Oak Hill neighbors express concerns as Petaluma plans for new well

Petaluma residents neighboring a planned groundwater well project in the Oak Hill Park area are asking city leaders for more transparency and review before approving its construction, following concerns that the area’s foundation may be too fragile.

The Oak Hill Municipal Well Project would install a well on a 5.58-acre, city-owned property at 35 Park Avenue, as city officials look to offset the need for purchased water and increase the reliability and diversity of local water supplies during the ongoing drought.

But neighbors are concerned the well will have a negative impact on the environment and make way for sinkholes.

“The neighborhood homeowners have worked diligently to preserve the integrity of their homes in this beautiful, historic area of our city,” said Elizabeth Hooshiar and Jonathan Malanche in a letter posted to the city website. They added many residents there have had to install costly French drains and sump pumps for flood water diversion over the years. “All of the solutions we’ve worked so hard to put in place to sustain this naturally water-rich hillside seem threatened right now by the prospect of lowering the water table and creating a new plethora of problems for us. It’s frightening.”

The project site is located north of Bodega Avenue and west of Howard Street, and is bordered by Oak Hill Park to the east and by residential areas to the north, south and west along Laurel Street, Amber Way, Wallace Court and Park Avenue.

The well would would be drilled to a depth of about 500 feet, with a capacity to pump about 200 to 400 gallons per minute. It would be housed in a below-ground vault near a custom treatment shed that holds equipment for groundwater sanitation.

“In the current plans, the well pump house is a small 12x14 foot wooden structure adjacent to the decommissioned Oak Hill Reservoir above the proposed well,” said Ingrid Alverde, the city’s director of Economic Development and Open Government, in a Wednesday afternoon email. “We plan to construct the well pump house in such a way as to retain the current popular walking path around the reservoir.”

The project comes after Petaluma officials reached an agreement with Sonoma Water, where the city would “maintain the ability to deliver up to 40% of the maximum monthly water demand in case of an emergency or drought,” which totals about 4 million gallons per day. Petaluma in 2016 completed two wells, the Park Place and Willowbrook wells on the city’s east side, to meet water production capacity goals.

In 2019, the city hired West Yost Associates to help identify potential well locations throughout the city. In determining potential sites, the group’s study considered factors such as whether sites were city-owned parcels, proximity to the water distribution network and to existing utilities, potential groundwater aquifer yield and potential water quality issues. Potential sites were narrowed down to three – Oak Hill, Magnolia and Paula Lane. Later in 2021, the Oak Hill site was ranked as the top choice, based on factors including life cycle costs and site constraints.

The City Council was looking to approve the Oak Hill well in a June 20 meeting, but pushed back approval after a public hearing determined that neighbors needed more appropriate outreach, after many said they had not been personally notified of the project. A community meeting is now expected for mid-August to update residents on the project’s process and make room for more discussion.

Petaluma resident Vicki Dufton said her back fence lies right next to the Oak Hill reservoir.

“It affects me very directly,” Dufton said in a Wednesday afternoon phone interview. “And I have a big concern about drilling at the top of our hill and how that’s going to affect the foundations of our homes, the security of our homes.”

Melissa Abercrombie, a resident of the neighboring Wallace Court, expressed similar uneasiness about the project.

“Our hill needs all the stabilization it can retain,” Abercrombie said in a letter to the city. “In the past few months, there have been increased cracks/buckling in the asphalt following years of drought and slippage.”

Alverde assured that the well has several design considerations that will alleviate concerns regarding groundwater depletion and impact to nearby foundations. That includes the 100-foot-deep concrete sanitary seal around the well, she said in an email, which prevents the well from directly drawing groundwater from the upper aquifer, which has the most impact on shallow groundwater depletion and possible land subsidence.

Alverde added that a full environmental review has been completed and found the project will not have an overall negative impact on the area. Staffers are currently looking to obtain confirmation of the project’s compliance with the California Environmental Quality Act.

An initial study, published April 25 in collaboration between city staff and architectural engineering company GHD, noted that construction activities for the well have the potential to degrade water quality from discharge to the local storm drain system as a result of erosion, which is considered a significant impact. However, the City proposed implementing water treatment mitigation measures during construction, to lessen the impact.

The study found the project would have a less-than-significant effect, with mitigation measures, on human life, fish and wildlife. Reports also say that no heritage trees in the park area would be removed as a result, and the project should have little to no impact on flooding, but could result in construction noise.

A geotechnical study was also performed to evaluate potential earthquake hazards and identified appropriate foundation supports to be used for the well treatment building. Overall the study found that there would be minimal seismic consequences from the well.

The estimated cost – including planning, design, administration, construction and management – totals nearly $3 million, according to a June staff report. Construction is expected to take two to three months, Alverde said.

Water from the well would only be used on an “as-needed basis” – in emergencies and times of severe drought. The amount of extracted groundwater is expected to reach no more than 215 acre-feet per year, according to city reports.

It is unknown when the project will come back before the City Council for approval.

Amelia Parreira is a staff writer for the Argus-Courier. She can be reached at amelia.parreira@arguscourier.com or 707-521-5208.