The town gets tunnel inquiries periodically and there is one Woodside home in which a tunnel connects the main basement to an underground garage and another basement under an accessory structure, he said.
"There are likely some other properties that have underground connections between structures, I am just not personally aware of them," Mr. Schaan said in an email.
Town staff members are in the early stages of examining basement regulations and were seeking direction from the council on an ordinance that would eventually come before the public for a hearing before adoption.
The council suggested that tunnels should not be wide enough to accommodate a motor vehicle or a wall of wine racks, and that maybe tunnels should be excluded from footprint limits. Underground spaces beneath accessory structures should be acceptable but not habitable nor should they have access to daylight, council members said.
Mr. Schaan led the group through a discussion that also touched on the dimensions of basement footprints, their extension into setbacks, the handling of graded earth, light wells and whether they should count as square footage, and groundwater and tree-root impacts.
A sampling of opinion: A basement should not exceed the footprint of the structure above, possibly excepting light wells; limited extension into setbacks may be OK on small or nonconforming lots; perhaps it's appropriate to increase the maximum volume of graded earth before requiring a permit; extensive tunneling can inhibit groundwater flow by creating an underground dam effect.
"It's very difficult, it's nearly impossible" to predict the impacts of underground development on groundwater, Mr. Schaan said.
How a basement evolves is a battle of wits, to some extent. Homeowners and their representatives will study town regulations for interpretations that favor their plans and then argue accordingly at the Town Hall planning counter. Forethought is a must in writing regulations, council members advised.
"It's like whack-a-mole," Councilwoman Anne Kasten said.
"You've got to be really careful about it. You've got to think about it," Councilman Peter Mason added.
"We should not criticize our (residents) for following the rules," Councilman Dave Burow noted.
Go to tinyurl.com/WS-basement and click on the agenda for April 12 for Mr. Schaan's staff report on basement regulations, beginning on Page 46.
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