Pushing aside the misgivings of the Ehrlich administration, legislative leaders said yesterday that they plan to make homeowners with septic systems pay the same surcharge to protect the Chesapeake Bay as those on public sewer systems.

Sen. Paula C. Hollinger and Del. Maggie L. McIntosh, who are chairwomen of the Senate and House committees handling Gov. Robert L. Ehrlich Jr.'s bill creating a fund to upgrade the state's sewer systems, said the legislation will be amended to ensure that septic system owners do not escape the fee.

The legislation, Ehrlich's top environmental initiative of the 2004 session, has won praise from the Democrats who control the General Assembly - even as they labeled it a "flush tax."

But they, along with environmentalists, want to take the governor's plan a step further and apply it to septic systems. They argue that septic tanks, which are common in rural and suburban areas - which are heavily Republican - also contribute nitrogen pollution to the bay and that their owners too should contribute to cleaning up the bay.

"We're just trying to spread it out and make everybody feel the responsibility of cleaning the bay up," said Hollinger, a Baltimore County Democrat.

Ehrlich's proposal would apply a flat $2.50-a-month surcharge on all residential water and sewer bills - with businesses paying on a sliding scale based on how much water they use - to create a Chesapeake Bay Watershed Restoration Fund. The fund would be used to finance $750 million to $1 billion in improvements to 66 sewage treatment plants.

At a hearing on the bill before the House Environmental Matters Committee yesterday, Ehrlich aide Bernie Marczyk said the administration would prefer to deal with septic systems separately after more study.

But McIntosh, the panel's chairwoman and a Baltimore Democrat, said it is important to deal with the issue of failing septic systems. Democrats' insistence, some said, is based in part on a suspicion that their constituents are being asked to foot a disproportionate share of bay cleanup costs.

Some Republican legislators are balking at the inclusion of septic systems, arguing that owners of such systems should not have to pay into a fund to clean up the pollution caused by inadequate sewage treatment plants. McIntosh, however, said the money raised could be used for other projects to clean up the bay.

Democratic leaders said they are confident Ehrlich will sign the bill with septic systems included.

The maneuvering over the septic systems came as the bill won the endorsement of two heroes of past battles to protect the Chesapeake Bay.

Former U.S. Sen. Charles McC. Mathias Jr. and former Gov. Harry R. Hughes made a joint appearance before the Environmental Matters Committee to praise Ehrlich's initiative.

The committee also heard from opponents of the bill, including some large manufacturing companies. Michael Powell, a lobbyist for the companies, said his clients could support the bill if they were exempted or their charges could be based on nonindustrial wastewater only.

But McIntosh said she would treat pleas for exemptions or lesser charges skeptically. "I'm going to hold fairly firm on carve-outs," she said.