February 2021 Vol. 76 No. 2
Features
Large-Diameter PCCP Installation in Louisville
By Jeff Griffin, Senior Editor
In Kentucky, the Louisville and Jefferson County Metropolitan Sewer District (MSD) has undertaken Project WIN (Waterway Improvements Now), a complete sewer improvement program to bring the MSD’s system in compliance with Environmental Protection Agency standards of the federal Clean Water Act.
An important element in the WIN program was the Lexington and Payne combined sewer overflow (CSO) interceptor that included installation of 4,339 linear feet of prestressed concrete cylinder pipe (PCCP). With pipe diameters ranging from 36- to 102-inches, the line conveys CSO into an underground tunnel for storage until it can be pumped to the Morris Forman Wastewater Treatment Plant.
Hazen and Sawyer designed the project, Garney Construction was the primary contractor, and pipe was manufactured by Thompson Pipe Group.
Alignment of the interceptor sewer is within and along the South Fork of Beargrass Creek, from East Broadway to East Main Street, in the Germantown area of Louisville.
As part of the collection of the CSOs, the scope of work included installation of the gravity flow pipe for six junction structures, seven control and diversion structures/vaults, and electrical utility services.
“Surface conditions along the route,” said Jeff Seal, Garney director, “included some areas of very hard rock, some areas of poor alluvial soils. We used sheet piling for some areas and a slide rail system. The rock was very hard – we tried trenching, chemical expansion grouting, hoe ram/hammering and finally blasting.”
Trenches were dug with a Caterpillar 335 excavator, a large, zero tail swing machine that was needed due to tight work area. Trench width and depth varied. Pipe bedding was stone, and the trench was filled with flowable back fill.
Pipe installation
Prior to installation, the pipe was stored in or near the frequently flooding creek bed. Pipe was handled and positioned with a Mi-Jack gentry crane and pushed into place with an excavator. The crane had to have the capacity to lift the pipe, plus the width to straddle the ditch/excavation, but was limited in height to clear under multiple bridges.
“The majority of the project was in Bear Grass Creek, which is an improved concrete channel,” said Seal. “During construction, flow was diverted to one side of the channel using a gravity system constructed from a slip-formed barrier wall.”
According to Kevin Baas, P.E., senior technical manager at Thompson Pipe, “Rigid PCCP was the clear choice for this project. PCCP won’t float away and is strong enough to withstand harsh installation environments. Flexible pipe requires at least four to six feet of cover and cannot be stored in areas where flooding occurs. And unlike flexible pipe, PCCP does not require special bedding or backfill.
“A post construction hydrostatic test was not a feasible option in this situation,” Baas added, “so contractor personnel air tested individual joints to confirm leak-free joints.”
The project also included extensive removal and replacement of the improved concrete channel in the South Fork of Beargrass Creek, erosion and sediment control, a vehicle access ramp and various surface restorations, such as both asphalt paving and concrete flatwork.
From start to completion, construction required two years.
With more than 3,200 miles of sanitary sewer lines in service, MSD collects wastewater from more than 270,000 homes, businesses and industries in the Louisville metropolitan area.
Based in North Kansas City, Mo., Garney Construction is one of the nation’s leading contractors for water and wastewater systems and has a regional office in Louisville.
Thompson Pipe Group offers a wide range of precast, pressure and trenchless pipes, and engineering and logistic services.
FOR MORE INFORMATION:
Garney Construction, (816) 741-4600, garney.com
Thompson Pipe Group, (972) 262-3600, thompsonpipegroup.com
Hazen and Sawyer (502) 290-6187, hazenandsawyer.com
Caterpillar, (309) 675-1000, cat.com
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