With extended spells of wet weather hitting the Midstate this fall, Carlisle continues to make gradual progress toward fixing — as best it can be fixed — it’s recurring issue of street flooding.
Like many older, densely built communities across the county, one of the borough’s biggest infrastructure liabilities lies in its stormwater system. Many of the drainage lines beneath Carlisle’s streets are upward of a century old.
“There really isn’t a silver bullet for it,” said Borough Engineering Public Works Director Mark Malarich. “It’s a matter of numerous small projects over a period of years.”
Simply put, stormwater drainage is dependent on three factors — the size of the pipe, how smoothly it flows water, and how steep a gradient is between the entry and exit points.
Carlisle has issues with all three of those factors, depending on what area is experiencing drainage issues. Older storm drains are often small and made of rough materials that are breaking down over time, and have collected decades or even centuries of grime and sediment in their lines.
“The majority of the drains are either clay or concrete pipes,” Malarich said. “They range in age from 100 years old to just a few years. The newer pipes are steel-reinforced concrete, or plastic.”
Replacement of stormwater mains is rolled into the borough’s capital plan for sewer upgrades. Any time a stormwater line runs alongside the sewer that is being dug up, that piping is inspected and repaired, or replaced, as well.
“This summer we did major repairs to the sewer line that runs under the old Masland facility, and at the same time, because they’re adjacent, we replaced the stormwater line,” Malarich said. “Portions of that were in very poor condition.”
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The borough will continue stormwater work on the north side of town as it embarks on capital improvements around the Masland and former Carlisle Tire and Wheel properties, both of which are slated for major redevelopment projects by private investors in the coming years.
At the same time, Malarich said the borough has applied for state and federal funding on an anticipated project around Dickinson College, specifically drain lines that converge at Cherry and Louther Streets, and flow into the intersection at High Street and West Street.
“There are some road repairs we need there as well, and we would potentially combine that with a road improvement project,” Malarich said.
High and West is a “problem spot,” for the college, said spokesman Craig Layne. “As of yesterday, we sent out messaging to faculty and students that this was a flood watch situation … we caution them to not try to walk or drive through those intersections if they’re completely under water.”
In other locations, however, aging infrastructure isn’t the whole problem. Carlisle’s stormwater system flows out into nearby streams and creeks, and certain areas have less slope than others. The most problem-prone is the intersection of East High and Spring Garden Streets.
“We’re very flat, from the standpoint of our topography, so the slope of the pipes is generally low,” Malarich said. “The difference in elevation from Spring Garden around the Weiss, and LeTort Spring Run, is not that great. The pipe laying under East High Street is pretty much flat.”
Most of the downtown Carlisle area discharges into LeTort. The northwest area drains into the Conodoguinet Creek, and the extreme west of the borough, near Allen Road, has storm pipes flowing into Alexander Spring Run.