The Chilmark conservation commission continued a public hearing this week on a long-running plan by the Sheriff’s Meadow Foundation to replace two culverts at the Mill Brook headwaters off North Road.

The project, originally proposed in 2016, aims to replace two small metal culverts at the headwaters of Mill Brook — a winding stream that originates up-Island beside Old Farm Road and runs down to the Tisbury Great Pond, connecting a series of small ponds in its path.

At issue is whether replacing the culvert will alter the freshwater wetland and affect surrounding wells in the area. — Jeanna Shepard

According to the Sheriff’s Meadow’s proposal, the project would replace the two pipes with a larger precast concrete culvert, as well drain 30 cubic yards of sediment from the brook area and construct a new pilot channel upstream of Old Farm Road. The project aims to restore ecological function and increase fish and wildlife passage in the brook, according to the proposal.

The culverts are located on a stretch of the brook in the Roth Woodlands — a Sheriff’s Meadow-owned property. The riverfront, bordering vegetated wetlands and land subject to flooding possibly impacted by the project, are regulated by the state Wetlands Protection Act and the town’s wetlands bylaw.

Sheriff’s Meadow, which won a grant for the project five years ago, has conducted numerous environmental studies on the site using the consulting firm Horsely Witten. An environmental notification form for the plan has also been filed with the Massachusetts Department of Environmental Protection.

But the project has elicited strong opposition and a long trail of correspondence from neighbors since its inception, many of whom worry it could have a negative impact on neighboring wells, especially a pristine water source that previously supported a spring water bottling operation. Frank Dunkl, president of Mill Brook Springs Inc., whose property on Old Farm Road abuts the project site and formerly ran the family-owned Chilmark Spring Water Co., is among the project’s most outspoken opponents.

Mr. Dunkl has fiercely criticized the plan in a series of letters since its proposal five years ago, among other things citing risk to the designated town emergency water supply located on his property as well as the impacts on the surrounding wetland. Island water expert Craig Saunders weighed in with a letter last week questioning the science behind the project. Island Grown Initiative, which owns Mr. Dunkl’s property as part of a life estate, has also registered strong concerns and asked that the project be delayed in favor of further study.

On Tuesday, the conservation commission continued a public hearing on the project to June 1. The hearing saw presentations from Neil Price of the Horsley Witten Group and Nick Nelson of Inter Fluve — a company that has also assisted in planning — outlining design plans, construction timelines and possible environmental impact.

During his presentation, Mr. Price said Sheriff’s Meadow has agreed to re-drill any wells affected by the culvert replacement to a deeper depth. “The main takeaway is that the impacts are highly unlikely and even if there are they will be mitigated,” Mr. Price said.