After four years of public meetings, lawsuits and heated debate, the Los Angeles County Department of Public Works will begin the massive sediment-removal project behind Devil’s Gate Dam in Pasadena at the end of the month.

All together, the county will remove 1.7 million cubic yards of sediment from mostly natural lands within Hahamongna Watershed Park behind the dam, a Pasadena city park.

The main goal is to clear away tons of sediment that has prevented the oldest dam in the county from functioning at its fullest capacity. County engineers say large-scale dredging within the city park is needed to return the nearly 100-year-old dam to full operation.

In its current state, mountain runoff may overflow into its spillway during a major storm, potentially inundating the Rose Bowl, Brookside Park and 447 structures in Pasadena, South Pasadena and parts of Los Angeles.

But even after a compromise was reached in November that reduced the amount of dirt being removed by 30 percent, neighbors and activist groups still are not happy. They say the amount of sediment removed will harm a delicate ecosystem housing endangered and sensitive wildlife.

Project schedule

Brittany Barker, project manager with the Los Angeles County Department of Public Works, said the project will begin at the end of this month or early November, depending on the contractor’s schedule.

Two phases will begin nearly simultaneously: first the removal of invasive plants that harm the habitat, and then the removal of trees, shrubs and all vegetation from the first 50 acres behind the dam. The last 20 acres of vegetation will be removed before the fourth year, around 2022, she said.

Also in the next few weeks, the county will turn dirt hiking trails on the east side of the park into paved roads to allow for trucks to exit onto the east-west section of Oak Grove Drive, where diesel dump trucks can turn left from 7 a.m. to 10 a.m. and avoid La Canada High School and residential streets. After that, trucks can turn right and cross over the dam, take Berkshire Place or other major streets to enter the 210 Freeway to dump sites in Irwindale and Sunland.

Actual loading of dirt and sediment onto dump trucks will begin in April and run through October or November, depending on weather conditions, every year during this time frame for four consecutive years, Barker said.

Residents’ concerns

Neighbors and activist groups are accusing the county of not abiding by the Board of Supervisors action and are asking for a more environmentally sensitive approach in the eleventh hour, one that appears to be falling on deaf ears.

“We tried to negotiate a settlement,” Tim Brick, Pasadena resident and managing director of the Arroyo Seco Foundation, said. The foundation sued the county but won only minor concessions, failing to stop the project. “They didn’t listen to anything we said and Supervisor Barger backed them up.”

The Arroyo Seco Foundation and some members of the Altadena Town Council collected 2,858 signatures on a petition presented last week to Supervisor Kathryn Barger, demanding a reduction in a project that will involve 400 trucks per day and take more than four years to complete.

Though the residents won a victory with the downgrading of the scope from 2.4 million cubic yards, the “footprint” to be dug out by bulldozers and other power equipment remains at 70 acres, albeit with some restoration and restructuring of the Arroyo Seco streambed, according to the county and other sources.

Under the revised plan, the number of dump trucks hauling out debris did not go down. The length of the project went from five years to four years.

“They will do 70 acres, permanently killing all the vegetation on 50 acres,” Brick said during a phone interview Monday. “If you do that, if you destroy the prime habitat in the stream zone — you won’t have anything healthy.”

Activist groups thought Barger’s motion would include less damage to a makeshift ecosystem emerging within backed up storm waters originating from the San Gabriel Mountains over the past 10 years.

The habitat supports plants and wildlife, including a pair of the endangered least Bell’s vireo, a small, grayish colored bird all but extinct from North America.

Other sensitive species that call Hahamongna home include: yellow warbler, southwestern pond turtle, coast range newt and the two-striped garter snake, according to the project’s Environmental Impact Report.

“The plan should be resilient, informed by science and work to re-establish the natural systems that make the Arroyo Seco one of the key tributaries to the LA River. It should protect the wildlife corridor and habitat for endangered species … and save the trees that absorb CO2, diminishing the greenhouse effect and improving air quality,” according to the petition.

The county has answered back, saying they have altered the project to save as much habitat as possible and will work to restore the 70 acres as “an enhanced habitat and recreational opportunity.”

In addition, “the slopes within the basin will be re-contoured to provide increased opportunities for wildlife foraging and to encourage species diversity within the restoration area,” the county said in a written statement.

Closures, construction will impact neighborhoods

Blair Hansen, who lives in the Vista Laguna Terrace Neighborhood on the edge of the park and dam, says hundreds of families will lose access to the trails they walk with their dogs. Children riding to St. Francis and La Cañada high schools won’t be able to ride through the park but have to take the busy streets.

“We know they have to do some sediment removal but we wanted it done in in a more thoughtful, environmentally conscious way,” she said during a phone interview Monday. “The day they come in and remove that vegetation people will look on in horror.”

The county will send fliers announcing the exact dates of construction to households within a 2,000-feet radius, Barker said.

She and others will knock on doors and leave literature on the project to closer-in homes more directly affected. Notices of trail and road closures will be listed, she said.

The public can call Barker during business hours at 626-458-4971 or a 24-hour hotline number: 1-800-675-HELP (4357). More information is available at www.devilsgateproject.com.