From board chairmen and from stockholders in tiny towns, the letters are flowing in, part of a well-orchestrated chemical industry effort to thwart congressional approval of a hazardout-chemical cleanup fund.

Sen. John C. Culver (D-Iowa) gets handwritten mail from home-state chemical company employes. Sen. Robert P. Stafford (R-Vt.) is hearing from corporate shareholders.

House members such as Reps. Mario Biaggi (D-N.Y.) and Albert Gore Jr. (D-Tenn.) are on the personalized mailing lists, receiving pleas for reason and sensibility toward "superfund" legislation that could cost industry many millions of dollars.

The superfund fight now is caught in the bind of a fast-expiring congressional calendar and a sophisticated industry effort aimed at weakening pending bills.

Well-placed election campaign contributions plus personalized letter-writing and telephone are having an effect.

"I've worked on this legislation for more than two years and this is by far the smoothest lobbying I've seen," said a congressional aide. "These chemical guys are the best in town -- no juggernaut like petroleum, just well-targeted, subtle pinpricks."

Although they differ in details, superfund bills in the House and Senate would set up a large fund, with industry paying most of the cost, to clean up chemical dumps that threaten public health.

Spurred by the Love Canal disaster in New York and by Environmental Protection Agency estimates that several thousand such dumps pose a peril, Congress is under heavy pressure.

An array of forces, ranging from the White House and governors, states and cities to environmentalists, health, farm and labor groups, is supporting a strong superfund bill. But the pressure of October adjournment and intensive industry lobbying are raising doubts that Congress will produce strong legislation.

This is the situation:

The House during the week of Sept. 8 is expected to take up two bills dealing with hazardous chemicals, one on oil spills and the other on waste dumps.

The dump bill sets up a $1.2 billion fund, with the chemical industry responsible for financing 75 pecent, the government the rest. Rep. James J. Florio (D-N.J.) is working on amendments more acceptable to industry, scalling down the fund.

A tougher Senate bill, also holding industry liable for damages caused by hazardous chemicals, would require the companies to finance 88 percent of the cleanup fund.

That measure is scheduled for Senate Finance Committee hearings two weeks from now, which may throw a further crimp into the timetable. Chairman Russell B. Long (D-La.), however, has made public pledges not to stall the bill.

Although the clock would seem to favor opponents of the strong bills -- a House-Senate conference would still be required to work out differences -- the chemical lobby is leaving nothing to change.

The move against superfund is being led by the Chemical Manufacturers Association (CMA), which has more than 200 members, including some of the country's biggest and most influential companies.

CMA vice president Bill Stover said, "Business as a whole is concerned about this legislation, but the advocacy role has fallen to us. The list of foes includes the Business Roundtable, the U.S. Chamber of Commerce, the National Association of Manufacturers and many more.

"If a resonably livable bill is adopted, I'll be happy. But the Senate bill doesn't fit that by any definition," Stover said.

On their own, such CMA member companies as Monsanto are enlisting employes and shareholders to urge legisltors to enact a law that avoids "overkill" -- a word that crops up in most of the mail.

Monsanto computers match the names of stockholders with those of the legislators who represent them. The shareholders are then urged by mail to convey the corporate message of opposition.

"We have a corporate policy that urges employes and shareholders to participate as much as possible in the public policy process," said Monsanto lobbyist John Hussey.

"We have never defended the indefensible," he added, "but the lefilation deals with a number of separate issues. The abandoned waste site is the principal policy problem that needs to be solved through the cooperation of government and industry. We think the House bill, without the fund, gets at the real problem."

A study released this week by Ralph Nader's Congress Watch organization threw another light on the battle. It reported more than $2 million in election campaign contributions from the chemical industry to members of Congress in the last three years.

Congress Watch found a "significant" link between contributions and two key votes in the House Ways and Means Committee to increase the size of the cleanup fund.

The average chemical industry contribution to members who supported both amendments was $1,078. To those who took the industry's side and opposed both amendments, contributions averaged $4,765.

Leading House recipients of industry contributions were Reps. Steve Symms (R-Idaho), $28,487; Charles Grassley (R-Iowa), Culver's opponent for the Senate, $23,449; John E. Porter (R-Ill.), $21,990; James Abdnor (R-S.D), $18,250, and James Martin, (R-N.C.), $14,485.

Top Senate beneficiaries were Howard H. Baker (R-Tenn.), $27,193; Long, $25,200; David Durenberger (R-Minn.), $24,600; John Tower (R-Tex.), $23,944, and William Armstrong (R-Colo.), $23,333.

Baker, an opponent of the superfund bill, is a member of the Environment and Public Works Committee, but attended few, if any, of the hearings or markups on the measure. Another members who opposed the bill in committee, Alan K. Simpson, (R-wyo.), got more than $21,000 from industry donors.

Long, the second-leading Senate recipient, will play a key role in determining the fate of the bill when his Finance Committee reviews the funding provisions.

Nader described the contributions list as "a Who's Who of opponents to the superfund bill," although he noted that Sen. Charles Percy (R-Ill.) supported a strong measure despite receiving more than $23,000 from the industry.