Landfill Site Selection in Trinidad & Tobago

Over the last thirty years the island of Trinidad has utilized four (4) major landfills for waste disposal: * Beetham Estate Landfill – located in North-West Trinidad, size of sixty-one (61) hectares, * Guanapo Landfill – located in North-east Trinidad, size of seven (7) hectares * Forres Park Landfill- located in Central Trinidad, size of eight (8) hectares * Guapo Landfill, located in South-West Trinidad

The largest of these landfills, the Beetham Estate Landfill, is located on a swamp-type terrain in Trinidad’s north-western peninsula and serves the corridor of Chaguaramas to Curepe and also just north of Chaguanas. The Beetham Estate Landfill is described as one that has long outlived its physical capacity and expected life on the allotted site. It has been established by the State that a replacement landfill site to the Beetham Estate Landfill is inevitably soon. The location of such a replacement site must be assessed carefully to ensure suitability and demand fulfillment. There are many existing methods used for determining the location and assessment of landfill sites involving time-consuming efforts, but within recent years the advancement in computer technology has enabled the process of finding a replacement site more efficient. New software may now be utilized to aid in site selection; such a system is a Geographic Information System (GIS).

The Geographic Information System (GIS) requires the user to input relevant spatial and geographic data for the proposed site which can be processed, manipulated, analyzed and displayed to determine the site’s validity. It is this capability of a GIS that makes it useful for our purpose, establishing of suitable sites that can serve as a replacement site for the Beetham landfill. This assignment is focused on determining suitability of new landfill sites in Trinidad, particularly one that serves the needs of the north to north-western region of Trinidad and this analysis is driven by the use Geographic Information Systems (GIS).

2.0 CRITERIA USED FOR SITE SELECTION

The intent of this assignment focuses on the suitability of a proposed landfill location site within the north-western region of Trinidad. The following factors are deemed pertinent for determining the suitability for such use. a) Size of the site. A site chosen for waste disposal should be large enough to service its areas of demand. The existing Beetham landfill site has been in operation for over 30 years. A similar life span and corresponding area can be considered. A shorter life span would mean the added cost of setting up a new site in a shorter time frame. b) Buffer zone. The site chosen should include a buffer zone between the landfill and neighboring land. This barrier provides protection from direct seepage of leachate into the grounds of adjacent land and also provides an area that can be planted to serve as a visual shield of the site. It also adds a protection against fires which may occur at the site. c) Proximity to water courses. A site should not be located close to existing surface water courses. This reduces seepage of leachate into the water. The site should exist in an area where there is a deep water table, to reduce the likelihood of leachate contaminating groundwater. d) Topography.

The site should not be hilly. Land should be relatively flat or undulating. e) Soil type. The soil of the site should not be porous. This reduces the likelihood of leachate moving quickly away from the site into neighboring areas. f) Weather. The site chosen should not be in an area that receives major rainfall. Excessive runoff may mix with waste liquids and possibly get into watercourses. Landfills usually have loose dirt which may be eroded by heavy rainfall. Strong winds may cause excessive dust and waste material to go airborne. g) Ground stability. Landfills should be located in areas where the land is stable. There should not be any fault lines in the vicinity. This reduces the opportunity for new openings for groundwater to travel at the site. h) Proximity to areas serviced. The landfill should not be located so far from the sites services such that it becomes unfeasible for its use. Close proximity encourages efficient service in moving vehicles to and away from the site. However the site should not be too close to urban areas. Close proximity to urban area may lead to complaints against health hazards and noise amongst others. i) Proximity to sensitive areas. The site should be located away from certain sites including environmentally protected areas such as forests and mangroves, sites of social and religious interest, and public areas which may be downwind from the site such as schools and play parks. j) Proximity to airports. A landfill site should not be too close to airports since landfills tend to attract scavenger birds which may find themselves in the flight path of air traffic.

3.0 DATA REQUIREMENTS

4.1 Spatial and Attribute Data required to satisfy criteria

The existing landfill at the Beetham Estate has been in existence for over thirty years and is approximately 0.61 km2 in area size. This landfill receives approximately 875 tonnes of garbage and refused material per day. Assuming a substantial increase in waste collection to the vicinity of 1000 tonnes per day the landfill’s size can be adjusted, increased to 0.70 km2. On identification of negative sites the remainder of the areas can be examined to determine if any satisfies the size chosen. Various buffer zones should be considered depending on the neighboring areas. Suggested buffer zones are a minimum of 1000 metres from areas with high population densities such as residential and commercial areas, distances no less than 300 metres from industrial areas and a minimum 100 metres from major roads. Layers displaying residential, commercial and industrial areas would be required to determine where a buffer can be set up. Layers displaying major roads would be needed to produce a buffer zone. Surface water courses should be a minimum distance of 250 metres to reduce leachate from entering the water course. Groundwater and its courses identified should be a minimum of five feet below the landfill. Areas with deep water tables are the most suitable for landfills. Layers would be needed that display surface water courses. Another layer would be needed to display water table heights.

Groundwater courses generally do not flow at levels higher than the water tables, unless it comes directly from the surface. A water table level layer should be sufficient to represent groundwater heights. Potential areas should be as flat as possible; any grade in land should not exceed 10%. This enables efficient use of equipment at the site. Less work and thus time would be spent moving material (dirt) during disposal of the garbage. An elevation layer would thus be required to help in site selection. The site’s earth should comprise of soils that are preferably clay in nature. Clay soil has low permeability, thus acts as a liner, reducing leaching. A layer displaying soil types would thus be necessary for site selection. The site should not be located in areas where there is excessive rainfall. Some areas receive more rain than others. The windward/eastern side of most Caribbean islands receives more rain and strong winds than rest of the island. As a result, site selections in these areas are not recommended. In addition to dust, strong winds may aid in the spread of fires at the site. A layer would be needed displaying average rainfall and other climatic factors at various locations. Fault lines provide access for groundwater and aids in the formation of new path ways for groundwater. Groundwater is a medium of transport of leachate.

Fault lines may also crack pot liners such as clay. A layer would be needed to display known fault lines. As stated earlier, the landfill is required to service mainly the north to north-western area of Trinidad; as such the location of the landfill should not be beyond Chaguaramas, Curepe and Chaguanas, areas that are serviced by the landfill. The site map does not need to include sections beyond these areas. A landfill site should not be placed in the vicinity of certain places including wetlands, active agricultural areas and frequently used public spaces such as parks. A layer should be included that displays the land use. Layers displaying popular public spaces should also be added. Layers displaying reserved areas, (forest, wildlife etc.) should be added. Such areas should not be selected for consideration. A layer identifying airports and heliports should be included. A buffer of approximately 2 kilometres should be placed around airports and heliports.

4.2 Data Accuracy

All layers using the stated restrictions may be considered preliminary. Further investigation must be done at selected sites to ensure precision of the data. Buffers around residential, commercial and industrial areas do not need to be exactly as that suggested. A tolerance of a few metres may be used to cater for short distances, e.g. in a case where someone’s property falls partially within the buffer zone, the buffer distance may be reduced to exclude the person’s property. Data collected would define the buffer zone but this may prone to various inaccuracies. Data used may not be up to date. This may influence some sites selected for example, a new buildings may have been built between the time of capture of the data and the time of use of the data. Development of buildings in unused spaces affects the buffer zone around built up areas, as well as the population density of the area. New large structures may have gas lines, water lines and telecommunication lines run nearby, all of which may affect the site’s location. Development of areas may include excavation works that affect height of the land above sea level and thus depth of the water table. Earthworks may also affect the flow of groundwater where new canals are made. Some of the data collected may be inaccurate from the collection stage.

For example, during a census individuals may not communicate true statistics; population density statistics may be inaccurate. However these slight inaccuracies would not greatly affect potential sites. Records giving the classification of soil types may be broad. Further testing of soils in areas designated as clay may produce soils of a different nature. Further tests would be required at potential sites to conclude the accuracy of the records used. While some fault lines may be known new ones may remain unidentified. The data received may thus have good accuracy but may suffer from unintentional omission. Some data collected may not have been in a useful format and may have been processed to serve the user; this may introduce errors. For example the data collected giving heights above sea level may have been spot heights, processing the format of the data may introduce errors; again because of the leniency in the criteria.

4.3 Primary Sources of Data

Surface water courses:Ministry of Food Production, Land and Marine Affairs, the Land and Surveys Division. Roads:Ministry of Food Production, Land and Marine Affairs, the Land and Surveys Division. Boundaries:Ministry of Food Production, Land and Marine Affairs, the Land and Surveys Division. Soil type:Ministry of Food Production, Land and Marine Affairs. Water table:Ministry of Energy.

Ground water courses:Ministry of Energy.
Ground stability:Ministry of Energy.
Fault lines:Ministry of Energy.
Elevation data:Ministry of Food Production, Land and Marine Affairs, the Land and Surveys Division. Weather:Trinidad and Tobago Meteorological Office.
Buildings & Infrastructure:Ministry of Planning and the Economy, Town and Country Planning Division. Socioeconomic data:Central Statistical Office of Trinidad and Tobago.

4.4 Software and Hardware recommended for GIS

Software required should be able to perform the following processes: adjustment and map projection transformations, statistical analysis, interpolation, DTM generation, editing and adding of topological relationships and image processing. A suitable package capable of carrying out these processes is ArcGIS. ArcGIS historically has been the leader in GIS software. It controls over 30% of the market. Being the most widely used GIS software users familiar to the software can be more readily found. The manufacturer of ArcGIS, ESRI Inc. provides adequate support in terms of customer assistance, preventative maintenance and training. Other additional software that may be useful are Microsoft’s Excel and Access. Excel may be used to store data such as coordinates which may be exported to compatible GIS software. Access provides a database which stores data for easy reference. Spatial statistical analysis may be done using SPSS. Spatial analysis may be done using ArcGIS. Image analysis may be done suing ArcGIS in conjunction with raster processing software such as EGC. Hardware used for the GIS include scanners, printers and plotters, workstation and storage devices. The main item, the workstation should be sufficient to run software used, in this case, ArcGIS. More specifically the CPU should consist of a minimum 2.0GHz processor and 4GB of RAM. GPS software may be necessary for capturing and updating data; software that may aid in this is Trimble.

4.0 GIS IMPLEMENTATION STEPS

Needs Assessment
– GIS required to communicate spatial patterns by integrating
geographically referenced data. – Selection criteria determined
Needs Assessment
– GIS required to communicate spatial patterns by integrating geographically referenced data. – Selection criteria determined

Conceptual Design
* Data given in section 2.0 determined.
Conceptual Design
* Data given in section 2.0 determined.

Database Planning & Design
– Research and evaluation of data relevant to criteria set out in section 2.0 – Acquisition of data deemed suitable.
Database Planning & Design
– Research and evaluation of data relevant to criteria set out in section 2.0 – Acquisition of data deemed suitable.

Database Construction
* Input, manipulation and processing of data acquired with GIS software. Database Construction
* Input, manipulation and processing of data acquired with GIS software.

GIS System Integration
* Not necessary for the purpose of this project.
* May be incorporated into the company if similar analyses are required in the future by the company GIS System Integration
* Not necessary for the purpose of this project.
* May be incorporated into the company if similar analyses are required in the future by the company

Application Development
* Database should be periodically updated to reflect changes in landscape etc. as well as incorporate new criteria. * Application may be modified for use to locate sites for other purposes e.g. industrial plant, airport, hospital etc. Application Development

* Database should be periodically updated to reflect changes in landscape etc. as well as incorporate new criteria. * Application may be modified for use to locate sites for other purposes e.g. industrial plant, airport, hospital etc.

GIS Use & Database Maintenance
* Database should be periodically updated to reflect changes in landscape etc. as well as incorporate new criteria.

GIS Use & Database Maintenance
* Database should be periodically updated to reflect changes in landscape etc. as well as incorporate new criteria.

5.0 REFERENCES

* “Fundamentals of GIS Lecture Notes”, Dr. B.Ramlal and Dr. E. Edwards. * “Preliminary Site Selection Report for the New Sanitary Landfill at the Savannah River Site (u)” by Savannah River Technology Centerm Environmental Sciences Section, December 1992. * “Landfill Site Selection by using Geographic Information Systems”, by Basak Sener, M. Lu¨ tfi Su¨ zen, Vedat Doyuran, November 2005. * “Landfill Site Selection”, by Jarrod Ball & Associates * “Landfill Site Selection by using Geographic Information Systems” by BAŞAK ŞENER, August 2004. * “Site Selection Study for a New Sanitary Landfill for the Subic Bay Metropolitan Authority, Olongapo, Philippines”, by Scott Purdy and Francis Sabugal. * “An Introduction to Landfill Site Selection”, by Steve Last * “EPA Landfill Manuals Manual on Site Selection Draft for Consultation”, December 2006