. Aterro sanitário em valas. Divisao de Resíduos Sólidos Domésticos. Sao Paulo, Brazil.

28. UNIVERSIDAD DE ANTIOQUIA. Facultad de Salud Pública. Estudio de aseo urbano (diagnóstico y proyecto). Municipio de
     Apartado. CORPOURABA. Medellín, Colombia. 1981.

ANNEXES

ANNEX I
EXAMPLES FOR THE DESIGN
OF MANUAL SANITARY LANDFILLS

EXAMPLE 1. Calculation of Solid Waste Production per Day

Find the daily quantity of solid wastes generated by 40,000 population; the rate per person is estimated at 0.5 kg/person/day.

SWp = Pop x ppc                                                    [5-3]

SWp = 40,000 x 0.5 = 20,000 kg/day = 20 tons/day

If the landfill operates six days a week, how much refuse should be disposed of each workday?

SWp  =   7 x 20   =  23.3. tons/day
                   6

EXAMPLE 2. Calculation of the Required Landfill Volume

The municipal administration of the city of Hierro is going to construct a sanitary landfill. It is necessary to know how much refuse is produced, the landfill volume, and the area required to start the selection of the site. The following information is available:

  • Urban population: 30,000

  • Growth rate: 2.6% annually

  • Volume of solid wastes collected measured in the collection vehicle: 252 m3/week

  • Service coverage: 90%

  • Solid waste density:

- collection vehicle (without compaction) 300 kg/m3

- recently compacted in the landfill 450 kg/m3

- stabilized in the landfill 600 kg/m3

SOLUTION:

To handle the information more easily, use Table 5.3 where the results are summarized. The number of column referred to are those of that table (see it at the end of the problem).

A. Population Projection:

Geometric growth will be assumed for calculating population projections (see equation 5-1, column 1, for estimates of the needs for the next 15 years).

          Year

PE = P1 (1 + r)n

P1 =                                              = 30,000        1
P2 = 30,000 (1 + 0.026)1                 = 30,800        2
P3 = 30,000 (1 + 0.026)2                 = 31,580        3
... = ...                                           = ...              ...
P15=30,000 (1 + 0.026)14                = 42,972       15

B. Production per Capita:

The production per capita is estimated using equation 5-2.

PPC  =  SWc/week     =            252m3/week x 300 kg/m3
            Pop x 7 x Cos               30,000 inhab x 7 days/week x 0.9

PPC1 = 0.4 kg/person/day (first year)

It is estimated that the production per capita increases 1% annually; thus, for the second and third years it will be:

PPC2 = PPC1 + (1%) = 0.4 x (1.01)
PPC2 = 0.404 kg/pop./day
PPC3 = PPC2 + (1%) = 0.404 x (1.01)
PPC3 = 0.408

PPC can be calculated in this way for the succeeding years (see column 2).

C. Quantity of Solid Wastes:

  • Daily production is calculated using equation 5-3, column 3.

SWp = Pop x PPC = 30,000 inhab. x 0.4        kg 
                                                             inhab./day

SWp = 12,000 kg/day

  • Annual production is calculated by multiplying the daily production of solid wastes by the 365 days in the year (see column 4).

SWp x  365 days    x   12,000 kg  x  365 days  x  1 ton   =   4,380 tons/year
               year                  day              year          1,000 kg

D. Volume of Solid Wastes:

  • Annual compacted volume (equation 5-5, column 7), with a density of 450 kg/m3 because of the manual operation.

V(annual comp.)  =   SWp   x  365  =   12,000 kg/day  x   365 days/year
                               Dsw                      450 kg/m3

= 9,733 m3/year

  • Annual stabilized volume (equation 5-5, column 8), with an estimated density of 600 kg/m3 to calculate landfill volume.

V(annual.comp.) =   SWp    x  365   =   12,000 kg/day     x  365 days/year
                              Dsw                        600 kg/m3

= 7,300 m3/year

  • Volume of the sanitary landfill.

The volume of the sanitary landfill consists of the solid waste and cover material volumes. In this case the cover material volume is estimated at 20% of the refuse volume (see equation 5-6, column 9):

VL = Vannual x CM = 7,300 m3/year x 1.20

      = 8,760 m3/year

It should be noted that column 10 presents the landfill volume accumulated annually, which makes possible to calculate the lifespan of the landfill by comparing it with the volumetric capacity of the site.

E. Calculation of the Area Required

  • Calculation of the area to be filled, using equation 5-8. If an average depth of six meters is assumed, the area required will be:

. The first year

AL   =   VL    =   8,760 m3/year      =  1,460 m2 for the 1st year (0.146 ha1)
            HL               6M

 

. The fifth year

AL47,090 m3    =  7,848 m2 (0.78 ha)
               6 m

In column 11, the area required for two, three, or more years is included based on data accumulated in column 10.

  • Calculation of total area considering an increase factor for additional areas (see column 12). In this case 30% is assumed, i.e.:

. For the first year

AT = F x AL = 1.30 x 1,460 m2 = 1,898 m2 (0.19 ha)

. For five years of lifespan

AT = 1.3 x 7,848 m2 = 10,203 m2 (1.02 ha*)

EXAMPLE 3. Calculation of the Trench Volume

In a municipality there is a flat land available for constructing a manual sanitary landfill by the trench method. To open the trenches, a backhoe with an an excavating capacity of 14 m3 per hour will be rented.

  • What are the volume and dimensions of a trench to last 60 days?

  • For how many days must the machinery be rented?

Basic information:

  • Population to be served 30,000 persons

  • PPC 0.4 kg/persons/day

  • Collection service coverage 90% of the population

SOLUTION:

  • Quantity of solid wastes produced

SWp = Pop x PPC = 30,000 inhab x 0.4      kg     =   12,000  kg
                                                              day              day

  • Quantity of SW collected

SWc = SWp x Css =   12,000 kg   x 0.90  =   10,800 kg
                                     day                             day

  • Trench volume

If the cover material is estimated at 20%, lifespan at 60 days, and the density at 500 kg/m3, then:

Table I.1

Year

Population
(hab)

PPC
kg/
hab-day

Quantity of wastes

Volume of solid wastes

Required area

Daily
(kg)

Anual
(ton)

Acumulated

Compacted

Stabilized Anual
(M3)

Landfill

Landfill
Ahs
(m2)

Total
At
(m2)

Daily
(kg)

Anual
(m3)

(SW + CM
Anual

Acum.
(m3)

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
1 30,000 0.400 12,000 4,380 4,380 26.7 9,733 7,300 8,760 8,760 1,460 1,898
2 30,800 0.404 12,443 4,542 8,922 27.6 10,093 7,570 9,084 17,844 2,974 3,866
3 31,580 0.408 12,885 4,703 13,625 28.6 10,451 7,838 9,406 27,250 4,542 5,904
4 32,401 0.412 13,349 4,872 18,497 29.7 10,827 8,120 9,744 36,994 6,166 8,015
5 33,244 0.416 13,830 5,048 23,545 30.7 11,218 8,413 10,096 47,090 7,848 10,203
6 34,108 0.420 14,325 5,229 28,774 31.8 11,620 8,715 10,458 57,548 9,591 12,469
7 34,995 0.425 14,873 5,429 34,203 33.1 12,064 9,048 10,858 68,406 11,401 14,821
8 35,905 0.429 15,403 5,622 39,825 34.2 12,493 9,370 11,244 79,650 13,275 17,258
9 36,638 0.433 15,864 5,790 45,615 35.2 12,868 9,651 11,581 91,231 15,205 19,767
10 37,796 0.437 16,517 6,029 51,644 36.7 13,398 10,048 12,057 103,288 17,215 22,379
11 38,779 0.442 17,140 6,256 57,900 38.1 13,903 10,427 12,512 115,800 19,300 25,379
12 39,787 0.446 17,745 6,477 64,377 39.4 14,393 10,795 12,954 128,754 21,459 27,897
13 40,822 0.451 18,411 6,720 71,097 40.9 14,933 11,200 13,440 142,194 23,699 30,809
14 41`,883 0.455 19,057 6,956 78,053 42.3 15,457 11,593 13,911 156,105 26,018 33,823
15 42,972 0.460 19,767 7,215 85,268 43.9 16,033 12,025 14,430 170,535 28,422 36,949

(6) SW production in a week is disposed of at SL in days "x"of collection (7 days/xworking days)
(9) Sanitary landfill volume = solid wastes + soil (20%) general average
(11) ARS = VrRS/HRS (ARS = Filling area
(12) AT  =  F ARS   F (factor for additional area)
        Area/hab 0.0063 (m2/hab) real

Waste density

-Vehicle         -    300 kg/m3
- compacted   -   450 kg/m3
-Stabilized       -  600 kg/m3

VD  =  t  x  SWc   x  CM   =  60 days x  10,800 kg/day x 1.2    =  1,555 m3
                   Dsw                                500 kg/m3

Thus, 26 m3 must be excavated to dispose of the solid wastes of one day.

  • Trench dimensions

hz = depth = 3 m
w = width = 6 m
l = length = ?

l  =   VD       =   1,555   =   86.4 m
        hD x w       3 x 6

Therefore:

hD = 3 m
w = 6 m
l = 86 m

  • Machinery time

texc =   Vd    =         1,553 m3                    =   13.9 = 14 days
        R X WD      14 m3/hour x 8 hours/day

This means that the excavation of the trench will take 14 days. It is convenient that at least five days before filling completely the trench, the equipment should be rented to open a new trench; the machinery should be properly scheduled.

EXAMPLE 4. Calculation of the Lifespan of the Site

Assume a flat site of 2.3 ha. How long will be the lifespan if trenches of 86 m long are used as described previously?

SOLUTION:

For complementary works, 0.3 ha are reserved. Two hectares are left to filling wastes and each trench is separated 2.00 m from the other, then:

  • ÁREA DE CIRCULACIÓN = CIRCULATION AREA

Since each trench occupies six m, plus two m of separation between them, i.e. eight m, the number of trenches in one hectare will be:

Number of trenches = 100/8 = 12.5 or 12

If each trench lasts two months, 12 trenches will last two years, and the total area required for the landfill will be 2.5 ha to have a lifespan of five years.

The trench method can be combined with the area method, i.e. raise the landfill a few meters above the original surface using cover material from the excavation (80% in case of the example) to use the land more efficiently.

EXAMPLE 5. Example of Volume Calculation for the Area Method

Assume a manual sanitary landfill project on an abandoned road which sections similar to those shown in the following figure and with horizontal axes at intervals of 100 m, yielding an average height of eight m.

Gra85.gif (3386 bytes)

The landfill will have a width "w" of six m at the base, a variable slope in each section, and the following data:

Abscissa (m) 0 100 200 300 400
Cross section (m2) A1 A2 A3 A4 A5
Slope (n) 1:2 1:1 1:3 1:1 1:2
Average height in axis "c" 8 M

The larger base of the trapezoid will be:

Width of the landfill surface = (w + nc + nc) meters
        at each abscissa (w = 6) = [6 + 2(nc)] meters

Therefore, the cross section area at every abscissa (trapezoid) will be:

   =   [6  +   2(nc)]  +  6     x c
                  2

   =  (6 + nc) x c

Area in 0 = (6 + 2 x 8) x 8 = 176 m2         A1
100 = (6 + 1 x 8) x 8 = 112 m2                A2
200 = (6 + 3 x 8) x 8 = 240 m2                A3
300 = (6 + 1 x 8) x 8 = 112 m2                A4
400 = (6 + 2 x 8) x 8 = 176 m2                A5

 

Applying the Simpson rule (equation [5-14]):

100

 

Volume =           [176 + 176 + 2(240) + 4(112 + 112)]
                   3

            = 57,600 m3

EXAMPLE 6. Volume Calculation Using the Prismoid Rule

The figure shows a manual sanitary landfill project in a trench with the following data:

i. length of the trench 100 m
ii. width at the lower base 6 m
iii. initial depth 8 m
iv. final depth 5 m
v. slopes 1:1

Calculate the landfill volume using the prismoid formula.

SOLUTION:

i. Cross section A1:

base width = 6 m
total width = (6 + 2c) m
depth in the axis "c" = 8 m

Therefore:

total width = (6 + 16) m
                = 22 m

 

ii. Cross section A2:

base width = 6 m
total width = (6 + 2c)
depth in the axis "c" = 5 m

Therefore:

total width = (6 + 10) m
                = 16 m

iii. Average cross section "M":

base width                 = 6 m
total width                  = (6 + 2c) m
depth of axis "c"        = average depth in A1 and A2
                                          = ½ (8 + 5) m
                               = 6.5 m

Therefore:

total width                 = 6 + 13 m

  = 19 m = average of the widths of A1 and A2

iv. Area of the sections and trapezoids

A1 = ½ (6 + 22) x 8 = 112 m2

A2 = ½ (6 + 16) x 5 = 55 m2

M = ½ (6 + 19) x 6.5 = 81.25 m2

 

v. Volume =    100     [112 + 55 + 4(81.25)]
                        6

     = 8,200 m3

EXAMPLE 7. Volume based on the Extreme Areas

Using the same data as in the previous example we have:

A1 = 112 m2
A2 = 55 m2
d = 100 m

Therefore the volume will be:

Volume =      (112 +   55)     x    100 (m3)
                            2

  = 8,350 m3

It should be noted that the result is approximate.

EXAMPLE 8. Volume Based on a Graticule

The figure shows a small part of the graticule. The area should be filled to 100.0 m height to obtain the final surface. The slope should be vertical.

The solid with a base in each square of the graticule is a vertical truncated prism, i.e. a prism which bases are not parallel.-

SUPERFICIE FINAL = FINAL SURFACE

- Volume of each prism = average height x base area

The average height of each truncated prism below the elevation of 100.0 m is:

Prism 1, (9 + 7 + 8 + 8) ¸ 4 = 8 m
Prism 2, (7 + 6 + 8 + 7) ¸ 4 = 7 m
Prism 3, (8 + 8 + 7 + 9) ¸ 4 = 8 m
Prism 4, (8 + 7 + 9 + 8) ¸ 4 = 8 m

Base area of each truncated prism = 10 x 10 = 100 m2

Therefore the volumes are as follows:

For Prism 1, 100 x 8 =      800 m3
For Prism 2, 100 x 7 =     700 m3
For Prism 3, 100 x 8 =     800 m3
For Prism 4, 100 x 8 =     800 m3

Total volume available = 3,100 m3

The volume can also be found in the following way:

    Volume = average height of the landfill x total area

The average height of the landfill is the average of the average heights of the prisms and not the height mean at the level points.

Average landfill height = (8 + 7 + 8 + 8) ¸ 4 = 7.75 m

Total area = 20 x 20 = 400 m2

where: total volume = 7.75 x 400 = 3,100 m3

When analyzing this process, it can be noticed that level A was used only once to find the average height of the landfill, level B twice, and level E a total of four times. As a result, the average height, thus, the volume can be found more easily by tabulating the operations as in Table I.2.

The heights at the level points are tabulated in column 2 and the number of times that each one is used is entered in column 3; column 4 contains the products of the numbers in columns 2 and 3; the average height is found by dividing the sum of column 4 by that of column 3.

TABLE I.2

Point in the network

Height to the project level

Number of times used

Product

A

9

1

9

B

7

2

14

C

6

1

6

D

8

2

16

E

8

4

32

F

7

2

14

G

7

1

7

H

9

2

18

I

8

1

8

 

Sum

16

124

Average height of the landfill = 124/16 m
                                         = 7.75 m, as previously.

EXAMPLE 9. Volume Based on Contour Lines

If we take the volume between the contour lines of 105 and 115 m, which areas may be found by any of the methods described in Annex II, the mean section will be enclosed by the curve of 110 m, which area may also be found using any method. Then, the prismoid volume will be:

Volume =     2h  [A1 + 4 A2 + A3]
                    6

As well, the volume between the contour lines for 115 m and 125 m will be:

Volume =    2h    [A3 + 4 A4 + A5]
                    6

The sum of these results will give the volume between levels 105 m and 125 m.2h 2h

Volume =   2h  [A1 + 4 A2 + A3] +   2h [A3 + 4 A4 + A5 ]
                  6                                    6

  =   h    [A1 + A5 + 2 A3 + 4 (A2 + A4)]
     3

which is the total volume given by Simpson rule.

Procedure:

1. A site plan is prepared on a scale of 1:250, 1:500, or 1:1000, depending on the size of the plot, with contour lines at intervals of 1.0 meter.

2. The land topography is drawn after the initial preparation and the final landfill topography, providing the surface slope (2% to 5%) to facilitate rainwater drainage.

3. A horizontal axis is traced at a convenient point and the land is cut by the horizontal planes A1, A2, A3, ..., An, with a height "h" between them. For rapid estimations, a value of 3, 5, 10, or 20 m is recommended, depending on the size of the land depression. For final estimation, a value of 1.0 meter is used.

4. The areas A1, A2, A3, ..., An are calculated using the initial and final topographical maps, and those of the landfill partial filling.

5. The site volumetric capacity is calculated with the equations 5-16, 5-17, or 5-18, taking the areas calculated in point 4.

EXAMPLE 10. Calculation and Design of the Daily Cell

For the same population of 30,000 persons, with a production of 12 tons/day and a coverage of 90%, calculate and design the daily cell in a manual sanitary landfill that operates six days a week.

SOLUTION:

A. The quantity of refuse in the manual sanitary landfill is:

        SWL = qq SWp x 7 = 12,000 kg/day x 7  = 14,000 kg/workday
                           x                             

However, as it is known, only 90% of solid wastes will actually arrive at the landfill; therefore:

SW'L = 14,000  _   kg___ x 0.90 = 12,600  _  kg____
                       workday                             workday

B. Cell volume, determined using Equation 1-21. The cover material is estimated at 20% of the volume of the recently compacted refuse, with a density of 450 kg/m3 in this case.

SW'L 12,600 kg/day

Vc =__  _  x CM = _______    x 1.20
        Dsw              450 kg/day

= 33.6 m3/workday

C. Cell dimensions

. The area, considering that the height is limited to one meters, is:

Ac =   __Vc  = 33.6 m3 = 33.6 m2/workday
              hc         1m

. The length or growth of the cell will depend on the normal variations of the refuse, while the width in this case can be maintained at three meters; thus:

l =  _Ac__  = _33.6m2 = 11.2 m/day
        w                3m

Therefore:

l = 11.2 m, w = 3 m, hc = 1.0 m

It is also possible to choose a square section:

l = 5.8 m, w = 5.8 m, hc = 1.0 m

EXAMPLE 11. Labor Force Calculation

For 12,600 kg/day, in each of the six days of operation of the sanitary landfill, with a workday of eight hours, and assuming six hours of effective work per day, how much labor is required, assuming the efficiency proposed in Chapter 5?

SOLUTION:

Volume of the daily cell = solid waste volume + cover material (20%)

Volume of solid wastes =  _12,600 kg/day = 28 m3 /day
                                           450 kg/m

Volume of earth = _28m3   x 0.20 = 5.6 m /day
                              day

Volume of the daily cell = (28 + 5.6) m3 /day

      = 33.6 m3 /day (hc = 1.0 m)

According to the different operations and efficiencies we have:

OPERATION

EFFICIENCY

MAN PER DAY

Waste movement 12.6 ton/day    x       1
0.95 ton/manhr      6 hrs.
 
Waste compaction

33.6 m3                   x 1
20 m3/man-hr         6 hrs.

0.28

Soil movement

5.6 m3                      x 1
0.37 m3/man-hr      6 hrs.

2.52

Cell compaction

33.6 m3                      x 1
(20) m3/man-hr       6 hrs.

0.28

 

(TOTAL No. OF MEN)

5.29

SANITARY LANDFILL

12.6 ton/day 5 men

2.5 ton/man-day

This means that this sanitary landfill could be operated with a total of approximately five men (performance of 2.5 tons/man-day). As it has been observed, the number of men depends on how near are the working face and cover material, on weather conditions (rainy season), and mainly on quantity variations of the refuse received at the landfill.

It is worth noting that supervision plays a primary role in the proper operation of the sanitary landfill as well as in the worker effectiveness.

EXAMPLE 12. Cost Calculation

The objective is to determine the operation and maintenance costs of a manual sanitary landfill and to establish, in addition, the user fee. The landfill, with an estimated lifespan of nine years, receives 12 tons of refuse daily (Monday through Saturday). The following information is available for the analysis:

1. Capital cost

. Study and design (with the support of an advisory entity) $ 4,000
. Land acquisition                                                               8,000
. Land preparation and complementary works                        7,000

TOTAL CAPITAL COSTS                                                 $19,000

2. Operation and maintenance expenses

. Labor

It has been determined that four workers are required, whose wages are $90.00 per month, with a social benefit factor of 1.6, and 20% of the supervisor wages ($150/month).

. Other operational expenses

Materials (rock for drains, wire, tools), $300/year

Rental of a caterpillar tractor (excavations and improvement of internal roads), 20 hours twice a year at $20/hour.

SOLUTION TO THE PROBLEM:

1. Calculation of unit cost of capital recovery (Uc) for nine years at an annual interest rate of 20%.

Using equations 5-30 and 5-31:

Cc = Ctotal (FRC) = Ctotal   _____i____

                                            1 - _1__
                                                 (1+i)n

Cc = 19,000 x ___0.20
                    1 - (1/1.2)9

Cc = 19,000 x 0.248079 = $4,713.5 per year

. The annual yield would be:

R = 313 __days x 12 __tons   = 3,756 __tons
                 year              day                  year

Then:

(Uc) = annual amount of capital recovery =   _____  $ 4,713.5 per year
             tons disposed of per year                                3,756 tons/year

= $1.25 per year

2. Calculation of the unit cost of operation and maintenance (Uco)

2.1 Labor cost (equation 5-32)

. Direct = 4 x 12 x 90 x 1.6 =                     $6,912 per year
. Indirect = (1 x 12 x 150 x 1.6) x 0.2           $ 576 per year
Subtotal for labor                                       $7,488 per year

 

2.2 Other operation expenses (Ct + Cm)

. Materials and tools                                      $310 per year
. Equipment rental = (20 x 20) 2 =                   $800 per year
Subtotal for other operation expenses           $1,100 per year

TOTAL OPERATION AND MAINTENANCE
COSTS (Cao)                                              $8,588 per year

(Uco) = Total operation and maintenance costs
                      Tons disposed of per year

= $8,588 per year = $2.29 per ton
3,756 tons/year

The total cost per unit would be: Cut = $3.54 per ton.

3. Calculation of fees

3.1 Fee with capital recovery plus operation and maintenance costs

Cost of providing the service when a loan is received and the debt service must be paid through fees

. Unit cost of capital recovery (per ton)     =     $1.25 per ton
. Unit cost of operation and maintenance =     $2.29 per ton

TOTAL TO BE RECOVERED                                             $3.54 per ton

Quantity of refuse

= 12 tons  x 26 days   = 312 tons

collected per month         day           month          month

Monthly cost for tons

= 312 tons  x $3.54 per ton

final disposal          month

= $1,104.5 per month

Now if each household (user) has an average of five persons who produce 0.5 kg/day of refuse, taking into account that 12 tons/day are collected six days a week, the daily production of refuse is as follows:

Daily production kg
                               = 12,000 x kg___ x __  _6 10.250 kg/day
of refuse                                    day                7

Then the number of users is determined as follows:

No. of users  =    10,250 kg/day           = 4,100 households (users)
                        0.5 kg         x     5 inhab
                            inhab/day      household

Thus:

The monthly fee = $1,104.5  per month =     $0.269 per user per month per user 4,100 users
                           4,100 users

3.2 Fee based on operation and maintenance costs

Cost of providing the service when the debt service is not included in the fee (only the operation and maintenance costs are considered).

Operation and maintenance costs per unit = $2.29 per ton

Monthly cost per       = 312 tons     x $2.29 per ton
final disposal                    month

                              = $714.5 per month

Monthly fee            =   $714.5 per month    =   $0.174 per user per month
per user                        4,100 users

4. Annual budget allotment from the municipality

The municipal administration should allot from the annual budget an amount equivalent to:

. Annual amount for debt payment                      = $4,713
. Annual operation and maintenance costs         = $8,588

TOTAL ANNUAL ALLOTMENT                           = $13,301

ANNEX II
CONCEPTS OF DRAWING AND TOPOGRAPHY

1. Drawing to Scale

This is a measure relationship that represents real objects in exact proportions, in appropriate sizes, to facilitate the work of planners and builders.

"Drawing to scale" can be defined as the exact representation of something in a reduced size.

The establishment of proportional measures (ratios) that represent natural objects on appropriate scales, or the representation of the system chosen for a map scale, has the following nomenclature:

1:1 (one to one) 1:50 (one to fifty)
1:2 (one to two) 1:100 (one to one hundred)
1:5 (one to five) 1:200 (one to two hundred)
1:25 (one to twenty-five) 1:1,000 (one to one thousand)

The first number represents the unit and the second, the number by which it has been divided to generate smaller proportional dimensions.

Examples:

Scale 1:20 Every meter in the field is equal to 1/20 m (0.05 m or 5 cm) on the map.

Scale 1:50 Every meter in the field is equal to 1/50 m (0.02 m = 2 cm) on the map.

Scale 1:100 Every meter in the field is equal to 1/100 m (0.01 m = 1 cm) on the map.

 

2. DRAWING AND MEASUREMENT OF LINES

  • Stakes are placed at the ends of the line to be measured and poles or markers are placed over them.

  • The observer should be approximately four meters behind one of the poles or markers so that he could see both poles fused into one.

  • Then, two persons (chainmen) will take the ends of the tape measure; the one who is behind will place the beginning of the tape at the base of the first pole and the other one in the front will stretch the tape along the line fixed by the two poles, following the indications of the observer placed behind the first pole; the one who is in the front will place wire hooks at the end of every tape length so that, when making the following measurement, the one at the back places the end of the tape he is carrying on the hook left by the other one. Figure II.1.

Observador= Observer
Jalón= Pole
Visual= Visual
Gancho+ Hook
Cadenero de atrás= Chainman behind
Cadenero de adelante= Chainman in the front
Cinta métrica= tape measure
Jalón o baliza= Pole
Cinta= Tape measure
Estaca= Stake

This operation will be repeated as many times as necessary until reaching the other end.

3. Drawing a Perpendicular from a Point outside the Alignment

A person should be placed on the alignment with his arms extended, looking toward the point where the perpendicular is going to be drawn, making sure that his arms point toward each end of the alignment. Then he closes his arms and extends them forward; the perpendicular point should be in the direction indicated by the arms.

If a surveyor's square is available (Figure II.2), the observation is made simply by using the grooves.

  • LOCALIZACIÓN = LOCATION
  • COMPROBACION = CHECKING
  • PUNTO FUERA DEL ALINEAMIENTO = POINT OUTSIDE THE ALIGNMENT
  • ALINEAMIENTO = ALIGNMENT
  • VISUAL= VISUAL
  • When CB is equal to BD the point "P" will be half the distance of CD

- (ÁNGULO RECTO)= (RIGHT ANGLE)

FIGURE II.2
Drawing a Perpendicular

4. Area calculation

The area of any figure that has been surveyed can be calculated based on:

. Field notes
. Map drawn

4.1 Areas Deduced from Field Notes

- Surveys with tape measure

In a survey with tape measure, the area is subdivided into triangles; the three sides are measured and the area of each is found by the formula:

Area =  wpe1.gif (1121 bytes)

where:

s = half of the perimeter =           a + b + c
                                                    2

 

a, b, and c =triangle sides.

FIGURE II.3
Land Survey with Tape

Example 1:

Figure II.3 shows a simple survey with a tape measure, comprised by the triangle PQR with the following sides:

PQ = 60.0 m
QR = 104.6 m
RP = 70.0 m

The area of PQR is found as follows:

a. In the angle PQR: PQ = r = 60.0 m
                               QR = p = 104.6 m
                                RP = q = 70.0 m

The perimeter of PQR            = 234.6 m

and thus, the semiperimeter s = 117.3 m

b.                  s - r = 57.3

s -p = 12.7

s - q = 47.3

Checking               = 117.3 = s

 

c. Area of the triangle PQR = wpe2.gif (1171 bytes)

wpe3.gif (1269 bytes)

=   2,009.3 m2

The boundaries were found by means of perpendiculars from the alignments.

In Figure II.3 the area between the survey line and the stream is formed by several triangles and trapezoids, which areas can be calculated separately as follows:

On the line RQ:

Area of triangle (1) = ½ x 19 x 4                        =    38.0 m2
Area of trapezoid (2) = ½ ( 4+8 ) x (38 - 19)       = 114.0 m2
Area of trapezoid (3) = ½ (8 + 4.5) x (55 - 38)    = 106.25 m2
Area of rectangle (4) = 4.5 x (72 - 55)                 = 76.5 m2
Area of trapezoid (5) = ½ (4.5 + 7) x (87 - 72)     = 86.25 m2
Area of triangle (6) = ½ (104.6 - 87) x 7               = 61.6 m2

                                                                        482.6 m2

The area between the line PQ and the road is also divided into triangles and trapezoids. In this case, however, the perpendiculars are at regular intervals of 10 meters.

If each perpendicular is called Y, the area between any two perpendiculars is calculated as follows:

Area between theabscissa 20 and 30 = ½(Y20 + Y30) x 10

Thus:

Total area = ½ (Y0 + Y10) x 10 + ½ (Y10 + Y20) x 10

                             + ½ (Y20 + Y30) x 10 + ... + ½ (Y50 + Y60) x 10

= ½ x 10 (Y0 + Y10 + Y10 + Y20 + Y20 + Y30+...+ Y50 + Y60)

= ½ x 10 (Y0 + Y60 + 2Y10 + 2Y20 + 2Y30 + 2Y40 + 2Y50)

= 10 (4 + 4 + Y10 + Y20 + Y30 + Y40 + Y50)
            2

This is the trapezoid rule that is usually stated as follows:

Area = width of the band x (average of the first and last perpendicular + total of the others)

d. In Figure II.3 the area is calculated as follows:

Area = 10  (4 = 4 + 4.5 + 5.1 + 6.5 + 6.3 + 5.1)
                    2

= 315.0 m2

The area can be calculated more precisely with Simpson rule, which can be stated as follows:

Area = 1/3 of the piece width (first + last perpendicular + twice the sum of the odd perpendiculars + four times the sum of the even perpendiculars).

Note: (i) There should be an odd number of perpendiculars.
         (ii) The perpendiculars should be at regular intervals.

Using Simpson rule, the area between the line PQ and the road is:

Area = 1 [Y0 + Y60 + 2 (Y20 + Y40) + 4 (Y10 + Y30 + Y50)]
            3

10 [4 + 4 + 2(5.1 + 6.3) + 4(4.5 + 6.5 + 5.1)]
     3

10 [8 + 2(11.4) + 4(16.1)]
     3

= 317.3m2

e. Finally, the area between the alignment PR and the forest is calculated. The area should be calculated by the trapezoid rule since there is an even number of perpendiculars between R and P at regular intervals of 10 meters.

The area beween the abscissa 70 and 74 is calculated separately. The area between PR and the forest will be:

Area = 10 ( 3 + 2.5 + 8 + 10 + 9.5 + 9.2 + 7.1 + 4.5 )
                      2

= 510.5 + 5.0

= 515.5 m2

Total area surveyed = 2,009.3 + 482.6 + 317.3 + 515.5
                             = 3,324.7 m2

4.2 Calculation of Areas Based on the Map

Various methods are available to find the area of a given figure on a map. The areas between the contour lines can be measured graphically with a planimeter, using the Simpson rule or the trapezoid rule. The last three methods, which are easy to apply in these cases, are described below.

. Mechanically with a planimeter

The area of any irregular figure can be calculated on a map using the mechanical device for measuring areas, known as the planimeter.

. Graphical calculation of the area

A sheet of transparent paper with squares or divided into millimeters is placed over the map, the squares are counted, and the area is deduced.

. By Simpson rule or trapezoid rule

The area is subdivided into several bands of equal width, the lengths of the corresponding perpendiculars are measured, and any of the two rules is used.

Example 2:

Figure II.4 shows an area of irregular form in a plane at a scale 1:500. Calculate the upper area of the landfill by the graphic methods and by the Simpson rule and trapezoid rule.

Calculation of the Aarea by the Graphic Method

SOLUTION:

 

a. Graphic Method

The transparent squared paper overlaid on the plane has 5 mm squares therefore, every square represents a piece of land of (5 x 500 x 5 x 500) mm2 = 25 x 0.25 m2.

= 6.25 m2

Area = (6.25 x number of squares) m2
        = 6.25 x 89
        = 556.25 m2

b. Simpson Rule and Trapezoid Rule

Assume that the straight line is marked xx as the baseline and every second vertical line on the square paper as a perpendicular "Ÿ" (a total of seven). The lengths of these perpendiculars, (Y1 to Y7), read to scale, are 16 m, 18.3 m, 20 m, 22.5 m, 23.8 m, 15.3 m, and 0 m, and they are separated 5 m throughout the baseline.

By the Simpson rule:

Area = 5   [16 + 0 + 2(20 + 23.8) + 4(18.3 + 22.5 +15.3)]
            3

= 546.67 m2

By the trapezoid rule

Area = 5 ( 16 + 0 ) + 18.3 + 20 + 22.5 + 23.8 + 15.3
                   2

= 539.50 m2

 

ANNEX III
MONITORING WATER QUALITY

The process of decomposition that occurs in solid wastes generates liquids, gases, and intermediate products. Some are held in the pores of the soil, while others are carried away or dissolved by the liquids passing through the layers of soil and refuse. Part of the planning of a sanitary landfill includes a series of measures to prevent potential risks to the quality of the environment, before, during its execution, and after its closure.

The manual sanitary landfill, although it is a small project, should include among the environmental controls at least the monitoring of water quality to early detect groundwater pollution in the surrounding area.

Small populations generally produce just domestic wastes, with some exceptions. It is important, thus, to point out that the requirements of the manual sanitary landfill regarding the imperviousness of the soil base and side walls are minimal if it has a clayey lime soil and the height above the water table is more than one meter. Given these conditions, the likehood of grounwater or surface water pollution by leachate is significantly reduced.

In areas with little rain, minimal amount of percolated liquid is expected.

Laboratory tests of nearby underground and surface waters samples can be carried out frequently during the first months and less often once the results are constant.

The analysis of the following parameters should be considered:

  • pH

  • Chemical oxygen demand (COD), mg/l

  • Biochemical oxygen demand (BOD), mg/l

  • Nitrate, mg/l

  • Chlorides, mg/l

  • Sulfates, mg/l

  • Total count of colonies, colonies/ml

  • Conductivity, m mho/cm.

The percolated liquid should also be analyzed.

For groundwater sampling, if the water table is next to the surface, wells can be dug manually. Depending on the type of soil, measures should be taken to avoid slides during the work. The wells should be located at least five meters away from the landfill area and drainage of the percolated liquid. Once the water table is found, granular material should be placed at the bottom and an eight-inch pipe should be installed to allow the insertion of a sampling container. The rest of the well is then covered with the soil that had been excavated.

FIGURE III.1
Well for Groundwater Monitoring

At sites where the water table is more than three meters below the surface, it is recommended to take the sample from the nearest well downstream.

ANNEX IV
DRAFT MUNICIPAL ACT

 

"By means of which the construction of the sanitary landfill is authorized, as well as the measures for its construction, operation, and maintenance and other provisions."

The Municipal Council of ... by the authority conferred on it by Article ... of the National Constitution and Law ...

WHEREAS

(considerations that the Council deems appropriate)

HEREBY ADOPTS THE FOLLOWING ARTICLES:

Article 1. The current dump for municipal refuse, located in ... and the other dumps within the municipal jurisdiction must be closed

Article 2. To implement the provisions of the previous article, the Office of ... will proceed:

- To carry out a program for extermination of rodents and arthropods, for which it should, whenever possible, seek the collaboration of the Health Service, Division of Environmental Sanitation.

- To cover the current refuse dump with a soil layer of 0.20 m to 0.30 m thick, tamping it down to avoid t fires and smokes.

- To fence the access to the current dump to prevent the entry of persons and animals.

- To place a visible sign indicating that the disposal of wastes on the dump is prohibited and the penalties for noncompliance. To inform about the sanitary landfill by radio, local newspapers, or other means.

Article 3. The construction of the sanitary landfill "Name" with its entire complementary works is authorized, it will occupy the land belonging to the Municipality, located in ... and approved by the Health Service for this purpose.

Article 4. The Office of ... shall be responsible for the construction, operation, and administration of the sanitary landfill, adhering in all cases to the standards and technical specifications contained in the final report of the design of the sanitary landfill, prepared by ... which for all effects is considered an integral part of this Act; to the recommendations of the Health Service; to the Decree ... of the Ministry of Health; and to the specific provisions of the present Act.

Article 5. The lot of the sanitary landfill should be fenced with ... to facilitate its identification and to prevent access of extraneous persons. Moreover, trees should be planted in the perimeter to provide isolation and better landscape.

Article 6. A sign shall be placed near the entrance to the landfill to inform about the project and the participating organizations.

Article 7. The sanitary landfill shall operate with the following staff: one (1) supervisor and ... ( ) workers.

Note: If those positions do not exist, the possibility of creating them should be studied.

Article 8. The post of Supervisor of Sanitation is created in the Office of .... with a monthly salary of $ ... charged to item ... of the municipal budget.

The post of Supervisor of Sanitation should be held by a technician in sanitation or a promoter of sanitation, with experience.

The Supervisor shall be responsible for the management of urban cleaning services, including the collection, transportation, and final disposal of the solid wastes, assuring the proper provision of this public service.

Article 9. The Supervisor shall be the person directly responsible for the construction of the sanitary landfill and shall have the following functions, among others:

1. To distribute the program of work adequately.

2. To report periodically on the development of the activities and problems that may arise.

3. To plan the supply and maintenance of materials and tools necessary for the operation of the sanitary landfill.

4. To check that the workers make adequate use and maintenance of the tools.

5. To monitor the effective compliance with the safety standards.

6. To control the entry of solid wastes to the sanitary landfill.

7. To control the entry of vehicles and persons.

8. To orient the internal traffic of the collecting vehicles and the unloading of wastes.

9. To control the size, filling of the cells, and the cover material.

10. To check that the adjacent areas are clean and to give the corresponding orders.

Article 10. The workers shall be the persons dealing directly with the construction and operation of the sanitary landfill. Therefore, they shall be assigned exclusively to that work and may work in other tasks only if the supervisor authorizes it.

Article 11. All personnel assigned to the urban cleaning service should be provided with protective clothing and implements.

Article 12. The Office of ... should develop the studies necessary for improve the collection and transportation of wastes in the urban area of the municipality.

Article 13. The Mayor shall make the budgetary transfers for the implementation of this Act.

Article 14. Since the Municipality of ... is one of the first in the region to adopt the sanitary landfill technique, offering the community a sanitary method to dispose of its refuse, it is the duty of all persons related to the municipal administration to disseminate its benefits and merits by all available means.

Article 15. The present Act is in force starting the date of its publication.

=====FOOTNOTES/ENDNOTES =====

1. Adapted from Irvine, William. Topography. Topography.. McGraw Hill, 1975. Chapter 15.


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