SEATTLE CITY LIGHT DECANT FACILITY
This new facility in Seattle provides City Light with its own vactor vehicle dump site for decanting, filtering and treating to meet environmental discharge requirements at the South Service Center. The facility accepts electrical vault hydro-excavation waste from vactor trucks within the utility’s service area and contains both indoor and outdoor use areas.
Outdoor areas include sloped concrete pads, adjustable gates, and baffled vaults for sediment retention and settling. The facility also contains an indoor treatment room that includes equipment designed for additional sediment filtration, oil and grease separation, an automated backwash filtrating system, activated carbon filtration, and small workstation for record keeping and water sample preparation. After completing the treatment process filtered water is then temporarily stored in two 4,000 gallon holding tanks for testing and, ultimately, discharge to the sanitary sewer system.
The project also includes the design and construction of a 4,500 SF vehicle storage building.
The facility is located on a large, developed site and will replace already existing permeable surface. The building foundation includes auger-cast pilings and grade beams, and the exterior concrete and metal materials. The facility was designed to be low-cost and low-maintenance with an emphasis on reliability and successful sediment and contamination removal.
The entire project was conducted within 8 weeks, and facility design began with a site alternatives analysis. The scope of the project includes complete construction documents, specifications, start-up and commissioning assistance and additional facilities including indoor vactor truck storage.