The operators of nearly 250 disposal wells in western Oklahoma are being asked to decrease the volume of oil and gas wastewater they inject underground, in response to a surge in earthquake activity.

The Oklahoma Corporation Commission’s (OCC) Oil and Gas Conservation Division (OGCD) said on Tuesday that the plan covers 5,281 square miles and 245 disposal wells that inject wastewater into the Arbuckle formation. The link between underground wastewater disposal and the record number of earthquakes recorded in the state in recent years was officially recognized by the Oklahoma Geological Survey last year.

In conjunction with the 191,000 barrel a day reduction plan launched in Fairview recently, the total volume cutback for the entire area will be more than half a million barrels a day, or about 40 percent, said OGCD director Tim Baker.

Baker said that the significant rise in seismic activity in the region demands a regional response.

“We have taken a number of actions in the Medford, Fairview and Cherokee areas,” he said. “However, there is agreement among researchers, including our partners at the Oklahoma Geological Survey, that the data clearly underscored the need for a larger, regional response. That is why, even as we took actions in various parts of the region in response to specific earthquake events, we were already working on a larger plan.”

Although the latest action comes in response to the continued seismicity in the area, it also includes areas that are not yet experiencing major earthquakes.

“This plan is aimed not only at taking further action in response to past activity, but also to get out ahead of it and hopefully prevent new areas from being involved,” Baker said.

According to OGCD, the plan will be phased in over four stages and two months as recommended by researchers, who caution against sudden pressure changes.

It was also announced this week that environmental organization the Sierra Club has filed a federal lawsuit against three energy companies engaged in hydraulic fracturing in Oklahoma, demanding a significant reduction in the amount of wastewater injected underground.