Sand Trap : Lake for Waterfowl Sits Empty as Design Error Creates Mosquito Threat

The Sepulveda Basin wildlife lake has not been filled with water because the U.S. Army Corps of Engineers allowed the lake to be dug too deep to drain properly, causing potential mosquito problems in the San Fernando Valley’s largest remaining open space, Los Angeles city officials said Monday.

The city was to fill the 11-acre lake near Woodley Avenue and Burbank Boulevard with half a foot of fresh water this month, in time for migratory waterfowl to use it as a resting place for the winter, said Gary Schussolin, a city parks engineer.

But unless the lake bottom is raised about two feet to allow water to drain and prevent it from becoming stagnant, the lake will become a prime breeding ground for mosquitoes, city officials said. Some mosquitoes in the basin are known to carry the potentially fatal St. Louis encephalitis virus.

A spokeswoman for the Corps, which owns the 11-acre lake and plans to lease it to the city, said the agency may not be able to have the lake bottom regraded until spring, after the birds have flown north.

The engineering mistake has angered environmentalists, who say the lake is the key component of a wildlife area in the Sepulveda Basin that includes footpaths and bird-viewing blinds.

“I’m not happy about this,” said Sandy Wohlgemuth, conservation chairman for the Los Angeles Audubon Society. “They told us it was going to be filled last January. I’d like to see it filled tomorrow. The ducks are already here looking for a place to rest.”

The lake is designed to eventually contain about 12 million gallons of reclaimed sewer water from the Donald C. Tillman sewage treatment plant, about half of which will be flushed daily through the lake into the Los Angeles River to prevent mosquitoes from establishing a breeding ground. The lake will be drained during the summer for the same reason.

Before the city receives approval from the state Water Quality Control Board to completely fill it with about five feet of treated sewer water, the lake was to be filled with about half a foot of fresh water. That would be enough to provide a resting place for waterfowl, Wohlgemuth said.

But because of the grading problem and the mosquito threat, the city cannot do that.

Sheila Murphy, a Corps spokeswoman, said the lake was graded in the late spring, when the ground was still damp from winter rains. She said that when the lake bottom dried, it subsided to a lower depth than called for in the plans.

The W. E. McKnight Construction Co. of Baldwin Park had a $2.6-million contract to grade both the wildlife lake and a 26-acre recreational lake planned for the southeast corner of the basin, Murphy said. She said the Corps does not blame the McKnight firm.

“The contractor did a good job . . . there were just a series of small things that went wrong, and basically we’re trying to work it out now,” Murphy said. “I would like to think we can get a handle on this soon, but we may want to wait until after the rainy season to regrade.”

Work Approved

Arthur Leon, chief engineer for McKnight, said the company pumped all the water out of the soil before excavating the lake bottom. The firm’s work, he said, met the Corps’ specifications and was certified as satisfactory by the agency when the job was completed. He said the problem “could have been a design error on the part of the Corps.” He said the company would welcome the opportunity to do additional work in the basin--for a fee.

“Asking us to go back and do this for free would be like hiring someone to put in a swimming pool and then asking him to move it to the other side of the yard,” Leon said.

Regrading the lake will cost about $30,000 and take about two weeks, said Gary Schussolin, a city parks engineer. He said the city sent the second of two letters Monday to the Corps, asking the agency to regrade the lake as soon as possible. The city does not have the resources to do the job, he said.

“If they regrade the bottom, all we have to do is turn on a valve and that area turns into a habitat for birds,” Schussolin said.

Schussolin said the drainage problem was detected this summer by crews from the Southeast Mosquito Abatement district, who noticed a bog to the west of the island in the center of the wildlife lake.

Frank Pelsue, general manager of the district, said crews had to spray the swampy area with insecticide twice a month this summer. Pelsue said he is concerned that the lake would become a breeding ground for mosquitoes carrying St. Louis encephalitis, a virus carried by birds and transmitted by mosquitoes to humans and other mammals. In 1984, there were 26 cases of the disease in Southern California, including one that ended in death.