6101 23RD DR W NORPRO 2025-07-29

Site Development Plan The proposed development consists of the construction of a new office/warehouse building on an undeveloped 3.5-acre site at 2215 Merrill Creek Parkway in Everett, Washington. The new 34,100± SF building will be located in the western portion of Lot 3B-1. Proposed improvements include stormwater management facilities, utilities and on-site landscaping. The site drains to two separate drainage basins as described in the Basin Summary section of this report.. In the developed condition, runoff will be routed in a manner that maintains existing drainage basins as discussed below. Narbeck Creek , Flow control and treatment is required for runoff in the Narbeck Creek drainage basin. A detention tank is proposed for flow control. All runoff tributary to the detention tank will be from the non- pollution generating surfaces, therefore, no water quality measures are proposed for the Narbeck Creek drainage basin. Powdermill Gulch Creek The majority of the site drains to Powdermill Gulch Creek. Since there is a regional detention facility that is sized to detain runoff from the site, no onsite detention is required for this drainage basin. Runoff from the main project site will be conveyed via sheet flow and an underground conveyance system to a presettling structure prior to a StormFilter for water quality treatment. Runoff from the small parking lot to the south will be routed to a StormFilter catch basin for water quality treatment. After water quality treatment, the water will be discharged to the public system within 23`d Drive W, which will convey the clean runoff to the detention pond. See Exhibit B - Developed Conditions 1 1 1 1 1 1 1 6/16/2011 Stormwater Site Plan Page 10 1