Dilution may keep water supply safe
De Beque town manager says benzene contamination poses no threat
Dilution should protect De Beque from benzene contamination in an upstream tributary of its water supply, the Colorado River, the town’s manager says.
“We don’t see any particularly large (red) flags right now,” Town Manager Guy Patterson said Thursday.
The river is the town’s sole source of potable water, and De Beque is about 10 miles downstream from Parachute Creek, the site of benzene contamination from what Williams says was a natural gas liquids leak from a pipeline leaving its gas processing plant.
Groundwater and soil contamination involving thousands of gallons of hydrocarbons was discovered last month, but benzene hadn’t been found in the creek until last week. However, the benzene levels remain below the state drinking water standard of 5 parts per billion in Parachute Creek. Also, no benzene has been detected where the town of Parachute diverts its irrigation water supply 2.7 miles downstream of the leak source area, or at the creek’s mouth at the Colorado River.
“Since we’re much further downstream it looks like we’re safe but we’re continuing to monitor the situation,” Patterson said.
Like others, De Beque was concerned about a lack of notification about the incident when it was first discovered. Officials first learned of it through media accounts. But Patterson said the town is now being kept up to date about surface water test results.
Williams said Thursday it has completed installing a water aerator in the creek to remove benzene and other volatile organic compounds. Installation of similar systems making use of what are called air sparging devices are either pending or nearly complete in both the creek and underground along the creek bank where a trench also is being built to try to keep benzene-tainted groundwater out of the creek.
Williams has installed another well for recovery of liquid hydrocarbons, and two more are planned. It has continued to drill monitoring wells to delineate the extent of contaminated groundwater.
The highest benzene measurement in the creek so far was 3.9 ppb, on Tuesday. The high reading Thursday was 3.2 ppb, with additional detections of 1.4 and 1.3 ppb at the next test locations downstream.
The state Water Quality Control Division doesn’t consider the creek a drinking water supply, and has set a maximum benzene standard in the creek of 5,300 ppb to protect aquatic life.
While the creek is used for irrigation and livestock graze near it and drink from it, the division hasn’t established agriculture-based standards for organic chemicals.
“However, in general, aquatic life and drinking water uses are much more sensitive than agriculture uses, meaning that standards established for those uses are much more stringent,” said division director Steve Gunderson, who also noted that benzene typically dissipates quickly in streams.