Maryland Gov. Martin O’Malley’s plan to curb sprawl cleared the Senate on Tuesday, although without key provisions that would have given the state power to override some local zoning decisions on new housing developments that rely on septic systems.

O’Malley (D) had said the state needed the authority to ensure it could reduce the waste that leaches from the developments and pollutes the Chesapeake Bay. But last week he weakened the proposal as it became clear that the bill faced an uncertain future.

With the override provisions struck from the bill, the Senate voted 32 to 14 along mostly party lines to require counties to draw mapped “tiers” of development before any major subdivisions served by septic systems could be approved.

The bill now moves to the House.

Last year, O’Malley sought to prohibit construction of subdivisions of five or more houses built with septic systems. But that legislation stalled.

The Senate vote backing this year’s bill came one day after another key O’Malley initiative emerged from negotiations with legislators in a scaled-back form. To secure enough votes to advance a proposal to subsidize development of offshore wind power, the administration agreed to lower the monthly subsidy that would be charged to residential ratepayers as well as large commercial and industrial users.

As with the wind bill, weakening the septic legislation was key to acceptance by lawmakers. An amendment to the measure, which Sen. Thomas M. Middleton (D-Charles) introduced last week with O’Malley’s support, killed provisions that would have given the state authority to deny permits if it decided counties were not abiding by master plan guidelines.

Sen. Brian E. Frosh (Montgomery), one of 14 liberal Democrats who unsuccessfully opposed the change but voted to pass the bill nonetheless, characterized it as a “baby step forward.”

“We’re not doing nearly what we need to do on smart growth,” Frosh said. “You see these developments starting to sprout up all over the place, unconnected to lines of transportation, unconnected to sewer systems.”

Frosh said the amended bill would not prevent counties from defining tiers in a way that would allow major subdivisions to be built on farmland and forestland. “There’s no enforcement mechanism except for lawsuits, and that’s an expensive and unresponsive way of regulating land use.”

Sen. Roger Manno (D-Montgomery), who also voted against the change, was more satisfied with the bill than Frosh. “I’m confident at this point that this bill will protect the bay and help to preserve the environment for our kids,” he said.

All Republicans in the chamber, after voting last week to adopt the Middleton amendment, voted against the bill. “What they’ve done is close the box in around [counties] with setting the tier requirements,” Sen. E.J. Pipkin (R-Queen Anne’s) said. “So there still continues to be a little bit of flexibility at the local level, but it’s significantly less than it is today.”

Sen. Barry Glassman (R-Harford) said the bill amounts to a “state-forced downzone” on farmers’ properties. “We want to save the land, but we don’t want to save the farmer.”

Middleton, chairman of the powerful finance committee and a farmer himself, said his support for the bill was contingent on the changes the O’Malley administration agreed on.

“I’d be very hesitant to vote for any bill that goes any further than this,” he said, referring to the possibility that the bill could change again in negotiations with the House of Delegates.