The Hogan administration is rolling back a 4-year-old regulation that required less-polluting but costlier septic systems for all new homes in Maryland that aren’t connected to sewers. The move seems sure to please builders, rural politicians and their constituents, but critics say it’s a step backward in trying to clean up the Chesapeake Bay.

Gov. Larry Hogan told the Maryland Association of Counties annual meeting in Ocean City that his administration would exempt new homes and commercial dwellings in most of the state from having to install the high-tech septic systems, which are designed to reduce the amount of nitrogen from human waste that’s allowed to escape. Last week, the state Department of the Environment published the proposed regulatory change in the Maryland Register.

The state would still require systems using “best available technology” in new construction within the state’s “Critical Area,” a 1,000-foot strip of land bordering the Chesapeake Bay and its tidal tributaries. Those systems reduce the amount of nitrogen from human waste that’s allowed to seep into groundwater, and ultimately to streams, rivers and the Bay.

Households using conventional septic systems leak up to 10 times as much nitrogen compared with homes hooked up to a modern municipal sewage treatment plant, state officials have long said. The high-tech systems reduce the nitrogen release by about half, but they cost several thousand dollars more to install and operate than conventional systems, and need more frequent maintenance.

Realtors, home builders and rural legislators have complained the mandate hurt rural economies because having to install high-tech systems drove up home prices.

In a press release about Hogan’s speech, the governor’s office called the septic requirement a “cost-prohibitive burden” for homeowners and businesses.

Ben Grumbles, the secretary of the Maryland Department of the Environment, called the change his agency is making “a measured step to reduce regulatory burden and build public support for a smarter and more effective septics program across the state.”

In a brief interview, Grumbles acknowledged that the rollback would allow more nitrogen pollution to enter the Bay, but he called the increase “insignificant.” He said state officials would figure out how to offset it as they devise a plan for keeping nutrient pollution from increasing with future growth and development in Maryland.

MDE spokesman Jay Apperson said the state would expand its efforts to crack down on failing septic systems and work with local communities to help connect more homes to sewer systems.

In a prepared statement released by the MDE, Grumbles said, “We are customizing the statewide requirement to meet local watershed needs more effectively while still insisting on excellent environmental results.”

The man who had the job before him disagrees.

Robert Summers, who worked at the MDE for 30 years and served as environment secretary under former Gov. Martin O’Malley, said nitrogen from septic systems everywhere, not just those closest to the Bay, threatens water quality.

“I fail to see how it is an unfair regulatory burden on septic owners that they treat their wastewater when those of us on sewage systems are paying more and more for upgrades to collection systems and treatment plants,” Summers said. “The whole population needs to do its share to control pollution. Why should rural residents get a free pass?”

It’s not known exactly how many new homes will be built on septic systems, but most of those with them to date have been away from the Bay. According to the state, of about 500,000 septic systems in Maryland, only about 10 percent are near the Bay and its tidal tributaries. Since 2013, an average of 703 homes have been built annually outside the Critical Area, the MDE said.

In an economic analysis of the draft regulation that was provided to a legislative committee, the MDE predicted it would decrease the cost of new housing in those rural and suburban areas where less-polluting septic systems are no longer required. On average, high-tech systems cost $7,500 more than conventional ones, the MDE estimated, but they also require electricity to operate, costing about $112 per year. After their first five years, the more sophisticated systems require $150 to $300 a year in maintenance, the MDE said.

Systems using “best available technology” for treating nitrogen had been required only in the Critical Area before. But in 2012, the MDE extended the mandate statewide. At the time, Summers said it was needed to reduce water pollution expected from future growth in rural areas that would not be served by sewer systems.

The statewide regulation came on the heels of legislation passed that year at O’Malley’s urging that also restricted where development could occur that relied on septic systems. That law, aimed at preserving farmland and limiting suburban sprawl, remains in effect, though rural areas also have complained that it has hurt development.

The septics issue has long been controversial because less-polluting systems cost more. And nitrogen from such systems is generally not as large of a source of Bay pollution as runoff from farms, stormwater and discharges from sewage treatment plants.

Even with the rollback, MDE spokesman Apperson said that officials expect Maryland to meet its 2017 nutrient reduction goals under the Bay pollution diet, or total maximum daily load, set by the U.S. Environmental Protection Agency for all watershed states.

Dropping the requirement for less- polluting septic systems outside the Critical Area will increase the amount of nitrogen reaching the Bay by a total of 50,000 pounds over the next decade, the MDE estimates. State officials say that amounts to less than 1 percent of the remaining nitrogen reductions the state needs to make to comply with the TMDL.

But septic pollution can reach significant levels in some local areas and contribute to increased levels of bacteria that can shut down swimming and make fishing risky.

Making new homes pay for less-polluting septic systems and restricting where they could be built was intended to steer development into urban cores and reduce land fragmentation, said Richard Hall, who was secretary of planning under O’Malley.

Changing the regulations is “just 360 bad,” Hall said. “You’re polluting and you’re not paying to remove that nutrient pollution, unlike the people on sewer, who are paying.”

Bay Journal staff writer Timothy B. Wheeler contributed to this story.