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City outlines phased rehabilitation and slip‑lining plan for Ames transmission main
Summary
Staff described a three‑phase Ames waterline rehabilitation, identifying creek crossings already under construction, an estimated $28 million total cost, and a likely two‑phase execution based on available congressional and P3 funding; a loan or bond financing may be needed for remaining work.
City staff briefed commissioners on the Ames waterline transmission main rehabilitation project, describing active creek‑crossing work, a slip‑lining plan for aging prestressed concrete pipe, and funding options including congressional appropriation and public‑private (P3) funding.
The update is significant because the Ames/Drummond wellfield and its 30‑inch prestressed concrete cylinder pipe (PCCP) trunk supply a majority of the city's water; staff said that trunk is near the end of its useful life and requires rehabilitation to maintain supply reliability. Maralee (presenting staff member) said the overall project was originally estimated at about $28,000,000 and has been divided to match current funding availability: two roughly five‑mile phases rather than a single 12‑mile contract.
Maralee explained the two technical approaches: for two difficult creek crossings the project will install a new above‑ground or HDPE pipe segment (phase 1, currently under construction). For about 10 miles of the older 30‑inch PCCP the plan is slip‑lining — inserting a 24‑inch fusible PVC pipe inside the existing pipe in staged, roughly one‑mile segments — a method intended to reduce easement needs, shorten construction time and limit downtime. She said slip‑lining could reduce an open‑cut construction timeline of nearly 18 months to under eight months for the ten‑mile portion. Maralee said contractors quoted roughly $14,000,000 for one phase and that the city currently has about $4,000,000 in congressional funding plus $10,000,000 in P3 funding toward the work.
Commissioners asked whether reducing diameter from 30 inches to a 24‑inch internal liner would decrease capacity; Maralee said the higher allowable operating pressure and hydraulic characteristics of the new pipe would supply the same — or slightly more — usable flow. On schedule, staff said the slip‑lining contractor’s working window was described from about November through April for the slip‑lining segments, and that the bypass lines to maintain supply during construction would be above ground and quicker to install than an open‑cut bypass.
Commissioners also discussed financing. Staff said they may move forward in two phases with available funds and seek loans or bond financing for the remainder; city staff said commissioners could see action items as early as the next meeting and that discussions with long‑term bond counsel were underway. No formal vote on construction contracts or financing occurred during the briefing.
