A Crucial Pipeline Under Casper Needs Major Repairs

A 47,000-foot pipeline buried beneath the Casper area quietly carries the wastewater of thousands of residents — and it’s starting to show its age.

The North Platte Sanitary Sewer Interceptor, or NPSSI, begins on the west side of Paradise Valley and snakes its way underground, collecting flow from Casper, Mills, Bar Nunn, and several Natrona County water and sewer districts. It all ends up at the Sam H. Hobbs Regional Wastewater Treatment Plant on the city’s east side.

It’s a piece of infrastructure most people never think about — until it fails.

City engineers say the massive concrete pipe has been slowly eaten away by hydrogen sulfide gas, a corrosive byproduct that forms in wastewater systems. A 2012 assessment flagged the problem and recommended lining the interceptor and replacing or rehabilitating manholes to extend its lifespan.

Since then, crews have repaired about 7,000 feet of the line. Another 4,000 feet are slated for rehab in 2026. But that still leaves a daunting 36,000 feet to go — a project with a price tag hovering around $42 million.

To keep the work moving, Casper’s wastewater team, with help from Sustainable Strategies, plans to chase down some federal money. They’re applying for up to $8 million in Disaster Supplemental Grant funding from the U.S. Economic Development Administration — a program designed to help communities recovering from federally declared disasters, like Natrona County’s 2023 flooding.

If awarded, the grant would cover 80% of a $10 million project, with the remaining 20% — about $2 million — coming from the city’s Wastewater Treatment reserves. That local contribution would still leave the fund a comfortable $1 million above its minimum balance.

All told, the funding could pay for rehabilitation of more than 6,000 feet of the NPSSI — another chunk of progress toward protecting one of the city’s most critical, unseen lifelines.

City officials say the project ties directly to council priorities of maintaining a safe, healthy community; keeping infrastructure in good shape; and being good stewards of Casper’s environment and resources.