Monterey One Water advances $51.7m wastewater-to-RNG construction package
Monterey One Water, California · Meeting date: September 18, 2026 · Published: September 22, 2026
The committee backed the construction award to C. Overaa & Co., alongside $4.9 million of construction-management services and a $302,450 design amendment. The wider Energy Production Improvements Project is estimated to cost $73.4 million and combines digester rehabilitation, gas upgrading and new on-site power generation.
Key points
- C. Overaa & Co. was recommended for a $47.007 million construction contract, plus a 10% contingency, for a $51.708 million not-to-exceed award.
- The wider project is estimated at $73.447 million and is expected to be financed largely through an existing EPA WIFIA loan, with construction expected to take about three years.
- Works include rehabilitation of four anaerobic digesters, replacement of biogas piping, biogas conditioning, membrane upgrading to RNG, gas compression and a pipeline connection to PG&E.
- The committee also recommended a $4.884 million Phase 2 construction-management contract for Ardurra Group and a $302,450 Black & Veatch engineering amendment.
- Staff estimate RNG sales to PG&E could generate $1.9 million-$5.85 million annually, depending on production and the PG&E payment rate.
Full report
Monterey One Water’s Recycled Water Committee has recommended awarding C. Overaa & Co. a $47.007 million construction contract for a major energy-production upgrade at the utility’s Regional Treatment Plant, with a 10% contingency raising the not-to-exceed value to $51.708 million.
The Energy Production Improvements Project is designed to expand the utility’s capacity to capture, process and use biogas from wastewater solids and other organic waste streams. Its central feature is a system to condition raw digester gas and upgrade it through membrane treatment from about 60% methane to RNG containing more than 99% methane. The RNG would be compressed and delivered through a new pipeline to PG&E’s natural-gas system.
The committee’s recommendation now goes to the full board. C. Overaa submitted the lowest of three responsive bids received on 21 August, at $47.007 million, compared with $48.630 million from GSE Construction Company and $49.296 million from Mountain Cascade. The engineer’s estimate was $45 million. Staff said the bids were competitive for a technically complex project and reflected current market conditions.
The work includes extensive repairs to all four anaerobic digesters, replacement and upsizing of biogas piping, installation of gas conditioning equipment, new enclosed waste-gas flares, new gas compressors, and an RNG injection station to be designed, built and maintained by PG&E. The project also replaces the power-generation and digester-heating functions of the existing 36-year-old cogeneration system with five Mainspring linear generators and high-efficiency boilers.
Staff said the existing digester, cogeneration, flare and boiler assets are at or near the end of their useful lives. About $24 million of the construction contract is attributed to rehabilitation and replacement of those assets independently of the RNG component.
The committee also recommended a $4.884 million Phase 2 construction-management services contract for Ardurra Group and a $302,450 amendment to Black & Veatch for additional design work. The latter covers utility potholing, RNG-pipeline realignment, natural-gas pipeline upsizing, digester penetration sealing, PG&E interconnection support and revisions to accommodate a change in the linear-generator configuration.
Total project costs are estimated at $73.447 million, including engineering, construction management, PG&E works and insurance. Monterey One Water said much of the cost will be financed through an existing EPA Water Infrastructure Finance and Innovation Act loan. It also expects the project to qualify for a federal investment tax credit after completion. Staff estimate annual RNG-sale revenue of $1.9 million-$5.85 million, depending on RNG production and the rate paid by PG&E.
This summary was generated by AI based on the source document and may contain errors.
Source: Recycled Water Committee, Monterey One Water