McGarrigle said the companies would keep "safety crews and firefighting apparatus" at both sites.
"There are potential fire and hazardous-material risks that we need to be prepared for," said Ed Doyle, co-chairman of the county's emergency-planning committee.
Officials did not identify specific risks, nor would they disclose emergency plans, citing security issues.
Doyle said both companies had agreed that local officials "can go in anytime and look at anything."
State Rep. Steve Barrar (R., Chester/Delaware), among the local and county officials who met with the companies, said he became involved after a laid-off refinery firefighter called him to express safety concerns.
Barrar, chairman of the House Emergency Services Committee, said the companies presented "very thorough plans" of how they would respond to a crisis.
Sunoco, which is getting out of the refining business, has set aside $250 million to pay for environmental remediation at its properties.
Sunoco top executive Lynn L. Elsenhans, who plans to step down March 1, said she did not expect the Marcus Hook plant to operate as a refinery again.
Safety is a major concern around the refineries because "we have people living across the street," said Ed Truitt, the county's director of emergency services.
"We just want to make sure we're keeping an eye on them like a hawk over the shoulder," Truitt said.
"We let them know we're serious about this."
Contact staff writer Anthony R. Wood at 610-761-8423 or twood@phillynews.com.
