Carlsbad may rent pumps to control lake's water levels

By: BARBARA HENRY - Staff Writer | Monday, December 5, 2005 8:50 PM PST ∞

CARLSBAD ---- In hopes of preventing a repeat of last year's spillovers, the City Council will decide tonight whether to spend $50,000 to rent large-capacity pumps to temporarily control water levels this winter at Lake Calavera.

Downstream residents say they're in favor of anything that would help with their flooding concerns, but environmentalists say they want more information about the proposal.

Capable of pumping up to 4,500 gallons a minute, the pumps would be dropped into the lake in northeastern Carlsbad on an as-needed basis for three or four months, city associate city engineer Chris Muehlbacher said Monday. They could be used to lower the lake's water level in advance of stormy conditions, thus preventing spillover at the dam.

"It would be only temporary to get through the rainy season," Muehlbacher said.

Next winter, the city isn't expecting to need rental pumps because it is planning a big construction project fix the valve mechanisms that regulate the lake's water levels. The valves, which control how much water flows downstream at any given time, haven't worked in years. One upper valve is stuck in the open position, while the two lower valves are locked in the closed position.

Most winters this hasn't mattered much, but last year's intense rainy season caused the lake to fill up with so much water that it started spilling over the dam. The rushing water then eroded the stream banks and worried the people who live downstream in Rancho Carlsbad, a gated, senior mobile-home park.

Bill Arnold, president of Rancho Carlsbad's homeowners association, said people in his community pushed the city to obtain the rental pumps.

"It was a suggestion we've made and the city is picking up on it," he said.

The temporary pumping plan is raising concerns among environmentalists. Diane Nygaard, who heads the regional Preserve Calavera group, said she thinks a new city staff report on the pump rental proposal doesn't contain enough documentation on how the project will be carried out. Nygaard said she wants to know what lake water levels will trigger pump activity, how the pumps will be powered and how environmental issues will be handled.

"We really have questions about whether this is a categorically exempt project," she added.

Categorically exempt projects --- ones that must be done to resolve an emergency situation --- don't require extensive environmental permits. City officials have said the pumps would fall in this category.

Muehlbacher said city staff members haven't yet established what the water-level trigger point would cause the pumps to operate.

"What becomes of concern is extended rainy events," he said. "One rainfall is not going to trigger pumping. It's numerous factors, including the saturation of the ground."

The city may not need them at all, he said. There hasn't been much rain so far this year, and the lake's surface area now covers 21 acres. In order to have a spillover, the surface area would be 30 to 32 acres, he said. During the height of the spillovers last winter, the lake covered up to a 36-acre surface area, Muehlbacher said.

This isn't the first time the city has come in conflict with environmentalists because of its plans for the lake.

Initially, the city had planned to drain much of the water out of the lake in order to repair the valves. Environmentalists and the people who live in the hillside homes above the lake fought the plans, saying they worried that draining the lake would kill fish and plants, leave a bad odor in the air and cause long-term effects on the area's habitat.

After the public outcry last spring, the city revised its plans. City officials now plan to build a small watertight structure that can be lowered into the valve work area. That proposal is expected to go to the city's Planning Commission for its review early next year, and environmentalists have expressed cautious support for it.

Tonight's meeting on renting the pumps is set to start at 6 p.m. at City Hall, 1200 Carlsbad Village Drive.

Contact staff writer Barbara Henry at (760) 901-4072 or bhenry@nctimes.com.

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