WASHINGTON (NEXSTAR) — The Chesapeake Bay is the largest estuary in the world. For years, states that provide the Bay’s watershed—Maryland, Pennsylvania, West Virginia, Delaware, New York, and the District of Columbia—have been working with varying success to improve the health of the bay.

Experts say there’s been some progress, but there’s still a long way to go.

Maryland Gov. Larry Hogan recently called out the state of Pennsylvania for not moving quickly enough to end runoff and sewage pollution. Hogan wants action from his northern neighbor and the Environmental Protection Agency (EPA) to hold the state accountable.

“There’s a 600-pound gorilla in the room. It’s Pennsylvania’s inability to fund its plan,” Chesapeake Bay Foundation President William Baker said. “They say they are $320 million per year short of implementing their plan.”

Baker and representatives from six states met Wednesday to develop plans to continue efforts to get the bay cleaned up by 2025.

Patrick McDonnell of Pennsylvania’s Department of Environmental Protection says his state has a grip on the issue.

“That’s the entire purpose of the last two years in the plan was putting a plan in place that would allow us to get to the year 2025,” he said.

But Hogan has been critical of Pennsylvania’s efforts to get a grip on pollution washing into the bay from his northern neighbor state.

“More of the pollution that goes into the bay comes from Pennsylvania than comes from Maryland, and we’d like to see some things that we think they can improve upon,” Hogan said.

Maryland will continue to work with Pennsylvania, according to Hogan, but he says Pennsylvania’s got to pay its fair share.

“We’ve invested $5 billion into cleaning the bay and we’re not going to be able to handle the sewage problems in Pennsylvania,” he added.

Experts say the biggest sources of bay pollution coming from Pennsylvania are Harrisburg’s antiquated sewage treatment plant and fertilizers that are washed from farm fields into the Susquehanna River.