The Reagan administration has given several indications it will seek to reduce the use of one of the government's main and most familiar environmental enforcement devices: the environmental impact statement.

These advance assessments of likely environmental consequences are required by the 1969 National Environmental Policy Act (NEPA) for major federally financial projects of almost every kind. They have become an inportant means of disciplining federal action, and a sore point among federal agencies and developers, who regard them as more bothersome than useful.

Interior Secretary James G. Watt told the Senate Budget Committee last week that the impact statement process now is "so cumbersome that it gets in the way of decision-making." He said without offering specifics that it needs "streamlining."

The administration has also cut deeply into the budget of the Council on Environmental Quality, the small agency that was created by NEPA and has overseen the use of impact statements.

CEQ defenders say these budget cuts at bottom are aimed at the environmental impact process.

But the California businessmen expected to be nominated as CEQ chief, A. Alan Hill, denied this yesterday. He used Watt's word, saying the idea was only to streamline the process.

CEQ was cut from a proposed $4 million to $1.04 million in fiscal 1982, 72 percent, and all 32 of its fulltime employees were formally notified yesterday to find other jobs. "Unless the White House appoints some other entity to assure that the [environmental] review process is carried out, that action is an attack on the National Environmental Policy Act," said Louise Dunlap of the Environmental Policy Center.

A group of eight congressmen wrote to Reagan expressing "deep concern" about the staff firing, saying it raised "serious questions about CEQ's future ability to effectively carry out its mandated functions." It also "calls into question the commitment of your administration to enforce the nation's core environmental laws," said the letter, which was drafted by Rep. Toby Moffett (D-Conn.).

It was CEQ over the years that wrote the guidelines spelling out precisely when environmental impact statements had to be made, and what they had to contain. Under President Carter, CEQ reorganized its guidelines to make them uniform for all 70 federal agencies.

"This cut is a threat to NEPA because it's not clear how the council can carry out its obligations with a staff of this size," acting CEQ chief Malcolm Baldwin said.

The new budget would allow for 16 positions, including the three council members, instead of the previous 32 fulltime and 17 part-time slots. Six or seven people now do NEPA oversight work fulltime, Baldwin said. "I think they'll be lucky to have more than one person doing it now," he concluded.

Hill, 43, responded that each of the three council members "will be a full-time working member" and that one will be assigned fully to NEPA work with one staff person to assist. "We have a statutory function and will carry that function on," he said. The main reduction will be in preparation of CEQ's annual report to the president on environmental issues and in its special reports, he said. "Those won't be as comprehensive or detailed as in the past," he said.

Hill, a native of San Rafael, Calif., worked for the state legislature and the Republican Party there before becoming assistant to the secretary of natural resources under Ronald Reagan in 1969. He became deputy director of the state department of conservation in 1970, moving to the agriculture department in 1972 and leaving in 1974 to run unsuccessfully for Congress.

He then cofounded a small firm supplying washroom equipment wholesale to the construction industry, which grossed less than $300,000 last year, Hill said. He plans to sell the business upon formal nomination to head CEQ.