Atherton: Dogged by drainage woes, town to spend $130,000 to find fixes Atherton: Dogged by drainage woes, town to spend $130,000 to find fixes (December 28, 2005)

By Andrea Gemmet

Almanac Staff Writer

With residents complaining about flooding, water damage and rushing runoff, the Atherton City Council is preparing to spend almost $130,000 on a comprehensive study of drainage problems in town.

At the December 14 meeting, City Council members said they were increasingly concerned that the town's one-size-fits-all drainage policy for new construction isn't working, particularly on sloping properties west of Alameda de las Pulgas.

Currently, town policy requires most new development to keep its runoff on site, usually by constructing French drains, dry wells or infiltration pits, to prevent huge amounts of water from overwhelming storm drains and flooding the Atherton Channel.

"Water that falls on the property stays on the property," as Councilman Alan Carlson puts it.

The problem, town officials have discovered, is that what works in a relatively flat neighborhood like Lindenwood doesn't necessarily work on a rocky hillside property, where runoff overflows the dry wells instead of percolating into the soil.

So, in the wake of complaints from residents saying that new construction by uphill neighbors is causing flooding and damage, Atherton council members indicated in October that it might be time for some changes to the town's development rules.

"Right now, we have a simple, easily understandable policy, but there are some negative effects," said Mike Hood, Atherton's building official. "If we're going to depart from it, I suggest we have some rational explanation for that departure."

Working with Ed Boscacci of BFK Engineering, Mr. Hood mapped out a 10-part study estimated to cost about $127,000. Among the tasks are measuring groundwater levels, making an inventory of dry wells and infiltration pits and evaluating their effectiveness, and determining percolation rates for typical soils found throughout the town.

Council members added several more areas of study, including measuring the impact of the increasing amount of paved or impervious surfaces in town, a map showing areas of rising groundwater to compare with a 1997 USGS survey, and suggestions for optimal solutions.

"There's an additional problem," said Kacy McClure, who lives on Stevick Avenue west of Alameda. "These huge houses have huge basements that are taking away the soil we assume will be absorbing this water."

Council members agreed to have the effects of huge basements included in the study, and also asked for data on how much groundwater is being pumped into roadside storm drains to accommodate basement construction.

The council directed town staff to make the additions and return to next month's meeting with a "request for proposals" document that can be approved and then distributed to companies that will make bids to do the work.

"This study (will) give us empirical data and should give us some quantifiable information that will be something to hang our hat on," said Mr. Hood.

On a separate, related agenda item, the City Council requested a proposal for short-term changes to drainage regulations in problematic parts of Atherton.

E-mail a friend a link to this story.