9624 ‎(2)‎

• UCREFRP Catalog Number: 9624
• Author: Bauch, N. J. and J. B. Bails.
• Title: Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado 1998-2001.
• USFW Year: 2004.
• USFW - Doc Type: \
• Copyright Material: NO

16 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998-2001
the mineral apatite (Hem, 1992). Although little information is
available on the mineralogy of the Troublesome Formation,
significantly higher concentrations of orthophosphate in water
samples from the Troublesome Formation aquifer could indi-
cate that apatite is the major source of orthophosphate in the
study area.
Naturally occurring dissolved organic carbon in ground
water is the result of biological and biochemical decay and
degradation processes in soil and, as such, usually is assumed to
be similar to the organic material present in soils in the ground-
water recharge area (Hem, 1992). Anthropogenic sources of
dissolved organic carbon include organic amendments to soil,
such as animal manure, and leachate from landfills or septic-
disposal systems. The naturally occurring and anthropogeni-
cally derived organic solutes that constitute dissolved organic
carbon can function as nutrients for microbiota, affect metal
solubility, participate in oxidation/reduction reactions, and
affect physical and chemical properties of solid/liquid or liquid/
gas interfaces. Certain organic solutes are toxic to aquatic and
other life forms and can cause water to be unusable for human
activities (Hem, 1992).
Dissolved organic carbon concentrations in ground-water
samples from the wells in the Fraser River watershed ranged
from 0.2 to 4.0 mg/L, and the median concentration was
0.91 mg/L (table 2). The highest concentrations, 3.0 mg/L and
greater, were detected in all four water samples from site 1, the
very shallow (18 ft) alluvial aquifer well located between
Winter Park and Fraser. Samples from site 6, east-southeast of
Tabernash, and from sites 7, 8, and 9, near Tabernash, had
median dissolved organic carbon concentrations exceeding
1.0 mg/L. All four wells also were alluvial aquifer wells.
Dissolved organic carbon concentrations were higher in
water samples from wells completed in the alluvial aquifer and
in non-ISDS areas than those from wells completed in the Trou-
blesome Formation aquifer and in ISDS areas (table 3). There
was, however, some overlap between dissolved organic carbon
concentrations in samples from ISDS and non-ISDS areas
(fig. 6). The concentration differences between these two areas
likely have no environmental significance. High concentrations
of dissolved organic carbon in ground water likely are the result
of the decay of organic compounds associated with natural
vegetation in the area. Concentrations in water samples from
site 1, which is in a pasture, also could reflect the effects of
animal waste.
Bacteria, Methylene Blue Active Substances, and
Radon-222
Total coliform bacteria are used as indicator bacteria to
assess the sanitary quality of water and the potential public
health risk from waterborne diseases. They typically do not
cause disease themselves but are correlated to the presence of
several waterborne organisms or pathogens that do cause dis-
ease (Myers and Sylvester, 1997). Coliform bacteria can be
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NUMBER OF SAMPLES
(31) (39)
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PRESENT ABSENT
EXPLANATION
X Outlier
90th percentile
75th percentile
50th percentile (median)
Lim 25th percentile
10th percentile
Figure 6. Distribution of dissolved organic carbon concentra-
tions by presence or absence of individual septic disposal
systems for wells in the Fraser River watershed, 1998-2001.
present in soil naturally or may occur as a result of animal or
human waste.
For the 11 wells, total coliform bacteria were detected in
one or two water samples from each of six wells (sites 1, 3, 4,
6, 7, and 8). Overall, the bacteria were detected in 9 of 68
ground-water samples, or 13 percent. All but two samples (both
for site 1) had bacteria concentrations less than or equal to
4 col/100 mL (colonies per 100 milliliters). Soil was the most
likely source for the low concentrations of total coliform bacte-
ria in water samples from sites 3, 4, 6, 7, and 8, and animal
waste was the likely source of the bacteria in samples from
site 1. Of these six wells, all were completed in the alluvial
aquifer, except for site 3, which was completed in the Trouble-
some Formation aquifer. All nine samples with detections of
total coliform bacteria also were analyzed for E. coh, an
indication of fecal contamination; E. coli were not detected.
Because each well was sampled only once in each month
that sampling occurred, insufficient data were available to com-
pare the total coliform counts for each well to the USEPA
MCLG, which specifies no more than 5 percent of the samples
in a month test positive for total coliform (table 2). Except for
site 1, total coliform bacteria were not a ground-water-quality
issue.
MBAS are natural or synthetic anionic surfactants; the
synthetic surfactants are present in many types of soaps and
detergents (Burkhardt and others, 1995). Detection of MBAS in
water samples can be an indicator of contamination by waste-
water. Most (57 of 69) water samples from the 11 wells did not
contain detectable concentrations of MBAS, including all sam-
ples from the 4 wells completed in the Troublesome Formation
aquifer. All detected concentrations except one were in water
samples from alluvial aquifer wells. MBAS concentrations
ranged from less than 0.02 to 3.82 mg/L (table 2), and all but the
maximum concentration were less than or equal to 0.10 mg/L.
The maximum concentration, detected in a sample from site 8
in an ISDS area, was the only concentration higher than the