*** Compilado por RESOL Engenharia LTDA ***






















Dr. Isabelle A. Paris









International Solid Waste Association






PALACIO DE MINERÍA, MÉXICO D.F. 14-19 de Marzo de 1994






















Landfill Course

Geological Aspect






I. Introduction

Geology, hydrogeology and hydrology are all different subjects which need several years of study and years of experience before an engineer can practice it with confidence. The aim of this one hour lecture therefore is not-to teach these subject and even less to be comprehensive. It is merely intended as an aid to understanding the factors that need to be taken into account for assessing potential landfill siting, their design, operation and monitoring.

The risks of water and ground contamination due to landfilling depend largely upon the geology and hydrogeology of the site chosen.

During the site selection phase, the geology and hydrogeology of the area must be thoroughly investigated and taken into account both at the regional and local level.

This knowledge will then be used in two ways:

1) first to select the most favorable areas (where the risks of negative environmental impact are lowest),

2) once a given area is chosen, to design the landfill in order to further minimize the potential for contamination.

This lecture will deal successively with the following points:

definition of major relevant geological, hydrological and hydrogeological concepts,

why and how waste can contaminate the environment,

how to conduct a geological-hydrogeological study,

description of best case and worse case scenario,



II. Definitions

2.1 Geology

Geology can be defined as the systematic study of the material, processes, environments and history of the earth.

Although the three are complementary, it is the nature and structure of the materials themselves that have the greatest bearing on landfill and which therefore will be dealt with here.

a) Rock types

The rocks present on the surface of the earth can be broadly subdivided into three categories, each corresponding to it's own mode of formation all three categories being linked to one another through the "geological cycle" (see figure l).


Sedimentary rocks

Sedimentary rocks are mostly derived from the destruction (erosion o chemical dissolution) of preexisting rocks, transport and deposition in layers generally at the bottom of seas or lakes and rivers (sometime directly on surface as with aeolian sandstones).

Sedimentary rocks include conglomerate, sandstones, limestones, chalk, clay...

Igneous rocks

Igneous rocks are formed through the rising and cooling of melted magma up to the surface of the earth. The original composition determine that final characteristics of the cooled rocks and it's resistance to weathering and fracturing.

Rapidly moving low viscosity magma generate the classic volcanic eruptions (basalts, tuffs). Cooler, thicker magma do not move so easily and stop below surface where they form coarser rocks. These become exposed on surface through erosion. Granites are formed in this manner.

Metamorphic rocks

Metamorphic rocks result from the transformation thought heating or regional pressure of preexisting rocks (igneous or sedimentary). The heat and/or pressure can results from the burying of sediments into the depth of the crust, from deformation during the creation of mountain ranges or from the proximity of rising igneous rocks.

Example of metamorphic rocks include schists, marbles (transformed limestones rocks) and gneisses (transformed igneous rocks).

A very important distinction can also be made between the "hard rocks" (basalts, limestones, granites, some sandstones) and soft rocks (chalk, clays, soft sand, gravel, weathered granites or basalts ... ).

The hard rock areas are not easily amenable to earth moving equipment and thus more expensive to deal with than the "soft rocks" which can be removed using earth moving equipment.

b) Geological hazards

As we have seen before, geology, comprises the study of processes involved in the development of the earth. Most of theses processes are slow (erosion, mountain formation). However, some are very rapid and drastically alter the surface of the earth. The probability of such processes, grouped under the term geological hazards, to occur must be assessed when looking for a potential landfill site. The most common geological hazards are listed below:


avalanches and lahars (for obvious reasons but avalanches paths can

be easily be forgotten, as was the case recently, in a french ski resort!)

active seismic zones,

fault zones even inactive as these would act as preferential water pathways.

c) Rock permeability

Permeability is a term expressing the rate at which water passes through a given body. It can be used to describe fluid movement in rocks, cement, plastics...

Permeability is expressed as K, in m/s and the higher the figure, the more permeable is the substrate.

For example, a very permeable rock, like a gravel formation, has a: K = 10-2 m/s.

At the other end of the spectrum, clay is poorly, permeable, (commonly termed, incorrectly, impermeable): K = 10-9 --- > 10-12 m/s. Water can still percolate through but very slowly.

Rocks can be broadly classified on a permeability scale as follows:









Fractured rocks

Sandy clays

Weathered rocks


Examples of typical permeability values are given for these rock types in figure 2.

However a given rock type cannot be automatically assigned a strict definite K value. This will depend on its local homogeneity (clay with sand lenses or vice versa), it's degree of fracturing, and it's state of alteration. K must therefore always be checked and measured in situ.

d) Geological history

In order to identify the most favorable area for the siting of a landfill, an understanding of how and why the present geological features were developed is necessary. Such an understanding allows the identification of the geological hazards previously mentioned.

The unraveling of the geological history of an area is achieved through the careful analysis of geological maps, and when these are inadequate or unexistant, through geological mapping and drilling.


The study of a geological map can show the existence of faults under a thin sedimentary cover (not visible on surface).

Analysis of sedimentary patterns indicates which zones are likely to be homogeneous, permeable, impermeable, ...

A study of the geomorphology or rivers terraces and recent deposits indicate flood plains...

2.2. Hydrology

Hydrology, is the science that deals with the processes involved in the depletion and replenishment of the water resources. These processes can best be understood by looking at the water cycle (Fig. 3).

The driving force for this circulation is radiant energy from the sun. This causes evaporation from water surfaces, the resulting water vapor comprising pail of the atmosphere. With favorable atmospheric conditions, the water will condense to form clouds from which precipitation may occur. The latter may return directly to storage in lakes and oceans, it may accumulate as snow in high mountains and in polar regions, or it may fall as rain over land. In the latter case some precipitation may be intercepted by vegetation and return to the atmosphere by evaporation. The remainder of the rainfall may collect to form surface run off or it may enter the ground as in filtration. The surface run off may then return to storage in lakes and oceans. The water that infiltrates the soil will either be taken up by plant roots and transpired to the atmosphere, or it will percolate downwards through the unsaturated zone to the water table.

This groundwater may then move towards surface discharge points (spring etc) where it will become a component of surface runoff moving towards oceans and lakes.

As far a landfill siting and designing is concerned, the following data needs dot be recorded and assessed:


Wind, rain or snow, and temperature are climatic conditions that may mandate the type of operation, amount and placement of soil cover, kinds of roads needed, and type of structures constructed on a landfill. Hence, it is imperative to have information on the number of days of wind, freezing temperature, rain or snow, to aid in selecting a site for a sanitary landfill.

Rain or snow

Precipitation must be considered with regards to surface water runoff, drainage system required for its control, leachate generation, feasibility of sustaining operations at all times on site, movement of equipment, and access to and front site. For instance, low lying sites that might frequently flood or become muddy during rainy weather should not be chosen in areas having high rainfall.


Climate and degree of infiltration

Climate is significant because of its direct bearing on the amount of rainwater that may infiltrate through the unsaturated zone and into a groundwater system. Degree of infiltration is a function of the amount of precipitation, volume of surface ponding, and runoff, and the evapotranspiration rate. (Evapotranspiration refers to the water released into the atmosphere by plants- in this case, the vegetation growing on the landfill cover). Ambient temperature and relative humidity also have an impact on infiltration, evaporation, and evapotranspiration. The potential for groundwater degradation from a well-designed and constructed landfill in arid and semi- arid regions is quite low, whereas the potential is quite high in humid regions. Another decision factor in selecting a suitable site is the quantity and seasonally of rainfall. For example, if rainfall is highly seasonal (e.g. Mediterranean type climate), the quantity of rainfall during the wet season may be relatively low.

Stream Density

The likelihood of surface water contamination increases in areas in which an unusually short underground flow path precedes discharge of contaminants into an area in which streams are closely spaced. However, the overall extent of any groundwater contamination may be limited by subsurface media. Alternately, widely spaced streams may also lead to the development or larger and longer-term groundwater contamination zones.


2.3 Hydrogeology

Hydrogeology can be defined as the study of groundwater, its chemistry, mode of migration and relation to the environment. The relationship of groundwater to the water cycle can be seen in figure 3. Therefore the possible impact of a landfill on the groundwater regime must always be carefully answered.

Let us define the mains terms and parameters necessary to understand and assess the groundwater systems:


recharge and discharge zones,

saturated/unsaturated zones,

hydraulic conductivity,

porosity and velocity.

What is an aquifer?

An aquifer is a body of rocks containing water with sufficient permeability for the water to flow. Three sorts of aquifer can be distinguished:

1) Sandy aquifers: In these aquifers, water flows, through the voids in between the grains: the intergranular porosity.(Fig. 4). Such aquifers can be found in sands and gravels.

2) Fractured aquifers: these aquifers occur in fractures poorly permeable rocks such as sandstones, chalks, limestone, volcanic rocks ... The water flows through communicating fractures and cracks: the fissure porosity. (Fig. 5).

3) Mixed aquifers: Theses aquifers contain both fissure and intergranular porosity and occur in karstic environment. (Fig. 6).

The infiltrated water reaches the "aquifer" more or less rapidly depending on the permeability of tire rocks it encounters. Through chalk, for example infiltrated water can take up to one year to reach the underground water. In schist and granite, in principle impermeable rocks, water can still percolate very quickly through the fractures or weathered zones.

Different configurations of aquifer

Aquifers are classified as unconfined or confined depending how they are bounded.

A confined aquifer is bound by two impermeable layers. The water is under pressure and the water level goes up when a bore hole is dug in such an aquifer or if part of the surface is dug out. The level to which the water rises in a bore hole is called the piezometric level. (Fig. 7).

An unconfined aquifer is an aquifer where the water table (or piezometric level) is free to fluctuate up and down, generally seasonally. (Fig. 8).











Recharge and discharge zone

As seen in the water cycle (Fig. 3), aquifers are filled (recharged) up through the infiltration of rain water through permeable strata. (Fig. 8).

Upon reaching the aquifer, the water flows under the regional hydraulic gradient and gets discharged again at springs, from seepages into river and pumped wells.

Thus, within an aquifer, water is not stagnant but flows from the recharge to the discharge zone. Rates of flow vary according to the type of aquifer: for example 1.500 m/y in alluvium and 3,5 to 9 km/y in a karstic system.

Saturated/Unsaturated zone

In an unconfined aquifer, two successive zones are encountered by the water percolating downwards from the surface.

The unsaturated zone when the rock interstices are partially occupied by water and partially by a gaseous phase (air). In this zones different complex mechanisms can interact with a percolating fluid (leachate or other pollutant): sorption, neutralization, precipitation, oxydo-reduction, biodegradation.

Although these mechanisms have been observed, they are yet to be precisely quantified and understood.

The saturated zone starts at the level of the water table when the rock interstices are entirely filled with water. In this zone, the groundwater flows under regional hydraulic gradient to the discharge zone.

Hydraulic conductivity, porosity, velocity

These terms are the most commonly used to characterize aquifers. Before defining them, one must first of all understand the most important law governing aquifers, Darcy's law:

Darcy's law: (figure 9)

Darcy's law allows the calculation of the discharge (Q) that is flowing through a given cross sectional area of a rock.

The equation is:

Q = kSi

Where Q = discharge (m3/s or m3/d)

k = permeability (m/s) or hydraulic conductivity (m/d)

S = cross sectional area

i = hydraulic gradient

Example of how Darcy's law is applied (Fig. 10):

If we imagine 2 m of water logged waste over a surface of 1 km2 overlying 5 m of clay, with a permeability K = 10-12 m/s. the flow of water through the "impermeable" layer is: Q = ksi.

Q = 10-12 m/s x 106 m2 x 2 = 4.107 m3/s = 12 m3/year.


Hydraulic conductivity is synonymous for permeability (K) previously defined. It describes the capacity of rocks to transmit water and is generally expressed in m/s.

Porosity is the measure of the interstitial pore space expressed as the relative volume (in %) of rock occupied by voids. In fact, part of the water present in the voids is retained by forces of molecular attraction, adhesion and cohesion. So, in terms of real storage potential, the use of effective porosity (n). in the free storage space, is more appropriate. For example, while clay, has a high total porosity, it has a low effective porosity. (Fig. 11).








Rock type

Total porosity range %

Effective porosity range %



Saturated hydraulic conductivity range m/d









F + I















F + I





F + I





F (+I)


Igneous and Metamorphic

(probably less than 1)

F (+I)


F = fissure flow, I = Intergranular flow

Fig. 11: Porosity ranges, flow types and saturated hydraulic conductivities for various rock types.



III. Risks of water contamination by waste

Surface water contamination (Fig. 12)

The main risks of surface water contamination are listed below:

1) If a landfill is located below flood level, each flood will penetrate the waste, flow across the landfill and disseminate polluted water and in some case even waste into the river system and surrounding area (so flood plain levels must be identified).

2) A landfill close to sea level, similarly, can pollute sea water and nearby, beaches during high tides.

3) A landfill close to a river can pollute it with seepage of leachate from the base of the landfill to the river.

Groundwater contamination

Several types of situation can result in ground water contamination:

1) A landfill with a permeable base and close to the water table. The unsaturated zone is non existent and the leachate percolates directly into the aquifer, creating a plume of pollution that can be very extensive.

2) A landfill located above a fractured zone. Even if the rock itself is unsaturated, leachate will reach the aquifer directly and quickly through the fractures.

3) Similarly, leachate can reach the aquifer through heterogeneities and discontinuities in an otherwise impermeable zone (for example along a fault zone, or along a thin limestone layer within a clay horizon).

IV. How to conduct a geological/hydrogeological study

4.1 Regional study

What needs to be known:

The geology, of the area in order to identify fault zones, impermeable areas, heterogeneities...,

The geomorphology of the area, to identify geological hazards such as flood plains and to delineate the water basins,

The hydrology: all the aquifers must be identified together with the surface water network and the water flowing direction.

These informations can be gathered from existing maps, aerial photos, boreholes, and reconnaissance field work.

4.2 Local study

What needs to be known:

Detailed geology,

An inventory of springs and water boreholes,

Detailed hydrogeology (depth to aquifers, piezometric levels, quality of water),

Permeability of the different formations.

Such data is obtained through:

Detailed geological mapping,

Drilling and careful logging, of the core,

Installing "Piezometers" in several boreholes and monitoring the water movement (existing piezometers can also be used if available),

Analyzing the water in the piezometer.

It must be pointed out that the drilling and installing of a piezometer needs to be very carefully supervised by a specialist as if sufficient care is not taken, very costly mistakes can be made (like missing an aquifer, tapping, and thus measuring the wrong aquifer ...

Measure in situ of permeability, on surface and inside boreholes. These measures must be made and interpreted by specialists and the interpretation must be linked to the geological mapping (a layer of material with K = 10-9 m/s can occur within a formation of siltstone (K= 10-12 m/s) and a thick clay formation (K = 10-12 m/s) can be locally fractured which lowers K dramatically, or contain sand lenses (K = 10-4 m/s).






The purpose of this section is to work through the process that leads to the development of a site for landfill. It can be a very long process. It may take five, ten or even more years to complete the process from first consideration to depositing the first load of waste in the site. This section is based on the idea that we are in charge of waste disposal in a region of a country and we have the task of ensuring that its waste disposal needs are met.


It may be obvious that new facilities are necessary but it is advisable to follow a logical process in evaluating the need and the proposals to answer that need.

Different types of waste to be accommodated

First we must define the types of waste that we are going to be concerned with. Unless there are special requirements the list of wastes will include the following:

· Construction and demolition waste.

· Excavated soils.

· Some industrial waste.

· De-watered sludges from waste water treatment.

Local circumstances may add other types of waste to this list. Many industrial wastes will

not be suitable for landfill and will require treatment or incineration.

Measuring the quantities of each type of waste

The next stage is to find out how big the problem is. We need to know how much waste is being produced now and how much is likely to be produced in the future. The best method of measuring waste quantities is to weigh vehicles entering existing disposal sites. It is important to ensure that no scavenging or illegal disposal is taking place before the waste arrives.

The weighing scales may be permanent scales- part of the site infrastructure- or they may be portable. If it is impractical to weigh all vehicles then a random sample should be weighed, preferably over periods of several weeks at different times of the year.

If a well-established disposal system does not exist, then it is probably better to rely on tackling the problem at the other end- where the waste arises. Again, it will be necessary to set up a sampling system covering different socio-economic areas, so that quantifies per head of population can be calculated.

Either way, the objective is to arrive at a total quantity of waste to be disposed in tones/year.

We then move on to forecasting the future. Lots of estimates of future waste generation have been given, but few are based on accurate records because generally such records have not been reliable. Also, waste generation is very dependent on forecasting the behavior of the economy and if we were good at that we probably wouldn't be involved in waste disposal!

The safest prediction is simply to allow for population change and increase or decrease on a pro-rata basis. If the population is forecast to double in 10 years then the quantity of waste is likely to double as well.

Composition of the waste

Because we are looking at a landfill strategy, composition is less important than where recycling or treatment by incineration or composting is being considered.

Samples of not less than 100 kg have to be taken and hand sorted and the individual constituents weighed. The sampling needs to be carried out on at least 2 and preferably 4 occasions during the year to catch seasonal variations. Recent field work has shown that, over a 5 year period, significant changes in refuse composition can take place.

The quantity of waste dictates factors such as volume, frequency and number of vehicles using a site, land area required and the amount of cover material needed.

The composition of the waste has an impact on the area requirements for each cell since we normally try to deposit waste in small cells which will not become saturated with rainfall. It also affects the number of passes required to achieve proper compaction and the type of

equipment needed.


The next stage in planning the strategy and selecting a suitable site is to review all the existing facilities.

It is necessary to look at all existing sites and to calculate the remaining capacity.

Some form of surveying will be required. There should be plans showing the extent of existing landfills and contour drawings showing the eventual restored landform. If these don't exist then they need to he prepared. Surveying for waste disposal landfill sites does not need to be carried out to the nth. degree of accuracy. Allowing a reasonable degree of accuracy can save costs and speed up field work.

In some cases, aerial survey may he the most efficient way of measuring volumes particularly if a large number of sites are involved.

It is common experience that landfills last longer than you think they are going to and then suddenly they run out! We need to have realistic figures for existing capacity.

When we have carried out our surveys we add the capacity of all our facilities together and divide by the total quantity of waste produced per year and this should give us the number of years we have available before a new site is required.

This little sum requires some knowledge of the volume occupied by 1 tone of refuse. It is a figure which varies with type of waste, method of compaction and over time and with depth in the landfill. In the absence of better information a figure of between 0.8 and 1.0 tone per cu. m. may be used if reasonable compaction is being applied. If not, then densities may be down to 0.5 tone per cu. m.


Having worked out the life of existing facilities it is useful to draw up a programme of work. By the time the existing facilities are full we must have our new site in operation. There are several procedures which have to be undertaken depending on the particular legal and administrative requirements of the area. Typically:

· We have to select the site.

· We have to prepare an application for its use to the authorities.

· We have to comply with the permitting procedures.

· We have to carry out the engineering works.

These procedures can take a very long time!


We are now in a position to start looking for our new landfill site.

Firstly we must establish the overall boundaries of our search area. This will be based on demographic and physical limitations such as political or regional boundaries, mountain ranges and rivers.

Next, we must establish suitable study areas on the basis of haul distance, topography, geology and surface and groundwater conditions.

Haul distance

The distance of the landfill site from the area where the waste arises land is collected is known as the haul distance.

If the landfill is close to the collection area then collection vehicles can travel directly to the landfill.

If the landfill is remote from the collection area, some form of transfer station is needed. Collection vehicles are expensive pieces of equipment and should spend most of their time collecting waste!

At a transfer station the waste is "transferred" from the collection vehicle to a bulk transport system. This is most likely to be bulk lorries, but in an extreme case could be rail.

A lot of financial factors come into play here. What we are concerned with is the total system cost. That is the cost of collection + transfer + landfill.

Landfill sites benefit greatly from economics of scale and so a very large remote landfill may be less expensive than a very small local landfill.

Identification of sites

Having identified our study areas, bearing in mind the boundaries and the access constraints and the physical limitations, we are now in a position to identify suitable sites.

These will be of two types:

· Mineral excavation areas where waste can be used to restore the ground.

· Areas of virgin land where a new landform can be created.

A lot can be achieved from maps and by travelling around looking. We should produce a

list of every potential site with a few notes about its major features.


We are now in a position to start eliminating many of the potential sites.

It is common experience that there are four critical factors in the selection of a potential site:

· Availability- If it isn’t going to be possible to acquire the site there's not much point proceeding with it.

· Planning Constraints- There may be some form of zoning or special planning, requirements. There may be a water protection zone. Such sites should be rejected.

· Access- It has often been found that access is a critical factor. The public sometimes seem to be more concerned with lorries than the actual landfill, so there must be an adequate access. Landfill is the one engineering operation that has to go on regardless of weather, so access is critical.

· Capacity- Because of the long time required and the considerable expense involved in developing a new landfill site it must have adequate capacity. A minimum of ten years is often considered desirable.

There may be other critical factors in other situations, but the aim is to get to a position where there is a short-list of about 4-6 possible sites, which pass the critical factor test.


The next stage is to carry out an environmental assessment of our preferred sites.

This will require the preparation of designs for each site and we should also calculate the total system costs of running each site. From this we can identify the effects of each site on all elements of the environment.

It is useful to draw up some form of evaluation sheet- listing each site and each factor and

assigning a weighting for each. Different elements of the environment may he ranked as more or less important. We thus end up with scores for each site and some sort of ranking order.


The evaluation sheet needs to identify all the possible impacts of the site together with certain other information already describes such as costs, access, and capacity. The impacts to be considered include:

· The effects on human beings living near the proposed landfill.

· Possible damage to buildings or structures from landfill gas or vehicles passing nearby.

· Effects on the local plants and wildlife.

· The nature of the underlying and surface geology.

· The effect of potential emissions from the site to land, water or air.


With the evaluation sheet in front of us we can consider each effect on each site and see if there are measures that can be taken to mitigate any nuisance.

These could range from building a long by-pass road to erecting a soil bank to reduce noise or visual impact. These measures need to be costed and built into the assessment.

Having done all this work we now will probably have to reject some more of our sites and we should be left with perhaps 2 or 3 which we would be happy with.

We now start on the final and most difficult part of the exercise - GOING PUBLIC!


Public interest in environmental matters has increased dramatically in recent years. The point at which we go public with a proposal such as siting of a landfill is a matter for debate.

Going too early raises unnecessary opposition. Going too late raises accusations that everything is all agreed in advance.

If several genuine alternatives emerge from the selection process which has been describes then this is a good time to explain to the public that is involved.

Some of the reasons why people are most likely to feel affected by a new landfill proposal are:

· Proximity- how close the landfill site or access route is to their houses.

· Economic- whether landowners will have the value of their property reduced by the presence of a landfill site.

· Leisure use- whether fishermen, bunters, or hikers etc. will have their leisure pursuits damaged by the presence of the landfill.

· Social- whether people will feel their life-style is threatened by, the influx of construction or landfill operatives.

The foremost thing municipal officials can do to solicit public support is to convert any existing bad sites into well run sanitary landfills with a clear useful end purpose.

Objectives of a public awareness campaign

In going public about a new proposal it is necessary to have clear objectives. These objectives may be as follows:

· To make certain that the public understands the proposals.

· To assure the public that their views will be listened to.

· To ensure that the government or public authority is responsive to the public.

· To provide opportunities for public involvement in decisions.

The advantages of a campaign with these objectives are:

· It increases the likelihood of agreement with the plans.

· It provides useful information which may have been missed.

· It gives assurance that all views have been considered.

· It ensures accountability by decision makers.

· It provides an effective mechanism to ensure decision makers take into account issues around the project.

The disadvantages of such a campaign are:

· There is the potential to create confusion because new issues are introduced.

· Uninformed participants may distribute erroneous information.

· Public involvement adds cost to project.

· There may be delays to the project.

· The project may become a platform for politicians.

It is considered that none of these disadvantages are sufficient to outweigh the benefits of an effective public awareness campaign.


The following steps are appropriate for a public information campaign:

· Inform the public of all the details of the scheme.

· Establish the need for the new site by explaining the situation in respect of existing

facilities and why a new site is therefore needed.

· Explain the alternatives that have been considered and why they have not been selected.

· Explain the operations, how the site will be managed, how gas and leachate will be controlled, and how the site will be restored and managed in the aftercare period.

· Be honest about the impacts of the site on the local environment and the people who may be affected.

· Try to understand the concerns of people who live nearby and don't try to confuse them with "science".

· Keep options open so that if new information emerges as a result of the consultation it may be taken into account and the proposals may be modified.

· Review previous assessments of environmental impact as more information is gathered by talking to people affected by the proposal.

Finally, we should be able to make our final selection and we are now in a position to make our formal application to use tire site. Much of the work already carried out will be of use in preparing tire fiscal design and operational plans.



Waste Monitoring and Planning- A description of the regional waste planning system developed for London and South-East England. 1987.



by M.J. Philpott, AKC, CEng, BSc(Eng), MICE, MInstWM,

Assistant County Surveyor (Waste Disposal), Oxfordshire County Council

(This presentation was accompanied by a series of slides. Some of these are reproduced as Tables or Figures; the content of others has been incorporated in to the text).


In my presentation, I intend to deal with three aspects of our work in the Waste Disposal Working Group. Firstly, I will explain how we developed a comprehensive waste monitoring scheme for the region. Secondly, I will show how the results of the monitoring are an essential part of every authority's waste disposal planning process. Finally, I will make some observations on the predominant role of landfill as the means of waste disposal in the south-east.

The Monitoring Survey

In 1985 we carried out our first monitoring survey. The survey was in two pats. Firstly, we asked every authority to identify every single existing or potential void space in their area. We then asked them to make a subjective judgement for each site as to its suitability for waste disposal.

We asked officers to assess the sites into six categories:

Category 1 included all sites which have planning consent for disposal;

Category 2 covered sites which were likely to be supported;

Category 3 was for those sites which did not appear to have major problems;

Category 4 comprised sites with severe problems;

Category 5 was for sites where the problems were thought to be insuperable; and

Category 6 was for sites already committed for alternative development.

So the final three categories were all sites where waste disposal was not felt to be possible

because of serious or overwhelming problems or because the site was committed for something else such as an industrial estate or a hypermarket.

We ended up with 500 million cubic metres of possible void space, as shown on Table 1. Nearly 300 million cubic metres is in major consented sites and these are located in the areas shown on Figure 1. Individual sites are shown by the dots. Groups of major sites are shown within the shaded areas. It will be seen that there are areas with no major sites such as West Berkshire and north-west Hampshire and of course, most of London.

Table 1

Void space by category up to 2000

(cubic metres)

Category 1 – consented


2 – potentially supported


3 – Without apparent major problems




Figure 1

Location of sites with consent for landfill.



The second part of the survey was concerned with the waste arisings in the region. Table 2 shows the overall figures for the south-east. Public authorities have, in the past, tended to concentrate very much on the first two figures only. These are the wastes which they have a statutory duty to dispose of. However, they represent less than 20% of the total. Over half the total waste is inert waste- that is, soil or waste from the construction industry. The other 30% is commercial or industrial waste, comprising packaging and paper or waste from industrial processes.



Waste arisings in the South East region



(% of total)




Civic amenity



Industrial and commercial









Table 3 shows that nearly half the total waste in the region arises in London. Again the proportions of waste in the different categories are very significant. When we think of the rail transfer stations, the river-based schemes and the giant Edmonton incinerator, it is important to realize that all these schemes were designed to cater for just part of one element of the total- the household waste element. All the rest, the other 80%, is controlled by the private sector and is hauled out of London each day by thousands of lorries to landfill sites in and around the capital.

Table 3

Waste arisings in the South East region



(% of total)




Civic amenity



Industrial and commercial









Having assembled all this data, what next? If I take my own county as an example. In Figure 2, the upper line represents the void space likely to be available up to the year 2000. The short line represents the volume of that void space which will be taken up by own waste- both public and private sector. The long lower line then represents the theoretical volume which might be available for imported wastes.

Figure 2

Landfill resources to 2000- Oxfordshire

Landfill capacity available

Not all counties are in the same position as us and if I take another example- Hampshire- you can see why. Figure 3 shows that capacity of available landfill space and incineration capacity falls short of the need in Hampshire itself. There is a shortfall of capacity which either has to be met by exporting waste or by using less-favoured sites or by landraising schemes.

Figure 3

Landfill resources to 2000- Hampshire

Landfill capacity available

Figure 4 represents the overall waste disposal situation for the whole of the south-east over the next 12 years. It shows those areas which will be "in the red" and it shows those counties which have theoretically available space to accommodate the deficit. It shows very clearly how the nub of the regional problem is what to do with London’s waste!

Figure 4

Overall waste disposal situation to 2000




Planning for the Future

In 1986 and 1987 it was the next stage of the work that caused the greatest problems. What we wanted to do was to estimate how much waste would be likely to be imported into each area year by year.

The way the waste disposal system works in the South East is that waste from those areas in deficit is transported to those areas which have surplus capacity. Market forces in the private sector ensure that generally the cheapest, shortest solution is found. So, for example, waste from London is taken out by lorry to Essex or Herts or other counties-bordering London. The public sector, on the other hand, has somewhat different perceptions. It is particularly concerned with security of disposal. Therefore in London we have the large transfer stations and the long-term contracts transporting waste to massive sites on the edges of the region. As sites near to London are filled, it is thus the private sector that will have to adapt the most.

How do we estimate how much waste each county is likely to have to dispose of in the next 10-15 years? Following the 1985 survey we put forward one model as a suggestion. Figure 5 is designed to illustrate this model. The thick line represents a void equal to the total capacity available within a county. As a priority, it is then partially filled with its own waste as shown by the lower area. The remainder is then filled with imported waste; when no more capacity exists, the flow of imported waste is diverted to the next nearest area.

Figure 5

Model of waste movements


In the view of the Waste Disposal Working Group, that is a reasonable scenario. There are other ways of looking at the problem but the end result will not be too different. The exercise is a logical one. Waste is produced every day. It has to be disposed of. It occupies space. That space has to exist somewhere!

As a consequence of this exercise we produced a table showing how much waste would need to be disposed of in each county. Table 4 gives the figures that were produced for my own county. They show an enormous growth in imported waste after 1995. At the moment we take one train a day from London, the final figure showing imports between 1995 and 2000 is equivalent to over ten trains a day.

Table 4

Waste requiring disposal: Oxfordshire


(cubic metres)













Figure 6 shows how such imports would affect the landfill resources in our county. The lower shaded area represents the space which is already consented. The middle shaded area represents the space in potentially supported sites and the upper hatched area represents the sites without major problems. If we only consider local waste then we have sufficient consented capacity to meet all our requirements into the next century. When we add in the extra competing claims of imported waste then we begin to use up all our readily available space so that we could need to be thinking about less favoured sites. A similar situation applies in all of the counties surrounding London since the total quantity of waste to be disposed of in the next 12 years is only just short of the total void space likely to be readily available.

Figure 6 Landfill requirement- Oxfordshire

The regional planning process can be summarised thus:

The WDAs carry out surveys of void space and waste arisings;

SERPLAN estimates the likely flows;

The WDAs consider the implication of these flows;

SERPLAN reports on any particular problem areas.

It is intended that this process of monitoring and analysis should be repealed every two years. The second monitoring survey has just been completed and we are now beginning to analyze the results. It is intended to report on this survey later this year and then the third monitoring survey will take place in November 1989. In this way, waste disposal authorities will always have an up-to-date context within which to plan and make decisions.

I have spent some time describing the process that occurred as we carried through the first survey. This is the process that is outlined in the Guidelines in paragraph 36. I now want to turn to the way in which this process will be integrated into the formal waste disposal planning system.

Waste disposal planning is implemented through waste disposal plans as describes in the Control of Pollution Act. The waste disposal plan is the means by which each authority ensures that sufficient resources exist for the disposal of wastes which will arise or will become situated for disposal in its area. Nearly all the plans so far produced concentrate on the household waste which the particular authority is directly responsible for.

Figure 7

Waste disposal plans

Figure 7 shows (shaded) those authorities that have produced plans to date. The hatched counties are those that have published limited plans. But the point I want to make is that so far very few of the plans fully address the problem facing commercial or industrial waste producers and little attention has been paid to the regional dimension. Thus is not surprising for three reasons:

- Section 1 of COPA has not been implemented, and thus has taken the pressure off Waste Disposal Authorities having to consider all wastes in their areas;

- The time limit which was to have applied for their production has been withdrawn- this was probably done to avoid pressures for additional staff to produce waste disposal plans;

- Information on the regional flows of waste was not available.

The Guidelines are designed to supply the information required on inter-authority flows of waste but they go further than that. In addition to the discussion of the issues in waste disposal that Mr. Selfe will describe they also set out a basic formal for analyzing the waste disposal situation in each authority. The format is shown in Appendix 2 of the Guidelines. It is suggested that each authority should include a section in its plan covering these four headings:

Potential space includes a survey and assessment of the total void plus any additional space from landraising schemes;

Waste arisings covers all wastes arising in the authority's area together with forecasts of future arisings;

The regional context comprises the information supplied by SERPLAN on likely imports and exports.

The overall situation is obtained by putting all these ingredients together and looking at the implications for the authority concerned, the private sector, and also other authorities.

It is hoped that all authorities will adopt this approach in their waste disposal plans.

The Role of Landfill

In the course of debates about the work we have been doing over the past three years, two issues have been repeatedly raised- incineration and recycling. Other speakers will be dealing with these this afternoon, but I want to comment on their significance in terms of the region's landfill requirements in the future.

The Edmonton incinerator is a very large and impressive structure. It disposes of 3-400,000 tonnes of waste each year. If we built two more Edmontons the total landfill space required in the region up to 2000 would be reduced by 2.6%.

Suppose somehow local authority recycling schemes are really developed and our present activities are increased by 5 times! We would reduce our landfill requirements in the region by just 2%.

Even if we are enthusiasts for large plants and recycling schemes, can we really see such changes occurring over the next ten years? And even if such changes were to occur then they would make only a marginal difference to the region's overall requirements for landfill space. In any case, landfill itself can be a producer of energy- through methane gas- and it is a means of recycling- of land.

Other methods of waste disposal will have a part to play, and perhaps a growing part, but your technical officers on the Working Group are in no doubt that landfill will continue to be the absolutely crucial element in waste disposal in the South East.

Throughout the South East there are enormous scars left by the extractive industries and every year millions of cubic metres of new space are created. In the South East, 2-3 square miles of land are opened up every year for sand and gravel extraction alone. The mineral operators and the planning authorities have devised many imaginative schemes to make the best of these necessary scars on the landscape but there is only one way of healing them completely and that is to fill them up again. Restored landfill sites can leave little or no trace of the activity once filling is completed.

It has been interesting as part of our working together with SERPLAN to see how sites which appear to be very similar in two authorities may be viewed quite differently by the planning committees and officers of each authority. Often it is their perception of waste disposal operations which will decide whether or not a particular sale will go ahead.

In the past there were good reasons why waste disposal was such an unpopular activity- I inherited a site in 1974 where the only equipment was a box of matches! Now however, things have changed. The best sites now are a world away from the general standards that existed before 1974. The scars left by mineral workings can only be healed by refilling them and the only material available to do that is waste!

The region's waste disposal problems will only be solved by developing a continuing programme of landfill sites and it is up to the authorities and industry working together to demonstrate that this landfilling can be done in an environmentally acceptable manner.


<!---assunto meio ambiente assunto medio ambiente assunto environment --->