The Sierra Club board of directors called on Interior Secretary Donald P. Hodel to complete a study of dismantling the Hetch Hetchy Reservoir in Yosemite National Park before the end of the Reagan Administration. The reservoir is a main source of water for more than 2 million residents and businesses in the San Francisco Bay Area. The 15-member board unanimously passed the resolution that calls on Hodel to "demonstrate the seriousness" of his proposal two months ago that O'Shaughnessy Dam on the Tuolomne River be razed and the valley be restored. The then-fledgling Sierra Club was the main opponent of the damming during the early part of this century. Congress authorized the dam in 1913 and the project was completed in 1924. In its resolution, the club said Hodel could finance the study out of "discretionary funds." Hodel is scheduled to meet with San Francisco Mayor Dianne Feinstein, an opponent of any demolition, at Hetch Hetchy next month to discuss his suggestion.