A black substance continues to flow into waterways from Suncor Energy’s oil refinery north of Denver, and tests show benzene levels are now at 48 times the limit for drinking water, even downstream of the point at which Sand Creek flows into the South Platte River.
As a result, federal labor officials launched an investigation of possible worker exposures at the refinery, where tap water also has issues.
State regulators said they continue to work with Suncor to find a way to block the toxic material from flowing into the bed of Sand Creek.
Colorado Department of Public Health and Environment data — from samples taken by Suncor — showed benzene concentrations at 720 parts per billion on Jan. 9 at the point where Sand Creek meets the South Platte, up from 190 on Jan. 6, and 144 times higher than the 5 ppb national drinking-water standard. Benzene is a chemical found in crude oil classified as cancer-causing, especially affecting blood.
Downriver on the South Platte, data show benzene at 240 ppb on Jan. 9, a decrease from 590 on Jan. 6 but still 48 times higher than the standard.
The South Platte River is the main water source for northeastern Colorado and the Denver area.
Spilled contaminants from decades of refinery operations at the site have seeped underground, “and it is snaking through. The pressures change. It finds the path of least resistance, and that’s apparently what has happened. It has found the path of least resistance to get into Sand Creek,” said Colorado health department environmental-programs director Martha Rudolph.
State regulators favor construction of underground clay walls at the creek and the refinery to try to block toxic material before it spreads; vapor-extraction systems to remove it from soil; and pumping of contaminated groundwater — all aimed at preventing further pollution.
They characterized the spill as one where hydrocarbons dissolved in groundwater enter through the bottom of Sand Creek, which carries them into the river. Officials are installing aerators on Sand Creek to try to release toxic vapors trapped in water into the air.
For utilities such as Aurora Water, which serves 335,000 people, the situation shows the importance of state-of-the-art water-treatment systems that can remove benzene before water reaches residents’ homes. Aurora Water currently is not drawing from its Prairie Waters intake system, 13 miles downriver, and will assess the upstream seepage before doing so, spokesman Greg Baker said.
Shortly after discovering the spill Nov. 28, benzene in Sand Creek reached 120,000 ppb, according to state data released.
Under Suncor’s property, a monitoring well detected benzene in groundwater at 74,000 ppb, with ethyl benzene at 7,300 ppb (standard is 700), toluene at 110,000 ppb (standard: 1,000), and xylenes at 38,000 ppb (standard: 1,400).
Meanwhile, the U.S. Department of Labor’s Occupational Safety and Health Administration is investigating the air and water on Suncor property in response to a complaint that workers may have suffered exposure.