Preserving Casper's Infrastructure: A Large Diameter Pipeline Trenchless Rehabilitation Project-Paper

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The City of Casper, Wyoming, rehabilitated critical sections of its nine-mile North Platte Sanitary Sewer Interceptor, built from unlined reinforced concrete pipe in the early 1980s. Low wastewater flows and slow velocities contributed to elevated hydrogen sulfide levels, sulfuric-acid corrosion, and severe pipe deterioration.<br /><br />Following years of inspections, risk assessment, and corrosion-control testing, the City selected trenchless cured-in-place pipe (CIPP) rehabilitation for about 7,600 feet of 48- and 54-inch interceptor. The approximately $6.7 million project also included point repairs, access-structure construction and rehabilitation, and improvements to siphon structures. Work was divided into two phases to support bypass pumping and accommodate winter conditions.<br /><br />Construction presented significant challenges: heavy sediment, pipe walls deteriorated to exposed or missing reinforcement, extreme cold, and conflicts with existing utilities. A specially designed floating scouring system enabled cleaning where conventional equipment failed. Other innovative solutions included a custom CIPP liner spanning a previously unknown change in pipe diameter and a coordinated bypass and lining approach to work around a large pipe obstructing an access vault.<br /><br />Despite temperatures reaching -30°F, the project was completed on schedule, with only one time extension for winter paving, and approximately $10,000 below the original contract amount. The rehabilitation is expected to provide reliable service for the renewed sections for up to 100 years and received the 2023 Rocky Mountain North American Society of Trenchless Technology Project of the Year Award.<br /><br />The project highlights the value of comprehensive condition assessment, early coordination among stakeholders, thorough review of historical records and utility conflicts, and flexible design and construction planning for aging buried infrastructure.

Keywords

Casper Wyoming

North Platte Sanitary Sewer Interceptor

sewer rehabilitation

cured-in-place pipe

CIPP

trenchless rehabilitation

hydrogen sulfide corrosion

sulfuric acid corrosion

bypass pumping

infrastructure renewal