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BMP and I Infeasibility criteria <br />applicable lists <br />T5.14A The following criteria can be cited as reasons for Infeasibility without <br />Bioretention further justification (though some require professional services to <br />or Rain Gardens make the observation): <br />(continued) ❑ Within 100 feet of an underground storage tank and connecting <br />underground pipes when the capacity of the tank and pipe system <br />is greater than 1,100 gallons. <br />❑ Where field testing indicates potential bioretention/rain garden <br />sites have a measured (a.k.a., Initial) native soil saturated <br />hydraulic conductivity less than 0.30 inches per hour. A small-scale <br />or largescale PIT in accordance with SWMMWW, Section V-5.4 <br />shall be used to demonstrate infeasibility of bioretention areas. If <br />the measured native soil infiltration rate is less than 0.301n/hour, <br />bioretention/rain garden BMPs are not required to be evaluated as <br />an option in List #1 or List #2. <br />❑ Where the minimum vertical separation of 3 feet to the seasonal <br />high groundwater elevation or other impermeable layer would not <br />be achieved below bioretention that would serve a drainage area <br />that exceeds the following thresholds (and cannot reasonably be <br />broken down into amounts smaller than indicated): <br />5,000 square feet of pollution -generating impervious <br />surface (PGIS) <br />• 10,000 square feet of impervious area <br />0.75 acres of lawn and landscape. <br />❑ Where the minimum vertical separation of 1 foot to the seasonal <br />high groundwater, Hardpan layer, or other impermeable layer would <br />not be achieved below bioretention that would serve a drainage <br />area less than the above thresholds. <br />❑ Within 100 feet of a drinking water well, or a spring used for <br />drinking water supply. <br />❑ Within 10 feet of small on -site sewage disposal drainfield, <br />including reserve areas, and grey water reuse systems. For <br />setbacks from a'large on -site sewage disposal system,' see <br />Chapter 246-272B WAG. <br />Infeasibility description <br />and rationale for each <br />BMP not selected <br />City of Everett Public Works <br />Small Project Stormwater Site Plan Report -Dec 2079 35 <br />