Study calls for new line

Portland Board of Works heard a presentation from Jones & Henry engineers Thursday morning on a flood mitigation study the firm recently completed.

The study found that the best course of action for the city to take to mitigate flooding problems would be to pursue the proposed Harrison Street sewer project, which would add a new 36-inch storm sewer line that would take pressure off the Millers Branch line.

According to the study, the Millers Branch line, which drains water from a large area northeast of Portland, has been a contributing factor to flooding through the downtown area. The 72-inch line is connected to a number of other drainage pipes, and in times of heavy rain can back up into the other drainage lines, causing water to flow out of catch basins and manhole covers on Meridian Street and elsewhere in downtown.

The proposed Harrison Street sewer separation project would remove 28 connections from the Millers Branch line in areas that are prone to flooding and connect them into a new 36-inch Harrison Street line. The current Harrison Street line is a 24-inch combined sewer, which becomes “significantly overloaded during moderate to heavy rain events.”

“The installation of the new storm sewer on Harrison Street will significantly reduce the rate and volume of flow into the combined sewer system,” the study said.

The proposed project would also install check valves in the existing Millers Branch line, which would allow storm water to flow through the line in periods of mild to moderate rain fall, but in periods of heavy rain would divert excess flow into the new Harrison Street line.

“We’re taking the surcharges, as the water level surcharges in the Miller(s) Branch and storm sewers on Main, High and Arch streets, and that surcharge would be directed into the new sewer,” said engineer Brian Houghton.

The study also calls for the construction of a wet weather pump station near the intersection of Water and Harrison streets. The station would allow the Harrison Street storm sewer line to drain even when the Salamonie River is at an increased elevation from heavy rain.

Houghton said that even if the city is unable to afford to install the pump station, with an estimated price tag of $966,661, the Harrison Street sewer separation would still cause reductions in flooding in downtown Portland.

“They can build the storm sewer without the pump station,” Houghton said. “I feel the Miller(s) Branch is adding an additional 12 to 18 inches of flooding … We would be reducing the impact of the flooding.”

The Harrison Street project, not including the pump station, is already a requirement as specified in the city’s long-term control plan with Indiana Department of Environmental Management. Jones & Henry estimated that the project would cost $2.55 million, but concluded that the completion of the project would create significant storm relief for the city.

“The amount of growth, combined with the lack of infrastructure upgrades in the last few decades has led to the need for additional storm water conveyance capacity in the central area of the city,” the report said. “The Harrison Street storm sewer separation project would bring relief to the area by allowing for additional storm water to flow into the Salamonie River regardless of the level in the Miller(s) Branch.”

Also Thursday, board of works members Bill Gibson, Jerry Leonhard and Randy Geesaman approved two studies with Umbaugh.

One is a $46,000 study from Umbaugh looking at the projected revenues and finances of the city’s wastewater department. The study is part of a requirement for receiving funding from the State Revolving Loan Fund for state-mandated improvements to the city’s wastewater treatment plant. The city received a $600,000 grant to help cover costs, but will need to use the loan fund to cover the remainder of the $3.3 million improvements.

The other is an $18,000 study that will project city tax revenues for the next three to five years, accounting for new industrial development and state changes to tax formulas. Geesaman said he expects the study to take a couple of months to be completed.