Friday, February 01, 2002 - 4:08:26 AM MST
Stormwater interceptor to help raise Lake Merced water levels
S.F., Daly City to share construction and operating costs
By Christine Louie
DALY CITY -- Funding has been secured for a stormwater interceptor that will someday divert rain into San Francisco's Lake Merced, which for years has suffered from dropping water levels.
San Francisco and Daly City will split the cost of the $706,400 project, and both cities will be responsible for the interceptor's operation once it is built.
The interceptor will be built at the mouth of the Vista Grande Tunnel, a three-quarter mile conduit that has been used for decades by the North San Mateo County Sanitation District to dispose of stormwater and wastewater. Engineering and consulting firm CH2M Hill, which has offices throughout the world, is completing the designs of the interceptor.
Once built, the interceptor will begin collecting stormwater, which will be evaluated for its water quality, said Patrick Sweetland, Daly City's director of water and wastewater resources. Based on those results, both cities would devise a plan to determine what percentage of the stormwater would be added into the lake.
City engineer Mo Sharma said testing the water is necessary to ensure it is consistent with the water quality of Lake Merced. Most of the water would be diverted during the peak rainfall period, roughly 450 cubic feet of water per second.
"If the water quality tests come out favorably, then we could have quite a bit of water (diverted)," he said. The hope is to have the unit, which looks similar to a manhole, built by the end of this month. A pre-construction meeting has been scheduled for Monday.
Proponents say that if the pilot project is successful, water levels for Lake Merced may rise. The lake has experienced a plummeting water table for years now, a problem which many believe has been worsened by uncontrolled well water pumping from Daly City and nearby golf courses and cemeteries.
Sharma said that a preliminary estimate is for the lake's water levels to go up about two to three inches a year.
Adding stormwater back into the lake, along with plans to build a $7 million recycled water facility in Daly City are two options officials are considering as they try and save the lake, and prevent the intrusion of salt water into the water supply.
Water officials in Daly City and golf course representatives missed a December deadline to formulate a contract for delivering recycled water to the golf courses.
Sweetland said Thursday that he expects the contract to be signed by the end of February. The delays, he said primarily revolved around funding for the facility and for the determining how much each golf course would pay for recycled water delivery.
Dick Morten, a member of the Lake Merced Task Force Water Committee praised the stormwater project but noted that "it's not the be-all, end-all cure" to the lake's lowering water levels, believed to be supplied by a depleting aquifer underneath the lake.
He stressed that before the lake can be restored, the aquifer which feeds it must first be replenished.
You can reach STAFF WRITER Christine Louie at 348-4337 or e-mail at [email protected].