3618 W MUKILTEO BLVD SITE WORK FOR HARBORS EDGE TOWNHOMES 2025-10-27

SAGE HOMES NORTHWEST, LLC HARBORS EDGE DRAINAGE REPORT AUGUST 2022 2. MINIMUM REQUIREMENTS The project is a new development which proposes more than 5,000 sq. ft. of new/replaced hard surface area, and therefore is required to satisfy all nine of the minimum requirements stipulated by the SWMMWW. 2.1 MINIMUM REQUIREMENT #1: PREPARATION OF STORMWATER SITE PLANS This report, along with the accompanying plans is intended to satisfy the stormwater site plan requirements. This requirement includes research of applicable site information, evaluation of any upstream tributary drainage basins, and the downstream flowpath. These items are addressed in Section 3 of this report. 2.2 MINIMUM REQUIREMENT #2: CONSTRUCTION STORMWATER POLLUTION PREVENTION A temporary erosion and sediment control plan is provided with the final engineering drawings; a separate SWPPP report will also be provided. A stormwater pollution prevention discussion is provided in Section 8 of this report. 2.3 MINIMUM REQUIREMENT #3: SOURCE CONTROL OF POLLUTION The project is a multi -family site. See Section 5 of this report for additional details. 2.4 MINIMUM REQUIREMENT #4: PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND OUTFALLS The topography of the site generally slopes to the north and discharges to the existing stormwater system. The project intends to collect runoff from the site and route it to a stormwater management facility near the north edge of the site that will infiltrate. The overflow will discharge to the existing stormwater system, maintaining the same flowpath. 2.5 MINIMUM REQUIREMENT #5: ONSITE STORMWATER MANAGEMENT The project is required to either meet the low -impact flow control standard, or evaluate a series of low -impact stormwater management features, as outlined in the SWMMWW. This project is electing to evaluate the low impact development (LID) options from List #2; that evaluation is provided in Section 4 of this report. 2.6 MINIMUM REQUIREMENT #6: RUNOFF TREATMENT The project is subject to "basic" treatment requirements, as outlined in the SWMMWW. A more detailed discussion of stormwater treatment is provided in Section 4 of this report. 2.7 MINIMUM REQUIREMENT #7: FLOW CONTROL The project is subject to the flow control requirements outlined in the SWMMWW. A detailed discussion of the proposed flow control measures is provided in Section 4 of this report. PACE J PAGE 7