Editor's note: This article has been changed to correct information about Xcel Energy's contribution to the project and the buildings on the former coal gasification site.

Later this month, Boulder will undertake a $210,000 study of the extent of contamination underneath the 13th Street Plaza at the site of a former coal gasification plant.

The site at 13th Street and Canyon Boulevard today houses the Dushanbe Teahouse and a city-owned parking lot. From 1902 to 1952, it was the site of the Federal Gas Company's coal gasification plant.

Six monitoring wells installed in September 2010 indicated the presence of benzene and naphthalene, a suspected carcinogen. But the wells did not provide enough information to identify the source of the materials or fully describe what might be underground.

Officials do not know if the substances have migrated off-site, but they said they're unlikely to threaten the city's drinking water.

"What we do know is these compounds are very heavy and not very water-soluble," Boulder spokeswoman Jody Jacobson said.

That means that if they are moving, they are probably moving slowly, officials said. And that's one of the questions the new round of investigation is designed to answer.

The parking lot east of the teahouse will be closed for one to two weeks after Thanksgiving so that an environmental consultant can put in two more monitoring wells and collect more information from the six existing wells, according to a memo to the City Council about the issue.

That consultant also will attempt to find out what structures or equipment might have been left underground when the surface structures were removed.

Air quality testing last year at the Teahouse and the Atrium building nearby showed levels of benzene and naphthalene well below EPA thresholds, the city said, and officials do not believe the site represents any threat to anyone who uses any of the buildings there.

Xcel Energy, which previously owned the site, will contribute up to $50,000 toward the total cost, the memo said. The city can seek additional money from Xcel for future clean-up costs if necessary.

If the consultant finds that remediation is necessary, Jacobson said the city is likely to submit a voluntary clean-up plan to the Colorado Department of Public Health and Environment.

Benzene and naphthalene are common byproducts of coal gasification, a process that produced fuel for heaters and lanterns. Benzene can cause bone marrow to stop producing red blood cells, leading to anemia. It also can damage the immune system or cause cancer.

Naphthalene, which is used in the production of mothballs and has other industrial uses, can lead to anemia, damage to the liver and can cause neurological damage in infants.
