A majority of Woodside council members now favors an ordinance that would allow the floor area of a new basement to extend no more than 50 percent beyond the footprint of the main residence above it.
Previously, four of the seven council members favored 65 percent, but in a straw poll of the council at its April 12 meeting, two members changed their minds: Anne Kasten said her previous view had been a result of feeling unwell that evening. Tom Livermore noted the Planning Commission's preference for 50 percent.
When the proposal regulating basement size and location returns to the council for consideration, it will contain the 50 percent limit. Councilmen Dave Tanner and Peter Mason, both on a council subcommittee that recommended a 50 percent allowance, also favor that limit.
The council on April 12 heard from resident and architect Steve Lubin, who presented arguments for reducing the allowed volume of a basement excavation by about one third.
Click here to see the illustrations Mr. Lubin used in his presentation.
The proposed regulations employ a formula that balances basement floor area against depth. At maximum size, a basement's volume (in cubic yards) would equal the allowed floor area for the main house multiplied by 12 and divided by 27.
The multiplier is a variable that alludes to depth but is somewhat arbitrary, Mr. Lubin told the Almanac. Most basements are 8-feet deep, he said; a multiplier of 12 yields a larger basement.
After Mr. Lubin's presentation, which showed icons of hundreds of trucks to demonstrate how deeper basements dramatically increase a project's total excavation and truck trips, the council decided that excavations deeper than 8 feet would require the applicant to consult with the town engineer.
On deeper cuts, state regulations kick in to prevent earthen walls around the future basement from falling in and endangering workers. Ways to stabilize this situation include injecting the soil with fluids to solidify it, sloping the walls away while the basement is under construction -- called over-cutting -- or erecting shoring walls. Over-cutting results in more significantly more off-haul. The council expressed a preference for shoring.
Lots of trucks
Using a multiplier of 12, a maximized basement under a 6,000-square-foot house would require 752 (arrivals and departures) by large-capacity trucks to off-haul soil and add drainage rock, and 102 trips by concrete trucks, according to Mr. Lubin's illustrations.
A multiplier of 8 yields 379 trips for off-haul and drainage rock, or 50 percent fewer trips, Mr. Lubin said. As for concrete, the smaller multiplier reduces truck trips by 41 percent.
"My hope was that (the council) would realize they've been really remiss in understanding the impacts of what their decisions would be," Mr. Lubin said in an interview.
As for the debate over a 65-percent versus 50-percent allowance outside the house footprint, "it's almost irrelevant as opposed to modulating the total volume involved," Mr. Lubin said.
Mr. Lubin also criticized resorting to shoring when a basement goes deeper than 8 feet in that it will probably involve pouring much more concrete, a strong greenhouse gas emitter, and employing a pile-driver from 8 a.m. to 5 p.m. Monday through Friday and Saturday mornings. "That would be atrocious," he said.
Asked about a multiplier of 12, Councilman Tanner said it allows a squash court to be built in the basement. A multiplier of 8 "is a dramatic volume reduction and you can't get a whole basement," he said. "It's hard to pick a number. ... As we go through this, we're really giving this thing a lot of thought."