seattle public utilities cso outfall replacement project

The Watershed Company conducted water quality monitoring during in-water construction for the Seattle Public Utility CSO 171 Outfall Rehabilitation Project. Turbidity and temperature monitoring took place October through December 2019 in Lake Washington near Chinook Beach Park. The Watershed Company monitored turbidity and temperature according to the terms and conditions provided in the Water Quality Monitoring and Protection Plan (WQMPP) for this project (The Watershed Company 2019). 

Monitoring occurred each day when in-water construction or sediment-generating activities were being conducted. Turbidity measurements were taken using a HACH 2100Q turbidimeter. Background samples were taken at three locations outside of the 150-foot work zone as described in the WQMPP. Compliance monitoring locations were situated at two locations within the 150-foot work zone.

Excellent communication between the contractor, on-site SPU engineer, and The Watershed Company biologists facilitated lower exceedance times and fewer occurrences, reducing effects on water quality.  No exceedances occurred during actual in-water work, including during the final removal of the turbidity curtains.

SERVICES

• Water quality monitoring

• Turbidity and temperature monitoring

• Compliance monitoring