2600 FEDERAL AVE 2021 PORT OF EVERETT 2025-09-29

1q:1 Consulting Engineers Page 4 of 13 Table 3: EXISTING BASIN A SITE CHARACTERISTICS Area Description Area (ac) Warehouse roof and south paved 3.86 parking lot Sand backfill 0.25 Off-site Federal Avenue and paved 0.13 Port Terminal Total Basin Area 4.24 Future PUD Substation Area is located at the northeast corner of the property and will be redeveloped as part of a future Snohomish PUD project. The existing site surface characteristics and drainage patterns will be maintained as part of this project. Stormwater runoff at this location flows to the northwestern portion of the area and drains into an existing ditch adjacent to the City's Port Gardner Stormwater Facility. The project also includes pavement replacement, shoulder widening and utility construction within the Federal Avenue right-of-way. The Federal Avenue work will occur in two basins identified as basins 1 and 2. Refer to Appendix A, Figure 3 Federal Avenue Storm Drain Basin Plan for a delineation of each basin. Federal Avenue drainage generally consists of sheet and shallow flow that is collected by catch basins located within the right-of-way. The catch basins discharge to a combined sewer overflow that crosses Port property on the Dunlap leasehold. Final discharge is to SMH1995U01 and the City Port Gardner Bay outfall. At the north end of Federal Avenue, about 4,145 sf of pollution generating impervious surface (PGIS) sheet flows to Port properties to the west and north where drainage is infiltrated or collected by Port storm drain structures. 3.0 Developed Conditions Basin M developed conditions will include the installation of a paved cargo laydown yard, installation of utilities including water, sewer, power, lighting and communications, storm drainage infrastructure and treatment, and infrastructure for storage of containers and breakbulk cargo. Portions of the 39.40 acres will not be developed as part of this initial project and will remain in their existing condition See Table 4: Developed Basin M Site Area below for areas not being developed as part of this project. Stormwater improvements associated with this project have been sized for the long-term fully developed condition of this site (39.40 acres, 100% impervious surface). The stormwater improvements include the installation of a collection and conveyance system consisting of concrete gutters, trench drains, stormwater pipes, catch basins, manholes, and water quality treatment systems. Stormwater runoff will be collected and conveyed by use of trench drains, manholes, catch basins and stormwater pipes to a high flow bypass structure with an integrated lift station, where the water quality flow will be pumped to a Chitosan Enhanced Sand Filtration above grade treatment system prior to discharging to Outfall M. Outfall M will