Calabasas tries underground water storage

BUILD HERE—A cistern will go below ground at Gates Canyon Park. RICHARD GILLARD/Acorn Newspapers

BUILD HERE—A cistern will go below ground at Gates Canyon Park. RICHARD GILLARD/Acorn Newspapers

Los Angeles County is designing a novel way to help Calabasas treat and reuse stormwater that carries pollutants into the Pacific Ocean.

County officials hosted a community forum Nov. 3 at the Agoura Hills/Calabasas Community Center to answer questions and address concerns about the $8-million drainage system and underground storage cistern that would be installed beneath Gates Canyon Park. The drainage will redirect polluted

City officials are working with Los Angeles County to design a stormwater treatment facility that will be installed beneath Gates Canyon Park next year, and Alex Farassati, environmental services supervisor for Calabasas, said the project will save more than $15,000 in annual irrigation costs.

“The volume of water we can capture and save kind of equals the water we use on an annual basis for irrigation. We have water for drinking; that’s a separate line. Right now, we use reclaimed water for irrigation for the park,” Farassati said.

“With this system, we will not be irrigating using the reclaimed water anymore, or we can just use it as a backup, but we will be mainly using the treated rainwater for the irrigation.”

Not everyone is enthusiastic. Calabasas resident Carl Ehrlich said storing water under the park, which is at the foot of a hill, could weaken the soil and potentially cause a landslide.

Why bother?” Ehrlich said. “My opinion is there’s no advantage here. You’re not replacing potable from the sprinkler system. You’re putting water underground. Why not just filter the water and put it in the storm drain?”

The project is expected to divert 1.15 million gallons of storm water each year. By saving that water, Calabasas is also diminishing its dependence on the Las Virgenes Municipal Water District, which supplies Calabasas with water for drinking and reclaimed water for irrigation.

The facility is being designed by Los Angeles County employees. It will come at no cost to Calabasas; instead, it will be funded by state grants and the Los Angeles County Flood Control District.

“(Calabasas) is the biggest winner here,” Farassati said. “We’re complying with the California Water Quality Act. We’re not spending a dime, and we’re getting free water.”

The system’s design is about 60 percent finished. Once it’s completed and the regulatory permits are obtained, construction is expected to begin next fall. Most of the park will remain open throughout construction.

“We are going to shut down probably 10 to 20 percent of the park. And we’re going to stay out of the park during the active months, June through August, when it’s utilized more,” Farassati said. “We’re going to focus on construction from September to the end of May (2019).”

Los Angeles County civil engineer Giles Coon, who oversees the project, said Gates Canyon Park was chosen because a nearby storm drain captures runoff from more than 100 residential acres in the Mountain View Estates neighborhood.

“That storm drain allows us, by diverting the flows into our cistern, it allows us to capture all that runoff and treat it. It’s really what makes the project work,” Coon said. “Without the storm drain we have no way to capture those kinds of flows in that kind of an area.”

Besides putting stormwater to good use, the treatment facility will help protect the environment.

“By capturing this water and treating it, we’ll keep pollutants from getting into Las Virgenes Creek and then downstream into Malibu Creek,” Coon said. “We have the project laid out to where we’re not going to impact the environment. Pretty much everything of substance will be underground. All the aboveground amenities, the turf, the fields, they’ll be replaced. We’re retaining all those benefits.”

The drainage project is an effort to improve the quality of water flowing out of the city in compliance with the Enhanced Watershed Management Program, a Los Angeles County program intended to minimize water pollution and address water supply issues. stormwater runoff that normally flows into Las Virgenes Creek and to the ocean. Instead, the water will be treated and stored in a cistern buried beneath the park and later used for irrigation.

Giles Coon, the L.A. County engineer overseeing the project, said the goal is to help Calabasas meet the water quality objectives set by the federal Environmental Protection Agency and the Los Angeles Regional Water Quality Control Board.

Water that flows through storm drains is normally carried straight to the ocean, without treatment. But today, the EPA is holding cities responsible for the oils, toxins and other refuse that finds its way into the water.

In Calabasas, the stormwater runoff from 105 acres of residential neighborhood will be cleansed and stored in the Gates Canyon Park cistern.

The cistern underneath the Gates Canyon play fields will be 11 feet deep and able to hold the equivalent of two Olympic swimming pools worth of water. When the cistern is full there will be enough water to irrigate Gates Canyon Park for about 12 weeks, officials said.

The work will be paid for by a combination of state grants and L.A. county programs. Calabasas tax dollars won’t be invested in the construction, but the city will be responsible for the materials and maintenance work used to treat the stormwater.

Coon said plans should be finished by spring of 2018 and that construction should begin later in the year.