Large-scale debris removal underway at Eaton Wash Dam

The recent storms brought lots of ash and fire debris into the Eaton Wash Dam in north Pasadena. Now the county is working to clean it out.

Eaton Wash Dam, one of 14 dams managed by L.A. County Public Works, captures storm water that is then cleaned for use as drinking water. The dam also serves as essential flood control, protecting communities downstream.

What’s the issue?

The recent storm sent ash and mud from the Eaton Fire scar in the mountains into the dam. The danger is that the sediment will clog up a valve outlet that allows controlled releases of water to prevent flooding.

If that valve is clogged during the next storm, the dam could breach and flood communities below. The sediment also makes it so the dam can’t capture as much water to store for our drinking supply when the dry season comes.

Does the ash impact our water supply?

The county says it will test the sediment throughout the cleanup effort. So far, they say the sediment has not been found to be hazardous. Most of the sediment came from the mountains, rather than buildings and homes burned in the Eaton Fire, according to the county.

Where does the sediment go?

County workers will truck the sediment to three landfills — in Irwindale, Azusa and Glendale. You can find additional information on the landfills and haul routes here.

The context

As fires become more common and extreme, keeping dams and storm-water-capture projects clean is an increasing challenge — and a strain on limited public works budgets. The county is working on several debris-removal projects across the 14 dams the agency manages. Read more here about how the climate crisis is complicating our water supply.

What’s next

Trucks will operate around the clock clearing debris. The project is expected to cost $13 million, and the goal is to remove up to 500,000 cubic yards of sediment by April — that’s about as much dirt as could fill the Rose Bowl two-thirds of the way to the top.