WATERLOO — Persistent heavy rainfall in recent days overloaded the city’s sewer system and let untreated sewage escape into local rivers and streams.
Waterloo Waste Management Services reported three locations where sewage escaped manholes and six more locations where city workers bypassed sanitary sewer lines into street drains to relieve pressure and prevent other spills.
A portion of the waste water reaching the treatment plant on Easton Avenue also was bypassed into the Cedar River because it was more than the facilty could handle.
“This is a long-term duration event that just never let up,” said Waste Management Services Director Steve Hoambrecker. “I’m sure we’re not the only city having these issues right now … with the saturated ground and the rivers up.”
The city is testing waste water bypassing the treatment plant and so far found readings for “total suspended solids” are below levels the city is normally allowed for treated waste water.
With some 7.74 inches of rain falling on Waterloo over the past week, Hoambrecker said the untreated waste water was heavily diluted, “minimizing the sanitary concern.”
Rain and ground water are meant to go into storm sewers, while human waste and other contaminants are channeled through separate sanitary sewer lines to be treated by the city before being discharged into the river.
Cracks in sanitary mains and home footing tiles connected to sanitary sewer drains allow ground water to infiltrate the sanitary sewer lines during periods of heavy rains, causing them to overflow into roads and ditches.
The U.S. Environmental Protection Agency brought legal action against the city in 2010 based on a large number of sewer overflows. A consent decree approved in 2015 requires the city to make major upgrades and improve maintenance operations to prevent overflows in the future.
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That consent decree also calls for fines against the city for overflows this year. But Hoambrecker noted the agreement provides exemptions when Waterloo’s rivers are above the flood stage, which they are this week.
The city has already been taking steps to improve its sanitary sewer collection system by lining pipes and enforcing a mandatory footing drain removal program in past problem areas.
Hoambrecker said the situation this week points out improvements but also shows plenty of work remains.
“Previously the Hackett Road lift state was always bypassing (in heavy rain) but it isn’t now,” Hoambrecker said. “There’s definitly been an improvement there. …Everything we’ve done has been beneficial.”
The first sanitary sewer manhole overflow was reported early Saturday morning near Bontrager Park at Park Lane and West Ninth Street.
Additional bypasses and overflows were reported Monday and Tuesday at Byrnbrae Street and Devonshire Drive; Hall Avenue and Midland Street; La Porte and East Orange roads; Pleasant Valley Drive and Letsch Road; Upland Drive and Muncy Avenue; West Eighth Street and Locke Avenue; Irv Warren Golf Course; and the 800 block of Jane Street.
The city began overflowing at the treatment plant early Tuesday morning.
The treatment plant can effectively handled 35 million gallons incoming each day. When the waste water comes more quickly, a portion is held in the 20 million gallon “equalization basin” until flows subside and it can be rerouted through the plant.
However, Hoambrecker said the equalization basin was not large enough to handle the extreme event this week.