King County has posted an update to their Barton and Murray (West Seattle) CSO Control Facilities Plan.
The proposals aim to control combined sewer overflows (CSOs) in two West Seattle locations, the Murray and Barton CSO basins.

Part of the Murray Basin project would mean the construction of a new 1.0 million-gallon storage tank on the east side of Beach Drive s.w. near Lowman Beach Park. Another project would be the installation of "rain gardens" in the right of way along 32 to 64 half blocks in the Sunrise Heights and Westwood neighborhoods east of 35th Ave. s.w.

The final facilities plan will be ready in summer of 2011.

Quoting from the executive summary:

"The Barton and Murray CSO basins cover 1,111 acres and 1,006 acres, respectively, along Puget Sound in West Seattle (see Figure 1.1). The basins drain to the Barton Pump Station near the Fauntleroy Ferry Terminal and the Murray Pump Station at Lowman Beach Park, respectively. The Barton Pump Station pumps flows to the Murray Pump Station. In the Barton CSO basin, the peak wet-weather flow is approximately 93 million gallons per day (mgd) and the pump station’s capacity is 26 mgd (with plans in place for increasing the capacity to 33 mgd). In the Murray CSO basin, the peak wet-weather flow is approximately 105 mgd and the pump station’s capacity is 31.5 mgd.

When flows from the basins exceed the capacity of the pump stations, the excess is discharged untreated through CSO outfalls to Puget Sound. Between the years of 2000 and 2007, the Barton CSO basin experienced an average of four untreated overflows per year. During this same time period, the Murray CSO basin experienced an average of five untreated overflows per year.

Under these requirements, CSOs must be controlled to an average of no more than one untreated discharge per year per outfall, based on a long-term average.

The full updated report, including the sixteen page executive summary referenced can be found here.

The West Seattle Herald covered this issue in early December

A larger graphic of the areas in the plan can be downloaded at the link above.