David Zwick, who was instrumental in writing and securing passage of the Clean Water Act of 1972, and who founded the advocacy group Clean Water Action, died on Feb. 5 in Minneapolis. He was 75.

He had had various health problems, including several heart attacks late last year, the environmental group Friends of the Earth, on whose board he served, said in announcing his death.

Mr. Zwick was a second-year law student at Harvard when Ralph Nader, an alumnus, came to the campus in the late 1960s recruiting “Nader’s raiders” to work on his citizen-advocacy projects. Mr. Zwick expressed interest, but Mr. Nader thought he was too immersed in school to be an immediate candidate.

“I said, ‘Let us know when you’re out and you want to work,’ ” Mr. Nader recalled in a telephone interview. “And he said, ‘No, I want to come now.’ So I knew this was a very committed person.”