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Table 20 Groundwater Contamination Risk Maps Guidelines and Criteria Contamination Risk Pollution Source Map to Use Guidelines and Criteria 1. Sanitary Landfill Subsurface Proposed landfills should be located outside of municipal well protection zones and areas of high or extreme con- tamination risk.High priority for monitoring active and abandoned landfills should be for those landfills in areas of high or extreme risk in municipal well protection zones. 2. On-Site Wastewater Systems Subsurface The planning of rural subdivisions or developments that include large on-site systems or clusters(more than 20)of on-site systems with an average density of one house per 1- V ) n /10G j N 1.5 acres(based on the gross acreage of the development) should include an evaluation to ensure that drinking water (N N(t — CAW/VD C '(17 (Z supplies are protected.If the evaluation indicates a risk for Vienitrate levels above 10 mg/L,alternatives such as protected GLS - water supplies (well location and depth),utilizing nitrogen- reducing wastewater treatment systems,or community scale water supply and wastewater treatment systems should be explored. 3. Wastewater Lagoons and Infiltration Subsurface Proposed wastewater lagoons and infiltration areas should Ponds be located outside of municipal well protection zones and areas of high or extreme contamination risk.Existing lagoons and ponds in municipal well protection zones should be monitored. 4. Underground Storage Tanks Subsurface Stringent design and periodic testing for corrosion pro- tection and leak containment should be required of all existing and proposed underground tanks storing hazard- ous or flammable materials within municipal well protec- tion zones and in areas of high or extreme contamination risk outside of well protection zones.Existing tanks in these areas not providing adequate corrosion protection or leak containment should be immediately replaced or prop- erly abandoned. 5. Above-ground Storage Tanks Surface Strict design criteria should be required for spill or leak containment for all above-ground tanks storing hazardous or flammable materials within municipal well protection zones and in areas of extreme contamination risk outside of well protection zones.Existing tanks in these areas with- out adequate spill or leak containment should be replaced or properly abandoned. 6. Land Application of Sludge Surface Application sites should not be located in areas of extreme (Biosolids)and Septage contamination risk.Sites in areas of high or moderate risk should receive highest priority in enforcement of existing P ( / siting guidelines,and should receive increased surveillance (` to ensure applications adhere to state guidelines and criteria. 7. Wastewater Irrigation and Surface Proposed wastewater irrigation and landspreading sites Landspreading Sites should not be located in areas of extreme contamination risk.Existing and future sites in municipal well protection �f�/, 1 ` DC zones should be monitored and subject to stringent design lT C� and operating requirements. 163