Stanford University released a 41-page report Friday, May 1, outlining two plans to allow water to get around, or through, Searsville Dam, providing passage for threatened steelhead trout.
The university would either create an opening at the base of the 123-year-old dam to allow the creek to flow through and provide the fish passage to upstream creeks; or it would allow the dam to fill completely with sediment, and Stanford would develop wetlands and a new stream channel through the sediment to allow water and passage upstream, according to the report.
The Searsville Alternatives Study Steering Committee Recommendations is the culmination of four years of work by 12 university administrators and faculty, including specialists in conservation, land use, environmental sustainability and water conservation. It received input from an advisory group that included representatives from the cities of Palo Alto and East Palo Alto, the U.S. Army Corps of Engineers, environmental advocates and neighborhood groups.
While the steering committee identified the two alternatives, it and the advisory committee looked at eight options, including doing nothing and taking the dam down. Some groups and persons on the advisory committee continue to recommend and support removal, including dismantling the structure in stages.
The two alternatives the steering committee identified would allow the dam to stay in place for now. Stanford could study the feasibility of removing the aging structure in the future. A key consideration in either proposed alternative will be what to do with the approximately 2.7 million cubic yards of sediment that have accumulated in 120-plus years of the dam's existence. The environmental impacts of downstream flooding and releasing part or all of the sediment downstream, or even hauling it all away, must be carefully considered, the report noted.
The first alternative, which the university prefers, would remove much of the sediment through sluicing and flushing and stabilization of the coarse accumulated sediment. This alternative assumes that downstream conditions would need to adapt to the increased sediment that will no longer be trapped behind the dam once an opening has been constructed.
The opening would be at grade with the creek. Fish would be able to pass through the opening, connecting Corte Madera Creek below the dam to a riparian channel leading to the upper creek. Leaving the dam in place establishes a "check dam" the would moderate the rush of water downstream from runoff during large storms. Some of the upstream wetlands might be preserved by having cutoff seepage walls.
Resource agencies and the San Francisquito Creek Joint Powers Authority would have to coordinate with Stanford to address the constriction downstream of the creek channel to protect against flooding in large storms, according to the report.
Searsville Lake is currently 90 percent silted in, and the second alternative would keep the dam in place without puncturing it, letting the lake fill in. A new creek channel, cut through the sediment, would move the water to both ends of Corte Madera Creek above and below the dam. The dam might also be lowered or notched to relieve flooding. A fish ladder would also be use by fish getting from one part of the creek to another.
These preferences do not preclude someday removing the dam, said Jean McCown, director of community relations. But the university wants to be careful about the impacts of the release of sediment and of flooding.
The alternatives would also allow the university to continue to use water from the creeks.
"The original purpose of the Dam and Reservoir was for water supply, and Searsville has been and continues to be an important source of water supply for the University," according to steering committee report.
"This recommendation creates a new point of diversion downstream and shifts water storage from Searsville to Felt Reservoir. Water diversions currently made at Searsville would most likely be moved to the existing San Francisquito Creek Pump Station, approximately 4 1/2 miles downstream from Searsville Dam," the report reads.
Diverted water would be stored at an expanded Felt Reservoir in order to meet the existing seasonal water needs of the university.
"The recommendation regarding water diversion and storage is intended to preserve Stanford's rights to creek water diversion and storage considering the effects of climate change, population growth, and drought on the region's water sources," the committee wrote.
The alternatives could cost in excess of $100 million. The university does not expect to carry that entire burden.
"Finding ways to address the financial responsibilities will be one of the top priorities," the steering committee wrote.
But not everyone agrees with the steering committee's choices.
Two key organizations still say removing the dam is the only acceptable action.
"Poking a hole in an unneeded dam or letting it fill in with sediment are not viable solutions. These are ineffective Band-Aids that are unlikely to secure permits or attract funding support," said Matt Stoeker, a biologist for Beyond Searsville Dam and a member of the advisory committee. "The troubling thing is that recent studies have shown that dam removal, combined with identified off-stream floodwater detention ponds, can provide the greatest ecosystem benefit while also achieving elevated flood protection that is in line with their preferred orifice alternative."
In his advisory group recommendations, Stoeker wrote that removing the dam and all accumulated sediment and creating a creek valley habitat or removing the dam and some accumulated sediment, stabilizing the remaining sediment and creating a middle lake for Stanford's water use are the only possibilities.
The other alternatives would create lethal water conditions in the reservoir for organisms, including the steelhead trout, and would cause the spread of exotic species downstream, among other problems.
The new bypass channel in the second alternative would require massive earth moving and habitat disruption at Jasper Ridge, and oversight and maintenance would not be feasible.
"We see no possible way to operate such a massive and long channel with existing water constraints and no feasible way to prevent downstream reservoir entrapment and death of steelhead. (And) there are major additional fish passage problems exacerbated by reservoir level fluctuations associated with operating a notched dam for flood protection," Stoeker wrote.
A recent National Marine Fisheries Service Jeopardy Decision against Santa Barbara County indicated numerous legal problems with orifice dams related to the Endangered Species Act, he noted.
In comments on the study after its release, American Rivers, another group on the advisory committee, and Beyond Searsville Dam said jointly in a statement the university's announcement will only delay a final decision regarding the dam's fate.
"American Rivers appreciates that Stanford has abandoned the idea that Searsville is useful for supplying water for their golf course and landscaping, particularly in this drought," said Steve Rothert, California director of American Rivers. "However, we are concerned that operating a dam with a hole in it will be more troublesome than they expect, with impacts to fish passage and sediment accumulation causing ongoing problems."
Stanford is currently being sued by Our Children's Earth and The Ecological Rights Foundation over Searsville.
The groups are also suing the National Marine Fisheries Service, alleging it inadequately analyzed how the dam, reservoir and booster pumps add to and exacerbate adverse impacts on the threatened species when it approved water diversion in 2008.
Related article: Stanford officials look to solve Searsville dilemma (January 2013)