Tahoe-Truckee Sanitation Agency pivots to $310m MBR overhaul to meet strict nutrient limits

Tahoe-Truckee Sanitation Agency pivots to $310m MBR overhaul to meet strict nutrient limitsFaced with escalating rehabilitation costs and strict nitrogen and phosphorus regulations, the California utility is abandoning a piecemeal capital plan in favor of a comprehensive facility replacement that will eliminate hazardous chemical use.

A 50-year lifecycle cost analysis showed that a $310 million comprehensive MBR upgrade is more cost-effective than the $390 million required for ongoing rehabilitations.

The new facility will eliminate the use of hazardous chemicals, including highly flammable methanol and sodium hypochlorite, by transitioning to biological nutrient removal and UV disinfection.

T-TSA is targeting State Revolving Fund and WIFIA financing and has already sold a $20 million bond tranche to support initial capital needs.

Construction could begin as early as spring 2029, though alternative delivery models like Construction Manager General Contractor (CMGC) could accelerate the timeline.

The Tahoe-Truckee Sanitation Agency (T-TSA) is moving forward with a $310 million Clean Water Revitalization Project to completely overhaul its 50-year-old wastewater treatment facility. Jason Hayes, General Manager of T-TSA, presented the project details to the Tahoe City Public Utility District board on July 17, outlining the agency's shift from a piecemeal rehabilitation strategy to a comprehensive facility replacement. T-TSA, which treats between 3 and 5 million gallons of wastewater per day and is permitted for a weekly average of 9.6 MGD, operates under some of the strictest nitrogen and phosphorus discharge limits in the United States. To meet these limits, the current facility relies heavily on chemical-intensive processes, including daily deliveries of hazardous materials such as highly flammable methanol. Initially, a master plan developed by Carollo Engineers recommended a 20-year capital improvement program estimated at $116 million in 2021 dollars. However, post-pandemic inflation and the limitations of maintaining aging technology prompted T-TSA to reassess its strategy. A subsequent 50-year lifecycle cost analysis revealed that rehabilitating the existing plant over multiple cycles would cost approximately $390 million. In contrast, the $310 million Clean Water Revitalization Project offers a more economical and resilient long-term solution. The new facility will utilize a membrane bioreactor (MBR) system, relying on advanced biological processes to remove nutrients rather than chemical addition. The upgrade will allow the agency to completely eliminate the use of methanol and sodium hypochlorite. The plant will also transition to UV disinfection, a technology Hayes noted has become more affordable relative to recent spikes in chemical expenses. To finance the overhaul, T-TSA is preparing to pursue funding through the State Revolving Fund (SRF) and the federal WIFIA program once the project reaches the 30% design threshold, expected by January. The agency recently sold a $20 million bond tranche, yielding $25 million net, to support ongoing capital needs, and has approved a contract for a new rate study to address processing demands driven by increased nutrient density in the influent. T-TSA is currently evaluating alternative project delivery options. If the agency proceeds with a traditional design-bid-build model, contract documents are expected to be bid in late 2028, with construction commencing in spring 2029. However, Hayes indicated that utilizing a Construction Manager General Contractor (CMGC) approach could accelerate the procurement timeline.