Maps and Legends

Maps and Legends

GIS applications in solid waste management, from collection to post-closure.

Public planning, especially in the area of solid waste management, is an extremely complex subject. Geographic information systems (GIS) can be valuable tools in the environmental planner’s toolbox, saving time, money and headaches when planning collection routes, siting processing facilities, as well as choosing locations for landfills and planning what will become of the landfill once it is full. As GIS technology has become easier to use and more cost-effective, more and more government agencies are employing GIS professionals. Chances are your city or county already has a GIS professional just waiting to help with your solid waste management project. This article will provide an overview of GIS and how it can be applied to the various areas of solid waste management.

What is GIS?

A geographic information system is an interconnected web of hardware and software designed to collect, organize, analyze, store and display spatially referenced data in order to answer complex questions. What does this mean to the environmental planning professional? Simply put, GIS is a way to take data you already have along with data you can gather from tools such as GPS receivers, and combine, organize and manipulate it to serve a higher purpose. GIS can be used to solve complex planning problems often associated with the management of solid waste.

One of the most time-consuming aspects of using GIS planning is data acquisition. In many instances the data may already be available but must be formatted so that it is compatible with GIS software. In the event you have to acquire new data, it will take time and money, but when complete will provide a structure for future applications.

Research Limitations Note: In putting together this article I discovered a fair amount of research relating to GIS applications in certain areas of solid waste management, routing and landfill siting specifically. However, an overwhelming majority of the published literature was related to solid waste management in European nations and not in the United States. Another issue I noticed is that a majority of the available GIS-related research focused on broad environmental issues, such as habitat destruction and preservation. Some of the applications that will be outlined below could benefit from further academic research.

Applications in Collection

As many waste managers will attest, planning routes for garbage, yard-waste and recycling collection is complex to say the least. Many factors must be considered when planning collection routes, including the number of stops, fuel efficiency of the collection vehicles and labor agreements, just to name a few.

There are multiple layers that go into making a GIS route map. The first is a customer list with addresses. This list is geocoded to a road network map to provide a base layer upon which routes are built. The next consideration is waste generation per customer. In all likelihood this will be an estimate initially, based on total waste tonnage delivered from each existing garbage route. With many cities turning to volume-based garbage rates it is possible to accurately determine the weekly waste production of each customer by incorporating weighing capability on the arm of many automated garbage trucks. If this is not an option, GIS can easily estimate the volume of garbage per household based on calculations involving population density and local income group distributions. Another key piece of data is a traffic flow study to help minimize congestion caused by collection vehicles. As with all planning tools, the more accurate and up-to-date the data is, the better the outcome will be.

Once the customer data has been organized and connected with the base map then the actual route planning can begin. The key word in route mapping is efficiency. Routes should seek to minimize travel time to the final disposal facility, which may mean splitting existing routes up among multiple trucks. Routes should also be laid out in deference to traffic flow; you don’t want to pick up garbage near a school in a residential area right as parents and buses are dropping off students.

GIS software allows you to input all of these factors into  programs such as Quantum GIS, Grass GIS or ArchInfo network analysis program and discover the best distribution of your collection resources. These steps can be applied to yard waste and recycling collection routes as well, which will probably require different routes based on generation of the materials being collected and the final destination of the material.

Recycling Centers/Drop-Offs

The siting of facilities such as recycling centers/material recovery facilities (MRFs), yard waste facilities and transfer stations is another area where GIS can help smooth the process. All three  facility types are subject to public opposition due to litter, odor and other vector concerns. The use of GIS can help to alleviate some of these concerns before they arise.

Consider the need for a recycling drop-off location separate from the centralized facility. To determine the best location for the drop-off, consider its location relative to the population that will use it. It is very unlikely you will be able to site the drop-off in the middle of a neighborhood, but you might be able to purchase or lease a suitable plot of land near a new suburban shopping district that is in close proximity to your users.

Next you need to look at the traffic patterns of potential users. The drop-off should be near highly traveled roadways but not so close as to cause congestion. The site should also be readily accessible to your collection trucks and near enough to a main artery that minimal time will be spent transporting the recyclables to the central facility.

These conditions can be entered into a GIS software package as layers. The built-in features of the software can then be used to create overlays ranking ideal locations based on your chosen criteria. One layer might include all available land needed for the drop-off. Next you could create a buffer around all sites within a given proximity to a major road. This could be saved as a layer and further analyzed by determining the average distance from each potential drop-off site and the central recycling facility.

Yard Waste Facilities

Siting a yard waste facility is similar to siting a recycling drop-off, with a few modifications. Unlike the drop-off, which you want close to your users, the yard waste facility would be better located away from residential areas to prevent issues related to odor. In this case, a first step would be to determine the amount of yard waste that will be handled by the facility. Looking at the land uses in the service area will help determine landscape types. Data should also be gathered on the amount and types of trees in the service area as they will contribute to the amount of material that must be processed.

Once the amount of material to be processed is determined it is then possible to determine the amount of land necessary for the facility. You can run a GIS query to select all plots of undeveloped land from a land-use map and the result saved as a separate layer. This layer can then be used to select only those areas within a given radius of the users and the collection fleet operations building. If there are still too many sites, a query can be run to select only those sites within a given distance from a main road to facilitate easy transport of the material in and the finished compost out.

Transfer Stations

Transfer stations, like landfills, often face public opposition, largely due to litter and odor concerns. Here a properly executed, GIS-backed site selection prepared early on could help to smooth the siting process. Transfer stations are a necessity in areas where final disposal, be it a landfill or waste-to-energy plant, is far enough from a given population that it becomes economically inadvisable to send garbage trucks back and forth daily.

In this case, the facility needs to be as centrally located as possible with access to an efficient route to the final disposal facility. With the data collected for the GIS-generated collection routes, solid waste volumes are already known and therefore the size of the facility can be determined. You can run a query to select parcels of the needed size that are geographically centered based on outlined city limits. This selection can then be further analyzed by eliminating sites within a given distance (buffer) of sensitive populations (elderly, schools, hospitals, etc.). Another layer could be created using these selected parcels and the road network to determine those parcels that have adequate access with minimal impact on existing traffic patterns.

Landfill Siting

When it comes to landfills, the application of GIS currently appears to be limited to siting. This is not surprising given that the process of siting a landfill is extremely difficult. But there are other potential applications of GIS when it comes to landfills that warrant consideration. More on those later.

Selecting a landfill site involves a range of considerations. As the U.S. Environmental Protection Agency (EPA) outlines, landfills must be located in such a way as to protect groundwater, surface waters and the surrounding environment from the effects of the waste stream. In “Developing and Implementing GIS-assisted Constraints Criteria for Planning Landfill Sites in the U.K.” authors Baban and Flannagan identified several landfill site constraints for a landfill in England. The first was locating the site outside of densely populated areas. The second is that the site must be within 10 kilometers (6.2 miles) of an urban area, where the waste is generated. This is a bit of a Catch-22 in that you rarely find a large enough area of land near urban areas, and urban populations tend to oppose landfills. The third constraint they identified is related to distance from major roads -- between 0.2 and 10 km (0.12 – 6.2 miles) -- to facilitate the flow of waste yet prevent problems of windblown litter and other vectors. The remaining seven constraints are related to protecting ground water and surface waters, land of ecological value, agricultural land and that the site be acceptable to the public.

All of these constraints are easily identified in a GIS program and can be queried and overlaid to produce a suitability map. Buffers can be put in place around ecologically sensitive areas, potential sites of ground and surface water pollution and roadways. A planning and zoning layer can be queried to identify available parcels that are not agricultural lands. New layers can be created from the queries and in those layers any ecologically sensitive areas can be clipped out. Overlaying all of these layers reduces the number of suitable sites to only the most suitable, which then must be subjected to the hardest step: public approval.

In the United States, there are some unique restrictions related to landfill siting that are more easily managed with the use of GIS than the methods traditionally used. Proximity to fault lines must be minimized in order to prevent groundwater contamination. Fault maps are readily available for inclusion in GIS analysis. Weather conditions are also becoming a prevalent factor in landfill siting and design, specifically average wind speed and direction. Wind speed and direction data is easily imported and analyzed in GIS programs, as most weather stations are already georeferenced, usually in the form of Lat/Long coordinates, making the data more easily related to the site location.

One final aspect of landfill siting that you can manage effectively with GIS software is the preferred soils for a landfill. Soils with high-clay content are most desirable due to the low infiltration of clay-rich soils. The U.S. Geological Survey (USGS) maintains very accurate and detailed soil surveys that are available in formats available  with most GIS programs.

With the increased regulatory control of landfill siting by the federal government, and the continuing proliferation of waste, the application of GIS technology for preliminary site evaluation and even the full-scale selection process will continue to increase.

Landfill Design

Many engineering firms have augmented traditional surveying techniques with the use of GPS technology. GPS data points are easily entered into tabular format that can then be mapped in GIS programs such as ArcGIS. This layer of points can provide vertices for a vector polygon map, which can then serve as a layer for further data storage and analysis. Future expansion areas can be analyzed along with this data to determine which adjacent areas will be best suited for further development.

Another aspect of design that can benefit from GIS application is the siting of ancillary features, including maintenance shops and equipment storage buildings, as well as choosing the most efficient location of the scale(s) and scale house. When actually designing the facility the locations of these features are important. Route-mapping tools in GIS software can help the designers locate the scale(s) and scale house in a location that is relatively close to both the access road and to the landfill cells themselves; it will not be perfect for all cell locations but it can minimize maintenance costs to access roads and keep fuel costs down for the users.

Proper siting of the equipment storage and maintenance facilities are important as well because as any operator knows, heavy equipment needs constant maintenance and driving over the haul roads results in damage that must be repaired. The use of GIS software to locate the optimal or near optimal locations for these facilities can save countless amounts of money and time.

Landfill Operations

Daily operations is an area where there is a lack of GIS applications research. But there may be opportunities to use GIS in a way that benefits operators and the general public. Landfill compactor manufacturers are beginning to incorporate GPS technology into their equipment. This data then can be used to generate various maps in the GIS software. For example, with daily tabular GPS data showing where garbage was placed along with compaction rates for the day, it is possible to coordinate the boundary of the working face to create a GIS layer and over the life of a cell create a compaction map. From this compaction map you can predict possible subsidence of the cell and thus anticipate and even prevent damage to the cap and any resulting erosion problems.

Planning daily operations is another area where GIS may prove to be invaluable. Many variables impact daily operations: expected volume of incoming waste, location of the previous day’s operation, previous weather, predicted weather conditions and more. Each of these factors can be used to generate a GIS layer and then analyzed to determine the best location for the day’s working face. For example, if it’s been raining over the last few days, it is inadvisable to deposit waste in the lowest portions of the cell, but it’s also smart to avoid potentially unstable areas along the walls where you have not previously deposited waste. Using GIS layers showing the updated areas of waste distribution, the recent precipitation data and the updated slope maps you can determine the best daily operations site.

Another problem that GIS software can be used to help mitigate is wind-blown litter. As many solid waste professionals know, wind-blown litter is probably the single most aggravating problem in solid waste management. By combining wind direction and strength predictions, site contour maps and a GIS layer showing potential daily operations sites the best sight can be chosen to minimize wind-blown litter. Or, if no alternative is available, to determine whether operations should be suspended. This layer, in concert with wind direction and speed predictions and the contour maps, can also provide the operator with optimal locations for portable litter fences.

The water-monitoring programs required at most landfills could also benefit from the use of GIS software. By creating layers showing the composition of the waste mass, the locations of the monitoring wells and combining this information with water quality reports, you can create a map that will let you locate where the chemicals that are impacting your wells are coming from. This can improve response times in the event of a contaminated well and also show the public the steps you are taking to protect the environment.

Post-Closure Landfills

Once a landfill is full and capped, the work at the site doesn’t end. The decision on what final vegetative cover is one that can be analyzed using GIS applications. Vegetation coverages exist for many areas and could be used to determine what is the most common vegetation type in the surrounding area so that the landfill will blend in. It is also possible to use the final elevation maps of the closed landfill to look at the potential impact on the surface water flow and where problem erosion areas could arise off-site.

Conclusions

The potential applications for GIS technology in the field of waste management are limited only by the resources you are willing to apply. Chances are that your county or city government or even your company already has a GIS specialist or someone who is at least interested in GIS. Whether you are involved in planning collection routes, siting recycling centers or transfer stations, or in the planning and operations of a landfill, there is some aspect of your operations that could benefit from the proper application of GIS technology.

Mark Wilcox BA MS. is an environmental professional pursuing his Doctorate in industrial technology at The University of Northern Iowa.

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