Searsville committee to evaluate impact

April 10, 2012, 2:45 a.m.

 The newly formed Searsville Alternatives Study Steering Committee is now directing planning efforts for potentially major changes to the Stanford-owned Searsville Dam and Reservoir. Because the dam controls water flow to Stanford’s Jasper Ridge Biological Preserve and has a controversial environmental impact on surrounding areas, the committee formed to conduct thorough studies over the next two years to precede any action, according to Philippe Cohen, administrative director of Jasper Ridge and a committee member.


Cohen gave a presentation Monday night at the Stanford National Accelerator Center outlining the issues the committee faces.


Jasper Ridge presents a particularly challenging situation for the committee. According to Cohen, the reserve tries to maintain a “hands-off” policy as a biological field station, leaving the terrain untouched by humans. This policy allows for important field research projects, including the Jasper Ridge Global Change Experiment, which has been collecting climate change data since 1992.


The preserve also protects several native and endangered species, including the steel-headed trout and California red-legged frog.


The idea of the “hands-off” policy is to remove the human influence factor from natural environments. However, the manmade Searsville Dam has had a major influence on the local environment since its construction in 1892 and the Jasper Ridge area is starting to feel its long-term consequences, Cohen said.


In particular, a 1998 study showed that the dam trapped huge amounts of sediment in Searsville Lake. The study recorded 207,000 tons of sediment flowing into the dam and only 15,000 tons flowing out. Searsville Lake was a public recreation area until Stanford closed it to the public in 1975.


Over the last decade, the once-popular lake has diminished in size and become overgrown as it fills with sediment.


Stanford’s Searsville Alternatives Study Steering Committee formed in order to find the best way to address this growing problem, while mitigating effects on Jasper Ridge and surrounding areas. Cohen said that as a result of the dam’s impact over the last century, preserving the area requires action.


“The status quo is the only option not on the table,” Cohen said. “If you want to keep it the way it is, you have to do something.”


Cohen said that the committee has hundreds of options to explore for action. The major options he outlined included targeting the dam by either raising, lowering or removing it; targeting the reservoir by either removing sediment or allowing the lake to fill in; and exploring outside options such as adding a bypass channel or diverting water.


Part of the recovery process for the lake, according to Cohen, is coming to terms with human impact on the environment in light of the “hands-off” policy.


“The human fingerprint is everywhere,” Cohen said.


The challenge now, he said, is to counteract the Dam’s impact with as little unintended effect as possible on the surrounding San Francisquito Creek and Corte Madera Creek watersheds.


This goal proves particularly difficult because the ecological factors of the area interact in unpredictable ways. For example, rising carbon dioxide levels, which would intuitively seem positive for plant growth, in reality, can inhibit plant growth through various effects on soil conditions and temperature.


Because of the complexity of the ecosystem, the committee is commissioning two years of studies to determine the right course to recommend to Provost John Etchemendy Ph.D. ‘82.


Cohen said that funding conversations will take place after the studies, but Stanford will fund any changes to the area.

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