10200 19TH AVE SE COSTCO FUEL STATION 2022-05-23

/11/4/1!IIII'mA PUBLIC WORKS • A site map with all required features per Volume I, Section 3.1.7 of the Manual. • A soils map is provided,but should be updated to reflect the soils found on the project site as verified by field testing conducted by Kleinfelder or others who perform infiltration feasibility assessment of the site. iii. The discussion provided in Section 5.0.D in the SSP indicates that roof LID controls are infeasible because of vertical constraints of the existing storm drainage system, but the documentation provided does not clearly demonstrate those constraints. The documentation also indicates that perforated stub-out connections are not feasible because the proposed roof drains would connect to an existing hardline system instead. MR#5 requires evaluating LID BMPs for roof surfaces based on a prescribed order and implementing the first BMP that is not demonstrated to be infeasible for managing roof runoff. The documentation provided does not demonstrate that perforated stub-outs are infeasible. Please revisit the LID BMP selection to select the first BMP from List#1 for roofs that is not demonstrated to be infeasible per the criteria of the Manual. iv. No conveyance analysis is provided. Please address conveyance sizing by provide sizing calculations for proposed conveyance facilities or otherwise documenting that the pipe sizes will meet the City's conveyance standards. v. No sizing calculations for the oil water separator are provided. Please provide calculations for sizing the oil water separator in accordance with the Manual to ensure that it has adequate capacity. If any flow splitters are proposed to control flow rates to the oil water separator, sizing calculations for those flow splitter(s) need to be provided. Otherwise, if no flow splitters are proposed,the calculations to size the oil water separator must demonstrate that the entire flow will be treated by the proposed design. • Sheet C5.0 (Drainage and Utility Plan) -Add Required Notes for Storm Drainage Plans from Section 4-2.7 of the City's Design and Construction Standards and Specifications. • Sheet 6.1 (Construction Notes and Details) - Oil/Water Separator details appear to be generic details with no design provided. The details need to indicate pipe invert elevations and diameters, flow splitters (if applicable), etc. Per the above comment on Oil Water Separator Sizing,the details need to reflect the results of calculations performed to size the facilities in accordance with the Manual. ' Page 3 of 3