The coal industry in Western Maryland won a victory over environmentalists today as members of a key Senate committee approved legislation to rescind the state's longstanding ban against mining on steep mountain slopes.

"Environmentalists go nuts whenever you talk about mining, but a lot of people have their roots in that industry," Sen. John N. Bambacus (R-Allegany) told fellow members of the Economic and Environmental Affairs Committee, who later approved his bill lifting the ban on an 8-to-3 vote.

Several senators said they changed their minds and voted for the measure after Bambacus presented several last-minute amendments that set forth five tests a mining company would have to pass before winning a permit to mine on steep slopes.

The coal industry in Allegany and Garrett counties has mounted an expensive lobbying effort to kill the 1975 ban against mining on slopes steeper than 20 degrees. And coal operators have an ally in Bambacus, who defeated the incumbent state senator from Maryland's two westernmost counties in 1982 after receiving large contributions from coal companies operating there.

Conservations have quarreled for years with coal operators, saying the ban has been a practical and symbolic check against some strip mining.

Lois Crossland, a civic activist from Lonaconing, Md., in the heart of one of the richest coal basins in Maryland, said she was "very disappointed" by the Senate committee vote. Crossland said she and others who live near strip mines will double their efforts to kill similar steep-slope legislation now pending in a House committee.

Crossland angrily criticized Bambacus, saying, "He cares nothing about the Allegany and Garrett citizens he represents."

"His credibility has been lost on George's Creek," the coal-producing valley where both she and Bambacus live, Crossland added.

Bambacus made an impassioned hour-long appeal today for the favorable vote, saying that an end to the steep-slope ban would bolster the coal industry in his district.

"This bill is extremely important to me," he said. "What legislator in his right mind is going to put in legislation that knowingly hurts people? Not me."

Bambacus' amendments gave the state Bureau of Mines the power to deny a steep-slope permit for a variety of reasons, including adverse impact on mine neighbors and the likelihood of severe water runoff, erosion or ground instability.

The amendments and last-minute appeals by Bambacus and Joseph A. Schwartz III, a lobbyist for the Maryland Coal Association, ensured the favorable vote committee vote, several members said.

Sen. Arthur Dorman (D-Prince George's) told a reporter yesterday that he intended to vote against the bill and predicted the legislation would "go down the tubes." Today, though, Dorman voted for the measure, saying the Bambacus amendments would go far toward safeguarding the environment.

Sen. Norman R. Stone Jr. (D-Baltimore County) also said he was persuaded by the amendments. "Ten years ago I would have voted no," Stone said. "Today I vote yes." But Sen. Sidney Kramer, who voted against the bill with fellow Montgomery Democrat S. Frank Shore, said that even the amended version "doesn't protect the environment in terms of the future."