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Sec. 19. Groundwater conservation overlay district (GC). Statement of purpose. The purpose of the groundwater conservation overlay district is to protect, preserve and maintain the quality and quantity of the existing and potential groundwater supply within the city by controlling the use, storage and disposal of potential contaminants of the groundwater in areas of the city and identified significant sand and gravel aquifers and by assuring the groundwater recharge areas associated with these aquifers are protected from overdevelopment. Applicability. The standards of the groundwater conservation overlay district shall apply to any land meeting any of the following criteria: Is located above a significant sand and gravel aquifer as identified by the Maine Geologic Survey, Maine Department of Conservation, "Hydrogeologic Data for Significant Sand and Gravel Aquifers," Maps 11 and 16; or Is located within 100 feet of a significant sand and gravel aquifer; or Is located within the recharge area of a significant sand and gravel aquifer as defined by the extent of permeable stratified sand and gravel and recharging wetlands within them that drain into the aquifer; or Is located within the seasonal high water limits of any stream that flows into a recharge area of a significant sand and gravel aquifer. Where the bounds delineated are in doubt or in dispute, the burden of proof shall be upon the owner(s) of the land in question to show where they should properly be located. At the request of the owner(s), the city may engage a professional geologist, geotechnical engineer, or soil scientist to determine more accurately the location and extent of an aquifer or recharge area, and shall charge the owner(s) for the cost of the investigation. These standards shall apply in addition to the standards of the underlying zoning district in which the property is located. Permitted uses. Any use permitted in the underlying zoning district and not prohibited by subsection shall be permitted in the groundwater conservation overlay district. Conditional uses. Any use permitted with a conditional use permit in the underlying zoning district and not prohibited by subsection shall be permitted as a conditional use in the groundwater conservation overlay district. Prohibited uses. Any use prohibited in the underlying zoning district together with the following uses, even if permitted in the underlying zoning district, shall be prohibited in the groundwater conservation overlay district: The disposal of solid wastes, other than brush and stumps in accordance with Solid Waste Disposal Rules and Regulations of the State of Maine; The storage of gasoline or other refined petroleum products except as heating fuel stored within a building or accessory to an allowed use and in accordance with the standards of the Maine Department of Environmental Protection for Permitting Underground Oil Storage Facilities; The storage of road salt or other deicing chemicals; ---PAGE BREAK--- The dumping of snow brought in from outside of the district; The storage or disposal of hazardous wastes as defined by the hazardous waste regulations promulgated by the Bureau of Land Quality Control, Maine Department of Environmental Protection; Automotive and equipment service and repair shops; Junkyards and salvage yards; Cemeteries. Space and bulk standards. Any building, structure or use of land within the groundwater conservation overlay district shall comply with the following requirements in addition to the space and bulk regulations of the underlying zoning district: TABLE INSET: Additional standards. Any building, structure or use of land within the groundwater conservation overlay district shall comply with the following requirements: Timber harvesting. a. Over any ten-year period, harvesting shall not remove more than 50 percent of the volume of trees over four inches in diameter. For the purpose of these standards, volume may be considered equivalent to basal area. b. Burning of slash is prohibited. Export of woodchips to wood-to-energy plants or on-site chipping and broadcast application to the land are recommended for slash disposal. Agriculture. a. Land application of sludge and spray irrigation of industrial wastewater or sewage are prohibited in the groundwater conservation district. b. Manure spreading is permitted if carried out in conformance with a conservation plan which meets the standards of the state soil and water conservation commission and is approved by the Androscoggin Valley Soil and Water Conservation District. The conservation plan must include provisions for control of surface water runoff and nonpoint source pollution. Animal husbandry. a. Animal husbandry and associated manure handling must be carried out in conformance with a conservation plan which meets the standards of the state soil and water conservation commission and is approved by the Androscoggin Valley Soil and Water Conservation District. The conservation plan must include provision for control of surface water runoff and nonpoint source pollution. Impervious surface. ---PAGE BREAK--- a. The impervious surface ratio for nonresidential uses may be increased if a groundwater study prepared by a groundwater hydrologist demonstrates that such increase will not have an adverse impact on either the quality or quantity of groundwater or that proposed mitigation measures will result in there being no adverse impact to either the quality or quantity of the groundwater. Industrial and commercial uses. a. Facilities shall be designed so that all stored, spilled or leaked hazardous materials are contained on-site; b. Facilities shall be designed so that no stored, spilled or leaked hazardous materials can infiltrate into the ground; c. Permanent disposal of any waste containing hazardous materials shall not be allowed on-site; d. Interior floor drains shall not be directed to any stream, storm drain, dry well or subsurface wastewater disposal system. They shall be directed to holding tanks, treatment systems or the public sewer system; e. Above ground storage tanks for hazardous materials shall be located within a diked area which is impervious to the substance(s) being stored and large enough to contain the entire contents of the tank(s); f. Storage areas for drums shall be contained within a diked area which is impervious to the substances being stored. All drums shall be stored in product-tight containers which are protected from leakage, accidental damage and vandalism; g. Commercial or industrial activities which have uncovered storage areas shall have specially designed stormwater drainage facilities which provide for disposal of stormwater in a manner that will not adversely affect groundwater quality; h. Dumpsters used to store industrial or commercial wastes shall be covered; i. The design of storage and containment storage shall be approved by the city engineer for conformance with standard engineering practice. Subsurface wastewater disposal systems. a. In areas which are not served by public sewer, no more than one dwelling unit may be connected to a subsurface waste disposal system, and no "engineered systems" are permitted unless a full hydrogeologic study which examines the specific groundwater impacts of the proposed system indicates that there will be no off-site impacts on groundwater quality. The study must be conducted by a state certified geologist with proven experience in hydrogeology. b. Disposal of hazardous materials to wastewater disposal systems is prohibited. ---PAGE BREAK--- Earth material extraction. a. Extraction shall not be allowed below the average seasonal high water table. No ditches, trenches, pumping or other methods shall be used to artificially lower the water table to permit more gravel extraction than could occur under natural conditions. b. All petroleum products shall be kept out of the pit. If refueling and oil changes must be conducted in the pit, a special area must be constructed that would prevent the maximum possible spill from entering the ground. Absorbent pads shall be kept onsite to be used immediately, should any petroleum products be spilled on the soil. c. The pit shall not be used for storage or dumping of any substances that could produce a harmful leachate. d. Any washing or crushing operations shall be conducted in a manner that will minimize runoff and evaporation. e. Access and haul roads into and around the pit shall not be oiled or salted. f. Access to the pit shall be strictly controlled at all times with locking gates. When the pit is permanently closed, all vehicular entrances shall be made impassable. g. When the pit is permanently closed, it shall be loamed and seeded. Application of fertilizer, manure or other soil amendments to bare soil whose topsoil has been removed is prohibited. Pesticides and herbicides. The application of pesticides and herbicides for nondomestic or nonagricultural uses shall be carried out with all necessary precautions to prevent hazardous concentrations of pesticides and herbicides in the water and on the land within the groundwater conservation district as a result of such application. Such precautions include, but are not limited to; erosion control techniques, the control of runoff water (or the use of pesticides having low-solubility in water), the prevention of volatilization and redeposition of pesticides and the lateral displacement (i.e. wind drift) of pesticides. Development approval. All nonresidential projects requiring development review shall prepare a groundwater protection plan which shall identify proposed measures for protecting the groundwater from adverse impacts from loss of recharge capacity, exfiltration from sewer pipes and contamination by oils, chemicals or nutrients. (Ord. No. 92-5, 3-5-92; Ord. No. 00-19, 10-5-00) Editor's note: See editor's note at article XI.