A planned wetland in far eastern Contra Costa County is not likely to affect the nearby Groundwater, a new report concludes – but it remains to be seen if that will sway some neighbors who fear the project could harm their drinking water drawn from wells.

The 645-acre wetland project aims to curb potential flooding and poor stormwater quality while fending off encroaching development and improving habitat for threatened wildlife such as red-legged frogs, fairy shrimp and burrowing owls. The undertaking officially called the Knightsen Wetland Restoration Project, is spearheaded by the East Contra Costa Habitat Conservancy and the East Bay Regional Parks District, which bought the land in 2016.

Residents will have a chance to hear about the restoration project’s potential effects on the area’s groundwater at an online community meeting on Wednesday.

To help allay some of the neighbors’ worries, the conservancy commissioned a study to evaluate the current conditions and potential effects of proposed wetlands on groundwater. The conservancy will present the findings at the meeting.

“One goal of the groundwater study was to answer questions from the community around potential changes to groundwater near residences along Eagle Lane, Byron Highway and Delta Road – particularly related to septic and drinking water wells,” said Abigail Fateman, executive director of the East Contra Costa Habitat Conservancy.

The conclusion, as outlined in the Balance Hydrologics’ report, was that overall, as currently designed, the project will not affect offsite groundwater levels in those three areas, while “effects in the north-central and south-central subparcels are small and mostly contained to within the property boundary.” It did note that the study was done during a dry year.

The project team has not yet completed the design and it can use the information from the report to make adjustments if needed, according to the consultants. The design is expected to be finished later this year and then the conservancy board will consider whether to move the project forward to the next phases, according to Fateman.

Located in the Sacramento-San Joaquin Delta east of Byron Highway, the project site was historically a mosaic of tidal marsh, wetland, sand dunes, grassland and oak savanna, with much of the property to the east of it under water before levees were built.

In recent decades, the land has flooded at times, prompting the Contra Costa County Public Works Department, along with the Knightsen Town Advisory Council, to study ways to address drainage problems in the area. One possible solution, officials say, is to direct and store stormwater, which could be naturally cleaned and filtered through the wetlands before discharge to the Delta.

However, some residents such as Carolynne Steen, who lives on Eagle Lane next to the proposed wetlands, are not convinced that the restored wetland will not harm their drinking water. Steen plans to attend the meeting to voice her reservations and hear more about the report.

“There are many of us who still think this is quite a big experiment since they have never really put a wetland in the middle of an area surrounded by properties that have wells and septics,” she said.

Steen said there is a real concern about how changing the topography of the land will affect residents’ wells in this rural community as more water is brought into the area and whether it will contaminate the groundwater.

Steen pointed to the January storms and a collapse of East Contra Costa Irrigation’s Eagle Lane canal, which caused water to overflow into the area of the proposed wetland as well as to flow back onto properties along Delta Road.

“So, all the water that’s supposed to be coming to the wetlands and going out No Name Slough, had nowhere to go and got all backed up,” she said. “Because there was already standing water, which is what they’re proposing to do, put standing water on that property.”

Trish Bello-Kunkel, a Knightsen Town Community Services director, also was concerned, noting the study was done during a dry season, and this past winter reminded them what could happen with extreme rain and tides.

“When the tides are extreme as they were recently, the water has nowhere to go but backward toward homes,” she said. “It brings me back to the recurring common sense question: Why would the wetlands’ proponents even consider breaking a levee and allowing in more water?”

Fateman, however, pointed out that that storm was a highly unusual one and the wetland site, which is yet to be built, has not been designed to hold and capture water at this point.

“That is not expected to be an ongoing situation,” she said.

Brentwood Mayor Joel Bryant, conservancy board director, meanwhile, sees the completed project as a way to deal with ongoing drainage problems while also improving wildlife habitat.

“The project is really important to give an opportunity to restore some of the habitat that has been there historically, over time, as well as give an opportunity to preserve some of our natural wetlands for our future generations,” he said.

The mayor said the wetlands project also protects the open space from future development sprawl.

“We have all seen the sprawl of development from the core Bay Area out to East County over the years in areas we never dreamed there would be development,” he said.

“I think we have to do everything we can, when possible, to preserve our open space and to preserve our communities for as good a quality of life as we can present our coming generations.”

Though some residents have also questioned whether the future wetlands would be turned into a recreation site attracting visitors, Fateman said no recreational amenities are planned.

But for Steen and others, the project still presents more questions than answers.

“So this is all an experiment. I mean, they can do their best judgments and studies of what they think is gonna happen, but nobody knows what’s going to happen until they actually do it,” Steen said.

The conservancy and parks district will host an open house and another meeting in the next several months detailing its plans for the project, which could break ground in 2025, according to Fateman.

To read the groundwater report, go to https://tinyurl.com/GroundwaterReport.

For more information on the project or to attend the upcoming Zoom meeting, go to www.tinyurl.com/Wetland-Knightsen.