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North Mercer Interceptor Emergency Project |
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Frequently Asked Questions
What is King County constructing on North Mercer Island?The King County Wastewater Treatment Division is replacing 2,300 feet of sewer pipe underneath Southeast 24th Street, 84th Avenue Southeast and Luther Burbank Park on Mercer Island (see map). The pipe ruptured in one section on 84th Avenue Southeast and in multiple places as a result of the December 14, 2006 windstorm. The damaged pipe is 40 years old and has reached 80 percent of its predicted service life. The pipe material, reinforced fiberglass, is difficult to repair. To ensure safe and reliable operations for decades to come and minimize impacts to the community, the county has elected to replace the entire pipe at this time. Why does King County have a sewer pipe on Mercer Island when the city has sewer service?The City of Mercer Island's sewer system collects wastewater from homes and businesses. King County receives the city's wastewater for treatment at the county's South Treatment Plant in Renton. The North Mercer Interceptor is part of King County's wastewater conveyance system on Mercer Island. King County serves Mercer Island as part of the county's regional wastewater treatment system, which protects public health and the environment by providing wastewater treatment services for 17 cities and 17 local sewer utilities. back to top Will the work disrupt my sewer service?Since homes and businesses on Mercer Island are served by the city's sewer system, no disruption of service is expected. The county's wastewater conveyance is continuing safely since crews installed a temporary sewer line to divert flows from the damaged pipe. Should you experience any problems with your wastewater service, please call 206-684-2404. How did the pipe break?The December 14, 2006 storm caused a power surge at the North Mercer Island Pump Station, which feeds into the pipe. The pump station's backup power engaged all pumps at once, creating a pressure surge that may have ruptured the pipe at weak spots underneath 84th Avenue Southeast. back to top Did the sewer pipe leak after the rupture?Wastewater overflowed into Luther Burbank Park and Lake Washington for a short time on December 20, 2006. King County staff closed the park beach as a precaution while King County water quality experts sampled surface water, the creek, and the shoreline. Samples showed bacteria levels in Lake Washington exceeded quality standards immediately after the overflow then returned to acceptable levels the next day, December 21. Following overflow events, King County notifies communities and jurisdictions and works with agencies like the Departments of Ecology and Health. The Department of Health determines when to reopen public areas. How is the new pipe going to be installed?To limit street disruptions, crews will use a technique called "pipe bursting" to install the new pipe. A tunnel boring machine lowered into the existing pipe corridor through pits in the roadway drags the new pipe into place. The machine makes room for the new pipe by breaking up -or "bursting"-- the old pipe as it moves forward. This technique allows the contractor to excavate limited areas called bursting pits instead of excavating a trench the length of the pipeline. Learn more about Pipe Bursting (pdf, Feb. 2007). back to top Who will run the project?King County has engaged a contractor to do the work. Like other sewer construction projects, King County has assigned to this project a multi-tiered project team involved in project design, permitting, construction management, and community relations. The county's operations and facilities inspection staff also support this project. The county's construction team will work closely with the contractor, city staff, neighbors, and agencies throughout the project. How was the contractor selected?Frank Coluccio Construction Company (FCCC) has completed both planned and emergency construction projects for the Wastewater Treatment Division. FCCC was able to mobilize skilled crews and equipment quickly to help King County respond to this emergency. FCCC has contracted with Buno Construction for pipe bursting work. In an emergency, King County Wastewater Treatment Division can request an emergency waiver from the County Executive to exempt projects from the County's normal bidding process. This exemption allows the county to repair critical infrastructure quickly rather than delay repairs while the normal procurement process, which can take up to a year, is underway. back to top When will the project be completed?The project began in January 2007 and is expected to last into April, although this could change as the emergency project gets underway and we learn more. Restoration of pavement will follow construction; wetland plants will be restored in the fall. Learn more about King County's Post-Construction Restoration Plans (pdf, Feb. 2007). What will the area look like when you're done?King County is committed to return the area to at least the previous condition. The contractor will restore SE 24th Street to its previous condition and overlay 84th Avenue Southeast and the entrance to overflow parking in Luther Burbank Park. All trees removed or damaged during construction will be replaced. A restoration plan for the wetland area is being developed at this time. Plans may involve using downed trees as habitat logs to enhance the wetland, stockpiling native topsoil to resurface the site, and planting native vegetation. An access path to the city's utilities in the park will be restored. back to top This FAQ list is also available as a pdf file. For more informationContact Monica Van Der Vieren by phone at 206- 263-7301 or e-mail at monica.vandervieren@kingcounty.gov for more information and answers to your questions and concerns. Back to project home page | top |
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Department of Natural Resources and Parks Updated: Feb. 5, 2007 |
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