11229 19TH AVE SE SILVER LAKE TOWNHOMES WHOLE SITE 2020-07-01

r i on the list for each surface type. Infeasibility must be demonstrated accordiing to the infeasibility list in the manual for each BMP which is not selected. Based on the geotechnical report it appears that permeable pavement could be a viable option unless the soil types do not accommodate its use. Note that a geotechnical engineer's determination that soils will not infiltrate is no longer an ac eptable demonstration of in{{�easi ility unless appropriate infiltration testing is performed. / 7t - 7rovtof..act A ectt • The drainage report notes that a wet vault with 5.2 feet of dead s(orage will be used to 6rovide water quality treatment. Presumably this was intended to mean the pond shown in the southwest corner of the site. However,the plans indicate that the invert of the pond outlet is less than one foot above the bottom of the pond which will not provide adequate dead storage. If the intent was to use the stand pipe to control the water level and provide the required dead storage the pond will back water into the detention vaults. In this case any portion of the vaults below the stand pipe overflow elevation (438.14)cannot be counted toward the detention storage requirement. Since the detention pipe invert(435.70) is approximately 2.5 feet below the V overflow elevation nearly half of the detention pipe cannot be counted as detention. r e v y+e 5 s • The stormwater facilities must comply with the requirements contained in the Design and Construction Standards and Specifications (DCSS). Most notably, access and fencing must be provided in accordance with ety Section 4-4.2 and the additional requirements in Section 4-4.1(2) if the City will maintain the facilities. ro°i V The city will not maintain CMP detention tanks without the approval of the City Engineer(DCSS 4-4.1(2)-1) • The wetpond must comply with the setback requirements in DCSS Section 4-4.1(3) includingr- a 10 foot s back from property lines,and any additional setback requirements per the Zoning Code. Pro v, • The wetpond must be designed in accordance with the applicable standards included in the Stormwater Management Manual, including a two celled configuration. Provide calculations in accordance with the manual demonstrating that adequate flow path is provided. --(3‘,/ ct d Erik Emerson PE City of Everett, Public Works Senior Surface Water Engineer eemerson@everettwa.gov In addition, Planning has commented that the wet pond cannot take the place of the required landscaping buffer to be located in the front 20' setback and the 5' side setback. If this facility will be vegetated to include water based plants that meet the Type III landscaping requirements,then the pond can encroach into the front setback. However if there will not be plants located in the pond, it must be relocated outside of the required setbacks per the Zoning Code. Grace Pollard in the Planning Department can answer any questions regarding these requirements (GPollard@everettwa.gov, 425-257-8807). Thanks, Sabrina Fandler, EIT, LEED®AP BD+C City of Everett Public Works Department Development Technician 3200 Cedar St, Everett, WA 98201 Office: 425-257-8810 Direct: 425-257-7813 Email: SFandler(W)everettwa.gov liffaWitir The Permit Services Counter is located on the 2nd Floor. Hours of Operation: Monday-Friday 7:30am-12:00pm and 1:OOpm-4:OOpm.