Conservation project aims to capture rainwater, replenish underground aquifer

From The Los Angeles Register

Sept. 14, 2014

Updated 11:42 p.m.

ARCADIA – As water levels reach historic lows across Los Angeles County, a new project aims to replenish the Main San Gabriel Groundwater Basin by capturing excess rainfall during wet seasons.

The plan will help reduce a dependency by the San Gabriel Valley on imported water, according to county documents.

The Los Angeles County Department of Public Works will build a pipeline connecting the Peck Road Spreading Basin in Arcadia and Monrovia to a segment of the San Gabriel River, where rainfall can seep underground to recharge the groundwater basin.

“This Peck Road Spreading Basin upgrade will allow water to percolate faster underground, and it’s an innovative way to conserve water otherwise lost to the ocean,” said Keith Lilley, a Public Works civil engineer.

The project, which will run 1.5 miles of pipe underground along Clark Street in Arcadia, is slated to break ground next year and be completed in 2016, officials said.

It will cost around $6.5 million and is being financed with grant money received by the county’s Integrated Regional Water Management Plan, Lilley said.

Currently, excess water from Peck Lake makes its way into the Rio Hondo, where the storm drain channels are concrete-lined and carry water straight to the ocean.

With the new pipe, excess water will be pumped to a segment of the San Gabriel River channel where the bottom is soft earth and the water can seep underground, replenishing nearby wells.

Between 30 percent and 40 percent of water consumed by Los Angeles County is pumped from the groundwater supply, Public Works officials said.

“In a year like this, you’d really get nothing because of the drought and water levels being lower than years past,” Lilley said. “What we did was go back and look at historical data, and modeled how much this pipeline would have conserved in different years of rainfall.”

Based on those calculations, engineers estimate the pipe will help collect 1,800 acre-feet of water in average years and 3,400 acre-feet in wet years. One acre-foot provides a year’s worth of water to two families of four, officials said.

The Peck Road Spreading Basin originally was designed to let water seep into the groundwater table, part of a network that feeds one of California’s largest aquifers, the Main San Gabriel Groundwater Basin.

But as years of rain caused sediment to slide in from the Santa Anita wash, the bottom of the lake became clogged, slowing the underground water absorption process and causing the Spreading Basin to overflow.

To remedy this, the pipe project also will remove 101,000 cubic yards of sediment. Once completed, the lake will see improved absorption into the aquifer, officials said. If the water level rises above 300 feet, the pump mechanism will be activated and siphon excess water to the San Gabriel River.

“It sounds like a good idea,” said Nikola Hlady, a planning and policy fellow at the nonprofit group Amigos De Los Rios.

The organization frequently partners with the department to revitalize parks, trails and open spaces. From 2005 to 2010, Amigos De Los Rios helped convert Peck Road Water Conservation Park from a former gravel quarry to a veritable green space with native plants, habitats for local wildlife, recreational areas for fishing and birdwatching and paths for hikers and cyclists.

Their latest project – the Emerald Necklace – is a 17-mile continuous loop of parks and greenways connecting 10 cities along the Rio Hondo and San Gabriel River.

The possibility of developing a bike path on top of the pipeline project has been discussed by department engineers.

“Looking at the green opportunities presented by this project, there was an idea to connect the two bike paths as one of the elements and have it be the ‘clasp’ of the Emerald Necklace,” Lilley said.

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