Last week’s sewage spill sent at least 53,000 gallons of raw sewage into the Spokane River over a three-day period, city officials estimated.
But the actual amount could be much higher because eyewitnesses last week reported seeing what appeared to be sewage debris in the river as early as May.
The three-day estimate is contained in a letter from Dale Arnold, director of the city’s wastewater management department, to the state Department of Ecology. Tuesday was the deadline for that report to Ecology, which is conducting its own investigation and could levy fines of as much as $10,000 per day.
Richard Koch, a senior engineer with the state Department of Ecology’s water quality program, said last week that algae growing at a 24-inch sewer overflow pipe where the spill entered the river indicated that the spill had been going on for some time.
The city learned of the spill at 1:30 p.m. July 11 and had it stopped by 5:25 p.m., Arnold said in his report.
About 7,000 gallons spilled into the river during that four-hour interval, Arnold said. He estimated that the spill could total 52,920 gallons if it occurred from Sunday through Tuesday evening.
“The actual time frame of this spill is unknown,” Arnold said in the letter.
The spill occurred when the line became partially plugged with debris, apparently from heavy spring and early summer rains, Arnold said in the letter. The sewage drained from an 8-inch sewer line into the 24-inch overflow pipe. The larger pipe is designed to release water from the sewer system during heavy storms.
Sewer crews have been ordered to reroute the 8-inch line directly into a 54-inch sewer interceptor buried in Aubrey L. White Parkway.
Monitoring devices on the larger storm overflow pipe did not detect the spill.
Sewage spills are not unusual. Last year, the city recorded nearly a dozen spills during dry weather, in which an estimated 140,000 gallons of raw sewage illegally spilled into the river, according to city records.
The Spokane Regional Health District issued a health advisory for the river last week and then lifted it.
Jani Gilbert, spokeswoman for Ecology in Spokane, said any possible fines will depend on the damage to the environment, health risks, negligence and severity of the incident.
“It looks to us like this is a very good start, and the actions outlined in this letter are very appropriate,” she said of the city’s plans to reroute pipes.
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