Horsley Witten Group — a Sandwich-based environmental science and engineering firm — and senior hydrogeologist Neal Price will conduct the studies and tests deemed necessary to determine the proposed Fearing Hill solar project’s potential impact on stormwater runoff in the area. 

The studies are needed to answer a number of the Planning Board’s remaining questions about the Fearing Hill solar project. Board members said the project could not be approved without a hydrogeologist’s analysis — currently, they said, the applicant’s paperwork is incomplete. 

The proposed 20-acre solar array, to be located on a 44-acre site at 91 and 101 Fearing Hill Rd., has drawn intense criticism from the public over the past few months.  

During a meeting on Aug. 16, members of the Planning Board interviewed Price to see if he would be a good fit for the work needed. The applicant’s representative, Joseph Shanahan, was not present.

Price said he’s been working on hydrogeologic issues — primarily in Southeastern Massachusetts and the Cape — for nearly 30 years. He said Horsley Witten had reviewed solar projects and analyzed their water quality impacts, but he noted that the firm doesn’t do much development work. 

Board Chair Richard Swenson reviewed three major reasons why a study on stormwater runoff was needed.

“Abutters to this property have reported to this Planning Board that they are running their sump pumps 12 months a year. In the spring, some people are running multiple sump pumps,” Swenson said. “It’s obviously very wet.” 

In addition, he said the board has been told the site is a “glacial till” area, meaning the sediment was deposited by a glacier and is not particularly absorbent. 

“It’s also been reported to this board that this site has previously been perced for residential development and failed those tests,” Swenson said. 

A perc test is often used to determine where a septic system can be built, and is simply a test of how well the ground being assessed drains or percolates water. 

Swenson explained that the board had not confirmed or denied those points, but wanted to bring them to Price’s attention to explain the questions the board hopes to have answered. 

Price said one common concern with all solar projects is “water quantity,” which seemed to be the main concern for the Fearing Hill proposal. He also noted that the site is currently forested, which adds another layer of complexity. 

“So this is the most dramatic change you can get from the water budget standpoint,” Price said, explaining that mature forests slow down the rain as it falls, take up rainwater and otherwise minimize runoff. “Clear cut that forest? That goes away. So a very large component of the water budget now becomes runoff.”

He said if the site was on a hill, people downhill would be “the recipients of that water.” 

To fully understand the potential stormwater runoff impacts, Price said a few different tests would be needed — and Horsley Witten would need to see what construction and mitigation measures are proposed. 

It would require the Fearing Hill applicant’s cooperation, and Price said the cost could range from $50,000 to $100,000. The cost would vary depending on what research the applicant has already done on the site.

Price said he might recommend drilling some borings on the site to see if the materials change — or are more permeable — beyond the surface levels.

“They must have stormwater management of some kind proposed here,” Price said. “So we would need to look at how effective that is. [...] The changes I discussed about the generalities of there being more runoff when you take the trees out can be mitigated with appropriate design of stormwater control measures.” 

Price said he hadn’t seen the Fearing Hill plans, but said it was possible they’d put measures in place to curb runoff issues for neighbors. 

The Planning Board voted unanimously to move forward with Price and the Horsley Witten Group. The engineering firm will do the work, beginning by assembling a detailed, phased plan for conducting the necessary Fearing Hill stormwater runoff analysis. 

The Fearing Hill applicant will cover the cost. The applicant could choose to appeal the board’s hydrogeologist selection, but Swenson said he did not anticipate an appeal.