Richard J. Herbst, a South Arlington civic activist, announced yesterday he will seek the Arlington Republican Party's endorsement of his candidacy for the Arlington County Board seat held by Ellen M. Bozman.

A former president of the Arlington Ridge Civic Association, Herbst said he was running because he wanted an opportunity to become more involved in community issues. "I have discovered over the past several years that I like community involvement . . . and I would like to concentrate on a countywide basis the way I have in South Arlington," he said.

A lawyer and engineer who works as a policy analyst for Commerce Secretary Malcolm Baldrige, Herbst is running as an independent because federal employes are prohibited from running as party candidates.

His candidacy will put him on the same ballot line this fall as Bozman, who is seeking her fourth four-year term as an independent endorsed by county Democrats and Arlingtonians for a Better County, a self-described nonpartisan political coalition.

Herbst said Bozman will be a "very formidable" opponent who will pose a "major challenge" to his first bid for elective office.

He said he believes he could give the five-member board a better political balance. Michael E. Brunner, who endorsed Herbst yesterday, is the only Republican on the board.

Herbst has been a member of the county's sports commission and chaired a study committee on solid waste disposal. In South Arlington, he has been active in efforts to block an elevated highway that would have replaced Rte. 1 and to shape development policies in the Crystal City and Pentagon City areas. He is expected to be endorsed at the Republican Party's May 11 canvass.