Town develops aquifer protection regulations

Like many communities, Cheshire, Conn., is concerned with its groundwater. In past years, industrial solvents, pesticides and other synthetic and organic chemicals have found their way into the town’s water supply. Recognizing it is more prudent to protect wells than contend with shortages and the costs of cleanup, the town developed a wellhead protection program in 1983.

About 82 percent of Cheshire’s residents are served by its public water supply wells. Of the 2,120 acres feeding the primary wellfield, more than 500 are zoned industrial.

On this land, industrial wastewater is discharged into septic systems rather than a sanitary sewer system, almost guaranteeing contaminants will seep into the groundwater. In addition, a newly constructed major highway just north of the wellfield poses additional risk to groundwater quality because of the possibility of commercialization.

In 1983, the South Central Connecticut Regional Water Authority (RWA) began working with Cheshire to develop a multi-faceted regulatory program aimed at increasing protection of the aquifer recharge area.

“Since it was clear from the start that the program would involve existing zone changes, we decided to use a computer-generated numerical model to delineate the recharge area,” says Tom Chaplik, manager of land-use planning at the RWA. “This is the most accurate method available for determining recharge area boundaries.”

A major concern when determining recharge boundaries is the possibility of litigation. “When a town rezones a protected area to exclude certain uses, affected landowners may object or even file lawsuits claiming the value of their land has been diminished,” says Jeffrey Lennox, an associate at the Trumbull, Conn., environmental consulting firm of Leggette, Brashears & Graham, which developed the computer model for the RWA.

Recharge area determinations typically are based on peak pumpage during severe drought. But water table contour maps from which recharge areas could be determined have rarely been developed from field data for these conditions. Instead of waiting for a severe drought, a numerical model can simulate the required conditions.

This approach was useful for the Cheshire wellfield, Lennox says, since the aquifer for the wellfield had complicated boundary conditions, including two rivers and several till boundaries. “Computer models can easily take such conditions into account, thus avoiding the errors that commonly occur with other methods,” he says.

Another advantage was the model’s ability to simulate increases in pumpage from future wells. Although the existing pumping capacity of the wellfield was 2.7 mgd, an expansion to 5.5 mgd was planned.

“Since we were looking at long-term protection of groundwater quality, we wanted to determine a recharge area that would reflect this increase,” Chaplik says.

To obtain data for developing water table maps, a monitor well network was installed throughout the wellfield. Soil borings yielded geologic information and stream studies determined bottom permeabilities, width, depths and elevations. This information was used to model a drought scenario.

From this scenario, a matrix of water elevations was derived and served as the basis for a water table contour map. Recharge areas then were determined from the contour map by analyzing flow directions. The completed maps were forwarded to the RWA for use in developing the groundwater protection program.

“It was apparent from the maps that at least two protective strategies were needed,” Chaplik says. “The town would have to change the zone from high-risk industrial to lower-risk mixed use, and it would have to strengthen its existing aquifer overlay regulations to minimize the potential risk from new developments.”

Although not part of the original strategy, it was clear an ordinance to lower the risk of existing activities was necessary. An appraisal study concluded the mixed-use zone would maintain property values at current levels.

Cheshire drafted aquifer protection regulations protecting the water supply and controlling new uses. The regulations outline requirements for approval, describe certain permissible uses to be connected with public sanitary sewers and establish performance and design standards.

Developments within protected areas would be required to obtain a groundwater protection permit at the same time as a building permit, and respond to requests for information from the RWA and the local health district.

Although the process of educating the public and town officials has been an uphill one, program supporters are confident that residents will ultimately approve. “We really don’t have a choice if we want to ensure that residents will be supplied with adequate water supplies at a reasonable cost,” Chaplik says.