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Sewage line now skips river route

Sewage line now skips river route

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Until last month, every time a Missoulian north of the Clark Fork River flushed a toilet, the results went across the river not once, but twice.

Thirty-five years of double-crossing came to an end when Missoula City engineers blocked a pipe that carried north Missoula sewage under the river near the Russell Street Bridge. With completion of a new sewer line underneath Mullan Road, northside sewage can go directly to the city's water treatment plant instead of taking the river scenic route.

"It was simpler in those days to go into the river," City Public Works Director Bruce Bender said of the old Russell Street pipe. "It makes a heck of a lot more sense now when you see the development on Reserve Street, but there was no growth in that area in the '60s, no bridge on Reserve Street, there was nothing on Mullan Road then, either. Russell Street was the defining boundary of the city."

And for decades prior to 1963, that was where Missoulians dumped their raw sewage directly into the river. The Russell site was chosen sometime in the 1940s, when city leaders decided that river dumping sites in the middle of downtown were unsanitary.

"A lot of people are amazed that raw sewage was going into the river as late as the 1960s," said City Engineer Steve King.

In 1962, the city spent $1 million to build a water treatment plant near the site of the present-day Reserve Street Bridge. That also involved laying sewer collection pipes through the neighborhoods south of the river, including a major line along River Road and Davis Street on the southern riverbank. Engineers at the time decided it was cheaper to direct northern Missoula sewage into the bigger southside pipes with a Russell Street river crossing than lay northside underground pipes. But that meant the sewage would have to cross the river again when the River/Davis line turned north at Reserve Street to reach the treatment plant.

The plant opened Oct. 7, 1963. The Missoulian newspaper that day noted: "The beginning today of disposal operations will put an end to a long era of dumping waste into the Clark Fork. Solid waste will be removed automatically from the sewage and the water will be purified under the watchful electronic eye of the most up-to-the-moment treatment facilities available."

That under-the-river pipe was designed to handle an average flow of 10.5 cubic feet per second, or 4,700 gallons per minute of sewage. And it was prepared to handle a maximum 10,780 gallons a minute, assuming 50 years of population growth and a big flood.

"That's the amount of sewage we'd have going into the river if we ever had a catastrophic failure," King said. While the pipe appears to remain in good shape, 35 years is pushing the safe boundary of its useful life.

Nevertheless, it took an opportunistic combination of events to make closing the line possible. Development in the North Reserve Street area drew increased attention to plumbing needs in that part of town. Then Missoula County chose a site on Mullan Road for its new regional jail, and wanted it to have full sewer service. To get it, the county offered to share the cost of extending a sewer line down Mullan.

It cost $1.2 million to place a 36-inch-wide sewer pipe under Mullan Road, plus another $200,000 to replace the road itself. That job got done Nov. 12.

Bender said even at today's prices, it would cost about one-quarter that amount to build the shorter connection under the Clark Fork. However, environmental standards today are much higher for in-river work. For the same reason, the city has no plans to remove the old line from the river, preferring to leave it unmolested in its concrete shell.

Sunday - 12/6/98
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