The discovery of suspicious debris in a streambed in a park abutting the Santa Susana Field Laboratory by a trio of community activists has led the state's toxics department to order the lab's owners to clean it up.

The cleanup and removal of 8,500 cubic yards of debris contaminated with asbestos, antimony and cancer-causing polyaromatic hydrocarbons, or PAHs, could start as early as Friday, said Norman Riley, the Department of Toxic Substances Control's project director for cleanup at the laboratory in the hills south of Simi Valley.

On Nov. 1, DTSC issued an order to Boeing and NASA, which owns about 450 acres of the Field Lab, to take action on debris and contamination on Sage Ranch.

Christina Walsh, John Luker and William Preston Bowling were researching drainage from the former rocket engine and nuclear test site in Sage Ranch earlier this year when they discovered a glassy, lightweight, foamlike material in a creek bed, Walsh said.

"What we found was basically layer upon layer of this stuff," said Walsh, who runs the Web site cleanuprocketdyne.org.

Walsh and her colleagues, who found another debris field at the park, contacted Riley toured the site with staff members.

"We asked Boeing to take immediate steps," Riley said, adding later, "It's important for the public to know we take their concerns very seriously and we take our responsibility to protect public health very seriously."

A fence has gone up around one of the two locations identified for cleanup.

One area is next to a former liquid oxygen plant, which Riley said appeared to be a dumping area. It was in an area southeast of the plant where foam insulation material, deposits of white powdery material and construction debris was discovered in a creek bed, known as the Northern Drainage. Other contaminants in that area, which is about 500 cubic yards, include silica and antimony.

A second debris field is tied to the former 3.5-acre Rocketdyne-Atomics International Rifle and Pistol Club Shooting Range, which was in operation from 1972 to 1991.

The Topanga fire burned through the shooting range area, which left the debris more brittle and thus more "capable to releasing its toxic constituents," Riley said.

On Wednesday, a Boeing spokeswoman said the company has worked cooperatively and voluntarily with those overseeing the cleanup.

The company has "worked quickly to develop work plans to address the area and Boeing plans to fully comply with agency orders and begin the cleanup as soon as possible," spokeswoman Blythe Jameson said.

Luker, a Box Canyon resident who joined the growing ranks of community activists focused on the Field Laboratory a year and a half ago, said having the toxics agency take their concerns seriously was reassuring.

"It is extremely gratifying," he said.