| Feb. 14, 2003
News Release Consultants for King County have begun another round of soil sampling along the proposed pipeline corridors for the Brightwater wastewater treatment facilities. And they're doing it by boring holes 50 to 550 feet deep. Depending on the treatment plant location, the Brightwater system will have pipelines that carry untreated wastewater, or influent, to the treatment plant and carry treated wastewater, or effluent, to an outfall deep in Puget Sound. All soil borings are for predesign purposes only and do not mean there will be any future construction activities at the locations of the borings. To reduce environmental impacts aboveground, such as traffic and noise, the pipelines will be built in tunnels up to 450 feet deep using highly sophisticated tunnel-boring machines. "Before determining final tunneling locations, we need more detailed soil characteristics to reveal the geology, water levels, water contents, and anticipated soil reactions," said Leon Maday, project manager. "The soil characteristics will assist our engineers in anticipating the requirements for constructing the tunnels at different depths and alignments." The work crews also will be installing groundwater observation wells in the soil borings. The wells will aid in gathering data to determine water flow characteristics, levels and pressures. King County's Wastewater Treatment Division is planning Brightwater to protect public health and water quality by treating sewage from the growing number of people in the service area. About 63 percent of the wastewater will come from cities and sewer districts in Snohomish County. The rest will come from cities and sewer districts in north King County. The King County Executive's preferred Brightwater alternative includes deep tunnels to and from a treatment plant next to State Route 9 at 228th Street Southeast in unincorporated Snohomish County. The effluent tunnel would run mostly under Northeast 195th Street in King County and Northwest 205th Street, the King/Snohomish county line. A second Route 9 alternative includes a tunnel beneath 228th Street Southeast/Southwest in Snohomish County. And the third alternative, a plant at the Unocal Corp. site in Edmonds, includes a tunnel under Bothell, Kenmore, Lake Forest Park and Edmonds. About 250 geotechnical soil borings are planned during the next nine months. Each boring will last up to two weeks. Most of the work will be on weekdays between 7 a.m. and 7 p.m. Some Saturday work may take place. Most drilling sites will be on road shoulders, less-traveled streets and vacant or low-use areas of private properties near the public right-of-ways. King County and its contractors are working closely with local communities to get drilling permits and tell nearby residents about the geotechnical soil borings. To protect workers, the public and the environment, King County is requiring all drilling contractors to follow best management practices for construction projects. Such practices include using silt fencing or hay bales to capture sediment and prevent erosion. Work crews will have four to seven workers operating the drilling equipment and gathering soil samples. The most common impact will be the sound of the drill rigs, boring holes 6 to 12 inches in diameter. After the drilling work is complete, the hole will be covered to enable future observation of groundwater levels. Geotechnical borings are routine for projects like Brightwater. Similar geotechnical work took place before building the 14-foot-diameter Mercer Street Tunnel for the Denny Way Combined Sewer Overflow Control Project in Seattle and other tunnels in the King County wastewater system. For more information about the borings, call the toll-free hotline at 877-950-9995 or 711 (TTY). For more information about Brightwater, call 888-707-8571 or visit the Brightwater Web site at http://dnr.metrokc.gov/wtd/brightwater/. King County's Wastewater Treatment Division protects public health and water quality by serving 17 cities, 15 sewer districts and more than 1.4 million residents in King, Snohomish and Pierce counties.
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