607 RIVERSIDE RD 2020-09-18 - Laserfiche WebLink

1 . Project Description The 35-acre Riverside Business Park development project site is located at 505 East Marine View Drive adjacent to the Snohomish River in Everett,Washington. This project includes the design and construction of Eighth Street with storm and utility infrastructure mains and stubs (water, gas, power, and communications)to service the interior lot developments, and public access roadside trails on the east and south sides of Riverside Road and north side of Eighth Street respectively. In the future,the trail will extend east of the new street to and along the Snohomish River front to reconnect into existing trails. Eighth Street will be designed to City of Everett standards to a length of 500 feet with a fire truck access turn-around cul-de-sac at the east terminus. The vertical profile of Eighth Street will be modified from existing elevations to collect surface drainage and facilitate rail extension from the south into Lot 5. The cul-de-sac will be raised to provide driveway access to Lot 3. Lot 5 will also have driveway access from Riverside Road similarly to Lots 2 and 4. The new street surface drainage will be collected and pumped to the Riverside Road drainage system for treatment in existing Stormwater Quality Pond 2. The overpass drainage system will be redirected for pretreatment prior to entering the second cell of Stormwater Quality Pond 2. With the overpass tributary area removed from the pumped drainage system in Riverside Road, the Riverside Road pump system will have capacity to convey runoff from the new Eighth St. The existing storm system in Riverside Road will be interconnected with drain pipes to equalize the pumps'drainage capacities and accommodate the 100-year overflow event required by the City of Everett General Transfer Agreements. The developments of Lots 2 through 5 will include their own onsite drainage systems meeting the City of Everett drainage code requirements for water quality and flow control prior to stormwater discharge into the Snohomish River through existing private outfalls. A drainage pipe stub will be extended from two existing outfalls (8- and 12-inch-diameter) east of the cul-de-sac to Lot 5. Within the 200-foot shoreline setback, these outfall pipes will be slip-lined to improve their drainage discharge capacity. The 8-inch outfall pipe, 50 feet inland, may require replacement to a new manhole structure from where a new storm pipe will be extended to provide drainage service to the Lot 5 development. An existing sewage lift station located inland from the riverbank, in the vicinity of the above-mentioned outfalls, will be relocated east of the cul-de-sac, outside the 200-foot shoreline setback boundary line. The approximate net earthwork volume from the site is 1,200 cubic-yards fill. 2. Site Assessment Topography The topography of the existing site along Riverside Road (N-S) and Riverside Road (E-W) is relatively flat, undulating between elevation 12 and 13. As Riverside Road (E-W) climbs to meet the overpass, roadway grades steepen to approximately 6 percent. The existing Eighth Street is also relatively flat with elevations undulating between 11 and 13. Approaching the Snohomish River to the east, grade falls at approximately 33 percent to an existing bulkhead. East of the bulkhead, the Snohomish River riverbank is submerged. Drainage Riverside Road (N-S) and Riverside Road (E-W) are drained by catch basins and pipes to a system of four pump stations in Riverside Road (N-S). Pump Station 1 discharges directly to the first cell of the existing Stormwater Quality Pond 2. Pump Stations 2 through 4 discharge into a single force main heading north in Riverside Road (N-S)that also outfalls to the first cell of the existing Stormwater Quality Pond 2. The existing Riverside Business Park—Public Access Trails and Roadway Improvements