A sprawling Warner Center parcel that formerly housed a manufacturer of rocket engines that launched astronauts into space has been long marketed as a potential high-rise urban district.

But decades of pollution left the soil and groundwater laced with cancer-causing toxins and chemicals.

Recently, property owner United Technologies Corp. has asked the state to change cleanup requirements of the property from residential to commercial standards, according to the documents filed with the Los Angeles Regional Water Quality Control Board, which oversees the remediation efforts.

In a letter submitted to state officials, the company said that the Regional Board has determined the property is “not suitable for unrestricted use and that a land-use restriction is necessary for the protection of present or future human health, safety or the environment as a result of the presence of hazardous materials.”

The chemicals detected at the site include cancer-causing trichloroethylene (TCE) and tetrachloroethylene (PCE) along with trichloroethane and tetrachloroethane, according to the Regional Board representatives. Based on the current condition, no residential use is allowed at the site, according to the documents.

“United Technologies has worked in close partnership with the Los Angeles Regional Water Quality Control Board (LARWCB) for many years to ensure the proper remediation of the Canoga Park property. Our priority has always been, and remains to be, to work with LARWCB to clean up the property so that it can be used for residential purposes, consistent with community goals. We are committed to ensuring that our efforts are in full compliance with all local, state and federal laws and regulations. We take seriously our environmental, health and safety responsibilities, and look forward to continuing to partner with all stakeholders on this matter.”

“The site meets the established cleanup goals for industrial/commercial land use,” said Renee Purdy, executive officer for Los Angeles Regional Water Board, in a statement.

Cleanup and monitoring of the groundwater will continue across the site and off-site even if state officials decide to approve a cleanup plan for soil, according to officials.

But Jane Williams, executive director at California Communities Against Toxics, said the cleanup plan proposed by United Technologies has lower standards and will leave contamination in groundwater.

“You’ve got these chemicals on the facility that are off-gassing into the air,” she said. “When you build a structure on top of that, they concentrate inside your structures.”

She added that the parcel was zoned for residential use and needs to be cleaned to the “appropriate” residential standards.

The 47-acre former Rocketdyne site was developed in the mid-1950s for the manufacture of rocket engines, metal molding and engine assembly.

Between 1956 and 1960, one of the buildings at the corner of Owensmouth Avenue and Vanowen Street was occupied by Atomics International and housed two small nuclear reactors, known as L-47 and L-77, used for the Systems Nuclear Auxiliary Power, or SNAP, program which developed nuclear power systems for NASA, according to the U.S. Department of Energy website.

Atomics International moved to another facility in the 1960s on De Soto Avenue in Canoga Park, and all radiological activities were transferred to the new site, the U.S. Department of Energy website said.

United Technologies Corp. acquired the property in 2005.

The company sold the business entity in 2013 to Aerojet but retained ownership of the facility. The site has remained idle since then.

Numerous environmental investigations have been conducted across the area since 1984 that have identified elevated levels of chemicals.

In recent years, the 47-acre parcel has been advertised as a potential high-rise urban neighborhood, according to real estate data firm CoStar, and is expected to cost about $150 million.

The area stretches across the street from sprawling Westfield Topanga mall and The Village and remains one of the city’s largest undeveloped sites.

Los Angeles City Councilman Bob Blumenfield, who represents the area, made a pitch in 2017 offering to bring Amazon’s second headquarters to the site.

Triple Five Group Ltd., the owner of the Mall of America, was eyeing the former Rocketdyne site.

The property sits within the Warner Center 2035 specific plan, which will determine development in Warner Center in the next 15 years, attracting construction of new offices, shops, hotels and thousands of new residential units.

But Williams, of California Communities Against Toxics, said the site’s groundwater along with soil need to be fully remediated before an influx of new residents begins arriving.

“The cleanup plan that is being approved by the state is leaving a huge amount of contamination in place,” she said.

Meanwhile, state officials say they are currently reviewing the data submitted by United Technologies. Once their analysis is completed, the board will issue a letter that would determine the future use of the site based on the current condition.

The letter is expected to be available for public review early this year.

The article has been updated to reflect a list of chemicals found on the Rocketdyne site.