A congressional committee has voted to prohibit federal engineers from dumping millions of cubic yards of dredge material near Kent Island in the Chesapeake Bay unless they have exhausted all other possible sites.

The House Appropriations Committee said Tuesday that it was "deeply concerned" about the plan and directed the Army Corps of Engineers to consider four other sites for disposing of mud dredged from the approach channels of Baltimore Harbor.

Opponents of the Kent Island location, known as Site 104, hailed the vote as another "nail in the coffin" of a plan that they say would damage water quality and aquatic life.

The administration of Gov. Parris N. Glendening (D) reiterated its position that dumping at Site 104 is essential to maintain shipping access to Baltimore Harbor and would pose no threat to the bay.

"This is a huge victory for the Chesapeake Bay," said Rep. Wayne T. Gilchrest, a Republican from the Eastern Shore, who lobbied the House Republican leadership to include the restrictive language in the bill.

But Maryland Secretary of Transportation John D. Porcari said: "Congressman Gilchrest has taken an unusual and unnecessary step to stop a process that has been underway for two years. As legitimate environmental concerns are brought to the attention of the Corps, they will address them. His actions actually prevent that."

The issue has been building since February, when the engineer corps issued a 400-page draft environmental impact statement that was favorable to the proposal. Opponents turned out in large numbers at three public hearings, and a Kent Island group persuaded six county governments around the bay to pass resolutions opposing the dumping.

In the spring, Glendening and port officials prevailed on the leadership of the Maryland General Assembly not to consider bills opposing Site 104. The state also rallied business and labor support, saying that Baltimore Harbor would not be able to accommodate large tankers and cargo ships if it was not adopted.

Opponents were buoyed this month, when the U.S. Fish and Wildlife Service urged the engineer corps to withdraw the Site 104 proposal, saying open-water dumping in that area of the bay could trigger algae blooms and kill off ecologically important underwater grasses.

The House bill is expected to come up for a vote in the next two weeks. If approved, it would go to a House-Senate conference committee. Porcari said state officials will lobby Sens. Paul S. Sarbanes and Barbara A. Mikulski, both Maryland Democrats, to get the Site 104 prohibition stripped from the bill.