Construction on the Overlake Center retail site was interrupted earlier this month when workers uncovered old tires and a metal drum filled with unidentified chemicals buried on the property.

City and state Department of Ecology inspectors are investigating the site for any groundwater contamination because the debris was found near a well that serves the Overdale neighborhood.

Public Works Engineering Director Bob Brock said the city is still waiting on test results, but officials don’t believe the well was affected.

“It was fairly localized at that point, and didn’t really spread,” he said. “At this point, we don’t believe the contamination has caused any problems.”

The debris was found when a contractor laying a sewer line dug up the old tires and a mess of other trash on March 2.

The debris was accompanied by a faint petroleum odor, according to an Ecology report, so the compromised soil was removed from the site.

On March 11, a metal drum was discovered when a worker digging a trench punctured the side of the barrel with a piece of construction equipment.

An unknown substance leaked out of the drum and turned the water in the trench white, Brock said.

The drum and effected soil were removed for testing.

“The stuff they found is stuff that’s not normally buried; you can’t just dig a hole and fill it with tires, you have to dispose of them properly,” Brock said. “But what was really problematic was the drum, because it was just a mixed bag of chemicals.”

Initial tests near the drum revealed high levels of solvents and other hazardous chemicals, according to city officials. All the debris and contaminated soil has been removed.

Construction is continuing in other areas of the Overlake Center, a seven-building development which will include tenants such as Overlake Medical Center Issaquah, Bartell Drugs, and 24 Hour Fitness. Construction began last October.

Brock warned that cleanup of the debris may slow development of some of the businesses. Neither the property owner, Dale Frank Jr., or the developer, OB Frank Properties, could be reached for comment.

Puget Sound Energy previously owned the land, and registered it as a hazardous waste facility. Brock said it was largely used for storage of poles and other equipment.

The state Toxics Cleanup Program now has 90 days to conduct an investigation. The ecology department could place the land on a list of hazardous sites or a list of confirmed and suspected contaminated sites.