LEWISTON — A $100,000 survey might be needed to make sure Jepson Brook won’t flood in a heavy storm.
“Back when they designed this thing, the city looked a lot different than it does today,” Public Works Director David Jones said. “So we need to make sure there is capacity in it.”
Jepson Brook was built in the early 1970s to reduce flooding in the neighborhoods north of Bates College.
It’s a man-made channel of concrete for most of its length that runs under ground in several places.
The channel meanders across roughly 2.6 square miles of the northern downtown, starting at the Garcelon Bog near Farwell Street. It continues north for awhile — wandering just beyond Russell Street and the Bates College athletic fields — before crossing College Street south of Fortin Way and turning south toward the Androscoggin River. It feeds into the river just north of the Riverside Cemetery.
But it’s the area around the channel that has Jones concerned. Jepson Brook’s watershed covers 2.5 miles of dense downtown, and about one-third is paved with concrete or asphalt.
That means there’s a lot of runoff draining into the channel during heavy rainstorms or when the snow melts. City storm sewer work this summer will add to it.
“We got a call from a neighbor last fall, and he said he’d been noticing that it had been running pretty full,” Jones said. “That’s what it was built for, to address flooding issues down through that brook area. But is there a chance it could overflow? So we thought we ought to look at this thing, with all the changes we’re doing to the city.”
The survey would be paid with money from the city’s Capital Improvements program. Councilors have scheduled a public hearing on the program at its meeting at 7 p.m. Tuesday. A vote is scheduled for Feb. 21.
Much of the downtown was built with a combined sewer. Storm runoff would flow into the city’s sanitary sewer system and be treated before being released to the river. In some instances, heavy storm runoff would overwhelm the sewer treatment system, sending raw sewage into the river.
City crews have spent the last several years working to meet federal standards by removing combined sewers in neighborhoods all around the city.
Now it’s the Jepson Brook watershed’s turn. Crews are ready to start building a parallel storm sewer system in those neighborhoods this spring that will eventually send runoff from roofs, sidewalks, roads and parking lots directly into Jepson Brook.
“We are adding a lot more flow into the thing, so we ought to do a capacity analysis to make sure the flow we expect can actually go in there,” Jones said.
Jones said the survey would consist of two parts. First, the city would survey all of the hard surfaces and pavement in the watershed, estimating how much runoff they’d generate during a heavy storm. Next, the city would install flow meters in various spots along the brook’s length to see how much water is actually in the channel.