Water superintendent outlines drought limits, new hydraulic model and PFAS response

Superintendent Mark Willett of the Nantucket Water Department updated the Planning Board on Tuesday on the town's withdrawal permit, drought restrictions and steps to respond to PFAS contamination.

Willett said the department is finalizing “a really pretty high-tech, very, very accurate hydraulic model of our system” that will let staff test how larger subdivisions or major commercial users would affect the town’s withdrawal permit. “When we get a larger subdivision — I’m not talking, you know, smaller cul de sac style…if it’s like Old South Road development or like a Tacoma Green development — I will be able to run that model and we can take a look at what that’s gonna mean to our permit, especially under these drought conditions,” Willett said.

Why it matters: Willett emphasized the distinction between groundwater level drought triggers set by the Commonwealth and the amount the town is legally allowed to pump under its permit. He told the board the Russell’s Way well is about 7–7.5 inches below the state’s drought threshold and that, because roughly half of precipitation reaches the water table, “I need 14 inches of rain to get out of drought.” Even if water is above pumps, he said, MassDEP restricts pumping under drought conditions and can enforce the permit.

Board members and residents asked how the model could help planning. Willett recommended joint meetings between the Planning Board and the Water Commission to identify likely build‑out scenarios and run them through the model so the department can use those forecasts when negotiating future permit increases with MassDEP. He said advance notice of development from planning staff has already helped the water department estimate capital needs and will improve permit negotiation.

PFAS, mobile treatment and new wells: Willett said the department is building a PFAS treatment system; the same control package could be configured on a mobile trailer to treat contaminated wells at temporary locations. “That same system can be built on a tractor trailer flatbed … it could be moved and connected to any well that was placed anywhere on the island,” Willett said. He also said the department is seeking an additional deep well site (tentatively called Well 17) on the north pasture, separate from the island’s current cluster of wells, to provide redundancy if a well becomes contaminated.

Enforcement and customer compliance: Willett said the department is exploring how to enforce outdoor watering restrictions and other permit conditions more effectively after repeated noncompliance. He and board members discussed fines, possible public notice of repeat violators and whether higher fines or court actions would be effective. Willett said he is working with MassDEP on enforcement limits and options.

Board direction and next steps: Planning Board members encouraged continued coordination and suggested staff share the Planning Department’s build‑out analysis with Willett so the model could test combined scenarios. Willett said he will make the model results available to planning staff and the water commission and recommended periodic joint meetings.

Ending: Willett told the board he will return periodically to update members as the model is completed, the mobile treatment option is implemented and permitting negotiations with MassDEP proceed.