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City of Boulder/USGS Water Quality Monitoring
Interpretation of Boulder Creek Watershed Fecal Coliform Data
by Sheila Murphy


Fecal coliform concentrations were analyzed in the period 1998-2000 at source water sites (e.g, Middle Boulder Creek above the Barker weir (MBCaW) and North Boulder Creek at Lakewood Reservoir (NBC-Lw)).Fecal coliform concentrations in Boulder Creek from Boulder Canyon downstream to Coal Creek have been analyzed since June 2000. Comparing the two sets of data is difficult because they are analyzed with different methods, and have different detection limits. It is also difficult to identify trends in the Boulder Creek profile without several years of data.

NBC-Lw in 2000

Samples from source water sites such as MBCaW and NBC-Lw were typically very low, less than 10 coliforms per 100 mL. Samples from Boulder Creek in Boulder Canyon were also generally low, less than the detection limit of 20 coliforms per 100 mL, with occasional spikes in concentration.

June 2000 FColi For the North Boulder Creek-Boulder Creek profile, samples from the year 2000 do not show an obvious pattern in fecal coliform concentrations. July 2000 FColi The concentrations of fecal coliform in samples from Boulder Creek at Eben G. Fine Park to the confluence of Coal Creek and Boulder Creek vary significantly, both from site to site and seasonally. This suggests that sources of fecal coliform are localized; the amount at each site depends on what has recently occurred upstream of that site (e.g., animal waste entering the stream). The fecal coliform count can largely be dependent on recent precipitation; rain water can carry sources of fecal coliform from streets, gutters, and lawns to Boulder Creek.

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The U.S. Environmental Protection Agency (EPA) and the Colorado Department of Public Health and Environment Water Quality Control Division (CDPHE-WQCD) have stringent regulations regarding fecal coliform presence in drinking water. For more information on these regulations, see the EPA and CDPHE-WQCD websites. These regulations are not discussed here because the Boulder Creek samples are not treated drinking water.

For domestic water supply, CDPHE-WQCD regulations state that fecal coliform count shall not exceed 2000 fecal coliforms per 100 mL (based on geometric mean of representative samples) at the point of intake (the location where water enters standard treatment for drinking water) (see Reg. 31, Basic Standards and Methodologies for Surface Water). The samples collected for source water are not at the point of intake; but for comparison, all samples from source water sites were well below 2000 coliforms per 100 mL.

CDPHE-WQCD regulations state that waters used for Class 1 primary contact (including such activities as swimming, rafting, and kayaking) should not have fecal coliform counts above 200 fecal coliforms per 100 ml. At Eben G. Fine Park, this standard was exceeded during the sampling events in August and September 2000. At Boulder Creek at 61st Street, this standard was exceeded in July, September, and November 2000. Downstream of 61st Street, each sampling site on Boulder Creek exceeded this standard at least once in the year 2000.

Waters used for Class 2 secondary contact (non-primary contact waters, including, but not limited to, fishing and other streamside or lakeside recreation) should not have fecal coliform counts above 2000 fecal coliforms per 100 ml. One sample from Boulder Creek (Boulder Creek at Highway 287 (BC-107)) in the year 2000 had a fecal coliform count greater than 2000 fecal coliforms per 100 ml.

Select here for general information about Fecal Coliform.

Select here for interpretation of other water
quality data in the Boulder Creek Watershed

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Last Page Update - Friday January 25, 2008