5125 SEAHURST AVE 2022-12-06 - Laserfiche WebLink

O IVI EGA 2707 Wetmore Avenue Everett, WA 98201 ENGINEERING, INC. t 425-387.3820 f 425.259-1958 September 25th, 2019 Thad Newport Erik Emerson Engineering/Permit Services Surface Water Department City of Everett City of Everett RE: First Construction Engineering Plan Review Comments for Seahurst 6-lot SP. Permit Application #: PW1906-021 Dear Thad, This letter is intended to summarize the changes made to the, engineering package reviewed during the first plan review for this project for the public works permit application for the project located at 5125 Seahurst Ave. This letter addresses the letter and mark-ups dated 8/12/19 from you and other City staff members. Public Works: Thad Newport 1. Please see resubmitted documents and transmittal sheet. 2. Changes have been made per redlines. Checkmarks added to redlined plans if change was made and no further explanation was needed. Stormwater Reviewer: Erik Emerson 3. Revisions made per comments. See responses below. a. Section 7 of the drainage report has been revised to state that the project is below the thresholds for MR6 and MR7. Please see page 11 of the revised drainage report. b. The drainage report has been revised to clearly demonstrate the project meets all criteria for MR7 and is below all thresholds in each TDA. The data from the WWHM showing that the project meets the 0.15 cfs threshold for each TDA is now provided in Section 9 of the revised report. Since this project is utilizing infiltration trenches and permeable pavement to fully infiltrate runoff 100% up to the 100-year storm event, DOE allows for these surfaces to not be included in the developed basin area and to only model effective surfaces. Please see Section 9 of the revised report for further detail and calculations. c. Since this project is utilizing permeable pavement and infiltration BMPs to fully infiltrate runoff from the proposed roof and driveway areas and those surfaces are considered ineffective, the only effective new/replaced impervious surfaces for the project are the sidewalks, which only total 2,900 sf. Therefore, since this project is adding less than 5,000 sf of effective impervious surfaces and is below the thresholds for MR7, no further flow control is required. Runoff from the new sidewalk will be collected by the stormwater system within the right-of-way. However, the drainage report has been updated to clearly show the new impervious surfaces per TDA. The drainage plans and report have been updated to reflect these changes.