Arvada officials outline $330 million plan to replace aging Arvada water treatment capacity, warn of risks if delayed

Arvada staff told the City Council on Monday night that the city needs to replace the Arvada Water Treatment Plant to keep the system safe, resilient and able to meet summer peak demand, and outlined a phased construction and financing plan with a current Class IV cost estimate of about $330,000,000.

City engineers said the Arvada plant, which is permitted at 16 million gallons per day (MGD) but does not consistently reach that level in practice, is “not designed to current standards” and that the system relies on two treatment plants — the Ralston Water Treatment Plant (36 MGD permitted) and the Arvada plant — to meet peak-day demand. Mary Stahl, utilities engineering manager, said the city’s utility-level goals are to provide water that is “safe, good, and enough.”

The master plan and follow-up studies concluded the Arvada facility should be replaced rather than repaired. Bethany Kolb, a utilities engineer, told the council that based on staff analysis and consultant input “the Arvada treatment plant will only last another 5 years before failing,” and that waiting carries risks including extended outdoor watering restrictions and possible inability to take Ralston offline for repairs without compromising service.

Why this matters: The city’s peak summer maximum day in 2024 was about 40 MGD, which exceeds Ralston’s 36 MGD; staff said two plants are required to meet peak demand and resilience goals. The Arvada facility’s constrained site, located at the toe of a dam, also limits options to repair or expand the existing footprint. Staff estimated that replacing the Arvada plant at its current site would be costly and risky — a preliminary optimistic cost estimate of $346,000,000 to rebuild in place — and added that state engineering approval would likely be required for construction within 200 feet of the dam’s toe.

Project scope and timeline: Staff presented a program-level approach to replace the Arvada treatment capacity with a new facility sized initially at 18 MGD and designed to be expandable. The project follows the city’s 2020 water treatment master plan, pilot testing completed in 2024 to validate higher-rate filtration, and follow-up siting and design work. City staff said they expect to complete the replacement capacity by February 2030 if the program proceeds on the current schedule.

Procurement and delivery: The utilities team recommended the construction-manager/general-contractor (CMGC) delivery method with an owner’s advisor on the project. Staff said CMGC provides earlier contractor involvement for long-lead equipment and better early cost visibility through contractor estimates at the 30% design stage.

Cost and financing: Chris (finance staff) told council the current Class IV estimate for the replacement program is approximately $330,000,000. Staff described a phased financing plan: revenue bond authorizations and issuances across multiple years rather than a single debt sale. The near-term plan is to issue debt this year for water and sewer funds not to exceed about $90,000,000 to fund design and early work, with additional construction-phase issuances of roughly $150,000,000 in 2027 and another $150,000,000 in 2029 under current planning. Staff said debt terms would likely be 30 years and noted program contingency factors — the budget includes a roughly 30% contingency factor at this stage to reflect Class IV estimate uncertainty.

Regulatory and operational constraints: Staff warned of several operational and regulatory constraints that limit repair options. The Arvada site is small (about 2 acres available for building), sits at the toe of dams (Ralston, Arvada and Tucker Lake), and much of the facility does not meet current safety and regulatory requirements, including space requirements around electrical equipment and the need for modern residuals handling and corrosion-control systems to comply with the Lead and Copper Rule. Staff said parts of the system use equipment that is no longer manufactured.

Alternatives considered: Staff described the primary alternatives — do nothing (defer), large-scale repair at the existing site, buy treated water from Denver Water, or build replacement capacity elsewhere — and explained weaknesses with each. They said “do nothing” risks water shortages and regulatory violations; repairing on-site faces safety, space and state-engineer approval issues; and buying from Denver Water would require changes in disinfection regime and extensive flushing or additional treatment because mixing the two systems’ water could create water quality problems.

Community impacts and next steps: Staff warned that fully funding the 10-year capital program that includes this project would materially increase typical water bills in coming years and displayed a 10-year bill-allocation chart showing substantial debt service for the construction years. Staff said they will return this spring with a revenue bond authorization request and a reimbursement resolution for prior project costs, continue rate-and-fee workshops, and bring the consulting and CMGC contracts (design and owner’s-advisor) to the council for consideration; those contracts appeared on the meeting’s consent agenda but final action is not recorded in the transcript. Staff emphasized they will continue to evaluate grant or federal funding options for later phases.

Quotes from council and staff: Bethany Kolb said, “the Arvada treatment plant will only last another 5 years before failing.” Mary Stahl summarized the utility objective: “Safe, good, and enough.” Chris summarized the cost outlook: “The current cost estimate for this project is about $330,000,000 and that is a Class IV estimate.”

What was not decided: The transcript records discussion and staff recommendations but does not show a final vote on the design or owner’s-advisor contracts, a formal bond authorization, or the final land/site selection; staff said the council is at a “land decision” point but the transcript does not include the formal action language or vote.

For residents: Staff warned that if the city pursued replacement at the existing Arvada site it would likely require multi-year outdoor watering restrictions (staff estimated roughly four years of restrictions during in-place replacement), and that choosing a replacement at a new site is intended in part to avoid that outcome.

The utilities team advised the council that the replacement program is intended to preserve service, meet future buildout demand, and reduce single points of failure in the system. Council members asked about bill impacts, contingency and phasing; staff said they will refine cost estimates as design advances and present clearer bill-impacts graphics in future workshops.