From The Denver Post:
Samples collected in 29 locations in eight rivers in the flood zone show high levels of E. coli in the Boulder Creek and Big Thompson River watershed, the state health department said Tuesday. The testing also showed high levels of E. coli in locations in the South Platte Basin all the way to the Nebraska line The samples were collected on Sept. 26, more than two weeks after flooding began. The areas will be resampled in the next few weeks.
Although the state is tracking multiple spills — about 40,000 gallons of oil — from well and storage facilities in the South Platte Basin, the testing showed no evidence of contamination.
“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,” Colorado Department of Public Health and Environment chief medical officer Dr. Larry Wolk said. “There were elevated E. coli levels, as we expected, in some locations.”
The highest levels of E. coli were detected in Boulder and near Niwot, where tests found the bacteria at a rate of 472-911 colonies per milliliter of water. Levels higher than about 126 parts per milliliter are considered unsafe, said Steve Gunderson, director of the state’s water quality control division.
Slightly lower levels of E. coli — 126 to 472 parts per milliliter — were detected along Boulder Creek northeast of Boulder, near Erie and near Boulder Creek’s confluence with the St. Vrain. Similarly high levels were detected near the confluence of the St. Vrain and South Platte north of Platteville, east of Milliken near the confluence of the South Platte and Big Thompson, and long the South Platte west of Kersey and near Orchard, Brush, Sterling and Julesberg.
Levels of 126 to 472 parts per milliliter also were found on the Big Thompson in two spots between Estes Park and Loveland.
State health department engineers estimate about 20 million gallons of raw sewage poured into floodwaters untreated, as well as 150 million to 270 million gallons of partially treated sewage, Gunderson said.
“It’s a wild guess,” Gunderson said. “But there were sewer systems that were out of commission for a while. Some were flooded. Some had sewer lines that were ripped out. It was pretty catastrophic.”
For example, a broken city of Boulder main allowed raw sewage to flow directly into Boulder Creek in the days after flooding began Sept. 11.
The water quality division also looked at feed lots and dairies in the flood zone. “Remarkably, those fared pretty well,” Gunderson said.
The state will test again in the next few weeks, and then return in the spring to begin assessing the impact of the flood and related contamination on aquatic life, Gunderson said.
“Not so much how fish are faring, but we’ll be looking for the bugs they feed on,” Gunderson said. “They are an indicator of aquatic life health and they are sensitive to problems in the stream — water quality, sediment smothering the rocks on the bottom where they live.”
The health department also sampled for metals that may have been released from mining areas in the mountains, but the analysis is not complete.
According to the health department, the E. coli can make people sick. However, outbreaks of communicable diseases or illnesses after floods seldom are seen and have not been reported with the recent flooding in Colorado.
Five public drinking water systems remain on boil or bottled water advisories: Jamestown, Lyons, Mountain Meadow Water Supply, Lower Narrows Campground and Sylvan Dale Ranch.