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Upgrading aging, underfunded water infrastructure in rural Mariposa County

Mariposa County

Mariposa, CA

Mariposa County needed a long-term solution to improve the county's aging water & wastewater infrastructure. They implemented a plan to reduce O&M costs, employ facilities managers & justify rate increases for residents in rural areas. The plan was informed by a Condition Assessment of the facilities' criticality.

Topics Covered

Waste Management
Water Quality
Fiscal Uncertainty


Initial: 150 Thousand USD


Federal grants

Project Status

Operational since 2017

Gov Champion

County Manager

Problem Addressed

Mariposa County needed a way to cover the projected costs necessary to sustain its underfunded water and wastewater infrastructure 

Mariposa County is nestled in the western foothills of the Sierra Nevada.

Residents live in rural areas or small communities with a median household income of approximately $45,000 or lower. Mariposa County’s entire water and wastewater infrastructure, as well as operations and maintenance (O&M), was severely underfunded. The county had not increased water or wastewater rates in over ten years. As a result, they did not have a savings or capital improvement fund stocked well enough to hire adequate personnel to maintain equipment and offset maintenance costs.

All but one of the County's facilities had been operating at a loss since fiscal year 2015 or earlier. Local leaders needed a long-term sustainable path to negotiate through the issue. The County sought out a solution to cover the necessary projected operations and capital costs in order to sustain the existing water and wastewater infrastructure for the next ten years.

Solutions Used

Mariposa County commissioned a condition assessment of the county's facilities that helped access funding and improve operations. 

Mariposa County relied on Pinnacle to perform an asset inventory for each of the county’s districts.The designers, operators, and engineers assigned to the project had experience in some of the most challenging and high-risk facilities in the country. Over a three-year period, Pinnacle’s expertise combined with the design engineer’s familiarity of local facility operations ensured an efficient and reliable assessment of Mariposa County’s facilities.

Pinnacle provided a Condition Assessment report based on their findings and provided recommendations to improve conditions. During the process interviews, Pinnacle went line-by-line to identify one-time opportunities that were big savers in both budget and job security. Additionally, the report proposed the County adopt a rate increase for all county communities. Second, it identified potential funding assistance programs to facilitate the necessary studies and subsequent capital improvements. And third, for the County to adopt the proposed staffing recommendations to balance the resources required to maintain all facilities.

In order to justify a rate increase, Pinnacle’s Condition Assessment included recommendations to mitigate the impact on Mariposa County’s year-round residents who would be financially impacted by the increase. First, to gradually increase the rates over a five-year period. And second, to implement a transparent public outreach strategy, including flyers and community meetings to explain the reasons and cost basis for the proposed rate increases.

During a site visit, Pinnacle's team focused on reviewing equipment conditions, maintenance practices, documentation, and biochemical conditions that characterize process reliability. They provided both general information regarding asset condition, and an overview of O&M documentation and recommendations for improving the current state of the O&M water services program. Although each facility was burdened with its own challenges, including accessibility issues, aging assets, design flaws, and low influent loading, they all shared common problems in documentation and accountability of O&M practices.

Pinnacle also identified that insufficient labor was employed to operate and maintain the facilities. This lack of time and resources was partially responsible for failures of documentation required to sustain the functionality and performance of the facilities in question.



Mariposa County was able to justify residential water and wastewater rate increases in two districts, increasing residential monthly rates by 100% in the first year.


The Condition Assessment report justified the County's staffing needs and provided accurate recommendations on how many operators should manage each facility.


Pinnacle provided a data-informed set of recommendations to craft a Capital Improvement Plan based on the findings of an existing RCM analysis determining the criticality of equipment.


The County received a Final Tech Report outlining the assessments and criticality of all tech equipment, as well as a data-informed rate comparison study.

Who Should Consider

Small or medium-sized Counties that require justifiable funding to improve water and wastewater facilities.

Last Updated

Mar 25th, 2022

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