SAN MATEO COUNTY - A vital reservoir near San Mateo that stores billions of gallons from the Hetch Hetchy water system will soon boost its capacity by as much as 10 percent.
The restoration of the Lower Crystal Springs Reservoir comes 26 years after the state ordered the water level lowered 8 feet until safety concerns were addressed. Engineers at the San Francisco Public Utilities Commission, which owns the dam, started considering how to address those concerns and return it to previous capacity.
Enter the frogs.
With water no longer flowing regularly over the spillway, the 119-year-old dam's knobby top provided a perfect place for water to collect and for the red-legged frog, a threatened species protected by the state, to take up residence. A nearby spring flows onto the south end of the dam, perpetually feeding the pools of water, and the raised road on top shades the puddles, slowing their evaporation.
The frogs thrived, leaving the state, county and water agency stymied.
"We find red-legged frogs all over the county. This time we just happened to find them on top of the dam," said Public Works Director Jim Porter, who added that his department worked for 15 years to find a solution to the problem.
It appears water will start flowing over the dam again within a few years, according to Public Utilities Commission project manager Tasso Mavroudis.
The county, which must replace the raised portion of Skyline Boulevard because it is seismically unstable, will be moving the frogs from the top of the dam to a new wetland area on land owned by the commission.
The road and the columns supporting it will be removed, perhaps as soon as October 2010, Mavroudis said.
Once the demolition is complete, the San Francisco water agency will begin its work to improve the spillway and the basin below it that water flows into. The spillway is a lowered portion of the dam that catches excess water. When that's finished - perhaps by early 2012 - San Mateo County will complete work on the road.
The water agency considers the project important - and will invest an estimated $32 million into it - because the additional 8 feet mean some 3 billion more gallons of Sierra Nevada water that could be stored in the reservoir. That increase comes on top of the 22.1 billion gallons the reservoir currently holds.
Storage is becoming an increasingly important matter as the state becomes more concerned about droughts, Mavroudis said.
One of the project's goals will be to improve drainage on top of the dam, so the monolithic concrete structure never becomes an ecosystem for threatened frogs again, he said.
"A lot of the maintenance has been deferred for years because of the frogs," he said. "It's been a problem since Day One."