A long-vacant Iwilei property contaminated with benzene near Costco and Home Depot has been bought by a Pennsylvania company that plans to clean and redevelop the site.

West Chester, Pa.-based environmental cleanup firm Weston Solutions Inc. said it recently bought the 4-acre property with the intent to clean the site and position it for development that could include retail or industrial use.

Weston did not disclose a purchase price or the seller.

According to property records, the previous owner was BHP Hawaii Inc., a subsidiary of Australia-based BHP Billiton Ltd., a mining and oil company. The assessed value of the site for city property tax purposes is $9.5 million.

The site for decades had been used by onetime BHP affiliate The Gas Co., or Gasco, to manufacture synthetic natural gas. According to a 2006 state Department of Health report, Gasco processed heavy petroleum hydrocarbons to produce gas, which over decades contaminated soil and groundwater with benzene and other petroleum products.

Prior cleanup efforts removed 30 tons of gasses, but soil and groundwater contaminant levels remain high, the Health Department report said.

Peter Ceribelli, a Weston senior vice president, said it would likely take at least a few million dollars and one to two years to clean the site.

"This is nothing we haven't seen before," he said. "We're delighted to have the site now and look forward to returning the site back to productive use."

The area around the old Gasco site over the past decade or so has increasingly shifted from industrial use to retail with the development of the Regal Theatres-anchored Dole Cannery complex, Costco, Home Depot and Best Buy. Later this year, Lowe's plans to open a home-improvement store on a nearby parcel previously owned by ConocoPhillips.

Retail reuse isn't uncommon on contaminated sites after they are cleaned. Home Depot was built on a site with similar contamination issues, and a commercial fishing village was developed by the state on nearby land at Pier 38 that had long been plagued by methane emissions related to petroleum contamination.

Weston, established in 1957, has operated a Hawai'i office for about 15 years and primarily does cleanup work for the Department of Defense as well as other clients. The employee-owned firm said purchasing, cleaning and redeveloping property is a growing part of its business and that the Iwilei site was a prime opportunity.

Reach Andrew Gomes at agomes@honoluluadvertiser.com.