By Jon Wiener
Friday, March 10, 2006
By any measure, the restoration of Charleston Slough has been highly successful. Maybe even too successful.
A quarter century has passed since the city of Mountain View paid $1 to acquire more than 110 acres of salt ponds from the Leslie Salt Co. At the time, the city was building a new sailing lake at Shoreline Park, but had no way of filling it. The purchase obligated the city to restore the ponds to wetlands, and the two projects began to develop hand-in-hand.
In 1989, the city modified the levees the company had built in order to open up the slough to tidal action. Bay waters began flowing in, but the city kept a channel open to pump water into the lake.
For the former ponds, the plan worked like a charm. The tides brought in enough sediment to convert the ponds into mudflats, providing prime feeding grounds for several species of migratory shorebirds. Soon, city officials predict, wetlands vegetation like pickleweed and cordgrass will move in, followed by any number of threatened and endangered species native to the Bay, and the area will once again serve as a thriving marshland.
But while the sediment has been crucial to improving the ecology of the slough, it is has also become a threat to the lake's water supply, slowing the channel and permanently clogging the pipeline. Choking off water flow at either point would mean a slow death for the lake.
"We've been so successful with the mud coming in that it's almost been overwhelming," said John Welbourne, an engineer for the city.
Welbourne's boss, public works director Cathy Lazarus, agrees, and says the city could not delay in remedying the problem.
"It would have been a fairly short time frame for the channel to disintegrate completely," she said.
In her office, Lazarus keeps a chewed-up propeller from the underwater pipeline. The city has abandoned that pipeline -- which is now too clogged with sediment and barnacles -- and is hard at work on a new one. But the propeller serves as a reminder of the urgency the city is facing.
Reverse the flow
City officials believe they've found a way to save the lake through an innovative solution that is already under construction. The idea, first proposed by a city consultant three years ago, is that the lake can backwash enough water into the slough -- for one hour each day -- to keep the channel free of mud.
"We weren't really keen on it," Welbourne said. "It took some convincing at first."
Now Welbourne is convinced. He is overseeing the nearly $3 million construction effort to shore up the banks of the lake and replace the abandoned pipeline with one that is 36 inches in diameter and easier to access.
When the work is finished this summer, the new pipeline will pump as many as 150,000 gallons of water per day into the lake. The water circulates around the lake before emptying out into Permanente Creek and draining back into the Bay. But for one hour each day, the water will flow backwards through the new pipeline, heading out towards the slough, using only the force of gravity to scour off the mud at the bottom of the channel and push it to the sides.
The lake is already down a few inches, and construction vehicles work constantly to complete the project. Christina Ferrari, who contracts with the city to operate the boathouse at the lake, said that on a sunny day two weeks a couple brought out chairs and sat on the exposed rocky beach to watch the activity.
Last year, according to Ferrari, tens of thousands of people rented sailboats and windsurfing equipment to use on the lake that city recreation manager Paula Bettencourt calls "one of the jewels of Shoreline Park." She said the lake also played host to corporate team-building, company picnics, summer camps and windsurfing and sailing classes for more than 1,000 children.
"It's a wonderful place to learn, because it's on an enclosed body of water, and the winds are consistent," Ferrari said.
Restoration efforts gather steam
Mountain View Mayor Nick Galiotto joined other local leaders last week to kick off the Clean Bay Campaign, an effort to educate residents about the impacts that pharmaceuticals, motor oil and other hazardous materials can have on the struggling ecology of the Bay.
Experts say about 90 percent of the Bay's wetlands -- which provide habitat, flood control and water purification -- have been lost to industrial use. Across the South Bay, massive restoration efforts are now underway to recover the valuable ecosystems.
The restoration of Charleston Slough follows the restoration of the neighboring Mountain View tidal marsh and the Stevens Creek tidal marsh. Both of those projects were required under the original permit that allowed city to build the lake at Shoreline.
Last year, the Navy relented in the face of public pressure and agreed to clean up a polluted Moffett Field drainage pond so that NASA and the Midpeninsula Regional Open Space District could restore much of it.
Save the Bay has spearheaded the restoration of 1,600 acres in Palo Alto's Baylands to the northwest of Charleston Slough. Meanwhile, the state is preparing to restore more than 15,000 acres of former Cargill salt ponds across the South Bay, the largest such project in the country.
-- Jon Wiener
http://www.mv-voice.com/story.php?story_id=1157