10521 19TH AVE SE 2022-05-23 - Laserfiche WebLink

9 0 4 PUBLIC WORKS • MR #3 — Source Control of Pollution o Document the proposed location and operation of the dumpster in compliance with the City of Everett Standards, including discussion of how runoff from the dumpster area will be controlled and diverted from the storm drainage system. MR #5 - On -Site Stormwater Management o Section 2.5.5 of Volume I of the SWMM requires that feasibility be evaluated against: ■ Design criteria, limitations, and infeasibility criteria identified for each BMP in the SWMM; and ■ Competing Needs Criteria listed in Chapter 5 of Volume V of the SWMM. Based on the documentation reviewed, it does not appear that feasibility was evaluated against these criteria, as required. o Follow the requirements for using List #2 in Section 2.5.5, Volume I of the SWMM to evaluate BMP infeasibility for each surface type in the order listed for that type of surface. Use the first BMP that is considered feasible. No other on -site stormwater management BMP is necessary for that surface. Use the above criteria for evaluating and documenting infeasibility of individual LID BMPs in the Drainage Report. o Appendix III of the Drainage Report provides a bulletin -style guidance on "soil treatment options". However, post -construction soil quality and depth to satisfy MR #5 shall be implemented per BMP T5.13 design requirements in Chapter 5, Vol. V of the SWMM. MR #6 — Runoff Treatment o Document in the Drainage Report whether pollutants of concern, oil control, or phosphorus need to be addressed for Silver Lake. o StreamFilter catch basins by BayFilter are proposed to provide enhanced water quality treatment. However, that device does not appear to be an approved treatment technology based on the Washington State Department of Ecology's TAPE website http://www.ecy.wa.gov/programs/wq/stormwater/newtech/technologies.html, as required in 4-4.5(2) of the City of Everett Design and Construction Standards and Specifications (DCSS). Please provide an approved treatment method. o Page 11 of the Drainage Report indicates that StreamFilter was sized based on a 30 gallon per minute (GPM) per cartridge flow rate. Document the basis for this flow rate (e.g., basic water quality treatment, enhanced water quality treatment, etc.) and the source of that basis (e.g., Ecology's TAPE approval letter, etc.) in the Drainage Report. o Provide narrative discussion in the Drainage Report of the hydraulic design requirements for the StreamFilter and demonstrate that those requirements are met by the proposed designs. Demonstrate in particular that the CPage::3of 6