South end sewage spills into Lake
November 24, 2008 · Updated 4:20 PM
North end sewer repairs are complete
By J. Jacob Edel
Mercer Island Reporter
About 5,000 gallons of wastewater spilled into the shores of Lake Washington last Saturday due to a power outage at the South end pump station and a generator failure. At the same time, construction crews last week were able to prevent overflows on the North end while completing the emergency replacement of a new sewer line near the community center and Luther Burbank Park.
The power outage last Saturday lasted for about 40 minutes, county wastewater spokesperson Annie Kolb-Nelson said, and the overflow occurred for about five minutes. Shortly after the power outage, crews attempted to activate an emergency generator to supply power to the station. A mechanical problem with one of the generator’s electrical switches, however, disabled the reserve power supply.
During the 40 minute outage, the station exceeded its storing capacity and began to overflow into the lake, county wastewater officials stated in a press release issued Monday. After employees replaced the defective electrical switch, the generator came on and stopped additional overflow. Power in the area was eventually restored and the facility is back under normal operations.
The overflow wastewater entered the lake through an emergency outfall near two homes and county environmental lab staff took water samples and notified health and regulatory agencies. There were no beach closures because the overflow did not occur near any public beaches.
Last week, on the North end, the temporary bypass sewer line that has been in place since December has been removed now that the new underground line is operational.
To complete the connection of the new line, the North Mercer Pump Station was shut down twice, for about one hour and twenty minutes on Wednesday and Thursday, while construction crews switched over from the by pass line. The new connections were successful, according to Doug Marsano, a spokesperson with the county wastewater division said.
“Crews completed the second operation to connect the new sewer pipe, this time on the upstream end at 82nd Avenue S.E. and all operations were completed without reaching storage capacity at the pump station,” Marsano said on Thursday.
The following day, crews shut down the pump station again to flush out the bypass pipe with fire hydrant water. Then, they disconnected it at the connection point in Luther Burbank Park and began removing it.
Monica Van der Vieren, another wastewater spokesperson, said the “big, ugly bypass pipe” was gone by Monday and construction was on schedule to prevent interfering with the upcoming Volksmarch and Rotary half-marathon events.
The neighborhoods roads, however, will not be re-paved until May 15 because Puget Sound Energy will now replace an aging gas line. Temporary asphalt patches have been put in place and the South Luther Burbank parking lot will remained closed until construction crews can clean it up.
“Construction work will finish up in the south lot by the end of March, but crews will still need to restore the parking lot and surrounding area,” Marsano said. “The amount of restoration work necessary won't be known until the lot is clear of equipment and material, which is still a few weeks away.”