Council members sounded like they were leaning in that direction during Tuesday's Town Hall work session discussion of proposed rules and regulations.
Geothermal systems, which are considered a sustainable “green” technology, use the groundwater of the Island as “a sink and a source of heat,” explained Drew Bennett, an East Hampton hydrologist consulting with the town on the proposed legislation. Geothermal “is a good thing,” he said, “but is it a good thing for Shelter Island?”
To buy time to answer that question, the Town Board imposed a moratorium on geothermal wells in August 2008 after learning that 50 or more systems were installed on the Island with no regulation by state and county agencies. They hired Mr. Bennett, who worked with Councilman Peter Reich and other town officials to develop a new chapter of town code restricting the systems by establishing maximum pumping rates, minimum setbacks to drinking water wells and maximum depths of the geothermal wells.
But locals told the Town Board loud and clear at a public hearing in December that the risks of the systems to the Island's fragile, sole source aquifer outweighed any green energy benefits, and that the complicated rules would be difficult to enforce.
On Tuesday, Mr. Bennett assessed the risk for each type of geothermal system. Open loop systems draw water from the ground for heat exchange and discharge the groundwater back into the aquifer; they can draw down nearby wells, pull saltwater into wells or raise the water temperature in parts of the aquifer. Closed loop systems draw no drinking water but use an array of vertical tubing, as deep as 300 feet, for heat exchange with surrounding groundwater and sediments. Closed loop wells could penetrate the clay layer that divides the Island's drinking water aquifer from undrinkable saltwater below. Horizontal closed loop systems use the same technology but lay the tubing in trenches, comparable to those for an irrigation system; they neither draw groundwater nor penetrate the aquifer.
The hydrologist listed the systems from most to least risky: open loop systems in the near shore areas pose the greatest risk, followed by inland open loop systems, deep penetrating closed loop systems and shallow closed loop systems. Horizontal closed loop systems presented the least risk to the aquifer but could only be used on a handful of large properties, Mr. Bennett said.
He answered questions about the toxicity and the amount of thermal exchange fluid used in closed loop systems. The proposed town law calls for FDA-approved fluids; closed loop systems use 25 to 150 gallons of the fluid.
According to Water Advisory Committee Chairman John Hallman, industry experts say that the optimum depth of geothermal wells is 200 to 300 feet and that “anything less is not worth it.” He told the board, “You have a hell of a decision to make. My personal opinion: don't even think about open loop.” Some closed loop systems that don't reach the clay layer and are heavily monitored could work, he said.
“It's nice to be green but I'm thinking of the aquifer in the long term.”
Don Kornrumpf and Jeremy Samuelson, from the Group for the East End, asked questions, particularly about the benefits of the systems to the community as a whole.
“It's not a bad idea to ban open loop throughout the Island,” Mr. Bennett agreed. The best approach would be to allow shallow vertical closed loop wells that “can be managed so that the benefit outweighs the risk.”
Councilman Peter Reich suggested limiting closed loop systems to summer operations only so that bottled water, instead of a thermally conductive fluid, could be used and would pose no risk of contaminating the aquifer. Geothermal's efficiency is higher for air conditioning than it is for heat. Mr. Reich noted that houses with geothermal heat may use less fuel oil in the winter but that the continual pumping necessary for heat exchange increases electric use. For cooling in summer, the net electric use is lower compared to houses using standard air conditioning, he added.
Councilman Glenn Waddington focused on the practicalities of geothermal regulation. He said that any monitoring of geothermal systems on private property would be “problematic ... We can't even get a grip on illegal sprinkler systems.” Councilman Ed Brown noted that any testing program would be expensive.
Councilwoman Chris Lewis commented that the primary benefit of geothermal systems goes to the individual. “The aquifer is a community benefit ... The single most important thing we have is water.”
“I think we need to consider total banning of geothermal installations,” she concluded, adding that the town would have to address existing systems as well.
To close, Mr. Bennett said, “The town is really embarking on a challenging assignment ... You should be commended for taking it on.”
Supervisor Jim Dougherty thanked Mr. Bennett, describing him as a “tremendous resource.” He said he would “digest” the information and pick up the issue again at future work sessions.