9227 4TH AVE W 2024-08-12 - Laserfiche WebLink

Based on section 1-3.4.7 (MR7: Flow Control) of the 2019 Stormwater Management Manual for Western Washington construction of flow control facilities is not required for projects that: (a) The total of effective impervious surfaces is less than 10,000 square feet in a threshold discharge area; (b) Convert less than three-quarters of an acre of native vegetation to lawn or landscape; (c) Convert 2.5 acres or more of native vegetation to pasture in a threshold discharge area and from which there is a surface discharge into a natural or man-made conveyance system from the site; and (d) Projects that through a combination of effective impervious surfaces and converted pervious surfaces cause less than 0.15 cubic feet per second increase in the 100-year flow frequency from a threshold discharge estimated using the Western Washington Hydrology Model. The Western Washington Hydrology Model (WWHM) was used for the analysis. The (WWHM) analyses are shown in APPENDIX A of this report. On-site stormwater management BMPs are provided for the project site in accordance with minimum requirement 5— see MR No. 5—On-site Stormwater Management above MINIMUM REQUIREMENT NO. 8 — Wetlands Protection There are no wetland on or within 300 feet of the project site. No discharge of stormwater into a wetland or wetland buffer. MINIMUM REQUIREMENT NO. 9 — Operation and Maintenance The City of Everett requires the owner or operator of the project drainage facility to maintain the facility in accordance with the City Maintenance Checklists. The following pages contain maintenance needs for components included in the project that are part of a drainage system. Those components must be contained within the project's Maintenance Plan. The property owner shall plan to complete a checklist for all system components on the following schedule: (M) Monthly from October through April. (A) Once in late summer (preferably September). (S) After any major storm (use 1 inch in 24 hours as a guideline). Photocopies of these pages shall be used and checked off for the problems looked for each time an inspection is completed. Comments on problems found and actions taken shall be noted. Some items do not need to be looked at every time an inspection is done. The suggested frequency at the left of each item shall be used as a guideline for inspections. Drainage Report—9227 4t"Ave W Everett,WA 98204 Nov. 10,2022 Page 17