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BMP and Infeasibility description <br />applicable lists Infeasibility criteria and rationale for each <br />BMP not selected <br />T5.10B <br />❑ Site setbacks and design criteria provided in BMP T5.10B <br />Flowpath lengths <br />Downspout <br />(SWMMWW, Section V-4.1) cannot be achieved. <br />Dispersion <br />Systems <br />9 For splash blocks, a vegetated flowpath at least 50 feet in length <br />cannot be <br />achieved <br />from the downspout to the downstream property line, structure, <br />stream, wetland, slope over 15 percent, or other impervious <br />surface is not feasible. <br />9 For trenches, a vegetated flowpath of at least 25 feet In between <br />the outlet of the trench and any property line, structure, stream, <br />wetland, or Impervious surface is not feasible. A vegetated <br />flowpath of at least 50 feet between the outlet of the trench and <br />any slope steeper than 15 percent is not feasible. <br />T5.10C <br />❑ Evaluation of infiltration is not required per the Infiltration <br />Infiltration <br />Perforated <br />Infeasibility Map due to steep slopes, erosion hazards, or landslide <br />stub -out <br />hazards <br />setbacks cannot <br />Connections <br />❑ For sites with septic systems, the only location available for the <br />be met, only <br />perforated portion of the pipe is located up -gradient of the <br />location for trench <br />drainfield primary and reserve areas. This requirement can be <br />would be under <br />waived if site topography will clearly prohibit flows from <br />driveway <br />intersecting the dralnfield or where site conditions (soil <br />permeability, distance between systems, etc.) indicate that this is <br />unnecessary. <br />9 Site setbacks and design criteria provided in BMP T5.10C <br />(SWMMWW, Section V-4.1 or DCSS Section 4-4.1(3) cannot be <br />achieved. <br />❑ There is not at least 1 foot of permeable soil from the proposed <br />bottom (final grade) of the perforated stub -out connection trench <br />to the highest estimated groundwater table, hardpan, or other <br />Impermeable layer. <br />13 The only location available for the perforated stub -out connection <br />is under impervious or heavily compacted soils. <br />City of Everett Public Works <br />Small Project Stormwater Site Plan Report -Dec 2019 29 <br />