A judge in Oklahoma has determined that a lawsuit filed after an earthquake, currently the second most powerful temblor recorded in the state’s history, can move forward with class action status.

Meanwhile, state regulators on Wednesday issued a directive for operators to shut in four wastewater disposal wells and curtail injection volumes at 21 others, after a 3.7-magnitude earthquake struck last week near Crescent in Logan County.

The directive by the Oklahoma Corporation Commission (OCC) and its Oil and Gas Conservation Division (OGCD) calls for three operating disposal wells targeting the Arbuckle formation to cease operations. It also directed a fourth well not be allowed to resume operations. All the wells are within a three-mile radius of the earthquake that struck 12 kilometers (7.5 miles) north of Crescent on May 17.

The OGCD called for an additional 21 disposal wells within three to 10 miles of the Crescent quake, to make a 20% reduction to average daily volumes that are above 500 b/d. The reduction is in addition to any past directives that reduced volumes.

“Based on the last 30-day average, this action is calculated to result in an overall further reduction in Arbuckle disposal of 2,848 b/d,” the OGCD said. “Further, operators of those wells which have reduced their depth to avoid injecting too close to the basement rock will be required to verify the well’s bottom hole plug integrity.”

The directive applies to 25 disposal wells in total, of which 20 have operated within the last 30 days. Of the 25 wells, 13 are operated by White Star Petroleum LLC and five are operated by Stephens Energy Group LLC. Kirkpatrick Oil Co. Inc. is listed as the operator of two wells, as is Dorado E&P Partners LLC. Berexco LLC, Longfellow Energy LP and Stephens Production Co. each operate one of the three remaining wells.

Of the four wells ordered shut in by the directive, two are operated by Stephens Energy and two are operated by White Star.

In the lawsuit, Judge Lori Walkley in a summary order filed last Friday ruled that class action status is appropriate for the case Jennifer Lin Cooper v. New Dominion LLC et al, No. CJ-2015-24, which is in Lincoln County District Court.

“In particular, this court finds that the questions of law or fact common to the members of the class predominate over any questions affecting only individual members, and that a class action is superior to other available methods for fair and efficient adjudication of the controversy,” Walkley wrote.

The lawsuit was filed in 2015, in response to a 5.7-magnitude temblor that shook the area around Prague, OK, on Nov. 6, 2011. Two people suffered minor injuries from the earthquake, which also damaged several buildings. A 4.8-magnitude aftershock was recorded two days later. At the time, the Prague temblor was the largest recorded in Oklahoma history; it was surpassed by a 5.8-magnitude earthquake that struck the Pawnee, OK, area on Sept. 3, 2016.

According to attorney Scott Poynter with the Little Rock, AR-based firm Poynter Law Group who is representing Cooper, Walkley’s order will allow citizens with residential or business properties in nine counties to participate in the class action. Poynter will serve as counsel for the class. The counties are Cleveland, Creek, Lincoln, Logan, Okfuskee, Oklahoma, Payne, Pottawatomie and Seminole.

Poynter said the case is scheduled for trial beginning Sept. 10. It is expected to last two weeks. “If plaintiffs are successful in September, anyone within the class area will only have to prove their damages related to the earthquakes to win a judgment against New Dominion,” he said.

Regulators with the OGCD have been attempting to mitigate induced seismic activity across the state since 2015. The agencies have focused on wastewater injection wells targeting the Arbuckle formation — especially the Mississippian Lime and the Hunton Dewatering play — within a 15,000-square mile area of interest in the state.

Scientists with the Oklahoma Geological Survey attribute many of the recent quakes to the disposal of extremely salty water — a byproduct of oil and gas production — in underground injection wells.

OCC records show that Tulsa-based New Dominion operates 41 wastewater disposal wells in the state. Of those, 14 are in Seminole County, while eight are in Pottawatomie County and six are in Oklahoma County. Lincoln and Okfuskee counties each have five of the company’s disposal wells, while the remaining three are in Hughes County. Twenty-eight wells are listed as targeting the Arbuckle and other formations.