BENICIA -- Valero's plan to import crude oil by rail heads to the Planning Commission on Thursday night, two days after a packed community meeting hosted by project opponents.

If approved, the project would position Valero to be the first of the five Bay Area refineries to tap into large amounts of discounted, land-locked North American crude, possibly including controversial Canadian tar sands oil.

Crude-by-rail opponents argue that the project's environmental document inadequately addresses potential health impacts of processing dirtier oil, including increased air pollution, and risks of rail spills and deadly accidents such as the one that killed at least 15 people in Quebec on Saturday morning.

Though the commission is scheduled to start the project hearing tonight, no decision is expected until August; commissioners want more time to consider public comments. The next scheduled Planning Commission meeting is Aug. 8; however, Valero is requesting a special meeting Aug. 1 to decide the matter.

The city's preliminary environmental review of the project, which would allow Valero to receive as much as 70,000 barrels a day of crude by rail at its Benicia refinery, found no significant impact.

However, the NRDC and the Good Neighbor Steering Committee, a refinery watchdog group that hosted a community meeting on the project on Tuesday, are pushing for a full environmental report.

About 60 people attended the forum at the Benicia Community Center. They heard NRDC representatives outline the group's concerns about increased air emissions tied to refining dirtier crudes and potential rail spills. The tanker cars would travel along Union Pacific tracks through Sacramento, Davis, Dixon, Fairfield and Suisun City, as well as the environmentally sensitive Suisun Marsh.

NRDC representatives argued refining tar sands oil blended with chemicals would increase emissions of benzene and lead and other hazardous air pollutants, including smelly sulfur compounds. The group further contends dirtier crudes speed up corrosion of equipment, possibly leading to explosions like the one at Chevron's Richmond refinery last August.

Valero officials declined invitations to speak at Tuesday's meeting, but are expected to be present tonight.

The commission meets at 7 p.m. today at City Hall, 250 E. L St.