Ord. #125, Second Series - Revise Chapter 157 - Stormwater Management

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1) Infiltration techniques shall be prohibited when the infiltration structural BMP will receive discharges from or be constructed in areas: a) Areas that that receive runoff from vehicle fueling and maintenance areas; b) Areas where infiltrating stormwater may mobilize high levels of contaminants in soil or groundwater; c) Areas where soil infiltration rates are field measured at more than 8.3 inches per hour unless the soils are amended to slow the infiltration rate below 8.3 inches per hour; d) Areas with less than three (3) feet of separation distance from the bottom of the infiltration system to the elevation of the seasonally saturated soils or the top of bedrock; e) Areas of predominately Hydrologic Soil Group type D soils (clay); f) Within a Drinking Water Supply Management Area (DWSMA) as defined in Minn. R. 4720.5100, subp. 13, if the system will be located: i. In an Emergency Response Area (ERA) within a DWSMA classified as having high or very high vulnerability as defined by the Minnesota Department of Health; or ii. In an ERA within a DWSMA classified as moderate vulnerability unless a higher level of engineering review sufficient to provide a functioning treatment system and to prevent adverse impacts to groundwater has been approved by the City's MS4; or iii. Outside of an ERA within a DWSMA classified as having high or very high vulnerability unless a higher level of engineering review sufficient to provide a functioning treatment system and to prevent adverse impacts to groundwater has been approved by the City's MS4. g) Areas within 1,000 feet upgradient or 100 feet downgradient of active karst features; and h) Areas that receive runoff from the following industrial facilities not authorized to infiltrate stormwater under the NPDES stormwater permit for industrial activities: i. automobile salvage yards; ii. scrap recycling and waste recycling facilities; iii. hazardous waste treatment, storage, or disposal facilities; iv, wood preserving facilities; or v. air transportation facilities that conduct deicing activities. ) If volurne and pollutant management controls cannot be constructed on -site, off -site locations where the controls can be met must be identified. Guidance for best management practices and standards f`or these mitigation processes should follow the Minimal Impact Design Standards ( IDS) Design Sequence Flowchart for flexible treatment options contained in the MN Stormwater Manual. 1) For non -linear projects, where the water quality volume cannot cost effectively be treated on the site of the original construction activity, the remaining water quality volume must be addressed through off -site treatment and meet the following requirements (must be selected in the following order of preference): (a) Locations that yield benefits to the same receiving water that receives runoff from the original construction activity. 41IF''ag