The fast-flowing Spokane River has already flushed and diluted most fecal matter from Monday’s sewage plant accident, water quality samples show.
The first samples from the river were obtained Tuesday at the T.J. Meenach Bridge, the Bowl and Pitcher Bridge and the Seven Mile Bridge. Laboratory tests of fecal coliform bacteria counts in the water samples were released late Wednesday by Spokane’s Department of Wastewater Management.
The results “indicate to me that on Tuesday there was no significant impact to the river” from the rupture of a 2-million-gallon tank full of sewage sludge the day before, said Michael F. Coster, laboratory supervisor for the city’s Department of Wastewater Management.
On Tuesday, city officials estimated that about a tenth of the tank’s contents — 200,000 gallons — may have spilled onto the ground or into the water. They haven’t provided a more precise figure.
Fecal coliform is measured in counts per 100 mils of water — just over a cup. In sufficient concentrations, it can be a health hazard because it contains harmful pathogens that can sicken people.
But the concentrations in the Spokane River were low, the monitoring data show.
At the T.J. Meenach Bridge upstream of the Spokane Advanced Wastewater Treatment Plant, fecal coliform counts in the first set of samples were very low, at 8 counts per 100 mils. They were slightly elevated at the Bowl and Pitcher Bridge at 50 counts downstream of the plant, but that is still far below any level of health concern, said Michael LaScuola of the Spokane County Regional Health District. At the Seven Mile Bridge, the count dropped to 17.
Fecal coliform levels of up to 100 counts per 100 mils is permissible at bathing beaches under state health guidelines. “If the count is over 100, we’ll begin to warn bathers,” LaScuola said.
A second set of water samples from Tuesday afternoon showed even lower bacteria levels: 7 counts at T.J. Meenach; 4 counts at the Bowl and Pitcher Bridge; and 11 counts at Seven Mile. Coliform levels dropped to less than 2 counts at the Lake Spokane boat launch near the Little Spokane River.
If additional samples taken Wednesday and available today show similar or lower counts, health district officials may decide to take down their warning signs posted along the Spokane River, LaScuola said. Regional health district officials posted the signs warning of river contamination on Tuesday and said they’d likely stay up until Friday.
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