The cutting head from the Elizabeth machine which cut a tunnel from Point Wells to Ballinger is lifted out of the portal in the Ballinger business district. Photo from Brightwater.
King County’s clean-water utility attained a significant project milestone over the past week as contractors completed mining on two tunnels that comprise a six-mile portion of Brightwater’s 13-mile conveyance pipeline.
The cutter head of the BT-4 machine, nicknamed “Elizabeth,” emerged through concrete shaft walls of the Ballinger Way Portal in Shoreline on June 18, marking the completion of its four-mile, 21-month journey from Point Wells.
The concrete-lined tunnel is approximately 13 feet in diameter and lies 400 feet below ground at its deepest point. Joint venture contractor Jay Dee/Coluccio/Taisei was awarded the $102 million contract in 2007 to build the west section of the Brightwater treatment plant's conveyance system.
On June 22, Central Tunnel contractor Vinci/Parsons/Frontier-Kemper completed mining on the 2.2-mile BT-2 tunnel when the machine nicknamed “Helene” emerged at the North Creek Portal in Bothell. The machine resumed mining in February after being idled for about nine months to enable repairs to a damaged cutter head wheel. Tunneling began at the North Kenmore Portal in September 2007. At its deepest point, the 14.4-foot-diameter tunnel lies about 325 feet below ground.
Construction progress on other portions of the Brightwater project remains on schedule. According to the most recent cost trend report, Brightwater construction costs are within 1.4 percent of the baseline budget established in 2004 when the project was at 30 percent design.
Photo: Cutter head of tunnel boring machine inside the shaft.
People enjoy clean water and a healthy environment because of King County's wastewater treatment program. The county’s Wastewater Treatment Division protects public health, the environment and the economy by serving 17 cities, 17 local sewer districts and more than 1.5 million residents in King, Snohomish and Pierce counties. Formerly called Metro, the regional clean-water agency now operated by King County has been preventing water pollution for nearly 50 years.
--Pictures and story courtesy Brightwater
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