The verdict is a setback for companies seeking to take advantage of the area’s energy resources since it effectively bars any drilling on two tracts of land leased for oil and gas development in 2011 by the federal Bureau of Land Management.

Those tracts top the sedimentary rock bed — known as the Monterey Shale Formation — are estimated to contain more than 15 billion barrels of oil, which totals 64% of all shale oil reserves in the country.

The oil must mainly be extracted by hydraulic fracturing, a.k.a fracking, where large amounts of water, sand and chemicals are injected into shale formations to push hydrocarbon fuels to the surface.

Grewal wrote the BLM “did not adequately consider the development impact of hydraulic fracturing techniques … when used in combination with technologies such as horizontal drilling.”

“The potential risk for contamination from fracking, while unknown, is not so remote or speculative to be completely ignored.”

The BLM must conduct a more thorough environmental review before it allows drilling to happen on the leases.

Image: dsearls, Creative Commons licence, Flickr