The Pennsylvania Department of Environmental Protection (DEP) plans to raise fees it levies on operators of unconventional wells, but did not say by how much.

In a notice published in last Saturday’s edition of the Pennsylvania Bulletin, the DEP said it is required to review the fees every three years. “The current fee review indicates the need for a fee increase to provide for the administration of the oil and gas program,” it said.

The notice also said the DEP intends to amend environmental protection performance standards for conventional oil and gas operators, which are codified in Chapter 78, a controversial portion of the Oil and Gas Act, the 2012 omnibus Marcellus Shale law also known as Act 13.

“The particulars of the fee package have not been determined yet,” DEP spokesman Neil Shader told NGI’s Shale Dailyon Monday. Marcellus Shale operators are currently levied a $5,000 permit application fee by the DEP.

Democratic Gov. Tom Wolf pledged to tighten regulations on operators in 2015. At the beginning of 2016, the DEP attracted widespread criticism from legacy producers, trade associations and state lawmakers from both parties when, after more than four years of work, the agency drafted separate regulations for conventional and unconventional operators.

That summer, a budget-related compromise between Wolf and Republican lawmakers allowed the DEP’s rules on unconventional wells to move forward, but legislation on conventional wells was scrapped.