State rules requiring "offsets" for water pollution from new development have been delayed until next year, Maryland's top environmental regulator told lawmakers Wednesday.

Although the regulations originally had been set for issuance by next month, Environment Secretary Robert M. Summers told members of House and Senate environment committees that there are "more details to be sorted out," mainly over a plan to let developers buy pollution "credits" elsewhere or pay a fee to the state for the costs of offsetting their projects' water-quality impacts.

The growth-offset regulations are required under the Chesapeake Bay "pollution diet" that the Environmental Protection Agency has imposed on Maryland and the five other states in the bay watershed. A new state law aimed at limiting development on septic systems also mandates pollution offsets for any large housing subdivision that would not be connected to a sewer system.

Summers explained that offsets are needed to ensure that population growth and development don't undermine the states' efforts to reduce nutrient and sediment pollution fouling the bay.

One way developers could offset the pollution predicted from their projects would be by paying farmers to plant more nitrogen-absorbing "cover crops or adopt some other conservation measure beyond what the farm itself is required to do to control its own pollution.

Planners project that Maryland could add 478,000 households by 2035, which if not offset could send more than 2 million pounds of nutrient pollution to the bay

State environmental officials first floated draft rules last spring and have been in discussions since with "stakeholders," including developers, local officials and environmentalists.  Developers and local officials want as much latitude as possible to buy and sell pollution credits, or to pay a fee to the state in lieu of having to find any specific offsets.  Environmentalists, though, want limits and oversight to ensure pollution actually gets reduced.

Given the continuing debate among stakeholders, Summers said regulators want to take more time to try to work through their disagreements and concerns.  He said he plans to form a "work group" of agency officials and outsiders to continue talks, with the aim of proposing regulations by October and finalizing them by the end of 2013.

Although the state law limiting septic development directs the Department of the Environment to issue offset rules by the end of 2012, Summers said he was delaying them until next year as well because they're being coordinated with the bay  regulations.

A few legislators voiced concern over the impact of the rules. Sen. Paul Pinsky, a Prince George's County Democrat, suggested that keeping growth from undermining the bay cleanup depends in large part on how well the state's local officials follow the septic-limits law.  The conservation group 1000 Friends of Maryland this week warned that more than a third of the counties appeared to be trying to skirt the law's intent.

Del. Charles Otto, a Republican representing Somerset and Wicomico counties, suggested it was another "attack" on the state's rural areas. Rural politicians have been accusing the O'Malley administration of waging a "war on rural Maryland."

"I"m of the school that thinks is is a way to protect our rural areas," replied Summers.

Otto also said he feared the rules would lead to the demise of farming in Maryland as developers buy up farmland and take it out of production as a way of offsetting the impacts of their building projects.

Del. Marvin Holmes, a Prince George's County Democrat, voiced a conflicting concern that developers might not get credit under the rules if they do convert farmland to housing and reduce pollution in the process.

Summers said regulators are seeking to strike the right balance in the rules to ensure that they don't choke off growth but don't create unintended incentives for further loss of farmland to development.

Holmes, recalling difficult negotiations among lawmakers earlier this year on the bill limiting septic-based development, said those were "a cakewalk compared to this."