9600 SHARON DR EXPLORER MIDDLE SCHOOL 2022-03-11

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