Tonight: Woodside may OK limits on basement size, location

Deeper basements

The Woodside Town Council may approve an ordinance tonight (Tuesday, April 26) that would cut back on a proposal to allow 65 percent of a basement to be outside the footprint of the main house. The new draft would also loosen requirements to keep excavated soil on site and add a staff review requirement for basements deeper than 8 feet.

The council meets at 7:30 p.m. in Independence Hall at 2955 Woodside Road in Woodside. If the council approves and introduces the ordinance, the council must then adopt it at a subsequent meeting before it becomes law. The ordinance would go into effect 30 days after final approval.

Tonight's deliberations represent the sixth attempt to introduce this ordinance. The previous council discussion, on April 12, resulted in changes substantial enough to require redrafting and reintroduction. The changes in the redrafted ordinance include:

■ A provision to reduce excavation. To minimize the amount of excavation done for a basement deeper than 8 feet, the town engineer and planning director will have to review and approve methods to prevent the earthen walls from collapsing and endangering workers.

Ways to stabilize the walls, as required by state law, 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 significantly more off-haul and truck traffic, according to a presentation to the council by architect and resident Steve Lubin on April 12. The council discussed the matter after Mr. Lubin's presentation and expressed a preference for shoring.

■ A revision on how much of a basement can exist outside the footprint of the main house above. The ordinance would allow no more than 50 percent of a basement to exist outside this footprint. The council has taken two straw polls on this question, one in February and the other on April 12.

In the first poll, contrary to the opinions of a council subcommittee and the Planning Commission favoring an allowance of 50 percent, a council majority went with 65 percent. The majority shifted in the second poll to a 50 percent allowance.

■ A provision to loosen requirements to redistribute excavated soil on the site. The council has favored the practice of keeping excavated soil on site in the interest of reducing off-haul truck traffic. At the April 12 meeting however, Councilman Dave Tanner, a builder and general contractor, said that soil beneath the top two or three feet tends to be unsuitable for such redistribution.

Previous discussions and subsequent edits to the ordinance include requiring two and a half feet of soil above any part of a basement that is outside the footprint of the main house, and setting aside the need for a site development permit for basements that are 25 percent or less than the allowed maximum floor area.

How deep

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."

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