01-03-1985 Council Packet Special Meeting

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bedrock formations and the major river systems. These and other geologic features cause vertical movement between aquifers. A;1 of the aquifers are used for drinking water to some extent. The Metropolitan Council recognized the importance of groundwater protection in its Water Resources Policy Plan Guide Chapter adopted in 1973. Policy 29 of this plan states that "solid waste disposal sites must be designed and constructed so as to preclude contamination of groundwater. Existing facili- ties which are polluting the groundwater should be corrected or eliminated". It is now widely recognized that engineering controls such as liners and leach - ate collection systems must be used in new or expanded land disposal facilities to more adequately protect groundwater. Liners are intended to retard leachate seepage and provide containment for collection. Liners are usually made of recompacted clay soils or synthetic fabrics. A leachate collection system is a series of perforated pipes underlying the waste but overlying the liner to allow removal of accumulated leachate. Once collected and removed, leachate must be treated at the site or at a sewage treatment plant. Discharged leach - ate must meet the same effluent quality standards as other sources of indus- trial sewage waste. Compacted, low -permeable soils covering the top of the disposal facility will limit infiltration of water into the waste material. Installation of monitoring and a regular samplinS program can determine the extent of any leachate migration from the site. Land disposal facilities containing unprocessed waste high in organic materials can produce other environmental impacts including explosive, toxic and asphyxiating gases. Methane, a principal component of landfill gas, has been known to accumulate in explosive concentrations and result in damage to persons and property. Landfill gas can be controlled by one or more of the following techniques: 1) lining the site with materials that bloc% the subsurface flow of gas to adjacent land or into buildings off the site; 2) selectively placing material to vent and/or collect gay; and 3) pumping wells to evacuate and vent, burn or process the gas for sale However, for some wastes, engineering controls alone are not adequate protec- tion. The first and primary means of protecting surface and groundwater resources should be the selection of locations that have hydrogeologic char- acteristics, soils, and other natural features that will contain any leachate that escapes engineered control systems. Some soils are better suited for attenuating leachate, or, in other words, reducing its potency. Favorable land disposal locations include areas with thick deposits of low permeable soils and few connections with usablc water supplies. Processing Facilities Solid waste processing facilities include combustion units that recover energy, facilities that prepare the solid waste into a fuel that can be shipped (RDF ), composting facilities and transfer stations. The potential environmental impacts will vary dependiny on the type of facility, waste feedstock and output products. Combustion facilities emit a wide array of substances into the air. The type and quantity of these emissions depends on the furnace type, fuel composition, and operational factirs. Federal and state air quality standards have been developed for trite-•ia pollutants (carbon monoxide, sulfur dioxide, particu- lates, nitrogen ox'.des, ozone, hydrocarbons and lead), and federal emissions