Colorado officials said Tuesday they have found no evidence of contamination from oil or natural gas spills in water samples taken from rivers and streams affected by last month’s flooding.

The Colorado Oil and Gas Conservation Commission (COGCC) said its inspectors have visited about 80% of the area impacted by the floods and were keeping track of a combined 30 locations where oil and produced water from hydraulic fracturing (fracking) operations had leaked into floodwaters. The impacted area comprises a portion of the Niobrara formation of the Denver-Julesburg (DJ) Basin (see Daily GPI, Sept. 20; Sept. 19).

In late September, inspectors with the Colorado Department of Public Health and Environment (CDPHE) collected water samples from 29 testing sites from eight rivers affected by the flood. The samples showed high levels of E. coli in some areas of the South Platte Basin.

“Although much attention was focused on spills from oil and gas operations, it is reassuring the sampling shows no evidence of oil and gas pollutants,” said CDPHE Executive Director Larry Wolk. “There were elevated E. coli levels, as we expected, in some locations.”

Additional sampling to determine any changes in pollutant levels is planned. CDPHE also plans to collect water samples to test for metals, which could have been released from mining areas. An analysis of those samples was ongoing and would be released once completed.

“It is good news, but it’s also tempered with the fact that we now have, within the floodwaters, E. coli and 220 million gallons of raw untreated sewage,” said Colorado Oil & Gas Association spokesman Doug Flanders. “From our perspective, after a flood like this, all of us have a major issue that we have to address, which is the health problems that E. coli can present,” he told NGI‘s Shale Daily.

The COGCC is tracking 13 notable oil releases, down from an earlier report of 15, totaling 43,134 gallons, and 17 releases of produced water totaling 26,385 gallons.

“They’re still investigating two locations where they thought they had releases at the time, but they haven’t found anything yet,” Flanders said. COGCC officials concurred but warned there were “damaged facilities” at the two de-listed oil sites.

“For context, the volume of oil released is comparable to more than three, standard 300-barrel storage tanks,” the COGCC said. “The amount of produced water released is more than two of such tanks.” COGCC inspectors have so far visited 1,355 well sites in the affected area. The agency also released a map showing the flood impact zone, which was larger than its previous assessment area.

“This is not due to an increase in impacted locations but is an exercise designed to use an excess of caution in ensuring any location potentially affected receives an assessment and evaluation by COGCC personnel,” the agency said, adding that it would continue to refine and update its impact figures as it “learns more through new information from inspectors and operators.”

Flanders said he wasn’t able to comment on how the presence of E. coli might hinder or prevent oil and gas workers from returning to their wells.

“The flow of the water was strong, [but] the waters were able to recede fairly expeditiously; they receded a lot quicker than most floods,” Flanders said. “So from that standpoint, our guys have been able to get in. But there is still a lot of caution, for safety reasons, around many of these sites because of access, as well as any of the other issues that are caused by a flood such as this. Most of our guys are not working in standing water, but there are still all of the effects that you find in a flood area.”

Last week, Anadarko Petroleum Corp. estimated the flood will cause the company to lower its annual sales volumes for the year by 2.5 million boe (see Daily GPI, Oct. 7).