As promised, county supervisors Tuesday will vote whether to send a letter to PG&E asking it to suspend the relicensing of Diablo Canyon nuclear power plant until seismic studies have been completed and verified.

The letter was put on the agenda by Supervisor Adam Hill, whose district includes the power plant. Approval of the letter is considered all but certain given that a majority of the board has already expressed support for it.

Addressed to PG&E President Chris Johns, the letter says that staying license renewal would be a good way for the utility to restore the trust of the community. The letter cites an interview Johns gave The Tribune shortly after the earthquake and nuclear disaster in Japan in which he admitted that the company needs to “earn its customers’ trust.”

“We can think of no better way to do so in our county than to agree to our request,” summarizes the letter. “In doing so, PG&E would help to allay many concerns, rebuild customer confidence and show that indeed safety is of the utmost importance.”

PG&E and the federal Nuclear Regulatory Commission have insisted that license renewal and the seismic studies can proceed concurrently. If approved, license renewal would extend the operating lives of the plant’s two reactors to 2044 and 2045.

PG&E will hold an open house from 4 to 7 p.m., Wednesday at the South County Regional Center in Arroyo Grande to answer the public’s questions about seismic safety and other issues at Diablo Canyon.