PWD water supply

The Littlerock Dam and its associated reservoir are part of the water supply system for Palmdale Water District, all of which made it through the recent earthquakes without damage. Protecting the water supply is part of the District’s emergency and security plans.

PALMDALE — Securing the water supply, whether from natural disasters such as earthquakes or more man-made dangers, is an important job for the Palmdale Water District and one that proved robust during the recent quakes.

The district’s water supply resides in the reservoir behind the Littlerock Dam, through the Palmdale Ditch, which carries water from the dam and in Lake Palmdale, is secured by its own Palmdale Dam.

General Manager Dennis LaMoreaux provided an overview of security for these supplies for the District’s board on July 8, although he could not get into specifics.

For Lake Palmdale, which is the final holding area for water before it is treated for distribution at the neighboring Leslie O. Carter Water Treatment Plant, access to the lake is controlled through the District’s agreement with the Palmdale Fin and Feather Club, which also has someone who lives on site.

Monitoring the water quality is another security measure, LaMoreaux said. Water may be either treated, or not used from that source if the problem can not be treated.

Water quality is similarly monitored twice a day along the length of the Palmdale Ditch, which stretches from Littlerock Dam to the lake. If necessary, contaminated water may be diverted before it enters the lake.

The District also has precautions in place for earthquakes, something which took on new importance with the recent earthquakes on July 4 and 5.

Following each temblor, staff inspected the facilities and found no damages, LaMoreaux said.

Water was prevented from flowing through the Palmdale Ditch after the quake on Friday, as it was dark and staff wanted to be able to inspect the ditch in the daylight the next day.

After Saturday’s full inspection, a few areas of the ditch needed repairs, but it is not clear if they were due to the earthquake or other wear, he said.

“All in all we were pretty lucky,” LaMoreaux said.

The Palmdale Dam was first built in 1886, then rebuilt in 1924 and again in the 1960s. Because the San Andreas Fault runs nearby, the dam itself is constructed differently and is designed to withstand a horizontal offset of 26 feet and a vertical offset of five feet, LaMoreaux said.

“It doesn’t mean that it won’t leak, but it won’t collapse,” he said.

As a flood control measure, the district controls land in a small valley to the east of the lake that can be used to hold all the water in the lake should the dam fail. There is a dike and a small cache of materials to be used to close off the valley in an emergency.

The water in that valley could then be slowly drained off through a culvert in a controlled manner, he said.

The district also maintains special monitoring of the dam, part of the approval process when the latest dam rebuild was approved by the state.

After the flooding below the Oroville Dam two years ago when the spillway failed, the state passed new laws requiring all dam owners to update their inundation maps and emergency plans.

Palmdale Water District has completed drafts of these that are in the final comment stages with the state, LaMoreaux said.

To help maintain water quality in the lake, a diversion ditch to the west and south of the lake is in place to prevent local runoff from getting into the lake water supply. This way, the only water in the lake itself is from the State Water Project, carried through the California Aqueduct, or from Littlerock Dam or the rain which falls directly on the lake’s surface, he said.

As another emergency preparation, the District has built up the inventory levels for its materials for repairs, as it may be difficult to get supplies following a disaster.

“We’ve done a lot to be prepared,” LaMoreaux said.

Director Gloria Dizmang had requested a report on security for the District’s water supply, she said, because she wanted to reassure customers they were on top of the issue, and that they do have ways of testing the water and ensuring its safety.

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