The US Environmental Protection Agency has approved an aquifer exemption for the Arroyo Grande oil field near San Luis Obispo. This enables Sentinel Peak Resources, the current owner of the oil field also known as Price Canyon, to move forward with a planned expansion of wells for both enhanced oil recovery and dispoal of wastewater, or "produced water."
In a decision dated April 30, the director of EPA’s water division said the underground formation beneath the oil field does not, and will not in the future, serve as a source of drinking water due to the presence of “commercially producible quantities of hydrocarbons.”
With the aquifer exemption approval, the oil company is one step close to being able to inject wastewater underground into a larger area than before.
Over 100 neighbors within one mile of the oil field get their drinking water from domestic wells, and many had fought the ruling, fearing that wastewater injected underground would contaminate their wells. Nine of those domestic water wells are within a quarter-mile of the newly-exempted area, and the nearest public water system well is just under one mile. But according to the EPA and state agencies, those well are “hydraulically isolated” from the exempted aquifer by the Arroyo Grande fault.
There are 207 Class II enhanced oil recovery wells and 16 disposal wells within the newly-exempted area.