03/01/2012 10:12 am ET Updated Mar 01, 2012

Suncor Refinery Spill: Crews Continue To Work To Cleanup Cancer-Causing Benzene By Deadline

Contaminated groundwater beneath Suncor Energy near downtown Denver is continuing to seep into the bottom of Sand Creek and cleanup crews have until Thursday to complete an underground wall to help hold back the cancer-causing benzene leak, The Associated Press reports. The toxic groundwater is seeping into Sand Creek near the confluence with the South Platte River.

Crews are building a 1,000-foot-long, 30-foot-deep underground wall designed to hold back the contaminated groundwater from seeping further into Sand Creek. Suncor energy has also expanded a hose system that is blowing air bubbles into Sand Creek to help expel the benzene. However, The Denver Post obtained Suncor's water sampling data that was provided to the Colorado Department of Public Health and Environment and upon analysis, benzene levels in the creek and river may be increasing. Read The Denver Post's analysis here.

It has been three months since the cleanup effort began and the toxic spill has continued to spread.

The South Platte River is a major source of drinking water for Aurora and Thornton, but the water to both regions is treated so contaminated drinking water is not expected. However, Suncor employees have had their blood tested for benzene that they might have been exposed to through the refinery's own in-house drinking water system, CBS4 reports.

The EPA, state of Colorado and Suncor Energy itself have been working since November to contain and cleanup the contamination. According to 7News, in late-December, benzene levels in Sand Creek reached 670 parts per billion -- 134 times the national drinking standard.