Hydro · Analysis

Eagle Mountain: the iron mine the desert could turn into a battery

A licensed but unbuilt pumped-storage project would turn two abandoned iron-ore pits near Desert Center into a water battery for the LA grid. The catch is not megawatts. It is desert groundwater and permitting time.

BY THE RENEWABLE ENERGY LA EDITORS · FILED OCTOBER 24, 2026 · 6 MIN READ ·

How a pair of mine pits becomes a battery

If you run rooftop solar anywhere in the basin, you already know the daily problem in your own meter: the panels pour out power at noon and the house goes quiet until it fills up again at six. The grid has the same problem at scale. California makes more solar than it can use in the early afternoon, then scrambles for supply after sundown, which is why storing midday power for the evening has become the quiet obsession of nearly everyone who keeps the lights on here.

One answer sits about 150 miles east of downtown, near Desert Center, in two abandoned iron-ore pits that Kaiser Steel dug generations ago at Eagle Mountain. The plan, licensed but never built, is to turn those pits into a battery made of water: pump water up to the higher pit when power is cheap and plentiful, let it fall back down through turbines when the basin needs it. On paper it would hold roughly 1,300 megawatts, per the developer's filings, enough to matter to the grid that serves your block.

The idea is old, and the basin already runs on it

Pumped storage (storing energy by moving water between two reservoirs at different heights) is the oldest grid-scale battery in the country, and Los Angeles already leans on one. The Castaic plant north of the city, tied to the California Aqueduct, holds on the order of 1,250 megawatts and has cycled water uphill and back since the 1970s. Eagle Mountain would copy that idea out in the open desert: the lower pit holds the water, the upper pit sits a few hundred feet higher, and the same water moves between them over and over.

The appeal is that the holes are already dug. Kaiser's miners moved the rock long ago, so the project would not carve fresh reservoirs into untouched land. The developer, Eagle Crest Energy, has pitched it for years as a second Castaic for a grid that now swings much harder between a midday solar glut and an evening shortfall than it did when the first one was built.

The cost that is not measured in megawatts

A pumped-storage plant in the desert leaks water as well as energy. Open pits in the Chuckwalla Valley sun evaporate what they hold, so the project would need a large initial fill drawn over several years and then a steady makeup draw after that, all of it pulled from desert groundwater. That is the number a ratepayer rarely sees in a press release, and it is the one that has drawn the most fire. At last public report the annual makeup draw was estimated in the thousands of acre-feet, a figure that has been argued over in the record for years.

That groundwater does not belong only to the project. It is the same basin that feeds springs, wildlife, and a scattering of desert communities, and Joshua Tree National Park sits close to the site. The honest summary is that the engineering is proven and the water accounting is not settled: how much the pits really lose, how fast the aquifer recovers, and who else has a claim on it are the questions that have kept the project on paper.

A federal license that has outlived its schedule

The federal license is real. The Federal Energy Regulatory Commission issued Eagle Crest a license good for about half a century in the mid-2010s, which is the step most people assume is the hard one. It was not. Construction deadlines in the license have come and gone, and the company has had to seek extensions more than once, because the pieces that turn a license into a power plant, firm financing, a buyer for the power, water in hand, and a line to carry it to the basin, have not all lined up at the same time.

The players who matter now are mostly outside FERC. The National Park Service and conservation groups watch the groundwater and the park boundary. The California Independent System Operator, which runs the grid, would have to interconnect the plant and schedule it. And LADWP and the basin's other buyers would have to decide that long-duration storage out in the desert beats batteries closer to home. Until one of those buyers commits, the license is a permit to build something nobody has yet agreed to pay for.

Worth watching this month

1. Watch the Eagle Mountain docket in FERC's eLibrary for any new construction-deadline extension or, more tellingly, a license-surrender filing, which would be the clearest sign the project is ending rather than stalling.

2. Watch whether the project holds its spot in the California ISO interconnection queue, since quietly dropping out of the queue would signal the plant is losing momentum even while the license stands.

3. Watch updates to the Chuckwalla Valley groundwater sustainability plan under the state's groundwater law, because tighter pumping limits in that basin would change the project's water math directly.

4. Watch LADWP's long-term resource planning for whether long-duration desert storage is named at all, a routine document that would nonetheless show whether a basin buyer is still interested.

5. Watch for any National Park Service scoping or comment window tied to the site, which tends to surface only when something is actually moving.

Where this dispatch reads

Federal Energy Regulatory Commission, eLibrary (.gov), elibrary.ferc.gov/eLibrary/search, Search the Eagle Mountain pumped-storage docket for the license, construction-deadline filings, and comments. This is the primary federal record.
National Park Service, Joshua Tree National Park (.gov), www.nps.gov/jotr/index.htm, Park boundaries, desert springs, and groundwater concerns near the project site, from the agency that manages the land next door.
California Independent System Operator (grid operator), www.caiso.com, The grid operator for most of the state; its interconnection queue and daily supply-and-demand data show why evening storage is in demand.
California Department of Water Resources, SGMA groundwater (.gov), water.ca.gov/programs/groundwater-management/sgma-groundwater-management, State groundwater-sustainability rules that govern the Chuckwalla Valley basin the project would draw from.
Los Angeles Department of Water and Power, www.ladwp.com, The basin's largest public utility; its resource planning shows whether a buyer for long-duration desert storage exists.
Eagle Crest Energy Company (developer), www.eaglecrestenergy.com, The developer's own project description for the design, reservoir layout, and stated capacity; read it as the applicant's case, not a neutral source.

Questions readers have asked

Is Eagle Mountain actually being built?

No. It holds a federal license but has not broken ground, and the construction deadlines in that license have been pushed back more than once.

How is this different from the big lithium batteries going in around the state?

Lithium batteries typically store a few hours of power. Pumped storage can run for many hours at a time, but it needs the right terrain and, in this case, a lot of scarce desert water.

Where would the water come from?

From desert groundwater in the Chuckwalla Valley, drawn to fill the pits and then to replace what evaporates. That draw is the main reason the project is contested.

Would it power my house in Los Angeles?

Only indirectly. It would feed the regional grid that serves the basin rather than any single home or neighborhood.

Why put it next to Joshua Tree?

Because the old Kaiser iron-ore pits are already there, which saves digging new reservoirs. The park boundary sits close by, which is exactly what raises the environmental stakes.