Board takes emergency action on sewer main

An open main behind residences in the unincorporated area of the regional wastewater collection system required emergency action by the Hot Springs Board of Directors last week.

The board adopted an ordinance allowing the city to waive competitive bidding requirements and award a $160,000 contract to Coakley Co. Inc. to replace a 700-foot section and three manholes in the 24-inch diameter concrete gravity main traversing the Chase Place neighborhood off Shady Heights Road.

The main collapsed for a second time after it was repaired following an earlier collapse last month. City Engineer Gary Carnahan said the bottom half is intact and able to carry flow to the wastewater treatment plant on Davidson Drive. The top half has corroded away, leaving the main exposed.

“It’s an emergency health issue,” Carnahan told the board. “It’s a 24-inch sewer main that’s open. We’ve barricaded it off to keep people from getting in there and falling into the sewer line. There’s a piece of plywood on top, but we need to start work as quickly as possible.”

The line collapsed where the 20-inch force main from the Gulpha pump station east of the King Expressway-Malvern Avenue interchange transitions to a 24-inch gravity main that feeds the treatment plant. Carnahan told the board the mixing of pressurized air from the force main with stale wastewater in the gravity main creates hydrogen sulfide that’s corroded the reinforced concrete.

The replacement section is a plasticlike material with epoxy-lined manholes the city hopes will better withstand corrosion. Carnahan said similar circumstances have led to collapses in other areas of the 133-square-mile collection system.

“We’ve had this in other areas,” he said. “Not a lot of our sewer system is made of that old concrete pipe anymore, but time to time we have these issues that we have to deal with.”