The U.S. Environmental Protection Agency has granted Gov. Arnold Schwarzenegger and the California EPA more time to respond to the federal agency's proposal that it should oversee the cleanup of the Santa Susana Field Laboratory site south of Simi Valley.

The federal EPA sent a letter to Schwarzenegger on Dec. 6 detailing the findings of its latest study of the 2,850-acre former rocket engine testing site known as Rocketdyne and proposing that it should be designated as a Superfund site.

The EPA asked the state to respond within 30 days to the letter, which included the site's background and history of chemical contamination of soil and groundwater. EPA officials estimate there are 500,000 gallons of tichloroethylene, a toxic chemical, lying beneath the site.

BreAnda Northcutt, a spokeswoman for California EPA, said the state now has until Tuesday to notify the federal EPA whether it wishes the property to become a Superfund site.

California EPA Secretary Linda Adams met with representatives from environmental groups, local residents and local officials, including members of the staffs of Sen. Dianne Feinstein, D-Calif., and state Sen. Sheila Kuehl, D-Santa Monica, at the California EPA headquarters in Sacramento on Thursday. The five-hour meeting gave Adams the opportunity to hear firsthand about some of the issues and concerns of the local community, Northcutt said.

"We all want to make sure that we make the right decision," she said. "The EPA gave us more time after Secretary Adams told them it felt like we were being rushed into a response."

Dan Hirsch, co-founder of the nuclear watchdog group Committee to Bridge the Gap, who attended the meeting Thursday, said he is concerned that Adams has signed a letter of intent with Boeing Co., which owns the majority of the field lab site.

That letter of intent, which would form the basis for a formal agreement in the future, agrees to seek the repeal of Senate Bill 990 — state legislation signed into law last year that calls for strict cleanup guidelines for the site — in return for handing the property over to the state for use as parkland.

Northcutt said that although a letter of intent between Adams and Boeing has been agreed upon, Adams has not yet made up her mind on the issue of whether to accept the EPA proposal to oversee the cleanup.

"An unprecedented amount of work has taken place between Cal/EPA and Boeing to ensure the site is cleaned up to residential standards even though it won't be used for housing," said Northcutt. "The meeting on Thursday was about rebuilding a sense of trust, and the community had valid concerns regarding the letter of intent."

"Secretary Adams told the meeting that no requests for a change to SB 990 will go to the governor's desk until an agreement has been signed with Boeing," she said.

Northcutt added that if the site is turned over to the state as parkland, the EPA will be required to clean up the property only to the level of its use, which would be open space, and that, therefore, any formal agreement based on the letter of intent between California EPA and Boeing would ensure that a higher standard is met.

Hirsch said he and others who have campaigned for the site to be cleaned up are willing to consider rejecting Superfund designation if assurances are given by the state that the concerns and wishes of the community will be included in any ultimate decision about the future of the site.