Adams County approves Arvada intergovernmental agreement to replace aging Tennyson sewer line, 5-0

The Adams County Board of Commissioners on Jan. 28 approved an intergovernmental agreement (IGA) with the City of Arvada to replace an aging sanitary sewer on Tennyson Street and increase capacity for future development, voting 5-0 to adopt the IGA (RCU-2024-12) with 36 findings of fact and two conditions.

County planning staff presented the Arvada Tennyson North Trunk Sewer Improvements Project, describing the request as an IGA submitted in lieu of an Areas and Activities of State Interest (AASI, sometimes called a 1041) permit under Adams County development standards and regulations. Jen Rudder, Planning and Development Manager for Adams County, told commissioners the project was continued from a November 2024 hearing so the city could complete additional stakeholder outreach and floodplain analysis.

"The proposed wastewater pipeline improvements are considered an AASI," Rudder said, summarizing the county’s review criteria and the work performed since the prior hearing. The project would replace an existing sanitary trunk line installed in 1962 with a 42-inch gravity sewer where the existing line ranges from 21 to 30 inches in diameter, including trenching, testing and relocation of service lines.

City of Arvada officials said the upgrade is driven by aging infrastructure and capacity needs. Jacqueline Rhodes, Director of Public Works for the City of Arvada, said Arvada, county staff and private engineers have worked closely since early 2023 to find a solution that also permits floodplain mitigation in the Square Lakes area. "We heard your comments the last hearing. We've been working on them," Rhodes said, urging approval.

Mary Stahl, Utilities Engineering Manager for Arvada, presented engineering reasoning for the city’s preferred alternative: upsizing the existing alignment to a 42-inch pipe with reduced cover in a short segment to allow the proposed floodplain mitigation. Stahl described design choices intended to reduce risk, including specifying a stiffer pressure-rated pipe with higher than normal design pressures to minimize infiltration and exfiltration and to withstand highway loads in a congested corridor.

The city and county reviewed five alternatives, city staff said: delay (deemed infeasible because the line has exceeded capacity), rerouting outside the Tennyson right of way (would encumber private property and leave properties unserved), adding a lift station (complex, costly and generally disfavored by CDPHE), the preferred 42-inch replacement with reduced vertical cover in one segment, and building a parallel pipe (would not enable the floodplain improvements). Engineers hired by a landowner, HKS, submitted a memo concluding the floodplain could be mitigated if the 42-inch alternative and related street modifications are implemented; Adams County Public Works concurred.

Mike Fiore, who identified himself as a nearby property owner with Fiore Equities, told the board he had retained engineers to analyze the floodplain and expressed appreciation that his firm’s analysis had been considered. He also asked whether the new line would serve properties outside Arvada; Jessica Morales, an attorney with the City of Arvada, explained city code generally allows utility service only to city properties and that non-annexed properties may receive service only under a city council-approved exception. Stahl added that the immediate parcels in question are within the Berkeley Water and Sanitation District, which complicates service without annexation.

County staff recommended approval with two conditions: compliance with the terms of the IGA and continued, diligent coordination between the City of Arvada, the county and property owners on the alignment and engineering variances specified in section 6E of the IGA (specifically a variance to depth-of-cover standards for the sewer segment between West 58th Avenue and Interstate 76 to facilitate the floodplain mitigation). Staff cited notification to 217 property owners within 750 feet of the right of way and receipt of one supporting comment letter from a real estate company.

Commissioners who spoke during deliberation expressed support for the collaborative process. Commissioner O'Doricio said the additional outreach and analysis eased concerns that the project would harm the Square Lakes subarea plan. Commissioner Henson called the presentation thorough and said upsizing the pipe would provide capacity and reduce risk of a sewage spill. Commissioner Mullica asked whether the design accounted for projected growth; Arvada staff said the design used build-out projections and included conservative depth standards and a sensitivity analysis.

The board approved the IGA by voice vote, 5-0. The approval authorizes the City of Arvada to proceed under the terms negotiated with Adams County, subject to the two conditions noted in county staff’s recommended approval.

Votes at a glance

- IGA RCU-2024-12 (Arvada Tennyson North Trunk Sewer Improvements Project): Motion to approve IGA with 36 findings of fact and two conditions — Passed, 5-0. - Unidentified rezoning case (applicant-requested continuance): Motion to continue to March 18, 2025 — Approved, 5-0.

The board’s approval clears the way for Arvada to begin construction as soon as contract and permitting steps are complete; Arvada staff indicated a goal of starting construction within four to eight weeks and completing work within about six to eight months. The project is financed in part by bonds the city sold in late 2022, city staff said. County and city staff said they will continue coordination with property owners, utility districts and referral agencies (including CDPHE and Xcel Energy) as the project proceeds.