The 21-foot deep-water detention basin, originally planned for Annex, is no longer needed, Santa Clara Valley Water District spokespersons said Wednesday.
"We've done some new hydrology studies and discovered that some of the flow that we thought went into Permanente Creek actually flows in quarry pits," said Marty Grimes, a water district spokesman about the approximate 230 acres at the cement plant in Cupertino, where a pit was found several hundred feet deep. "That means we don't have to go the same depth."
Instead, according to Grimes, the water district project managers will present two alternative project proposals to the water district board of directors, and in October, to the Mountain View . One proposal calls for a smaller 11-foot basin at the site "that would provide the same flood protection," said Grimes. The other plan builds a pipe that catches the storm water and diverts from Permanente Creek. That pipe would be built beneath Cuestra Drive.
However, with the latter proposal, there may be some "parcels upstream of Cuesta Park that would not be protected; that includes ," he said. To mitigate flooding upstream, the water district plans to either deepen or widen Hale Creek, which runs through Los Altos and Los Altos Hills.
The Permanente Creek Flood Protection Project sprung from a bond measure in 2000 that created funds for the water district to help protect 1,664 homes from the probability of a 100-year flood. The project included the original proposal for the 21-foot basin at the Cuesta Park Annex location, one at , one at Rancho San Antonio and another at Blach Intermediate School in Los Altos.
After the down the water district's project at Blach, however, they had to find alternatives. One of those may have been to build a dam, according to Afshin Rouhani, project manager.
"When all the other options failed, the possibility of a dam came up," Rouhani said. "But there are significant environmental impacts."
However, with the discovery that water had been diverted to the pits at the Lehigh Cement quarry, "a dam is no longer necessary," Rouhani said.
The water district estimated that the original 21-foot basin at Cuesta Park Annex would cost $40 million. That would remain the price tag for the 11-foot basin, because the structural modifications to Hale Creek would still need to be made. The alternate scenario, the laying of the water catchment pipe beneath Cuestra Drive, sheds $6 million from the cost. These plans still include the changes at Hale Creek.
Flood basins at the other sites will continue to move forward.