4th South and South Trenton Storm Drain Improvements

Client: Seattle Public Utilities

DCG was the lead design firm for the $3.6M improvements including over 3,700-LF of new ductile iron storm drains ranging from 12-in to 24-in diameter with a variety of catch basin and inlet types to provide the most efficient collection of stormwater, as well as reconstruction of roads and sidewalks per SDOT standards. The project included transformation of 3.5-acres of vacant land (previously a fill site for the SR 509 project) on the Seattle Parks’ Marra-Desimone Park site into a multi-use stormwater facility. Stormwater quality treatment was enhanced through the construction of biofiltration treatment swales collected by the new stormwater mains. DCG also designed the relocation of 8-in water mains, including temporary gravity blocks to protect existing water valves and hydrants during the adjacent excavation, and temporary above grade water loops to maintain domestic water service to the residential neighborhood.