Maryland Gov. Larry Hogan’s administration announced Thursday that it is withdrawing its opposition to a Dominion Virginia Power plan to release coal-ash water into a Potomac River tributary after the utility company agreed to stricter testing standards.

“Maryland is supportive of recent agreements in Virginia to increase wastewater treatment protections and monitoring protocols,” Ben Grumbles, Maryland’s secretary of the environment, said in a statement.

“We are engaged in and encouraged by the ongoing discussions with Virginia and Dominion to do even more testing for fish tissue, water quality and sediment in the river beyond the current testing and monitoring in current or soon-to-be-proposed permits,” Grumbles said.

The withdrawal of Maryland’s opposition strengthens what has been a controversial effort by Dominion to comply with a federal mandate to permanently seal coal-ash ponds at its Possum Point plant in Prince William County and other sites in Virginia.

After Maryland and Prince William County opposed the plan to release 215 million gallons of the treated coal-ash water into the Potomac, the company agreed to stricter testing standards than what was called for in a state permit sanctioning the effort.

Those new standards, which include hourly testing for contamination, persuaded Prince William County to withdraw its opposition to the Dominion plan in March.

The Potomac Riverkeeper Network, an environmental group in Washington, continues to oppose the plan.