Water-Resources Investigations Report 03–4275

U.S. Department of the Interior

U.S. Geological Survey

Water-Quality Characteristics and GroundWater Quantity of the Fraser River Watershed,

Grand County, Colorado, 1998–2001

Prepared in cooperation with the

GRAND COUNTY BOARD OF COUNTY COMMISSIONERS
Front and back covers: Fraser River Valley 

Photographs by Jeffrey B. Bails, U.S. Geological Survey 
Water-Quality Characteristics and GroundWater Quantity of the Fraser River Watershed, 

Grand County, Colorado, 1998–2001

By Nancy J. Bauch and Jeffrey B. Bails

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

GRAND COUNTY BOARD OF COUNTY COMMISSIONERS

Water-Resources Investigations Report 03–4275
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.
Contents iii

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description of the Fraser River Watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Data Collection and Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Data Collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Laboratory Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Statistical Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Water-Quality Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Water Quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Ground Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Field Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Dissolved Solids, Major Ions, and Trace Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Nutrients and Dissolved Organic Carbon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Bacteria, Methylene Blue Active Substances, and Radon-222 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Changes Over Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Field Properties and Suspended Sediment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Dissolved Solids, Major Ions, and Trace Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Nutrients and Organic Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Fecal Coliform Bacteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Ground-Water Quantity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Appendix I—Selected Ground-Water-Quality Data for Wells in the Fraser River Watershed, 1998–2001 . . . . 33

Appendix II—Quality-Control Methods and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Figures

1–3. Maps showing:

1. Location of ground- and surface-water sample-collection sites in the Fraser River

watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

2. Land-use/land-cover classifications for the Fraser River watershed. . . . . . . . . . . . . . . . . . . . . . . .4

3. Generalized geology of the Fraser River watershed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

4. Piper diagram showing dissolved major-ion composition of ground- and surface-water 

samples collected in the Fraser River watershed, 1998–2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

5–6. Boxplots showing:

5. Distribution of dissolved nitrate concentrations by aquifer type for wells in the 

Fraser River watershed, 1998–2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6. Distribution of dissolved organic carbon concentrations by presence or absence 

of individual septic disposal systems for wells in the Fraser River watershed, 

1998–2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7. Map showing median radon-222 concentrations for wells in the Fraser River watershed, 

1998–99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
iv 

8–13. Graphs showing:

8. (A) Specific conductance and dissolved (B) calcium, (C) magnesium, (D) chloride, 

 and (E) sulfate concentrations over time for well 7 in the Fraser River watershed, 

 1998–2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

9. Dissolved sulfate and chloride concentrations and discharge at the Fraser River 

 below Crooked Creek at Tabernash, Colorado, 1998–2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

10. Dissolved ammonia and nitrate concentrations and discharge at the 

 Fraser River below Crooked Creek at Tabernash, Colorado, 1998–2001 . . . . . . . . . . . . . . . . . . 22

11. Phosphorus concentrations and discharge at the Fraser River below 

 Crooked Creek at Tabernash, Colorado, 1998–2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

12. Organic carbon concentrations and discharge at the Fraser River below 

 Crooked Creek at Tabernash, Colorado, 1998–2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

13. Fecal coliform bacteria concentrations and discharge at the Fraser River below 

 Crooked Creek at Tabernash, Colorado, 1998–2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

14. Map showing extent and depth of the alluvial aquifer in the upper Fraser River 

 watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

15. Graph showing ground-water level and temperature in the alluvial aquifer (site 9) in the

 upper Fraser River watershed, 1998–2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Tables

1. Description of 11 ground-water wells and one surface-water sampling site in the Fraser 

River watershed, August 1998–September 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

2. Statistical summary of selected ground-water data for the Fraser River watershed, 

1998–2001, with U.S. Environmental Protection Agency and State of Colorado 

water-quality standards and U.S. Geological Survey National Water Quality 

Laboratory reporting levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3. Results of two-tailed Wilcoxon rank-sum tests for comparison of selected field properties 

and water-quality constituents in wells by aquifer type, land use, and individual septic 

disposal system (ISDS) or non-ISDS area, Fraser River watershed, 1998–2001. . . . . . . . . . . . . . . . . . . . 12

4. Statistical summary of selected field properties and water-quality constituents for surface 

water at the Fraser River below Crooked Creek at Tabernash, Colorado, 1998–2001 . . . . . . . . . . . . . . 20

APPENDIX I and II TABLES

5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001 . . . . . . . . . . 35

6. Comparison of laboratory results for environmental and quality-control samples for 9 wells 

in the Fraser River watershed, 1998–2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

7. Summary of differences between environmental and quality-control samples for wells in 

the Fraser River watershed, 1998–2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

8. Variability and uncertainty in manganese, ammonia, nitrate, and radon-222 concentrations 

as determined by replicate pairs for wells in the Fraser River watershed, 1998–2001. . . . . . . . . . . . . . 56

 9. Concentrations of major ions, trace elements, nutrients, and dissolved organic carbon in 

blank samples for wells in the Fraser River watershed, 1998–2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
 v

CONVERSION FACTORS, DATUMS, ABBREVIATIONS, AND ACRONYMS

Temperature can be converted to degrees Celsius (°C) or 

degrees Fahrenheit (°F) by the equations:

°C = (°F – 32) / 1.8

°F = 1.8 (°C) + 32

Datums: Vertical coordinate information is referenced to the National Geodetic Vertical 

Datum of 1929 (NGVD 29). Horizontal coordinate information is referenced to the North 

American Datum of 1927 (NAD 27).

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25°C).

Abbreviations and Acronyms

col/100 mL colonies per 100 milliliters

pCi/L picocuries per liter

μm micrometer

AMCL alternative maximum contaminant level

CDPHE Colorado Department of Public Health and Environment

E. coli Escherichia coli

GIS geographic information system

HA health advisory

ISDS individual septic disposal system

LOWESS LOcally WEighted Scatterplot Smooth

LT-MDL long-term method detection level

LRL laboratory reporting level

MBAS methylene blue active substances

MCL maximum contaminant level

MCLG maximum contaminant level goal

MRL minimum reporting level

Multiply By To obtain

acre-foot (acre-ft) 1,233 cubic meter

centimeter per second (cm/s) 0.394 inch per second

cubic foot (ft3) 0.02832 cubic meter

cubic foot per second (ft3/s) 0.02832 cubic meter per second

foot (ft) 0.3048 meter

foot per day (ft/d) 0.3048 meter per day

gallon per day per foot (gpd/ft) 0.000207 cubic meter per second per meter

inch per year (in/yr) 25.4 millimeter per year

microgram per liter (μg/L) 1.0 part per billion

mile (mi) 1.609 kilometer

milligram per liter (mg/L) 1.0 part per million

milliliter (mL) 0.0338 ounce, fluid

pound per square inch (lb/in2) 6.895 kilopascal
vi 

NTU nephelometric turbidity units

NWQL National Water Quality Laboratory

PMCL proposed maximum contaminant level

POC particulate organic carbon

QC quality control

SDWR secondary drinking-water regulation

TT treatment technique

TVS table value standard

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

WY water year (a 12-month period beginning October 1 and ending 

September 30 of the following year. A water year is 

designated as the year in which it ends.)

Abbreviations and Acronyms—Continued
Water-Quality Characteristics and Ground-Water Quantity 

of the Fraser River Watershed, Grand County, Colorado, 

1998–2001

Nancy J. Bauch and Jeffrey B. Bails

Abstract

The U.S. Geological Survey, in cooperation with the 

Grand County Board of County Commissioners, conducted a 

4-year study to assess ground- and surface-water-quality conditions and ground-water quantity in the 302-square-mile Fraser 

River watershed in north-central Colorado. The Fraser River 

flows north about 28 miles from the headwaters near the Continental Divide, through the towns of Winter Park, Fraser, Tabernash, and Granby, and is one of the major tributaries to the 

Upper Colorado River. Increasing urban development, as well 

as the seasonal influx of tourists, is placing more demands on 

the water resources in the Fraser River watershed.

A ground-water sampling network of 11 wells was 

established to represent different aquifer systems (alluvial, 

Troublesome Formation, Precambrian granite), land uses 

(urban, nonurban), and areas with or without individual septic 

disposal system use. The well network was sampled for groundwater quality on a semiannual basis from August 1998 through 

September 2001. The sampling included field properties and the 

collection of water samples for analysis of major ions, trace 

elements, nutrients, dissolved organic carbon, bacteria, methylene blue active substances, and radon-222. One surface-water 

site, on the Fraser River just downstream from the town of 

Tabernash, Colorado, was sampled bimonthly from August 

1998 through September 2001 to assess the cumulative effects 

of natural and human processes on water quality in the upper 

part of the Fraser River watershed. Surface-water-quality sampling included field properties and the collection of water-quality samples for analysis of major ions, trace elements, nutrients, 

organic carbon, and bacteria.

Ground water was a calcium-bicarbonate type water and is 

suitable as a drinking-water, domestic, municipal, industrial, 

and irrigation source. In general, no widespread ground-waterquality problems were indicated. All pH values and concentrations of dissolved solids, chloride, fluoride, sulfate, nitrite, and 

nitrate in the ground-water samples met or were substantially 

less than U.S. Environmental Protection Agency drinkingwater standards and health advisories or State of Colorado 

water-quality standards. Federal standards for turbidity and 

concentrations of iron, manganese, methylene blue active substances, and radon-222 were not met in water samples from at 

least one well. The only ground-water-quality concern assessed 

by this study is radon-222, which was detected in all radonanalyzed samples from 10 wells at levels exceeding the proposed U.S. Environmental Protection Agency drinking-water 

standard of 300 picocuries per liter.

Concentrations of chloride, magnesium, and sulfate were 

statistically different (higher) in ground-water samples from 

wells completed in the alluvial aquifer, urbanized areas, and 

areas with individual septic disposal system use than those from 

wells completed in the Troublesome Formation, nonurban 

areas, and areas without individual septic disposal system use. 

Dissolved organic carbon concentrations were statistically 

higher in ground-water samples from wells completed in the 

alluvial aquifer and areas without individual septic disposal system use than those from wells completed in the Troublesome 

Formation and areas with individual septic disposal system use. 

Differences in dissolved organic-carbon concentrations 

between the latter category and areas without septic systems 

likely had no environmental significance.

 Surface water at the site Fraser River below Crooked 

Creek at Tabernash was a calcium-bicarbonate type water and 

is suitable as a drinking-water, residential, commercial, and irrigation resource. All pH values and concentrations of dissolved 

oxygen were within the State of Colorado instream water-quality standards, and all concentrations of chloride, sulfate, iron, 

manganese, un-ionized ammonia, nitrite, nitrate, and fecal 

coliform bacteria met State standards. Seasonal changes in the 

values or concentrations of field properties and constituents in 

the surface water were detected. For most constituents, maximum concentrations typically occurred during winter with low 

streamflow conditions, and minimums typically occurred during spring as a result of dilution by snowmelt runoff.

Ground-water quantity was estimated for the alluvial and 

Troublesome Formation aquifers in the upper portion of the 

Fraser River watershed, the most likely area for future groundwater use. The estimated average volume of available ground 

water in the alluvial aquifer was about 150,000 acre-feet, with 

seasonal fluctuations of about 7 percent. The Troublesome 

Formation aquifer, which consists of siltstone and interbedded 

sandstone and conglomerate, has approximately 370,000 acrefeet of available water in the upper 500 feet of the aquifer.
2 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

Introduction

Many small towns and rural areas in the Western United 

States had substantial population growth and related land-use 

changes during the last 2 decades of the 20th century and the 

beginning of the 21st century. Outdoor recreation and tourism, 

second-home development, and proximity to resort and mountain areas have been major factors affecting growth and the 

steady urban development of rangeland, forests, and agricultural lands. Many of the communities affected by population 

growth and urban development are in rural areas where little or 

no information is available on the quality of ground water or 

surface water.

One area in Colorado that has seen population growth and 

increased urban development is the Fraser River watershed in 

Grand County (fig. 1), where population increased by more than 

56 percent in the 1990’s (U.S. Census Bureau, 2002). Located 

in north-central Colorado, the Fraser River watershed encompasses about 302 mi2 (square miles) and contains the towns of 

Winter Park, Fraser, Tabernash, and Granby. Two ski areas are 

within the watershed, along with sites for many year-round 

recreational and tourism-based activities. The effect of the rapid 

development of the watershed on the quality of the local water 

resources largely is unknown. Except for some tributaries and

Figure 1. Location of ground- and surface-water sample-collection sites in the Fraser River watershed 

(Arapaho National Forest boundary from Colorado Department of Transportation, 1998).

COLORADO

Ground-water sampling

 site with site number

Surface-water sampling site

U.S. Highway 40

Wastewater-treatment facilities

Arapaho National Forest

Continental

Divide

Fraser River

watershed

Colorado

River

Granby

40 ̊

106 ̊ 105 ̊52'30"

105 ̊45'

Fraser

Winter

Park

Berthoud

Pass

1

2

3

4

5

6

7

9

10

11

12

8

39 ̊52'30"

1

Ground-water sampling

 site in an individual septic

 disposal system area

3

12

Grand County

Moffat Water Tunnel

024

0 2 4 6 KILOMETERS

6 MILES

Vasquez

Water Tunnel

Vasquez Creek

Crooked

Creek

Pole Creek

Hurd Creek

Fraser River

Ranch

Creek

Tenmile Cree k

Strawberry Creek

EXPLANATION

St. Louis

Creek

Tabernash

Base modified from U.S. Geological Survey 

County map series 1:50,000, 1978

Grand County sheets 2 and 4
Introduction 3

the Fraser River itself (Bails, 2003), little historical information 

is available on ground- and surface-water quality in the Fraser 

River watershed. An assessment of available water-quality data 

in the watershed through water year 1997 revealed few groundand surface-water-quality data (Apodaca and Bails, 1999). 

The effects of population growth and the conversion of 

rangeland and forests to urban land uses on ground-water 

quality in the Fraser River watershed were first studied in 1997 

as part of the Upper Colorado River Basin study unit of the 

U.S. Geological Survey (USGS) National Water-Quality 

Assessment Program (Apodaca and Bails, 2000; Apodaca and 

others, 2002). Recognizing the lack of baseline water-quality 

data for the Fraser River watershed, the Grand County Board of 

County Commissioners indicated a need to further characterize 

and monitor water quality in the watershed. In 1998, the USGS, 

in cooperation with the Grand County Board of County 

Commissioners, began a detailed water-quality study in the 

area. The objectives of the study were to (1) assess current 

ground-water quality and quantity in areas with present-day 

development and potential future development in the Fraser 

River watershed, (2) determine the effects of individual septic 

disposal systems (ISDS’s) on ground-water quality, and 

(3) assess current surface-water quality and quantity at a site on 

the Fraser River downstream from the town of Tabernash to 

determine the effects of present-day growth in the watershed 

and to support assessment of future growth. This study provides 

baseline ground- and surface-water information for the Fraser 

River watershed. Water-quality sampling began in August 1998 

and continued through September 2001. Results from the initial 

sampling in August 1998 relating the effects of ISDS’s on 

ground-water quality were described by Apodaca and others 

(2000). 

Purpose and Scope

This report presents an assessment of ground- and surfacewater-quality data and ground-water-quantity data collected by 

the USGS from August 1998 through September 2001 in the 

Fraser River watershed. Ground-water-quality data include 

field properties and concentrations of dissolved solids, major 

ions, selected trace elements, nutrients, organic carbon, bacteria, methylene blue active substances (MBAS), and radon-222 

for water from 11 wells. These data are related to aquifer type 

(alluvial, Troublesome Formation), land use (urban, nonurban), 

and location in ISDS and non-ISDS areas. Ground-waterquality data also are examined for changes over time. The surface-water data include field properties and concentrations of 

dissolved solids, major ions, selected trace elements, nutrients, 

organic carbon, and fecal coliform bacteria for water from one 

site on the Fraser River. This report also presents an estimate of 

the quantity of water available in the alluvial aquifer of the 

Fraser River and in the Troublesome Formation.

Description of the Fraser River Watershed

The Fraser River watershed is in north-central Colorado in 

Grand County (fig. 1) and lies within the Southern Rocky 

Mountains physiographic province (Hunt, 1974). The watershed comprises about 302 mi2

 in the southeastern part of Grand 

County and constitutes about 16 percent of the total area 

(1,869 mi2) of the county. The terrain within the watershed is 

flat in the valleys to mountainous in the southern and eastern 

boundaries, with land-surface altitudes ranging between about 

8,000 and 12,800 ft. The Fraser River flows northerly about 

28 mi from its headwaters along the Continental Divide in the 

Arapaho National Forest though the towns of Winter Park, 

Fraser, Tabernash, and Granby to its confluence with the Colorado River (fig. 1). The primary tributaries to the Fraser River 

are Vasquez, St. Louis, Crooked, Ranch, Tenmile, and Strawberry Creeks (fig. 1). 

Land use/land cover in the Fraser River watershed is 

64 percent evergreen forest; 8 percent deciduous forest; 24 percent pasture, shrubland, and grassland; less than 2 percent 

urban, less than 2 percent perennial ice/snow or bare rock; and 

less than 1 percent open water (fig. 2) (U.S. Environmental Protection Agency, 2002a). For purposes of this report, the land 

use/land cover is classified as “urban” or “nonurban” (forests, 

rangeland, grassland) and “ISDS” or “non-ISDS” area, based 

on a visual examination of land use around a well and well location in an area of historical or new ISDS use or in an area without ISDS use. 

Daily average temperature ranges between 13°F and 55°F. 

Average annual precipitation ranges from 20 inches per year 

north and west of Fraser to more than 40 inches per year in the 

higher peaks along the Continental Divide in the eastern and 

southern portions of the watershed.

The geology of the Fraser River watershed varies from 

rocks of Precambrian age to unconsolidated alluvium of Quaternary age (fig. 3). Igneous and metamorphic rocks (granite, 

gneiss, and schist) of Precambrian age are exposed in the northeastern, eastern, and southern areas of the watershed. Fractured 

rocks of this age generally produce small quantities of water 

that are suitable only for domestic uses. Sedimentary rocks of 

Triassic, Jurassic, and Cretaceous age in the northwestern area 

of the watershed yield little water; however, yields probably are 

sufficient for most domestic purposes. Rocks of Tertiary age or 

younger, including the Troublesome Formation and alluvium, 

have the largest yields for wells in the watershed (Voegeli, 

1965). The Troublesome Formation of Tertiary age is primarily 

siltstone with some interbedded sandstones and conglomerates 

and is as much as 1,000 ft thick. Alluvium consists of unconsolidated sand and gravel and glacial drift and is as much as 

200 ft thick. Recharge is derived mostly from snowmelt 

(Apodaca and others, 2000).

Aquifers in the Fraser River watershed include the alluvial 

aquifer composed of alluvium, the Troublesome Formation 

aquifer composed of rocks of the Troublesome Formation, and 

the Precambrian granite aquifer composed of fractured granite.
4 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

EXPLANATION

39 ̊52'30"

40 ̊

106 ̊

105 ̊52'30"

105 ̊45'

Urban

Deciduous forest Open water

Shrubland

Perennial ice and snow

Evergreen forest

Rangeland

Grassland

Base modified from U.S. Geological Survey 

County map series 1:50,000, 1978

Grand County sheets 2 and 4

Figure 2. Land-use/land-cover classifications for the Fraser River watershed (U.S. Environmental Protection Agency, 

2002a).
Introduction 5

Water from the alluvial and Troublesome Formation aquifers is 

used for residential and municipal purposes.

The population of Grand County in 2000 was 12,442, an 

increase of more than 56 percent since 1990 and more than 

300 percent since 1970 (U.S. Census Bureau, 2002). In addition, the county receives large seasonal influxes of visitors 

related to recreational and tourism-related activities, which add 

to the demand on water resources of the area. Three wastewatertreatment facilities (fig. 1) and public water supplies that service 

the larger population centers are located upstream from Tabernash. The wastewater facilities serve the Winter Park ski area 

and the towns of Winter Park and Fraser and discharge to the 

Fraser River. Discharge from the facilities is highest in winter 

and early spring because of recreational activities. Outside of 

Fraser, well water is used for water supply and ISDS’s are used 

for post-use treatment of sewage.

Acknowledgments

 The authors thank the Grand County Board of County 

Commissioners for their support throughout the study described 

in this report. We also thank the individuals, businesses, and 

agencies that permitted access to their wells for ground-water 

sampling. The authors acknowledge the efforts of Lori Apodaca, Rick Arnold, Steve Char, Jason Gurdak, and C. Michelle 

Smith of the USGS in collecting the ground-water-quality data 

presented in this report, and Jim Martinez and Clay Thompson 

Figure 3. Generalized geology of the Fraser River watershed (Green, 1992; Tweto, 1979).

Base modified from U.S. Geological Survey 

County map series 1:50,000, 1978

Grand County sheets 2 and 4

Igneous rocks of Tertiary and(or) Cretaceous age

01234

01234 5 KILOMETERS

5 MILES

105 ̊52'30"

40 ̊

106 ̊

39 ̊52'30"

105 ̊45'

Granby

Fraser

Winter

Park

Tabernash

Vasquez Creek

Crooke d

Creek

Fraser River

Ranch

Creek

Tenmile Creek

Strawberry Creek

St. Louis Creek

Pole Creek

EXPLANATION

Unconsolidated surficial deposits of

 Quaternary age

Modern alluvium

Gravels and alluvium

Dakota and Morrison Formations

Troublesome Formation–Siltstone,

 sandstone, and conglomerate

Sedimentary rocks of Tertiary age

Sedimentary rocks of Cretaceous and Jurassic age

Igneous and metamorphic rocks of Precambrian age

Pre-Bull Lake age gravel and alluvium

Pierre Shale, undivided

Colorado Group

Granitic rock of 1,400 Mega-annum

Granitic rock of 1,700 Mega-annum

Biotite gneiss, schist, and migmatite

Felsic and hornblende gneisses, either separate or interlayered

Windy Gap Member of the Middle

 Park Formation

Sedimentary rocks of Cretaceous age

Sedimentary rocks, broadly classified

Coalmont Formation–Sandstone, shale,

 coal beds, and conglomerate

Laramide instrusive rocks

Mesozoic rocks–Mainly early Cretaceous,

 Jurassic, and Triassic age

Ash-flow tuff of main volcanic

 sequence

Glacial drift of Pinedale and Bull

 Lake Glaciations or Pre-Bull Lake

 age 
6 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

of the USGS in collecting the surface-water-quality data. 

Thanks also are extended to Lori Apodaca and Daniele Chafin 

for technical review of the manuscript, Mary Kidd for editorial 

review, Sharon Powers for illustrations, John Evans for cover 

design, and Alene Brogan for manuscript preparation and layout.

Data Collection and Analysis

Water-quality data were collected from August 1998 

through September 2001 at 11 ground-water sites, including 

2 sites that were sampled for only a portion of the study, and 

1 surface-water site (fig. 1, table 1). The 11 ground-water sites 

were selected to represent different aquifers, different land-use 

settings, and varying depths to ground water within the Fraser 

River watershed. Well selection was based on well availability, 

location in areas with historical or new ISDS use or non-ISDS 

use, and areal distribution throughout the study area. Well 1, 

currently in a nonurban and non-ISDS area, was added to the 

sample-collection network in 2000 upon the request of the 

cooperator, the Grand County Board of County Commissioners, 

because of impending development in the area. Data collection 

at well 3 was discontinued after 1999 because it represented a 

ground-water resource that was sufficiently represented by 

other wells in the same area. Wells were located in fractured 

granite (one well), in the sedimentary Troublesome Formation 

(four wells), and in alluvium (six wells) and ranged in depth 

from 18 to 295 ft. The single surface-water site (site 12, Fraser 

River below Crooked Creek at Tabernash) was selected to represent the integration of the effects of natural and human factors 

on surface-water quality in the Fraser River watershed upstream 

from Tabernash. 

Ground-water quantity was evaluated for the surficial alluvial aquifer and the Troublesome Formation aquifer. The areal 

extent of the aquifers was derived from geologic maps of 

Colorado (Green, 1992; Tweto, 1979). Information on aquifer 

thickness was gathered from lithologic well logs obtained at the 

Colorado Division of Water Resources. Aquifer properties were 

derived from available aquifer-test information as well as comparison to similar aquifer systems. A more detailed discussion 

of the estimation of ground-water quantity, or the amount of 

water available to be withdrawn by wells, in the alluvial and 

Troublesome Formation aquifers can be found in the “GroundWater Quantity” section of this report.

Table 1. Description of 11 ground-water wells and one surface-water sampling site in the Fraser River watershed, 

August 1998–September 2001.

[USGS, U.S. Geological Survey; ft, feet; ISDS, individual septic disposal system; CFC, chlorofluorocarbon; M, monitoring; Muni, municipal; D, domestic; Fm, 

Formation; NU, nonurban; U, urban]

Site 

number

(fig. 1)

USGS station

number

Altitude

(ft)

Well 

type Aquifer1

Well 

depth 

below 

land 

surface

(ft)

Land 

use

Location in 

ISDS 

area

CFC estimated 

recharge 

date2

Datacollection 

period for 

well

Ground-water-quality wells

 1 395623105481000 8,619 M Alluvial 18 NU No 31989 2000–01

 2 395658105485400 8,568 Muni Troublesome Fm 110 U No 1983 or

younger

1998–2001

 3 395642105500700 8,685 D Troublesome Fm 145 U Yes 1968 1998–99

 4 395657105495300 8,610 D Alluvial 85 U Yes 1980 1998–2001

 5 395750105515800 8,665 D Troublesome Fm 120 NU Yes 1979 1998–2001

 6 395921105472300 8,531 D Alluvial 75 NU No 1991 1998–2001

 7 395942105502000 8,332 D Alluvial 65 U Yes 1969 or

younger

1998–2001

 8 395937105500500 8,342 D Alluvial 25 U Yes 1990’s 1998–2001

 9 395929105510300 8,320 M Alluvial 28 U No 1976 1998–2001

 10 395928105533500 8,592 D Troublesome Fm 295 NU No 1968 1998–2001

 11 395907105540100 8,582 D Precambrian granite 105 NU No 1955 1998–2001

Surface-water-quality site

12 09033300 8,270 Station name: Fraser River below Crooked Creek at Tabernash, Colorado

1From Tweto (1979) and Green (1992).

2From Apodaca and others (2000), unless otherwise noted.

3

From Apodaca and others (2002).
Data Collection and Analysis 7

Data Collection

Ground-water samples were collected from the 11 wells 

semiannually during the spring and fall, following procedures 

outlined in Koterba and others (1995). Well water was sampled 

using either a submersible pump (no pressure tanks) or through 

an outside household spigot (all downstream from pressure 

tanks). During each sampling visit, field properties (water 

temperature, specific conductance, dissolved-oxygen concentration, pH, turbidity, and acid-neutralizing capacity) were 

measured, and ground-water samples were collected for 

laboratory analysis. 

Surface-water samples from site 12 (Fraser River) were 

collected bimonthly following procedures outlined in the USGS 

National Field Manual (U.S. Geological Survey, 1997 to 

present). Discharge and field properties (water temperature, 

specific conductance, dissolved-oxygen concentration, and pH) 

were measured, and surface-water samples were collected for 

laboratory analysis using the equal-width-increment method.

Ground- and surface-water samples collected for analysis 

of dissolved solids, major ions, trace elements, and nutrients 

were filtered onsite through a 0.45-μm cellulose filter. Samples 

collected for analysis of dissolved organic carbon were filtered 

through a 0.45-μm silver filter. The silver filter was saved for 

analysis of particulate organic carbon. Samples collected for the 

analysis of suspended sediment and total recoverable phosphorus were not filtered. Samples collected for nutrient and dissolved and particulate organic carbon analysis were chilled to 

4°C, and all samples except suspended sediment were transported to and analyzed at the USGS National Water Quality 

Laboratory (NWQL) in Lakewood, Colo. Suspended-sediment 

samples were analyzed for suspended-sediment concentration 

at the USGS Iowa Sediment Laboratory in Iowa City, Iowa. The 

procedures used for processing and preservation of the waterquality samples are described in Koterba and others (1995) and 

in the USGS National Field Manual (U.S. Geological Survey, 

1997 to present). 

Unfiltered samples for the analysis of bacteria (total 

coliform, Escherichia coli [E. coli], and fecal coliform) were 

collected in the field using sterilized equipment. Bacteria samples were collected last, and the samples were processed within 

6 hours of collection. Collection and processing were done 

using m-ENDO and NA-MUG media for ground water and mFC media for surface water (Britton and Greeson, 1989; U.S. 

Environmental Protection Agency, 1991; American Public 

Health Association, American Water Works Association, and 

Water Pollution Control Federation, 1999).

For MBAS, unfiltered water samples were collected and 

chilled until analyzed. Samples for the analysis of radon-222 

were collected by withdrawing 10 mL of water into a glass 

syringe and injecting this water into a glass scintillation vial 

beneath mineral oil (U.S. Geological Survey, 1997 to present).

After sampling at each site, all equipment except that for 

bacteria sampling was cleaned with a 0.1-percent nonphosphate 

detergent solution and then rinsed with tap water and distilled 

water. Tubing was stored in clean, sealable plastic bags, and 

organic carbon and radon equipment was reassembled, wrapped 

in aluminum foil, and stored in clean containers. Bacteria sampling equipment was washed, wrapped in craft paper, and then 

sterilized in the laboratory by autoclaving at 121°C at 15 lb/in2

for 20 minutes. 

Data Analysis

Analysis of ground- and surface-water data collected for 

this study was conducted in a two-step process. First, groundand surface-water samples were analyzed at the USGS NWQL. 

Then these results, along with the ground- and surface-water 

field properties, were analyzed using various statistical 

methods. 

Laboratory Analysis

At the USGS NWQL, the ground- and surface-water samples were analyzed for concentrations of dissolved solids, major 

ions, trace elements (iron and manganese), nutrients (ammonia 

[un-ionized ammonia (NH3) plus ammonium (NH4

+)]), total 

and(or) dissolved ammonia plus organic nitrogen, nitrite, nitrate 

plus nitrite (hereinafter nitrate), total or dissolved phosphorus, 

and orthophosphate), and dissolved organic carbon. The nutrients represent concentrations as either nitrogen or phosphorus. 

Ground-water samples also were analyzed for MBAS and 

radon-222, and surface-water samples also were analyzed for 

particulate organic carbon. Except for these latter three constituents plus bacteria and constituents as total concentrations, all 

samples were in the dissolved form. Samples for major ions and 

nutrients were extracted and analyzed by various methods 

(Fishman and Friedman, 1989; Fishman, 1993; U.S. Environmental Protection Agency, 1993). Samples for dissolved 

organic carbon were analyzed by UV-promoted persulfate oxidation and infrared spectrometry (Brenton and Arnett, 1993), 

and samples for particulate organic carbon were analyzed by 

wet-chemical oxidation and infrared spectrometry (Burkhardt 

and others, 1997). Samples for MBAS were analyzed using procedures described by Burkhardt and others (1995), and samples 

for radon-222 were analyzed by liquid scintillation counting 

(American Society for Testing and Materials, 1999).

The analytical results from the NWQL were reported as 

either the minimum reporting level (MRL) or laboratory reporting level (LRL), along with the long-term method detection 

level (LT-MDL). The minimum reporting level is defined by 

the NWQL as the smallest measured concentration of a constituent that may be reliably measured using a given analytical 

method (Timme, 1995). For some constituents, the reporting 

level was changed at the beginning of a water year from the 

MRL to the LT-MDL and LRL (Childress and others, 1999). 

The LT-MDL is the lowest concentration of a constituent that is 

reported by the NWQL and represents that value at which the 

probability of a false positive is statistically limited to less than 

or equal to 1 percent. The LRL is calculated as 2 times the 

LT-MDL and represents the value at which the probability of a 
8 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

false negative is less than or equal to 1 percent. Concentrations 

detected between the LT-MDL and LRL are reported as estimated (E) concentrations. Concentrations detected at values 

less than the MRL, LT-MDL, or undetected are reported with a 

“less than” (<) symbol at the MRL or the LRL (Childress and 

others, 1999). The LT-MDL and LRL for a constituent may 

change annually on a water-year basis. 

Statistical Methods

Water-quality data were analyzed using nonparametric 

statistical methods. Nonparametric methods were used because 

they do not require data sets to be normally distributed, are 

resistant to outliers, and are appropriate for use with small data 

sets (Helsel and Hirsch, 1992). The two-tailed Wilcoxon ranksum test was used to determine if the distribution of the groundwater-quality data was significantly different among aquifer 

types (alluvial, Troublesome Formation), land use (urban, nonurban), and ISDS and non-ISDS areas. Results of the test are 

expressed in terms of p-values—the probability of rejecting or 

not rejecting the hypothesis that the data sets of the comparison 

categories are similar. The test does not prove that the data sets 

are similar, only that similarity in data sets can be rejected or not 

rejected. Test results were considered to be statistically significant when the p-value of the respective test was less than or 

equal to 0.05, indicating that there was at least a 95-percent 

probability that there were differences in water-quality data and 

related median values between the comparison categories. The 

case against similarity in data increased as p-values got smaller 

and smaller. For results with p-values greater than 0.05, the 

hypothesis of similarity in data sets could not be rejected. Data 

for the Precambrian granite aquifer were excluded from the 

comparison of aquifer types because of the small size of the data 

set (seven samples). Water temperature and radon-222 data 

were excluded from comparisons for land use and ISDS/nonISDS areas because processes on or near the land surface should 

have no effect on water temperature and radon-222 concentrations in ground water. Data that were reported with a less-than 

(<) symbol were given a value equal to one-half the respective 

MRL or LRL for comparison testing. Results of the two-tailed 

Wilcoxon rank-sum tests for some constituents were excluded 

from discussion in this report because elevated concentrations 

in one or more wells biased the results. Additional information 

on the Wilcoxon rank-sum test is found in Helsel and Hirsch 

(1992) and Ott (1993). 

With statistical testing such as the Wilcoxon rank-sum test, 

differences in water-quality data between categories can be 

statistically significant but not environmentally significant. For 

example, statistically significant differences in nitrate concentrations between two land uses would not be environmentally 

important if nitrate concentrations were centered around 

1.50 mg/L for one land use and 0.090 mg/L for the other land 

use. Nitrate concentrations in the water for both land uses 

would be considered low and would not be of concern 

environmentally.

Changes in ground-water quality with time were qualitatively examined by graphing individual constituents for a site 

against time, fitting a LOWESS smooth curve (Helsel and 

Hirsch, 1992) to the data, and visually examining the graphs for 

changes. Quantitative analyses of changes with time or trends 

were not used because the time periods of the data sets were of 

insufficient length (maximum of 4 years), and the data sets were 

of insufficient size (maximum of seven samples) to perform statistical tests for trend analysis, such as the Mann-Kendall test or 

the seasonal Kendall test. Also, data collection only occurred in 

2 months of each year. Graphs of changes with time were developed for most water-quality constituents, including water temperature, specific conductance, pH, turbidity, dissolved-oxygen 

concentration, acid-neutralizing capacity, dissolved solids, 

major ions (calcium, magnesium, sodium, potassium, chloride, 

and sulfate), silica, nutrients (nitrate and orthophosphate), and 

dissolved organic carbon. Manganese was included when most 

or all manganese concentrations for a given well were greater 

than the reporting level. Graphs were not developed for bromide, fluoride, ammonia, ammonia plus organic nitrogen, 

nitrite, iron, total coliform bacteria, and MBAS because most 

concentrations for these constituents were less than the respective laboratory reporting levels. Phosphorus was excluded 

because of its similarity in concentration to orthophosphate. 

Radon-222 and data for wells 1 and 3 also were excluded 

because only four or fewer samples were collected at each site 

or from the two wells.

Water-Quality Standards

Ground-water data were compared to U.S. Environmental 

Protection Agency (USEPA) primary, secondary, proposed, 

and alternative drinking-water standards and treatment techniques (U.S. Environmental Protection Agency, 2002b) and 

State of Colorado water-quality standards, where applicable 

(Colorado Department of Public Health and Environmental, 

2001). Primary drinking-water standards consist of maximum 

contaminant levels (MCL’s), which are the highest values or 

concentrations of contaminants allowed in public water-supply 

systems to protect human health. MCL’s are legally enforceable 

standards. Secondary drinking-water regulations (SDWR) are 

related to the esthetic and cosmetic qualities of the water, such 

as taste and odor or tooth and skin discoloration, and are not 

legally enforceable. The USEPA-proposed MCL and proposed 

alternative MCL (AMCL) that are applicable to this report are 

under review and are not currently (2003) enforceable. USEPA 

treatment techniques are required processes that aim to lower 

the levels of contaminants in drinking water.

Instream water-quality standards have been established for 

selected field properties and water-quality constituents for the 

Fraser River and its tributaries by the Colorado Department of 

Public Health and Environment (Colorado Department of Public Health and Environment, 2002). The water-quality standards 

are numeric values or table value standards (TVS). The Fraser 
Water Quality 9

River and its tributaries are given the highest (class 1) aquatic 

life and recreational qualifications allowable.

In 2000, USEPA established recommended nutrient criteria for rivers and streams in ecoregion II–Western Forested 

Mountains, including the Fraser River watershed. The intent of 

these criteria is to identify baseline conditions for rivers and 

streams that are minimally affected by human activities and 

protect against nutrient enrichment from cultural eutrophication 

(U.S. Environmental Protection Agency, 2000a). These criteria 

are guidance that States and tribes may use as a starting 

point in establishing their water-quality standards (U.S. Environmental Protection Agency, 2000a). For ecoregion II, the recommended criterion for total phosphorus in rivers and streams 

is 0.010 mg/L (U.S. Environmental Protection Agency, 2000a). 

Because the total phosphorus criterion only is a guidance for 

establishing standards and is not a legally enforceable criterion, 

it will be excluded from the discussions about ground- and surface-water quality in the Fraser River watershed.

Water Quality

Water-quality data for ground water and surface water 

include field properties, dissolved solids and(or) major ions, 

selected trace elements, nutrients, organic carbon, and bacteria. 

Ground-water data also include MBAS and radon-222. Groundwater data are related to aquifer type, type of land use, and the 

presence or absence of ISDS’s and are examined for changes 

over time. To the extent required, interpretation of water-quality data is limited or qualified by quality-control factors, as 

described in Appendix II—“Quality-Control Methods and 

Analysis” at the end of this report.

Ground Water

All water-quality constituents for ground water are in the 

dissolved form except for total coliform bacteria, MBAS, and 

radon-222. A statistical summary of selected ground-water 

data, USEPA and State of Colorado water-quality standards, 

and NWQL reporting levels is listed in table 2. A full listing of 

ground-water-quality data is in table 5 in Appendix I.

Field Properties

Water temperature for 86 percent of the wells was less than 

10°C. Temperatures above 10°C were measured only in two 

wells (sites 5 and 11) near Tabernash. Well 5 is 120 ft deep in 

the Troublesome Formation, and well 11 is 105 ft deep in the 

Precambrian fractured granite. Water temperature from site 5 

generally was about two times higher than temperatures from 

the other wells. Sample collection for this well took place at an 

outside household spigot, and the temperature of the water may 

have increased as the water traveled through the pressure tank 

and plumbing system. There is no known hydrothermal activity 

in the area. No statistical relation was detected between well 

depth and water temperature. There was a statistically significant difference in water temperature between the alluvial and 

the Troublesome Formation aquifers (table 3); the median water 

temperature was cooler in the alluvial aquifer.

Specific conductance, defined as the ability of water to 

conduct an electric current at 25°C, provides an indication of 

ion concentration. As ion concentrations increase, specific conductance increases (Hem, 1992). Specific conductance for 

ground water in the Fraser River watershed was low to moderate, ranging between 88 and 430 μS/cm (table 2). Median values of specific conductance were lowest in the vicinity of Fraser 

and Winter Park and were highest in the Tabernash area. 

Well 8 had the highest median specific conductance, 

392 μS/cm.

Most (76 percent) dissolved-oxygen concentrations measured in ground water for this study were greater than 1.0 mg/L. 

Dissolved-oxygen concentrations less than 1.0 mg/L, which can 

be indicative of reducing conditions, were measured in three 

wells, one in the Troublesome Formation aquifer near Fraser 

(well 2) and two in the alluvial aquifer near Tabernash (wells 7 

and 9). Some metals such as iron and manganese are more soluble under reducing conditions (Hem, 1992). Dissolved-oxygen 

concentrations in sites 7 and 9 were particularly low—less than 

or equal to 0.7 mg/L for all samples. Dissolved-oxygen concentrations below 1.0 mg/L are considered low for the Fraser River 

watershed (Apodaca and Bails, 1999). Statistically significant 

differences in dissolved-oxygen concentrations were detected 

for aquifer type and land use (table 3); median dissolvedoxygen concentrations were lower in the alluvial aquifer and in 

urban areas than in the Troublesome Formation aquifer and 

nonurban areas. Ground water is supplied with dissolved oxygen through recharge and the movement of air through the 

unsaturated zone above the water table (Hem, 1992). Low 

dissolved-oxygen concentrations may result from the interaction of ground water with oxidizable materials (organic matter 

and reduced minerals) along the flow path of the water and(or) 

from microbiological activities. The lower dissolved-oxygen 

concentrations in the alluvial aquifer and urban wells may 

represent natural conditions or may indicate the addition of 

organic matter through human activities, including fertilizers or 

septic systems. Of the three wells with low dissolved-oxygen 

concentrations, only site 7 is in an ISDS area.

Almost all pH values were within the USEPA SDWR of 

6.5 to 8.5 (table 2). The exception was site 1, where pH in the 

water samples ranged from 6.1 to 6.5. A pH of 7.0 indicates 

neutral pH, less than 7.0 indicates the water is acidic, and pH 

greater than 7.0 indicates the water is basic. Site 1 is very shallow—only 18 ft deep, and ground water is frequently in contact 

with the soil horizon. Humic acids from the soil horizon 

decrease pH in the ground water. Values of pH were statistically 

different for aquifer types and land use (table 3). Median pH 

was lower in alluvial aquifer and urban well-water samples than 

in water samples from the Troublesome Formation aquifer and 

nonurban areas. It is not known why urban wells had a generally 

lower pH than did nonurban wells.
10 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 2. Statistical summary of selected ground-water data for the Fraser River watershed, 1998–2001, with U.S. Environmental Protection Agency and State of Colorado water- quality standards and U.S. Geological Survey National Water Quality Laboratory reporting levels. [All water-quality constituents are in the dissolved form except for total coliform bacteria, methylene blue active substances, and radon-222. USEPA, U.S. Environmental Protection Agency; USEPA water-quality standards and health advisory are from U.S. Environmental Protection Agency (2002b) unless otherwise noted; WY, water year; MRL, minimum reporting level; LT-MDL, long-term method detection level; LRL, laboratory reporting level; °C, degrees Celsius; --, no standard determined; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; SDWR, USEPA secondary drinking-water regula- tion; NTU, nephelometric turbidity units; TT, treatment techniques; WQS, water-quality standard; <, less than; μg/L, micrograms per liter; E, estimated; N, nitrogen; HA, health advisory; MCL, maximum contami- nant level; nitrate is nitrate plus nitrite; P, phosphorus; C, carbon; col/100 mL, colonies per 100 milliliters; MCLG, maximum contaminant level goal; pCi/L, picocuries per liter; AMCL, alternative maximum contaminant level] Field properties, constituents, and reporting units Number of samples Minimum Median Maximum USEPA water-quality standard or health advisory WY 1998 WY 1999 WY 2000 WY 2001 MRL LT-MDL LRL (*=MRL) LT-MDL LRL (*=MRL) LT-MDL LRL (*=MRL) Field properties Water temperature 

(°C)

70 4.0 7.3 15.0 -- 0.1 *0.1 *0.1 *0.1

Specific conductance 

(μS/cm)

70 88 260 430 -- 1.0 *1.0 *1.0 *1.0

Oxygen, dissolved 

(mg/L)

70 0.1 3.8 10.1 -- 0.1 *0.1 *0.1 *0.1

pH (standard units) 70 6.1 7.6 8.5 6.5–8.5 (SDWR) 0.1 *0.1 *0.1 *0.1Turbidity (NTU) 69 0.1 0.3 7.7 15.0 (TT) 1.0 *1.0 *1.0 *1.0

Dissolved solids, major ions, and trace elements

Dissolved solids 

(mg/L)

67 55 165 269 2400 mg/L or 1.25 times 

background level (WQS)

Computed concentration3

Chloride (mg/L) 70 0.3 2.6 24.7 250 (SDWR) 0.1 *0.1 0.14 0.29 0.04 0.08Sulfate (mg/L) 67 <0.3 2.9 16.0 250 (SDWR) 0.1 *0.1 0.15 0.31 0.05 0.11Iron (μg/L) 70 <10 <10 310 300 (SDWR) 10 5 10 5 10 5 10Manganese (μg/L) 70 E 2.0 <3.2 510 50 (SDWR) 4 1.5 3 1.1 2.2 1.6 3.2

Nutrients and dissolved organic carbon

Ammonia,4 as N 

(mg/L)

70 <0.002 <0.002 0.040 30 (HA) 0.002 *0.002 *0.002 *0.002

Nitrite, as N (mg/L) 69 <0.001 <0.001 0.004 1 (MCL) 0.001 *0.001 *0.001 *0.001Nitrate, as N (mg/L) 70 <0.005 0.208 4.72 10 (MCL) 0.005 *0.005 *0.005 *0.005Orthophosphate, as P 

(mg/L)

70 E 0.005 0.047 0.137 -- 0.001 *0.001 *0.001 0.004 0.007

Dissolved organic 

carbon, as C (mg/L)

70 0.2 0.91 4.0 -- 0.1 *0.1 0.16 0.33 0.16 0.33

Total coliform bacteria, methylene blue active substances, and radon-222
Water Quality 11

Total coliform 

bacteria 

(col/100 mL)

68 <1 <1 E 140 55% (MCLG) 1 *1 *1 *1

Methylene blue active 

substances (mg/L)

69 <0.02 <0.02 3.82 0.5 (SDWR) 0.02 *0.02 *0.02 0.02

Radon-222, total 

(pCi/L)

30 365 760 6,380 6300 (proposed MCL) 74,000 (proposed 

AMCL)

*26 *26 *26 *26

1Treatment techniques are U.S. Environmental Protection Agency required processes, from U.S. Environmental Protection Agency (2002b).2Maximum allowable dissolved-solids concentration in ground water is the value that is less restrictive; applies to “agricultural use—quality,” “surface-water quality protection,” and “potentially usable quality” 

classes of ground water, from Colorado Department of Public Health and Environment (2001).

3Dissolved solids (sum of constituents) is computed as the sum of calcium, magnesium, sodium, potassium, silica, chloride, sulfate, and carbon (as carbonate equivalent) plus any other constituents, such as 

dissolved iron, if they are present in the water.

4Un-ionized ammonia [NH3] plus ammonium [NH4+].5No more than 5 percent of samples can be total coliform-positive in a month. Every sample that has total coliforms must be analyzed for fecal coliforms; no fecal coliforms are allowed. From 

U.S. Environmental Protection Agency (2002b). 

6Under review, from U.S. Environmental Protection Agency (2000b). 7Applies to those States that create Multimedia Mitigation programs to address radon in indoor air. Under review, from U.S. Environmental Protection Agency (2000b). 

Table 2. Statistical summary of selected ground-water data for the Fraser River watershed, 1998–2001, with U.S. Environmental Protection Agency and State of Colorado waterquality standards and U.S. Geological Survey National Water Quality Laboratory reporting levels.—Continued[All water-quality constituents are in the dissolved form except for total coliform bacteria, methylene blue active substances, and radon-222. USEPA, U.S. Environmental Protection Agency; USEPA water-quality 

standards and health advisory are from U.S. Environmental Protection Agency (2002b) unless otherwise noted; WY, water year; MRL, minimum reporting level; LT-MDL, long-term method detection level; LRL, 

laboratory reporting level; °C, degrees Celsius; --, no standard determined; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; SDWR, USEPA secondary drinking-water regulation; NTU, nephelometric turbidity units; TT, treatment techniques; WQS, water-quality standard; <, less than; μg/L, micrograms per liter; E, estimated; N, nitrogen; HA, health advisory; MCL, maximum contaminant level; nitrate is nitrate plus nitrite; P, phosphorus; C, carbon; col/100 mL, colonies per 100 milliliters; MCLG, maximum contaminant level goal; pCi/L, picocuries per liter; AMCL, alternative maximum 

contaminant level]

Field properties, 

constituents, and 

reporting units

Number 

of 

samples

Minimum Median Maximum

USEPA

water-quality

standard or health

advisory

WY 1998 WY 1999 WY 2000 WY 2001

MRL LT-MDL LRL (*=MRL) LT-MDL LRL (*=MRL) LT-MDL LRL (*=MRL)
12 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 3. Results of two-tailed Wilcoxon rank-sum tests for comparison of selected field properties and water-quality constituents in wells by aquifer type, land use, and individual septic disposal system (ISDS) or non-ISDS area, Fraser River watershed, 1998–2001. [All water-quality constituents are in the dissolved form except for total coliform bacteria, methylene blue active substances, and radon-222. n, number of samples; Troubl. Fm., Troublesome Formation; 

p-value is the significance level of the two-tailed Wilcoxon rank-sum test. A p-value less than or equal to 0.05 (shown in bold type) indicates that the hypothesis of similarities in values or concentrations 

between the tested groups is rejected, and there is a statistically significant difference between the tested groups. ISDS, individual septic disposal system; °C, degrees Celsius; NA, not applicable; μS/cm, 

microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; <, less than; NTU, nephelometric turbidity units; μg/L, micrograms per liter; E, estimated; N, nitrogen; nitrate is nitrate plus 

nitrite; P, phosphorus; C, carbon; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter]

Field properties, constituents,

and reporting units

Aquifer Land use Septic disposal

Alluvial

median, 

(n)

Troubl. 

Fm.

median, 

(n)

p-value

Urban

median, 

(n)

Nonurban

median, 

(n)

p-value

ISDS

median, 

(n)

Non-ISDS

median, 

(n)

p-value

Temperature (°C) 6.6, (39) 7.3, (24) 0.024 6.6, (38) 8.0, (32) NA 6.7, (31) 7.3, (39) NASpecific conductance (μS/cm) 256, (39) 256, (24) 0.343 258, (38) 260, (32) 0.981 260, (31) 256, (39) 0.244Dissolved oxygen (mg/L) 1.9, (39) 4.8, (24) <0.001 1.0, (38) 4.6, (32) <0.001 4.3, (31) 3.4, (39) 0.892pH (standard units) 7.3, (39) 7.8, (24) 0.048 7.2, (38) 7.9, (32) <0.001 7.6, (31) 7.5, (39) 0.385Turbidity (NTU) 0.3 (38) 0.2 (24) 0.016 0.3, (37) 0.3, (32) 0.732 0.3, (31) 0.22, (38) 0.285Dissolved solids (mg/L) 168, (38) 158, (22) 0.342 168, (37) 160, (30) 0.668 162, (31) 166, (36) 0.349Chloride (mg/L) 4.5, (39) 1.5, (24) 0.002 4.6, (38) 1.5, (32) <0.001 4.8, (31) 1.8, (39) 0.021Magnesium (mg/L) 4.39, (39) 3.41, (24) 0.005 4.40, (38) 2.10, (32) <0.001 3.53, (31) 2.44, (39) <0.001Sulfate (mg/L) 4.5, (38) 2.7, (22) <0.001 4.0, (37) 2.5, (30) <0.001 3.1, (31) 2.7, (36) 0.004Iron (μg/L) <10 (39) <10, (24) 0.006 <10, (38) <10, (32) 0.075 <10, (31) <10, (39) NAManganese (μg/L) <4.0, (39) <3.0, (24) 0.008 E 6.2, (38) <3.0, (32) NA 3.9, (31) <3.0, (39) <0.001Ammonia,1 as N (mg/L) 0.002, (39) <0.002, (24) 0.311 <0.002, (38) <0.002, (32) 0.761 <0.002, (31) 0.003, (39) 0.522Nitrate, as N (mg/L) 0.110, (39) 0.216, (24) 0.590 0.222, (38) 0.204, (32) 0.444 0.206, (31) 0.214, (39) 0.328Orthophosphate, as P (mg/L) 0.047, (39) 0.121, (24) <0.001 0.048, (38) 0.048, (32) 0.288 0.028, (31) 0.061, (39) <0.001Dissolved organic carbon, as C (mg/L) 1.8, (39) 0.69, (24) 0.010 1.1, (38) 0.83, (32) 0.878 0.70, (31) 1.0, (39) 0.008Total coliform bacteria (col/100 mL) <1, (37) <1, (24) 0.057 <1, (36) 1, (32) 0.983 <1, (30) <1, (38) 0.557Methylene blue active substances (mg/L) <0.02, (39) <0.02, (23) 0.006 <0.02, (38) <0.02, (31) 0.681 <0.02, (31) <0.02, (38) 0.834Radon-222, total (pCi/L) 710, (15) 1074, (12) 0.479 1096, (18) 661, (12) NA 784, (15) 752, (15) NA

1Un-ionized ammonia [NH3] plus ammonium [NH4

+].
Water Quality 13

Turbidity, the cloudiness of water, can foster the growth of 

microbes and impede the water-disinfection process (Apodaca 

and Bails, 2000). Turbidity for water samples from all wells 

except site 1 was less than 5.0 nephelometric turbidity units 

(NTU), the USEPA treatment technique value for public-supply 

water (table 2); most were less than or equal to 2.4 NTU. Higher 

turbidity for water samples from site 1 probably was due to the 

shallowness of the well and its location in a field that frequently 

has standing water. The median turbidity for water samples 

from alluvial aquifer wells was statistically higher than the 

median turbidity for water samples from wells in the Troublesome Formation aquifer (table 3).

Dissolved Solids, Major Ions, and Trace Elements

Dissolved solids, major ions, and trace elements in uncontaminated ground water are the result of the natural dissolution 

of materials along the ground-water flow path in soil and rock. 

Dissolved-solids concentration is used as one indicator of the 

suitability of water for drinking, residential, and industrial use, 

and irrigation purposes. The concentrations of dissolved solids 

in water samples from wells in the Fraser River watershed were 

low to moderate, ranging from 55 to 269 mg/L (table 2) and 

indicated that the water is suitable for domestic, municipal, 

industrial, and agricultural uses. Median dissolved-solids 

concentrations were lowest in the vicinity of Fraser and Winter 

Park and were highest around and to the west of Tabernash. 

Water samples from site 8 had the greatest median dissolvedsolids concentration, 252 mg/L. All dissolved-solids concentrations were less than the State of Colorado water-quality

standard of 400 mg/L (table 2). 

The dominant water type in the ground-water samples was 

calcium-bicarbonate type water (fig. 4). Only in samples from 

site 1 was the water type a mixed-cation (calcium-potassium or 

calcium-sodium) -bicarbonate type water or a mixed-cation 

(calcium-potassium or calcium-sodium) -mixed-anion (bicarbonate-chloride) type water. 

There were differences among the wells in the concentrations of the major ions that formed the calcium-bicarbonate type 

water. Median concentrations of most major ions were greatest 

for wells in the Tabernash area, especially site 8. The median 

chloride concentration for water samples from site 8 was 

3 times greater than the median concentrations for samples from 

the other wells, and all sulfate concentrations in samples from 

site 8 were greater than 10 mg/L. Site 7, located just east of 

site 8, was the only other well with a sulfate concentration 

greater than 10 mg/L. The Tabernash area, including sites 7 and 

8, is the most downgradient part of the study area. Because of 

this, the ground water would have had a longer residence time, 

which could cause the increase in specific conductance and 

higher concentrations of dissolved solids and major ions. Chloride and sulfate concentrations in water samples from all wells 

were substantially less than the USEPA SDWR of 250 mg/L for 

each constituent (table 2). Concentrations of chloride, magnesium, and sulfate in water samples from wells in the alluvial 

aquifer and urban and ISDS areas were statistically higher than 

those from wells in the Troublesome Formation aquifer and 

nonurban and non-ISDS areas, as indicated by median concentrations of the three ions (table 3). 

Sources of chloride in ground water can include natural 

processes (evaporative concentrations in precipitation, brines, 

dissolution of halite, fluid inclusions in rock) and human activities (fertilizers, septic-system effluent, road salt). In other areas 

of the Southern Rocky Mountains physiographic province, 

chloride concentrations have been higher in urban than nonurban areas (Apodaca and Bails, 2000). Magnesium can be a 

major constituent of igneous and metamorphic rocks, depending on the presence or alteration of ferromagnesian minerals in 

the rocks, and is present in minerals such as dolomite in sedimentary rocks. Most sulfate in ground-water samples from the 

11 wells probably resulted from the oxidation of sulfide minerals in igneous and sedimentary rocks in the watershed. Greater 

magnesium and sulfate concentrations in urban wells as compared to the nonurban wells probably resulted from the greater 

exposure of the ground water to more igneous and metamorphic 

rocks and sulfide minerals in the more areally extensive watershed draining to the urban areas.

Concentrations of iron in the ground-water samples ranged 

from less than 10 to 310 μg/L (table 2). Concentrations greater 

than the reporting level of 10 μg/L only were detected in samples from sites 4, 6, and 7. The highest concentrations occurred 

in water samples from site 7 (median of 210 μg/L), with one 

sample exceeding the USEPA SDWR for iron of 300 μg/L 

(table 2). Manganese concentrations ranged from an estimated 

2 μg/L to 510 μg/L (table 2), with water samples from four 

wells having concentrations greater than the laboratory reporting levels. Elevated concentrations occurred in samples from 

site 7 (median of 457 μg/L) and site 9 (median of 73.8 μg/L). 

All seven samples from site 7 had manganese concentrations 

greater than the USEPA SDWR for manganese of 50 μg/L 

(table 2), as did four of seven samples for site 9. As discussed 

in “Field Properties,” the solubility of iron and manganese 

increases when reducing conditions (characterized by very low 

dissolved-oxygen concentrations) are present in an aquifer. 

Median dissolved-oxygen concentrations for water samples 

from sites 7 and 9 were low, 0.2 and 0.5 mg/L, respectively, and 

indicated the presence of reducing conditions. Manganese concentrations in water samples from wells in the alluvial aquifer 

and ISDS areas were significantly higher than those in water 

samples from wells in the Troublesome Formation aquifer and 

non-ISDS areas, as indicated by median manganese concentrations (table 3).

Nutrients and Dissolved Organic Carbon 

Nutrients (nitrogen and phosphorus) can occur in ground 

water as a result of natural and anthropogenic factors. Nitrogen 

is a naturally occurring element in crustal rocks, plants, soil, and 

the atmosphere, whereas phosphorus is common in igneous 

rocks and occurs in mineral form as apatite (Hem, 1992).
14 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Chloride Cl) ANIONS

Carbonate (CO ) + Bicarbonate ( 3

HCO )3

ANIONS

Percent total milliequivalents per liter

Chloride (Cl) Calcium (Ca)

Na+K

CATIONS

No

dominant

type

No

dominant

type

Calcium

type

Sodium

type or

potassium

type

Sulfate

type

Bicarbonate

type

Chloride

type

Magnesium

type

Site 1

Site 2

Site 3

Site 4

Site 5

Site 6

Site 7

Site 8Site 9

Site 10

Site 11

Site 12

Calcium (Ca)

CATIONS

Ca Na+K

Mg

Magnesium (Mg)

Sodium (Na) + Potassium (K) 80 80

80

80

60

60 60

60

40

40

40

40

20

20

20

20

80

80

60

60

40

20

20

SO4

80

80

80

60 60

40 40

20 20

Sulfate (SO4) 40

20

Cl 80 60 40 20

Mg

Ca 50

50

10

10

90 90

SO4

Na+K

50

10

HCO3

50

90 90

50

10

Cl 50

50 50

40

EXPLANATION

Site number (figure 1)

Ground-water sites

Surface-water site

60

Magnesium (Mg)

HCO3 + CO3

Percent total milliequivalents per liter

Sulfate (SO ) + Chloride (Cl) 4

Calcium (Ca) + Magnesium (Mg)

Sulfate (SO ) + Chloride (Cl) 4

Calcium (Ca) + Magnesium (Mg)

Sulfate (SO4)

Carbonate (CO ) + Bicarbo 3

nate (CO )3

Sodium (Na) + Potassium (K)

Ca + Mg

Cl + SO4

Ca + Mg + Na + K

Na + K + Ca + Mg

HCO3 + Cl + SO4

Cl + SO4 + HCO3

HCO3 + CO3

Figure 4. Dissolved major-ion composition of ground- and surface-water samples collected in the Fraser River watershed, 1998–2001.
Water Quality 15

Anthropogenic sources of nitrogen and phosphorus include 

synthetic fertilizers, animal waste, and septic-system effluent. 

Nitrogen also is a by-product of the combustion of fossil fuels. 

Nitrogen and phosphorus are essential nutrients for plant 

growth, but high concentrations of either nutrient in a water 

body can cause unwanted, dense algal blooms. High concentrations of nitrate in drinking water can cause methemoglobinemia 

(blue-baby syndrome) in small children (Hem, 1992). Drinkingwater standards or health advisories have been established for 

ammonia (un-ionized ammonia [NH3] plus ammonium 

[NH4

+]), nitrite, and nitrate (table 2).

Ground-water samples were analyzed for the dissolved 

forms of ammonia (un-ionized ammonia plus ammonium), 

ammonia plus organic nitrogen, nitrite, nitrate, phosphorus, and 

orthophosphate.

Ammonia (un-ionized ammonia plus ammonium) was 

detected in low concentrations in water samples from the 

11 wells (table 2). Most (60 of 70) ammonia concentrations 

were less than 0.01 mg/L (table 5, Appendix I). Ammonia also 

was detected in 32 percent (7 of 22) of the blank samples, primarily at low concentrations (0.002–0.005 mg/L); one sample 

had a concentration of 0.021 mg/L (table 9, Appendix II). The 

presence of ammonia in some blanks indicates that small 

amounts of ammonia were introduced during sampling and(or) 

laboratory analysis in a few samples. Also, variability in 

reported ammonia concentrations was within the concentration 

range of the environmental data, and there was inconsistency in 

the detection of ammonia in replicate-pair samples (table 7, 

Appendix II). Because of these factors, the exact concentration 

of ammonia in the ground-water samples collected during the 

sampling period is uncertain. It is known, however, that only 

small amounts of ammonia were present in the samples, and all 

concentrations were less than or equal to about 0.040 mg/L 

(table 2).

 In surface or ground water, nitrite usually is undetected or 

detected at very low concentrations because it is rapidly converted to nitrate in the presence of oxygen. During this study, 

nitrite concentrations were undetected or were less than or equal 

to the reporting level of 0.001 mg/L in all ground-water samples 

but one (0.004 mg/L for site 8 on 09/13/2000). Detected concentrations of nitrite were much lower than the USEPA MCL 

for nitrite of 1 mg/L in drinking water (table 2).

Nitrate plus nitrite concentrations in the ground-water 

samples were essentially nitrate, and will be considered as such 

in this report, because of the very low or undetected concentrations of nitrite. Nitrate concentrations in the ground-water samples ranged from less than 0.005 to 4.72 mg/L, with a median 

concentration of 0.208 mg/L (table 2). Most (54 of 70) nitrate 

concentrations were very low, less than 0.3 mg/L. Nitrate 

concentrations for all water samples from site 7, completed in 

the alluvial aquifer in Tabernash, were less than or equal to 

0.008 mg/L. Nitrate in this well probably was denitrified to 

reduced species of nitrogen; reducing conditions for this well 

were indicated by low dissolved-oxygen concentrations and 

elevated iron and manganese concentrations. Nitrate concentrations were elevated (greater than 1 mg/L) in water samples from 

three alluvial aquifer wells (sites 1, 4, and 8). Nitrate concentrations greater than 2 mg/L may indicate nitrate introduced by 

human activities (U.S. Geological Survey, 1999). Nitrate concentrations for all seven water samples from site 8 were above 

2 mg/L, the estimated national background concentration of 

nitrate in ground water (Mueller and Helsel, 1996). These concentrations may indicate that recent land-use practices have 

affected water quality, as water in site 8 has an estimated chlorofluorocarbon recharge date of the 1990’s (table 1). Results of 

the Wilcoxon rank-sum test indicated that the hypotheses of 

similarities in nitrate concentrations between urban and nonurban areas and between ISDS and non-ISDS areas could not be 

rejected (table 3). Similarities in nitrate concentrations between 

aquifer types also could not be rejected statistically (table 3) 

because of comparable median values, although nitrate concentrations were elevated in water samples from some alluvial 

aquifer wells (fig. 5). No nitrate concentrations were greater 

than the USEPA MCL for nitrate in drinking water of 10 mg/L 

(table II). Variability and uncertainty in nitrate concentrations 

(table 8, Appendix II) had little, if any effect, on the nitrate 

results.

Orthophosphate was the primary component of dissolved 

phosphorus in water from the 11 wells in the study area, as indicated by the similarities in concentrations of the two constituents. For some ground-water samples, the dissolved phosphorus 

concentration was slightly less than the orthophosphate concentration. Small differences in these two constituents may be a 

reflection of analytical precision or variability in phosphorus 

concentrations, as discussed in “Quality-Control Methods and 

Analysis” in Appendix II. Orthophosphate concentrations in the 

ground-water samples ranged from an estimated value of about 

0.005 to 0.137 mg/L, and the median concentration was 

0.047 mg/L (table 2). Minimum concentrations were detected in 

water samples from three alluvial aquifer wells (sites 1, 4, and 

7). All samples for sites 2 and 10, completed in the Troublesome Formation aquifer, had orthophosphate concentrations 

greater than 0.1 mg/L. Orthophosphate concentrations were 

higher in water samples from the Troublesome Formation aquifer and non-ISDS areas than in samples from the alluvial aquifer 

and ISDS areas, as indicated by median concentrations 

(table 3). The most common geologic source of phosphorus is

Figure 5. Distribution of dissolved nitrate concentrations by 

aquifer type for wells in the Fraser River watershed, 1998–2001.

EXPLANATION

0

1

2

3

4

5

Alluvial Troublesome

Formation

NUMBER OF SAMPLES

(39) (24)

DISSOLVED NITRATE,

IN MILLIGRAMS 

PER LITER AS

NITROGEN

AQUIFER TYPE

Outlier

90th percentile

75th percentile

50th percentile (median)

25th percentile

10th percentile
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 indicate 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 groundwater recharge area (Hem, 1992). Anthropogenic sources of 

dissolved organic carbon include organic amendments to soil, 

such as animal manure, and leachate from landfills or septicdisposal systems. The naturally occurring and anthropogenically 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 Troublesome 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 disease (Myers and Sylvester, 1997). Coliform bacteria can be

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 bacteria 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 Troublesome Formation aquifer. All nine samples with detections of 

total coliform bacteria also were analyzed for E. coli, 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 compare 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 wastewater. Most (57 of 69) water samples from the 11 wells did not 

contain detectable concentrations of MBAS, including all samples 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 

Figure 6. Distribution of dissolved organic carbon concentrations by presence or absence of individual septic disposal 

systems for wells in the Fraser River watershed, 1998–2001.

EXPLANATION

(31) (39)

NUMBER OF SAMPLES

0

1

2

3

4

5

DSSOLVED ORGANIC CARBON,

IN MILLIGRAMS PER LITER

 AS CARBON

PRESENT ABSENT

Outlier

90th percentile

75th percentile

50th percentile (median)

25th percentile

10th percentile
Water Quality 17

USEPA SDWR for MBAS of 0.5 mg/L (table 2). This exceedance may indicate the local contamination of ground water by 

waste from an ISDS. Detection of anthropogenic surfactants 

probably relates more to the failure of individual ISDS’s rather 

than being representative of the entire ISDS area. Other 

detected concentrations of MBAS were too low to discern 

whether the surfactants were naturally occurring or had an 

anthropogenic source.

Radon is a naturally occurring radioactive gas that is 

formed from the decay of uranium. Major sources of radon 

include rocks containing uranium minerals, soils derived from 

such rocks, and ground water that has been in contact with uranium-bearing rocks and soils. Uranium decays to radium (and 

other products) and then to radon, which is soluble in water and 

occurs in ground water as a gas. Radon can be present in indoor 

air as a result of seepage from soils underneath a building (the 

primary mechanism) or through the use of well water (through 

aeration) that contains radon. The primary public health risk 

associated with radon is the breathing of radon from indoor air 

in homes (U.S. Environmental Protection Agency, 2000b). The 

National Research Council estimated that the radon in indoor 

air resulting from the breakdown of uranium in soils has contributed to about 20,000 lung cancer deaths each year in the 

United States (National Research Council, 1999). Only a small 

portion of radon in indoor air is derived from the aeration of 

radon-containing well water through household use of the 

water. This source can, however, increase a person’s risk of 

lung cancer over a lifetime. Drinking water that contains radon 

presents a risk of internal-organ cancers, particularly stomach 

cancer (U.S. Environmental Protection Agency, 2000b). Radon 

can be removed from well water through the use of carbon 

filters or aeration devices (U.S. Environmental Protection 

Agency, 2000b).

Different isotopes of radon are produced by the decay of 

radium, but only one, radon-222, has environmental importance 

(Hem, 1992). Excluding site 1, which was sampled only in 2000 

and 2001, three of the water samples collected from each well 

in 1998 and 1999 were analyzed for radon-222. Concentrations 

ranged from 365 to 6,380 pCi/L (picocuries per liter), and the 

median concentration was 760 pCi/L (table 2). All concentrations exceeded the USEPA-proposed MCL for radon-222 in 

drinking water of 300 pCi/L (table 2), which is under review. 

When variability and uncertainty in radon-222 concentrations 

were taken into account (table 8, Appendix II), part of the concentration range for one sample was less than the USEPAproposed MCL. Among the 10 wells, water samples from site 4, 

an alluvial aquifer well immediately west of Fraser, had the 

highest median radon-222 concentration (6,170 pCi/L). This 

concentration was more than three times higher than the next 

highest median concentration (fig. 7). All radon-222 concentrations for site 4 were greater than the USEPA-proposed alternative MCL for radon-222 in drinking water of 4,000 pCi/L 

(table 2), which also is under review. Statistically significant 

differences in radon-222 concentrations were not indicated for 

samples from wells completed in the alluvial aquifer and wells 

completed in the Troublesome Formation aquifer (table 3). 

Radon-222 concentrations in ground-water samples from wells 

in the Fraser River watershed were similar to concentrations in 

ground-water samples from wells in other areas of the Upper 

Colorado River Basin in Colorado, which ranged from 305 to 

4,030 pCi/L in 1997 (Apodaca and others, 2000). 

Changes Over Time

For each well except sites 1 and 3, data for field properties 

and water-quality constituents for ground-water samples were 

examined qualitatively for changes over time by using 

LOWESS smooth curves. Insufficient data were available for 

wells 1 and 3 to be included in the analysis. Properties and constituents that were graphed included water temperature, specific 

conductance, dissolved-oxygen concentration, pH, turbidity, 

alkalinity, dissolved solids, major ions (calcium, chloride, 

magnesium, potassium, silica, sodium, and sulfate), manganese, nutrients (nitrate and orthophosphate), and dissolved 

organic carbon. For most constituents from most wells, changes 

in the data over time were not apparent. Changes were apparent, 

however, for samples from site 7, an alluvial aquifer well in the 

Tabernash area. Specific conductance and calcium, magnesium, 

chloride, and sulfate concentrations appeared to increase over 

time (fig. 8). These changes are qualitative changes only and are 

not legitimate statistical trends because of the short time periods 

of the data collection, the small sample sizes, and data collection only occurring in 2 months of each year. The change in specific conductance probably was a function of higher 

concentrations of calcium, magnesium, chloride, and sulfate 

over portions of the sampling period. Calcium and magnesium 

concentrations generally increased between May 1999 and May 

2001, whereas chloride and sulfate concentrations increased 

after May 2000, respectively (fig. 8). The apparent increases in 

specific conductance and calcium, magnesium, chloride, and 

sulfate concentrations for site 7 had little effect on water quality 

of the well, but the changes indicate that shallow ground water 

could be susceptible to changes in land use in the watershed. 

Specific conductance remained moderate, and the water 

remained suitable for use. Chloride and sulfate concentrations 

remained well below the USEPA drinking-water standard of 

250 mg/L for each constituent (table 2). 

Surface Water

As stated previously, field properties for the surfacewater site Fraser River below Crooked Creek at Tabernash 

(hereinafter Fraser River at Tabernash) were measured 

bimonthly between August 1998 and September 2001, and 

water samples were collected for laboratory analyses during 

each site visit. The resulting data for WY’s 1999, 2000, and
18 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

2001 are listed in the annual USGS water-data reports for these 

years (Crowfoot and others, 2000, 2001, and 2002). A statistical 

summary of selected surface-water data for the site, applicable 

State of Colorado instream water-quality standards, and NWQL 

reporting levels are listed in table 4. All water-quality constituents discussed in this section are in the dissolved form except 

for total phosphorus, particulate organic carbon, and fecal 

coliform bacteria.

Field Properties and Suspended Sediment

Discharge in the Fraser River at Tabernash ranged from a 

minimum of 31.0 ft3

/s to a maximum of 244 ft3/s for the sampling period, and the median was 66.2 ft3

/s (table 4). Discharge 

is dominated by snowmelt runoff during spring. Smaller 

discharges at other times of the year reflect the gradual melting 

of annual snowfields, precipitation events (primarily 

Figure 7. Median radon-222 concentrations for wells in the Fraser River watershed, 

1998–99.

Base modified from U.S. Geological Survey 

County map series 1:50,000, 1978

Grand County sheets 2 and 4

Continental

Divide

Colorado

River

Granby

40 ̊

106 ̊ 105 ̊52'30"

105 ̊45'

Fraser

Winter

Park

Tabernash

39 ̊52'30" Moffat Water Tunnel

024

0 2 4 6 KILOMETERS

6 MILES

Vasquez

Water Tunnel

Vasquez Creek

Crooked

Creek

Pole Creek

Hurd Creek

Fraser

River

Ranch

Creek

Tenmile

Creek

Strawberry Creek

EXPLANATION

St. Lou is Creek

9

669

1

2

3

4

5

6

7 8

9

10

11

ND

ND

1,560

1,020

752

669

727 764

523

553

6,170

1,790

Site number

Median radon-222 concentration

No data
Water Quality 19

thunderstorms in summer), base flow from ground-water 

discharges, and discharge from wastewater-treatment facilities. 

Concentrations of suspended sediment in the Fraser River 

at Tabernash were low overall, ranging from 3 to 29 mg/L, 

with a median of 8 mg/L (table 4). Elevated concentrations 

occurred during early spring or during snowmelt runoff. 

Suspended sediment is important in nutrient analysis because a 

large proportion of phosphorus carried by streams tends to 

adhere to the sediment.

Measurements of specific conductance ranged from 74 to 

146 μS/cm (table 4) and indicated slightly mineralized water. 

Minimum specific conductance was detected during times of

Figure 8. (A) Specific conductance and dissolved (B) calcium, (C) magnesium, (D) chloride, and (E) sulfate concentrations over time for well 7 in the 

Fraser River watershed, 1998–2001.

300

320

340

360

380

400

40

50

60

70

4.0

4.5

5.0

5.5

6.0

4

6

8

10

01/01/1999 01/01/2000 01/01/2001 01/01/2002

6

8

10

12

14

TIME

B

C 

D

E

DISSOLVED

SULFATE, IN

MILLIGRAMS 

PER LITER

DISSOLVED

CHLORIDE, IN

MILLIGRAMS 

PER LITER

DISSOLVED 

MAGNESIUM, IN

MILLIGRAMS 

PER LITER

DISSOLVED

CALCIUM, IN

MILLIGRAMS 

PER LITER

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS 

PER CENTIMETER 

AT 25 DEGREES 

CELSIUS

A
20 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 4. Statistical summary of selected field properties and water-quality constituents for surface water at the Fraser River below Crooked Creek at Tabernash, Colorado, 1998– 2001. [All water-quality constituents are in the dissolved form except for total phosphorus, particulate organic carbon, and fecal coliform bacteria. Water-quality standards are from Colorado Department of Public Health and Environment (2002). WY, water year; MRL, minimum reporting level; LT-MDL, long-term method detection level; LRL, laboratory reporting level; ft3/s, cubic feet per second; --, no standard established; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; μg/L, micrograms per liter; N, nitrogen; <, less than; nitrate is nitrate plus nitrite; P, phosphorus; C, carbon; col/100 mL, colonies per 100 milliliters; E, estimated] Field properties, constituents, and reporting units Number of samples Minimum Median Maximum State of Colorado water-quality standard WY 1998 WY 1999 WY 2000 WY 2001 MRL LT-MDL LRL (*=MRL) LT-MDL LRL (*=MRL) LT-MDL LRL (*=MRL) Field properties and suspended sediment Discharge (ft3/s) 24 31.0 66.2 244 -- Suspended sediment (mg/L) 16 3 8 29 -- Specific conductance (μS/cm) 23 74 108 146 -- 1.0 *1.0 *1.0 *1.0 Oxygen, dissolved (mg/L) 24 8.0 9.6 11.5 16.0, 7.0 0.1 *0.1 *0.1 *0.1 pH (standard units) 24 7.8 8.3 8.6 6.5–9.0 0.1 *0.1 *0.1 *0.1 Dissolved solids, major ions, and trace elements Dissolved solids (mg/L) 17 53 70 93 -- Computed concentration2 Chloride (mg/L) 24 2.2 3.9 9.0 250 0.1 *0.1 0.14 0.29 0.04 0.08 Sulfate (mg/L) 19 1.1 2.7 4.5 250 0.1 *0.1 0.15 0.31 0.05 0.11 Iron (μg/L) 19 73 198 354 300 (chronic) 10 5 10 5 10 5 10 Manganese (μg/L) 19 14 26 53 50 (chronic) 4 1.5 3 1.1 2.2 1.6 3.2 Nutrients and organic carbon Ammonia,3 as N (mg/L) 24 <0.002 0.015 0.412 -- 0.002 *0.002 *0.002 *0.002 Un-ionized ammonia,4 as N (mg/L) 24 2.6×10-5 7.4×10-5 0.004 0.02 (chronic) Computed concentration4 Nitrite, as N (mg/L) 24 0.001 0.005 0.01 0.05 0.001 *0.001 *0.001 *0.001 Nitrate, as N (mg/L) 24 0.012 0.062 0.703 10 0.005 *0.005 *0.005 *0.005 Total phosphorus, as P (mg/L) 24 0.032 0.058 0.173 -- 0.004 *0.004 0.003 0.006 0.003 0.006 Phosphorus, as P (mg/L) 24 0.015 0.030 0.084 -- 0.004 *0.004 0.003 0.006 0.003 0.006 Orthophosphate, as P (mg/L) 24 0.011 0.024 0.077 -- 0.001 *0.001 *0.001 0.004 0.007 Dissolved organic carbon, as C (mg/L) 19 1.6 3.3 6.3 -- 0.1 *0.1 0.16 0.33 0.16 0.33 Particulate organic carbon, as C (mg/L) 18 <0.2 0.3 0.7 -- Fecal coliform bacteria Fecal coliform bacteria (col/100 mL) 23 <1 E 7 129 200 (geometric mean)

1 *1 *1 *1

1Water-quality standard is a minimum of 6.0 mg/L except during periods of fish spawning when it is a minimum of 7.0 mg/L. 2Dissolved solids (sum of constituents) is computed as the sum of calcium, magnesium, sodium, potassium, silica, chloride, sulfate, and carbon (as carbonate equivalent) plus any other constituents, such as 

dissolved iron, if they are present in the water. 3Un-ionized ammonia [NH3] plus ammonium [NH4

+]. 4NH3.
Water Quality 21

maximum discharge and is an indication of dilution of surface 

water with snowmelt. Maximum values occurred during late 

winter and early spring before the onset of snowmelt.

Dissolved-oxygen concentrations in the Fraser River at 

Tabernash ranged from 8.0 to 11.5 mg/L, with a median of 

9.6 mg/L (table 4). Dissolved-oxygen concentrations were 

inversely related to stream temperature, which is a primary 

factor controlling the solubility of oxygen in water. The State of 

Colorado instream water-quality standard for dissolved-oxygen 

concentration in the Fraser River is 6.0 mg/L except during 

periods of fish spawning when the standard is raised to 

7.0 mg/L (table 4) (Colorado Department of Public Health and 

Environment, 2002). No dissolved-oxygen concentrations measured during this study were less than the standard.

Values for pH in the Fraser River ranged from 7.8 to 8.6 

(table 4). All measurements were within the State instream 

water-quality standard of 6.5–9.0 (Colorado Department of 

Public Health and Environment, 2002). 

Dissolved Solids, Major Ions, and Trace Elements

The concentrations of dissolved solids in the Fraser River 

were low, ranging from 53 to 93 mg/L (table 4). These concentrations reflected the high quality of the surface water and 

indicate the suitability of the water for drinking, residential, 

industrial, and irrigation purposes.

The surface water was a calcium-bicarbonate type water 

throughout the study period (fig. 4). Samples from 10 of 

11 ground-water wells were the same type water. During most 

of the year, the surface water primarily is base flow from 

ground-water discharge. The following discussion will only 

focus on the major ions chloride and sulfate and the trace elements iron and manganese, all of which have State of Colorado 

instream water-quality standards.

Chloride concentrations overall were low (less than or 

equal to 9.0 mg/L) in the Fraser River at Tabernash (table 4). 

Maximum concentrations typically occurred during late winter 

or early spring just prior to peak flow resulting from spring 

snowmelt. Minimum concentrations occurred during snowmelt 

runoff (fig. 9). It is likely that chloride in the river comes from 

nonpoint sources, including salt and gravel applications during 

winter, and discharges from wastewater-treatment facilities. All 

chloride concentrations were substantially below the State 

instream standard of 250 mg/L (Colorado Department of Public 

Health and Environment, 2002).

Sulfate concentrations also were low (less than or equal to 

4.5 mg/L) in the river. Like chloride, maximum concentrations 

of sulfate typically occurred during late winter or early spring 

just prior to peak flow resulting from spring snowmelt; minimum concentrations occurred after snowmelt runoff in midsummer (fig. 9). All sulfate concentrations were substantially 

below the State instream standard of 250 mg/L (Colorado 

Department of Public Health and Environment, 2002).

Iron concentrations were relatively high at the site, ranging 

from 73 to 354 μg/L with a median concentration of 198 μg/L 

(table 4). The elevated iron concentrations may be related to 

discharges of iron-rich ground water to the river in the vicinity 

of Tabernash. A large amount of variability in the iron concentrations was present over the sampling period, but no seasonal 

patterns were discernible. The State chronic instream iron standard of 300 μg/L for the Fraser River site was exceeded in 1 of 

19 samples (Colorado Department of Public Health and Environment, 2002). For trace elements such as iron and manganese, 

compliance with the State instream standard is met if the concentration of the 85th percentile of all representative data is less

Figure 9. Dissolved sulfate and chloride concentrations and discharge at the 

Fraser River below Crooked Creek at Tabernash, Colorado, 1998–2001.

0

2

4

6

8

10

12

DISSOLVED SULFATE AND 

CHLORIDE, IN 

MILLIGRAMS PER LITER

DISCHARGE, IN CUBIC 

FEET PER SECOND

0

50

100

150

200

250

300

Dissolved chloride

Dissolved sulfate

Discharge

TIME

08/01/98

11/01/98

02/01/9905/01/9908/01/99

11/01/99

02/01/0005/01/0008/01/00

11/01/00

02/01/0105/01/0108/01/01
22 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

than the standard. For this site, the 85th percentile concentration 

of iron was 275 μg/L. Even though one exceedance did occur, 

the river was in compliance with the iron standard over the sampling period.

Manganese concentrations ranged from 14 to 53 μg/L, and 

the median concentration was 26 μg/L (table 4). Like iron, manganese concentrations were variable over the sampling period, 

and no seasonal patterns were discernible. The State chronic 

instream manganese standard of 50 μg/L was exceeded in 1 of 

19 samples (Colorado Department of Public Health and Environment, 2002). Because the 85th percentile concentration was 

about 37 μg/L for manganese, the Fraser River was in compliance with the stream standard for manganese at this site over the 

sampling period. 

Nutrients and Organic Carbon

Nitrogen and phosphorus constituents that are discussed as 

nutrients include ammonia (un-ionized ammonia plus ammonium), un-ionized ammonia, nitrite, nitrate, total and dissolved 

phosphorus, and orthophosphate. In surface water, these nutrients can both come from natural and anthropogenic sources 

through runoff or the discharge of ground water to surface 

water. Natural sources include nitrogen fixation as a source of 

nitrogen and the mineral apatite as a source of phosphorus. 

Anthropogenic sources of nitrogen are more numerous and 

include the production and use of synthetic fertilizers, atmospheric deposition from the combustion of fossil fuels, animal 

feedlots, and sewage. These latter two sources also are sources 

of phosphorus in surface water. 

There are currently (2003) three wastewater-treatment 

facilities located upstream from the surface-water-sampling site 

that discharge into the Fraser River. The largest nutrient input 

to the Fraser River coincides with a portion of the river near the 

wastewater-treatment facilities (Bails, 2003). State instream 

water-quality standards have been established for un-ionized 

ammonia, nitrite, and nitrate in stream water but not for phosphorus.

Ammonia concentrations at the Fraser River site ranged 

from less than 0.002 to 0.412 mg/L, and the median concentration was 0.015 mg/L (table 4). Ammonia concentrations 

showed a seasonal pattern; maximum concentrations occurred 

during winter and early spring, and minimum concentrations 

occurred during snowmelt runoff and during the summer and 

fall months (fig. 10). Stream standards for ammonia are based 

on un-ionized ammonia (NH3), the form of ammonia most toxic 

to aquatic life. For the Fraser River watershed, the State chronic 

instream standard for un-ionized ammonia is 0.02 mg/L. This is 

a table value standard (TVS) that is constant whereas the acute 

TVS is a function of the pH and temperature of the water (Colorado Department of Public Health and Environment, 2002). 

For each sample, the un-ionized ammonia concentration was 

estimated from the reported ammonia concentration by using 

pH, water temperature, and the equilibrium constant for ammonia protonation (U.S. Geological Survey Office of Water 

Quality Technical Memorandum No. 93.12, 1993, URL 

http://water.usgs.gov/admin/memo/QW/qw93.12.html, 

accessed February 7, 2002). The acute TVS concentration also

Figure 10. Dissolved ammonia and nitrate concentrations and discharge at the 

Fraser River below Crooked Creek at Tabernash, Colorado, 1998–2001.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Dissolved ammonia

Dissolved nitrate

Discharge

TIME

08/01/98

11/01/98

02/01/9905/01/9908/01/99

11/01/99

02/01/0005/01/0008/01/00

11/01/00

02/01/0105/01/0108/01/01

DISCHARGE, IN CUBIC

FEET PER SECOND

DISSOLVED AMMONIA AND NITRATE,

 IN MILLIGRAMS PER 

LITER AS NITROGEN

EXPLANATION

0

50

100

150

200

250

300
Water Quality 23

was calculated for each sample and then compared to the calculated un-ionized ammonia concentration. No surface-water 

sample had an un-ionized ammonia concentration that exceeded 

the chronic standard or the calculated acute TVS for un-ionized 

ammonia. 

In noncontaminated waters, nitrite usually is not detected 

or is detected at low concentrations because it is unstable in the 

presence of oxygenated water and is rapidly converted to 

nitrate. All nitrite concentrations in the Fraser River were less 

than or equal to 0.01 mg/L and met the State instream waterquality standard of 0.05 mg/L (Colorado Department of Public 

Health and Environment, 2002). Nitrate concentrations in the 

river were very low, ranging from 0.012 to 0.703 mg/L 

(table 4). Nitrate concentrations fluctuated with the same 

seasonality as ammonia concentrations (fig. 10). Low nitrate 

concentrations at the beginning of summer resulted from dilution of surface water with snowmelt water. During summer, the 

low concentrations probably reflected the consumption of 

nitrate by stream biota. All nitrate concentrations were well 

below the State instream standard of 10 mg/L (table 4) (Colorado Department of Public Health and Environment, 2002).

Total phosphorus concentrations ranged from 0.032 to 

0.173 mg/L, and the median concentration was 0.058 mg/L 

(table 4). Typically, more than one-half of the total phosphorus 

in the Fraser River was particulate rather than dissolved phosphorus. Most of the dissolved phosphorus that was detected in 

surface-water samples was orthophosphate (fig. 11), the form of 

phosphorus that is most readily used in plant and animal metabolism. Maximum concentrations for all phosphorus species 

occurred in late winter or early spring, and minimum concentrations occurred during snowmelt runoff and, at times, during fall.

All natural waters contain organic carbon (Hem, 1992). 

Sources of organic carbon in surface water include living and 

decaying vegetation and biota, wastewater, and ground water. 

Organic carbon is important in surface water as a nutrient for 

microbiota that mediate chemical processes (Hem, 1992), and it 

can increase the solubility or transport of hydrophobic organic 

chemicals such as pesticides. Most organic carbon in the Fraser 

River at Tabernash was dissolved organic carbon. Concentrations of dissolved organic carbon ranged from 1.6 to 6.3 mg/L 

(table 4). The median concentration of 3.3 mg/L was similar to 

the national average of 3.0 mg/L for semiarid regions (Hem, 

1992). Dissolved organic carbon concentrations in the river 

fluctuated seasonally, with maximum concentrations during 

snowmelt runoff and minimum concentrations during winter 

(fig. 12). Particulate organic carbon concentrations ranged from 

less than 0.2 to 0.7 mg/L (table 4). Two of the three highest 

concentrations occurred during spring at the onset of snowmelt 

runoff, and then concentrations decreased during the runoff 

period (fig. 12). The timing of these peak concentrations of 

dissolved and particulate organic carbon indicates that the concentrations are likely derived from decaying vegetation and 

organic detritus transported from the landscape during snowmelt runoff.

Fecal Coliform Bacteria

Fecal coliform bacteria are an indication of the sanitary 

quality of the surface water and the potential for adverse 

human-health effects. The Fraser River is classified as a class 1 

recreation river, which allows for primary contact with the 

water in such activities as swimming, kayaking, and rafting

Figure 11. Phosphorus concentrations and discharge at the Fraser River below 

Crooked Creek at Tabernash, Colorado, 1998–2001.

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0 0

50

100

150

200

250

300

Dissolved phosphorus

Orthophosphate

Total phosphorus

Discharge

TIME

08/01/98

11/01/98

02/01/9905/01/9908/01/99

11/01/99

02/01/0005/01/0008/01/00

11/01/00

02/01/0105/01/0108/01/01

DISSOLVED PHOSPHORUS, 

ORTHOPHOSPHATE, AND TOTAL 

PHOSPHORUS CONCENTRATION, IN 

MILLIGRAMS PER LITER 

AS PHOSPHORUS

DISCHARGE, IN CUBIC

FEET PER SECOND
24 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

where the ingestion of small amounts of water may occur (Colorado Department of Public Health and Environmental, 2002). 

Under this classification, the geometric mean of all data for 

fecal coliform bacteria must be less than 200 col/100 mL. The 

geometric mean of the fecal coliform samples collected for this 

report was 7.4 col/100 mL, well below the State instream standard. The maximum fecal coliform bacteria concentration was 

129 col/100 mL (table 4). Fecal coliform bacteria concentrations showed a seasonal pattern, with maximum concentrations 

occurring in summer and lower concentrations throughout the 

rest of the year (fig. 13). Maximum concentrations in summer 

potentially could be of future concern, as most recreational uses 

of the river would be expected to take place during that time. 

The most likely sources of fecal coliform bacteria in the Fraser 

River are the wastewater-treatment facilities and domestic and 

wild animals.

Ground-Water Quantity

The assessment of ground-water quantity for the Fraser 

River watershed focused on the upper portion of the watershed 

where the majority of development is occurring. The alluvial 

aquifer and Troublesome Formation aquifer are the primary 

sources of ground water for domestic and municipal use in the 

Fraser River valley. The alluvial aquifer in the upper Fraser

Figure 12. Organic carbon concentrations and discharge at the Fraser River below 

Crooked Creek at Tabernash, Colorado, 1998–2001.

Figure 13. Fecal coliform bacteria concentrations and discharge at the

Fraser River below Crooked Creek at Tabernash, Colorado, 1998–2001.

0

1

2

3

4

5

6

7

0

50

100

150

200

250

300

Dissolved organic carbon

Particulate organic carbon

Discharge

TIME

08/01/98

11/01/98

02/01/9905/01/9908/01/99

11/01/99

02/01/0005/01/0008/01/00

11/01/00

02/01/0105/01/0108/01/01

DISSOLVED AND 

PARTICULATE 

ORGANIC CARBON

CONCENTRATION, IN 

MILLIGRAMS PER LITER 

AS CARBON

DISCHARGE, IN CUBIC

FEET PER SECOND

0

20

40

60

80

100

120

140

0

50

100

150

200

250

300

Fecal coliform bacteria

Discharge

08/01/98

11/01/98

02/01/9905/01/9908/01/99

11/01/99

02/01/0005/01/0008/01/00

11/01/00

02/01/0105/01/0108/01/01

TIME

DISCHARGE, IN CUBIC

FEET PER SECOND

FECAL COLIFORM BACTERIA,

IN COLONIES PER 

100 MILLILITERS
Ground-Water Quantity 25

River watershed consists of unconsolidated, poorly sorted, 

valley-fill deposits that range in thickness from a few feet along 

the valley walls up to at least 140 ft in the valley center. The 

Troublesome Formation aquifer consists primarily of siltstone 

with interbedded sandstone and conglomerate, with a thickness 

of more than 600 ft. Previous estimates of ground-water storage 

in the alluvial and Troublesome Formation aquifers were made 

by Apodaca and Bails (1999).

Ground-water quantity is discussed in terms of aquifer 

properties, water-level measurements, and where appropriate, 

qualitative estimates of ground water available to be withdrawn 

by wells. Aquifer properties were derived from lithologic welllog data, from results of available aquifer tests (Resource Engineering, Incorporated, 1999 and 2000; Wilson, 1965), and from 

comparison to aquifer properties of similar systems. In addition, 

two downhole monitors were installed in wells completed 

in the alluvial and Troublesome Formation aquifers to measure 

water level and temperature. The monitors were installed in 

September of 1998 and continuously collected data until midSeptember 2001.

The quantity of available water in the alluvial aquifer is a 

function of the areal extent of the aquifer, the saturated thickness of the aquifer, and the effective porosity (specific yield) of 

water in the saturated zone. The extent of the alluvial aquifer 

overlying the Troublesome Formation was determined from a 

geographic information system (GIS) coverage of the Fraser 

River valley geology (Green, 1992; Tweto, 1979). Unconsolidated surficial deposits of Quaternary age were aggregated, and 

a total areal extent of 22 mi2 was calculated (fig. 14). Information from well logs obtained from the Colorado Division of 

Water Resources indicates the maximum alluvial aquifer depth 

of at least 140 ft in the area of interest upstream from Tabernash. Data collected from the continuous water-level monitor in 

the alluvial aquifer at site 9 indicated the average depth to water 

over the period of study was 8.5 ft below land surface with a 

minimum of 5.9 ft and a maximum of 9.5 ft below land surface 

(fig. 15). The minimum depth to water occurred during early 

spring as snowmelt recharged the alluvial aquifer. The maximum depth to water occurred during the fall and winter as discharge of ground water to surface water exceeded recharge, 

causing the water table to decline. 

To determine the volume of the saturated alluvial aquifer, 

the volume of the alluvial aquifer above the water table was 

subtracted from the total volume of the alluvial aquifer by using 

a GIS procedure. The total volume of the alluvial aquifer was 

estimated by generating a generalized map of aquifer thickness 

from lithologic logs obtained from the Colorado Division of 

Water Resources for 291 wells (fig. 14). Locations of wells and 

the thickness of the alluvium were plotted on a map of the areal 

extent of the alluvial aquifer. Thickness contour lines of 50 ft 

were then drawn on the map to determine areas where the alluvial aquifer was either 0 to 50 ft thick or 50 to 100 ft thick. A 

100-ft maximum thickness was assumed because of the uncertainties in the limited data. The assumed 100-ft maximum thickness allows for some equalization in the estimate of aquifer volume such that some areas may not reach the full 100-ft depth, 

while in some areas the full depth is at least 140 ft. An additional assumption was made concerning the geometry of the 

bottom of the alluvial aquifer. It was assumed that the bottom is 

not flat but is actually thickest in the center of the valley and 

tapers off toward the edges of the aquifer boundary in a lenslike 

morphology. To account for this, the total volume of the area of 

the 0- to 50-ft thickness was calculated by multiplying the areal 

extent of the aquifer by one-half the maximum thickness, or 

25 ft. For the areas of 50- to 100-ft aquifer thickness, the total 

volume is a combination of the top 50 ft, which would not have 

any effect from the bottom of the aquifer morphology, plus the 

bottom 50 ft, which would be affected by the configuration of 

the bottom of the aquifer. To calculate the total volume, the 

areal extent of the 50- to 100-ft-thick areas was multiplied by 

50 ft to represent the upper part of the aquifer that was unaffected by the lower boundary. This number was then added to 

the same areal extent multiplied by one-half the thickness, or 

25 ft, to represent the bottom one-half of the aquifer where the 

boundary condition was present. This equates to 75 ft multiplied 

by the areal extent in the 50- to 100-ft-thick areas for the alluvial 

aquifer. Saturated thickness of the alluvial aquifer was calculated for minimum, average, and maximum depths to water to 

yield estimates for the seasonal variation in aquifer storage. To 

generate the saturated volume of the alluvial aquifer, the depths 

to water were subtracted from average aquifer thicknesses and 

the differences were multiplied by aquifer area. This approach 

yields a maximum saturated volume of the alluvial aquifer 

equal to about 3.33 × 1010 ft3, an average saturated volume of 

3.17 × 1010 ft3, and a minimum saturated volume of 3.11 × 1010

ft3

. These values result in a seasonal change in saturated volume 

of the alluvial aquifer of about 7 percent during the 2 years of 

available data.

Alluvial aquifer testing in the Fraser River Basin conducted by the USGS in 1960 (Wilson, 1965) indicated a coefficient of transmissivity of 12,000 gpd/ft (gallons per day per 

foot) or a hydraulic conductivity of 114 ft/d (feet per day), 

which is in the range of well-sorted sands or glacial outwash 

(Fetter, 1994). Common specific yields (effective porosity) for 

aquifers of this type range from 0.19 to 0.27 (Fetter, 1994). 

Assuming a specific yield of 0.2, the amount of available water 

in the alluvial aquifer at average saturated volume is estimated 

to be about 150,000 acre-ft. Seasonal fluctuations in water level 

indicate that recharge occurs fairly rapidly and that water discharged from the alluvial aquifer is replenished during spring 

snowmelt. Determination of sustainable yields from the alluvial 

aquifer would require more information regarding the amount 

of recharge, regional flow, amount of discharge, and the locations and pumping rates of proposed water-supply wells.

The Troublesome Formation aquifer in the Fraser River 

watershed encompasses an area of about 52 mi2

 upstream from 

Tabernash (fig. 3). Aquifer testing of the Troublesome Formation (Resource Engineering, Incorporated, 1999 and 2000) indi-
26 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

cates that the formation acts as a confined aquifer with little or 

no hydrologic communication with the alluvial aquifer. Lithologic logs of wells installed in the area were obtained from the 

Colorado Division of Water Resources and were tabulated to 

infer physical properties of the Troublesome Formation aquifer. 

Lithologic logs were examined for 162 wells drilled from 80 to 

600 ft below land surface, which were either completed in or 

drilled through the Troublesome Formation. Well depth, overburden thickness, total thickness of water-bearing units, and 

total thickness of nonwater-bearing units in the Troublesome 

Formation aquifer were tabulated from the logs. Wells were 

grouped by township-range-section location, and results were 

averaged for each section that overlies the Troublesome Formation. A maximum of 16 well logs was used to characterize the 

Troublesome Formation aquifer in each section. Some sections 

had no wells completed in the Troublesome Formation. Further

Figure 14. Extent and depth of the alluvial aquifer in the upper Fraser River watershed.

0

0 1 2 KILOMETERS

1 2 MILES

EXPLANATION

50-foot aquifer depth contour line

Aquifer thickness = 0 to 50 feet

Aquifer thickness = 50 to 100 feet

Well locations from Colorado Division of 

 Water Resources

Winter

Park

Granby

Tabernash

Fraser

Troublesome

Formation
Ground-Water Quantity 27

refinement of the well-log selection in sections with a large 

number of available well logs included preference to wells of at 

least 200 ft in depth and wells that were drilled through the 

Troublesome Formation. Tabulated measurements then were 

summarized to give average percentages of water-bearing units 

compared to nonwater-bearing units per section. Total average 

percentages of water-bearing compared to nonwater-bearing 

units then were calculated from the section averages. This 

method was used to give an equally weighted spatial representation of the Troublesome Formation aquifer properties. To estimate the available water in the Troublesome Formation, a total 

Troublesome Formation aquifer thickness of 500 ft was 

assumed. Though the aquifer is thicker than 500 ft in some parts 

of the area, 500 ft was selected as a reasonable maximum depth 

for a water-production well. Wells drilled in the Troublesome 

Formation where aquifer testing was done were completed to 

depths less than 300 ft, except for one well completed to 535 ft, 

and had sufficient yield for community-supply wells (Resource 

Engineering, Incorporated, 1999 and 2000).

Results of tabulation of well data indicate that the average 

percentage of water-bearing units in the upper 500 ft of the 

Troublesome Formation aquifer is 11 percent, with average 

values for each section ranging from 2 to 35 percent. For a 

water-storage calculation of the upper 500 ft of the Troublesome Formation, this equates to an average of 55 ft of saturated 

thickness. Because the Troublesome Formation is a confined 

aquifer, water does not drain from the aquifer as in unconfined 

aquifers but is released due to compression of pore spaces and 

the elasticity of the aquifer itself. The total volume of water 

stored in the Troublesome Formation aquifer is the sum of the 

water released from elastic compression of the aquifer (water 

under pressure) and the amount that would be released from the 

pore spaces of the saturated thickness of the aquifer under 

unconfined conditions as the potentiometric surface drops 

below the upper limit of the confined aquifer (that is, aquifer 

dewatering). Because the Troublesome Formation is a series of 

siltstone and interbedded sandstone and conglomerate and little 

reliable information is available on the depth to the water-bearing units as well as the aquifer’s response to dewatering, the 

amount of water released from elastic compression was not calculated. An average specific yield for unconfined sedimentary 

deposits similar to the water-producing zones of the Troublesome Formation give an approximate value of 0.2 (Fetter, 

1994). The volume of the saturated thickness of the Troublesome Formation is calculated as the areal extent of the aquifer 

times the saturated thickness. This calculation yields a saturated 

aquifer volume of 7.98 × 1010 ft3

. This volume multiplied by the 

specific yield of 0.2 results in an amount of stored water equal 

to approximately 370,000 acre-ft, which would be available if 

the water table dropped below the top of the aquifer and the 

aquifer became unconfined. The total amount of available water 

in the Troublesome Formation might be greater than 370,000 

acre-ft because the amount of water under pressure has not been 

accounted for in the estimate. However, if the specific yield is 

only 0.1 rather than 0.2, then the amount of available ground 

water would be one-half of the calculated estimate.

Results from five aquifer tests completed in the Troublesome Formation (Resource Engineering, Incorporated, 1999 

and 2000) indicate that the average value for coefficient of 

transmissivity for the Troublesome Formation is approximately 

5,000 gpd/ft. When combined with the information on the average saturated thickness of the Troublesome Formation, hydrologic conductivity of the water-bearing units is estimated to be 

about of 12 ft/d, which is in the range of aquifers consisting of 

silty to fine sands (Fetter, 1994). Because the testing of the 

Troublesome Formation aquifer was completed without collecting drawdown data from nearby reference wells, the storage 

coefficient could not be determined.

In order to better estimate maximum potential withdrawals 

of water from the Troublesome Formation (that would not cause 

Figure 15. Ground-water level and temperature in the alluvial aquifer 

(site 9) in the upper Fraser River watershed, 1998–2001.

0

1

2

3

4

5

6

7

8

9

Water level

Temperature

0

1

2

3

4

5

6

7

8

9

10

08/01/98

11/01/98

02/01/9905/01/9908/01/99

11/01/99

02/01/0005/01/0008/01/00

11/01/00

02/01/0105/01/0108/01/01

TIME

DEPTH TO WATER, IN

FEET BELOW LAND SURFACE

WATER TEMPERATURE,

IN DEGREES CELSIUS
28 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

dewatering, or damage to the aquifer), more information would 

be needed on recharge and discharge rates along with a more 

precise understanding of aquifer properties. The estimate of the 

amount of water currently available within the Troublesome 

Formation discussed in this section is not representative of the 

true full potential yield of the aquifer. Factors that will affect the 

yield of the aquifer include recharge rate, regional ground-water 

flow, discharge rate, specific storage of the aquifer, and location 

and pumping rates of proposed water-supply wells. The use of 

ground-water-flow modeling combined with more comprehensive aquifer testing would be necessary to refine estimates of 

future water availability.

Summary

Increasing urban development, as well as the seasonal 

influx of tourists, is placing more demands on the water 

resources in the Fraser River watershed. The U.S. Geological 

Survey, in cooperation with the Grand County Board of County 

Commissioners, conducted an assessment of ground- and 

surface-water quality and ground-water quantity in the Fraser 

River watershed, Grand County, Colorado. Eleven wells were 

sampled semiannually from August 1998 through September 

2001. The data were related to aquifer type (alluvial, Troublesome Formation), land use (urban, nonurban), and presence or 

absence of individual septic disposal systems. One surfacewater site, Fraser River below Crooked Creek at Tabernash, 

Colorado, was sampled bimonthly. This site represents the 

cumulative effects of natural and human factors that affect 

surface-water quality in the Fraser River watershed upstream 

from the town of Tabernash. Ground-water-quantity estimates 

were made for the surficial alluvial aquifer and the Troublesome Formation aquifer.

 The ground water primarily was a calcium-bicarbonate 

type water. Except for elevated radon-222 activities, no widespread ground-water-quality problems in the watershed were 

indicated. The ground-water data were compared to U.S. Environmental Protection Agency or State of Colorado waterquality standards. In general, ground water in the Fraser River 

watershed is suitable as a source of drinking water and for 

domestic, municipal, industrial, and irrigation purposes. Concentrations of dissolved solids, chloride, fluoride, sulfate, 

nitrite, and nitrate in the ground-water samples were substantially less than their respective drinking-water or water-quality 

standards. Properties and constituents from samples from at 

least one well that did not meet the standards were turbidity, 

iron, manganese, methylene blue active substances, and 

radon-222. The constituent of most concern is radon-222. All 

radon-222 concentrations for every well sample exceeded the 

U.S. Environmental Protection Agency proposed drinkingwater standard of 300 pCi/L, which is currently (2003) under 

review.

Results of the two-tailed Wilcoxon rank-sum tests indicated that there were statistically significant differences 

(p-value ≤0.05) in values or concentrations of some field properties and water-quality constituents between aquifer type (alluvium, Troublesome Formation), land use (urban, nonurban), 

and areas with or without individual septic disposal systems. 

Chloride, magnesium, and sulfate concentrations were 

significantly higher in the alluvial aquifer, urban areas, and 

areas with the septic systems. Orthophosphate concentrations 

were significantly higher in the Troublesome Formation aquifer 

and in areas without individual septic disposal systems. Dissolved organic carbon concentrations were significantly higher 

in the alluvial aquifer and areas without individual septic disposal systems than in the Troublesome Formation aquifer and 

areas with individual septic disposal systems, although these 

concentration differences likely had no environmental significance.

An examination of changes in ground-water-quality data 

over time revealed that changes were apparent only for one of 

nine wells examined. For this well, specific conductance 

appeared to increase over time, probably due to increasing concentrations of calcium, magnesium, chloride, and sulfate during 

parts of the sampling period. 

Surface water collected at the Fraser River below Crooked 

Creek at Tabernash from August 1998 through September 2001 

also was a calcium-bicarbonate type water and had low concentrations of dissolved solids. Water quality at this site generally 

was good and indicated the suitability of the water for drinking, 

residential, industrial, and irrigation purposes. All pH values 

and concentrations of dissolved oxygen, chloride, sulfate, iron, 

manganese, un-ionized ammonia, nitrite, nitrate, and fecal 

coliform bacteria met State of Colorado instream water-quality 

standards.

Concentrations of most constituents in the Fraser River 

varied seasonally. Maximum values of specific conductance 

and maximum concentrations of chloride, sulfate, ammonia, 

nitrate, and all phosphorus species typically occurred during 

winter or early spring when discharge was minimal and when 

local wastewater-treatment facilities were near maximum discharge. Minimum values or concentrations of all constituents 

except sulfate generally occurred during snowmelt runoff, indicating the dilution of the surface water with snowmelt. Minimum sulfate concentrations were detected during midsummer 

after snowmelt runoff. Ammonia and nitrate concentrations 

also were at a minimum during summer and fall, with low 

nitrate concentrations probably occurring because of consumption by instream biota. Maximum concentrations of suspended 

sediment occurred during early spring or during snowmelt runoff, and maximum concentrations of dissolved organic carbon 

occurred during snowmelt runoff. Concentrations of fecal 

coliform bacteria peaked during summer but remained below 

the State of Colorado instream standard for the Fraser River. 

Estimates of ground-water quantity in the upper Fraser 

River watershed were made for the surficial alluvial aquifer and 

the Troublesome Formation aquifer, the primary sources of 

ground water for domestic and municipal use in the valley. Calculations of the saturated volume of the alluvial aquifer were 

made for minimum, average, and maximum potentiometric sur-
References Cited 29

face conditions and show a seasonal variance in saturated 

volume of about 7 percent. A ground-water reserve estimate 

was made for average potentiometric surface conditions and is 

a function of the volume of saturated aquifer and the specific 

yield of aquifer material. This calculation yields an average of 

150,000 acre-ft of available stored water in the alluvial aquifer. 

Calculations of water available in the upper 500 ft of the Troublesome Formation were made by assuming an average thickness of water-bearing units equal to 11 percent (55 feet) and a 

specific yield of 0.2, which is typical of an aquifer similar to the 

water-bearing units of the Troublesome Formation. These numbers yield an estimate of available ground water (stored water) 

of about 370,000 acre-ft within the Troublesome Formation 

aquifer in the upper portion of the Fraser River watershed. This 

reserve represents the amount of available water if the aquifer 

became unconfined. Information is not available to estimate the 

fraction of this water reserve that can be withdrawn without 

dewatering, or damaging, the aquifer.

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Appendixes
32 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001
APPENDIXES 33

Appendix I

Selected ground-water-quality data for wells in 

the Fraser River watershed, 1998–2001
34 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001
APPENDIXES 35

Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.[All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey 

National Water Information System (NWIS) data base]

Date Time

Water

temperature 

(°C)

(00010)

Specific 

conductance

(μS/cm)

(00095)

Oxygen, 

dissolved

(mg/L)

(00300)

pH

(standard 

units)

(00400)

Turbidity

(NTU)

(00076)

Alkalinity

(mg/L as 

CaCO3)

(39086)

Bromide

(mg/L)

(71870)

Calcium

(mg/L)

(00915)

Chloride

(mg/L)

(00940)

Fluoride

(mg/L)

(00940)

Iron

(μg/L)

(01046)

Site 1 (395623105481000)

05/16/00 0900 5.1 88 7.0 6.4 4.0 28 <0.01 7.12 4.5 0.2 <1009/11/00 1330 9.8 151 1.2 6.1 6.2 31 0.04 12.1 19.3 0.2 E 805/14/01 1500 5.2 117 10.1 6.3 6.2 35 <0.01 9.52 7.2 0.2 <1009/11/01 1030 9.3 106 3.0 6.3 7.7 27 <0.01 8.00 5.2 0.3 E 5

Site 2 (395658105485400)

08/21/98 0830 6.9 162 0.8 6.5 0.1 79 0.01 21.8 1.7 0.2 <1005/04/99 1230 6.0 164 0.8 6.8 0.3 70 0.01 20.8 2.0 0.1 <1009/01/99 1415 7.7 171 2.1 6.8 0.3 78 <0.01 22.7 5.1 0.1 <1005/18/00 1100 6.5 164 1.1 7.1 0.2 88 0.02 22.4 2.1 0.2 <1009/14/00 1030 7.5 171 1.0 7.2 0.1 79 <0.01 22.7 3.8 0.1 <1005/16/01 1230 6.6 171 0.8 7.0 0.1 77 0.02 23.3 4.8 E 0.1 <1009/12/01 1000 6.9 165 1.0 7.2 0.1 70 <0.01 21.3 5.4 0.2 <10

Site 3 (395642105500700)

08/25/98 0900 6.5 120 7.6 7.2 0.6 60 <0.01 17.0 0.4 0.2 <1005/06/99 1000 5.9 120 5.3 7.2 1.1 64 0.02 17.3 0.8 0.2 <1009/01/99 0830 6.7 117 5.1 7.9 0.1 57 <0.01 16.2 1.0 0.1 <10

Site 4 (395657105495300)

08/26/98 1230 6.0 137 4.2 6.7 0.2 52 0.02 18.0 5.4 <0.1 <1005/06/99 1530 5.4 133 3.9 6.9 2.4 53 0.02 18.3 3.9 <0.1 2009/01/99 1015 6.2 134 5.5 7.0 0.6 57 0.01 18.1 4.4 <0.1 <1005/16/00 1200 5.3 136 5.1 6.8 0.3 55 0.02 18.8 4.8 <0.1 <1009/14/00 1400 6.5 137 4.3 6.9 0.1 55 0.01 18.7 3.8 <0.1 E 805/17/01 1115 5.5 134 4.3 7.3 0.1 59 0.02 19.0 3.5 <0.2 <1009/11/01 1600 6.1 134 4.3 6.9 0.1 53 0.01 17.8 3.8 E 0.1 <10

Site 5 (395750105515800)

08/20/98 1200 14.3 256 6.5 7.8 0.3 140 0.02 43.4 0.5 0.3 <1005/06/99 1230 11.8 259 4.4 7.9 0.2 127 0.01 43.7 0.9 0.3 <1009/01/99 1600 12.7 256 5.7 8.0 0.3 126 <0.01 42.7 1.4 0.3 <1005/16/00 1500 13.9 257 5.4 8.0 0.6 131 0.02 44.3 0.84 0.3 <1009/12/00 1500 13.6 260 4.8 8.1 0.4 130 <0.01 43.5 0.88 0.3 <1005/15/01 1530 13.5 258 5.0 8.1 1.0 129 0.03 45.9 0.88 0.3 <1009/13/01 1500 15.0 260 4.4 8.1 1.3 131 <0.01 42.6 0.92 0.3 <10
36 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Site 6 (395921105472300) 08/27/98 1130 7.7 179 4.4 8.0 0.6 88 <0.01 30.0 0.3 1.4 <10 05/05/99 1330 7.1 225 2.6 8.0 0.3 118 <0.01 35.4 0.8 1.2 20 08/31/99 1300 8.1 227 3.3 7.9 0.3 105 <0.01 38.2 0.6 1.2 30 05/17/00 1430 6.5 237 3.4 8.5 0.2 118 <0.01 40.3 0.9 1.1 <10 09/13/00 1330 8.5 216 3.7 8.1 0.2 106 <0.01 34.7 0.9 1.3 <10 05/16/01 1515 6.6 223 3.3 8.4 0.2 108 <0.01 37.7 0.9 1.2 <10 09/12/01 1400 9.8 199 3.4 8.0 0.6 93 <0.01 29.7 0.6 1.4 <10 Site 7 (395942105502000) 08/18/98 1530 7.0 317 0.1 7.2 0.5 152 0.02 48.7 4.9 0.2 240 05/05/99 0930 4.0 322 0.2 7.2 0.3 142 0.02 47.4 5.7 0.3 260 08/31/99 0830 8.1 321 0.1 7.3 0.4 142 <0.01 51.1 5.0 0.2 210 05/18/00 0830 5.5 331 0.2 7.6 0.6 164 0.02 49.7 5.3 0.2 310 09/13/00 1600 8.1 339 0.2 7.3 0.2 162 <0.01 53.1 6.0 0.2 190 05/17/01 0845 5.6 359 0.2 7.6 0.3 164 0.03 58.1 9.2 0.4 20 09/12/01 1630 7.7 362 0.3 7.6 0.5 161 0.02 54.6 9.4 0.3 100 Site 8 (395937105500500) 08/24/98 1130 7.7 389 5.0 7.8 0.2 143 0.05 51.6 16.4 0.3 <10 05/04/99 1530 6.6 417 1.3 7.5 0.2 138 0.07 57.1 24.7 0.2 <10 08/31/99 1030 8.0 392 1.7 7.6 0.4 130 0.06 55.1 18.9 0.2 <10 05/18/00 1500 6.2 403 2.2 7.6 0.6 140 0.07 54.0 23.8 0.2 <10 09/13/00 0930 8.4 430 1.2 7.5 0.3 139 0.06 60.5 21.3 0.3 <10 05/16/01 0900 6.1 353 1.8 7.7 0.3 135 0.05 50.8 11.3 0.2 <10 09/13/01 0945 8.0 341 1.9 8.0 0.2 143 0.03 46.7 8.7 0.3 <10 Site 9 (395929105510300) 08/19/98 1000 7.3 260 0.5 6.7 1.8 132 0.01 40.1 1.2 0.1 <10 05/03/99 1500 6.3 273 0.5 6.5 1.7 130 0.01 41.0 1.4 0.1 <10 08/30/99 1500 7.4 267 0.6 6.9 2.1 142 <0.01 43.3 1.4 0.1 <10 05/15/00 1500 6.3 256 0.4 6.9 1.0 127 <0.01 38.4 1.6 0.1 <10 09/12/00 0930 7.4 271 0.3 6.8 0.2 133 <0.01 41.7 1.8 0.2 <10 05/15/01 0930 4.8 250 0.7 6.9 0.8 126 <0.01 39.6 3.1 E 0.1 <10 09/10/01 1445 7.2 262 0.6 6.6 -- 125 <0.01 39.0 2.8 E 0.1 <10 Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued [All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, micro- siemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey National Water Information System (NWIS) data base] Date Time Water temperature 

(°C)

(00010)

Specific 

conductance

(μS/cm)

(00095)

Oxygen, 

dissolved

(mg/L)

(00300)

pH

(standard 

units)

(00400)

Turbidity

(NTU)

(00076)

Alkalinity

(mg/L as 

CaCO3)

(39086)

Bromide

(mg/L)

(71870)

Calcium

(mg/L)

(00915)

Chloride

(mg/L)

(00940)

Fluoride

(mg/L)

(00940)

Iron

(μg/L)

(01046)
APPENDIXES 37

Site 10 (395928105533500)

08/20/98 0930 8.0 292 4.7 7.5 0.7 220 0.02 50.5 1.1 0.1 <1005/07/99 0900 7.0 294 5.3 7.6 0.4 146 0.02 49.5 1.6 < 0.1 <1009/02/99 0900 7.3 294 5.6 8.0 0.1 147 0.01 52.8 1.8 < 0.1 <1005/19/00 0830 7.0 294 6.5 8.0 0.1 149 0.03 51.0 1.5 < 0.1 <1009/14/00 0835 7.2 290 5.5 7.9 0.1 147 <0.01 51.0 1.5 0.1 <1005/17/01 1430 7.3 291 4.9 7.8 0.1 143 0.02 52.1 1.8 E 0.1 <1009/13/01 1230 7.9 291 4.5 7.9 0.1 146 <0.01 49.0 2.0 E 0.1 <10

Site 11 (395907105540100)

08/18/98 0900 10.4 310 5.1 7.6 0.1 130 0.03 47.2 1.7 0.2 < 1005/04/99 0900 7.9 317 4.2 6.9 0.2 156 0.03 49.2 1.9 0.2 < 1008/31/99 1445 9.2 317 4.2 7.9 0.2 152 0.02 50.9 3.1 0.2 < 1005/17/00 1000 7.7 322 5.2 7.8 0.1 169 0.03 51.9 2.5 0.2 < 1009/12/00 1230 10.0 324 3.9 7.8 0.1 167 0.03 50.6 2.7 0.2 < 1005/15/01 1300 8.0 324 5.9 7.8 0.1 162 0.03 52.3 3.0 0.2 < 1009/11/01 1345 10.5 322 4.4 7.7 0.4 160 0.02 49.6 2.8 0.2 < 10

Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued[All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 

100 milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey 

National Water Information System (NWIS) data base]

Date Time

Water

temperature 

(°C)

(00010)

Specific 

conductance

(μS/cm)

(00095)

Oxygen, 

dissolved

(mg/L)

(00300)

pH

(standard 

units)

(00400)

Turbidity

(NTU)

(00076)

Alkalinity

(mg/L as 

CaCO3)

(39086)

Bromide

(mg/L)

(71870)

Calcium

(mg/L)

(00915)

Chloride

(mg/L)

(00940)

Fluoride

(mg/L)

(00940)

Iron

(μg/L)

(01046)
38 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued [All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, micro- siemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey National Water Information System (NWIS) data base] Date Time Magnesium (mg/L) (00925) Manganese

(μg/L)

(01056)

Potassium

(mg/L)

(00935)

Silica

(mg/L)

(000955)

Sodium 

(mg/L)

(000930)

Sulfate 

(mg/L)

(000945)

Dissolved

solids

(mg/L)

(70301)

Ammonia1

(mg/L)

(00608)

Ammonia

plus organic

nitrogen

(mg/L)

(00623)

Nitrite

(mg/L)

(00613)

Nitrate

plus nitrite

(mg/L) 

(00631)

Site 1 (395623105481000)

05/16/00 0900 1.74 <2.2 0.90 13.0 7.4 3.2 55 0.003 0.23 <0.001 1.0909/11/00 1330 2.85 <2.2 1.42 14.1 11.3 7.4 89 <0.002 0.12 <0.001 0.28805/14/01 1500 2.24 <3.0 1.02 12.0 9.3 6.0 76 0.003 0.22 <0.001 1.7309/11/01 1030 1.83 <3.0 1.14 13.3 9.6 9.0 70 <0.002 0.19 0.001 1.11

Site 2 (395658105485400)

08/21/98 0830 3.70 <4.0 1.96 31.9 5.2 3.2 119 <0.002 <0.10 <0.001 0.24505/04/99 1230 3.73 <3.0 1.89 31.9 5.2 3.0 112 0.005 <0.10 <0.001 0.20809/01/99 1415 3.94 <3.0 2.18 34.7 5.4 3.5 126 <0.002 E 0.09 0.001 0.29405/18/00 1100 3.93 <2.2 1.72 33.6 5.1 -- -- <0.002 <0.10 <0.001 0.23309/14/00 1030 3.93 <2.2 1.92 34.5 5.3 3.4 125 0.005 E 0.06 <0.001 0.29205/16/01 1230 3.88 <3.0 1.92 34.4 5.3 4.0 125 0.006 <0.10 <0.001 0.24909/12/01 1000 3.70 <3.0 1.80 35.1 5.4 4.2 120 <0.002 E 0.05 0.001 0.195

Site 3 (395642105500700)

08/25/98 0900 2.05 <4.0 1.75 21.4 4.0 1.7 86 <0.002 <0.10 <0.001 0.21005/06/99 1000 2.14 <3.0 1.47 22.1 3.9 1.4 89 0.006 <0.10 <0.001 0.17709/01/99 0830 2.05 <3.0 1.68 23.3 3.8 2.0 86 <0.002 <0.10 <0.001 0.206

Site 4 (395657105495300)

08/26/98 1230 2.51 <4.0 1.42 22.3 4.1 2.8 92 <0.002 <0.10 <0.001 1.0305/06/99 1530 2.52 E 2.3 1.43 23.7 3.9 2.3 94 0.011 <0.10 0.001 0.87209/01/99 1015 2.52 <3.0 1.54 23.6 4.0 2.6 96 <0.002 <0.10 <0.001 1.1105/16/00 1200 2.64 <2.2 1.30 23.7 4.0 2.6 96 <0.002 <0.10 <0.001 1.2009/14/00 1400 2.52 <2.2 1.44 23.8 4.0 2.5 95 0.004 <0.10 0.001 1.1605/17/01 1115 2.47 <3.0 1.45 23.6 3.8 2.9 96 0.008 <0.10 <0.001 1.0109/11/01 1600 2.44 <3.0 1.39 23.2 3.9 2.8 92 <0.002 <0.10 0.001 1.10

Site 5 (395750105515800)

08/20/98 1200 3.36 <4.0 1.48 22.8 5.4 3.0 165 <0.002 <0.10 <0.001 0.17205/06/99 1230 3.50 <3.0 1.52 23.2 5.2 2.7 158 0.009 <0.10 <0.001 0.14509/01/99 1600 3.40 <3.0 1.56 23.5 5.3 2.8 158 <0.002 0.12 0.001 0.20005/16/00 1500 3.55 2.8 1.36 23.4 5.2 2.7 161 <0.002 <0.10 <0.001 0.18709/12/00 1500 3.43 E 2.0 1.43 23.1 5.2 2.7 160 <0.002 <0.10 <0.001 0.18605/15/01 1530 3.53 E 2.5 1.29 23.1 5.1 3.2 162 <0.002 <0.10 <0.001 0.16909/13/01 1500 3.45 3.9 1.42 22.7 4.9 3.1 159 <0.002 <0.10 <0.001 0.143
APPENDIXES 39

Site 6 (395921105472300)

08/27/98 1130 2.18 <4.0 1.27 21.6 7.0 2.0 119 0.002 <0.10 <0.001 0.01905/05/99 1330 2.58 <3.0 1.25 20.5 6.3 1.9 141 0.009 <0.10 <0.001 0.03408/31/99 1300 2.75 <3.0 1.44 21.4 6.4 2.4 138 0.040 <0.10 <0.001 0.06305/17/00 1430 2.84 <2.2 1.16 20.7 6.5 -- -- <0.002 <0.10 <0.001 0.10909/13/00 1330 2.44 <2.2 1.19 20.3 6.4 2.5 134 <0.002 E 0.06 <0.001 0.05405/16/01 1515 2.59 <3.0 1.15 20.2 6.4 2.9 138 0.007 <0.10 <0.001 0.06209/12/01 1400 2.15 <3.0 1.16 21.6 8.2 2.6 123 <0.002 <0.10 <0.001 0.020

Site 7 (395942105502000)

08/18/98 1530 4.73 436 3.86 39.3 9.0 8.1 211 0.010 0.13 0.001 <0.00505/05/99 0930 4.73 456 3.79 39.4 9.1 7.3 204 0.014 E 0.10 <0.001 <0.00508/31/99 0830 4.97 457 4.10 42.0 9.0 7.9 210 <0.002 E 0.09 <0.001 <0.00505/18/00 0830 4.92 457 4.07 39.0 8.7 7.1 218 <0.002 0.10 <0.001 <0.00509/13/00 1600 5.04 461 3.97 41.2 9.5 7.7 225 0.003 E 0.10 <0.001 <0.00505/17/01 0845 5.45 510 3.88 41.2 9.4 10.5 237 0.024 E 0.08 <0.001 <0.00509/12/01 1630 5.21 375 3.96 40.7 9.2 11.9 232 0.006 E 0.09 0.001 0.008

Site 8 (395937105500500)

08/24/98 1130 4.65 9.4 4.37 38.5 16.3 10.9 249 <0.002 <0.10 <0.001 4.6805/04/99 1530 5.20 8.4 4.66 37.5 16.2 11.4 258 0.024 0.16 0.001 4.0208/31/99 1030 4.98 16.5 4.81 41.4 16.9 11.9 252 <0.002 E 0.06 <0.001 4.3805/18/00 1500 5.01 14.9 4.52 37.3 15.5 10.7 253 <0.002 E 0.06 <0.001 3.9509/13/00 0930 5.34 14.9 4.50 40.1 16.8 16.0 269 <0.002 E 0.10 0.004 4.7205/16/01 0900 4.41 <3.0 3.54 38.2 14.8 12.1 230 0.005 0.12 <0.001 3.1009/13/01 0945 4.17 E 2.3 3.50 40.2 15.4 10.2 227 0.002 <0.10 0.001 2.62

Site 9 (395929105510300)

08/19/98 1000 4.58 167 2.04 32.1 7.3 4.5 173 <0.002 <0.10 <0.001 0.12505/03/99 1500 4.80 130 2.02 32.3 7.4 3.2 171 0.011 E 0.08 -- 0.05908/30/99 1500 4.96 73.8 2.31 35.2 7.5 4.6 185 <0.002 0.11 <0.001 0.08205/15/00 1500 4.48 28.4 2.05 32.9 6.7 4.6 167 0.002 0.11 <0.001 0.08809/12/00 0930 4.73 88.2 2.16 35.0 7.3 3.4 176 <0.002 E 0.08 <0.001 0.08405/15/01 0930 4.39 18.2 1.79 31.5 6.7 3.3 166 0.004 E 0.10 <0.001 0.00809/10/01 1445 4.47 39.6 2.02 34.2 7.2 3.2 168 <0.002 0.12 0.001 0.110

Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued[All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 

100 milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey National Water Information System (NWIS) data base]

Date Time

Magnesium

(mg/L)

(00925)

Manganese

(μg/L)

(01056)

Potassium

(mg/L)

(00935)

Silica

(mg/L)

(000955)

Sodium 

(mg/L)

(000930)

Sulfate 

(mg/L)

(000945)

Dissolved

solids

(mg/L)

(70301)

Ammonia1

(mg/L)

(00608)

Ammonia

plus organic

nitrogen

(mg/L)

(00623)

Nitrite

(mg/L)

(00613)

Nitrate

plus nitrite

(mg/L) 

(00631)
40 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Site 10 (395928105533500) 08/20/98 0930 1.88 <4.0 5.23 38.0 5.7 2.6 238 <0.002 <0.10 <0.001 0.267 05/07/99 0900 1.92 <3.0 4.87 38.4 5.4 2.3 193 0.012 <0.10 <0.001 0.236 09/02/99 0900 1.99 <3.0 5.61 40.3 5.6 2.3 198 <0.005 E 0.08 <0.001 0.292 05/19/00 0830 1.96 <2.2 4.40 38.7 5.1 -- -- <0.002 <0.10 <0.001 0.252 09/14/00 0835 1.90 <2.2 5.07 39.0 5.5 2.4 196 <0.002 <0.10 <0.001 0.277 05/17/01 1430 1.91 <3.0 5.11 39.0 5.3 2.6 195 0.018 <0.10 <0.001 0.221 09/13/01 1230 1.86 <3.0 4.81 38.8 5.6 2.5 192 0.009 <0.10 <0.001 0.227 Site 11 (395907105540100) 08/18/98 0900 1.91 <4.0 6.30 43.5 13.6 1.7 125 0.003 <0.10 <0.001 0.214 05/04/99 0900 1.97 <3.0 6.03 44.1 13.4 1.3 205 0.009 <0.10 0.001 0.206 08/31/99 1445 2.02 <3.0 6.65 45.5 13.2 1.7 215 0.004 <0.10 0.001 0.225 05/17/00 1000 2.04 <2.2 6.00 43.9 12.3 1.6 223 0.003 <0.10 <0.001 0.233 09/12/00 1230 1.97 <2.2 6.15 43.4 12.2 1.7 220 <0.002 <0.10 <0.001 0.235 05/15/01 1300 1.99 <3.0 5.77 43.4 12.1 2.0 219 0.011 E 0.06 <0.001 0.202 09/11/01 1345 1.97 <3.0 5.89 43.7 12.5 1.9 215 0.008 <0.10 <0.001 0.183 Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued [All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, micro- siemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey National Water Information System (NWIS) data base] Date Time Magnesium (mg/L) (00925) Manganese

(μg/L)

(01056)

Potassium

(mg/L)

(00935)

Silica

(mg/L)

(000955)

Sodium 

(mg/L)

(000930)

Sulfate 

(mg/L)

(000945)

Dissolved

solids

(mg/L)

(70301)

Ammonia1

(mg/L)

(00608)

Ammonia

plus organic

nitrogen

(mg/L)

(00623)

Nitrite

(mg/L)

(00613)

Nitrate

plus nitrite

(mg/L) 

(00631)
APPENDIXES 41

Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued[All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 100 

milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey 

National Water Information System (NWIS) data base]

Date Time

Phosphorus

(mg/L)

(00666)

Orthophosphate

mg/L

(00671)

Dissolved

organic carbon

(mg/L)

(00681)

Coliform, 

bacteria, total

(col/100 mL)

(30501)

E. coli

(col/100 mL)

(50278)

Methylene

blue active

substances

(mg/L)

(38260)

Radon-222, 

total

(pCi/L)

(82303)

Site 1 (395623105481000)

05/16/00 0900 0.007 0.007 4.0 40 <1 <0.02 --09/11/00 1330 0.007 0.007 3.0 <1 -- 0.02 --05/14/01 1500 0.007 E 0.005 3.3 E 140 <1 0.02 --09/11/01 1030 0.009 0.007 3.6 <1 -- <0.02 --

Site 2 (395658105485400)

08/21/98 0830 0.123 0.130 0.6 <1 -- <0.02 1,56005/04/99 1230 0.124 0.131 0.5 <1 -- <0.02 1,59009/01/99 1415 0.131 0.136 0.8 <1 -- <0.02 1,39005/18/00 1100 0.128 0.121 0.67 <1 -- <0.02 --09/14/00 1030 0.135 0.125 0.78 <1 -- <0.02 --05/16/01 1230 0.131 0.126 0.68 <1 -- <0.02 --09/12/01 1000 0.136 0.129 0.69 <1 -- <0.02 --

Site 3 (395642105500700)

08/25/98 0900 0.025 0.025 0.3 1 <1 <0.02 1,67005/06/99 1000 0.026 0.026 0.2 <1 -- <0.02 1,79009/01/99 0830 0.026 0.030 0.3 <1 -- <0.02 1,980

Site 4 (395657105495300)

08/26/98 1230 0.015 0.015 0.5 <1 -- <0.02 6,38005/06/99 1530 0.017 0.015 0.3 <1 -- <0.02 6,05009/01/99 1015 0.014 0.016 0.4 <1 -- <0.02 6,17005/16/00 1200 0.017 0.016 0.46 <1 -- <0.02 --09/14/00 1400 0.017 0.016 0.49 <1 -- <0.02 --05/17/01 1115 0.017 0.017 0.35 <1 -- <0.02 --09/11/01 1600 0.016 0.013 0.46 2 <1 <0.02 --

Site 5 (395750105515800)

08/20/98 1200 0.046 0.047 0.5 <1 -- <0.02 55305/06/99 1230 0.055 0.051 0.5 <1 -- <0.02 51109/01/99 1600 0.048 0.049 0.7 <1 -- <0.02 57005/16/00 1500 0.045 0.047 0.60 <1 -- <0.02 --09/12/00 1500 0.048 0.046 0.61 <1 -- <0.02 --05/15/01 1530 0.045 0.041 0.53 <1 -- <0.02 --09/13/01 1500 0.046 0.042 0.72 <1 -- <0.02 --
42 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Site 6 (395921105472300) 08/27/98 1130 0.060 0.061 1.9 <1 -- <0.02 365 05/05/99 1330 0.066 0.066 1.3 4 <1 0.05 556 08/31/99 1300 0.067 0.070 1.4 <1 -- <0.02 523 05/17/00 1430 0.066 0.064 1.4 <1 -- 0.10 -- 09/13/00 1330 0.069 0.066 1.9 1 <1 <0.02 -- 05/16/01 1515 0.066 0.061 1.3 <1 -- 0.02 -- 09/12/01 1400 0.056 0.056 1.7 <1 -- <0.02 -- Site 7 (395942105502000) 08/18/98 1530 0.022 0.018 1.8 <1 -- 0.03 710 05/05/99 0930 0.016 0.017 1.9 <1 -- <0.02 764 08/31/99 0830 0.022 0.017 1.9 <1 -- <0.02 784 05/18/00 0830 0.014 0.024 1.9 <1 -- <0.02 -- 09/13/00 1600 0.029 0.028 2.0 1 <1 0.02 -- 05/17/01 0845 0.023 0.014 1.9 2 <1 0.04 -- 09/12/01 1630 0.028 0.021 1.8 <1 -- <0.02 -- Site 8 (395937105500500) 08/24/98 1130 0.044 0.048 1.1 <1 -- 0.02 727 05/04/99 1530 0.059 0.061 1.1 <1 -- <0.02 801 08/31/99 1030 0.048 0.052 1.1 1 <1 <0.02 710 05/18/00 1500 0.058 0.056 1.4 <1 -- 3.82 -- 09/13/00 0930 0.052 0.049 1.3 <1 -- <0.02 -- 05/16/01 0900 0.050 0.047 1.2 <1 -- <0.02 -- 09/13/01 0945 0.051 0.046 0.98 <1 -- <0.02 -- Site 9 (395929105510300) 08/19/98 1000 0.063 0.060 2.0 <1 -- <0.02 636 05/03/99 1500 0.064 0.060 2.0 <1 -- <0.02 669 08/30/99 1500 0.059 0.062 2.3 <1 -- <0.02 687 05/15/00 1500 0.052 0.052 2.3 <1 -- <0.02 -- 09/12/00 0930 0.060 0.055 2.1 <1 -- <0.02 -- 05/15/01 0930 0.054 0.050 1.9 <1 -- 0.02 -- 09/10/01 1445 0.056 0.050 2.2 <1 -- <0.02 -- Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued [All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, micro- siemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey National Water Information System (NWIS) data base] Date Time Phosphorus (mg/L) (00666) Ortho- phosphate mg/L (00671) Dissolved organic carbon (mg/L) (00681) Coliform, bacteria, total (col/100 mL) (30501) E. coli (col/100 mL) (50278) Methylene blue active substances (mg/L) (38260) Radon-222, total (pCi/L) (82303)
APPENDIXES 43

Site 10 (395928105533500)

08/20/98 0930 0.126 0.131 0.8 <1 -- <0.02 75705/07/99 0900 0.131 0.130 0.8 <1 -- <0.02 75209/02/99 0900 0.134 0.137 1.0 <1 -- <0.02 75205/19/00 0830 0.132 0.126 0.91 <1 -- <0.02 --09/14/00 0835 0.129 0.120 0.90 <1 -- <0.02 --05/17/01 1430 0.124 0.121 0.76 <1 -- <0.02 --09/13/01 1230 0.124 0.122 0.86 <1 -- -- --

Site 11 (395907105540100)

08/18/98 0900 0.032 0.033 0.4 <1 -- <0.02 1,02005/04/99 0900 0.032 0.036 0.5 <1 -- <0.02 99808/31/99 1445 0.033 0.037 0.7 <1 -- <0.02 1,09005/17/00 1000 0.035 0.036 0.74 <1 -- <0.02 --09/12/00 1230 0.038 0.034 1.2 <1 -- <0.02 --05/15/01 1300 0.033 0.032 0.62 <1 -- 0.03 --09/11/01 1345 0.036 0.033 0.80 <1 -- <0.02 --

1Un-ionized ammonia [NH3] plus ammonium [NH4+].

Table 5. Selected ground-water-quality data for wells in the Fraser River watershed, 1998–2001.—Continued[All water-quality constituents are in the dissolved form except for total coliform bacteria, E. coli (Escherichia coli), methylene blue active substances, and radon-222. °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μg/L, micrograms per liter; site number refers to table 1 and figure 1; col/100 mL, colonies per 100 

milliliters; pCi/L, picocuries per liter; <, less than; E, estimated; --, no data. Number in parentheses below the water-quality property or constituent is the data parameter from the U.S. Geological Survey 

National Water Information System (NWIS) data base]

Date Time

Phosphorus

(mg/L)

(00666)

Orthophosphate

mg/L

(00671)

Dissolved

organic carbon

(mg/L)

(00681)

Coliform, 

bacteria, total

(col/100 mL)

(30501)

E. coli

(col/100 mL)

(50278)

Methylene

blue active

substances

(mg/L)

(38260)

Radon-222, 

total

(pCi/L)

(82303)
44 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001
APPENDIXES 45

Appendix II

Quality-Control Methods and Analysis
46 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001
APPENDIXES 47

Quality-Control Methods and Analysis

Quality-assurance and quality-control (hereinafter referred to as QC) samples were used to assess the variability and bias of waterquality data that may be introduced by sample collection, processing, storage, and laboratory analysis. Replicate and field-blank samples 

were collected and processed as QC samples by using the same equipment and procedures as environmental samples. Replicate samples 

for ground water were analyzed for major ions and trace elements, nutrients (nitrogen and phosphorus), dissolved organic carbon, total 

coliform bacteria, MBAS, and radon-222. Blank samples were analyzed for major ions, trace elements, nutrients, and dissolved organic 

carbon (ground-water samples only). Additional information on QC is given in Shelton (1994) and Koterba and others (1995). Ground 

water QC data will be discussed first, followed by surface water QC data.

Replicate samples were used to test for data variability, which is the degree of random error in independent measurements of the same 

quantity. Replicate samples were collected and processed in sequence with environmental samples at a site to yield samples of presumably 

identical composition. By comparing the analytical results of the replicate pair (environmental sample and QC sample), information is 

obtained on the precision of the measured concentration values and consistency in identifying the constituents of interest. 

Replicate samples were first assessed with a unit called the lowest rounding unit, which is the magnitude of the least significant figure 

reported by the USGS NWQL. A nitrate concentration of 0.923 mg/L, for example, would be rounded to the nearest 0.001 mg/L, whereas 

a concentration of 4.73 mg/L would be rounded to the nearest 0.01 mg/L; a lowest rounding unit of 1 would represent 0.001 mg/L for the 

0.923-mg/L sample and 0.01 for the 4.73-mg/L sample. For either sample of a replicate pair, concentrations below the laboratory reporting 

level (less than, or <, concentrations) were given a value of zero for replicate analysis. A replicate pair with estimated (E) concentrations 

was included in the replicate analysis when both the environmental and QC samples had an estimated value but were excluded when only 

one sample of the replicate pair had an estimated value. 

When analysis of lowest rounding unit data identified a constituent with 50 percent or more rounding units above 2, the mean relative 

standard deviation was used to estimate variability and uncertainty in concentration for that constituent. For a given constituent, the relative 

standard deviation was determined for each replicate pair, and then the mean relative standard deviation was computed for the constituent 

to determine variability and uncertainty in concentration. 

For major ions and trace elements, 204 replicate pairs for ground water were evaluated. Values of the lowest rounding unit difference 

ranged between 0 and 197 (tables 6–7, Appendix II). Most replicate pairs for bromide, chloride, fluoride, sodium, sulfate, and iron had a 

lowest rounding unit of 2 or less. These differences probably are well within instrument variation and do not seem to be related to a 

particular constituent concentration. Variability associated with sample collection, processing, storage, and laboratory analysis did not 

appreciably affect the results of environmental data for these constituents. 

Most ground-water replicate pairs for calcium, magnesium, potassium, silica, and manganese had a lowest rounding unit difference 

of 2 or greater (tables 6–7, Appendix II). Variability and uncertainty in concentration values were not determined for calcium, magnesium, 

potassium, and silica because of the small environmental significance of the concentration differences for the respective replicate pairs. 

The maximum dissolved-solids concentration of 269 mg/L in the ground-water samples was below the USEPA SDWR of 500 mg/L 

(table 2). The maximum concentration difference between environmental and QC samples for calcium, magnesium, potassium, and silica 

(constituents of dissolved solids) was 3.0 mg/L for calcium and was insufficient to significantly affect calculated dissolved-solids concentrations. Variability in manganese concentrations, however, may affect the interpretation of environmental data because manganese 

concentrations in some samples exceeded the USEPA SDWR for manganese. Most differences in manganese concentrations in replicate

pairs for sites 7, 8, and 9 were greater than 10 rounding units, whereas concentrations in replicate pairs for other sites varied insignificantly 

(tables 6–7, Appendix II). Variability in manganese concentrations for site 9 was 15.3 percent (±31.8 percent) of the concentration value 

at the 95-percent confidence level (table 8, Appendix II). Variability in manganese concentrations for sites 7 and 8 was not determined 

because of few data (only one replicate pair per well).

For nutrients and dissolved organic carbon, 122 ground-water replicate pairs were evaluated. Lowest rounding unit differences ranged 

from 0 to 137 (tables 6–7, Appendix II). The latter value was an outlier, however, as the next highest difference was 19. Most replicate 

pairs for ammonia plus organic nitrogen, nitrite, orthophosphate, and dissolved organic carbon had lowest rounding unit differences of 2 

or less. Interpretation of environmental data for these constituents was not affected by variability in reported concentrations. Lowest rounding unit differences greater than 2 were most common for ammonia, phosphorus, and nitrate. For ammonia and phosphorus, all differences 

in lowest rounding unit were 6 or less. Interpretation of environmental data for ammonia was affected by the variability in reported concentrations, as the variability was within the concentration range of the environmental data (table 8, Appendix II). Variability in phosphorus 

data did not affect the interpretation of environmental data for phosphorus. For nitrate, some differences in concentrations between the 

environmental and quality-control samples were large, ranging between 12 and 137 lowest rounding unit (tables 6–7, Appendix II). Excluding the replicate pair with the latter value, variability in nitrate concentrations was 1.79 percent (±3.72 percent) of the concentration value 

at the 95-percent confidence level (table 8, Appendix II). However, because the maximum nitrate concentration of 4.72 mg/L in the groundwater samples was well below the USEPA MCL of 10 mg/L (table 2), variability in nitrate concentrations did not affect the interpretation 

of environmental data for nitrate.

All environmental and QC samples for the six ground-water replicate pairs of total coliform bacteria had concentrations less than the 

reporting level of 1 col/100 mL (tables 6–7, Appendix II); therefore, variability in the concentration of total coliform bacteria could not be 

determined. Variability in the concentration of MBAS also could not be determined because most (15 of 18) of the replicate pairs had all 

concentrations below the reporting level (tables 6–7, Appendix II). Differences in radon-222 concentrations in the environmental and QC 

samples ranged between 7 and 78 lowest rounding unit (tables 6–7, Appendix II), which did affect the interpretation of environmental data 
48 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001

for one sample. Variability in radon-222 concentrations was 8.3 percent (±17.3 percent) of the concentration value at the 95-percent 

confidence level (table 8, Appendix II).

Eleven constituents had one or both samples of a replicate pair reported as “less than” concentrations, concentrations undetected at 

the reporting level (table 7, Appendix II). Of these 11, only bromide, ammonia, nitrite, and MBAS had at least one replicate pair with a 

“less than” concentration for one sample and a concentration greater than the reporting level for the other sample, indicating some 

inconsistency in detecting bromide, ammonia, nitrite, and MBAS in the ground-water samples. The most significant of these was for 

ammonia. One-half (four of eight) of the ammonia replicate pairs with a “less than” concentration also had a detected concentration 

(table 7, Appendix II). Most concentrations of bromide, ammonia, nitrite, and MBAS in the ground-water samples were low, near the 

respective reporting levels.

Field-blank samples were used to test for bias, defined as the systematic error inherent in sampling and analytical methods. Blank 

samples were collected using inorganic- and organic-free water that contained no detectable concentrations of the constituents of interest. 

The blank water was processed through the sampling equipment, handled, and analyzed in the same manner as the environmental samples.The ground- and surface-water field blanks were analyzed for major ions, nutrients, trace elements, and dissolved organic carbon, with 

the last two only for ground water. Because constituents in this report were analyzed at low concentrations in the laboratory, field blanks 

were useful in determining possible contamination of a sample from collection, processing, cleaning, storage, and laboratory analysis procedures.

Seventeen field-blank samples for ground water were collected for major-ion and trace-element analysis (table 9, Appendix II). 

Reporting levels for some constituents changed during the 4-year sampling period. In the field blanks, concentrations of chloride, fluoride, 

potassium, silica, sodium, sulfate, and manganese were below the laboratory reporting levels. Bromide and iron were detected at the laboratory reporting levels in one blank sample each. Calcium was detected in three blank samples and magnesium was detected in one blank 

sample above the laboratory reporting levels. Estimated concentrations were reported for three calcium, two magnesium, and five sodium 

blank samples and one blank sample each of sulfate and manganese. The one magnesium detection with a concentration greater than two 

times the lowest rounding unit of the reporting level had no appreciable effect on the reliability of environmental data because of substantially higher magnesium concentrations in environmental samples. Therefore, interpretation of major-ion and trace-element environmental 

data was not affected by detections of major ions and trace elements in the blank samples.

Nineteen field-blank samples for ground water were collected for nutrient and dissolved organic carbon analysis (table 9, 

Appendix II). All constituents except phosphorus were detected in some field-blank samples. Estimated concentrations of ammonia plus 

organic nitrogen and dissolved organic carbon were detected in two and seven blank samples, respectively. Nitrite and nitrate were detected 

at or within one lowest rounding unit of the respective reporting levels. Interpretation of the environmental data for ammonia plus organic 

nitrogen, nitrite, and nitrate in ground water was not affected by detections of these nutrients in blank samples. 

Ammonia was detected in seven blank samples, primarily at or within three times the lowest rounding unit (table 9, Appendix II). 

Blank samples commonly are contaminated with ammonia when exposed to the atmosphere, especially when analyzed at low concentrations—as was done in this study. As discussed above, an inconsistency in the detection of ammonia in ground-water samples was indicated 

by four of eight replicate pairs with a “less than” concentration for one sample and a detected concentration for the other sample. These 

two factors, combined with blank samples having a similar concentration range of ammonia as that of the environmental samples, indicate 

that the exact concentration of ammonia in the ground-water samples collected during this study is not known with certainty. It is known, 

however, that only small amounts of ammonia were present in the samples, and all concentrations were less than or equal to about 

0.04 mg/L. The blank sample with an ammonia detection of 21 times the lowest rounding unit did not affect the interpretation of environmental data because the sample collected prior to the blank did not indicate the presence of ammonia, and subsequent samples were not 

collected during that sampling phase.

Almost all detections of orthophosphate and dissolved organic carbon in blank samples were equal to or within two times the lowest 

rounding unit of the laboratory reporting levels (table 9, Appendix II). Interpretation of orthophosphate and dissolved organic carbon data 

were not affected by detections in blank samples because concentrations in the blank samples were at least one order magnitude smaller 

than concentrations in environmental samples.

Surface-water sample collection at Fraser River below Crooked Creek at Tabernash was done as part of a larger USGS surface-water 

sampling network in the Fraser River watershed. During the August 1998–September 2001 time period, no replicate samples were collected 

on the Fraser River, and no replicate-pair analysis could be performed. Field-blank samples for analysis of major ions and nutrients were 

collected on the Fraser River at four of the network sites, not including the Fraser River site discussed in this report.

For major ions, the blank results indicate that the environmental data for major ions were free of bias during sampling and laboratory 

analysis. Analysis of the three blank samples for dissolved magnesium and sodium indicate no detections. The two dissolved-silica blank 

samples also had no detections. Dissolved calcium was detected in one blank sample at a value five times the laboratory minimum reporting 

level. Interpretation of dissolved-calcium data for surface water was not affected by this blank detection because all values for calcium in 

the environmental surface-water samples were many orders of magnitude higher than the concentration detected in the field blank.

Analysis of the surface-water blank samples for nutrients indicate two detections of ammonia at the reporting level and one detection 

of orthophosphate at one rounding unit above the laboratory reporting level. These detected concentrations are within the expected instrument or method variance, and the interpretation of ammonia and orthophosphate concentrations in surface water was not affected by the 

detections in the blank samples.
APPENDIXES 49

Table 6. Comparison of laboratory results for environmental and quality-control samples for 9 wells in the Fraser River watershed, 1998–2001.[All water-quality constituents are in the dissolved form except for total coliform bacteria, MBAS (methylene blue active substances), and radon-222. no., number; Env., environmental sample; QC, quality-control sample; Conc. diff., difference in concentration between environmental sample and quality-control sample; RU diff., absolute difference in lowest rounding unit; mg/L, milligrams per liter; shaded cells represent differences greater than 1 rounding unit; <, concentration less than the laboratory reporting level; E, estimated; nc, not calculated; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4+]; nitrate is nitrate plus nitrite; --, no data; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter. For calculations, “less than” (<) concentrations are presumed to be zero]

Site no.

(fig. 1;

table 1) 

Date Time

Bromide Calcium Chloride Fluoride

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff. QC QC QC QC

(mg/L) (mg/L) (mg/L) (mg/L)

1 09/11/00 1330

1400

0.040.05

-0.01 1 12.1

12.2

-0.1 1 19.3

18.8

0.5 5 0.2

0.3

-0.1 1

1 05/14/01 1500

1515

<0.01<0.01

0.00 0 9.52

9.55

-0.03 3 7.2

7.3

-0.1 1 0.2

0.2

0.0 0

4 09/14/00 1400

1415

0.010.01

0.00 0 18.7

18.8

-0.1 1 3.8

3.9

-0.1 1 <0.1

<0.1

0.0 0

5 09/13/01 1500

1530

<0.01<0.01

0.00 0 42.6

43.4

-0.8 8 0.9

0.9

0.0 0 0.3

0.3

0.0 0

6 08/27/98 1130

1200

<0.01<0.01

0.00 0 30.0

30.1

-0.1 1 0.3

0.4

-0.1 1 1.4

1.4

0.0 0

7 05/05/99 0930

1000

0.020.02

0.00 0 47.4

50.4

-3.0 30 5.7

5.8

-0.1 1 0.3

0.2

0.1 1

8 09/13/00 0930

1000

0.060.06

0.00 0 60.5

60.7

-0.2 2 21.3

21.2

0.1 1 0.3

0.2

0.1 1

8 05/16/01 0900

0930

0.050.05

0.00 0 50.8

51.5

-0.7 7 11.3

11.6

-0.3 3 0.2

0.2

0.0 0

8 09/13/01 0945

1000

0.030.03

0.00 0 46.7

45.3

1.4 14 8.7

8.5

0.2 2 0.3

0.3

0.0 0

9 05/03/99 1500

1530

0.010.02

-0.01 1 41.0

42.7

-1.7 17 1.4

1.5

-0.1 1 0.1

0.1

0.0 0

9 08/30/99 1500

1530

<0.01<0.01

0.00 0 43.3

43.0

0.3 3 1.4

1.4

0.0 0 0.1

0.1

0.0 0

9 05/15/00 1500

1530

<0.01

0.01

-0.01 1 38.4

40.1

-1.7 17 1.6

1.6

0.0 0 0.1

0.1

0.0 0

9 09/10/01 1445

1515

<0.01<0.01

0.00 0 39.0

38.2

0.8 8 2.8

2.9

-0.1 1 0.1

0.1

0.0 0

10 05/07/99 0900

0915

0.020.02

0.00 0 49.5

51.9

-2.4 24 1.6

1.6

0.0 0 <0.1

<0.1

0.0 0

10 09/02/99 0900

0915

0.010.02

-0.01 1 52.8

52.7

0.1 1 1.8

1.8

0.0 0 <0.1

<0.1

0.0 0

10 05/19/00 0830

0845

0.030.02

0.01 1 51.0

50.1

-0.9 9 1.5

1.5

0.0 0 <0.1

<0.1

0.0 0

10 05/17/01 1430

1500

0.020.03

-0.01 1 52.1

52.2

-0.1 1 1.8

1.8

0.0 0 0.1

0.1

0.0 0

11 08/31/99 1445

1500

0.020.02

0.00 0 50.9

51.3

-0.4 4 3.1

2.1

1.0 10 0.2

0.2

0.0 0

11 05/17/00 1000

1015

0.030.03

0.00 0 51.9

52.0

-0.1 1 2.5

2.5

0.0 0 0.2

0.2

0.0 0
50 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 6. Comparison of laboratory results for environmental and quality-control samples for 9 wells in the Fraser River watershed, 1998–2001.—Continued [All water-quality constituents are in the dissolved form except for total coliform bacteria, MBAS (methylene blue active substances), and radon-222. no., number; Env., environmental sample; QC, quality-control sample; Conc. diff., difference in concentration between environmental sample and quality-control sample; RU diff., absolute difference in lowest rounding unit; mg/L, milligrams per liter; shaded cells represent differences greater than 1 rounding unit; <, concentration less than the laboratory reporting level; E, estimated; nc, not calculated; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4

+]; nitrate is nitrate plus nitrite, --, no data; col/100 mL, colonies per 100 milliliters; pCi/L, 

picocuries per liter. For calculations, ‘less than” (<) concentrations are presumed to be zero]

Site no. 

(fig. 1; 

table 1) 

Date Time

Magnesium Potassium Silica Sodium

Env. Conc. 

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff. QC QC QC QC

(mg/L) (mg/L) (mg/L) (mg/L)

1 09/11/00 1330

1400

2.852.86

-0.01 1 1.42

1.43

-0.01 1 14.1

14.1

0.0 0 11.3

11.3

0.0 0

1 05/14/01 1500

1515

2.242.23

0.01 1 1.02

1.00

0.02 2 12.0

11.9

0.1 1 9.3

9.4

-0.1 1

4 09/14/00 1400

1415

2.522.51

0.01 1 1.44

1.42

0.02 2 23.8

24.1

-0.3 3 4.0

4.0

0.0 0

5 09/13/01 1500

1530

3.453.51

-0.06 6 1.42

1.32

0.10 10 22.7

23.0

-0.3 3 4.9

5.1

-0.2 2

6 08/27/98 1130

1200

2.182.19

-0.01 1 1.27

1.29

-0.02 2 21.6

21.6

0.0 0 7.0

7.1

-0.1 1

7 05/05/99 0930

1000

4.734.94

-0.21 21 3.79

3.72

0.05 5 39.4

40.4

-1.0 10 9.1

9.0

0.1 1

8 09/13/00 0930

1000

5.345.42

-0.08 8 4.50

4.51

-0.01 1 40.1

40.6

-0.5 5 16.8

16.5

0.3 3

8 05/16/01 0900

0930

4.414.45

-0.04 4 3.54

3.88

-0.34 34 38.2

38.1

0.1 1 14.8

14.8

0.0 0

8 09/13/01 0945

1000

4.174.06

0.11 11 3.50

3.66

-0.16 16 40.2

39.8

0.4 4 15.4

14.8

0.6 6

9 05/03/99 1500

1530

4.804.93

-0.13 13 2.02

2.12

-0.10 10 32.3

32.6

-0.3 3 7.4

7.3

0.1 1

9 08/30/99 1500

1530

4.964.94

0.02 2 2.31

2.32

-0.01 1 35.2

34.9

0.3 3 7.5

7.5

0.0 0

9 05/15/00 1500

1530

4.484.63

-0.15 15 2.05

1.90

0.15 15 32.9

33.6

-0.7 7 6.7

7.1

-0.4 4

9 09/10/01 1445

1515

4.474.39

0.08 8 2.02

1.89

0.13 13 34.2

33.8

0.4 4 7.2

7.1

0.1 1

10 05/07/99 0900

0915

1.921.97

-0.05 5 4.87

5.01

-0.14 14 38.4

39.3

-0.9 9 5.4

5.4

0.0 0

10 09/02/99 0900

0915

1.991.99

0.00 0 5.61

5.48

0.13 13 40.3

40.3

0.0 0 5.6

5.6

0.0 0

10 05/19/00 0830

0845

1.961.93

0.03 3 4.40

4.40

0.00 0 38.7

38.1

0.6 6 5.1

6.0

-0.9 9

10 05/17/01 1430

1500

1.911.90

0.01 1 5.11

5.03

0.08 8 39.0

38.9

0.1 1 5.3

5.3

0.0 0

11 08/31/99 1445

1500

2.022.02

0.00 0 6.65

5.64

1.01 101 45.5

45.8

-0.3 3 13.2

13.3

-0.1 1

11 05/17/00 1000

1015

2.042.06

-0.02 2 6.00

5.68

0.32 32 43.9

44.2

-0.3 3 12.3

12.4

-0.1 1
APPENDIXES 51

Table 6. Comparison of laboratory results for environmental and quality-control samples for 9 wells in the Fraser River watershed, 1998-2001.—Continued[All water-quality constituents are in the dissolved form except for total coliform bacteria, MBAS (methylene blue active substances), and radon-222. no, number; Env., environmental sample; QC, quality-control sample; Conc. diff., difference in concentration between environmental sample and quality-control sample; RU diff., absolute difference in lowest rounding unit; mg/L, milligrams per liter; shaded cells represent differences greater than 1 rounding unit; <, concentration less than the laboratory reporting level; E, estimated; nc, not calculated; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4+]; nitrate is nitrate plus nitrite; 

--, no data; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter. For calculations, “less than” (<) concentrations are presumed to be zero]

Site no.

(fig. 1;

table 1) 

Date Time

Sulfate Iron Manganese

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff. QC QC QC

(mg/L) (mg/L) (mg/L)

1 09/11/00 1330

1400

7.47.3

0.1 1 E 8

<10

nc nc <2.2

<2.2

0.0 0

1 05/14/01 1500

1515

6.06.0

0.0 0 <10

<10

0 0 <3.2

<3.2

0.0 0

4 09/14/00 1400

1415

2.52.6

-0.1 1 E 8

E 10

nc nc < 2.2

E 1.2

nc nc

5 09/13/01 1500

1530

3.13.3

-0.2 2 <10

<10

0 0 3.9

4.2

-0.3 3

6 08/27/98 1130

1200

2.02.1

-0.1 1 <10

<10

0 0 <4

<4

0 0

7 05/05/99 0930

1000

7.37.3

0.0 0 260

260

0 0 456

470

-14 14

8 09/13/00 0930

1000

16.015.9

0.1 1 <10

<10

0 0 14.9

13.4

1.5 15

8 05/16/01 0900

0930

12.112.4

-0.3 3 <10

<10

0 0 <3.2

<3.2

0.0 0

8 09/13/01 0945

1000

10.210.1

0.1 1 <10

<10

0 0 E 2.3

E 1.9

nc nc

9 05/03/99 1500

1530

3.23.3

-0.1 1 <10

<10

0 0 130

143

-13 13

9 08/30/99 1500

1530

4.64.6

0.0 0 <10

<10

0 0 73.8

77.1

-3.3 33

9 05/15/00 1500

1530

4.64.6

0.0 0 <10

<10

0 0 28.4

39.6

-11.2 112

9 09/10/01 1445

1515

3.23.3

-0.1 1 <10

E 8

nc nc 39.6

59.3

-19.7 197

10 05/07/99 0900

0915

2.32.3

0.0 0 <10

<10

0 0 <3

<3

0 0

10 09/02/99 0900

0915

2.32.4

-0.1 1 <10

<10

0 0 <3

<3

0 0

10 05/19/00 0830

0845

<0.3<0.3

0.0 0 <10

<10

0 0 <2.2

<2.2

0.0 0

10 05/17/01 1430

1500

2.62.5

0.1 1 <10

<10

0 0 <3.2

<3.2

0.0 0

11 08/31/99 1445

1500

1.71.9

-0.2 2 <10

<10

0 0 <3

<3

0 0

11 05/17/00 1000

1015

1.61.6

0.0 0 <10

<10

0 0 <2.2

<2.2

0.0 0
52 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 6. Comparison of laboratory results for environmental and quality-control samples for 9 wells in the Fraser River watershed, 1998–2001.—Continued All water-quality constituents are in the dissolved form except for total coliform bacteria, MBAS (methylene blue active substances), and radon-222. no., number; Env., environmental sample; QC, quality-control sample; Conc. diff., differ- ence in concentration between environmental sample and quality-control sample; RU diff., absolute difference in lowest rounding unit; mg/L, milligrams per liter; shaded cells represent differences greater than 1 rounding unit; <, concen- tration less than the laboratory reporting level; E, estimated; nc, not calculated; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4

+]; nitrate is nitrate plus nitrite; --, no data; col/100 mL, colonies per 100 milliliters; pCi/L, 

picocuries per liter. For calculations, “less than” (<) concentrations are presumed to be zero]

Site no. 

(fig. 1; 

table 1) 

Date Time

Ammonia Ammonia plus organic nitrogen Nitrite Nitrate

Env. Conc. 

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff. QC QC QC QC

(mg/L) (mg/L) (mg/L) (mg/L)

1 09/11/00 1330

1400

<0.002<0.002

0.000 0 0.1

0.2

-0.1 1 <0.001

<0.001

0.000 0 0.288

0.290

-0.002 2

1 05/14/01 1500

1515

0.0030.006

-0.003 3 0.2

0.2

0.0 0 <0.001

<0.001

0.000 0 1.73

1.69

0.04 4

4 09/14/00 1400

1415

0.0040.007

-0.003 3 <0.1

<0.1

0.0 0 0.001

0.001

0.000 0 1.16

1.15

0.01 1

5 09/13/01 1500

1530

<0.002

0.002

-0.002 2 <0.1

<0.1

0.0 0 <0.001

<0.001

0.000 0 0.143

0.141

0.002 2

6 08/27/98 1130

1200

0.0020.008

-0.006 6 <0.1

<0.1

0.0 0 <0.001

<0.001

0.000 0 0.019

0.018

0.001 1

7 05/05/99 0930

1000

0.0140.011

0.003 3 E 0.1

E 0.09

nc nc <0.001

<0.001

0.000 0 <0.005

<0.005

0.000 0

8 09/13/00 0930

1000

<0.002<0.002

0.000 0 E 0.1

E 0.1

0.0 0 0.004

0.003

0.001 1 4.72

4.73

-0.01 1

8 05/16/01 0900

0930

0.0050.011

-0.006 6 0.1

0.1

0.0 0 <0.001

<0.001

0.000 0 3.10

1.73

1.37 137

8 09/13/01 0945

1000

0.0020.004

-0.002 2 <0.1

<0.1

0.0 0 0.001

<0.001

0.001 1 2.62

2.56

0.06 6

9 05/03/99 1500

1530

0.0110.008

0.003 3 E 0.08

0.1

nc nc --

<0.001

-- -- 0.059

0.053

0.006 6

9 08/30/99 1500

1530

<0.002<0.002

0.000 0 0.1

E 0.09

nc nc <0.001

0.001

-0.001 1 0.082

0.081

0.001 1

9 05/15/00 1500

1530

0.0020.005

-0.003 3 0.1

0.1

0.0 0 <0.001

<0.001

0.000 0 0.088

0.085

0.003 3

9 09/10/01 1445

1515

<0.002<0.002

0.000 0 0.1

0.1

0.0 0 0.001

0.001

0.000 0 0.110

0.110

0.000 0

10 05/07/99 0900

0915

0.0120.010

0.002 2 <0.1

<0.1

0.0 0 <0.001

<0.001

0.000 0 0.236

0.242

-0.006 6

10 09/02/99 0900

0915

0.005

<0.002

0.005 5 E 0.08

E 0.08

0.00 0 0.001

0.002

-0.001 1 0.292

0.280

0.012 12

10 05/19/00 0830

0845

<0.002

0.002

-0.002 2 <0.1

<0.1

0.0 0 <0.001

<0.001

0.000 0 0.252

0.271

-0.019 19

11 08/31/99 1445

1500

0.004

<0.002

0.004 4 <0.1

<0.1

0.0 0 0.001

<0.001

0.001 1 0.225

0.225

0.000 0

11 05/17/00 1000

1015

0.0030.002

0.001 1 <0.1

<0.1

0.0 0 <0.001

<0.001

0.000 0 0.233

0.233

0.000 0
APPENDIXES 53

Table 6. Comparison of laboratory results for environmental and quality-control samples for 9 wells in the Fraser River watershed, 1998–2001.—Continued[All water-quality constituents are in the dissolved form except for total coliform bacteria, MBAS (methylene blue active substances), and radon-222. no., number; Env., environmental sample; QC, quality-control sample; Conc. diff., difference in concentration between environmental sample and quality-control sample; RU diff., absolute difference in lowest rounding unit; mg/L, milligrams per liter; shaded cells represent differences greater than 1 rounding unit; <, concentration less than the laboratory reporting level; E, estimated; nc, not calculated; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4+]; nitrate is nitrate plus nitrite; -

-, no data; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter. For calculations, “less than” (<) concentrations are presumed to be zero]

Site no. 

(fig. 1 

table 1)

Date Time

Phosphorus Orthophosphate Dissolved organic carbon

Env. Conc. 

diff.

RU

diff.

Env. Conc. 

diff.

RU

diff.

Env. Conc. 

diff.

RU

diff. QC QC QC

(mg/L) (mg/L) (mg/L)

1 09/11/00 1330

1400

0.0070.010

-0.003 3 0.007

0.007

0.000 0 3.0

3.0

0.0 0

1 05/14/01 1500

1515

0.0070.007

0.000 0 E 0.005

E 0.005

0.000 0 3.3

3.2

0.1 1

4 09/14/00 1400

1415

0.0170.018

-0.001 1 0.016

0.017

-0.001 1 0.49

0.56

-0.07 7

5 09/13/01 1500

1530

0.0460.046

0.000 0 0.042

0.044

-0.002 2 0.72

0.70

0.02 2

6 08/27/98 1130

1200

0.0600.062

-0.002 2 0.061

0.060

0.001 1 1.9

1.8

0.1 1

7 05/05/99 0930

1000

0.0160.021

-0.005 5 0.017

0.023

-0.006 6 1.9

1.9

0.0 0

8 09/13/00 0930

1000

0.0520.053

-0.001 1 0.049

0.049

0.000 0 1.3

1.3

0.0 0

8 05/16/01 0900

0930

0.0500.052

-0.002 2 0.047

0.049

-0.002 2 1.2

1.0

0.2 2

8 09/13/01 0945

1000

0.0510.048

0.003 3 0.046

0.047

-0.001 1 0.98

1.0

-0.02 2

9 05/03/99 1500

1530

0.0640.058

0.006 6 0.060

0.059

0.001 1 2.0

2.2

-0.2 2

9 08/30/99 1500

1530

0.0590.058

0.001 1 0.062

0.060

0.002 2 2.3

2.3

0.0 0

9 05/15/00 1500

1530

0.0520.054

-0.002 2 0.052

0.054

-0.002 2 2.3

2.2

0.1 1

9 09/10/01 1445

1515

0.0560.056

0.000 0 0.050

0.050

0.000 0 2.2

2.2

0.0 0

10 05/07/99 0900

0915

0.1310.130

0.001 1 0.130

0.131

-0.001 1 0.8

0.8

0.0 0

10 09/02/99 0900

0915

0.1340.132

0.002 2 0.137

0.134

0.003 3 1.0

1.0

0.0 0

10 05/19/00 0830

0845

0.1320.133

-0.001 1 0.126

0.126

0.000 0 0.91

0.91

0.00 0

11 08/31/99 1445

1500

0.0330.033

0.000 0 0.037

0.036

0.001 1 0.7

0.7

0.0 0

11 05/17/00 1000

1015

0.0350.035

0.000 0 0.036

0.035

0.001 1 0.74

0.67

0.07 7
54 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 6. Comparison of laboratory results for environmental and quality-control samples for 9 wells in the Fraser River watershed, 1998–2001.—Continued [All water-quality constituents are in the dissolved form except for total coliform bacteria, MBAS (methylene blue active substances), and radon-222. no., number; Env., environmental sample; QC, quality-control sample; Conc. diff., difference in concentration between environmental sample and quality-control sample; RU diff., absolute difference in lowest rounding unit; mg/L, milligrams per liter; shaded cells represent differ- ences greater than 1 rounding unit; <, concentration less than the laboratory reporting level; E, estimated; nc, not calculated; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4

+]; nitrate is nitrate plus nitrite; 

--, no data; col/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter. For calculations, “less than” (<) concentrations are presumed to be zero]

Site no. 

(fig. 1 

table 1)

Date Time

Total coliform bacteria MBAS Radon-222, total

Env. Conc. 

diff.

RU

diff.

Env. Conc.

diff.

RU

diff.

Env. Conc.

diff.

RU

diff. QC QC QC

(col/100 mL) (mg/L) (pCi/L)

1 09/11/00 1330

1400

<1

--

-- -- 0.02

<0.02

0.02 2 --

--

-- --

1 05/14/01 1500

1515

E 140

--

-- -- 0.02

0.02

0.00 0 --

--

-- --

4 09/14/00 1400

1415

<1

--

-- -- <0.02

<0.02

0.00 0 --

--

-- --

5 09/13/01 1500

1530

<1

--

-- -- <0.02

<0.02

0.00 0 --

--

-- --

6 08/27/98 1130

1200

<1

--

-- -- <0.02

<0.02

0.00 0 365

--

-- --

7 05/05/99 0930

1000

<1

--

-- -- <0.02

<0.02

0.00 0 764

733

31 31

8 09/13/00 0930

1000

<1

--

-- -- <0.02

<0.02

0.00 0 --

--

-- --

8 05/16/01 0900

0930

<1

--

-- -- <0.02

0.03

-0.03 3 --

--

-- --

8 09/13/01 0945

1000

<1

--

-- -- <0.02

<0.02

0.00 0 --

--

-- --

9 05/03/99 1500

1530

----

-- -- <0.02

<0.02

0.00 0 669

747

-78 78

9 08/30/99 1500

1530

<1<1

0 0 <0.02

<0.02

0.00 0 687

677

10 10

9 05/15/00 1500

1530

<1<1

0 0 <0.02

<0.02

0.00 0 --

--

-- --

9 09/10/01 1445

1515

<1

--

-- -- <0.02

<0.02

0.00 0 --

--

-- --

10 05/07/99 0900

0915

<1

--

-- -- <0.02

0.03

-0.03 3 752

738

14 14

10 09/02/99 0900

0915

<1<1

0 0 <0.02

<0.02

0.00 0 752

705

47 47

10 05/19/00 0830

0845

<1<1

0 0 <0.02

<0.02

0.00 0 --

--

-- --

11 08/31/99 1445

1500

<1<1

0 0 <0.02

<0.02

0.00 0 1093

1100

-7 7

11 05/17/00 1000

1015

<1<1

0 0 <0.02

<0.02

0.00 0 --

--

-- --
APPENDIXES 55

Table 7. Summary of differences between environmental and quality-control samples for wells in the Fraser River watershed, 1998–2001.[All water-quality constituents are in the dissolved form except for total coliform bacteria, MBAS (methylene blue active substances), and radon-222. Lowest rounding unit is equal to the magnitude of the least significant figure reported by the U.S. Geological Survey National Water Quality Laboratory; NA, not applicable; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4+]; nitrate is nitrate plus nitrite]

Constituent

Number of 

replicate 

pairs

evaluated

Percentage of

replicate pairs

with no

difference

Percentage of

replicate pairs 

within 1 lowest 

rounding unit

Percentage of

replicate pairs 

within 2 lowest 

rounding units

Number of

replicate pairs with

concentration(s) 

less than the 

laboratory 

reporting level

Number of

replicate pairs with 

inconsistency in 

reporting concentrations less than 

the laboratory 

reporting level

Bromide 19 68 100 100 6 1Calcium 19 0 32 37 NA NAChloride 19 42 79 84 NA NAFluoride 19 84 100 100 4 0Magnesium 19 11 37 47 NA NAPotassium 19 5.3 21 37 NA NASilica 19 16 32 32 NA NASodium 19 37 74 79 NA NASulfate 19 37 84 95 1 0Iron 16 100 100 100 15 0Manganese 17 59 59 59 10 0Ammonia 18 22 28 50 8 4Ammonia plus organic 

nitrogen

15 93 100 100 8 0

Nitrite 17 71 100 100 13 3Nitrate 18 22 44 56 1 0Phosphorus 18 28 56 78 NA NAOrthophosphate 18 28 67 89 NA NADissolved organic 

carbon

18 50 67 89 NA NA

Total coliform bacteria 6 100 100 100 6 0MBAS 18 83 83 89 17 3Radon-222, total 6 0 0 0 NA NA
56 Water-Quality Characteristics and Ground-Water Quantity of the Fraser River Watershed, Grand County, Colorado, 1998–2001 Table 8. Variability and uncertainty in manganese, ammonia, nitrate, and radon-222 concentrations as determined by replicate pairs for wells in the Fraser River watershed, 1998–2001. [All water-quality constituents are in the dissolved form, unless otherwise noted. Ammonia, un-ionized ammonia [NH3] plus ammonium [NH4

+]; nitrate is nitrate plus nitrite; 

±, plus or minus]

Constituent Variability1 in concentration (percent) Uncertainty2 in concentration (95-percent confidence) (percent)

Manganese (site 9) 15.3

±31.8

Ammonia (9 wells) 54.3

±113

Nitrate (9 wells) 1.79

±3.72

Radon-222, total (4 wells) 8.3

±17.3

1Variability=mean relative standard deviation of replicate pairs for constituent. Relative standard deviation of a replicate pair=100×({SQRT[(C1–C2)

2/2]}/[(C1+C2)/2]), where SQRT is 

square root, C1 is concentration of environmental sample, and C2 is concentration of quality-control sample.

2Uncertainty=±2.080×(mean relative standard deviation of replicate pair).

Table 9. Concentrations of major ions, trace elements, nutrients, and dissolved organic carbon in blank samples for wells in the Fraser River watershed, 1998–2001[All water-quality constituents are in the dissolved form. no., number; mg/L, milligrams per liter; <, concentration less than the laboratory reporting level; E, estimated; shaded cells represent concentrations greater than twice the laboratory 

reporting levels; --, no data; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4

+]; nitrate is nitrate plus nitrite]

Site no.

(fig. 1;

table 1)

Date Time

Concentration (mg/L)

Bromide Calcium Chloride Fluoride Magnesium Potassium Silica Sodium Sulfate Iron Manganese

6 08/27/98 1530 0.01 <0.02 <0.1 <0.1 <0.004 <0.1 <0.1 <0.1 <0.1 <10 <49 05/03/99 1400 <0.01 E 0.01 <0.1 <0.1 E 0.002 <0.1 <0.05 <0.06 <0.1 <10 <37 05/05/99 0800 <0.01 E 0.02 <0.1 <0.1 <0.004 <0.1 <0.05 E 0.04 <0.1 <10 <3

10 05/07/99 1000 <0.01 <0.02 <0.1 <0.1 E 0.002 <0.1 <0.05 E 0.04 <0.1 <10 <3

9 08/30/99 1400 <0.01 0.04 <0.1 <0.1 0.010 <0.1 <0.05 E 0.03 <0.1 10 <3

11 08/31/99 1545 <0.01 <0.02 <0.1 <0.1 <0.004 <0.1 <0.05 <0.06 <0.1 <10 <310 09/02/99 1000 <0.01 <0.02 <0.1 <0.1 <0.004 <0.1 <0.05 <0.06 <0.1 <10 <3

9 05/15/00 1400 <0.01 E 0.01 <0.29 <0.1 <0.014 <0.24 <0.09 E 0.08 <0.31 <10 <2.2

11 05/17/00 0900 <0.01 <0.02 <0.29 <0.1 <0.014 <0.24 <0.09 <0.09 <0.31 <10 <2.210 05/19/00 0930 <0.01 <0.02 <0.29 <0.1 <0.014 <0.24 <0.09 <0.09 <0.31 <10 <2.2

1 09/11/00 1200 <0.01 0.03 <0.29 <0.1 <0.014 <0.24 <0.09 <0.09 <0.31 <10 E 1.28 09/13/00 0800 <0.01 <0.02 <0.29 <0.1 <0.014 <0.24 <0.09 <0.09 <0.31 <10 <2.24 09/14/00 1530 <0.01 <0.02 <0.29 <0.1 <0.014 <0.24 <0.09 <0.09 <0.31 <10 <2.28 05/16/01 0800 <0.01 <0.011 <0.08 <0.16 <0.008 <0.09 <0.09 <0.06 <0.11 <10 <3.29 09/10/01 1345 <0.01 0.019 <0.08 <0.16 <0.008 <0.09 <0.09 E 0.03 E 0.05 <10 <3.28 09/13/01 0830 <0.01 <0.011 <0.08 <0.16 <0.008 <0.09 <0.09 <0.06 <0.11 <10 <3.25 09/13/01 1620 <0.01 <0.011 <0.08 <0.16 <0.008 <0.09 <0.09 <0.06 <0.11 <10 <3.2
APPENDIXES 57

Table 9. Concentrations of major ions, trace elements, nutrients, and dissolved organic carbon in blank samples for wells in the Fraser River watershed, 1998–2001.—Continued[All water-quality constituents are in the dissolved form. no., number; mg/L, milligrams per liter; <, concentration less than the laboratory reporting level; E, estimated; shaded cells represent concentrations greater than twice the laboratory reporting levels; ammonia, un-ionized ammonia [NH3] plus ammonium [NH4+]; nitrate is nitrate plus nitrite]

Site no. 

(fig. 1; 

table 1)

Date Time

Concentration (mg/L)

Ammonia

Ammonia 

plus organic 

nitrogen

Nitrite Nitrate Phosphorus Orthophosphate

Dissolved 

organic 

carbon

6 08/27/98 1530 <0.002 <0.1 0.001 <0.005 <0.001 <0.001 <0.19 05/03/99 1400 0.004 E 0.05 <0.001 0.005 <0.004 <0.001 0.47 05/05/99 0800 0.004 <0.1 <0.001 0.005 <0.004 <0.001 <0.1

10 05/07/99 1000 0.005 <0.1 <0.001 0.005 <0.004 0.001 <0.1

9 08/30/99 1400 <0.002 <0.1 <0.001 <0.005 <0.004 0.001 0.2

11 08/31/99 1545 0.003 <0.1 <0.001 0.005 <0.004 <0.001 <0.110 09/02/99 1000 <0.002 E 0.06 <0.001 <0.005 <0.004 <0.001 <0.1

9 05/15/00 1400 <0.002 <0.1 <0.001 <0.005 <0.006 <0.001 E 0.28

11 05/17/00 0900 0.002 <0.1 <0.001 <0.005 <0.006 <0.001 E 0.1810 05/19/00 0930 0.021 <0.1 <0.001 <0.005 <0.006 0.003 <0.33

1 09/11/00 1200 <0.002 <0.1 <0.001 <0.005 <0.006 <0.001 <0.338 09/13/00 0800 <0.002 <0.1 <0.001 <0.005 <0.006 <0.001 <0.334 09/14/00 1530 <0.002 <0.1 <0.001 <0.005 <0.006 0.002 E 0.261 05/14/01 1330 <0.002 <0.1 <0.001 <0.005 <0.006 <0.007 <0.338 05/16/01 0800 <0.002 <0.1 <0.001 <0.005 <0.006 <0.007 E 0.23

10 05/17/01 1600 0.004 <0.1 <0.001 <0.005 <0.006 <0.007 <0.33

9 09/10/01 1345 <0.002 <0.1 <0.001 0.006 <0.006 <0.007 E 0.258 09/13/01 0830 <0.002 <0.1 <0.001 0.006 <0.006 <0.007 E 0.205 09/13/01 1620 <0.002 <0.1 <0.001 0.006 <0.006 <0.007 E 0.20