Littlerock Dam

Associated Press

Littlerock Dam, as seen in this Antelope Valley Press photo from February 2017. The Palmdale Water District is moving closer to increasing its water storage capacity by removing more than a million cubic yards of sediment from the reservoir behind the dam.

PALMDALE — The Palmdale Water District is moving closer to increasing its water storage capacity by removing more than a million cubic yards of sediment from the reservoir behind the Littlerock Dam.

On Monday, the Board of Directors unanimously, and without discussion, approved a $1.6 million contract with Aspen Environmental Group for work involved with the design, permitting and construction of the project over the next five years.

The Littlerock Reservoir Sed­i­ment Removal Project has been in the works for more than 25 years. It calls for removing more than 1.16 million cubic yards of sed­iment that has built up behind the dam since 1992, reducing the water storage capacity by 500 acre-feet, according to District off­ic­ials.

An acre-foot is 325,851 gallons, or approximately the amount of water a typ­ical Antelope Valley house­hold used in one year, be­fore the last drought reduced usage.

The reservoir collects rain and snow melt from the watershed in the San Gabriel Mountains and is one of three sources of water for the District. The others are groundwater pumped from wells and State Water Project water carried through the California Aqueduct.

The first phase of the project was con­struction of a sub­terranean grade control structure, which began in October 2018 and was completed early last year.

The grade control struc­ture was required before sed­iment removal could begin, in order to shore up the ground to prevent erosion once sediment is taken out of the stream.

The next phase of the project will involve renewing permits with the California Department of Fish and Wildlife, Lahontan Regional Water Quality Control Board and the US Forest Service.

It will also include designing the grading plans for removing sediment over a three-to-five-year period, to be updated every year, according to the staff report.

The consulting contract includes these services, plus providing biological and construction inspection.

Aspen Environmental Group was one of two companies with qualified proposals for the project in answer to a request for proposals from the District. They were chosen for recommendation to the Board based on experience, availability and lower proposed fee by almost $740,000, according to the staff report.

The firm has already been working with the District on earlier aspects of the project, including biological surveys and the biological assessment in regards to the endangered arroyo toad.

Last year, they assisted in the emergency sediment removal due to debris from the Bobcat Fire, by conducting surveys, reviewing plans and obtaining permits, according to the proposal.

The District received a good response to that emergency project to remove 19,000 cubic yards of sediment following the Bobcat Fire, which means interest is promising for removal of the project’s first 120,000 cubic yards later this year, General Manager Dennis LaMoureaux said in his report.

With a consultant named to oversee the work, next up will be finding the contractor for the removal work itself, he said.

The project has been awarded more than $1 million in grant funds for the project through the Antelope Valley Integrated Regional Water Management Plan, according to LaMoureaux’s report.

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