Committee Told ‘Big Dig’ On Track To End This Year

The chair of the Hahamongna Watershed Park Advisory Committee on Tuesday told Pasadena Now that a local sediment removal project is ahead of schedule and is expected to end in November.

The committee received an update from officials with the county’s Public Works Department on efforts to remove 1.7 million cubic yards from the area around the 100-year-old Devil’s Gate Dam.

Local critics have dubbed the project the “Big Dig” due to its comparisons to a more than 20-year road and tunnel construction megaproject in Boston that negatively impacted traffic through local neighborhoods.

“It was announced at our meeting that the project is running ahead of schedule and the dig may be completed by sometime in November of this year, which is one year ahead of the original plan,” said Chair Mark Mastromatteo.

Mastromatteo said the coordination between community members, the contractor and the city led to a well run and thoughtfully operated project. 

“ It was accomplished in sync with the needs and concerns of the adjacent residents,” he said. “While, by the very nature of correcting about 30 years of build up of materials from the nearby mountains is going to be disruptive and even jarring to some people, the long term result is a watershed and dam operation that will be maintained and a habitat that is much more native and able to flourish in the years ahead.”

All told, at least 980,000 cubic yards of sediment have been hauled away, according to a recent staff report. 

Last month, the county announced that steps were being taken to lessen the negative impacts on neighborhoods near the project.

The department upgraded its 2021 sediment hauling fleet in an effort to reduce truck emissions.

Other steps taken include pre-watering sediment prior to the loading of the trucks, watering all loaded trucks before they leave the reservoir to control material from blowing out of truck beds, maintaining tire wash stations to remove dirt from tires and undercarriages of trucks, and using street sweepers to  continuously sweep paved surfaces, including the truck access ramp and the local sediment hauling routes.

Ninety-five trucks are scheduled to be used to make a maximum of 425 roundtrips daily, according to a report originally included in the City Council’s Public Safety Committee (PSC) agenda.

Hauling hours are from 7 a.m. to 3:30 p.m. Monday through Friday.

In addition to providing flood relief to communities that have endured more than a decade of elevated flood risk along the Arroyo Seco, the project will establish a permanent stormwater maintenance area that allows for the creation of 70 acres of enhanced habitat and recreational opportunities.

The project is a four-year effort to increase flood protection for communities downstream of Devil’s Gate Dam and restore habitat within a popular section of the Arroyo Seco Watershed.

According to Los Angele County Supervisor Kathryn Barger, the project is ahead of schedule and native plants are already being replanted.

Devil’s Gate is the oldest dam constructed by the L.A. County Flood Control District, providing flood protection for Pasadena, South Pasadena and Los Angeles.

A large amount of sediment had not been removed from Devil’s Gate since 1994 when workers hauled out 160,000 cubic yards. The Station Fire in 2009 then dumped a million cubic yards of soil and debris into the basin.

The Board of Supervisors voted on July 7 to approve a settlement between L.A. County, the Arroyo Seco Foundation (ASF) and the Pasadena Audubon Society (PAS) that reduced the negative impacts of the project on endangered bird species in the area.