Engineers recommend 12 MGD Hilltop water plant as planning costs near $120 million; council presses for tighter estimates

Engineers from HDR told the City of Mineral Wells council that an optimized conventional design (their “Alternative 3b”) best balances cost, reliability and operations for the Hilltop Water Treatment Plant, and they recommended sizing the plant at 12 million gallons per day rather than the earlier 16 MGD concept.

Corey Shockley of HDR introduced the feasibility work and said the firm and city staff had re‑evaluated demand and wholesale contract uncertainty, which supported the move to a 12 MGD planning basis. Ashley Eastman of HDR said the team compared 10 alternatives across nonmonetary criteria such as reliability, constructability and O&M burden and ranked each option. “Alternative 3b is an optimized conventional treatment,” Eastman said, adding that the approach is similar to the existing process, is familiar to current operators and can be expanded modularly if growth accelerates.

Why it matters: HDR presented the Hilltop options as Class 5 (planning‑level) estimates, which Eastman said carry a wide accuracy range. The firm showed a construction OPCC (order of probable construction cost) for the 12 MGD optimized conventional option of about $116,000,000; the slide noted a higher total (about $120–121 million) if a construction manager‑at‑risk (CMAR) delivery method and associated fees are used. HDR emphasized these are planning numbers with contingencies that should narrow as the design reaches 30% detail and the basis of design is completed.

Council questions focused on the size of the contingency and market conditions. One council member said the range—driven by missing design-level detail such as pump horsepower, motor control counts and precise pipe sizing—was difficult to accept and worried that procurement could allow large contractor margins. HDR and staff replied that many items remain undefined at the Class 5 level and that a 4.5 or 30% estimate produced later in the design sequence will reduce uncertainty. Eastman explained the rationale for regulatory sizing: TCEQ’s 0.6 gallons per minute per connection rule and aggregated wholesale accounts push designers to size for peak days, not average daily flow.

Funding and schedule: Staff and HDR said the project will move through a preliminary engineering report (PER), a basis of design, then to more detailed design. They noted required submittals to the Texas Water Development Board (TWDB)—an engineering feasibility report (EFR) and an environmental impact document (EID)—that are part of the Drinking Water State Revolving Fund (DWSRF) process; staff said the TWDB must release design funds before certain steps, but some design work can proceed "at risk." HDR estimated that a CMAR could be onboard by year‑end under an aggressive schedule if the city chose that route.

Other components: The presentation also revisited the larger system question of a Brazos pump station and pipeline. Staff reported combined routing/pump‑station costs rose sharply when the pipeline was included; in the presentation one line stated a very large combined figure (the transcript records “nearly $175,200,000,000”), which staff acknowledged in follow‑up as an outlier and is likely a transcription or magnitude error in the record. Staff told council they are prioritizing the treatment plant and will return with refined numbers.

No council action was requested or taken tonight on the Hilltop project; staff said they will continue refining estimates with HDR and will present the PER and basis of design findings as those documents are completed.

The council was clear it wants more precise costing before any procurement decision: staff said a more defined OPCC and a 30% design phase will provide that clarity.