Debris basin’s capacity to increase

Plans to enlarge capacity at the Mulally Debris Basin, which is on U.S. Forest Service land bordering La Cañada in the upper Ocean View area, were released this week from Los Angeles County.

This, after a community meeting last fall with residents, city officials and county representatives to discuss the inadequate capacity of the basin and possible alternatives for a resolution.

The county selected one of three alternatives discussed at the October meeting, a reinforced concrete wall, which would replace the existing structure, according to Valerie De La Cruz, project manager for the county’s water resources division.

The proposed wall will be six feet taller than the existing crib dam structure, De La Cruz said, adding that the “additional height will add additional capacity and protection to the residents downstream.”

The debris basin is significantly undersized and might not be able to provide mud relief in a significant storm situation, according to a report from city staff during the October community meeting at La Cañada City Hall.

The county, at that time, said an additional 5,000 cubic yards of storage would need to be added to the existing 9,400- cubic- yard capacity.

The basin has the potential of affecting about 5,000 local residents, according to information provided by county representatives at that October meeting.

The U.S. Forest Service originally built the basin in the 1960s to control erosion as it was coming down the water coarse, according to Chris Stone, assistant division engineer for L.A. County’s department of public works, who made a presentation at last fall’s La Cañada meeting.

It was further developed as a basin in the 1970s, and a channel system was developed to tie in to the existing storm drain system under city streets, Stone explained.

About seven years ago, the county began working on concepts for a larger capacity basin, because the basin provides only minimal storm water protection; however, without community input during the county’s planning, those plans weren’t well received by residents and were put aside by the county.

Last fall, La Cañada Flintridge Public Works Director Edward Hitti approached county staff and asked for help with increasing capacity for the basin.

Although the initial plan was released this week, the project description is not set to be finalized until July. In coming months, the county will acquire permits and conduct several surveys, studies and analysis, including a traffic technical report is scheduled between July 7 and Aug. 21, and a biological resources analysis between April 20 and Aug. 28.

A public review period is scheduled for Nov. 16 to Dec. 11. Construction is set to begin May 12, 2010 and conclude by Oct. 30, 2010.

The project is expected to cost more than $500,000 in anticipated construction costs alone — which doesn’t include costs for permitting, design, or mitigation — however, cost isn’t necessarily an object for residents, since the project will be paid for by county funds already designated for services of the Los Angeles County Flood Control District, Stone previously said.

La Cañada Flintridge Chamber of Commerce President and CEO Pat Anderson, who lives on Manistee Drive near the mouth of the basin, said Tuesday that she appreciates the county’s efforts in helping ensure the safety of nearby residents and helping the city with risk management.

Anderson previously described a storm several years ago that dumped about 30 inches of rain on the area.

Anderson said the water flowing through the Mulally Debris Basin, “reminded me of Niagara Falls at times.” Although, “the integrity of the basin worked fine, as it was supposed to do,” Anderson added that she’s always concerned about the basin. “Believe me, when it starts to rain, I’m out there watching this thing.”