Mercer Island has taken a big step in a long series to address water safety in the wake of the 2014 E. coli incident.
Due to vulnerabilities in Mercer Island’s water distribution system and a recommendation from the Department of Health (DOH) following the contamination event, the City Council approved an $810,000 capital project on July 19 to install a chlorine booster station on the north end of the Island, near the city’s reservoir.
The station will be more effective than “chucking pucks” into the city’s water supply, and “minimizes the risk of future contamination and adds to our ability to respond in the case of emergency,” according to city maintenance staff.
Some council members were concerned about the high price tag of the project, but noted that health and safety is the city’s No. 1 priority. The budget could change as design work continues.
“Utilities are expensive, and everybody takes them for granted until something goes wrong,” said council member Wendy Weiker.
The city replaces about 0.4 percent of its 113 mile system, which contains unlined cast iron pipe, in a good year, said Anne Tonella-Howe, assistant city engineer. That work costs about $1-3 million. The industry standard is 1 percent replacement per year.
The council has allocated $550,000 per year, funded through water and utility rate increases, to address the specific operating and capital improvements following the water advisory event.
The purpose of the station is to augment the chlorine residual levels in the drinking water supplied by SPU, and to “maintain a higher concentration of secondary disinfectant in the city’s distribution system and prevent coliform growth,” according to the council’s agenda bill. It would be a precise, predictable way to add chlorine to the system.
The city has taken other steps to address its water quality issues. Since the E. coli incident, the city has nearly tripled data collection efforts around water quality monitoring. Work is also underway to expand the pilot high-velocity uni-directional flushing program to help move chlorine through the water system.
The city, with Seattle Public Utilities (SPU), also plans to install a water quality analyzer at the boat launch. Construction on the booster station is expected to be completed by the end of 2018.
