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<br />to prevent adverse impacts to groundwater has been approved <br />by the City of Arden Hills. <br />4. Areas within 1,000 feet upgradient or100 feet downgradient of <br />active karst features; and <br />5. Areas that receive runoff from the following industrial facilities <br />not authorized to infiltrate stormwater under the NPDES <br />stormwater permit for industrial activities: <br />a. Automobile salvage yards; <br />b. Scrap recycling and waste recycling facilities; <br />c. Hazardous waste treatment, storage, or disposal <br />facilities; <br />d. Wood preserving facilities; or <br />e. Air transportation facilities that conduct deicing <br />activities. <br />ii. Filtration System <br />1) Filtration options include, but are not limited to: sand filters with underdrains, <br />biofiltration areas, swales using underdrains with impermeable check dams and <br />underground sand filters; <br />2) Must not install filter media until the contributing drainage area is constructed and fully <br />stabilized unless they provide rigorous erosion prevention and sediment controls (e.g., <br />diversion berms) to keep sediment and runoff completely away from the filtration area; <br />3) Designed to remove at least 80 percent of TSS; <br />4) Must use a pretreatment device such as a vegetated filter strip, small sedimentation <br />basin, water quality inlet, forebay or hydrodynamic separator to remove settleable <br />solids, floating materials, oils and grease from the runoff to the maximum extent <br />practicable, before runoff enters the filtration system; <br />5) Designed to provide a water quality volume as described in Section b.iii, b.iv, and b.v; <br />6) Designed to discharge all stormwater(including stormwater in excess of the water <br />quality volume) routed to the system through the uppermost soil surface or engineered <br />media surface within 48 hours. Additional flows that the system cannot filter within 48 <br />hours must bypass the system or discharge through an emergency overflow; <br />7) Designed to provide a means to visually verify the system is discharging through the <br />soil surface or filter media within 48 hours; <br />8) Employ appropriate on-site testing to ensure a minimum of three (3) feet of separation <br />between the seasonally saturated soils(or from bedrock) and the bottom of the proposed <br />filtration system;