U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 00–4186

Assessment of Water Quality, Road 

Runoff, and Bulk Atmospheric 

Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, 

Colorado, Water Years 1995–97

By Michael R. Stevens

Denver, Colorado

2001

Prepared in cooperation with the

FEDERAL HIGHWAY ADMINISTRATION and

CLEAR CREEK COUNTY
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes only and does

not constitute endorsement by the U.S. Geological Survey.

For additional information write to: Copies of this report can be purchased

U.S. Geological Survey

Information Services

Box 25286

Federal Center

Denver, CO 80225

from:

District Chief

U.S. Geological Survey

Box 25046, Mail Stop 415

Denver Federal Center

Denver, CO 80225–0046
CONTENTS III

CONTENTS

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

Introduction............................................................................................................................................................................ 3

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

Acknowledgments ....................................................................................................................................................... 3

Description of Study Area ..................................................................................................................................................... 3

Monitoring Network and Quality Assurance......................................................................................................................... 5

Characterization of Water Resources..................................................................................................................................... 12

Precipitation................................................................................................................................................................. 12

Streams ........................................................................................................................................................................ 13

Hydrology .......................................................................................................................................................... 13

Water-Quality Characteristics............................................................................................................................ 15

Onsite Measurements............................................................................................................................... 16

Dissolved-Solids Loads ........................................................................................................................... 22

Major Ions................................................................................................................................................ 23

Possible Effects of Magnesium Chloride Applications on Major-Ion Chemistry in Streams ................. 26

Nutrients .................................................................................................................................................. 36

Trace Elements ........................................................................................................................................ 41

Suspended Sediment, Turbidity, and Streambed-Particle Size................................................................ 46

Basin Characteristics of Suspended-Sediment Sites...................................................................... 46

Suspended-Sediment Concentrations and Loads........................................................................... 48

Comparison-Site Suspended-Sediment Yields .............................................................................. 50

Sediment Discharge by Hydrograph Period .................................................................................. 51

Turbidity ........................................................................................................................................ 52

Peak Suspended Sediment and Turbidity During Storms.............................................................. 53

Bed-Material Particle Size............................................................................................................. 54

Storm-Runoff Effects on Stream-Water Quality...................................................................................... 55

Lakes and Reservoirs ................................................................................................................................................... 64

Vertical Profiles and Onsite Measurements ....................................................................................................... 64

Transparency and Chlorophyll........................................................................................................................... 67

Water-Column Major Ions, Nutrients, and Trace Elements............................................................................... 67

Nutrient Limitation and Trophic Status ............................................................................................................. 69

Bottom-Sediment Chemistry ............................................................................................................................. 69

Ground Water............................................................................................................................................................... 71

Onsite Measurements and Major Ions ............................................................................................................... 71

Nutrients ............................................................................................................................................................ 74

Trace Elements .................................................................................................................................................. 74

Comparisons with Water-Quality Standards................................................................................................................ 74

Streams .............................................................................................................................................................. 74

Colorado Water-Quality Standards.......................................................................................................... 74

Other Guidelines...................................................................................................................................... 79

Ground Water..................................................................................................................................................... 80

Characterization of Guanella Pass Road Runoff ................................................................................................................... 81

Background Information on Forest Road Hydrology .................................................................................................. 81

Hydrology .................................................................................................................................................................... 83

Water-Quality Characteristics...................................................................................................................................... 84

Onsite Measurements and Major Ions ............................................................................................................... 84

Nutrients ............................................................................................................................................................ 86

Trace Elements .................................................................................................................................................. 87

Organic Carbon and Trace-Organic Constituents.............................................................................................. 87

Suspended Sediment and Particle Size .............................................................................................................. 87

Sources and Transport of Sediment in Road Runoff ................................................................................................... 87
IV CONTENTS

Sources and Deposits of Sediment .................................................................................................................... 87

Road Drainage and Stream Linkage.................................................................................................................. 93

Seasonal Characteristics of Sediment and Dissolved Solids in Road Runoff ................................................... 102

Sediment .................................................................................................................................................. 104

Dissolved Solids ...................................................................................................................................... 106

Potential Effects of Road Runoff on Receiving Water ................................................................................................ 106

Streams .............................................................................................................................................................. 106

Lakes and Reservoirs......................................................................................................................................... 110

Ground Water .................................................................................................................................................... 110

Bulk Atmospheric Deposition ............................................................................................................................................... 111

Effect of Road-Surface Type ....................................................................................................................................... 111

Distribution Characteristics ......................................................................................................................................... 112

Estimate of Bulk Atmospheric-Deposition Contributions from an Unpaved Road Section ....................................... 112

Summary and Conclusions .................................................................................................................................................... 114

References Cited.................................................................................................................................................................... 117

Appendix—Hydrologic and Water-Quality Data .................................................................................................................. 121

FIGURES

1–4. Maps showing:

1. Location of Guanella Pass study area and stream data-collection sites ........................................................... 4

2. Location of lake, reservoir, road-runoff, and snow-sampling sites .................................................................. 7

3. Location of ground-water and bulk atmospheric-deposition sampling sites.................................................... 8

4. Location of selected precipitation and suspended-sediment sampling sites in Colorado ................................ 14

5–10. Graphs showing:

5. Generalized stream hydrograph divided into seasonal periods........................................................................ 16

6. Fluctuations in instantaneous stream discharge at sites GC11 and CC5, April through 

September 1997................................................................................................................................................ 17

7. Daily mean water discharge at Geneva Creek at Grant (GC11), water years 1995–97 ................................... 19

8. Flow-duration curves at Geneva Creek at Grant (GC11), water years 1995–97.............................................. 20

9. Monthly mean water temperature at selected sites, water years 1996–97 ....................................................... 24

10. Seasonal variation of specific conductance and streamflow at site DC1, water year 1997 ............................. 26

11. Boxplots showing distribution of concentrations and values of selected water-quality constituents 

at selected sites, water years 1995–97 ..................................................................................................................... 28

12–24. Graphs showing:

12. Comparison of water discharge, specific conductance, chloride concentration, turbidity, 

and suspended sediment at CC1 (upstream) and CC2 (downstream) and CC13 (upstream) 

and CC5 (downstream), in water year 1997..................................................................................................... 34

13. Values and concentrations of specific conductance, pH, and instantaneous water discharge 

at water-quality-sampling sites along South Clear Creek during low-flow synoptic sampling, 

September 6, 1995............................................................................................................................................ 39

14. Percentages of major ions at water-quality-sampling sites along South Clear Creek during 

low-flow synoptic sampling, September 6, 1995............................................................................................. 40

15. Relation of chloride load with instantaneous water discharge at site CC5, water years 1995–97................... 42

16. Variations in selected dissolved-phase and total recoverable trace-element loads along Geneva 

Creek from GC6 to GC12 during low-flow synoptic sampling, September 1995........................................... 44

17. Variation in daily mean water discharge, daily flow-weighted-mean suspended-sediment 

concentration, and daily mean suspended-sediment discharge at site GC11, water years 1995–97................ 49

18. Relation of suspended-sediment discharge to annual streamflow for selected sites, water 

years 1995–97 .................................................................................................................................................. 51

19. Relation of suspended-sediment discharge to drainage-basin area for selected sites, water 

years 1995–97 .................................................................................................................................................. 52

20. Relation of suspended-sediment yield per square mile to annual streamflow for selected sites, 

water years 1995–97 ........................................................................................................................................ 53

21. Relation of rising-limb suspended-sediment discharge and instantaneous water discharge for 

selected sites and a composite of undisturbed reference sites (REF), water years 1995–97 ........................... 57
CONTENTS V

22. Daily fluctuations in instantaneous turbidity and water discharge at site CC5, May 5–9, 1997..................... 58

23. Profile of water-temperature and specific-conductance variation with depth in Duck Lake 

and Clear Lake on selected sampling dates during water year 1997 ............................................................... 65

24. Profile of pH and dissolved-oxygen variation with depth in Duck Lake and Clear Lake on 

selected sampling dates during water year 1997 ............................................................................................. 66

25. Piper diagram of chemical composition of ground-water samples collected during water 

years 1995–97.......................................................................................................................................................... 72

26. Scatterplot showing relations of magnesium, sodium, and chloride concentrations and specific 

conductance, and the relation of chloride concentration and the mass ratio of calcium to magnesium, 

for ground-water samples collected during water years 1995–97........................................................................... 73

27. Schematic of a forest road ....................................................................................................................................... 81

28. Graph showing variation in daily mean water discharge at CRD7 (road-runoff site) and CC2 

(the potential receiving stream), water years 1996–97............................................................................................ 85

29–44. Photographs showing:

29. Boulders eroded from cutslope on Guanella Pass road near disused ski area, May 1996............................... 88

30. Cutslope just north of Green Lake along Guanella Pass road, May 1994 ....................................................... 89

31. Cutslope along Guanella Pass road in the switchback road segment above Naylor Creek 

north of Guanella Pass, July 1995 ................................................................................................................... 89

32. Cutslope along Guanella Pass road in the Falls Hill segment just north of the Scott Gomer 

Creek crossing, January 1994 .......................................................................................................................... 90

33. Erosion of fillslope and side-cast material by Geneva Creek, high streamflow, June 1995 ............................ 90

34. Appearance of fillslope at low streamflow in Geneva Creek after repair and regrading 

of road, August 1995 ....................................................................................................................................... 91

35. Culvert outflow concentrating road runoff onto the fillslope in the switchback road segment 

above South Clear Creek, upstream from Naylor Creek, July 1995................................................................ 91

36. Rutting and erosion of the road surface just south of Naylor Creek................................................................ 92

37. Ditch erosion in the switchback road segment, south of Naylor Creek, August 1998 .................................... 93

38. Eroded road-runoff channel about 200 feet below the Guanella Pass road, located in the 

switchback road segment south of Naylor Creek, August 1996...................................................................... 93

39. Alluvial fan of material eroded from a channel cut by road runoff on the slope above South 

Clear Creek upstream from Naylor Creek, August 1996................................................................................. 94

40. Deposit of road-runoff sediment covering tundra vegetation just north of Duck Lake, near 

the summit of Guanella Pass, July 1995.......................................................................................................... 94

41. Abandoned beaver pond filled with sediment on South Clear Creek upstream from Lower 

Cabin Creek Reservoir, June 1996................................................................................................................... 95

42. Sediments behind beaver dam that is being eroded by South Clear Creek, June 1998 ................................... 95

43. Alluvial fan at the inlet of South Clear Creek to Georgetown Reservoir, just downstream 

from the confluence with Leavenworth Creek, September 1995 .................................................................... 96

44. Cutbank in mine waste along Leavenworth Creek between Guanella Pass road and the 

confluence with South Clear Creek, August 1995........................................................................................... 96

45. Map showing location and identification of drainage features (roadside ditches and culverts) 

that showed evidence of sediment reaching a stream ...................................................................................... 97

46. Map showing location of culvert monitoring site and the segment of the road draining to 

the monitoring site (short segment), and the location of the segment of road draining to 

South Clear Creek upstream from the CC2 sampling site............................................................................... 105

47. Boxplot showing distribution of suspended-sediment concentrations for high-streamflow, 

low-streamflow, and road-runoff samples........................................................................................................ 109

48–50. Graphs showing:

48. Comparison of median bulk atmospheric-deposition rates by type of site...................................................... 111

49. Distribution of bulk atmospheric deposition at site G, August through September 1996 ............................... 112

50. Relation of bulk atmospheric-deposition (less than 2 millimeters) rate and distance from the 

Guanella Pass road for data collected at sites L, M, and N, August through September 1997 ....................... 113
VI CONTENTS

TABLES

1. Data-collection sites ................................................................................................................................................ 9

2. Summary of quality-assurance data, water years 1995–97..................................................................................... 11

3. Selected National Atmospheric Deposition Program/National Trends Network sites in Colorado........................ 13

4. Rainfall chemical quality at selected Front Range of Colorado NADP/NTN sites in 1997 ................................... 15

5. Stream discharge data for water years 1995–97 at sites with stream gages............................................................ 18

6. Percentage of average annual flow for streams near Guanella Pass study area, water years 1995–97................... 20

7. Summary of stream-water-quality statistics, water years 1995–97......................................................................... 21

8. Selected monthly mean water temperature in degrees Celsius for sites with continuous watertemperature measurement ....................................................................................................................................... 23

9. Spearman’s coefficients of correlation for specific conductance and concentrations of selected 

water-quality constituents at selected sites, water years 1995–97 .......................................................................... 27

10. Dissolved-solids loads computed for selected sites, water years 1995–97 ............................................................. 36

11. Spearman’s coefficients of correlation for instantaneous water discharge and concentrations 

of selected water-quality constituents at selected sites, water years 1995–97 ........................................................ 37

12. Spearman’s coefficients of correlation for suspended-sediment concentration and concentrations 

of selected water-quality constituents at selected sites, water years 1995–97 ........................................................ 38

13. Estimates of mass of chloride in dust inhibitor applied to Guanella Pass road and annual chloride 

load and hypothetical concentration estimates in South Clear Creek at site CC5 .................................................. 41

14. Summary of trace-element data ranges for sites that are affected and sites that are unaffected by 

acid-sulfate weathering in the watershed ................................................................................................................ 43

15. Basin characteristics of suspended-sediment discharge monitoring sites and upstream/downstream 

paired sites .............................................................................................................................................................. 47

16. Regression coefficients and information used to compute suspended-sediment loads at selected 

sites, water years 1996–97 ...................................................................................................................................... 50

17. Summary of annual suspended-sediment discharges and suspended-sediment yields at selected 

sites, water years 1995–97 ...................................................................................................................................... 50

18. Generalized basin characteristics for suspended-sediment comparison sites located outside the 

study area ................................................................................................................................................................ 54

19. Summary of annual streamflow and suspended-sediment yields for selected comparison streams 

in Colorado with crystalline bedrock geology and Guanella Pass streams............................................................. 55

20. Summary of hydrograph period contributions for water discharge and suspended sediment at 

selected sites, water years 1995–97 ........................................................................................................................ 56

21. Regression equations and information for rising limb of snowmelt hydrograph at selected sites, 

water years 1995–97 ............................................................................................................................................... 57

22. Ambient and rainstorm peak-measured suspended-sediment and turbidity data at sites with 

pumping samplers, water years 1995–97 ................................................................................................................ 59

23. Bed-material particle-size data collected at stream sites, Guanella Pass area ........................................................ 61

24. Selected water-quality properties or constituents of water samples collected during prestorm 

(base flow) and storm runoff in South Clear Creek above Naylor Creek (CC2) on August 21, 1996, 

and Deer Creek near Bailey (DC1) on August 23, 1996......................................................................................... 62

25. Comparison of selected water-quality constituents and trace-element phase changes at Geneva Creek 

(GC11) between two storm-event samples (09–12–96 and 08–09–97) and corresponding base-flow 

reference samples .................................................................................................................................................... 63

26. Mass ratio computations of nitrogen to phosphorus and limiting nutrients in Duck Lake (L1) and 

Clear Lake (L3) surface or photic-zone composite samples, water year 1997 ....................................................... 68

27. Trophic-state index computations for Duck Lake (L1) and Clear Lake (L3), water year 1997.............................. 70

28. Selected bottom-sediment chemical concentrations for lake and reservoir sites, water years 1995–97................. 71

29. Regression equations and information used to compute hardness concentrations at selected sites, 

water years 1995–97 ............................................................................................................................................... 75
CONTENTS VII

30. Water-quality standards for selected stream-sampling sites along the Guanella Pass road for 

constituents and properties sampled ....................................................................................................................... 76

 31. Drinking-water-quality standards for selected constituents and properties............................................................ 80

32. Road-runoff linkages and road-drainage density in basins of selected stream-sampling sites............................... 103

33. Characteristics of road-runoff monitoring sites ...................................................................................................... 103

34. Water discharge, sediment transport, and dissolved-solids transport at site CRD7, water years 1996–97 ............ 104

35. Summary of stream and road-runoff water quality, water years 1995–97.............................................................. 107

36. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC1 ................. 123

37. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC2 ................. 125

38. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC5 ................. 127

39. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC7 ................. 129

40. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC9 ................. 131

41. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC11 ............... 133

42. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC1................. 135

43. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC2................. 137

44. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC5................. 139

45. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC7................. 141

46. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC8................. 143

47. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC10............... 145

48. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC11............... 147

49. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at DC1................. 149

50. Summary of water-quality statistics for analyses of ground-water samples collected, water years 1995–97........ 151

51. Selected water-quality data collected at road-runoff sites, water years 1995–97................................................... 153

52. Summary of water-quality statistics for analyses of selected samples collected, water years 1995–97, 

at road-runoff sites during snowmelt ...................................................................................................................... 160

53. Summary of water-quality statistics for analyses of selected samples collected, water years 1995–97, 

at road-runoff sites during rainfall events ............................................................................................................... 162

54. Drainage-feature evaluation data ............................................................................................................................ 164

55. Suspended-sediment discharge from Guanella Pass road segment upstream from Naylor Creek 

expressed as a percentage of suspended-sediment discharge at CC2 and as a potential change in 

concentration at CC2, during CRD7 flow period, water year 1996........................................................................ 178

56. Suspended-sediment discharge from Guanella Pass road segment upstream from Naylor Creek 

expressed as a percentage of suspended-sediment discharge at CC2 and as a potential change in 

concentration at CC2, during CRD7 flow period, water year 1997........................................................................ 179

57. Dissolved-solids discharge from Guanella Pass road segment upstream from Naylor Creek expressed 

as a percentage of dissolved-solids discharge at CC2 and as a potential change in concentration at 

CC2, during CRD7 flow period, water year 1996 .................................................................................................. 180

58. Dissolved-solids discharge from Guanella Pass road segment upstream from Naylor Creek expressed 

as a percentage of dissolved-solids discharge at CC2 and as a potential change in concentration at 

CC2, during CRD7 flow period, water year 1997 .................................................................................................. 182
VIII CONTENTS

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic datum derived

from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

Additional Abbreviations

MCL Maximum Contaminant Level

mg milligrams

(mg/d)/ft2 milligrams per day per square foot

mg/L milligrams per liter

mm millimeters

NTU nephelometric turbidity units

ROE residue on evaporation

μg/L micrograms per liter

μm micrometers

μm3/cm2 cubic micrometers per square centimeter

μS/cm microsiemens per centimeter at 25 degrees Celsius

Multiply By To obtain

acre 0.00156 square mile

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

acre-foot per square mile (acre-ft/mi2) 0.000476 cubic hectometer per square kilometer

yard 0.9144 meter

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

foot (ft) 0.3048 meter

inch 25.4 centimeter

mile 1.609 kilometer

square centimeter (cm2) 0.1550 square inch (in2)

square foot (ft2) 0.0929 square meter

square mile (mi2) 2.590 square kilometer (km2)

ton, short 0.9072 megagram or metric ton

ton per day (T/d) 0.9072 megagram per day
Abstract 1

Assessment of Water Quality, Road Runoff, and 

Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, 

Water Years 1995–97

By Michael R. Stevens

Abstract

The Guanella Pass road, located about 

40 miles west of Denver, Colorado, between the 

towns of Georgetown and Grant, has been designated a scenic byway and is being considered for 

reconstruction. The purpose of this report is to 

present an assessment of hydrologic and waterquality conditions in the Guanella Pass area and 

provide baseline data for evaluation of the effects 

of the proposed road reconstruction. The data 

were collected during water years 1995–97 

(October 1, 1995, to September 30, 1997).

Based on Colorado water-quality standards, 

current surface-water quality near Guanella Pass 

road was generally acceptable for specified use 

classifications of recreation, water supply, agriculture, and aquatic life. Streams had small 

concentrations of dissolved solids, nutrients, 

trace elements, and suspended sediment. An 

exception was upper Geneva Creek, which was 

acidic and had relatively large concentrations 

of iron, zinc, and other trace elements related to 

acid-sulfate weathering. Concentrations of many 

water-quality constituents, especially particlerelated phases and suspended sediment, increased 

during peak snowmelt and rainstorm events and 

decreased to prerunoff concentrations at the end 

of runoff periods. Some dissolved (filtered) traceelement loads in Geneva Creek decreased during 

rainstorms when total recoverable loads remained 

generally static or increased, indicating a phase 

change that might be explained by adsorption 

of trace elements to suspended sediment during 

storm runoff.

Total recoverable iron and dissolved zinc 

exceeded Colorado stream-water-quality standards most frequently. Exceedances for iron 

generally occurred during periods of high 

suspended-sediment transport in several streams. 

Zinc standards were exceeded in about one-half 

the samples collected in Geneva Creek 1.5 miles 

upstream from Grant.

Lake-water quality was generally similar 

to that of area streams. Nitrogen and phosphorus 

ratios calculated for Clear and Duck Lakes indicated that phytoplankton in the lakes were 

probably phosphorus-limited. Measures of 

trophic status (secchi depth, total phosphorus, 

and chlorophyll-a) indicated that Duck and Clear 

Lakes were oligotrophic in 1997.

Ground water had relatively low specific 

conductance (range 24 to 584 microsiemens per 

centimeter) and did not exceed U.S. Environmental 

Protection Agency drinking-water standards, 

except for samples collected from a single well, 

which exceeded the Proposed Maximum Contaminant Level for uranium.

Runoff from the Guanella Pass road enters 

streams through surface channels connected to 

culverts and roadside ditches. Fifty-six percent 

of the total number of culvert and roadsideditch drainage features on the Guanella Pass 
2 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

road showed evidence of recent surface runoff 

connection to an adjacent stream. Road runoff 

is generated during snowmelt and during summer 

rainstorms. 

At a road cross-drain culvert monitored 

continuously for discharge (water years 

1996–97), most runoff (77 to 96 percent) was 

a result of snowmelt, and runoff from the road 

preceded the basinwide peak streamflow, 

resulting in sediment and water-quality constituent inputs to the stream when the stream’s 

capacity for dilution of the road runoff was low. 

Specific conductance of road-runoff samples 

ranged from 14 to 468 microsiemens per centimeter. Major-ion composition of some samples 

indicated effects from deicing salt (sodium chloride) and dust inhibitor (magnesium chloride) 

applied to sections of the road, but changes in the 

stream concentrations that might be attributed to 

the runoff were brief and relatively small.

Nutrients were commonly measured in 

road-runoff samples at larger concentrations 

than in streamflow. Concentrations of nitrate and 

ammonia, especially during rainfall-generated 

road runoff, were more similar to the concentrations in precipitation than to the concentrations 

in stream water. Concentrations of ammonia plus 

organic nitrogen (total as N) (range less than 0.2 

to 24 milligrams per liter) and total phosphorus 

(range 0.024 to 7.2 milligrams per liter) in road 

runoff were generally large in snowmelt and rainstorm samples and were related to abundant 

particulate organic material and suspended sediment in the road runoff.

Trace-element data indicated that total 

recoverable trace-element concentrations in road 

runoff were substantially larger (by several times) 

than dissolved trace-element concentrations, indicating that most trace elements were particulate. 

Most of the stream trace-element standards would 

not likely be exceeded as a result of road-runoff 

constituents discharged into streams because 

the standards apply primarily to dissolved-phase 

(filtered) constituents, and the predominant phase 

associated with Guanella Pass road runoff is 

particulate. 

The suspended-sediment concentrations 

in snowmelt-generated road runoff ranged from 

66 to 7,360 milligrams per liter. Rainstorm-runoff 

concentrations ranged from 34 to 38,800 milligrams per liter. The sediment was primarily fine 

grained, which facilitated transport of the sediment. The median percentage of silt and clay 

(finer than 0.062 millimeter) in road-runoff 

samples analyzed for size fractions was greater 

than 90 percent for snowmelt samples and 

88 percent for rainstorm samples.

Dilution of estimated road runoff to South 

Clear Creek upstream from Naylor Creek as a 

result of snowmelt on the road in early May 

(prior to peak watershed streamflows) ranged 

from approximately 10 to 100 times. During peak 

snowmelt in the watershed (early June), dilution 

of road runoff was estimated to be greater than 

1,000 times. Dilution factors for late-summerrainstorm road runoff were in the range of 10 

to 500 times. Given the large concentrations of 

suspended sediment in road runoff, the potential 

water-quality effects of road runoff could be 

substantial during the low streamflows of early 

snowmelt and late summer base flow (low dilution capacity) but inconsequential during high 

streamflows (high dilution capacity).

The median bulk deposition rate of filterable solids is probably related to dust deposition 

from roads. The median deposition rate at sites 

near unpaved roads was 105 times the median rate 

at an undisturbed reference site (located at least 

500 feet away from a road), and the rate at sites 

near paved roads was 3 times the undisturbed 

reference site median rate. During August to 

September 1997, bulk atmospheric deposition 

directly on the active channel of a reach of 

Geneva Creek was estimated to be 1.7 tons, or 

about 1 percent of the estimated 165 tons of 

suspended sediment transported past the nearby 

stream-monitoring site near Grant during the 

same period. The estimate of 1.7 tons indicates 

little potential effect from direct settling of bulk 

atmospheric solids on suspended-sediment transport in Geneva Creek, a stream that closely parallels the Guanella Pass road.
INTRODUCTION 3

INTRODUCTION

The Guanella Pass road between Georgetown 

and Grant, Colo. (fig. 1), has been designated a scenic 

byway and is being considered for reconstruction. The 

mountainous area along the road is drained by South 

Clear Creek north of the pass and by Geneva Creek 

south of the pass (fig. 1). The area drained by these 

two streams and their tributaries is an important 

natural area that is used for clean-water supplies, 

recreation, and wildlife habitat.

The existing road was constructed during the 

1950’s and 1960’s. The road consists of a series of 

paved and unpaved (dirt and gravel) sections, with 

road cuts and fills that were left to revegetate naturally. 

The proposed road reconstruction has several alternatives ranging from complete reconstruction and paving 

to leaving the road in the present form (Federal 

Highway Administration, 1993). The proposed road 

reconstruction may add new features, such as new 

asphalt paving, retaining walls, changes in drainage 

features, and revegetated slopes. The reconstruction 

of the Guanella Pass road may affect the chemical 

quality and sediment loading of the adjacent streams. 

However, an erosion-resistant road surface, engineered drainage system, and revegetation efforts might 

reduce the long-term amount of eroded sediment in the 

streams.

To characterize existing conditions and provide 

a basis for evaluation of the effects of the proposed 

road reconstruction, the U.S. Geological Survey 

(USGS), in cooperation with the Federal Highway 

Administration (FHWA) and Clear Creek County, 

conducted a study during water years (WY) 1995–97 

(October 1, 1995, to September 30, 1997).

Purpose and Scope

The purpose of this report is to present an 

evaluation of hydrologic and water-quality conditions 

in the Guanella Pass area based on the data collected 

during water years 1995–97. Objectives of the study 

are to (1) describe existing hydrology, water quality, 

suspended sediment, and dust conditions in the 

Guanella Pass road area; (2) collect sufficient data 

for comparison of conditions during the preconstruction period to the construction and postconstruction 

periods if the road is reconstructed; and (3) assess 

general effects of the present road on hydrology, 

water quality, sediment, and dust.

Seventy-seven sites were established in the 

study area to facilitate hydrologic characterization 

of streams, lakes and reservoirs, ground water, road 

runoff, and bulk deposition related to the current road. 

Data were collected mostly in the South Clear Creek 

and Geneva Creek Basins, although sites in the West 

Chicago Creek and Deer Creek Basins were added as 

undisturbed reference sites.

This report focuses on documenting and 

describing the water resources (streams, lakes and 

reservoirs, and ground water) in the study area in 

terms of onsite measurements, concentrations of major 

and trace constituents, nutrients, and suspended sediment and compares water quality to applicable standards and guidelines. In the “Characterization of 

Guanella Pass Road Runoff” sections of the report, 

background information, chemical and sediment characteristics, sources, delivery to streams, and some 

potential effects of road runoff on water resources 

are discussed. In the “Bulk Atmospheric Deposition” 

sections, effects of road-surface type, distribution 

characteristics, and estimates of bulk atmosphericdeposition contributions from an unpaved road 

to a stream are discussed.

Acknowledgments

The assistance of others during this study was 

invaluable. The author thanks Historic Georgetown, 

Inc., Public Service Company of Colorado, William 

and Julia Holmes, Clear Creek and Park Counties, and 

the U.S. Department of Agriculture Forest Service for 

access to property for sampling and installation of 

equipment.

DESCRIPTION OF STUDY AREA

The Guanella Pass road, located approximately 40 miles west of Denver, Colo. (fig. 1), 

connects U.S. Interstate 70 at Georgetown with 

U.S. Highway 285 at Grant. The northern 13.1 miles 

is known as Clear Creek County Road 381, and the 

southern 10.4 miles is known as Park County Road 62 

(Federal Highway Administration, 1993). The road 

ranges in altitude from about 8,600 ft at Georgetown 

and Grant to 11,699 ft at the top of the pass and consists 

of several paved and unpaved sections; the paved 

sections total 11.4 miles and the unpaved sections total 

12.1 miles (Federal Highway Administration, 1993).
4 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Georgetown

Grant

Threemile

Creek

Geneva

Creek

Scott Gomer Creek

Duck Lake

Square Top

Lakes

Geneva 

Creek

Upper Cabin

Creek Reservoir

Lower Cabin

Creek Reservoir

Georgetown

Reservoir

Leavenworth 

Creek

South Clear Creek

Clear Lake

Vidler

Tunnel

Green

Lake

West Chicago Creek

Bruno Gulch

GC5

GC4

GC2

GC3

CC1

CC2

CC12

CC3

CC13

CC8

GC1

GC7

GC6

GC8

CC1

GC11

GC12

GC8

GC10

DC1

GC9

CC5 

CC4 

CC6 

CC11 

CC7

Mount

Evans Mount

Bierstadt

Guanella

Pass

285

105°45'

39°30'

105°45'

39°30'

Waldorf

Mine

Scott

Gomer

Creek

Kirby Gulch

Burning Bear

Creek

CLEAR CREEK 

COUNTY

PARK COUNTY

70

North Fork South Platte

CC9

CC10

0

0

1

1

2

2

3 MILES

3 KILOMETERS

SUMMIT

CO

U

NTY

PARK

CO

UNTY

381

62

EXPLANATION

WATER– OR SEDIMENT–QUALITY

SAMPLING SITE—Number refers 

 to site number in table 1

Paved road

Unpaved road

Unimproved road

Continental Divide

Study area boundary

Mount Evans wilderness boundary

Base from U.S. Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 37°30' and 40°30'

Central meridian 37°00'

CONTINENTAL

DIVIDE

WATER–QUALITY SAMPLING SITE

AND CONTINUOUS WATER 

TEMPERATURE

CC2 WATER–QUALITY, CONTINUOUS

STREAMFLOW, WATER TEMPERATURE,

SPECIFIC CONDUCTANCE, 

SUSPENDED–SEDIMENT DISCHARGE,

AND PUMPING SAMPLER

Creek

Naylor

Duck Creek

Deer

Creek

Cañon

City

Grand 

Junction

SOUTH PLATTE RIVER

DENVER Study

area

COLORADO 

GUNNISON RIVER

COLORAD O RIVER

YAMPA 

RIVER

Figure 1. Location of Guanella Pass study area and stream data-collection sites.
MONITORING NETWORK AND QUALITY ASSURANCE 5

The road section in Clear Creek County (fig. 1) 

is maintained year round; the road section in Park 

County is not maintained in winter but seldom is 

impassable. In Clear Creek County, a salt (sodium 

chloride) and sand mixture is applied to road sections 

in winter, and a magnesium chloride dust inhibitor 

is sometimes applied to unpaved road sections 

(Jim Cannedy, Clear Creek County, oral commun., 

1997).

The study area includes the watersheds of South 

Clear Creek and Geneva Creek and part of the West 

Chicago Creek and Deer Creek watersheds (which do 

not drain areas along the Guanella Pass road). The 

Guanella Pass road parallels South Clear Creek from 

the pass to Georgetown; south of the pass, the road 

parallels Duck and Geneva Creeks to the southern 

terminus at Grant. The Continental Divide forms 

the western boundary of the study area, and the 

eastern one-half of the study area includes the Mount 

Evans Wilderness Area. Annual precipitation in the 

study area ranges from about 12 to 16 inches near 

Georgetown and Grant to about 40 to 50 inches in the 

higher mountains (Colorado Climate Center, 1984). 

Vegetation includes conifer and aspen forest at low 

altitudes and alpine tundra above timberline, which 

is about 11,500 ft. 

Precambrian granite, gneiss, and schist compose 

the bedrock in the study area. Geology consists mainly 

of these three bedrock types; most basins have a mix 

of two or all three (Tweto, 1979). The metamorphic 

rocks are metasediments (metamorphic rock related 

to sedimentary parent material) and metavolcanics 

(metamorphic rock related to volcanic parent 

material). Both rock types are gneissic and are 

different mainly in the mafic mineral composition. 

Both rock types also are intruded and partly melted by 

granite from a large intrusion centered in the Mount 

Evans area. Small intrusions of Tertiary age in the 

headwaters of Geneva and Leavenworth Creeks 

cover a relatively small area. 

Glaciers deposited drift in the valleys of Duck, 

Geneva, and South Clear Creeks (Tweto, 1979). The 

drift composes substantial portions of many of the 

unconsolidated deposits in the valleys. Armoring 

of the streambed by cobbles and boulders seems to 

reduce active channel erosion of the glacial drift. 

Many area lakes were created as a result of glacial 

activity. 

Ore deposits were mined near the headwaters 

of Geneva and Leavenworth Creeks. These areas are 

known as the Geneva Creek and Argentine Districts 

(Davis and Streufert, 1990). Naturally occurring 

pyritic components of the intrusive rocks and mineral 

deposits become oxidized and produce acidic and 

mineralized ground water and surface water in the 

upper basin of Geneva Creek (Bassett and others, 

1992) and Leavenworth Creek. This process is 

referred to as acid-sulfate weathering.

The primary land use is recreation. Most of 

the study area is managed by the U.S. Department 

of Agriculture, Forest Service (Forest Service). The 

Forest Service maintains five campgrounds in the area, 

two on the South Clear Creek side and three on the 

Geneva Creek side of Guanella Pass. Dispersed 

camping along the roadside is popular. Some livestock 

grazing occurs in the Geneva, Scott Gomer, and Duck 

Creek drainages. Although there was substantial 

logging in the area in the past (Nichols, 1992), there 

are no current (1999) logging operations. A few residences, some seasonal, are located at Duck and Naylor 

Lakes and along Duck, Geneva, and lower South Clear 

Creeks. 

The Vidler Tunnel (fig. 1) diverts water from 

upper Peru Creek across the Continental Divide into 

the Leavenworth Creek Basin for downstream use. 

The Roberts Tunnel, a transmountain diversion of 

water from Dillon Reservoir to the North Fork of the 

South Platte River near Grant, conducts flows beneath 

the southwest corner of the study area. An aqueduct 

diverts water from Leavenworth Creek on a seasonal 

basis to maintain the water level in Green Lake, which 

is not located on a stream. Some of the natural lakes, 

such as Duck Lake, have been modified for increased 

storage by the construction of small dams. The Public 

Service Company of Colorado operates two reservoirs 

(Upper and Lower Cabin Creek Reservoirs) in the 

South Clear Creek Basin for a pumped-storage hydroelectric facility. Water is diverted from South Clear 

Creek at Georgetown Reservoir for drinking-water 

treatment and hydroelectric power generation in 

Georgetown.

MONITORING NETWORK AND QUALITY 

ASSURANCE

Seventy-seven sites were established in the 

study area for hydrologic characterization of streams, 

lakes and reservoirs, ground water, and road runoff 

and bulk deposition related to the current road. Data 

were collected mostly in the South Clear Creek and 
6 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Geneva Creek Basins, although sites in the West 

Chicago Creek (CC11) and Deer Creek (DC1) Basins 

were added as additional undisturbed reference sites. 

The locations of all sites are shown in figures 1–3, 

and the site names and identification numbers are 

listed in table 1. Data collected for the study period 

also are compiled in Stevens and others (1997), 

Stevens (1999), Stevens (2000), and Cox-Lillis (2000).

Continuous records of discharge, water temperature, specific conductance, and suspended sediment 

were collected at seven sites on perennial streams. 

These sites (CC2, CC5, CC7, CC9, GC5, GC11, and 

DC1) provided seasonal perspective and allowed 

computation of annual means and loads that can be 

used for comparisons between sites and between years 

at the same site.

Samples for surface-water quality were 

collected at 26 sites in WY’s 1995–97. In WY 1995, 

many sites were sampled at a reconnaissance level 

during high flow and low flow to determine the location of future sampling efforts. In WY’s 1996–97, the 

number of analytes was reduced along with the 

number of sites. Selected continuous-record sites 

(CC2, CC5, GC5, GC11, and DC1) were sampled 

approximately 20 times per year during the openwater season—approximately weekly from May 

through June and biweekly from July through August. 

A few samples were collected during low flow and 

storm runoff each year. Stream sites sampled for 

macroinvertebrates and algae (periphyton) are 

described in Cox-Lillis (2000). Water samples at 

these biological sites were collected at high flow and 

low flow in WY’s 1996–97 to characterize variability 

of water quality. 

Water-quality samples, onsite-measurement 

profiles, and(or) bottom-sediment samples were 

collected from six lakes and reservoirs (fig. 2). In 

WY 1995, four lakes or reservoirs (L1, L2, L3, 

and L4) were sampled once for water chemistry in 

August. In WY 1996, L1 and L3 were sampled once 

for water chemistry during late summer. In WY 1997, 

L1 and L3 were sampled at least six times. Bottomsediment chemical samples were collected each year 

from L1 and L3; one bottom-sediment chemical 

sample was collected during the study at L2, L4, 

L5, and L6.

Samples to assess ground-water quality were 

collected at 15 springs or wells (fig. 3). A single water 

sample was collected at campground wells and springs 

near the road to indicate the quality of water used for 

drinking and to indicate whether road-runoff chemical 

effects might be observed in sources near the road. 

Road-runoff samples were collected at 17 sites 

(fig. 2) during WY’s 1995–97, mostly at cross-drain 

culverts or ditches at the roadside. Two chemical 

samples of full-depth composites of maximumaccumulation snowpack were collected in March 

(fig. 2) during WY’s 1995–97.

Bulk atmospheric-deposition samples were 

collected at 15 sites (fig. 3) during WY’s 1995–97. 

Differences in deposition between paved and unpaved 

road sites were assessed at 12 sites in August and 

September 1995. Site G was sampled intensively in 

August and September 1996 to assess deposition characteristics. Sites L, M, and N were sampled in August 

and September 1997 to compute an estimate of bulk 

deposition contributions to the active channel of 

Geneva Creek.

The types of hydrologic and water-quality

data collected from streams, lakes, reservoirs, 

ground water, and road runoff in WY 1995 are onsite 

measurements (water discharge, water temperature, 

specific conductance, pH, turbidity, and dissolved 

oxygen); concentrations of major ions and dissolved 

solids (calcium, magnesium, sodium, potassium, alkalinity, sulfate, chloride, fluoride, silica, and dissolvedsolids residue); nutrients (nitrogen and phosphorus 

compounds); trace elements (cadmium, copper, iron, 

lead, manganese, mercury, and zinc); organic carbon; 

and suspended sediment. These data, the methods of 

data collection, and quality assurance are listed and 

described in Stevens and others (1997) and Stevens 

(2000).

Replicate and equipment blank samples were 

obtained for quality-assurance purposes. Replicate 

samples were collected to determine sampling and 

analytical precision. Replicates were obtained by 

collecting an extra sample immediately after the 

first sample. Field blank samples were collected to 

determine if field sampling and processing equipment 

biased constituent concentration through contamination; laboratory bias also is included in the results of a 

field blank. Field blanks were prepared by using certified inorganic and organic blank water that was passed 

through the sampling equipment and processed as a 

regular sample. 

Percentiles of relative percent difference 

(RPD) were computed for replicate samples. Median 

concentrations are reported for field blanks in table 2. 

The replicate data indicate generally reproducible 

analytical results. Median RPD’s ranged from 0 to 
MONITORING NETWORK AND QUALITY ASSURANCE 7

Georgetown

Grant

Threemile

Creek

Geneva

Creek

Scott Gomer Creek

Duck Lake

Square Top

Lakes

Geneva 

Creek

Upper Cabin

Creek Reservoir

Lower Cabin

Creek Reservoir

Georgetown

Reservoir

Leavenworth 

Creek

South Clear Creek

Clear Lake

Green

Lake

West Chicago Creek

Bruno Gulch

L3

GRD8

Guanella

Pass

285

105°45'

39°30'

105°45'

39°30'

Waldorf

Mine

Scott

Gomer

Creek

Kirby Gulch

Burning Bear

Creek

CLEAR CREEK 

COUNTY

PARK COUNTY

70

North Fork South Platte

CRD9

CRD8

CRD6

CRD4

CRD3

CRD7

CRD1

GRD1

CRD2

GRD2

GRD3

GRD4

GRD7

GRD5

GRD8

SN1

GRD6

SN2

L6

L4

L2

L5

L1

L3

0

0

1

1

2

2

3 MILES

3 KILOMETERS

SUMMIT

CO

U

NTY

PARK

CO

UNTY

381

62

EXPLANATION

LAKE/RESERVOIR SAMPLING

SITE—Letter refers 

 to site number in table 1

Paved road

Unpaved road

Unimproved road

Continental Divide

Study area boundary

Base from U.S. Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 37°30' and 40°30'

Central meridian 37°00'

CONTINENTAL

DIVIDE

ROAD-RUNOFF WATER-QUALITY

SAMPLING SITE

CRD7

SN1

ROAD-RUNOFF WATER-QUALITY

AND CONTINUOUS STREAMFLOW

SAMPLING SITE WITH PUMPING

SAMPLER

SNOW-SAMPLING SITE

Creek

Naylor

Duck Creek

Deer

Creek

Mount

Evans

Mount

Bierstadt

Cañon City

Grand 

Junction

SOUTH

PLATTE RIVER

DENVER Study

area

COLORADO 

GUNNISON RIVER

COLORAD O RIVER

YAMPA 

RIVER

Figure 2. Location of lake, reservoir, road-runoff, and snow-sampling sites.
8 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Georgetown

Grant

Threemile

Creek

Geneva

Creek

Scott Gomer Creek

Duck Lake

Square Top

Lakes

Geneva 

Creek

Upper Cabin

Creek Reservoir

Lower Cabin

Creek Reservoir

Georgetown

Reservoir

Leavenworth 

Creek

South Clear Creek

Clear Lake

Green

Lake

West Chicago Creek

Bruno Gulch

M

GW3

Guanella

Pass

285

105°45'

39°30'

105°45'

39°30'

Waldorf

Mine

Scott

Gomer

Creek

Kirby Gulch

Burning Bear

Creek

CLEAR CREEK 

COUNTY

PARK COUNTY

70

North Fork South Platte

GW1

GW2

GW3 GW13 GW4

GW5

GW9

GW6

GW11

GW15

GW12

GW7

GW8

GW14

GW10

0

0

1

1

2

2

3 MILES

3 KILOMETERS

SUMMIT

CO

U

NTY

PARK

CO

UNTY

381

62

EXPLANATION

GROUND-WATER SAMPLING

SITE—Letter refers to site number

in table 1

Paved road

Unpaved road

Unimproved road

Continental Divide

Study area boundary

Base from U.S. Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 37°30' and 40°30'

Central meridian 37°00'

CONTINENTAL

DIVIDE

BULK ATMOSPHERIC-DEPOSITION 

SAMPLING SITE

Creek

Naylor

Duck Creek

Deer

Creek

C

D

L

M

A

B N

F

E

G

H

K

J

Mount

Evans Mount

Bierstadt

Cañon City

Grand 

Junction

SOUTH PLATTE RIVER

DENVER Study

area

COLORADO 

GUNNISON RIVER

COLORAD O RIVER

YAMPA

RIVER

Figure 3. Location of ground-water and bulk atmospheric-deposition sampling sites.
MONITORING NETWORK AND QUALITY ASSURANCE 9

Table 1. Data-collection sites

Site number

(figs. 1–3)

U.S. Geological Survey

identification number Site name

CC1 393606105422118 South Clear Creek near Guanella Pass

CC2 393647105425317 South Clear Creek above Naylor Creek near Georgetown

CC3 393642105430416 Naylor Creek at mouth near Georgetown

CC4 393804105423413 South Clear Creek below Naylor Creek near Georgetown

CC5 06714400 South Clear Creek above Lower Cabin Creek Reservoir near Georgetown

CC6 393946105422203 South Clear Creek above Clear Lake near Georgetown

CC7 06714600 South Clear Creek above Leavenworth Creek near Georgetown

CC8 393819105452801 Leavenworth Creek above Waldorf Mine near Georgetown

CC9 06714800 Leavenworth Creek at mouth near Georgetown

CC10 394211105414100 South Clear Creek at Georgetown

CC11 394027105393900 West Chicago Creek near Idaho Springs

CC12 393619105423700 South Clear Creek above Naylor Creek at upper station near Georgetown

CC13 393649105425301 South Clear Creek near Guanella Pass Campground near Georgetown

GC1 393504105432312 Duck Creek above Duck Lake West Branch near Grant

GC2 393458105431511 Duck Creek above Duck Lake East Branch near Grant

GC3 393433105433210 Duck Creek below Duck Lake near Grant

GC4 393243105430814 Duck Creek above Mill Gulch near Grant

GC5 06704500 Duck Creek near Grant

GC6 393348105460415 Geneva Creek above Smelter Gulch near Grant

GC7 393153105440109 Geneva Creek above Duck Creek near Grant

GC8 393141105445808 Bruno Gulch above Geneva Park near Grant

GC9 393018105421707 Geneva Creek above Scott Gomer Creek near Grant

GC10 393028105421706 Scott Gomer Creek at mouth near Grant

GC11 06705500 Geneva Creek at Grant

GC12 392735105394705 Geneva Creek near Grant

DC1 393040105340400 Deer Creek near Bailey

GW1 393944105422500 Lower Cabin Creek Reservoir Dam spring

GW2 393904105422800 Clear Lake Campground well

GW3 393644105430400 Guanella Pass Campground west well

GW4 393638105425900 Guanella Pass Campground east well

GW5 393620105423900 Guanella Pass spring #1

GW6 393439105434200 Duck Lake spring

GW7 393052105423300 Burning Bear Campground well

GW8 392853105405800 Whiteside Campground well

GW9 393610105423900 Guanella Pass spring #2 near Georgetown

GW10 393616105423400 Guanella Pass spring #3 near Georgetown

GW11 393342105424800 Guanella Pass spring #4 near Grant

GW12 393335105431500 Guanella Pass spring #6 near Grant

GW13 393627105421800 Guanella Pass spring #7 near Grant

GW14 393036105340100 Deer Creek spring #1 near Bailey

GW15 393145105435300 Duck Creek Picnic Ground well near Grant

L1 393454105432900 Duck Lake near Grant

L2 393937105423900 Lower Cabin Creek Reservoir near Georgetown

L3 394011105425700 Clear Lake near Georgetown

L4 394032105421700 Green Lake near Georgetown

L5 393527105441900 Lower Square Top Lake near Grant

L6 394128105415300 Georgetown Reservoir near Georgetown
10 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

29 percent. Many of the larger RPD’s are due to 

concentrations or values near the minimum reporting 

level (MRL), a range in which precision is expected 

to be poor. In these cases, concentrations may differ 

little but result in large RPD’s. For example, a sample 

with a concentration of 0.01 mg/L and a replicate 

concentration of 0.02 mg/L would result in an RPD 

of 67 percent, but the difference might be considered 

to be within the precision of the method at that 

concentration. Data for individual replicate pairs and 

analytes, which are listed in Stevens (2000), can help 

determine if large RPD’s are the result of substantial 

differences between replicate sample concentrations.

Median values or concentrations of field blanks 

indicated no substantial or systematic contamination 

bias during collection and processing of samples. 

Median concentrations for five analytes (table 2) 

were above the laboratory MRL (calcium, dissolved 

ammonia, dissolved aluminum, total organic carbon, 

and dissolved organic carbon). Calcium concentrations in blanks were far below most stream concentrations (median blank concentration was less than 

10 percent of median stream concentrations, 

tables 34–47 in Appendix). Contamination bias 

in the other four analytes could affect the data in 

some samples containing small concentrations of 

those analytes.

CRD1 393612105423800 Road ditch below Guanella Pass

CRD2 393602105423000 Road ditch near Guanella Pass

CRD3 393643105430200 Road ditch at Naylor Creek near Georgetown

CRD4 393643105425200 Road ditch above Lower Cabin Creek Reservoir near Georgetown

CRD5 393859105422700 Road ditch above Clear Lake Campground near Georgetown

CRD6 394036105415900 Road ditch below Green Lake near Georgetown

CRD7 393618105424200 Guanella Pass culvert #1 near Georgetown

CRD8 394043105420200 Guanella Pass culvert #4 near Georgetown

CRD9 394211105414300 Road ditch above Georgetown

GRD1 393516105430700 Road ditch near Duck Lake near Grant

GRD2 393506105430600 Road ditch above Duck Lake near Grant

GRD3 393309105430200 Road ditch near Geneva Mountain near Grant

GRD4 393244105430800 Road ditch below Duck Lake

GRD5 393152105434700 Road ditch below Mill Gulch near Grant

GRD6 393508105430600 Guanella Pass culvert #2 near Grant

GRD7 393243105430800 Campsite road runoff #1 near Grant

GRD8 393444105444100 Road ditch near Grant

A 392813105403200 Grant road site (bulk deposition) near Grant

B 392822105410600 Grant reference site (bulk deposition) near Grant

C 393152105434701 Road site below Mill Gulch (bulk deposition) near Grant

D 393300105431100 Road site above Mill Gulch (bulk deposition) near Grant

E 393413105432700 Geneva Basin Ski Area road site (bulk deposition) near Grant

F 393506105430601 Road site above Duck Lake (bulk deposition) near Grant

G 393516105430701 Road site near Duck Lake (bulk deposition) near Grant

H 393612105423801 Road site below Guanella Pass (bulk deposition) near Georgetown

J 394113105420000 Road site above Georgetown Reservoir (bulk deposition) near Georgetown

K 394116105414900 Clear Creek reference site (bulk deposition) near Georgetown

L Geneva Creek bulk deposition site L near Grant

M Geneva Creek bulk deposition site M near Grant

N Geneva Creek bulk deposition site N near Grant

Table 1. Data-collection sites—Continued

Site number

(figs. 1–3)

U.S. Geological Survey

identification number Site name
MONITORING NETWORK AND QUALITY ASSURANCE 11

Table 2. Summary of quality-assurance data, water years 1995–97

[mg/L, milligrams per liter; μg/L, micrograms per liter; --, no data; <, less than minimum reporting level; *, concentration in blank exceeds the laboratory 

minimum reporting level]

Property Units Number

of pairs

Replicates

(relative percent difference) Blanks

10th

percentile

50th

percentile

90th

percentile

Number

of blanks

Median

concentration

Calcium, dissolved mg/L 4 0 0.7 1.5 8 *0.02

Magnesium, dissolved mg/L 4 0 0 0 8 <.01

Sodium, dissolved mg/L 4 0 0 0 8 <.02

Potassium, dissolved mg/L 4 0 0 0 4 <.1

Sulfate mg/L 6 0 0 5.0 6 <.1

Chloride mg/L 6 0 0 93 6 <.1

Fluoride mg/L 1 -- 0 -- 2 <.1

Silica mg/L 4 0 0 1.0 8 <.02

Dissolved solids, residue at 180 degrees Celsius mg/L 4 3.9 12 43 4 <1

Nitrogen, nitrite, dissolved as N mg/L -- -- -- -- 4 <.01

Nitrogen, nitrite plus nitrate, dissolved as N mg/L 7 0 4.9 13 9 <.05

Nitrogen, ammonia, dissolved as N mg/L 5 0 0 0 7 *.004

Nitrogen, ammonia plus organic, dissolved as N mg/L -- -- -- -- 1 <.2

Nitrogen, ammonia plus organic, total as N mg/L 7 0 0 16 5 <.2

Phosphorus, total as P mg/L 7 0 29 81 5 <.001

Phosphorus, dissolved as P mg/L -- -- -- -- 2 <.01

Phosphorus, dissolved orthophosphate as P mg/L 5 0 0 0 7 <.01

Aluminum, total recoverable as Al μg/L -- -- -- -- 1 <10

Aluminum, dissolved as Al μg/L -- -- -- -- 5 *.8

Antimony, dissolved as Sb μg/L -- -- -- -- 5 <1

Arsenic, total recoverable as As μg/L -- -- -- -- 1 <1

Barium, total recoverable as Ba μg/L -- -- -- -- 1 <100

Barium, dissolved as Ba μg/L -- -- -- -- 5 <1

Beryllium, total recoverable as Be μg/L -- -- -- -- 1 <10

Beryllium, dissolved as Be μg/L -- -- -- -- 5 <1

Cadmium, total recoverable as Cd μg/L -- -- -- -- 1 <1

Cadmium, dissolved as Cd μg/L -- -- -- -- 5 <1

Chromium, total recoverable as Cr μg/L -- -- -- -- 1 <1

Chromium, dissolved as Cr μg/L -- -- -- -- 5 <1

Cobalt, total recoverable as Co μg/L -- -- -- -- 1 <1

Cobalt, dissolved as Co μg/L -- -- -- -- 5 <1

Copper, total recoverable as Cu μg/L 6 0 9 100 6 <1

Copper, dissolved as Cu μg/L 6 0 0 54 10 <1

Iron, total recoverable as Fe μg/L 6 3.3 12 31 6 <10

Iron, dissolved as Fe μg/L 6 .5 6.4 21 10 <3

Lead, total recoverable as Pb μg/L 6 0 0 0 6 <1

Lead, dissolved as Pb μg/L 2 0 0 0 6 <1

Manganese, total recoverable as Mn μg/L 6 0 0 43 6 <10

Manganese, dissolved as Mn μg/L 6 0 0 3.8 10 <1

Mercury, total recoverable as Hg μg/L -- -- -- -- 1 <.1

Molybdenum, total recoverable as Mo μg/L -- -- -- -- 1 <1
12 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

CHARACTERIZATION OF WATER 

RESOURCES

Characterization of existing water resources

was necessary to document baseline preconstruction hydrologic and water-quality conditions and 

to provide a basis for evaluating possible effects 

of road runoff on the water resources. Information 

about precipitation, streams, lakes and reservoirs, 

and ground water in WY’s 1995–97 was collected.

Precipitation

Precipitation in the study area falls primarily 

as snow during October through May. Short, locally 

intense thunderstorms occur in summer but usually 

cause only minor, short-duration rises in stream 

stage. Storm runoff from rainfall contributes relatively 

little to the total annual flow in streams and produces 

peak flows that are small compared to snowmelt peak 

flows. Average annual precipitation differs with 

altitude and position relative to major topographic 

features like the Continental Divide and Mount Evans. 

Average annual precipitation ranges from 12 to 

16 inches near Georgetown and Grant, and 40 to 

50 inches on Mount Evans and the Continental 

Divide (Colorado Climate Center, 1984). 

Rainfall data were collected seasonally 

(April or May to September) by tipping-bucket 

recorders at streamflow gages, primarily for the 

purpose of activating storm-sampling equipment and 

for interpretation of water-quality data. The rainfall 

data indicate that 30 to 50 or more days with measurable rain can be expected from June to August each 

year. Rainstorms usually occur during afternoon to 

early morning. Daily precipitation seldom exceeded 

0.5 inch but can exceed 1.5 inches (Stevens and 

others, 1997; Stevens, 2000). Measured precipitation 

totals in April, May, or September can be rain, melted 

snow, or both, depending upon air temperature. This 

can be important because raindrops have more erosive 

power than snow and cause faster surface-runoff 

response during a storm.

Snowpack chemical quality was analyzed 

once each year near the end of the snow accumulation season and before spring melting began (end of 

March) at two sites, one in South Clear Creek Basin 

(SN2) and one in Duck Creek Basin (SN1) (fig. 2). 

Because most of the water in the study area begins 

as snow, the chemical character of the snowpack 

is a useful initial geochemical baseline for the interpretation of water quality. In general, runoff derived 

from melted snow in the study area is dilute and 

slightly acidic (Stevens and others, 1997; Stevens, 

Molybdenum, dissolved as Mo μg/L -- -- -- -- 5 <1

Nickel, total recoverable as Ni μg/L -- -- -- -- 1 <1

Nickel, dissolved as Ni μg/L -- -- -- -- 5 <1

Selenium, total recoverable as Se μg/L -- -- -- -- 1 <1

Silver, total recoverable as Ag μg/L -- -- -- -- 1 <1

Silver, dissolved as Ag μg/L -- -- -- -- 5 <.2

Zinc, total recoverable as Zn μg/L 6 0 0 0 6 <10

Zinc, dissolved as Zn μg/L 6 0 13 54 10 <3

Uranium, natural, dissolved μg/L -- -- -- -- 6 <1

Carbon, organic, total as C mg/L -- -- -- -- 1 *.4

Carbon, organic, dissolved as C mg/L -- -- -- -- 3 *.4

Table 2. Summary of quality-assurance data, water years 1995–97—Continued

[mg/L, milligrams per liter; μg/L, micrograms per liter; --, no data; <, less than minimum reporting level; *, concentration in blank exceeds the laboratory 

minimum reporting level]

Property Units Number

of pairs

Replicates

(relative percent difference) Blanks

10th

percentile

50th

percentile

90th

percentile

Number

of blanks

Median

concentration
CHARACTERIZATION OF WATER RESOURCES 13

2000). Specific conductance was generally less than 

10 μS/cm, and pH ranged from 4.9 to 6.9. Major 

ion concentrations were small; calcium was the 

predominant cation, and sulfate was the predominant 

anion. Dissolved ammonia concentrations were generally less than 0.1 mg/L as N, dissolved nitrate concentrations were less than 0.20 mg/L as N, and dissolved 

orthophosphate concentrations were less than 

0.02 mg/L as P. Aluminum, iron, manganese, and zinc 

were detected at small concentrations in the dissolved 

phase (less than 12 μg/L) (Stevens and others, 1997; 

Stevens, 2000).

Rainfall chemical quality was not analyzed 

in the study area, but regional precipitation quality 

is monitored by the National Atmospheric Deposition 

Program/National Trends Network (NADP/NTN) 

at several sites along the Colorado Front Range 

and is probably similar to precipitation quality in 

the Guanella Pass area. Precipitation-weighted-mean 

concentrations for winter and summer in 1997 at 

three sites (table 3, fig. 4) along the Front Range 

of Colorado are listed in table 4. Using precipitationweighted-mean concentration ensures that the influence of the weekly composite concentration on the 

mean is proportional to the amount of precipitation 

that week. This concentration is computed as the 

sum of the weekly products of the precipitation 

volume multiplied by the composite concentration, 

and divided by the sum of all weekly precipitation 

volumes, for a particular season. For purposes of 

this study, winter included the months of December, 

January, and February, and summer included June, 

July, and August (National Atmospheric Deposition 

Program/National Trends Network, 1998). 

Similar to snow chemistry of Guanella 

Pass samples, summer rainfall samples at the three 

NADP/NTN sites had low specific conductance, 

were slightly acidic, and had a low chloride concentration (table 4) (National Atmospheric Deposition 

Table 3. Selected National Atmospheric Deposition 

Program/National Trends Network sites in Colorado

Site

number

(fig. 4)

Site

name Latitude Longitude Altitude(feet)

P1 Loch Vale 40°17'16'' 105°39'46'' 10,364

P2 Niwot Saddle 40°03'19'' 105°35'18'' 11,549

P3 Manitou 39°06'04'' 105°05'31'' 7,749

Program/National Trends Network, 1998). Although 

concentrations of dissolved ammonia and nitrate are 

larger at the NADP/NTN sites than those measured 

in the snowpack on Guanella Pass, general patterns 

probably are similar. Despite a large range in mean 

concentrations among NADP/NTN sites, data indicate 

that dissolved inorganic nitrogen concentrations are 

larger in summer than winter. Also, the prevalence 

of relatively large inorganic nitrogen concentrations 

in rainfall is important to the interpretation of roadrunoff nutrient chemistry because rapid conveyance 

of nutrient-laden runoff to streams bypasses soil 

processes that could remove nitrogen, resulting in 

larger stream nitrogen concentrations during rainstorm runoff.

Streams

Streams are the primary water resource in the 

Guanella Pass area. It is important to understand the 

hydrologic and water-quality aspects of study-area 

streams in order to characterize current conditions 

and establish a baseline for future comparisons.

Hydrology

Streamflow in the study area is affected by 

seasonal snow accumulation and melting (fig. 5). 

A winter base-flow period lasts from about midSeptember to March and is characterized by low, 

stable flows that occur primarily beneath a cover 

of ice in midwinter and are supported by groundwater discharge. Particle transport is generally 

small and dissolved-solids concentrations are 

generally large during this period.

In April or early May, warm air temperatures 

can cause limited melting, especially at lower elevations, which causes small rises in streamflow and a 

flushing of sediment and chemical constituents that 

have accumulated on the streambed, in snowpack, 

and in soil or aquifer pore spaces. For sediment, the 

flushing is related to erosion by increased streamflow. 

For some dissolved chemical constituents, the flushing 

is related to the displacement of soil water and ground 

water (which are concentrated in dissolved solids due 

to longer contact time with soil and rock) into streams 

by meltwater (Hornberger and others, 1994) and to 

the selective release of chemical constituents from 

snowpack during the early period of snowpack 
14 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

melting (Davis and others, 1995). During this early 

melting period, the high-altitude snowpack reaches 

melting temperature, and meltwater infiltrates into 

the underlying soil and into ground water. This 

increases the ground-water hydraulic head under 

the snowpack, and ground water discharges to the 

streams. 

During the rising limb of the hydrograph, 

streamflows increase rapidly but still fluctuate in 

response to changes in air temperature and spring 

storms. Streamflow fluctuates daily in response to 

melting (fig. 6), which can influence concentrations of water-quality constituents by dilution 

and physical suspension. 

Peak streamflow typically occurs between late 

May and mid-June. Streamflows rapidly decrease after 

the peak, and the decline typically slows through July. 

Particle transport begins to decrease because of 

decreasing supply of sediment and energy for transport, and dissolved-solids concentrations generally 

increase because of less dilution by meltwater and 

changing sources of flow as the annual snowpack is 

depleted and streamflow is sustained by ground water. 

Rainstorms can occur from May to September but are 

most prevalent in July, August, and early September. 

In general, rainstorms cause small increases in streamflow but are not an important contributor to the annual 

total runoff.

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

DENVER

Colorado

Springs

Pueblo

Grand 

Junction

SOUTH

PLATTE

RIVER

8

9

8

9

11

7

5

1

3

4

5

6

2

10

EXPLANATION

Active streamflow measurement site and

 discontinued suspended-sediment measurement

 site (site number in table 18)

Discontinued streamflow and suspended-

 sediment measurement site (site number

 in table 18)

NADP/NTN monitoring site (site number

 in table 3)

P3

RIO GRANDE

ARKANSAS RIVER

COLORADO RIVER

P2

P1

P3

Figure 4. Location of selected precipitation and suspended-sediment sampling sites in Colorado.
CHARACTERIZATION OF WATER RESOURCES 15

Continuous streamflow was measured at 

seven sites in the study area (fig. 1). Annual streamdischarge data (Stevens and others, 1997; Stevens, 

2000) are summarized in table 5. Differences in 

WY 1995–97 discharge for all sites are represented 

generally by the 1995–97 Geneva Creek (GC11) 

hydrograph shown in figure 7. The highest peak 

streamflows and annual runoff occurred in 1995 

and the lowest occurred in 1996. Runoff measured 

at each site was generally proportional to drainage 

area, although the runoff per square mile differs 

(table 5) because of variations in precipitation 

with altitude. Annual runoff during the study period 

ranged from 1,220 acre-ft/yr (CC2 in 1996) to 

59,510 acre-ft/yr (GC11 in 1995) (table 5; Stevens 

and others, 1997; Stevens, 2000).

Because the study period was only 3 years, the 

WY 1995–97 average runoff at streamflow-gaging 

stations with longer records might provide perspective 

in the context of long-term average runoff (table 6). 

In comparison to historical runoff at nearby gaging 

stations, WY 1995 was an exceptionally large runoff 

year. Flooding occurred in Georgetown, and some 

culvert and road damage resulted from peak flows 

in the Guanella Pass study area. Streamflow in water 

year 1996 was slightly above normal in some areas 

and below normal in other areas, while water year 

1997 was above normal but less than WY 1995 high 

flows. 

Flow-duration curves can be used to indicate 

which flow ranges were different in year-to-year 

comparisons. The Geneva Creek near Grant site 

(GC11) generally represents trends seen throughout 

the study area (fig. 8). The flow-duration curves 

show that the differences in flow among the 3 years 

occurred during the highest 10 to 20 percent of streamflows. These highest daily flows are representative of 

the peak snowmelt period and are important because 

generally most of the suspended-sediment and waterquality constituent loads are transported by the highest 

flows.

Water-Quality Characteristics

Water quality in the Guanella Pass study 

area was summarized using statistics, boxplots, 

and nonparametric correlations with streamflow, 

specific conductance, and suspended-sediment 

concentration. Evaluation of water quality with standards based on State of Colorado fixed and equationderived values are described in the “Colorado WaterQuality Standards” section of this report. Methods of 

data collection, water-quality data, and daily mean 

data from continuously measured parameters are 

presented in Stevens and others (1997) and Stevens 

(2000). Statistical summaries of water-quality 

information are listed in table 7 for all sites and in 

Appendix tables 36–49 for individual sampling sites 

where more than two samples were collected. 

Table 4. Rainfall chemical quality at selected Front Range of Colorado NADP/NTN sites in 1997 (National Atmospheric 

Deposition Program, 1998)

[NADP/NTN, National Atmospheric Deposition Program/National Trends Network; concentrations are precipitation-weighted-mean concentrations; μS/cm, 

microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; winter includes December, January, February; summer includes June, July, 

and August]

Property or constituent Loch Vale (P1)1 Niwot Saddle (P2)1 Manitou (P3)1

Winter Summer Winter Summer Winter Summer

Specific conductance, μS/cm 4.8 7.6 4.9 9.6 8.7 12.6

pH, standard units 5.07 5.00 5.09 4.88 5.06 4.77

Calcium, dissolved, mg/L as Ca .04 .09 .09 .11 .12 .19

Magnesium, dissolved, mg/L as Mg .005 .012 .010 .014 .018 .026

Sodium, dissolved, mg/L as Na .050 .033 .038 .031 .068 .049

Potassium, dissolved, mg/L as K .011 .022 .015 .023 .042 .042

Chloride, dissolved, mg/L as Cl .08 .05 .05 .06 .11 .08

Sulfate, dissolved, mg/L as SO4 .28 .50 .26 .73 .31 .97

Nitrogen, ammonia, dissolved, mg/L as N .03 .18 .03 .25 .21 .28

Nitrogen, nitrate, dissolved, mg/L as N .41 .78 .52 1.08 1.18 1.41

1Sites are shown on map in figure 4.
16 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Onsite Measurements

Onsite measurements of water temperature, 

specific conductance, pH, and dissolved oxygen were 

made when water-quality samples were collected. 

Water temperature was measured continuously at 

sites CC2, CC5, CC7, CC9, CC11, GC1, GC2, GC5, 

GC8, GC10, GC11, and DC1, and specific conductance continuously at sites CC2, CC5, CC7, CC9, 

GC5, GC11, and DC1 (Stevens and others, 1997; 

Stevens, 2000). 

Water temperature was measured continuously 

on a seasonal basis (May to September) at selected 

sites during WY’s 1995–97 (Stevens and others, 1997; 

Stevens, 2000). Most sites had mean daily and instantaneous water temperatures within 1 or 2 degrees 

above 0°C from November to March. Summer 

monthly mean water temperatures for sites monitored 

in WY’s 1996–97 with sufficient data are listed in 

table 8 and shown in figure 9. Summer water temperatures at all sites have a strong daily (diurnal) fluctuation influenced by air temperature, generally varying 

by as much as 5° to 10°C during the day. The warmest 

months of the year are July and August when monthly 

mean water temperatures ranged from 7.1° to 11.6°C; 

instantaneous high water temperatures during this 

period ranged from about 10° to 20°C (Stevens, 2000). 

Figure 9 indicates that monthly mean temperatures 

between sites vary by less than 5 degrees during the 

entire open-water season. In May, when there is no 

ice cover at low-elevation sites and ice cover is only 

beginning to melt in the high basins (GC1, GC2, 

CC2), a water-temperature gradient due to elevation 

(cooler at higher sites than at lower sites) is evident 

(table 8 and fig. 9). Through summer, the temperature 

differences between sites decrease.

Water chemistry in the streams of the Guanella 

Pass area changes seasonally with variations in water 

discharge (fig. 10). During the study period, water 

in the streams was relatively dilute, with specificconductance values generally below 100 μS/cm. 

Specific conductance is strongly correlated with 

the amount of dissolved ionic compounds in water, 

making it useful for assessing the general amount 

of dissolved material that can degrade water when 

present in large concentrations (Hem, 1985). Median 

0

700

100

200

300

400

500

600

DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND 

ON D J FM AM J J AS

1996 1997 Winter base flow, snow accumulation period Spring flush, early melting Rising limb of snowmelt hydrograph

Falling limb of snowmelt hydrographLate summer, low flow, rainstorm events

Figure 5. Generalized stream hydrograph divided into seasonal periods.
CHARACTERIZATION OF WATER RESOURCES 17

specific conductance at sites with computed statistics 

(table 7 and Appendix tables 36–49) ranged from 

31 μS/cm at site GC1 to 87 μS/cm at site CC7. Less 

mineralized headwater sites (CC1, GC1, and GC2) 

had minimum specific conductances less than 

30 μS/cm. Acid-sulfate weathering, caused by the 

oxidation of pyrite in the headwaters of Geneva and 

Leavenworth Creeks, was the source of relatively 

large specific conductances (greater than 100 μS/cm) 

measured during low flows along those streams. Large 

specific conductances also were measured at site CC2 

at low flows and were due to the presence of springs 

located just upstream, which contribute water with 

specific conductances greater than 200 μS/cm 

(Stevens and others, 1997; Stevens, 1999).

Spearman correlation coefficients (Helsel and 

Hirsch, 1992) of specific conductance with selected 

constituents at selected sites were computed (table 9). 

Spearman’s rho is a nonparametric measure of the 

strength of monotonic correlation between two variables using a rank procedure. Nonparametric statistics 

are less affected by non-normally distributed data than 

parametric statistics and can be used with data sets 

containing censored values (data reported as less than 

laboratory MRL). The correlation coefficient varies 

from minus 1 to plus 1, with the negative sign indicating a negative slope or decreasing dependent variable with an increasing independent variable, and the 

positive sign indicating a positive slope or increasing 

dependent variable with an increasing independent 

variable. Stronger correlation is indicated by values 

more positive or more negative than zero. The p-value 

is computed to indicate the significance level and twotailed probability of error. For this study, Spearman’s 

rho of greater than plus or minus 0.50 was considered 

at least moderately correlated. Also for this study, 

p-values less than 0.05 were considered highly significant and indicate a less than 5-percent statistical probability of error. 

At all sites listed in table 9, specific conductance 

had a strong positive correlation with most of the 

major dissolved constituents (calcium, magnesium, 

sodium, alkalinity, sulfate, and silica), with the exception of potassium and chloride at three sites. Specific 

conductance generally was poorly and insignificantly 

correlated with nutrients. Trace elements were poorly 

0

600

100

200

300

400

500

INSTANTANEOUS WATER DISCHARGE, IN CUBIC FEET PER SECOND

April May June July August September

1997

GENEVA CREEK AT GRANT (GC11)

SOUTH CLEAR CREEK ABOVE LOWER 

CABIN CREEK RESERVOIR (CC5)

Figure 6. Fluctuations in instantaneous stream discharge at sites GC11 and CC5, April through 

September 1997.
18 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

and insignificantly correlated with specific conductance with the exception of GC11, where manganese 

and zinc were moderately and positively correlated 

with specific conductance in both total recoverable 

and dissolved analyses. Suspended-sediment concentration generally had a weak inverse correlation with 

specific conductance; the negative slope reflects the 

opposite influences of streamflow on the two constituents (that is, specific conductance decreases with 

increasing streamflow, whereas suspended-sediment 

concentration generally increases with increasing 

streamflow).

Median specific conductance generally 

increased from site CC1 near the headwaters of South 

Clear Creek to CC7, just upstream from the confluence with Leavenworth Creek (fig. 11). Concentration 

by evapotranspiration, tributary inflow, or groundwater inflow might be the cause of the downstream 

upward trend.

Upstream/downstream comparisons in two 

reaches (CC1 to CC2, and CC13 to CC5, fig. 1) along 

South Clear Creek in water year 1997 also were used 

to determine whether specific conductance increases 

in a downstream direction in upper South Clear Creek, 

a stream reach that parallels the Guanella Pass road. 

Samples collected at paired upstream/downstream 

sites (sampled in downstream order, closely spaced in 

time) indicates that the upstream sites generally had 

smaller values of specific conductance on all of the 

sampling dates (fig. 12). Figure 12 also shows that 

water discharge increases in a downstream direction, 

indicating inflow from surface- and ground-water 

sources, which could explain the increase in specific 

conductance.

Specific conductance generally increased in a 

downstream direction along Duck Creek from GC1 to 

GC5 (fig. 11). Geneva Creek, a stream with relatively 

large concentrations of dissolved solids as a result of 

Table 5. Stream discharge data for water years 1995–97 at sites with stream gages

[ft, feet; mi2, square mile; ft3/s, cubic feet per second; acre-ft, acre feet; site locations are shown in figure 1]

Measurement CC2 CC5 CC7 CC9 GC5 GC11 DC1

Altitude of gage (ft) 10,710 10,100 9,280 9,280 9,750 8,760 9,280

Drainage area (mi2) 2.19 11.8 16.0 12.0 7.78 74.6 13.4

Water year 1995

Maximum daily discharge (ft3/s) -- 107 147 125 78 746 --

Minimum daily discharge (ft3

/s) -- 1.6 3.6 1.2 0.46 7.4 --

Average daily discharge (ft3/s) -- 15.3 21.2 17.7 7.33 82.2 --

Instantaneous peak flow (ft3/s) -- -- 215 168 97 1,070 --

Annual runoff (acre-ft) -- 11,110 15,350 12,830 5,310 59,510 --

Annual yield (acre-ft/mi2) -- 942 959 1,069 683 798 --

Water year 1996

Maximum daily discharge (ft3/s) 19 36 60 83 29 282 31

Minimum daily discharge (ft3

/s) .17 2.5 3.4 1.3 .81 10 2.5

Average daily discharge (ft3

/s) 1.68 10.7 16.6 13.8 5.92 55.7 8.96

Instantaneous peak flow (ft3/s) -- 42 64 100 32 357 --

Annual runoff (acre-ft) 1,220 7,770 12,080 10,020 4,300 40,470 6,510

Annual yield (acre-ft/mi2

) 557 658 755 835 553 542 486

Water year 1997

Maximum daily discharge (ft3/s) 19 54 113 100 36 438 103

Minimum daily discharge (ft3/s) .31 2.8 3.7 1.5 .60 11 2.4

Average daily discharge (ft3/s) 2.21 14.0 18.4 15.3 6.60 70.2 16.7

Instantaneous peak flow (ft3/s) 31 59 127 124 39 547 136

Annual runoff (acre-ft) 1,600 10,100 13,330 11,080 4,780 50,820 12,120

Annual yield (acre-ft/mi2) 731 856 833 923 614 681 904
CHARACTERIZATION OF WATER RESOURCES 19

acid-sulfate weathering processes, tends to decrease in 

specific conductance in a downstream direction from 

GC7 to GC11 (fig. 11) due to dilution by less concentrated tributary flows.

Values of pH generally were neutral (between 

about 7 and 8) (fig. 11) except at GC7 and GC6, 

mineralized sites in the upper part of Geneva Creek 

(upstream from the moderating influence of Scott 

Gomer Creek), where pH values as low as 3.9 were 

measured (GC6). Annual fluctuations in pH at 

most sites were less than 1.0 pH unit. Although 

Leavenworth Creek is affected by mine drainage, 

pH was always neutral at the mouth (CC9). The lowflow sample in the upper part of the Leavenworth 

Creek Basin (CC8) in 1995 also had a near-neutral 

pH (7.2). The pH was not correlated with specific 

conductance (table 9) except at site GC11, where 

seasonal dilution by relatively alkaline snowmelt 

causes a weak but significant positive correlation with 

discharge and consequently a weak but highly significant negative correlation with specific conductance. 

Alkaline snowmelt might seem inconsistent because 

snow is weakly acidic, but exposure of the meltwater 

to soil and rock materials increases alkalinity of the 

runoff.

The solubility of dissolved oxygen is 

controlled by temperature and barometric pressure. 

Certain natural environments such as wetlands and 

the bottom water of lakes can be undersaturated in 

dissolved oxygen; but generally the turbulent, shallow, 

rapid-flowing streams of mountainous areas are well 

oxygenated. Temperature fluctuations and photosynthetic activity can result in temporary supersaturation 

of dissolved oxygen. Dissolved-oxygen concentrations 

during the study ranged from 6.7 mg/L (GC2) to 

11.6 mg/L (CC5), and the median percentage of 

saturation of dissolved oxygen ranged from 99 (GC5, 

GC8) to 104 (GC10) (table 7, Appendix tables 36–49). 

No dissolved oxygen deficiencies (less than 6 mg/L; 

Colorado Department of Public Health and Environment, Water Quality Control Division, 1996) were 

measured in any streams during the study.

0

800

100

200

300

400

500

600

700

DAILY MEAN WATER DISCHARGE, IN CUBIC FEET PER SECOND

1994 1995 1996 1997

O ND J FM A MJ J A S OND J FMA MJ J A SO ND J FMA MJ J A S

Figure 7. Daily mean water discharge at Geneva Creek at Grant (GC11), water years 1995–97.
20 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Table 6. Percentage of average annual flow for streams near Guanella Pass study area, water years 1995–97

[Data from Crowfoot and others (1996–98); WY, water year; average annual runoff is for the period of record]

U.S. Geological 

Survey station 

number

Station name

Average 

annual 

runoff 

(acre-ft)

Percentage of

average annual flow Distance from study area

WY 1995 WY 1996 WY 1997

06716500 Clear Creek near Lawson 105,700 151 126 139 6 miles downstream from Georgetown

06710385 Bear Creek above Evergreen 29,330 157 77 119 21 miles east of Guanella Pass

06706000 North Fork South Platte River 

below Geneva Creek, at 

Grant1

52,240 155 106 137 1,500 feet downstream from confluence 

with Geneva Creek, at Grant

 1Diversions from Roberts Tunnel have been subtracted.

EXPLANATION

Water year 1995

Water year 1996

Water year 1997 

0

800

100

200

300

400

500

600

700

DISCHARGE, IN CUBIC FEET PER SECOND 

0 20 40 60 80 100 120

PERCENTAGE OF YEAR DISCHARGE WAS EXCEEDED

Figure 8. Flow-duration curves at Geneva Creek at Grant (GC11), water years 1995–97.
CHARACTERIZATION OF WATER RESOURCES 21

Table 7. Summary of stream-water-quality statistics, water years 1995–97

[--, insufficient data to calculate statistic; ranges of site data computed from all stream-water-quality sites; median statistics are a compilation of individual 

site summary statistics in the Appendix; **, 1995 data were at a higher minimum reporting limit (MRL) and are not included in computations; μS/cm, 

microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; mg/L, milligrams per liter; %, percentage; <, less than; μg/L, 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units

Data range Summary of site median statistics

Minimum Maximum Minimum 

median

Median of 

medians

Maximum

median

Specific conductance μS/cm 23 210 31 44 87

pH units 3.8 8.8 5.0 7.6 8.0

Turbidity NTU .2 2,140 .7 2.2 8.0

Dissolved oxygen mg/L 6.7 11.6 7.7 8.8 9.8

Dissolved oxygen saturation % 84 117 99 100 104

Hardness, as CaCO3 mg/L 9 89 11 18 38

Calcium, dissolved mg/L 2.6 16 3 3 5 10

Magnesium dissolved mg/L .6 12 .8 1.2 3.9

Sodium dissolved mg/L .7 5.6 .8 1.4 1.7

Potassium dissolved mg/L .2 2.0 .5 .6 1.2

Acid-neutralizing capacity, Alkalinity, lab, as CaCO3 mg/L <.1 61 4.6 16 41

Sulfate mg/L .8 90 1.4 3.3 23

Chloride mg/L <.1 36 .1 .3 1.2

Fluoride mg/L <.1 .4 .1 .2 .2

Silica mg/L 4.1 13 4.4 6.8 9.2

Dissolved solids, residue at 180 degrees Celsius mg/L 10 128 24 40 70

Nitrogen, nitrite, dissolved as N mg/L <.01 .01 -- -- --

Nitrogen, nitrite plus nitrate, dissolved as N** mg/L .005 .22 .011 .059 .1

Nitrogen, ammonia, dissolved as N** mg/L <.002 .036 <.002 <.002 <.002

Nitrogen, ammonia plus organic, dissolved as N mg/L <.2 .3 -- -- --

Nitrogen, ammonia plus organic, total as N mg/L <.2 4.3 <.2 <.2 .2

Phosphorus, total as P** mg/L <.001 3.2 .002 .009 .02

Phosphorus, dissolved as P mg/L <.01 .04 -- -- --

Phosphorus, dissolved orthophosphate as P** mg/L <.001 .02 <.001 .001 .002

Aluminum, total recoverable as Al μg/L 20 11,000 -- -- --

Aluminum, dissolved as Al μg/L 4 4,700 -- -- --

Antimony, dissolved as Sb μg/L <1 <1 -- -- --

Arsenic, total recoverable as As μg/L <1 <1 -- -- --

Barium, total recoverable as Ba μg/L <100 <100 -- -- --

Barium, dissolved as Ba μg/L 16 38 -- -- --

Beryllium, total recoverable as Be μg/L <10 <10 -- -- --

Beryllium, dissolved as Be μg/L <1 <1 -- -- --

Cadmium, total recoverable as Cd μg/L <1 2 -- -- --

Cadmium, dissolved as Cd μg/L <1 2 -- -- --

Chromium, total recoverable as Cr μg/L <1 20 -- -- --

Chromium, dissolved as Cr μg/L <1 2 -- -- --

Cobalt, total recoverable as Co μg/L <1 10 -- -- --

Cobalt, dissolved as Co μg/L <1 8 -- -- --

Copper, total recoverable as Cu μg/L <1 92 <1 <1 17

Copper, dissolved as Cu μg/L <1 37 <1 <1 4

Iron, total recoverable as Fe μg/L 10 110,000 80 460 1,200

Iron, dissolved as Fe μg/L <3 1,800 18 104 420
22 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Dissolved-Solids Loads

Dissolved-solids loads were computed for sites 

with continuous specific-conductance data (CC2, 

CC5, CC7, CC9, GC5, GC11, and DC1) by relating 

specific conductance to dissolved-solids (sum of 

constituents) concentration. The result of a regression 

of specific conductance (SC) with dissolved solids 

sum of constituents concentration (Sd) for all available 

data from all sites during the study was used to estimate daily mean dissolved-solids concentration from 

computed and estimated daily mean specific conductance at the selected sites. The data were transformed 

using the natural logarithm (LN) before doing an ordinary least-squares regression, then retransformed and 

multiplied by a bias transformation-correction factor. 

The regression is expressed as:

(1)

where

a is the slope coefficient, and

b is the intercept coefficient for the regression.

A nonparametric bias correction factor, Cb, 

which is the mean of the exponentiated residuals from 

the regression (Duan, 1983), is expressed as:

(2)

where

e = 2.71828 (base for natural logarithms),

r = residuals of the regression, and 

n = number of residuals.

The final form of the equation is:

LN S (3) d ( ) = b a LN (SC) +

Cb Σ e( )r = [ ] ⁄ n

Sd e

( ) a SC( ) b Cb =

Lead, total recoverable as Pb μg/L <1 71 <1 <1 36

Lead, dissolved as Pb μg/L <1 2 <1 <1 2

Manganese, total recoverable as Mn μg/L <10 2,300 10 20 190

Manganese, dissolved as Mn μg/L <1 760 <1 5.5 190

Mercury, total recoverable as Hg μg/L <.1 .1 -- -- --

Molybdenum, total recoverable as Mo μg/L <1 2 -- -- --

Molybdenum, dissolved as Mo μg/L <1 <1 -- -- --

Nickel, total recoverable as Ni μg/L <1 17 -- -- --

Nickel, dissolved as Ni μg/L <1 17 -- -- --

Selenium, total recoverable as Se μg/L <1 <1 -- -- --

Silver, total recoverable as Ag μg/L <1 <1 -- -- --

Silver, dissolved as Ag μg/L <1 2 -- -- --

Zinc, total recoverable as Zn μg/L <10 430 <10 <10 190

Zinc, dissolved as Zn μg/L <3 320 <3 5.5 170

Uranium, natural, dissolved μg/L <1 2 -- -- --

Carbon, organic, total as C mg/L 1.0 33 -- -- --

Carbon, organic, dissolved as C mg/L .5 3.3 -- -- --

Sediment, suspended mg/L <1 1,180 2 5.5 18

Sediment, suspended, % finer than 0.062 mm % 14 100 44 69 83

Sediment, suspended, discharge T/d .001 1,370 .01 .19 1.8

Table 7. Summary of stream-water-quality statistics, water years 1995–97—Continued

[--, insufficient data to calculate statistic; ranges of site data computed from all stream-water-quality sites; median statistics are a compilation of individual 

site summary statistics in the Appendix; **, 1995 data were at a higher minimum reporting limit (MRL) and are not included in computations; μS/cm, 

microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; mg/L, milligrams per liter; %, percentage; <, less than; μg/L, 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units

Data range Summary of site median statistics

Minimum Maximum Minimum 

median

Median of 

medians

Maximum

median
CHARACTERIZATION OF WATER RESOURCES 23

The reduced form of the equation and regression 

information for the Guanella Pass data is:

(4)

where

r

2 is the correlation coefficient, and

p is the p-value indicating significance 

of the slope coefficient.

After computing daily dissolved-solids concentration from equation 3, the daily load of dissolved 

solids, Lsd, was computed from:

(5)

where

Q is the daily mean water discharge, in cubic 

feet per second.

Annual dissolved-solids loads for available 

water years were calculated as the sum of the daily 

loads for selected sites (table 10). Annual loads 

ranged from 72.0 tons at site CC2 in water year 1996 

to 2,800 tons at site GC11 in water year 1995. Flowweighted-mean concentrations of dissolved solids 

(computed by dividing the annual load in tons by 

the mean annual flow in cubic feet per second and 

converting to milligrams per liter) among all sites 

ranged from 25 to 53 mg/L. These differences might 

be related to basin geology or land use. When loads 

were expressed as flow-weighted-mean annual 

concentrations and yields per unit of runoff, the 

concentrations and yields at a particular site were 

similar each year.

Major Ions

The inorganic dissolved constituents that 

compose most of the dissolved solids in natural waters 

are called major cations and anions. The major cations 

are calcium, magnesium, sodium, and potassium and 

have positive charges. Major anions are bicarbonate, 

sulfate, chloride, and fluoride and have negative 

charges. Bicarbonate concentration is computed 

from an alkalinity titration that measures the acidneutralizing capacity (ANC) of the solutes in the 

water. Differences in the major-ion composition 

of water can indicate differences in water sources, 

geochemical processes, geology, and land use. 

A related property, hardness, is the sum of the 

milliequivalents of calcium and magnesium multiplied 

by 50 and is expressed as equivalent CaCO3, in milligrams per liter (Hem, 1985). Hardness is used to 

compute the trace-element water-quality standards 

in Colorado. Summary statistics for major ions are 

Sd ( ) 1.496 SC( ) 0.7962 = ;

r

2 = = 0.95; p <0.0001

Lsd ( ) 0.0027 QSd =

Table 8. Selected monthly mean water temperature in degrees Celsius for sites with continuous water-temperature 

measurement

[--, no data]

Site

(see fig. 1)

Altitude

(feet)

Water year 1996 Water year 1997

May June July August May June July August

GC2 11,160 0.5 5.7 -- 7.4 0.4 5.4 7.7 7.5

GC1 11,160 1.7 5.3 10.1 -- -- -- -- --

CC2 10,710 -- 5.7 8.4 7.1 0.9 5.8 7.6 7.8

CC5 10,100 3.1 6.1 8.3 8.4 3.2 5.9 7.4 8.2

GC8 9,840 3.0 5.1 8.3 8.7 2.9 4.7 7.1 8.0

GC5 9,750 5.4 6.8 9.7 8.7 4.7 6.4 9.0 8.7

CC11 9,730 3.6 7.1 9.6 8.9 3.0 6.3 8.2 8.1

GC10 9,380 2.8 8.1 11.2 9.4 3.0 7.0 10.2 9.0

CC7 9,280 5.3 8.8 12.0 10.1 5.2 8.8 10.7 11.6

CC9 9,280 2.3 4.7 7.9 8.2 2.1 4.6 7.1 8.0

DC1 9,280 -- 5.0 7.0 6.8 2.4 4.6 6.2 6.8

GC11 8,760 5.3 7.7 10.9 10.4 4.8 7.2 9.8 9.7
24 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

14

10

14

10

14

10

MONTHLY MEAN WATER TEMPERATURE, IN DEGREES CELSIUS

14

10

0

5

0

5

0

5

GC2 GC1 CC2 CC5 GC8 GC5 CC11 GC10 CC7 CC9 DC1 GC11

SITE

0

5

May 1996

June 1996

August 1996

July 1996

MISSING DATA

MISSING DATA

MISSING DATA

MISSING DATA

MISSING DATA

Figure 9. Monthly mean water temperature at selected sites, water years 1996–97.
CHARACTERIZATION OF WATER RESOURCES 25

May 1997

0

14

5

10

0

14

5

10

0

14

5

10

MONTHLY MEAN WATER TEMPERATURE, IN DEGREES CELSIUS

0

14

5

10

June 1997

July 1997

August 1997

GC2 GC1 CC2 CC5 GC8 GC5 CC11 GC10 CC7 CC9 DC1 GC11

SITE

MISSING DATA MISSING DATA MISSING DATA MISSING DATA

Figure 9. Monthly mean water temperature at selected sites, water years 1996–97—Continued.
26 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

listed in table 7 and the Appendix (tables 36–49). Boxplots of hardness, ANC (alkalinity), sulfate, and chloride for selected sites are shown in figure 11.

Stream chemistry was characterized by the 

predominance of calcium and bicarbonate (as indicated 

by acid-neutralizing capacity and the range in pH) at 

most sites (Stevens and others, 1997). The exceptions 

are the stream reaches where acid-sulfate weathering 

contributes enough sulfate to dominate the anions in 

stream water (upper Geneva and Leavenworth Creeks) 

(Stevens and others, 1997). When the mineral pyrite 

in bedrock or mine waste is oxidized, hydrogen ions 

(acid), sulfate, and iron hydroxide are produced. A 

summary of the reactions can be represented as 

follows (Moran and Wentz, 1974):

This acid-sulfate weathering process can 

result in lowering of pH, large sulfate and dissolvedsolids concentrations, production of iron hydroxide 

(also known as yellow boy), and the release of trace 

elements such as copper, lead, and zinc associated 

with the pyrite or other minerals chemically weathered 

by the acidic water (Moran and Wentz, 1974).

Concentrations of major ions tended to be 

strongly and positively correlated with specific 

conductance (table 9), negatively correlated with 

water discharge (table 11), and poorly correlated 

with suspended sediment (table 12). 

Possible Effects of Magnesium Chloride Applications 

on Major-Ion Chemistry in Streams

Because magnesium chloride (dust inhibitor) 

and sodium chloride (deicer) have been used on parts 

of the Guanella Pass road in Clear Creek County, 

chloride might be an indicator of road maintenance 

operations affecting surface water. Chloride concentrations in water are generally low in areas of crystalline bedrock geology because of the lack of minerals 

containing chloride. The primary source of chloride 

in these areas is precipitation and land use (such as 

deicers or dust inhibitors applied to a road).

FeS2 3.75O2 + + 3.5H2O

= Fe OH ( )3 2SO4

–2 4H+ + +

Streamflow

Specific conductance

STREAMFLOW, IN CUBIC FEET PER SECOND

0

120

20

40

60

80

100

0

120

20

40

60

80

100

SPECIFIC CONDUCTANCE, IN MICROSIEMENS 

PER CENTIMETER

OND

1996

J FMA MJ J AS

1997

Figure 10. Seasonal variation of specific conductance and streamflow at site DC1, water 

year 1997.
CHARACTERIZATION OF WATER RESOURCES 27

Table 9. Spearman’s coefficients of correlation for specific conductance (μS/cm at 25°C) and concentrations of selected water-quality co

water years 1995–97

[rho, Spearman correlation coefficient; p-value, probability of a greater Spearman’s rho; p-values <0.05 (2-tailed) are considered highly significant and are shaded, a lighshade for negative correlations; Spearman’s rho’s greater than plus or minus 0.50 are shaded; NTU, nephelometric turbidity units; mg/L, milligrams per liter; μg/L, micro

<, less than; correlations based on periodic water-quality samples]

Property or constituent

CC2 CC5 GC5 GC11 

rho p-value rho p-value rho p-value rho p-va

pH, standard units 0.18 0.240 0.05 0.771 –0.12 0.420 –0.31 0.0Turbidity, NTU .19 <.001 –.11 .061 .05 .206 –.10 .0

Oxygen, dissolved, mg/L –.12 .487 .56 <.001 .49 .001 .34 .0

Hardness, total, mg/L as CaCO3 .99 <.001 .92 <.001 .97 <.001 .94 <.0

Calcium, dissolved, mg/L .98 <.001 .89 <.001 .97 <.001 .93 <.0Magnesium, dissolved, mg/L .99 <.001 .81 <.001 .95 <.001 .95 <.0Sodium, dissolved, mg/L .96 <.001 .55 .029 .96 <.001 .83 <.0Potassium, dissolved, mg/L .38 .143 .82 <.001 .41 .0

Alkalinity (acid-neutralizing capacity), mg/L as CaCO3 .95 <.001 .91 <.001 .69 <.001 –.21 .3

Sulfate, dissolved, mg/L .96 <.001 .66 <.001 .82 <.001 .91 <.0Chloride, dissolved, mg/L .79 <.001 .29 .101 .58 <.001 .19 .2

Silica, dissolved, mg/L .64 <.001 –.34 .201 .92 <.001 .90 <.0

Dissolved solids, sum of constituents, mg/L as N .79 <.001 .91 <.001 .98 <.0Nitrogen, ammonia, dissolved, mg/L as N .12 .635 .02 .925 .53 .022 .39 .1

Nitrogen, ammonia plus organic, total, mg/L as N –.45 .005 .21 .282 .15 .371 –.07 .6

Nitrogen, nitrite plus nitrate, dissolved, mg/L as N –.01 .948 .25 .194 .49 .002 .15 .3

Phosphorus, total, mg/L as P –.30 .074 –.16 .416 .04 .796 –.29 .0Phosphorus, ortho, dissolved, mg/L as P .02 .951 .15 .457 .15 .547 –.21 .3Copper, dissolved, μg/L .14 .386 –.04 .833 –.26 .099 –.07 .6Copper, total recoverable, μg/L .13 .427 –.16 .383 .13 .391 .33 .0Iron, dissolved, μg/L –.21 .181 –.17 .369 .47 .002 –.60 <.0

Iron, total recoverable, μg/L –.19 .225 –.12 .502 .21 .163 –.34 .0Lead, total recoverable, μg/L .13 .394 –.14 .445 –.07 .630 –.06 .7Manganese, dissolved, μg/L –.19 .228 –.09 .624 .55 <.001 .82 <.0Manganese, total recoverable, μg/L –.11 .485 –.19 .295 .10 .508 .51 <.0Zinc, dissolved, μg/L –.26 .102 .23 .223 –.19 .237 .67 <.0Zinc, total recoverable, μg/L .21 .179 –.16 .369 –.14 .350 .60 <.0Suspended sediment, percentage finer than 0.062 mm .72 <.001 .34 .083 –.21 .789 .79 <.0Suspended-sediment concentration, mg/L –.74 <.001 –.30 .016 –.39 .077 –.40 .0
28 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

200

0

50

100

150

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

EXPLANATION

Minimum value

Location of sites shown 

 in figure 1.

25th percentile

Median

75th percentile

Maximum value

(16) Number of observations

(10) (18) (44) (38) (19) (9) (8) (47) (43) (7) (13) (47) (10) (10)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

10

2

4

6

8

pH, IN STANDARD UNITS

(16) (47) (55) (71) (53) (11) (6) (5) (31)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

TURBIDITY, IN NEPHELOMETRIC 

TURBIDITY UNITS

(16) (47) (55) (71) (53) (11) (6) (48) (35) (5) (10) (54) (10) (9)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1 1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

SUSPENDED SEDIMENT,

IN MILLIGRAMS PER LITER

(16) (43) (49) (62) (44) (10) (6) (38) (33) (5) (8) (23) (10) (9)

Figure 11. Distribution of concentrations and values of selected water-quality constituents at selected sites, water 

years 1995–97.
CHARACTERIZATION OF WATER RESOURCES 29

EXPLANATION

Minimum value

Minimum reporting

 limit

25th percentile

Median

75th percentile

Maximum value

(5) Number of observations

0

100

20

40

60

80

HARDNESS, IN MILLIGRAMS PER

LITER AS CALCIUM CARBONATE

0

80

20

40

60

ACID-NEUTRALIZING CAPACITY,

IN MILLIGRAMS PER LITER

AS CALCIUM CARBONATE 

0

60

20

40

SULFATE, IN MILLIGRAMS 

PER LITER

0.05

100

0.1

0.2

0.5

1

2

5

10

20

50

CHLORIDE, IN MILLIGRAMS

PER LITER

(5) (5) (30) (16) (5) (4) (4) (26) (28) (4) (3) (31) (3) (3)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(5) (5) (29) (16) (5) (4) (4) (26) (26) (4) (3) (30) (3) (3)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(11) (6) (42) (29) (6) (5) (5) (39) (43) (5) (5) (40) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(13) (6) (44) (34) (6) (5) (5) (39) (43) (5) (5) (40) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

Location of sites shown 

 in figure 1.

Figure 11. Distribution of concentrations and values of selected water-quality constituents at selected sites, 

water years 1995–97—Continued.
30 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

EXPLANATION

Minimum reporting limit

Values plotted if number

 of observations is less

 than 3

Minimum value

25th percentile

Median

75th percentile

Maximum value

Number of observations

0

0.04

0.01

0.02

0.03

AMMONIA, DISSOLVED, 

IN MILLIGRAMS PER LITER

0.0005

0.1

0.001

0.002

0.005

0.01

0.02

0.05

NITRITE PLUS NITRATE, DISSOLVED,

IN MILLIGRAMS PER LITER

0

0.010

0.002

0.004

0.006

0.008

ORTHOPHOSPHORUS, DISSOLVED,

IN MILLIGRAMS PER LITER

0.0001

10

0.0002

0.0005

0.001

0.002

0.005

0.01

0.02

0.05

0.1

0.2

0.5

1

2

5

PHOSPHORUS, TOTAL,

IN MILLIGRAMS PER LITER

(8) (2) (17) (2) (18) (16) (4) (2) (2) (2) (3) (18) (2) (20)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(8) (2) (17) (2) (18) (16) (4) (2) (2) (2) (3) (18) (2) (20)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(8) (2) (17) (2) (18) (16) (4) (2) (2) (2) (3) (18) (2) (20)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(10) (3) (37) (5) (20) (37) (4) (3) (3) (3) (4) (36) (5) (43)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(8)

Location of sites shown 

 in figure 1.

Figure 11. Distribution of concentrations and values of selected water-quality constituents at selected sites, water 

years 1995–97—Continued.
CHARACTERIZATION OF WATER RESOURCES 31

EXPLANATION

Minimum value

25th percentile

Median

75th percentile

Maximum value

(11) Number of observations

0

60

20

40

COPPER, DISSOLVED, 

IN MICROGRAMS PER LITER

0

100

20

40

60

80

COPPER, TOTAL RECOVERABLE,

IN MICROGRAMS PER LITER

0

800

200

400

600

IRON, DISSOLVED,

IN MICROGRAMS PER LITER

10

1,000,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

IRON, TOTAL RECOVERABLE,

IN MICROGRAMS PER LITER

(11) (6) (42) (29) (6) (5) (5) (39) (43) (5) (5) (40) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(11) (6) (42) (32) (7) (5) (5) (43) (46) (5) (5) (45) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(11) (6) (42) (29) (6) (5) (5) (39) (43) (5) (5) (40) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(11) (6) (42) (32) (7) (5) (5) (43) (46) (5) (5) (45) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

Minimum reporting limit

Location of sites shown 

 in figure 1.

Figure 11. Distribution of concentrations and values of selected water-quality constituents at selected sites, water 

years 1995–97—Continued.
32 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

EXPLANATION

Minimum value

25th percentile

Median

75th percentile

Maximum value

(11) Number of observations

1

1,000

2

5

10

20

50

100

200

500

MANGANESE, DISSOLVED,

IN MICROGRAMS PER LITER

10

10,000

20

50

100

200

500

1,000

2,000

5,000

MANGANESE, TOTAL

RECOVERABLE, IN

MICROGRAMS PER LITER

1

1,000

2

5

10

20

50

100

200

500

ZINC, DISSOLVED,

IN MICROGRAMS PER LITER

0

600

200

400

ZINC, TOTAL RECOVERABLE,

IN MICROGRAMS PER LITER

(11) (6) (42) (29) (6) (5) (5) (39) (43) (5) (5) (40) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(11) (6) (42) (32) (7) (5) (5) (43) (46) (5) (5) (45) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(11) (6) (42) (29) (6) (5) (5) (39) (43) (5) (5) (40) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

(11) (6) (42) (32) (7) (5) (5) (43) (46) (5) (5) (45) (5) (5)

CC1 CC2 CC5 CC7 CC9 CC11 GC1 GC2 GC5 GC7 GC8 GC10 GC11 DC1

Minimum reporting limit

Location of sites shown 

 in figure 1.

Figure 11. Distribution of concentrations and values of selected water-quality constituents at selected sites, water 

years 1995–97—Continued.
CHARACTERIZATION OF WATER RESOURCES 33

As mentioned previously, specific conductance increases downstream along South Clear 

Creek. Magnesium chloride or sodium chloride 

could increase specific conductance if supplied to

the stream. Chloride concentrations in streams in 

the Guanella Pass area are generally less than 1 mg/L, 

a small proportion of the major-ion concentration. 

However, storm-related samples at CC2 had chloride 

concentrations up to 36 mg/L, and some road-runoff 

samples had predominantly magnesium and chloride 

or sodium and chloride major-ion compositions 

(Stevens and others, 1997). The downstream increase 

in specific conductance along South Clear Creek does 

not seem to be strongly related to chloride or any 

particular major inorganic constituent because majorion composition tends to remain similar (figs. 13 and

14). Downstream increases in specific conductance are 

probably related to the concentration of dissolved 

solids by evapotranspiration.

Upstream/downstream comparisons in two 

reaches (CC1 to CC2, and CC13 to CC5, fig. 12) along 

South Clear Creek in water year 1997 were used to 

assess whether dissolved chloride concentrations were 

increasing in a downstream direction in upper South 

Clear Creek, a stream reach that runs parallel to the 

Guanella Pass road. Figure 12 indicates that the 

upstream sites for both pairs generally had smaller 

chloride concentrations during May and early June 

and in a rainstorm sample on July 28, 1997, for the 

CC1/CC2 pair. These dates correspond to the periods 

when road runoff is occurring, which is consistent 

with the migration of chloride in road runoff to 

streams. The downstream increases in concentration 

(fig. 12) could indicate effects from road runoff, which 

generally had larger concentrations of chloride than 

stream water (Stevens, 1999).

Clear Creek County applied magnesium chloride to the unpaved sections of the Guanella Pass road 

to control dust. During the study period, bighorn sheep 

were attracted to the salt residues and were frequently 

observed licking the treated portions of the road. 

The dust-control product applied is mainly MgCl2

(30 percent by volume), SO4 (less than 3.5 percent), 

K (less than 0.5 percent), Na (less than 0.7 percent), 

and H2O (less than 69 percent) (John Millward, Great 

Salt Lake Minerals, written commun., 1997). Trace 

elements are listed as minor components of the 

product. The magnesium chloride product was initially 

applied in 1987 to the section of road between the end 

of pavement near Lower Cabin Creek Reservoir and 

Naylor Creek at a rate of 1.5 gallons per square yard, 

and to the section between timberline on the south side 

of the pass and a point just past the road to the Duck 

Lake residences at a rate of 0.5 gallon per square yard 

(Jim Cannedy, Clear Creek County, oral commun., 

1998). In 1993, a second dust-control treatment was 

applied to the section of road between Naylor Creek 

and timberline on the south side of Guanella Pass at 

a rate of 0.5 gallon per square yard. A final application 

of magnesium chloride was made in 1996 to the 

unpaved portion of the road at a rate of 0.5 gallon per 

square yard (Jim Cannedy, Clear Creek County, oral 

commun., 1998).

To estimate if dissolved-solids loads might be 

sensitive to magnesium chloride applications, the mass 

of chloride applied to a section of road in a basin was 

compared to the estimated annual chloride load and 

the dissolved-solids load for a basin. The mass of chloride applied in the South Clear Creek Basin above 

Lower Cabin Creek Reservoir (CC5) was estimated 

using the application rates noted previously and a road 

width of 18 ft (table 13). The chloride load at CC5 

was estimated using a relation of the natural logarithm 

of the chloride load and water discharge for WY’s 

1995–97 (fig. 15) and applying the resulting equation 

to daily mean discharge to compute daily chloride 

loads. Daily loads for the water year were summed 

to compute annual loads at CC5 for WY’s 1995–97 

(table 13). 

The estimated mass of chloride from 

MgCl2 applied to the road in the CC5 basin in 1987 

(57.1 tons chloride), 1993 (11.5 tons), and 1996 

(15.5 tons) ranged from 83 to 414 percent of the 

estimated average annual chloride load (13.8 tons 

per year) transported in South Clear Creek at CC5 

during WY’s 1995–97 (table 13). 

To estimate how chloride applied to the 

road might affect concentrations in the stream, a 

hypothetical set of assumptions was used to compute 

changes in annual flow-weighted-mean concentrations 

(FWMC) of chloride transported from the CC5 basin. 

For the computation, it was assumed that the mass of 

chloride from the largest known application of MgCl2

applied to the Guanella Pass road in the CC5 basin 

(57.1 tons in 1987) was added to the estimated annual 

chloride load for each year (1995–97) at CC5 

(table 13). That load was then assumed to have been 

transported by the annual flow at CC5 that year and 

was converted to an annual FWMC of chloride 

(table 13). The FWMC that includes road-applied 

chloride could then be compared to the FWMC 

without road-applied chloride.
34 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

EXPLANATION

CC1

CC2

0

20

10

WATER DISCHARGE,

IN CUBIC FEET PER SECOND

0.1

10,000

1

10

100

1,000

TURBIDITY, IN NEPHELOMETRIC

TURBIDITY UNITS

0

150

50

100

SPECIFIC CONDUCTANCE, 

IN MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS

1

10,000

10

100

1,000

SUSPENDED-SEDIMENT 

CONCENTRATION, IN MILLIGRAMS

PER LITER

0

4

2

CHLORIDE CONCENTRATION, 

IN MILLIGRAMS PER LITER

MISSING DATA MISSING DATA

1997

20-Feb199715-May199720-May199723-May199730-May19972-June19979-July199728-July199710-Sept1997

20-Feb199715-May199720-May199723-May199730-May19972-June19979-July199728-July199710-Sept1997

20-Feb199715-May199720-May199723-May199730-May19972-June19979-July199728-July199710-Sept1997

20-Feb199715-May199720-May199723-May199730-May19972-June19979-July199728-July199710-Sept1997

20-Feb199715-May199720-May199723-May199730-May19972-June19979-July199728-July199710-SeptFigure 12. Comparison of water discharge, specific conductance, chloride concentration, turbidity, and suspended 

sediment at CC1 (upstream) and CC2 (downstream) and CC13 (upstream) and CC5 (downstream), in water 

year 1997.
CHARACTERIZATION OF WATER RESOURCES 35

EXPLANATION

CC13

CC5

MISSING DATA

1997

17-Apr19979-May199716-May- 3-June-1997

1997

30-June199710-Sept0

60

20

40

WATER DISCHARGE,

IN CUBIC FEET PER SECOND

40

100

60

80

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER CENTIMETER 

AT 25 DEGREES CELSIUS

0

2

1

CHLORIDE CONCENTRATION,

IN MILLIGRAMS PER LITER

1

1,000

2

5

10

20

50

100

200

500

TURBIDITY, IN NEPHELOMETRIC

TURBIDITY UNITS

0

300

100

200

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

1997

17-Apr19979-May199716-May- 3-June-1997

1997

30-June199710-Sept1997

17-Apr19979-May199716-May- 3-June-1997

1997

30-June199710-Sept1997

17-Apr19979-May199716-May- 3-June-1997

1997

30-June199710-SeptMISSING DATA MISSING DATA

1997

17-Apr19979-May199716-May- 3-June-1997

1997

30-June199710-SeptFigure 12. Comparison of water discharge, specific conductance, chloride concentration, turbidity, and suspended 

sediment at CC1 (upstream) and CC2 (downstream) and CC13 (upstream) and CC5 (downstream), in water 

year 1997—Continued.
36 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Results of the FWMC comparison indicate 

hypothetical increases in chloride from MgCl2

ranging from about 3 to 12 times. In the case of the 

largest increase, the annual FWMC of chloride at 

CC5 in 1996 (0.5 mg/L) might increase 12 times 

(to 5.9 mg/L). Although this is a large percentage 

increase, the increased concentrations are still 

relatively minor, about 14 percent of the total 

dissolved solids FWMC of 41 mg/L at CC5 in 

1996 (table 10). These increases are probably overestimates because it is unlikely that the entire mass 

of chloride applied would be flushed from the basin 

in a single year. If chloride applied to the road is not 

transported out of the basin within months of application, it could be stored in ground water or the soil 

material on the roadbed and might take years to 

leave the basin. Longer term monitoring is necessary to understand the fate of MgCl2 applied to the 

Guanella Pass road.

Nutrients

Nitrogen and phosphorus compounds in water 

are important plant and algal nutrients. In excess 

concentrations, nutrients can produce a nuisance 

growth of algae in streams and lakes. Nutrient concentrations in stream water were generally small or 

less than the laboratory MRL. The distributions of 

ammonia, nitrite plus nitrate, orthophosphorus, and 

total phosphorus are shown in boxplots (fig. 11). 

Table 10. Dissolved-solids loads computed for selected sites, water years 1995–97

[mi2, square mile; ft3/s, cubic feet per second; acre-ft, acre-feet; mg/L, milligrams per liter]

Site

(fig. 1)

Water

year

Drainage 

area

 (mi2)

Mean annual 

discharge 

(ft3/s)

Annual 

discharge

(acre-ft)

Annual 

dissolvedsolids load 

(tons)

Flow-weighted mean

dissolved-solids

concentration

(mg/L)

Dissolvedsolids yield

(tons/acre-ft)

Dissolvedsolids yield 

(tons/mi2)

CC2 1996 2.19 1.68 1,220 72.0 43 0.059 32.9

CC2 1997 2.19 2.21 1,600 88.7 41 .055 40.5

CC5 1995 11.8 15.3 11,100 597 40 .054 50.6

CC5 1996 11.8 10.7 7,750 437 41 .056 37.0

CC5 1997 11.8 14.0 10,100 554 40 .055 46.9

CC7 1995 16.0 21.2 15,400 1,070 51 .070 66.7

CC7 1996 16.0 16.6 12,100 864 53 .071 54.0

CC7 1997 16.0 18.4 13,300 933 51 .070 58.3

CC9 1995 12.0 17.7 12,800 670 38 .052 55.8

CC9 1996 12.0 13.8 10,000 547 40 .055 45.6

CC9 1997 12.0 15.3 11,100 602 40 .054 50.2

GC5 1995 7.78 7.33 5,310 219 30 .041 28.1

GC5 1996 7.78 5.92 4,300 169 29 .039 21.7

GC5 1997 7.78 6.60 4,780 189 29 .040 24.3

GC11 1995 74.6 82.2 59,500 2,800 35 .047 37.6

GC11 1996 74.6 55.7 40,500 2,100 38 .052 28.1

GC11 1997 74.6 70.2 50,800 2,420 35 .048 32.4

DC1 1996 13.4 8.97 6,510 239 27 .037 17.8

DC1 1997 13.4 16.7 12,100 404 25 .033 30.1
CHARACTERIZATION OF WATER RESOURCES 37

Table 11. Spearman’s coefficients of correlation for instantaneous water discharge (cubic feet per second) and concentrations of selecteat selected sites, water years 1995–97[rho, Spearman correlation coefficient; p-value, probability of a greater Spearman’s rho; p-values <0.05 (2-tailed) are considered highly significant and are shaded, a lighshade for negative correlations; Spearman’s rho’s greater than plus or minus 0.50 are shaded; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelom

milligrams per liter; μg/L, micrograms per liter; mm, millimeters; <, less than; correlations based on periodic water-quality samples]

Property or constituent

CC2 CC5 GC5 GC11 

rho p-value rho p-value rho p-value rho p-v

Specific conductance, μS/cm –0.95 <0.001 –0.74 <0.001 –0.76 <0.001 –0.93 <0.0

pH, standard units –.21 .168 –.13 .450 .07 .620 .34 .0

Turbidity, NTU –.22 <.001 .30 <.001 .14 <.001 .10 .0

Oxygen, dissolved, mg/L .10 .553 –.39 .023 –.69 <.001 –.37 .0

Hardness, total, mg/L as CaCO3 –.95 <.001 –.74 .001 –.83 <.001 –.95 <.0

Calcium, dissolved, mg/L –.94 <.001 –.70 .002 –.83 <.001 –.94 <.0Magnesium, dissolved, mg/L –.95 <.001 –.70 .002 –.85 <.001 –.97 <.0Sodium, dissolved, mg/L –.93 <.001 –.24 .381 –.77 <.001 –.87 <.0Potassium, dissolved, mg/L –.21 .268 –.11 .670 –.62 <.001 –.45 .0

Alkalinity (acid-neutralizing capacity), mg/L as CaCO3 –.94 <.001 –.91 <.001 –.83 <.001 .20 .3

Sulfate, dissolved, mg/L –.92 <.001 –.25 .194 –.57 <.001 –.91 <.0

Chloride, dissolved, mg/L –.69 <.001 .48 .004 –.17 .307 –.19 .2Silica, dissolved, mg/L –.70 <.001 .52 .038 –.81 <.001 –.93 <.0

Dissolved solids, sum of constituents, mg/L –.95 <.001 –.66 .005 –.80 <.001 –.98 <.0Nitrogen, ammonia, dissolved, mg/L as N –.05 .823 –.34 .163 –.17 .493 –.11 .6Nitrogen, ammonia plus organic, total, mg/L as N .43 .007 .24 .219 –.23 .154 .15 .3

Nitrogen, nitrite plus nitrate, dissolved, mg/L as N –.03 .857 –.16 .408 –.21 .191 –.11 .4Phosphorus, total, mg/L as P .30 .073 .52 .004 .06 .714 .27 .1

Phosphorus, ortho, dissolved, mg/L as P .01 .972 .29 .248 .40 .100 .13 .6Copper, dissolved, μg/L –.07 .643 .36 .056 .27 .091 –.01 .9Copper, total recoverable, μg/L –.09 .571 .45 .009 .17 .264 –.26 .0

Iron, dissolved, μg/L .22 .161 .26 .174 –.41 .009 .61 <.0Iron, total recoverable, μg/L .21 .184 .59 <.001 .15 .330 .44 .0

Lead, total recoverable, μg/L –.13 .403 .31 .086 .25 .095 .15 .3Manganese, dissolved, μg/L .21 .173 .39 .034 –.59 <.001 –.85 <.0

Manganese, total recoverable, μg/L .10 .513 .57 .001 .17 .259 –.44 .0

Zinc, dissolved, μg/L .23 .142 –.18 .339 .34 .033 –.71 <.0

Zinc, total recoverable, μg/L –.21 .179 .22 .217 .24 .116 –.55 <.0Suspended sediment, percentage finer than 0.062 mm –.70 <.001 –.77 <.001 –.49 .016 –.76 <.0

Suspended-sediment concentration, mg/L .69 <.001 .52 <.001 .57 <.001 .46 .0
38 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Table 12. Spearman’s coefficients of correlation for suspended-sediment concentration and concentrations of selected water-quality con

water years 1995–97 [rho, Spearman correlation coefficient; p-value, probability of a greater Spearman’s rho; p-values <0.05 (2-tailed) are considered highly significant and are shaded, a ligh

shade for negative correlations; Spearman’s rho’s greater than plus or minus 0.50 are shaded; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelommilligrams per liter; μg/L, micrograms per liter; mm, millimeters; <, less than; correlations based on periodic water-quality samples] Property or constituent CC2 CC5 GC5 GC11 

rho p-value rho p-value rho p-value rho p-va

Specific conductance, 

μS/cm –0.32 0.034 0.01 0.945 –0.17 0.296 –0.25 0.1

pH, standard units –.55 <.001 –.26 .214 –.29 .110 –.58 <.0

Turbidity, NTU .91 <.001 .78 <.001 .71 <.001 .87 <.0Oxygen, dissolved, mg/L .32 .077 –.22 .361 .01 .963 .34 .0Hardness, total, mg/L as CaCO3 –.28 .148 –.62 .023 –.18 .369 –.23 .2Calcium, dissolved, mg/L –.31 .105 –.63 .021 –.14 .500 –.21 .3Magnesium, dissolved, mg/L –.24 .202 –.74 .004 –.21 .288 –.26 .2Sodium, dissolved, mg/L –.25 .200 –.48 .096 –.10 .618 –.19 .3Potassium, dissolved, mg/L .47 .010 –.03 .912 .14 .490 .27 .1

Alkalinity (acid-neutralizing capacity), mg/L as CaCO3 –.44 .020 –.56 .048 –.33 .098 –.22 .2

Sulfate, dissolved, mg/L –.38 .017 –.53 .006 –.18 .286 –.10 .5

Chloride, dissolved, mg/L .07 .652 .75 <.001 –.03 .840 –.03 .8Silica, dissolved, mg/L –.74 <.001 .07 .819 –.28 .160 –.39 .0

Dissolved solids, sum of constituents, mg/L –.26 .179 –.59 .034 –.21 .301 –.28 .1

Nitrogen, ammonia, dissolved, mg/L as N .09 .730 –.09 .737 –.03 .928 .28 .2Nitrogen, ammonia plus organic, total, mg/L as N .69 <.001 .57 .003 .30 .090 .32 .0Nitrogen, nitrite plus nitrate, dissolved, mg/L as N .22 .195 –.35 .093 –.07 .700 –.21 .2Phosphorus, total, mg/L as P .81 <.001 .89 <.001 .09 .614 .29 .0Phosphorus, ortho, dissolved, mg/L as P .40 .113 .64 .005 .51 .064 .27 .2

Copper, dissolved, 

μg/L .33 .040 .27 .198 .24 .163 .15 .3

Copper, total recoverable, 

μg/L .67 <.001 .71 <.001 .51 <.001 .50 <.0

Iron, dissolved, 

μg/L .07 .659 .36 .078 –.01 .971 .18 .2

Iron, total recoverable, 

μg/L .82 <.001 .91 <.001 .59 <.001 .80 <.0

Lead, total recoverable, 

μg/L .74 <.001 .70 <.001 .52 <.001 .75 <.0

Manganese, dissolved, 

μg/L .86 <.001 .44 .028 –.37 .026 –.25 .1

Manganese, total recoverable, 

μg/L .82 <.001 .80 <.001 .59 <.001 .33 .0

Zinc, dissolved, 

μg/L .30 .057 –.11 .609 .32 .060 –.46 .0

Zinc, total recoverable, 

μg/L .61 <.001 .64 <.001 .37 .016 .22 .1

Suspended sediment, percentage finer than 0.062 mm –.18 .411 –.27 .156 –.65 <.001 .51 .0
CHARACTERIZATION OF WATER RESOURCES 39

Dissolved ammonia concentrations generally were 

less than 0.01 mg/L as N. Dissolved nitrite plus nitrate 

concentrations generally were less than 0.10 mg/L as 

N. Concentrations of dissolved orthophosphate generally were less than 0.005 mg/L as P. 

The largest nitrite plus nitrate and ammonia 

concentrations in alpine streams usually occur 

during winter low flow and early snowmelt (Stevens 

and others, 1997; Stevens, 2000). Most plants and 

bacteria that use nitrogen are inactive during winter, 

so nitrogen concentrations tend to be larger in streamflow during this period of the water year. Elution 

from snowpack and flushing of soil water high in 

nitrogen might be the cause of high nitrogen concentrations during early snowmelt (Campbell and others, 

1995).

Nitrogen concentrations increase during rainfall runoff due to the larger nitrite plus nitrate and 

ammonia concentrations in precipitation (table 4) 

than streamflow. Selected Colorado atmospheric 

deposition stations in summer 1997 had more 

nitrate and ammonia as N (average nitrate 1.1 mg/L, 

average ammonia 0.24 mg/L, table 4) than typical 

stream-water concentrations (Guanella Pass stream 

median nitrite plus nitrate 0.059 mg/L, median 

ammonia less than 0.002 mg/L, table 7). When rainfall 

reaches the ground, nitrogen can be removed by plants 

and bacteria. Increases in nitrogen are expected in 

the stream because the plants and bacteria may not 

remove all the nitrogen before the runoff reaches 

the stream. Sites with large impervious drainage 

areas, such as roads and rock outcrops, may have 

larger nitrogen concentrations during runoff because 

the runoff gets to the stream more rapidly, retaining 

more nitrogen.

Total ammonia plus organic nitrogen and 

total phosphorus concentrations were highest during 

snowmelt runoff and summer storms (Stevens and 

others, 1997; Stevens, 2000). These analytes include 

the particulate contribution, which is large during 

periods of suspended-sediment transport. Total 

ammonia plus organic nitrogen concentrations 

usually did not exceed 1 mg/L as N except in some 

storm samples. Total phosphorus concentrations 

ranged from less than 0.001 to 3.2 mg/L as P; medians 

ranged from 0.002 to 0.020 mg/L as P (table 7, 

CC1

CC2CC4

CC5CC6CC7CC10

DISTANCE FROM GUANELLA PASS, IN MILES

VALUE OR CONCENTRATION

0

120

20

40

60

80

100

0 2 4 6 8 10 12 14

Water discharge

Specific conductance

pH

Figure 13. Values and concentrations of specific conductance (in microsiemens per centimeter at 

25 degrees Celsius), pH (in standard units), and instantaneous water discharge (in cubic feet per 

second) at water-quality-sampling sites along South Clear Creek during low-flow synoptic sampling, 

September 6, 1995.
40 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Appendix tables 36–49). Comparison of total and 

dissolved nutrient concentrations (Stevens and others, 

1997) indicates that during snowmelt and storm 

events, particulate organic nitrogen and particulate 

phase phosphorus predominate. At low flows, nutrients were transported mainly in the dissolved phase in 

small concentrations. 

Dissolved nutrients (nitrate, ammonia, and 

orthophosphorus) were not significantly correlated 

with specific conductance or streamflow (tables 9 

and 11). Total ammonia plus organic nitrogen, 

however, which includes particulate-related nitrogen, 

had a significant but weak positive correlation with 

streamflow at site CC2 (table 11), a significant but 

CC1

CC2CC4CC5

CC6

CC7

CC10

0 2 4 6 8 10 12 14

0

60

10

20

30

40

50

PERCENTAGE OF MAJOR CATIONS

0 2 4 6 8 10 12 14

DISTANCE FROM GUANELLA PASS, IN MILES

0

100

20

40

60

80

PERCENTAGE OF MAJOR ANIONS

Calcium

Magnesium

Sodium

Potassium

Bicarbonate

Sulfate

Chloride

Fluoride

Figure 14. Percentages of major ions at water-quality-sampling sites along South Clear Creek during 

low-flow synoptic sampling, September 6, 1995.
CHARACTERIZATION OF WATER RESOURCES 41

weak negative correlation with specific conductance 

at site CC2 (table 9), and significant positive correlations with suspended sediment at sites CC2, CC5, 

and DC1 (table 12). Total phosphorus, which also 

includes particulate-related phosphorus, had significant but weak positive correlations with streamflow 

at sites CC2 and CC5 (table 11), no significant correlations with specific conductance (table 9), and strong 

significant positive correlations with suspended sediment at sites CC2, CC5, and DC1 (table 12). The 

nutrient correlations at some sites (CC2, CC5, DC1) 

reinforce the indications that particulate nutrients

 are transported during periods of high flow when 

suspended-sediment concentrations are large, 

such as during snowmelt and storm runoff. 

Trace Elements

Trace elements in this study are defined as 

inorganic chemical elements, excluding nutrients, 

found in natural water in small quantities, mostly 

less than 1 mg/L (Hem, 1985). Sometimes 

aluminum, barium, iron, and manganese exceeded 

1 mg/L, but for the purposes of this study, they are 

still considered to be trace elements. The occurrence of trace elements can be separated into two 

types of sites: sites with acid-sulfate weathering 

processes in the watershed and sites unaffected by 

acid-sulfate weathering processes (table 14). If a 

site was located downstream from the mining areas 

on Geneva, Leavenworth, or South Clear Creeks, it 

was considered an affected site.

Table 13. Estimates of mass of chloride in dust inhibitor applied to Guanella Pass road and annual chloride load and 

hypothetical concentration estimates in South Clear Creek at site CC5

[MgCl2, magnesium chloride; WY, water year; loads are in tons; daily mean water discharge in cubic feet per second; FWMC is the annual flow-weightedmean concentration in milligrams per liter, and is annual load (tons) divided by annual mean flow (ft3

/s) divided by 0.0027 divided by number of days in 

the year; Assumptions: Applied brine = 30% MgCl2 by weight; density = 10.8 lbs/gal; pure MgCl2 = 74.5% chloride by weight; County application rates 

and locations as described in this report; width of application on road = 18 feet]

Mass of chloride in MgCl2 applied in Guanella Pass area WY’s 1995–97

Year 1987 1993 1996

Load 79.3 22.2 24.1

Mass of chloride in MgCl2 applied to road in CC5 basin WY’s 1995–97

Year 1987 1993 1996

Load 57.1 11.5 15.5

Annual chloride loads in South Clear Creek at site CC5

Year 1995 1996 1997

Load 27.4 5.59 8.4

Annual total dissolved solids loads in South Clear Creek at site CC5a

Year 1995 1996 1997

Load 597 437 554

Year Daily mean

water discharge

Estimated actual

chloride load

Estimated

FWMC

Annual flow-weighted-mean concentrations of chloride at site CC5

1995 15.3 27.4 1.8

1996 10.7 5.59 0.5

1997 14.0 8.4 0.6

Year Daily mean

water discharge

Estimated 1996

chloride load plus

1987 chloride mass

from applied MgCl2

Hypothetical

FWMC

Hypothetical scenario using largest application and annual flows and chloride loads at CC5

1995 15.3 84.5 5.6

1996 10.7 62.7 5.9

1997 14.0 65.5 4.7

a

Data from table 10.
42 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

 In areas unaffected by acid-sulfate weathering, 

dissolved trace-element concentrations, excluding 

aluminum, barium, iron, and manganese, were small, 

generally less than 10 μg/L (Stevens and others, 1997; 

Stevens, 2000). The most frequently detected 

dissolved trace elements (excluding aluminum, 

barium, iron, and manganese) among streams unaffected by acid-sulfate weathering were zinc (range 

less than 3 to 20 μg/L) and copper (range less than 1 

to 4 μg/L). Concentrations of dissolved lead and 

cadmium almost never exceeded the 1-μg/L laboratory 

MRL (Stevens and others, 1997; Stevens, 2000).

Streams located in areas of ore deposits and 

pyritic rocks are affected by acid-sulfate weathering: 

Geneva Creek (sites GC6, GC7, GC9, GC11, GC12), 

Leavenworth Creek (sites CC8 and CC9), and South 

Clear Creek downstream from Leavenworth Creek 

(site CC10). Characteristics of affected streams are 

large sulfate, iron, and other trace-element concentrations (table 14; Stevens and others, 1997). Acidic 

pH also is a characteristic, but it is not the defining 

factor. The pH can be neutralized downstream, but 

high concentrations of trace elements can persist, 

commonly in the suspended fraction or as streambed 

precipitates. 

 Total recoverable trace-element concentrations 

usually increase as the suspended-sediment concentration increases (table 12). This increase is due to total 

recoverable analyses incorporating the portion of the 

sample that is soluble in a mild-acid extraction. Thus, 

much of the trace element adsorbed to the suspended 

sediment will be a part of the concentration that would 

be removed by filtration in a dissolved analysis. In 

the Guanella Pass area, iron, manganese, barium, and 

aluminum occurred in large total recoverable concentrations (table 14). 

Despite the presence of substantial traceelement sources in basins with pyritic rocks (upper 

Geneva Creek and Leavenworth Creek), maximum 

total recoverable trace-element concentrations were 

not always larger in streams affected by acid-sulfate 

weathering than those in unaffected streams (table 14). 

During snowmelt and rainstorm runoff, which are 

periods of large suspended-sediment concentrations, 

concentrations of total recoverable copper, chromium, 

iron, and manganese in some streams (CC2 and CC5) 

unaffected by acid-sulfate weathering exceeded 

maximum concentrations sampled in affected 

streams (table 14).

The solubility of trace elements in water is 

affected by pH. Generally, the most soluble chemical 

forms of a trace element occur in acidic waters, 

whereas the most insoluble chemical forms occur in 

neutral or basic waters. The pH at which an element 

becomes soluble is different for each element. In 

the case of stream water, the stream pH may change 

from acidic to neutral as alkaline-tributary flows are 

added downstream. Elements that were soluble 

0.001

1

0.002

0.003

0.004

0.005

0.007

0.01

0.02

0.03

0.04

0.05

0.07

0.1

0.2

0.3

0.4

0.5

0.7

INSTANTANEOUS CHLORIDE LOAD,

IN TONS PER DAY

Best-fit line 

Chloride load = (0.0071)eq(0.0553)

Adjusted r-squared = 0.80

Root mean squared error = 0.53

0 10 20 30 40 50 60 70

INSTANTANEOUS WATER DISCHARGE, IN CUBIC FEET PER SECOND

80

EXPLANATION

1995

1996

1997

Best-fit ordinary 

least-squares 

regression line

Figure 15. Relation of chloride load with instantaneous water discharge at site CC5, water years 1995–97.
C

HARACTERIZATIONOFWATERRESOURCES43

Table 14. Summary of trace-element data ranges for sites that are affected and sites that are unaffected by acid-sulfate weathering in t[Affected sites: CC8, CC9, CC10, GC6, GC7, GC9, GC11, and GC12; unaffected sites: CC1, CC2, CC3, CC4, CC5, CC6, CC7, CC11, CC12, CC13, GC1, GC2, GC3, Gfrom Stevens and others (1997), Stevens (2000), and Appendix tables 34–47; multiple, many sites; μg/L, micrograms per liter; <, less than]

Constituent Units Acid-sulfate weathering No acid-sulfat

Maximum Site Minimum Site Maximum Site 

Aluminum, total recoverable as Al μg/L 11,000 GC11 30 CC10 4,600 GC8 Aluminum, dissolved as Al μg/L 4,700 GC6 6 CC10 140 GC8 Antimony, dissolved as Sb μg/L <1 multiple <1 multiple <1 multiple Arsenic, total recoverable as As μg/L <1 multiple <1 multiple <1 multiple Barium, total recoverable as Ba μg/L 100 GC11 <100 multiple 100 GC8 Barium, dissolved as Ba μg/L 38 GC7 18 GC11 31 multiple Beryllium, total recoverable as Be μg/L <10 multiple <10 multiple <10 multiple Beryllium, dissolved as Be μg/L <1 multiple <1 multiple <1 multiple Cadmium, total recoverable as Cd μg/L 2 GC6, GC9 <1 multiple <1 multiple Cadmium, dissolved as Cd μg/L 2 GC6 <1 multiple <1 multiple Chromium, total recoverable as Cr μg/L 16 GC11 <1 multiple 20 CC2 Chromium, dissolved as Cr μg/L <1 multiple <1 multiple 2 GC5 Cobalt, total recoverable as Co μg/L 10 GC11 <1 multiple 10 GC8 Cobalt, dissolved as Co μg/L 8 GC6 <1 multiple <1 multiple Copper, total recoverable as Cu μg/L 53 GC11 1 CC9 92 CC5 Copper, dissolved as Cu μg/L 37 GC6 <1 CC10, GC11 4 DC1 Iron, total recoverable as Fe μg/L 47,000 GC6 10 CC9 110,000 CC5 Iron, dissolved as Fe μg/L 1,800 GC6 <3 GC11 720 CC1 Lead, total recoverable as Pb μg/L 71 CC9 <1 multiple 54 CC2 Lead, dissolved as Pb μg/L 2 CC9, GC12 <1 multiple <1 multiple Manganese, total recoverable as Mn μg/L 900 GC11 <10 CC9 2,300 CC5 Manganese, dissolved as Mn μg/L 760 GC6 2 CC10 130 CC2 Mercury, total recoverable as Hg μg/L .1 GC6 <.1 multiple <.1 multiple Molybdenum, total recoverable as Mo μg/L 2 multiple <1 multiple 2 multiple Molybdenum, dissolved as Mo μg/L <1 multiple <1 multiple <1 multiple Nickel, total recoverable as Ni μg/L 17 GC11 <1 CC10 17 GC8 Nickel, dissolved as Ni μg/L 17 GC6 <1 CC10 2 GC8 Selenium, total recoverable as Se μg/L <1 multiple <1 multiple <1 multiple Silver, total recoverable as Ag μg/L <1 multiple <1 multiple <1 multiple Silver, dissolved as Ag μg/L 1 GC12 <1 multiple 2 GC10 Zinc, total recoverable as Zn μg/L 430 CC9 <3 GC11 360 CC5 Zinc, dissolved as Zn μg/L 320 GC6 6 GC12 20 GC5 Uranium, natural, dissolved μg/L 2 GC6 <1 multiple <1 multiple 
44 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

and in the dissolved phase (operationally defined as 

passing through a 0.45-μm filter) become insoluble 

and precipitate on the streambed or are transported 

downstream in the suspended fraction. In Geneva 

Creek, at site GC6 September 1995, most of the 

copper load was in the dissolved phase (fig. 16). 

As the stream flowed downstream from GC6 to GC12, 

the pH changed from 3.8 to 7.4. Dissolved copper 

decreased sharply in a downstream direction while 

total recoverable copper remained fairly steady, 

GC6

GC7GC9GC11

GC12

0

80

20

40

60

2

8

4

6

0

0.2

0.1

0

0.0015

0.0005

0.0010

LOAD, IN TONS PER DAY

pH, STANDARD UNITS

WATER DISCHARGE, IN

CUBIC FEET PER SECOND

4 6 8 10 12 14 16 18 20 22

Water discharge, in cubic feet per second

4 6 8 10 12 14 16 18 20 22

pH, in standard units

4 6 8 10 12 14 16 18 20 22

Total recoverable

aluminum

Dissolved

aluminum

4 6 8 10 12 14 16 18 20 22

DISTANCE FROM CONTINENTAL DIVIDE, IN KILOMETERS

Total recoverable 

copper

Dissolved 

copper

Figure 16. Variations in selected dissolved-phase and total recoverable trace-element loads along Geneva 

Creek from GC6 to GC12 during low-flow synoptic sampling, September 1995.
CHARACTERIZATION OF WATER RESOURCES 45

indicating that most of the copper changed to a 

suspended-solid phase. Most of the aluminum and 

iron were in the dissolved phase at site GC6, but both 

precipitated prior to reaching GC9. The pH change did 

not affect manganese and zinc as much because the 

data indicate that most of the loads remained in the 

dissolved phase from GC6 to GC12 (fig. 16).

Evidence of the trace-element phase change 

along Geneva Creek can be observed as orange and 

white precipitates, probably of iron and aluminum 

compounds, formed at confluences with tributaries and 

along the streambed as in other acidic/neutral-stream 

mixing zones in the region (Bassett and others, 1992; 

McKnight and others, 1992). Precipitates accumulate 

on the Geneva Creek streambed during low flow. 

These precipitates, whose smothering action causes 

a physical stress on aquatic life, can have a more negative effect than trace-element toxicity (Dev Niyogi, 

U.S. Geological Survey, oral commun., 1999). Then, 

during high flow, the precipitates on the streambed are 

scoured, representing a substantial source of particulate 

iron, aluminum, and other trace elements which are 

potentially adsorbed to the amorphous phases of iron 

and aluminum, suspended sediments, and organic particles dislodged from the streambed.

Spearman correlations of dissolved trace 

elements with streamflow (table 11) show that dissolved 

trace elements were sometimes significantly correlated. 

GC6GC7

GC9

GC11GC12

4 6 8 10 12 14 16 18 20 22

0

0.10

0.05

Total recoverable

iron

Dissolved

iron

4 6 8 10 12 14 16 18 20 22

0.02

0.04

0.03

Dissolved 

manganese

Total 

manganese

4 6 8 10 12 14 16 18 20 22

DISTANCE FROM CONTINENTAL DIVIDE, IN KILOMETERS

0.006

0.012

0.008

0.010

Total recoverable

zinc

Dissolved

zinc

LOAD, IN TONS PER DAY

Figure 16. Variations in selected dissolved-phase and total recoverable trace-element loads along Geneva 

Creek from GC6 to GC12 during low-flow synoptic sampling, September 1995—Continued.
46 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

The strongest correlations were negative or inverse 

and were at site GC11 for manganese and zinc; both 

elements transported mostly in the dissolved phase 

at GC11. 

Dissolved trace elements were significantly 

correlated with specific conductance (table 9) at GC11 

for iron (negative), manganese (positive), and zinc 

(positive). GC5 also had significant positive correlations 

with specific conductance for iron and manganese.

Dissolved trace elements were not generally 

correlated with suspended-sediment concentration 

(table 12). Dissolved manganese was significantly 

but weakly correlated with suspended sediment at 

CC5 (positive), GC5 (negative), and DC1 (positive) 

and was strongly and positively correlated at CC2.

Total recoverable trace elements and streamflow (table 11) were not well correlated at most sites. 

However, GC11, a site with large dissolved proportions of manganese and zinc, had negative correlations 

with streamflow for those elements, likely a result of 

dilution.

Total recoverable trace elements were significantly correlated with specific conductance (table 9) 

only at GC11 where there were significant positive 

correlations with manganese and zinc and a negative 

correlation with iron.

Spearman correlations of total recoverable 

trace elements with suspended-sediment concentrations (table 12) were significant and positive at all sites 

for copper, iron, lead, and manganese. Significant and 

positive correlations with suspended sediment were 

computed for zinc at CC2, CC5, and GC5. Positive 

correlation with suspended-sediment concentration 

was a result of the tendency for trace elements to be 

adsorbed to suspended sediment and for the majority 

of trace-element concentrations to be associated with 

the particulate phase (insoluble chemical forms) during 

periods of suspended-sediment transport. 

Suspended Sediment, Turbidity, 

and Streambed-Particle Size

Monitoring of suspended sediment, turbidity, 

and streambed particle size was initiated because the 

existing road and the reconstruction project might 

cause erosion along the road and in receiving areas for 

road runoff, increase suspended-sediment transport, 

decrease water clarity, and contribute to deposits on 

the streambed. Some sites were intensely sampled 

with automated pumping samplers that produce detailed 

records of daily suspended-sediment discharge. At 

other sites, periodic samples of suspended sediment 

were manually collected to define a suspendedsediment transport relation. Streambed particle-size 

data were collected at selected sites.

Basin Characteristics of Suspended-Sediment Sites

Basin characteristics for Guanella Pass 

sediment-discharge computation sites are listed in 

table 15. Drainage areas for sediment-discharge computation sites ranged from 2.19 mi2 (CC2) to 74.6 mi2

(GC11). Several sites had similar drainage areas: CC5 

(11.8 mi2

), CC7 (16.0 mi2), CC9 (12.0 mi2), and DC1 

(13.4 mi2). Road density in each of the basins varied 

from 0.0 mi/mi2

 (DC1 and CC1, roadless areas) to 

1.05 mi/mi2

 (CC9, an area with a network of old mining 

roads). Other sites ranged from 0.23 mi/mi2 (GC11) to 

0.65 mi/mi2

 (CC2). The length of roads in a basin has 

been positively correlated with sediment yield in 

forested basins in Washington (Reid and Dunne, 1984).

Lakes, reservoirs, and beaver ponds can accumulate sediment and complicate basin sediment-yield 

computations by reducing downstream transport. All 

of the basins in the study area probably are affected to 

a degree by beaver dams. Upper Geneva Creek, Duck 

Creek, and upper South Clear Creek have large, active 

beaver dam complexes. Some of the observed beaver 

dams on active stream channels have large sediment 

deposits behind them. The trapping effect of beaver 

dams on sediment is probably less for suspended sediment than it is for bedload because of smaller grain 

sizes. Abandoned beaver dams show evidence of 

dissection of the dam and deposited sediment, which 

act as sediment sources as they are eroded. Duck Lake, 

Naylor Lake, Lower Cabin Creek Reservoir, and Clear 

Lake also trap portions of the sediment load from 

Duck Creek and South Clear Creek Basins and lessen 

the transport of sediment to downstream reaches. 

The Vidler Tunnel diversions into Leavenworth 

Creek may affect the hydraulics and, thus, the sediment transport characteristics of Leavenworth Creek 

by importing water from Peru Creek. However, 

1995–97 flow records show that Vidler Tunnel 

water was diverted mainly during July and August 

(Charles Schaffer, Colorado State Engineer’s 

Office, written commun., 1999), when natural flows 

in Leavenworth Creek were rapidly receding, possibly 

increasing sediment transport. However, the tunnel 

water did not contribute to the highest flows in May 

and June, which transported the bulk of suspendedsediment loads.
CHARACTERIZATION OF WATER RESOURCES 47

Table 15. Basin characteristics of suspended-sediment discharge monitoring sites and upstream/downstream paired sites[mi2, square miles; ft, feet; <, less than; >, greater than; ≥, equal to or more than; valley trend is the general downstream bearing (map direction); basin gradient, basin rebasin; road density, length of roads in the basin divided by drainage area; CC1/CC2 and CC13/CC5 are upstream/downstream paired sites]

Site

(fig. 1)

Drainage

area

(mi2)

Valley

trend

Range in

altitude

(ft)

Basin

gradient

(ft/ft)

Range in

annual

precipitation

 (inches)

Geology

Vegetation/

cover

Land-use

factors

Major Minor

CC1 1.1 northwest 12,988–11,200 0.19 30–40 granite glacial drift, 

gneissic metasediments

tundra, 

conifer

primitive campin

CC2 2.19 northwest 12,988–10,710 .15 30–40 granite glacial drift, 

gneissic metasediments

tundra, 

conifer

primitive campin

road

CC5 11.8 north 13,794–10,200 .12 25≥30 gneissic 

metasediments

granite, glacial drift aspen/ 

conifer, tundra

developed and 

primitive camping, road

CC7 16.0 north 13,794–9,270 .10 16≥30 gneissic 

metasediments

granite, glacial drift aspen/ 

conifer, tundra

developed and 

primitive camping, hydrelectric generation, road

CC9 12.0 northeast 13,850–9,270 .13 16≥30 gneissic 

metavolcanics

glacial drift, 

gneissic metasediments

tundra, aspen/ 

conifer

primitive campin

mining, roads

CC13 7.2 north 13,794–10,705 .16 25≥30 gneissic 

metasediments

glacial drift, 

gneissic metasediments

aspen/ 

conifer, tundra

developed and 

primitive camping, road

GC5 7.78 south 13,680–9,760 .35 20–30 gneissic 

metasediments

granite, glacial drift aspen/ 

conifer, tundra

primitive campin

residential, grazing, road

GC11 74.6 southeast 13,794–8,760 .21 <16–40 gneissic 

metasediments

granite, glacial drift aspen/ 

conifer, tundra

primitive campin

mining, residetial, grazing, road

DC1 13.4 southeast 13,575–9,280 .15 20–30 gneissic 

metavolcanics

granite, glacial drift aspen/ 

conifer, tundra

primitive campin
48 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Suspended-Sediment Concentrations and Loads

Suspended-sediment concentration data are 

listed in Stevens and others (1997) and Stevens (2000). 

Suspended sediment is defined as the particles (mostly 

rock fragments, soil, and some organic material) 

suspended in the water column by the turbulence of 

the water. Suspended-sediment discharge usually is 

only a portion of the total sediment discharge, which 

also includes the bedload. Bedload is the sediment 

transported by bouncing, rolling, and skidding along 

the streambed. Summary statistics of concentrations 

and percentage finer than 0.062 mm for each site 

with more than two samples are listed in Appendix 

tables 36–49 and table 7. Suspended-sediment concentrations vary by season—large (greater than 10 mg/L 

to hundreds of milligrams per liter) during snowmelt 

and rainstorm periods, small (less than 10 mg/L) 

during low-flow and winter periods. Suspendedsediment concentrations collected by equal-width 

integrated (EWI) methods (Edwards and Glysson, 

1988) ranged from less than 1 mg/L at many sites 

during low flow to 1,180 mg/L at site CC2 during 

stormflow. Median suspended-sediment concentrations (EWI) were generally less than 20 mg/L 

(fig. 10). Larger concentrations occurred, indicated by 

sample concentrations from pumping samplers during 

rainstorms. Pumping samplers that collect stream 

water at a single point, however, do not average the 

variability in concentration at various depths and 

widths of the stream cross section. Thus, single-point 

samplers are less accurate and could under- or overestimate suspended-sediment concentrations. An 

example of the seasonal and year-to-year variations, 

and the general positive correlation with streamflow 

of suspended-sediment concentration and discharge, 

is shown in figure 17 for Geneva Creek (GC11). 

Sites on two reaches on South Clear Creek, CC1 

to CC2 and CC13 to CC5 (fig. 12), during WY 1997 

were used to examine the suspended-sediment concentration changes within a stream reach that closely parallels the Guanella Pass road. Samples were collected at 

the sites in downstream order, closely spaced in time. 

Upstream sites of each pair generally had smaller 

suspended-sediment concentrations than the downstream sites during May and early June and in a rainstorm sample on July 28, 1997 (CC1/CC2) (fig. 12). 

These dates correspond to the periods of road runoff. 

Suspended-sediment discharge is the rate 

of suspended sediment transported by a stream 

(commonly expressed as tons per day). Incremental 

suspended-sediment discharges can be computed and 

summed to determine the weight of sediment transported in a period of time, typically a water year. 

In this study, suspended-sediment discharge was 

computed by two methods. One, selected sites 

were intensely sampled by automatic pumping 

samplers, and daily suspended-sediment discharge 

was computed using the SEDCALC program 

(Koltun and others, 1994). For this method, sufficient 

suspended-sediment concentration data are collected 

each day to compute an average daily suspendedsediment discharge. Daily mean suspended-sediment 

discharges computed by this method are listed in 

Stevens (2000).

A second method was used at sites where 

continuous water-discharge record was available and 

periodic suspended-sediment samples were collected. 

Transport relations were computed and sediment 

discharge estimated using instantaneous streamflows 

from the gaging station. One to three regression equations (table 16), bias corrected (Duan, 1983), were 

developed on the basis of hydrograph periods (fig. 5): 

1. A rising-limb period was defined as the period 

between the day of the upturn in the hydrograph 

at the beginning of snowmelt to the day of the 

peak daily mean streamflow of the snowmelt 

period. 

2. A falling-limb period was defined as the period 

from the day after the peak daily mean streamflow to the day when discharge decreases to 

25 percent of the peak daily mean streamflow 

(generally near the end of July or early August). 

3. Base flow (includes summer low flow) was defined 

as the period from the end of the falling-limb 

period to the beginning of the rising-limb period. 

4. Storm days were assumed to be those days that had 

increases in streamflow or suspended-sediment 

concentrations related to rainstorms. Summer 

stormflow relations between suspended-sediment 

load and water discharge were poorly correlated 

and were not used. Not using the stormflow 

relations could underestimate the suspendedsediment contributions from rainstorms for 

the summer period. Suspended-sediment 

discharge computations and equations for this 

method are similar to those discussed previously 

in the “Dissolved-Solids Loads” section.
CHARACTERIZATION OF WATER RESOURCES 49

Annual suspended-sediment discharges and 

yields computed by both methods for all sites, 

WY’s 1995–97, are listed in table 17. Suspendedsediment discharges were highly variable during the 

study period. Instantaneous suspended-sediment 

discharge (based on EWI samples) ranged from 

0.001 T/d (CC1, CC2) to 1,370 T/d (GC11) (table 7). 

During WY’s 1995–97, annual suspended-sediment 

discharge ranged from 21.9 tons at CC2 (WY 1996) to 

11,500 tons at GC11 (WY 1995). During water 

year 1995, suspended-sediment transport was more 

than an order of magnitude higher at some sites than 

transport during WY 1996. Relations between annual 

suspended-sediment discharge and annual streamflow 

(fig. 18) and between annual suspended-sediment 

discharge and drainage basin area (fig. 19) indicate 

1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

0.1

10,000

0.2

0.5

1

2

5

10

20

50

100

200

500

1,000

2,000

5,000

EXPLANATION

Daily mean streamflow,

in cubic feet per second

Daily mean suspended-sediment 

discharge, in tons per day

EXPLANATION

Daily mean streamflow, 

in cubic feet per second

Flow-weighted-mean 

suspended-sediment 

concentration, 

in milligrams per liter

OND J FMAM J J ASOND J FMAM J J ASOND

1994 1995 1996

J FMA MJ J A S

1997

OND J FMAM J J A SOND J FMAM J J A SOND J FMAM J J AS

1994 1995 1996 1997

Figure 17. Variation in daily mean water discharge, daily flow-weighted-mean suspended-sediment 

concentration, and daily mean suspended-sediment discharge at site GC11, water years 1995–97.
50 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

that annual suspended sediment at each site is proportional to annual flow, and large basins tend to produce 

large loads.

The relation between suspended-sediment yield 

(tons/mi2) and water yield (fig. 20) indicates that 

annual yields in the South Clear Creek Basin (at CC5, 

basin area, 11.8 mi2) tend to be larger than the Deer 

Creek Basin (at DC1, an undisturbed reference basin, 

area 13.4 mi2) at equivalent annual flows, but are 

similar to the Leavenworth Creek Basin (at CC9, 

basin area 12.0 mi2).

Comparison-Site Suspended-Sediment Yields

Guanella Pass suspended-sediment yields 

were compared to 11 mountainous stream sites with 

basins of crystalline (igneous or metamorphic) 

geology and mostly rural land uses in Colorado 

(Elliott and DeFeyter, 1986) to determine if Guanella 

Pass suspended-sediment yields were within the 

general range of computed yields of other basins with 

the similar general bedrock type, land use, and topography in the region. Generalized basin characteristics 

for these comparison sites are listed in table 18. 

Table 16. Regression coefficients and information used to compute suspended-sediment loads at selected sites, water 

years 1996–97

[r, rising limb of annual snowmelt hydrograph; f, falling limb of annual snowmelt hydrograph; b, base-flow period; <, less than]

Site

(fig. 1)

Hydrologic

period

Water

year

Number of 

samples

Natural logarithm form: LN(Ls) = a + b LN (Qw)

Exponentiated form: 

Ls = e(a)Qw

(b)Cb

Coefficient and p-values

Standard

error

Coefficient of

determination

(r2)

Bias

correction

factor

(Cb)

a p-value b p-value

CC2 r 1996 13 –3.859 0.0044 1.568 0.0043 0.99 0.50 1.477 Ls = (0.0312)Qw

(1.568)

CC2 f/b 1996 32 –5.112 <.0001 1.495 <.0001 .47 .93 1.098 Ls = (0.0066)Qw

(1.495)

CC5 r 1996 17 –2.910 .0005 1.437 <.0001 .86 .74 1.358 Ls = (0.0740)Qw

(1.437)

CC5 f/b 1996 47 –5.371 <.0001 1.505 <.0001 .70 .83 1.254 Ls = (0.0058)Qw

(1.505)

CC7 r/f/b 1996–97 47 –5.048 <.0001 1.209 <.0001 .91 .62 1.471 Ls = (0.0094)Qw

(1.209)

CC9 r 1997 17 –8.587 <.0001 2.439 <.0001 1.10 .73 1.765 Ls = (0.00034)Qw

(2.439)

CC9 f/b 1997 36 –5.476 <.0001 1.453 <.0001 .84 .86 1.409 Ls = (0.0059)Qw

(1.453)

Table 17. Summary of annual suspended-sediment discharges and suspended-sediment yields at selected sites, water 

years 1995–97

[tons/yr, tons per year; tons/mi2, tons per square mile; tons/acre-ft, tons per acre-foot; --, no data]

Site

(fig. 1)

Water year 1995 Water year 1996 Water year 1997

Suspendedsediment 

discharge 

(tons/yr)

Suspendedsediment 

yield 

(tons/mi2)

Suspendedsediment

yield

(tons/

acre-ft)

Suspendedsediment 

discharge 

(tons/yr)

Suspendedsediment 

yield 

(tons/

mi2)

Suspendedsediment

yield 

(tons/

acre-ft)

Suspendedsediment 

discharge 

(tons/yr)

Suspendedsediment 

yield 

(tons/

mi2)

Suspendedsediment

yield 

(tons/

acre-ft)

CC2 -- -- -- 21.9 10.0 0.018 103 47.0 0.064

CC5 1,430 121 0.129 187 15.8 .024 319 27.0 .032

CC7 1,400 87.5 .091 112 7.00 .009 133 8.31 .010

CC9 1,760 147 .137 230 19.2 .023 278 23.2 .025

GC5 74.0 9.51 .014 29.7 3.82 .007 78.5 10.1 .016

GC11 11,500 154 .193 576 7.72 .014 1,760 23.6 .035

DC1 -- -- -- 36.4 2.72 .006 326 24.3 .027
CHARACTERIZATION OF WATER RESOURCES 51

Streamflow and suspended-sediment yields for the 

sites are listed in table 19. The period of record 

for the comparison sites was not the same as the 

Guanella Pass study and could affect the suitability 

of the comparisons. Suspended-sediment yields per 

acre-foot of water discharge at Guanella Pass sites 

(table 17) were within the range of the mean yields 

of the comparison basins (table 19) except for water 

year 1995, when the Guanella Pass yields were much 

larger than the means but still within the range 

of the maximum yields. 

Sediment Discharge by Hydrograph Period

The annual contribution of suspended-sediment 

load for three periods and the load contribution on 

days with summer storms (July to September) were 

computed (table 20) for the purpose of understanding 

how much suspended sediment each seasonal period 

contributes and whether those periods correspond 

to times when road runoff to streams occurs. 

The hydrograph periods (fig. 5) are the same as 

described in the previous discussion of sediment 

load computation: (1) Rising limb of the annual 

snowmelt water-discharge hydrograph, (2) falling 

limb, (3) base/summer low-flow period, (4) and 

summer stormflow.

Results indicate that approximately 80 percent 

or more of the suspended sediment was transported 

during the rising and falling limbs of the annual snowmelt hydrograph (about May to July). The shape of 

the hydrograph was important in that a sharp rise 

followed by a long, falling-limb recession produced 

a greater contribution for the falling limb despite 

larger flow-weighted-mean concentrations of 

suspended sediment during the rising limb. Guanella 

Pass suspended-sediment transport seems similar to 

many areas in Colorado in that suspended-sediment 

loads were generally larger during the rising-limb 

period than loads at the same discharge during the 

falling-limb period (Elliott and DeFeyter, 1986). 

This relation could indicate a limited supply of 

suspendable sediment that is exhausted during the 

rising portion of the annual snowmelt hydrograph. 

The annual contributions from low-flow and stormflow periods were relatively small, and stormflow 

contributions were generally smaller than those 

from low-flow periods. 

Road runoff was produced by melting, primarily 

during the month of May, which corresponds to the 

rising-limb period of area stream hydrographs. By 

analyzing suspended-sediment discharge/waterdischarge relations during the rising limb, differences 

1,000 2,000 5,000 10,000 20,000 50,000 100,000

ANNUAL STREAMFLOW, IN ACRE-FEET PER YEAR

10

100,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

SUSPENDED-SEDIMENT DISCHARGE,

IN TONS PER YEAR

CC7

CC9

GC5

GC11

DC1

EXPLANATION

CC2

CC5

Figure 18. Relation of suspended-sediment discharge to annual streamflow for selected sites, water 

years 1995–97.
52 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

in transport at sites receiving road runoff might be 

distinguished. Figure 21 shows sediment-transport 

relations (table 21) for the 1995–97 rising limb 

of the hydrograph at sites with annual suspendedsediment monitoring (CC2, CC5, CC7, CC9, GC5, 

GC11, and DC1). Site DC1 is considered to be a 

site with an undisturbed land use. Also, rising-limb 

suspended-sediment discharges, computed at sites 

with undisturbed land use (CC1, CC11, GC1, GC8, 

and GC10), were pooled to produce a regression line 

called REF (for undisturbed reference sites). These 

sites did not have enough data to compute a regression 

for each site.

Generally, most of the regression lines occupy 

a narrow band with a similar slope. The rising-limb 

transport relations for sites CC2 and CC5 indicate 

larger suspended-sediment discharge at a given 

streamflow than other sites in the study. CC2, a site 

with a small contributing drainage area, has steeper 

source areas and gradient, which might cause larger 

suspended-sediment discharges for a given water 

discharge. But results for site CC5, which has a similar 

contributing basin area as DC1 and CC9, indicate a 

larger rate of rising-limb suspended-sediment transport. Transport relations, yield comparisons, and peak 

rain-event suspended-sediment concentrations indicate 

that upper South Clear Creek, a basin receiving road 

runoff, had a larger rate of suspended-sediment transport than a similar-sized, undeveloped basin (Deer 

Creek near Bailey).

Turbidity

Turbidity is a measure of water clarity, which 

is affected primarily by the presence of suspended 

matter. Data documenting preconstruction variability 

in turbidity are important because turbidity could 

be used for project monitoring during construction. 

Turbidity was routinely measured with water-quality 

and suspended-sediment samples (Stevens and others, 

1997; Stevens, 2000). Turbidity is easily measured and 

results are available immediately, allowing changes in 

water clarity to be identified. Increased turbidity is an 

indication of the reduction of light penetration crucial 

to sustaining periphyton (algae). Decreases in light 

penetration can reduce algal primary productivity 

and affect the feeding habits of fish (MacDonald 

and others, 1991). 

Turbidity fluctuates with discharge (fig. 22). 

Understanding that turbidity fluctuates widely in 

short periods during runoff is important because preexisting fluctuation behavior could be mistaken for the 

effects of future construction near the stream. Continuous turbidity sensors such as the one that produced 

10

50,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

SUSPENDED-SEDIMENT DISCHARGE,

IN TONS PER YEAR

1 2 5 10 20 50 100

DRAINAGE AREA, IN SQUARE MILES

CC7

CC9

GC5

GC11

DC1

EXPLANATION

CC2

CC5

Figure 19. Relation of suspended-sediment discharge to drainage-basin area for selected sites, water 

years 1995–97.
CHARACTERIZATION OF WATER RESOURCES 53

the data for figure 22 were tried at sediment-collection 

sites, but fouling and bubbles from turbulence affected 

the record. The use of continuous turbidity monitors 

to trigger sampling equipment under these conditions 

does not yet seem feasible.

Turbidity was generally measured with each 

suspended-sediment sample collected. The statistical 

summaries (table 7 and Appendix tables 36–49) 

include only turbidity measured simultaneously with 

periodic suspended-sediment samples because the 

entire data set of turbidity may overrepresent some 

flow regimes because of the differences in collection 

frequency of pumped suspended-sediment samples. 

In general, turbidity at low and winter flows was less 

than 5 nephelometric turbidity units (NTU). During 

the snowmelt period, turbidity was generally less 

than 100 NTU and often less than 20 NTU (Stevens 

and others, 1997; Stevens, 2000). A boxplot of 

turbidity values (EWI samples only) at selected 

sites is shown in figure 11 and indicates that median 

values were generally less than 10 NTU. As with 

suspended-sediment concentrations, the largest 

values of turbidity occurred on the rising limb 

of the snowmelt hydrograph. Peak rainstorm 

turbidity ranged from a few NTU’s to more than 

1,000 NTU’s (Stevens and others, 1997; Stevens, 

2000).

The upstream/downstream pairs (CC1 to CC2, 

and CC13 to CC5) (fig. 12) indicate a pattern of downstream increases in turbidity similar to suspendedsediment concentration. During the periods of early 

snowmelt (May to early June) and rainstorms (represented here by the July 28, 1997, sample at CC1/CC2), 

turbidity increased in a downstream direction.

Peak Suspended Sediment and Turbidity During Storms

Road runoff occurs during summer rainstorms, 

which contributes to large suspended-sediment 

concentrations in receiving streams. Table 22 is a 

compilation of peak suspended-sediment and turbidity 

data collected during rain events in the summer 

months of WY’s 1995–97. Not all sites had equal 

sample coverage; pumping samplers were used, and 

sometimes only part of the rain event was adequately 

sampled. Ambient (nonstorm) conditions are represented by a sample unaffected by storm activity 

and collected within a few days of the event sample. 

Samples chosen to represent ambient conditions were 

limited by sample coverage and storm occurrence.

400

1

500

2

3

4

5

7

10

20

30

40

50

70

100

200

300

400

SUSPENDED-SEDIMENT DISCHARGE,

IN TONS PER SQUARE MILE

500 700 1,000 1,400

ANNUAL STREAMFLOW, IN ACRE-FEET PER SQUARE MILE

CC7

CC9

GC5

GC11

DC1

EXPLANATION

CC2

CC5

Figure 20. Relation of suspended-sediment yield per square mile to annual streamflow for selected sites, 

water years 1995–97.
54 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Analysis of the peak samples indicates that 

increases in suspended-sediment concentration and 

turbidity during a storm ranges from one to several 

orders of magnitude within a short period (table 22). 

At sites CC9, GC5, GC11, and DC1, measured 

peak concentrations did not exceed 400 mg/L. At 

sites CC2 and CC5, suspended-sediment concentrations exceeding 1,000 mg/L were sampled. The largest 

stream suspended-sediment concentration collected 

during the study period was 2,905 mg/L during a 

storm event (August 11, 1997) at site CC2. Data 

also indicate that suspended-sediment concentrations 

rapidly return to near prestorm concentrations 

after the storm (Stevens, 2000). Limited data for 

the percentage of silt/clay (finer than 0.062 mm) in 

the suspended sediment (table 22) indicate that during 

storms the material is fine grained, generally more 

than 90 percent silt/clay. This is probably due to the 

relatively small streamflow increases during rainstorm 

events that cannot transport large particles but can 

transport fine sediment detached by erosion resulting 

from the impact of rainfall on bare soil. If large particles are transported to the stream, they may settle on 

the streambed until being transported with high flows 

during the next snowmelt-runoff season.

Bed-Material Particle Size

Bed-material size distribution can indicate 

the condition of the stream substrate for biological 

integrity and show differences between sites that may 

indicate land-use effects. A study done in the Routt 

National Forest, in Colorado, which included an analysis of bed-material size and management activity, 

found a significant correlation between the number of 

particles less than 8 mm in diameter and the number of 

road crossings in granitic basins. Significant correlations between channel-condition indices with both the 

number of road crossings and the number of segments 

of road near the stream were also determined 

(Schnackenberg and MacDonald, 1998). 

In the Guanella Pass study, pebble-count 

methods (Wolman, 1954; Bevenger and King, 1995) 

were used to evaluate substrate-size conditions at 

selected sites. The data (table 23) indicate that at most 

sites, sand-sized or smaller material accounts for less 

than 10 percent of the substrate and the silt/clay fraction accounts for less than 1 percent. This relatively 

coarse bed material is in contrast to the fine-grained 

character of stormflow suspended sediment, and it 

might indicate that fine sediment transported in 

Table 18. Generalized basin characteristics for suspended-sediment comparison sites located outside the study area

Site

 (fig. 4) Site name

Drainage

area

(square miles)

Period of

record

(water years)

Generalized basin characteristics

Surface 

bedrock

geology

Land

use

Primary

source of 

peak

streamflow

1 Tarryall Creek near Jefferson 183 1978–81 crystalline/

sedimentary

rural,

agriculture

snowmelt

2 North Fork South Platte River at

South Platte

479 1950–82 crystalline rural,

developed

snowmelt

3 Clear Creek at Golden 400 1975–84 crystalline rural,

mining,

developed

snowmelt

4 Saint Vrain Creek at Lyons 212 1950–84 crystalline rural snowmelt

5 Big Thompson River at Estes Park 137 1948–84 crystalline rural,

developed

snowmelt

6 Cache La Poudre River at mouth of

canyon near Fort Collins

1,056 1950–84 crystalline rural snowmelt

7 Halfmoon Creek near Malta 23.6 1948–84 crystalline rural snowmelt

8 Middle Fork Piedra River near

Pagosa Springs

32.2 1970–75 crystalline rural snowmelt

9 Vallecito Creek near Bayfield 72.1 1963–84 crystalline rural snowmelt

10 Animas River near Howardsville 55.9 1950–82 crystalline rural, 

mining

snowmelt

11 Mineral Creek above Silverton 11.0 1969–75 crystalline rural, 

mining

snowmelt
CHARACTERIZATION OF WATER RESOURCES 55

stormflow does not form extensive deposits in these 

reaches and does not strongly influence bed-material 

composition. The boulder/cobble/gravel composition 

of area streams indicates that, in the areas sampled, 

fine materials, which can be poor habitat for algae, 

macroinvertebrates, and fish, were generally present 

in limited quantities, although fine sediments were 

observed in beaver ponds, debris dams, and streamchannel margins of most study-area streams.

Storm-Runoff Effects on Stream-Water Quality

Storm runoff can have an effect on stream-water 

chemistry and suspended-sediment transport in the 

study area. Water samples were collected at South 

Clear Creek above Naylor Creek (CC2) at base flow 

just before a thunderstorm (prestorm) and during 

stormflow (table 24). Water discharge increased 

from 0.54 to 0.71 ft3/s. Specific conductance increased 

from 136 to 191 μS/cm, and the pH decreased from 

8.0 to 7.6. Turbidity increased more than 600 times, 

indicating large concentrations of suspended particles. 

Most concentrations of major ions showed only 

minor changes, whereas the concentration of chloride 

increased 13 times, an indication that road applications 

of magnesium chloride (in 1993 and 1996 for this 

section of the road) could be affecting stormwater 

inflows to the stream. In contrast, the concentration of 

magnesium increased only slightly, perhaps a result of 

cation exchange with sodium and potassium, both of 

which also slightly increased.

The storm sample comparison at CC2 indicates 

that concentrations of nutrients, such as dissolved 

nitrite plus nitrate, total ammonia plus organic 

nitrogen, and total phosphorus, increased during the 

Table 19. Summary of annual streamflow and suspended-sediment yields for selected comparison streams in Colorado with 

crystalline bedrock geology and Guanella Pass streams

[acre-ft, acre-foot; mi2, square mile; tons/mi2, tons per square mile]

Site

 (figs. 1, 5)

Annual streamflow Suspended-sediment

yield per square mile

Suspended-sediment

yield per acre-foot

Maximum 

yield

(acre-ft/

mi2)

Minimum 

yield

(acre-ft/

mi2)

Mean

yield

(acre-ft/

mi2)

Maximum

yield

(tons/

mi2)

Minimum

yield 

(tons/

mi2)

Mean

yield 

(tons/

mi2)

Maximum

yield

(tons/

acre-ft)

Minimum

yield

(tons/

acre-ft)

Mean

yield

(tons/

acre-ft)

Comparison sites (fig. 4) (data from Elliott and DeFeyter, 1986)

1(a) 178 34 123 8.58 0.38 5.51 0.052 0.011 0.038

2 453 85 260 81.0 .58 22.0 .212 .007 .069

3 571 197 356 92.5 12.4 40.1 .162 .063 .103

4 750 158 406 21.6 2.28 9.24 .030 .014 .021

5 1,000 335 677 44.4 4.54 21.5 .045 .014 .030

6 611 88 227 48.7 2.05 10.8 .080 .022 .043

7 1,510 439 878 28.3 5.10 14.0 .020 .012 .016

8 1,540 458 983 59.3 7.02 31.9 .042 .015 .028

9 2,270 636 1,440 19.3 4.29 11.5 .009 .007 .008

10 1,940 594 1,240 356 3.35 79.1 .184 .006 .055

11 1,800 995 1,440 80.7 38.6 60.7 .045 .039 .042

Guanella Pass streams

CC2(a) 731 557 644 47.0 10.0 28.5 .064 .018 .041

CC5(a) 942 657 819 121 15.8 54.6 .129 .024 .062

CC7(a) 959 756 849 87.5 7.00 34.3 .091 .009 .037

CC9(a) 1,069 833 942 147 19.2 63.1 .137 .023 .062

GC5(a) 683 553 617 10.1 3.82 7.81 .014 .007 .012

GC11(a) 798 542 674 154 7.72 61.8 .193 .014 .081

DC1(a) 904 486 695 24.3 2.72 13.5 .027 .006 .016

a

Statistics are for periods less than 5 years and are presented for discussion only; not intended to represent long-term values.
56 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Table 20. Summary of hydrograph period contributions for water discharge and suspended sediment at selected sites, water years 1995[--, no data; periods are parts of the snowmelt hydrograph; flow-weighted-mean concentration is total suspended-sediment load for the period divided by total water dischmilligrams per liter; FWMC, flow-weighted-mean concentration of suspended sediment (in milligrams per liter)]

Characteristic

Water year 1995 Water year 1996 W

Rising

limb

Falling 

limb

Lowflow

Rainstorm Rising limb Falling limb Low flow Rain- storm Rising limb Fa

li

Site CC2

Percentage of water year -- -- -- -- 5 8 83 4 8 Percentage of discharge -- -- -- -- 21 43 49 2 14 Percentage of suspended-sediment load -- -- -- -- 63 25 8 4 18 FWMC -- -- -- -- 40 8 3 21 59 

Site CC5

Percentage of water year 17 12 68 3 6 27 67 -- 14 Percentage of discharge 20 48 26 6 9 60 31 -- 23 Percentage of suspended-sediment load 34 56 1.7 8.1 57 37 6 -- 49 FWMC 158 111 6 130 104 10 3 -- 49 

Site CC7

Percentage of water year 13 13 74 -- 24 15 61 -- 16 Percentage of discharge 20 47 33 -- 36 31 33 -- 27 Percentage of suspended-sediment load 59 40 1.3 -- 38 35 27 -- 30 FWMC 193 57 3 -- 7 8 6 -- 8 

Site CC9

Percentage of water year 11 11 76 2 18 13 69 -- 16 Percentage of discharge 20 53 21 5 31 46 23 -- 23 Percentage of suspended-sediment load 27 71 .6 .7 59 39 2 -- 51 FWMC 135 136 3 15 32 15 1 -- 41 

Site GC5

Percentage of water year 15 10 75 -- 21 13 64 2 15 Percentage of discharge 22 49 29 -- 34 46 18 2 26 Percentage of suspended-sediment load 35 55 9 -- 55 38 4.6 2.6 35 FWMC 16 12 3 -- 8 4 1 5 16 

Site GC11

Percentage of water year 15 11 72 2 11 13 72 4 14 Percentage of discharge 18 55 24 3 32 37 27 4 26 Percentage of suspended-sediment load 48 50 1.5 .4 58 22 17 3 35 FWMC 378 130 9 15 19 6 7 9 34 

Site DC1

Percentage of water year -- -- -- -- 21 16 60 3 13 Percentage of discharge -- -- -- -- 35 31 31 3 18 Percentage of suspended-sediment load -- -- -- -- 46 33 9 12 58 FWMC -- -- -- -- 5 4 1 14 50 
CHARACTERIZATION OF WATER RESOURCES 57

WATER DISCHARGE, IN CUBIC FEET PER SECOND

1 2 5 10 20 50 100 200 500 1,000

0.01

1,000

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

100

200

500

RISING-LIMB SUSPENDED-SEDIMENT DISCHARGE,

IN TONS PER DAY

CC5

CC2

CC9

REF

GC11

GC5

DC1 CC7

Figure 21. Relation of rising-limb suspended-sediment discharge and instantaneous water discharge for 

selected sites and a composite of undisturbed reference sites (REF), water years 1995–97.

Table 21. Regression equations and information for rising limb of snowmelt hydrograph at selected sites, water 

years 1995–97

[a, intercept coefficient; b, slope coefficient; Qs, suspended-sediment discharge; Qw, water discharge; LN, natural logarithm; REF, data from undisturbed 

land use reference sites excluding DC1; <, less than] 

Site

(fig. 1)

Number of 

samples

Natural logarithm form: LN(Qs) = b + a LN (Qw)

Exponentiated form:

Qs = e(b)Qw

(a)Cb

Coefficients

Standard 

error

Adjusted

coefficient of 

determination

(r2)

Bias 

correction 

factor

(Cb)

a p-value b p-value

CC2 13 1.5684 0.0043 –3.8586 0.0044 0.987 0.50 1.477 Qs = (0.0312)Qw

(1.568)

CC5 17 1.4368 <.0001 –2.9098 .0005 .864 .74 1.358 Qs = (0.0740)Qw

(1.437)

CC7 14 1.1126 .0096 –4.2162 .0083 .899 .39 1.371 Qs = (0.0203)Qw

(1.113)

CC9 17 2.4386 <.0001 –8.5872 <.0001 1.102 .73 1.765 Qs = (0.00034)Qw

(2.439)

GC5 24 1.4329 <.0001 –4.9052 <.0001 .767 .80 1.387 Qs = (0.0103)Qw

(1.433)

GC11a 16 1.8111 <.0001 –7.1144 .0001 1.074 .76 2.190 Qs = (0.0018)Qw

(1.811)

DC1 19 1.4623 <.0001 –5.5047 <.0001 .684 .77 1.217 Qs = (0.0050)Qw

(1.462)

REF 20 1.8045 <.0001 –5.7564 <.0001 .985 .75 1.527 Qs = (0.0049)Qw

(1.805)

a

Water years 1996–97 only.
58 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

storm (table 24). Nitrate in precipitation (table 4) 

or dry-fall accumulations are possible sources of the 

temporary increase in concentration. The increases 

in total ammonia plus organic nitrogen and total 

phosphorus are likely related to the increases in 

suspended particles from erosion associated with 

the storm.

Prestorm and storm-runoff analytical results 

for trace-element analyses at CC2 (table 24) that 

are greater than the reporting limit indicate that 

total recoverable and dissolved concentrations were 

larger for the selected trace elements during stormrunoff conditions. The trace-element concentrations 

in the storm runoff are about 1 to 2 orders of magnitude larger than those measured in the prestorm 

conditions. The increase in total recoverable concentrations at CC2 is mostly the result of increases in 

suspended particles from erosion associated with the 

storm. The dissolved trace-element increases could 

be the result of an influx of trace-element-bearing 

surface runoff or ground water, colloids not removed 

by filtration, or instream geochemical processes 

involving sediment.

During storm runoff, the water discharge at CC2 

(table 24) was only 31 percent higher than at prestorm 

conditions, whereas the sediment concentration 

increased more than 500 times. Sources of suspended 

sediment are bank and streambed erosion, surface 

runoff, and stormflow from the road. The small 

increase in streamflow seems insufficient to cause 

substantial increases in instream sediment-erosion 

processes. Although surface runoff is rare in forested 

basins (Luce, 1995), some sparsely vegetated areas 

exist in small areas near South Clear Creek that could 

contribute to suspended sediment if overland flow 

occurred. Storm runoff from the road is a likely source 

of the large increases in suspended-sediment concentration during the storm. During a different storm 

(July 28, 1997), field observation showed evidence 

of discharge to South Clear Creek upstream from 

CC2 originating at culverts and shoulder ditches on 

2400

6

20

8

10

12

14

16

18

DISCHARGE, IN CUBIC FEET PER SECOND

1200 2400 1200 2400 1200 2400 1200 2400 1200 2400

56789

May 1997

0

200

20

40

60

80

100

120

140

160

180

TURBIDITY, IN NEPHELOMETRIC TURBIDITY UNITS

DISCHARGE

TURBIDITY

Figure 22. Daily fluctuations in instantaneous turbidity and water discharge at site CC5, May 5–9, 1997.
C

HARACTERIZATIONOFWATERRESOURCES59

Table 22. Ambient and rainstorm peak-measured suspended-sediment and turbidity data at sites with pumping samplers, water years 19[--, no data; ft3/s, cubic feet per second; mg/L, milligrams per liter; mm, millimeters; NTU, nephelometric turbidity units; ambient samples represent nonstorm conditions indicated rainstorm peak concentration on the same line in the table; rainstorm peak-measured sample is the sample with the highest suspended-sediment concentration cosample coverage may not have been complete for any particular storm]

Site

(fig. 1)

Rain-event peak-measured (sediment) sample Representative ambient sam

Date Time

Water 

discharge 

(ft3/s)

Turbidity 

(NTU)

Suspendedsediment 

concentration

(mg/L)

Percentage 

finer than 0.062 mm

Date Time

Water 

discharge 

(ft3/s)

Turbidity 

(NTU)

c

CC9 08–01–95 1240 41 190 65 97 07–30–95 1900 49 1.9 CC9 08–23–95 1700 25 2.3 4 -- 08–23–95 2400 23 1.0 CC9 08–28–95 1800 25 18 29 -- 08–25–95 2100 23 .8 CC9 07–04–96 1700 64 .9 97 -- 07–03–96 2400 52 .4 CC9 09–06–96 1430 -- -- 27 -- 09–05–96 1430 -- -- GC5 07–09–96 2015 20 11 35 90 07–08–96 2400 18 1.5 GC5 07–18–96 1358 31 8.2 29 69 07–16–96 2200 13 1.8 GC5 08–23–96 1428 2.1 4.2 10 -- 08–22–96 2400 1.5 1.1 GC5 09–03–97 2115 8.6 7.6 64 -- 09–03–97 1746 3.8 2.3 GC11 08–22–95 1800 127 8.7 19 -- 08–20–95 1800 77 3.5 GC11 08–23–95 1600 105 9.0 20 -- 08–20–95 1800 77 3.5 GC11 08–25–95 2100 110 4.1 40 -- 08–25–95 2000 104 3.2 GC11 09–05–95 2400 54 11 27 -- 09–05–95 2300 51 4.3 GC11 09–09–95 1800 61 4.4 17 -- 09–07–95 1800 57 3.0 GC11 07–18–96 1245 112 27 44 85 07–17–96 2400 104 4.2 GC11 09–12–96 1844 26 83 100 98 09–12–96 1221 25 4.4 GC11 08–04–97 1630 109 98 143 -- 08–03–97 1518 86 2.6 GC11 08–09–97 1715 118 140 329 -- 08–11–97 1518 126 4.3 GC11 08–17–97 2045 83 18 39 -- 08–18–97 1645 83 4.1 GC11 08–28–97 1500 67 40 56 -- 08–29–97 1500 56 4.9 GC11 09–12–97 1859 -- -- 66 -- 09–12–97 1500 39 4.2 DC1 07–09–96 2200 29 4.4 27 -- 07–09–96 1200 18 .4 DC1 07–18–96 1835 31 9.6 53 51 07–17–96 2200 14 1.0 DC1 08–21–96 1643 7.9 20 350 99 08–21–96 1620 7.2 1.2 DC1 08–23–96 1453 11 51 76 97 08–23–96 1430 8.7 2.9 DC1 09–12–96 1255 8.4 91 142 -- 09–11–96 2200 5.4 .3 DC1 07–20–97 1345 58 2.5 14 -- 07–19–97 1609 60 .5 DC1 08–03–97 2045 9.7 12 42 -- 08–03–97 1845 9.7 4.0 DC1 08–04–97 1445 10 74 108 -- 08–04–97 0145 9.7 1.0 
60 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 DC1 08–09–97 1715 23 20 48 -- 08–09–97 1345 16 1.4 

DC1 08–31–97 1600 12 26 39 -- 08–30–97 1600 11 1.0 CC5 07–03–95 1400 -- -- 1,273 -- 07–02–95 1400 -- -- CC5 07–04–95 1703 -- -- 641 -- 07–05–95 1747 -- -- CC5 07–30–95 1900 30 450 543 84 07–27–95 1720 -- -- CC5 08–20–95 1700 23 29 38 -- 08–20–95 1500 20 1.2 CC5 08–22–95 1700 27 42 45 -- 08–21–95 1500 21 2.3 CC5 08–28–95 1900 20 -- 45 -- 08–28–95 1800 22 -- CC5 08–30–95 1700 18 11 80 -- 08–28–95 1700 21 3.8 CC5 07–28–97 1725 28 110 73 -- 07–28–97 1435 26 -- CC5 08–09–97 1630 26 61 42 -- 08–09–97 1400 26 2.3 CC5 08–10–97 1154 33 91 95 -- 08–09–97 1154 25 1.8 CC5 08–11–97 1520 27 79 73 -- 08–11–97 1154 26 3.2 CC5 08–26–97 1716 21 380 607 -- 08–26–97 1201 20 1.5 CC5 09–01–97 1615 24 1,500 1,739 -- 09–02–97 1845 16 1.3 CC2 07–18–97 1845 2.5 84 61 99 07–18–96 1800 2.4 1.9 CC2 08–03–96 1346 1.2 45 35 98 08–03–96 1416 1.1 6.1 CC2 08–21–96 1630 .71 2,500 1,510 100 08–21–96 1515 .54 4.0 CC2 08–27–96 1816 .71 870 450 100 08–27–96 1646 .58 -- CC2 09–06–96 1300 .82 1,500 773 100 09–06–96 1131 .52 4.6 CC2 09–14–96 2259 .63 420 180 100 09–14–96 2100 .58 2.7 CC2 09–15–96 0144 .73 99 52 -- 09–15–96 0014 .66 3.0 CC2 07–18–97 1800 2.5 42 37 -- 07–19–97 1800 1.7 4.5 CC2 07–28–97 1510 2.4 2,100 1,077 -- 07–30–97 1800 2.1 6.1 CC2 08–09–97 1345 2.1 1,400 1,180 100 08–08–97 1830 1.8 3.5 CC2 08–11–97 1445 2.7 2,900 2,905 -- 08–12–97 0300 2.4 8.1 CC2 09–03–97 1945 2.8 730 1,817 -- 08–31–97 1800 1.2 1.7 CC2 09–19–97 2315 1.1 360 180 -- 09–19–97 2131 .83 2.9 

Table 22. Ambient and rainstorm peak-measured suspended-sediment and turbidity data at sites with pumping samplers, water years 1

[--, no data; ft3/s, cubic feet per second; mg/L, milligrams per liter; mm, millimeters; NTU, nephelometric turbidity units; ambient samples represent nonstorm condition

indicated rainstorm peak concentration on the same line in the table; rainstorm peak-measured sample is the sample with the highest suspended-sediment concentration csample coverage may not have been complete for any particular storm]

Site

(fig. 1)

Rain-event peak-measured (sediment) sample Representative ambient sa

Date Time

Water 

discharge 

(ft3/s)

Turbidity 

(NTU)

Suspendedsediment 

concentration

(mg/L)

Percentage 

finer than 

0.062 mm

Date Time

Water 

discharge 

(ft3/s)

Turbidity 

(NTU)
CHARACTERIZATION OF WATER RESOURCES 61

the road. Discrete sources of sediment-laden discharge 

from the road were observed at several points along 

the stream during the short rainstorm. The velocity 

of the sediment plumes in the creek was slow because 

of low flow, resulting in alternating reaches of clear 

and turbid water. This non-steady-state condition 

might explain the large fluctuations in turbidity and 

suspended-sediment concentrations during some rain 

events at CC2 (Stevens, 2000) that are poorly correlated with streamflow.

A prestorm/storm-runoff sample set also was 

collected at Deer Creek near Bailey (DC1), which 

provides a storm-effects comparison at a site unaffected by roads or other land uses (table 24). The DC1 

results might not be comparable to the CC2 results 

because of the difference in location and precipitation 

totals (CC2 = 0.25 inch, DC1 = 0.89 inch) (Stevens, 

2000). Streamflow increased by 26 percent at DC1 

between the prestorm and storm samples, indicating 

a minor effect on flow. Specific conductance and pH 

values, major ion and dissolved nitrite plus nitrate 

concentrations remained fairly stable. Particle-related 

analytes such as total ammonia plus organic nitrogen, 

total phosphorus, and total recoverable trace elements 

increased as a result of increased suspended-sediment 

concentrations (15 times the prestorm concentration). 

Overall, the increases in constituent concentrations at 

DC1 during the selected stormflows were smaller than 

at CC2 and might be a result of the lack of roads and 

development in the DC1 basin.

Evidence of trace-element phase changes during 

storms was indicated by comparing filtered and unfiltered samples collected during two storms at Geneva 

Creek at Grant (GC11) to samples collected during 

base-flow conditions (table 25). In the first sample 

set in table 25 (collected September 12, 1996, at 1716 

and 1844 by pumping sampler), loads of suspended 

copper, iron, manganese, and zinc increased (increases 

ranging from 94 percent for copper to 10,000 percent 

for manganese) as a result of the storm runoff, 

whereas the dissolved-phase loads of copper and zinc 

decreased. Dissolved-phase loads of iron and manganese remained relatively unchanged. The decrease in 

percentage of some trace elements in the dissolved 

phase might be explained in part by a relative increase 

in particle-related phases (indicated by the increase in 

suspended sediment and turbidity) and by dilution 

from the increase in discharge. However, the decrease 

in dissolved-phase load between the base-flow condition and the storm condition for copper (–43 percent) 

and zinc (–60 percent) indicates that some of the 

dissolved phase might have been adsorbed to particles 

(sediment, organic material) transported during 

stormflow. 

Table 23. Bed-material particle-size data collected at stream sites, Guanella Pass area

[<, less than]

Site

(fig. 1) Date

Percentage of particles less than size, 

in millimeters

256 64 8 4 2 1 0.5 0.25 0.125 0.062

CC11 07–15–97 73 43 8 6 6 4 2 1 <1 <1

CC9 07–17–97 93 47 6 5 4 4 3 2 1 <1

CC5 07–17–97 98 81 15 12 10 9 8 7 4 1

CC2 07–30–97 89 52 12 11 8 6 5 3 1 <1

CC12 10–01–96 91 51 4 4 4 3 2 2 1 1

CC1 08–22–97 93 40 <1 <1 <1 <1 <1 <1 <1 <1

GC1 08–01–97 81 57 8 8 4 2 1 1 <1 <1

GC2 08–01–97 80 36 10 10 7 5 3 2 1 <1

GC5 08–22–97 73 45 8 7 6 6 5 3 2 1

GC7 08–22–97 96 61 5 5 4 4 3 2 1 <1

GC8 08–22–97 89 45 3 3 3 2 1 1 <1 <1

GC10 08–20–97 82 39 2 2 2 2 1 1 <1 <1

GC11 08–12–97 72 29 3 3 3 2 2 1 1 <1

DC1 07–25–97 94 55 10 10 9 6 4 2 1 <1
62 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

The second storm at GC11 (table 25) did 

not have a base-flow comparison sample immediately 

preceding the storm sample, but one sample collected 

2 weeks before probably represents a suitable comparison. As with the 1996 sample, the storm sample 

collected on August 9, 1997 (pumping sampler), 

exhibited an increase in suspended sediment 

(2,600 percent) and turbidity (2,600 percent) relative 

to samples collected at the base-flow condition of 

July 27, 1997 (pumping sampler). Similar to the 

1996 sample, the decrease in dissolved-phase loads 

of zinc transported during stormflow were greater 

than 94 percent. In contrast to the previous storm 

sample discussion, the dissolved copper load 

remained substantially unchanged (+5 percent), and 

dissolved manganese loads decreased substantially 

(–74 percent). The decreases in dissolved-phase loads 

of some trace elements indicate that sediment-laden 

stormflow may actually improve water quality from 

the standpoint of dissolved trace-element concentrations, which are a focus of State of Colorado waterquality standards (Colorado Department of Public 

Health and Environment, Water Quality Control 

Division, 1996).

Table 24. Selected water-quality properties or constituents of water samples collected during prestorm (base flow) and 

storm runoff in South Clear Creek above Naylor Creek (CC2) on August 21, 1996, and Deer Creek near Bailey (DC1) on 

August 23, 1996

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; mg/L, milligrams per liter; 

μg/L, micrograms per liter; <, less than; mm, millimeters]

Property or constituent

CC2 DC1

Prestorm

(1515 hours)

Storm runoff

(1630 hours)

Prestorm

(1430 hours)

Storm runoff

(1453 hours)

Discharge, ft3/s 0.54 0.71 8.7 11.0

pH, standard units 8.0 7.6 7.8 7.6

Specific conductance, μS/cm 136 191 39 43

Turbidity, NTU 4.0 2,500 2.9 51

Calcium, dissolved, mg/L as Ca 14 14 4.0 4.0

Magnesium, dissolved, mg/L as Mg 6.9 9.8 1.1 1.0

Sodium, dissolved, mg/L as Na 2.0 3.6 1.8 1.7

Potassium, dissolved, mg/L as K .8 1.7 .6 .7

Alkalinity, total lab, mg/L as CaCO3 60 44 17 17

Sulfate, mg/L as SO4 6.6 7.1 2.7 2.5

Chloride, dissolved, mg/L as Cl 1.8 24 .2 .2

Dissolved solids, sum of constituents, mg/L 75 92 31 30

Nitrogen, nitrite plus nitrate, dissolved, mg/L as N .016 .20 .063 .056

Nitrogen, ammonia plus organic, total, mg/L as N .3 1.2 <.2 .5

Phosphorus, total, mg/L as P .012 .23 .009 .077

Copper, total recoverable, μg/L as Cu <1 39 <1 4

Copper, dissolved, μg/L as Cu <1 1 <1 4

Iron, total recoverable, μg/L as Fe 390 66,000 180 3,100

Iron, dissolved, μg/L as Fe 240 59 12 34

Lead, total recoverable, μg/L as Pb <1 48 <1 4

Manganese, total recoverable (μg/L as Mn) <10 1,700 <10 100

Manganese, dissolved (μg/L as Mn) <1 82 1 2

Zinc, total recoverable (μg/L as Zn) <10 180 <10 <10

Zinc, dissolved (μg/L as Zn) 5 17 <3 <3

Sediment, suspended (mg/L) 3 1,510 5 76

Sediment, percentage finer than 0.062 mm 93 100 76 97
CHARACTERIZATION OF WATER RESOURCES 63

Table 25. Comparison of selected water-quality constituents and trace-element phase changes at Geneva Creek (GC11) 

between two storm-event samples (09–12–96 and 08–09–97) and corresponding base-flow reference samples

[NA, not applicable; --, no data; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per centimeter at 25 degrees Celsius; 

mg/L, milligrams per liter; μg/L, micrograms per liter; >, greater than; <, less than; ≥, greater than or equal to]

Property or constituent

Base-flow reference Stormflow Percentage change in 

discharge-weighted 

value or load

between base flow

and stormflow

Value or

concentration

Percentage in 

suspended1 or 

dissolved2 phase

Value or 

concentration

Percentage in 

suspended1 or 

dissolved2 phase

Date, time 09–12–96 at 1716 09–12–96 at 1844

Discharge, ft3/s 23 N/A 26 N/A 313

Turbidity, NTU 4.8 N/A 83 N/A 3

1,900

Specific conductance, μS/cm 87 100 86 100 312

pH, standard units 7.2 N/A 7.3 N/A N/A

Chloride, mg/L .3 100 .3 100 413

Sulfate, mg/L 29 100 28 100 49

Copper, suspended1 as Cu, μg/L 7 78 12 92 494

Copper, dissolved as Cu, μg/L 2 22 1 8 4–43

Iron, suspended1 as Fe, μg/L >427 >99 5,096 >99 <1,200

Iron, dissolved as Fe, μg/L <3 <1 4 <1 --

Manganese, suspended1 as Mn, μg/L <1 0 90 28 4>10,000

Manganese, dissolved as Mn, μg/L 250 100 230 72 44

Zinc, suspended1 as Zn, μg/L 5 6 70 70 41,500

Zinc, dissolved as Zn, μg/L 85 94 30 30 4–60

Suspended sediment, mg/L 10 100 100 100 4

1,000

Date, time 07–27–97 at 2201 08–09–97 at 1715

Discharge, ft3/s 112 N/A 118 N/A 5

Turbidity, NTU 5.4 N/A 140 N/A 2,600

Specific conductance, μS/cm 59 100 57 100 2

pH, standard units 7.1 N/A 7.3 N/A N/A

Chloride, mg/L .2 100 .2 100 5

Sulfate, mg/L 14 100 14 100 5

Copper, suspended1

 as Cu, μg/L 5 71 10 83 110

Copper, dissolved as Cu, μg/L 2 29 2 17 5

Iron, suspended1 as Fe, μg/L 765 91 7,260 98 900

Iron, dissolved as Fe, μg/L 75 9 140 2 97

Manganese, suspended1 as Mn, μg/L 30 20 270 90 850

Manganese, dissolved as Mn, μg/L 120 80 30 10 –74

Zinc, suspended1 as Zn, μg/L 3 5 >67 >96 >2,200

Zinc, dissolved as Zn, μg/L 57 95 <3 <4 ≥94

Suspended sediment, mg/L 13 100 329 100 2,600

1

Percentage suspended fraction was computed as the difference between the dissolved and total recoverable concentrations divided by the total 

recoverable concentration; suspended sediment was assumed to be 100 percent suspended. 2

Percentage dissolved fraction computed as the dissolved concentration divided by the total recoverable concentration; specific conductance, 

chloride, and sulfate were assumed to be 100 percent dissolved. 3

Percentage change in discharge-weighted value by comparison of base-flow and stormflow estimates.

4

Percentage change in constituent load by comparison of base-flow and stormflow estimates.
64 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Lakes and Reservoirs

Lakes and reservoirs in the Guanella Pass area 

are important resources for recreation, aquatic habitat, 

hydroelectric-power generation, irrigation storage, and 

drinking water. Lakes and reservoirs within the watersheds affected by the Guanella Pass road are receiving 

waters for road runoff. Selected lakes and reservoirs 

near the Guanella Pass road were sampled to document water-quality conditions. Green Lake, Clear 

Lake, Lower Cabin Creek Reservoir, and Duck 

Lake were sampled once in August 1995 as part of a 

reconnaissance-level assessment (Stevens, 1999). In 

water years 1996–97, sampling focused on Clear Lake 

and Duck Lake, prominent public and private water 

bodies near the Guanella Pass road. In 1997, bottom 

sediment was collected at Georgetown Reservoir and 

Lower Square Top Lake for comparison to the previously sampled lakes and reservoirs (Stevens and 

others, 1997; Stevens, 2000). 

Duck Lake (L1, fig. 2) is a privately owned lake 

at 11,123 ft of altitude near the headwaters of Duck 

Creek. Duck Lake is more than 100 feet deep in 

places, and its natural capacity has been modified with 

a small dam that seasonally releases irrigation water 

into Duck Creek for downstream use. 

Lower Cabin Creek Reservoir (L2, fig. 2) is a 

shallow reservoir on South Clear Creek at approximately 10,000 ft of altitude, operated by the Public 

Service Company of Colorado for the purpose of peak 

power generation. The water from Lower Cabin Creek 

Reservoir is pumped to Upper Cabin Creek Reservoir 

and released to generate power at peak demand 

through a powerplant at the edge of Lower Cabin 

Creek Reservoir. Normal streamflow patterns are 

maintained by releases from Lower Cabin Creek 

Reservoir and Clear Lake (also operated by the 

Public Service Company of Colorado). 

Clear Lake (L3, fig. 2), which is more than 

100 feet deep and whose natural capacity has been 

modified with a small dam, is located immediately 

downstream from Lower Cabin Creek Reservoir on 

South Clear Creek at 9,873 ft of altitude. Recreational 

facilities at the lake promote heavy visitor use. Fluctuations in water level are generally minimal. During 

water years 1996 and 1997, however, repairs and 

renovations to the dam required lowering water levels 

and pumping water over the dam while construction 

progressed. 

Green Lake (L4, fig. 2), located west of Clear 

Lake, is owned by the Public Service Company of 

Colorado and is used for private recreation. The 

lake is small but deep (more than 50 ft), and its natural 

capacity is increased by a small dam, with storage 

augmented by flows piped from Leavenworth Creek 

on a seasonal basis. Aeration is used during winter 

to maintain adequate dissolved oxygen for fish 

populations. 

Lower Square Top Lake (L5, fig. 2) is a natural 

lake lying at 12,046 ft of altitude at the headwaters of 

Duck Creek. The lake area gets heavy visitor traffic by 

hikers and fishermen but has no other upstream landuse factors. 

Georgetown Reservoir (L6, fig. 2) is a small 

diversion structure that allows water to be diverted to a 

powerplant in Georgetown and the Georgetown watertreatment plant. The capacity of the detention structure 

is small and is severely limited by sediment accumulation. Water in Georgetown Reservoir, having a short 

residence time and a shallow depth, is likely to be 

similar in character to a mixture of Leavenworth and 

South Clear Creeks.

Vertical Profiles and Onsite Measurements

Lake and reservoir profiles of water temperature, specific conductance, pH, and dissolved oxygen 

were used to evaluate limnological characteristics. 

Profile measurements were collected once at Lower 

Cabin Creek Reservoir and Green Lake in water 

year 1995 and many times during the open-water 

season at Duck and Clear Lakes during water years 

1996–97 (Stevens and others, 1997; Stevens, 2000). 

Seasonal air temperatures and lake stratification 

patterns indicate that the deep lakes (Duck Lake, 

Clear Lake, and Green Lake) are probably dimictic—

temperature stratification forms in summer and winter, 

and the lake contents mix during overturn in the spring 

and fall (Cole, 1994). In these lakes, water temperature, specific conductance, pH, and dissolved oxygen 

varied with depth during the summer season. Lower 

Cabin Creek Reservoir probably does not stratify 

every year (no stratification was observed in 

August 1995) because of shallow depth and pumping 

of reservoir contents for hydroelectric-power generation. Seasonal profile patterns for the stratified lakes 

in the study area are exemplified by selected Duck 

Lake and Clear Lake profiles for WY 1997 (figs. 23 

and 24).
CHARACTERIZATION OF WATER RESOURCES 65

0

0

10/23/96

6/12/97

7/8/97

9/5/97

0 120 10 20 30 40 50 60 70 80 90 100 110

SPECIFIC CONDUCTANCE, IN MICROSIEMENS

PER CENTIMETER AT 25 DEGREES CELSIUS 

0

110

10

20

30

40

50

60

70

80

90

100

10/23/96

6/12/97

7/8/97

9/5/97

10/23/96

6/17/97

7/2/97

9/5/97

110

30

40

50

60

70

80

90

100

DEPTH BELOW SURFACE, IN FEET

0 100 10 20 30 40 50 60 70 80 90

10

20 Duck Lake Clear Lake

0 16 2 4 6 8 10 12 14

WATER TEMPERATURE, IN DEGREES CELSIUS

110

10

20

30

40

50

60

70

80

90

100

Clear Lake

0 16 2 4 6 8 10 12 14

0

Duck Lake

110

10

20

30

40

50

60

70

80

90

100

10/23/96

6/17/97

7/2/97

9/5/97

Figure 23. Profile of water-temperature and specific-conductance variation with depth in Duck Lake and 

Clear Lake on selected sampling dates during water year 1997.
66 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

0 14 1 2 3 4 5 6 7 8 9 10 11 12 13 0 14 1 2 3 4 5 6 7 8 9 10 11 12 13

DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER

110

10

20

30

40

50

60

70

80

90

100

DEPTH BELOW SURFACE, IN FEET

0 0

110

10

20

30

40

50

60

70

80

90

100

Duck Lake Clear Lake

7/2/97

9/4/97

10/23/96

6/17/97

7/8/97

9/5/97

10/23/96

6/12/97

pH, IN STANDARD UNITS

6/17/97

7/2/97

9/4/97

10/23/96

6/12/97

7/8/97

9/5/97

10/23/96

Clear Lake

6 10 7 89

0

110

10

20

30

40

50

60

70

80

90

100

6 10 7 89

0

110

10

20

30

40

50

60

70

80

90

100

Duck Lake

Figure 24. Profile of pH and dissolved-oxygen variation with depth in Duck Lake and Clear Lake on 

selected sampling dates during water year 1997.
CHARACTERIZATION OF WATER RESOURCES 67

In both Duck and Clear Lakes, minor thermal 

stratification was evident in June 1997, intensifying 

through the summer. The thermocline was located at 

about 20 to 30 ft below the surface in Duck Lake and 

30 to 40 ft below the surface in Clear Lake (fig. 23). 

The surface temperatures throughout water year 1997 

ranged from about 4° to 14°C, whereas the bottom 

temperatures were a fairly constant 4°C year round. 

Specific-conductance profiles (fig. 23) generally 

indicate increasing conductivity with depth, whereas 

pH profiles (fig. 24) generally indicate neutral but 

decreasing pH, with depth. Water temperature, 

specific conductance, and pH are generally uniform 

with depth in October 1996.

Dissolved-oxygen profiles at Duck and Clear 

Lakes (water year 1997) (fig. 24) generally indicate 

decreases with depth except October 1996 when 

mixing of lake or reservoir contents reoxygenated 

the entire water column of both lakes. Bottom-water 

hypoxia (low oxygen) was more pronounced in Duck 

Lake than in Clear Lake; minimum dissolved-oxygen 

concentrations in Duck Lake generally were less than 

2 mg/L except for October 1996. Small concentrations 

of dissolved oxygen can restrict the vertical distribution of organisms that require oxygen. Clear Lake 

did not have dissolved-oxygen concentrations below 

3.5 mg/L in water year 1997.

Transparency and Chlorophyll

Water transparency was assessed with secchidisc measurements at the time of water-quality 

sampling. Transparencies at all sampling dates ranged 

from 9.0 ft (Clear Lake, 10–23–96) to 29.4 ft (Green 

Lake, 08–15–95). Most transparencies were in the 8- 

to 15-ft range in water years 1996–97 (Stevens and 

others, 1997; Stevens, 2000).

Chlorophyll-a can be used as an indicator 

of algal productivity. Chlorophyll-a concentrations 

were analyzed from photic-zone composite samples 

from Duck and Clear Lakes in water years 1996–97 

(Stevens and others, 1997; Stevens, 2000). The photic 

zone was estimated at the time of sampling to be twice 

the secchi-disc depth. Chlorophyll-a concentrations 

in Duck Lake in water years 1996–97 ranged from 

0.5 mg/L (09–4–96, data from Stevens [2000]) to 

3.2 mg/L (08–12–97). Chlorophyll-a concentrations 

in Clear Lake in water years 1996–97 ranged from 

0.2 mg/L (09–05–97, 06–12–97) to 0.5 mg/L 

(07–23–97) (table 27).

Water-Column Major Ions, Nutrients, and 

Trace Elements

Chemical characteristics of lake and reservoir 

water were generally similar to those of the streams 

that flow into them. In the case of Green Lake, chemical characteristics are influenced by the diversion 

water from Leavenworth Creek that maintains the lake 

level. Some lake and reservoir bottom-water samples 

indicate that reducing conditions develop as a result of 

seasonal oxygen deficits (Stevens and others, 1997; 

Stevens, 2000). 

Specific conductance ranged from 22 μS/cm at 

the surface of Duck Lake (07–02–97) to 212 μS/cm 

near the bottom of Green Lake (08–15–95). As in 

most area stream waters, pH was neutral and majorion chemistry was predominantly calcium and bicarbonate at all lakes and reservoirs sampled. Chloride 

concentrations were small, generally less than 1 mg/L 

(Stevens and others, 1997; Stevens, 2000). 

Nutrient concentrations were small; nitrogen 

species consisted mainly of dissolved ammonia and 

dissolved nitrite plus nitrate. Ammonia can be released 

from bottom sediment during periods of hypoxia. The 

largest concentration of ammonia (0.722 mg/L as N) 

was determined for near-bottom water of Duck Lake 

in the June 17, 1997, sample. Most bottom-water 

samples had concentrations of dissolved ammonia less 

than 0.2 mg/L as N. Surface or photic-zone composite 

samples had dissolved ammonia concentrations less 

than 0.01 mg/L as N. Duck Lake tended to have 

dissolved ammonia concentrations that were larger 

than those from Clear Lake (Stevens and others, 

1997; Stevens, 2000), a consequence of more extreme 

reducing conditions caused by more intense hypoxia.

Nitrite plus nitrate, along with ammonia, are 

considered to be the most bioavailable forms of 

nitrogen in water (Woods, 1992). Nitrite plus nitrate 

was present in the inflows to lakes but also may be 

formed from the oxidation of ammonia. Nitrite plus 

nitrate concentrations in surface, or photic-zone 

composite, samples ranged from less than 0.005 mg/L 

as N (Duck Lake, 09–04–97) to 0.11 mg/L as N (Clear 

Lake, 08–16–95, and Lower Cabin Creek Reservoir, 

08–15–95). Nitrite plus nitrate concentrations in nearbottom samples ranged from 0.013 mg/L as N (Duck 

Lake, 06–17–97) to 0.21 mg/L as N (Duck Lake, 

09–04–96). Generally, larger surface-water and nearbottom-water concentrations of nitrite plus nitrate 

occurred in Clear Lake than in Duck Lake in water 
68 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

year 1997, probably because of inflows of surface 

water containing large concentrations (Stevens and 

others, 1997; Stevens, 2000).

Phosphorus is the other major nutrient of 

concern in lakes and reservoirs and is of particular 

interest because it usually is the limiting nutrient for 

algal growth. Total phosphorus concentrations ranged 

from 0.001 to 0.18 mg/L as P in surface and photiczone composite samples, and 0.001 to 0.094 mg/L as P 

in near-bottom samples. The large concentration at the 

surface was measured when shore erosion increased 

suspended particles, a result of the drawn-down condition of Clear Lake at the time of sampling. Dissolved 

orthophosphorus, the most bioavailable form of phosphorus (Woods, 1992), ranged from less than 0.001 to 

0.002 mg/L as P in surface or photic-zone composite 

samples, and less than 0.001 to 0.038 mg/L as P in 

near-bottom water samples (Stevens and others, 1997; 

Stevens, 2000). The larger concentrations of phosphorus in near-bottom water samples of Duck and 

Clear Lakes than in the photic zone may indicate 

that phosphorus is being released from bottom sediment, especially in Duck Lake. Because the nearbottom water-sample concentrations are so large, 

the difference between near-surface and near-bottom 

samples does not seem to be a result of algal consumption of phosphorus near the surface.

Nitrogen (N) to phosphorus (P) mass ratios have 

been used to characterize the limiting nutrient for algal 

growth present in water (Britton and Gaggiani, 1987; 

Woods, 1992). If a nutrient is limiting, the hypothesis 

is that the addition of that nutrient would then cause an 

increase in algal production (in the absence of other 

limiting factors) (Britton and Gaggiani, 1987; Woods, 

1992). A mass ratio of about 7N:1P (dissolved inorganic nitrogen to dissolved orthophosphorus) is the 

theoretical boundary between N and P limitation 

(Redfield, 1958). In practice, N:P ratios below 5 are 

thought to represent nitrogen-limiting situations, 

whereas N:P ratios above 10 represent phosphoruslimiting conditions. Nitrogen to phosphorus ratios 

between 5 and 10 could indicate nitrogen or phosphorus limitation (Britton and Gaggiani, 1987; 

Woods, 1992). 

Nitrogen to phosphorus ratios for Duck and 

Clear Lakes for WY 1997 are listed in table 26. Some 

nutrient concentrations were less than the MRL, but in 

most cases this fact did not prevent assessment of the 

Table 26. Mass ratio computations of nitrogen to phosphorus and limiting nutrients in Duck Lake (L1) and Clear Lake (L3) 

surface or photic-zone composite samples, water year 1997

[All concentrations dissolved in mg/L; P, phosphorus; all phosphorus concentrations are orthophosphorus as P; N, nitrogen; DIN, dissolved inorganic 

nitrogen, the sum of NO2 + NO3 and ammonia; DIN:P, dissolved inorganic nitrogen to orthophosphorus ratio; limiting nutrient, algal growth limited by 

concentration of nitrogen or phosphorus; (NO2 + NO3 ):P, ratio of nitrate plus nitrite to orthophosphorus, used when ammonia is a censored value; 

DIN:P ratio is preferred, but (NO2 + NO3 ):P ratio along with the reporting limit of ammonia is used to estimate a range, which often determines a limiting 

nutrient; ?, inconclusive; --, not computed; <, less than; >, greater than]

Site Date Phosphorus, 

ortho as P

Nitrogen, 

NO2 + NO3

as N

Nitrogen, 

ammonia 

as N

DIN

Percentage 

of ammonia

in DIN

DIN:P

Limiting

nutrient by

DIN:P

(NO2 + 

NO3):P

Limiting 

nutrient by 

(NO2 + 

NO3):P

L1 10–23–96 <0.001 0.014 <0.002 <0.016 <13 ? ? >14 P

L1 06–17–97 <.001 .019 <.002 <.021 <10 ? ? >19 P

L1 07–02–97 .001 .005 .002 .007 29 7 N or P ? ?

L1 07–14–97 <.001 .006 <.002 <.008 <25 ? ? >6 N or P, or P

L1 07–24–97 <.001 .012 .007 .019 37 >19 P ? ?

L1 08–12–97 .001 .007 <.002 <.009 <22 ? ? 7 N or P

L1 09–04–97 .002 <.005 .002 <.007 29 <3.5 N ? ?

L3 10–23–96 <.001 .062 <.002 <.064 <3 ? ? >62 P

L3 06–12–97 <.001 .061 <.002 <.063 <3 ? ? >61 P

L3 07–08–97 <.001 .080 <.002 <.082 <2 ? ? >80 P

L3 07–23–97 <.001 .083 .002 .085 2 >85 P -- --

L3 08–08–97 .001 .075 <.002 <.077 <3 ? ? 75 P

L3 09–05–97 .001 .073 <.002 <.075 <3 ? ? 73 P
CHARACTERIZATION OF WATER RESOURCES 69

ranges in ratios. If ammonia concentration was less 

than the reporting limit, generally the proportion of 

ammonia was too small to affect the N:P ratio. If the 

orthophosphorus or nitrite plus nitrate concentration 

was less than the MRL, an evaluation of the possible 

concentrations would usually allow an estimate 

of a range for the N:P ratio, which determined the 

limiting nutrient. For Duck Lake, 43 percent of the 

samples indicated phosphorus limitation (table 26); 

for 43 percent of the samples, limitation status could 

not be determined because of concentrations below 

the MRL, and 14 percent of the samples indicated 

nitrogen limitation. For Clear Lake, all samples 

during WY 1997 indicated phosphorus limitation. 

Concentrations of dissolved and total recoverable trace elements in all lakes were small, with only 

aluminum, iron, manganese, and zinc consistently 

higher than the laboratory MRL (Stevens and others, 

1997; Stevens, 2000). Copper occasionally exceeded 

the laboratory MRL. Iron and manganese concentrations were almost always higher in the near-bottom 

sample than in the surface or photic-zone composite 

sample, except after fall overturn when surface and 

bottom concentrations were nearly equal for total 

recoverable and dissolved concentrations. Nearbottom water-sample concentrations of total recoverable iron ranged from less than 10 μg/L (Green Lake, 

08–15–95) to 2,500 μg/L (Duck Lake, 08–16–95). 

Near-bottom water-sample concentrations of total 

recoverable manganese ranged from less than 10 mg/L 

(several samples) to 540 mg/L (Duck Lake, 08–16–95) 

(Stevens and others, 1997; Stevens, 2000). Iron and 

manganese become more soluble and can be released 

from bottom sediments under reducing conditions 

caused by hypoxia. Lower Cabin Creek Reservoir may 

release these hypoxic waters periodically. Orange-red, 

flocculated material accumulated on the streambed 

downstream from the reservoir. The material probably 

consists of iron and manganese hydroxides precipitated as the water from the reservoir was reoxygenated 

in the stream (see streambed-sediment chemical data 

for site CC6 just downstream from Lower Cabin 

Creek reservoir [Stevens, 2000]).

Nutrient Limitation and Trophic Status

The relative fertility of a lake or reservoir can be 

evaluated by assessing the trophic status. Oligotrophic 

(nutrient-poor) lakes have characteristics such as high 

transparency, small organic-matter content, relatively 

large dissolved-oxygen concentrations, small nutrient 

concentrations, and small algal biomass. Eutrophic 

(nutrient-rich) lakes have the opposite characteristics 

(Woods, 1992). On the basis of data collected in water 

year 1997, Duck Lake and Clear Lake were assessed 

using the method developed by Carlson (1977). 

Trophic-state index (TSI) values were calculated from the following equations:

(6)

(7)

(8)

where

SD = secchi-disc depth, in meters;

TP = total phosphorus concentration, in micrograms per liter;

CHLA = chlorophyll-a concentration, in micrograms 

per liter; and

ln = the natural logarithm of the indicated 

variable.

Trophic-state index values were calculated 

for each sampling date and for the mean values in 

water year 1997 (table 27). The Carlson (1977) 

index assumes phosphorus limitation. The boundary 

between oligotrophic (nutrient-poor) and mesotrophic 

(moderate nutrients) is a TSI value of 41. The 

boundary between mesotrophic and eutrophic 

(nutrient-rich) is a TSI value of 51. Both Duck and 

Clear Lakes generally remained in the oligotrophic 

category in water year 1997 for the three trophic 

indices. Annual mean TSI values were oligotrophic 

for both lakes.

Bottom-Sediment Chemistry

Bottom sediments in lakes and reservoirs can 

accumulate nutrients and trace elements that can be 

toxic to sediment-dwelling organisms and can be 

remobilized under certain geochemical conditions. 

Bottom sediments also can integrate years of chemical 

conditions and provide an indication of watershed 

chemical influences that are sometimes difficult to 

detect in water-column samples. A surficial sample 

TSI SD ( ) = 60 14.41 SD – ( ) ln

TSI TP ( ) = 14.42 TP ( ) ln + 4.15

TSI CHLA ( ) = 8.23 CHLA ( ) ln + 33.3
70 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

(less than 10 cm of depth) of bottom sediment 

was collected by surface dredge (petite ponar type) 

once in four water bodies (L2, L4, L5, and L6) (fig. 2). 

At Duck Lake (L1) and Clear Lake (L3), bottomsediment samples were collected each water year, 

1995–97. Trace-element analyses were completed on 

all samples (less than 63-μm fraction). Nutrient analyses were completed on samples from sites L1, L3, 

and L4. Selected organic analyses (including herbicides and pesticides) were completed on samples 

from sites L1, L2, and L3 (Stevens and others, 

1997; Stevens, 2000).

Selected trace-element, nutrient, and traceorganic concentrations in bottom sediment are listed 

in table 28. Among the sites sampled for nutrient 

content, Duck Lake (L4) had the largest concentrations of ammonia, ammonia plus organic nitrogen, 

and phosphorus. Because little of the ammonia plus 

organic nitrogen concentration is ammonia, organic 

nitrogen is the predominant form of nitrogen in bottom 

sediments at all of the lakes and reservoirs. 

Among the lakes and reservoirs sampled for 

bottom-sediment trace elements (all sites), Green 

Lake (L4) and Georgetown Reservoir (L6) generally 

had the largest concentrations of zinc and lead 

(table 28). The large concentrations of these trace 

elements in sediment at these sites are related to 

sources of trace elements in the Leavenworth 

Creek Basin, which is a water source to both water 

bodies. The relatively large concentrations of trace 

elements in the bottom of Georgetown Reservoir 

(L6) could be a concern if the reservoir is dredged 

or decommissioned.

Among the sites sampled for selected traceorganic constituents, Duck Lake (L1) and Lower 

Cabin Creek Reservoir (L2) bottom sediment 

contained small concentrations of PCB’s (polychlorinated biphenyls). Dichlorodiphenyldichloroethylene 

(DDE), also a decay product of DDT, was detected in 

Lower Cabin Creek Reservoir bottom sediment. Also, 

1,1-dichloro-2,2-bis p-chlorophenylethane (DDD), a 

decay product of DDT, was detected in Duck Lake 

bottom sediment (table 28). The small concentrations 

of DDD and DDE in bottom sediment could be the 

result of bulk atmospheric deposition resulting from 

the past widespread use of DDT, and their presence 

does not necessarily indicate a source in the basin. 

These organic chemicals are environmentally persistent and readily partition into a sorbed phase such as 

bottom sediment.

Table 27. Trophic-state index computations for Duck Lake (L1) and Clear Lake (L3), water year 1997

[TSI, trophic state index (Carlson, 1977); SD, secchi-disc depth; TP, total phosphorus as P; CHLA, chlorophyll-a; --, no data; WY, water year; m, meter; 

μg/L, micrograms per liter; all data are for surface or photic-zone composites]

Site

(fig. 2) Date SD(m)

TSI

(SD)

TP

(μg/L)

TSI

(TP)

CHLA

(μg/L)

TSI

(CHLA)

L1 10–23–96 4.0 40 6 30 0.8 28

L1 06–17–97 3.2 43 8 34 1.5 35

L1 07–02–97 -- -- 6 30 1.9 37

L1 07–14–97 4.6 38 4 24 .8 28

L1 07–24–97 4.6 38 4 24 1.3 33

L1 08–12–97 4.2 39 14 42 3.2 42

L1 09–04–97 3.6 41 7 32 1.8 36

L1 Mean for WY 1997 4.0 40 7 31 1.6 34

L3 10–23–97 2.7 45 3 20 .3 19

L3 06–12–97 -- -- 6 30 .2 15

L3 07–08–97 3.4 42 5 27 .4 22

L3 07–23–97 4.1 40 1 4 .5 24

L3 08–08–97 4.5 38 3 20 .4 22

L3 09–05–97 6.0 34 2 14 .2 15

L3 Mean for WY 1997 4.2 40 3 19 .3 20
CHARACTERIZATION OF WATER RESOURCES 71

Ground Water

Ground-water samples were collected at springs 

and USDA Forest Service campground handpumps 

in the Guanella Pass study area during a reconnaissance study of ground-water quality (fig. 3) to assess 

conditions in WY’s 1995–97. Ground-water analytical 

data are presented in Stevens and others (1997) 

and Stevens (2000). Statistical summaries of groundwater chemical data are presented in Appendix 

table 50. 

Ground-water sources in nearby crystalline 

bedrock areas are generally from fractures in bedrock or alluvium, soil, or glacial material in valleys 

(Hofstra and Hall, 1975). Because snow is the 

primary form of precipitation in the area, recharge 

in the bedrock areas is probably from infiltration 

of melted snow. Alluvium in the valleys is probably 

shallow and hydraulically connected to the stream. 

Available well-construction information (Stevens, 

2000) indicates that some wells are relatively shallow 

(30 to 265 ft depth) and are screened in bedrock 

(screened depth ranging from 15 to 160 ft below 

surface).

Onsite Measurements and Major Ions

The specific conductance of ground-water 

samples ranged from 24 to 584 μS/cm, with a median 

value of 104 μS/cm (Appendix table 50), which is 

generally greater than the range in surface-water 

medians, 31 to 87 μS/cm (table 7). The pH ranged 

from 6.5 to 8.3, a generally neutral range. Turbidity 

was low, ranging from 0.2 to 20 NTU. The predominant cation in all of the ground-water samples was 

calcium, and the predominant anion was bicarbonate 

(fig. 25). The median concentration of chloride was 

0.6 mg/L, and concentrations ranged from less than 

0.1 to 18 mg/L (table 50). Natural background concentrations of chloride are generally low in the mountainous, crystalline bedrock setting (Hofstra and Hall, 

1975).

Hofstra and Hall (1975) analyzed groundwater samples from the mountainous part of Jefferson 

County, an area of similar geology near the study area, 

and used a chloride concentration of 4 mg/L or greater 

to indicate chloride concentrations above background 

levels. Only two sites (fig. 3, GW4 and GW5) 

exceeded this criterion (Stevens and others, 1997). 

Because these sites are downslope from parts of the 

Table 28. Selected bottom-sediment chemical concentrations for lake and reservoir sites, water years 1995–97

[--, no data; mg/kg, milligrams per kilogram; μg/g, micrograms per gram; <, less than; if more than one sample was collected, maximum concentration is 

listed]

Constituent Units

Station

(fig. 2)

L1 L2 L3 L4 L5 L6

Nitrogen, ammonia total as N mg/kg 280 -- 50 94 -- --

Nitrogen, ammonia plus organic total as N mg/kg 9,200 -- 1,900 3,900 -- --

Phosphorus, total as P mg/kg 8,000 -- 910 800 -- --

Arsenic, total as As μg/g 13 2 3 7 <10 <10

Cadmium, total as Cd μg/g 2 -- <2 -- <2 3

Copper, total as Cu μg/g 49 60 73 160 3 31

Iron, total as Fe μg/g 130,000 6,100 79,000 55,000 9,300 29,000

Lead, total as Pb μg/g 90 30 63 330 18 450

Manganese, total as Mn μg/g 4,700 1,200 2,300 650 170 1,800

Mercury, total as Hg μg/g .05 .05 .53 .28 -- --

Zinc, total as Zn μg/g 170 180 210 2,000 28 1,000

PCB,1

 total μg/kg 10 22 <2 -- -- --

DDE2 μg/kg <.9 .7 <.2 -- -- --

DDD3 μg/kg .9 <.4 <.2 -- -- --

1polychlorinated biphenyl.

2dichlorodiphenyldichloroethylene.

31,1-dichloro-2,2-bis(p-chlorophenyl)ethane.
72 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Guanella Pass road treated with magnesium chloride 

(MgCl2), this applied dust inhibitor is a likely source 

of chloride that has migrated into the ground water. 

Scatterplots of major ionic constituents and 

specific conductance in ground-water samples might 

show outliers that could relate to applications of 

magnesium or sodium chloride. A scatterplot of 

magnesium with specific conductance (fig. 26) shows 

that magnesium concentration correlates well with 

specific conductance except at GW5, which tends to 

have a larger magnesium concentration than the 

specific-conductance correlation would predict. The 

chloride concentration at GW5, 5.8 mg/L, also is 

the second largest among all sampled ground-water 

sites. Sodium concentration has a poorer relation with 

specific conductance than the relation between magnesium concentration and specific conductance (fig. 26). 

Sampling site GW3 has a higher sodium concentration 

than the specific-conductance relation would predict, 

but the chloride concentration is too small to indicate 

any possible effect of NaCl applications. Chloride 

concentration is not well correlated with specific 

0 0

20

20

40

60

80

100

0

40

60

80

80

80

100

60

60

40

40

20

20

0

20

40

60

80

80

100

20

40

60

80

0

60

40

20

100

100

EXPLANATION

SULFATE + CHLORIDE

PERCENT

CALCIUM + MAGNESIUM

SULFATE

CARBONATE + BICARBONATE

100

80

60

40

20

0

PERCENT

CHLORIDE

SODIUM + POTASSIUM

PERCENT

MAGNESIUM

CALCIUM

100

100

80

60

40

20

0

80

60

40

20

0

GW1

GW2

GW3

GW4

GW5

GW6

GW7

GW8

GW9

GW10

GW11

GW12

GW13

GW14

GW15

Ground-water sites 

shown in figure 3

Figure 25. Chemical composition of ground-water samples collected during water years 1995–97.
CHARACTERIZATION OF WATER RESOURCES 73

0 100 200 300 400 500 600

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

0

30

10

20

MAGNESIUM CONCENTRATION,

IN MILLIGRAMS PER LITER

GW5

0 100 200 300 400 500 600

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

0

30

10

20

SODIUM CONCENTRATION,

IN MILLIGRAMS PER LITER

0 100 200 300 400 500 600

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

0

20

5

10

15

GW3

1 234567 8

CALCIUM:MAGNESIUM MASS RATIO

0

20

5

10

15

CHLORIDE CONCENTRATION,

IN MILLIGRAMS PER LITER 

GW4

GW7 GW10

GW5

GW4

GW5

Figure 26. Relations of magnesium, sodium, and chloride concentrations and specific conductance, and the 

relation of chloride concentration and the mass ratio of calcium to magnesium, for ground-water samples collected 

during water years 1995–97.
74 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

conductance (fig. 26) probably because the source 

of chloride is precipitation or runoff, not rock weathering, in this geologic setting (Bassett and others, 

1992). Chloride concentrations from two sampling 

sites were larger than 4 mg/L: GW4 and GW5 

(Stevens and others, 1997). Both sampling sites are 

downslope from sections of roads treated with magnesium chloride (MgCl2). 

A scatterplot of chloride to calcium:magnesium 

ratio (Ca:Mg) (fig. 26) shows that the two largest chloride concentrations correspond to samples with low 

Ca:Mg ratios. Large chloride to Ca:Mg ratios could 

indicate influence by MgCl2 runoff. Because the mass 

of chloride in MgCl2 is almost three times greater than 

magnesium, the increase in chloride concentrations 

will be more obvious than the increase in magnesium. 

Nutrients

Nutrient concentrations in ground water 

were small (Appendix table 50) and similar to those 

measured in mountainous areas of similar geology 

(Hofstra and Hall, 1975). Dissolved nutrient concentrations also were similar to concentrations measured 

in stream water. Dissolved nitrite plus nitrate was the 

nutrient species most frequently reported at concentrations greater than the laboratory MRL, with a median 

concentration of 0.08 mg/L as N and a range of less 

than 0.05 to 0.15 mg/L as N (table 50). Water from 

wells GW8 and GW10 (fig. 3) had the largest 

dissolved ammonia concentrations of 0.02 mg/L 

(Stevens and others, 1997; Stevens, 2000). Total or 

dissolved ammonia plus organic nitrogen was not 

detected at concentrations greater than laboratory 

MRL. Total phosphorus concentrations also were 

small, ranging from less than 0.01 to 0.03 mg/L as P 

(table 50). All dissolved orthophosphate concentrations were less than the MRL except at GW5 

(0.001 mg/L as P), GW9 (0.002 mg/L as P), and 

GW10 (0.01 mg/L as P) (Stevens and others, 1997; 

Stevens, 2000). However, there were two reporting 

limits (0.001 and 0.01 mg/L), and many samples were 

analyzed at the higher reporting limit.

Trace Elements

Compared to the dissolved phase, particulatephase concentrations of trace elements were relatively 

small, as indicated by differences between total 

recoverable and dissolved concentrations (Stevens 

and others, 1997; Stevens, 2000). Dissolved-phase 

concentrations were small except for occasional large 

concentrations of iron, manganese, and zinc. Large 

dissolved zinc (4,600 μg/L) and dissolved copper 

(9 μg/L) concentrations in campground wells could 

indicate a bias from trace elements leaching into well 

water from handpump or well materials. Concentrations of zinc and copper in samples collected from 

campground sites (GW2, GW3, GW4, GW7, GW8, 

and GW15) were all larger than in samples collected 

from springs (all others). Dissolved uranium was 

present in a few samples. In 1995, a relatively large 

concentration of 67 μg/L of uranium was determined 

in a sample from a campground well (GW3). The next 

largest uranium concentration in the 1995 sample set, 

however, was 5 μg/L (GW1), so the large concentration does not seem representative of uranium concentrations in the area. In 1997, a sample from GW3 

had a uranium concentration of 44 μg/L, basically 

confirming the relatively large concentration in the 

1995 sample. A possible source of uranium is groundwater contact with uranium-bearing rocks that are 

present in some crystalline rocks of the Colorado 

Front Range (Hills and others, 1982).

Comparisons with Water-Quality 

Standards

Stream and ground-water standards are used 

in this report to assess water quality. Water-quality 

standards for Colorado and other applicable guidelines 

are used to evaluate streams near the Guanella Pass 

road. Ground-water quality is evaluated on the basis of 

Colorado and U.S. Environmental Protection Agency 

(USEPA) drinking-water standards.

Streams

Water-quality standards for streams in Colorado 

are based on use classifications such as aquatic life, 

recreation, water supply, and agriculture.

Colorado Water-Quality Standards

In Colorado, water-quality standards are 

determined by the State Water Quality Control 

Commission and consist of a narrative or numeric 

restriction established to protect the beneficial uses 

of water. Some water-quality standards for streams 

are set to specific values or concentrations (such as 

dissolved oxygen, pH, nitrite, nitrate, chloride, sulfate, 

iron, and manganese). Others, un-ionized ammonia 

and some trace elements, are usually site specific and 
CHARACTERIZATION OF WATER RESOURCES 75

use hardness data and equations for each element to 

calculate standards (Colorado Department of Public 

Health and Environment, Water Quality Control 

Division, 1996). In certain cases (such as Leavenworth 

Creek CC9), fixed numeric standards have been established that reflect site-specific conditions and may 

specify trace-element phases and analytical techniques 

(such as dissolved or total recoverable methods).

Trace-element concentrations are assumed to be 

dissolved unless designated otherwise by the numeric 

standards (Colorado Department of Public Health and 

Environment, Water Quality Control Division, 1996). 

Acute standards are values or concentrations not to be 

exceeded for 1 day. Chronic standards are not to be 

exceeded by the 85th percentile of sample concentrations in a representative period. Extraordinary ephemeral or seasonal conditions do not constitute violations. 

Stream standard concentrations and values are not 

to be exceeded more than once every 3 years on the 

average (Colorado Department of Public Health and 

Environment, Water Quality Control Division, 1996). 

Thus, continued systematic monitoring is needed to 

determine compliance with or exceedance of a 

standard.

The State of Colorado specifies that hardness 

concentrations used to calculate the trace-element 

standards be computed from the lower 95-percent 

confidence limit of the mean hardness at the periodic 

low-flow criteria determined from regression analysis 

of site-specific or regional data. In this study, however, 

the length of record and current data were insufficient 

for this method. Therefore, hardness concentrations 

were determined from analysis of water samples 

collected at the time of sampling or were estimated 

from a site-specific hardness logarithmic regression 

with specific conductance (table 29). Hardness at CC9 

was estimated from a regression that included all hardness concentrations for study area streams because 

insufficient site-specific hardness data were available 

for the site.

Preliminary estimates of the Colorado waterquality standards for six stream-sampling sites adjacent to the Guanella Pass road (table 30) were 

calculated on the basis of numeric fixed standards 

or equations (Table of Value Standards [TVS]) for 

each element (Colorado Department of Public Health 

and Environment, Water Quality Control Division, 

1996). Laboratory MRL’s for trace elements such as 

cadmium, mercury, silver, and lead were commonly 

too high to determine concentrations at the level of the 

standard. These constituents might be present in the 

sample at concentrations lower than the laboratory 

MRL but higher than the standard. Certain constituents listed in the Colorado water-quality standards 

were not analyzed in the samples (for example, chlorine, cyanide, sulfide, and boron). 

Based on all samples collected in water 

years 1995–97, standards for dissolved oxygen, pH, 

chloride, sulfate, un-ionized ammonia, nitrate, total 

recoverable arsenic, and total recoverable chromium 

were not exceeded at any of the sampling sites along 

the Guanella Pass road (table 30).

Concentrations of water-quality constituents 

from South Clear Creek above Naylor Creek (CC2) 

exceeded both the dissolved and total recoverable 

fixed chronic standards for iron and manganese 

(table 30) at certain times. At South Clear Creek above 

Lower Cabin Reservoir (CC5), dissolved and totalrecoverable iron and total recoverable manganese also 

exceeded the fixed chronic standard in some samples. 

Table 29. Regression equations and information used to compute hardness concentrations at selected sites, water 

years 1995–97

[a, intercept coefficient; b, slope coefficient; H, hardness; SC, specific conductance; Cb, bias correction factor; all sites, a regression of available hardness 

and specific-conductance data at all sites; <, less than] 

Site

(fig. 1)

Water

year

Number of 

samples

Natural logarithm form: LN(H) = b + a LN (SC)

Exponentiated form:

H = e(b)SC(a)Cb

Coefficients

Standard

error

Adjusted

coefficient of

determination

(r2)

Bias

correction 

factor

(Cb)

a p-value b p-value

CC2 1995–97 29 1.0170 <0.0001 –0.9070 <0.0001 0.074 0.98 1.002 H = (.4047)SC(1.017)

CC5 1995–97 15 .9166 <.0001 –.5019 .1140 .039 .92 1.001 H = (.6060)SC(.9166)

GC5 1995–97 31 1.0093 <.0001 –1.0205 .0002 .045 .89 1.001 H = (.3608)SC(1.009)

GC11 1995–97 26 .9447 <.0001 –.8391 <.0001 .044 .96 1.001 H = (.4325)SC(.9447)

All study sites 1995–97 165 1.0840 <.0001 –1.2825 <.0001 .097 .95 1.005 H = (.2786)SC(1.0840)
76 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Table 30. Water-quality standards for selected stream-sampling sites along the Guanella Pass road for constituents and 

properties sampled

[mg/L, milligrams per liter; --, no data or no standard; <, less than; μg/L, micrograms per liter; ?, reporting limit above standard or part of range in standard; 

max, maximum; min, minimum; standards from Colorado Department of Public Health and Environment, Water Quality Control Commission (1996)]

Property or constituent

Total

number of

samples

Max

or Min

standard

Range of

concentration

Range of

standard

Number of

exceedances

Min Max Chronic Acute Chronic Acute

Site CC2

Dissolved oxygen, mg/L 38 Min 6.8 11.5 6.0 -- 0 --

pH, standard units 44 Min/max 7.2 8.3 6.5–9.0 -- 0 --

Chloride, dissolved, mg/L 44 Max .5 36 250 -- 0 --

Sulfate, dissolved, mg/L 42 Max 1.3 7.5 250 -- 0 --

Un-ionized ammonia, mg/L 17 Max .000005 .00006 .02 0.03–0.10 0 0

Nitrate, dissolved, mg/L 37 Max <.005 .12 10 10 0 0

Arsenic, total recoverable, μg/L 2 Max <1 <1 -- 50 -- 0

Cadmium, dissolved, μg/L 2 Max <1 <1 .3–.6 .5–1.6 ? ?

Chromium III, dissolved, μg/L 2 Max -- -- -- -- -- --

Chromium III, total recoverable, μg/L 2 Max <1 20 -- 50 -- 0

Copper, dissolved, μg/L 42 Max <1 2 2–11 3–16 0 0

Iron, dissolved, μg/L 42 Max 26 440 300 -- 11 --

Iron, total recoverable, μg/L 42 Max 60 72,000 1,000 -- 16 --

Lead, dissolved, μg/L 8 Max <1 <1 5 5–34 0 0

Manganese, dissolved, μg/L 42 Max <1 130 50 -- 2 --

Manganese, total recoverable, μg/L 42 Max <10 1,900 1,000 -- 4 --

Mercury, total recoverable, μg/L 2 Max <.1 <.1 .01 -- ? --

Nickel, dissolved, μg/L 2 Max <1 <1 24–51 230–496 0 0

Selenium, total recoverable, μg/L 2 Max <1 <1 10 -- 0 --

Silver, dissolved, μg/L 2 Max <1 <1 .003–.018 .09–.50 ? ?

Zinc, dissolved, μg/L 42 Max 2 17 22–96 25–106 0 0

Site CC5

Dissolved oxygen, mg/L 31 Min 7.1 11.6 6.0 -- 0 --

pH, standard units 38 Min/max 7.3 8.3 6.5–9.0 -- 0 --

Chloride, dissolved, mg/L 34 Max .3 1.9 250 -- 0 --

Sulfate, dissolved, mg/L 29 Max 2.2 6.6 250 -- 0 --

Un-ionized ammonia, mg/L 26 Max .000008 .0002 .02 .04–.12 0 0

Nitrate, dissolved, mg/L 28 Max .048 .18 10 -- 0 --

Arsenic, total recoverable, μg/L 8 Max <1 <1 -- 50 -- 0

Cadmium, dissolved, μg/L 8 Max <1 <1 .4–.4 .8–.9 ? ?

Chromium III, dissolved, μg/L 8 Max -- -- -- -- -- --

Chromium III, total recoverable, μg/L 8 Max <1 8 -- 50 -- 0

Copper, dissolved, μg/L 29 Max <1 2 3–5 4–7 0 0

Iron, dissolved, μg/L 29 Max 35 320 300 -- 1 --

Iron, total recoverable, μg/L 32 Max 120 110,000 1,000 -- 14 --

Lead, dissolved, μg/L 13 Max <1 <1 5 10–18 0 0

Manganese, dissolved, μg/L 29 Max 2 19 50 -- 0 --

Manganese, total recoverable, μg/L 32 Max <10 2,300 1,000 -- 1 --

Mercury, total recoverable, μg/L 8 Max <.1 <.1 .01 -- ? --

Nickel, dissolved, μg/L 8 Max <1 1 33–35 323–342 0 0

Selenium, total recoverable, μg/L 8 Max <1 <1 10 -- 0 0

Silver, dissolved, μg/L 8 Max <1 <1 .007–.008 .2–.2 ? ?

Zinc, dissolved, μg/L 29 Max 1 10 29–49 33–54 0 0
CHARACTERIZATION OF WATER RESOURCES 77

Site CC9

Dissolved oxygen, mg/L 16 Min 8.4 11.3 6.0 -- 0 --

pH, standard units 19 Mini/max 7.0 8.8 6.5–9.0 -- 0 --

Chloride, dissolved, mg/L 6 Max .1 .7 250 -- 0 --

Sulfate, dissolved, mg/L 6 Max 7.9 35 250 -- 0 --

Un-ionized ammonia, mg/L 5 Max .000003 .0002 .02 0.03–0.07 0 0

Nitrate, dissolved, mg/L 6 Max .044 .11 10 -- 0 --

Arsenic, total recoverable, μg/L 3 Max <1 <1 -- 50 -- 0

Cadmium, total recoverable, μg/L 3 Max <1 2 0.4 -- 1 --

Chromium III, dissolved, μg/L -- Max -- -- -- -- -- --

Chromium III, total recoverable, μg/L 3 Max <1 4 -- 50 -- 0

Copper, total recoverable, μg/L 7 Max 1 14 50 -- 0 --

Iron, dissolved, μg/L 6 Max 4 110 300 -- 0 --

Iron, total recoverable, μg/L 7 Max 10 2,600 1,000 -- 2 --

Lead, total recoverable, μg/L 7 Max 2 71 4 -- 5 --

Manganese, dissolved, μg/L 6 Max 7 47 50 -- 0 --

Manganese, total recoverable, μg/L 7 Max <10 370 1,000 -- 0 --

Mercury, total recoverable, μg/L 3 Max <.1 <.1 .05 -- ? --

Nickel, total recoverable, μg/L 3 Max 1 4 50 -- 0 --

Selenium, total recoverable, μg/L 3 Max <1 <1 10 -- 0 --

Silver, total recoverable, μg/L 3 Max <1 <1 .1 -- ? --

Zinc, total recoverable, μg/L 7 Max 130 430 450 -- 0 --

Site CC10

Dissolved oxygen, mg/L 2 Min 8.2 9.1 6.0 -- 0 --

pH, standard units 2 Min/max 7.9 8.0 6.5–9.0 -- 0 --

Chloride, dissolved, mg/L 2 Max .9 1.5 250 -- 0 --

Sulfate, dissolved, mg/L 2 Max 9 12 250 -- 0 --

Un-ionized ammonia, mg/L 2 Max .0002 .0003 .02 .09–.10 0 0

Nitrate, dissolved, mg/L 2 Max .06 .09 10 -- 0 --

Arsenic, total recoverable, μg/L 2 Max <1 <1. -- 50 -- 0

Cadmium, dissolved, μg/L 2 Max <1 <1. .5–.6 1.2–1.7 ? 0

Chromium III, dissolved, μg/L 2 Max -- -- -- -- -- --

Chromium III, total recoverable, μg/L 2 Max <1 1 -- 50 -- 0

Copper, dissolved, μg/L 2 Max 1 4 5–6 7–9 0 0

Iron, dissolved, μg/L 2 Max 9 66 300 -- 0 --

Iron, total recoverable, μg/L 2 Max 40 740 1,000 -- 0 --

Lead, dissolved, μg/L 2 Max <1 1 5 18–28 0 0

Manganese, dissolved, μg/L 2 Max 2 23 50 -- 0 --

Manganese, total recoverable, μg/L 2 Max 10 90 1,000 -- 0 --

Mercury, total recoverable, μg/L 2 Max <.1 <.1 .01 -- ? --

Nickel, dissolved, μg/L 2 Max <1 2 44–54 426–521 0 0

Selenium, total recoverable, μg/L 2 Max <1 <1 10 -- 0 0

Silver, dissolved, μg/L 2 Max <1 <1 .01–.02 .4–.6 ? ?

Zinc, dissolved, μg/L 2 Max 42 130 45–56 49–62 1 1

Table 30. Water-quality standards for selected stream-sampling sites along the Guanella Pass road for constituents and 

properties sampled—Continued

[mg/L, milligrams per liter; --, no data or no standard; <, less than; μg/L, micrograms per liter; ?, reporting limit above standard or part of range in standard; 

max, maximum; min, minimum; standards from Colorado Department of Public Health and Environment, Water Quality Control Commission (1996)]

Property or constituent

Total

number of

samples

Max

or Min

standard

Range of

concentration

Range of

standard

Number of

exceedances

Min Max Chronic Acute Chronic Acute
78 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Site GC5

Dissolved oxygen, mg/L 42 Min 7.2 10.4 6.0 -- 0 --

pH, standard units 47 Mini/max 7.1 8.3 6.5–9.0 -- 0 --

Chloride, dissolved, mg/L -- Max -- -- -- -- -- --

Sulfate, dissolved, mg/L -- Max -- -- -- -- -- --

Un-ionized ammonia, mg/L 18 Max .000009 .0004 .02 .06–.12 0 0

Nitrate, dissolved, mg/L -- Max -- -- -- -- -- --

Arsenic, total recoverable, μg/L 2 Max <1 <1 100 -- 0 --

Cadmium, dissolved, μg/L 2 Max <1 <1 .3–.3 .6–.6 ? ?

Chromium III, dissolved, μg/L 2 Max <1 2 51–55 426–465 0 0

Chromium III, total recoverable, μg/L -- Max -- -- -- -- -- --

Copper, dissolved, μg/L 40 Max <1 3 2–3 3–4 1 1

Iron, dissolved, μg/L 40 Max 43 270 300 -- 0 --

Iron, total recoverable, μg/L 45 Max 140 4,000 1,000 -- 7 --

Lead, dissolved, μg/L 8 Max <1 <1 .3–.4 6–7 ? 0

Manganese, dissolved, μg/L -- Max -- -- -- -- -- --

Manganese, total recoverable, μg/L 45 Max <10 100 1,000 -- 0 --

Mercury, total recoverable, μg/L 2 Max <.1 <.1 .01 -- ? --

Nickel, dissolved, μg/L 2 Max <1 <1 26–28 251–272 0 0

Selenium, total recoverable, μg/L 2 Max <1 <1 17 135 0 --

Silver, dissolved, μg/L 2 Max <1 1 .004–.005 .11–.13 1 1

Zinc, dissolved, μg/L 40 Max 2 10 19–29 21–32 0 0

Site GC11

Dissolved oxygen, mg/L 40 Min 7.2 10.9 6.0 -- 0 --

pH, standard units 47 Min/max 7.0 7.9 6.5–9.0 -- 0 --

Chloride, dissolved, mg/L -- Max -- -- -- -- -- --

Sulfate, dissolved, mg/L -- Max -- -- -- -- -- --

Un-ionized ammonia, mg/L 18 Max .000005 .00008 .02 .04–.11 0 0

Nitrate, dissolved, mg/L -- Max -- -- -- -- -- --

Arsenic, total recoverable, μg/L 2 Max <1 <1 100 -- 0 --

Cadmium, dissolved, μg/L 3 Max <1 <1 .3–.4 .5–.8 ? ?

Chromium III, dissolved, μg/L 2 Max <1 <1 44–64 367–540 0 0

Chromium III, total recoverable, μg/L -- Max -- -- -- -- -- --

Copper, dissolved, μg/L 39 Max 1 4 2–5 2–6 1 1

Iron, dissolved, μg/L 39 Max <3 430 300 -- 1 --

Iron, total recoverable, μg/L 43 Max 230 23,000 1,000 -- 19 --

Lead, dissolved, μg/L 7 Max <1 1 .3–.8 4–16 1 0

Manganese, dissolved, μg/L -- Max -- -- -- -- -- --

Manganese, total recoverable, μg/L 43 Max 60 900 1,000 -- 0 --

Mercury, total recoverable, μg/L 2 Max <.1 <.1 .01 -- ? --

Nickel, dissolved, μg/L 2 Max 1 3 23–32 219–313 0 0

Selenium, total recoverable, μg/L 2 Max <1 <1 17 135 0 0

Silver, dissolved, μg/L 2 Max <1 <1 .003–.006 .08–.17 ? ?

Zinc, dissolved, μg/L 39 Max <3 85 16–41 17–46 21 17

Table 30. Water-quality standards for selected stream-sampling sites along the Guanella Pass road for constituents and 

properties sampled—Continued

[mg/L, milligrams per liter; --, no data or no standard; <, less than; μg/L, micrograms per liter; ?, reporting limit above standard or part of range in standard; 

max, maximum; min, minimum; standards from Colorado Department of Public Health and Environment, Water Quality Control Commission (1996)]

Property or constituent

Total

number of

samples

Max

or Min

standard

Range of

concentration

Range of

standard

Number of

exceedances

Min Max Chronic Acute Chronic Acute
CHARACTERIZATION OF WATER RESOURCES 79

At site CC9, Leavenworth Creek at the mouth, 

the total recoverable cadmium, lead, and iron (chronic) 

fixed standards were exceeded (table 30). Only total 

recoverable analyses are specified at site CC9. The few 

cadmium and lead exceedances may be related to ore 

deposits and acid-sulfate weathering processes. At 

site CC10, South Clear Creek at Georgetown, dissolved 

zinc exceeded the chronic and acute standards. Sources 

of zinc that contribute to exceedance of the standard at 

CC10 are Leavenworth Creek and possibly the mines 

on the hillsides downstream from the South Clear 

Creek/Leavenworth Creek confluence.

At site GC5, Duck Creek near Grant, dissolved 

copper and silver concentrations each exceeded acute 

and chronic standards in one of two samples. The 

chronic standard for total recoverable iron also was 

exceeded in 7 of 45 samples (table 30). 

At site GC11, on Geneva Creek, dissolved 

copper exceeded the acute and chronic standards 

in a single sample. Dissolved iron and lead each 

exceeded the chronic standard in a single sample. Total 

recoverable iron concentrations at GC11 exceeded the 

1,000-mg/L chronic standard in 19 of 43 samples. 

Dissolved zinc concentrations exceeded the standards 

in numerous samples at GC11: chronic 54 percent, and 

acute 44 percent of all samples (table 30).

The zinc exceedances at GC11 are associated 

with low-flow periods when the contributions from 

ground water are a larger percentage of flow and the 

dilution and neutralizing effect of nonacidic tributaries 

is small. Acid-sulfate weathering (Bassett and others, 

1992) at the headwaters of Geneva Creek is the major 

source of the trace elements (copper, iron, lead, and 

zinc).

Total recoverable iron in streams can exceed 

chronic standards during snowmelt or stormflow due 

to the increase in iron associated with suspendedsediment during these periods (Gaggiani and others, 

1987). Therefore, large suspended-sediment concentrations may cause exceedance of standards because 

of total recoverable iron content. The relation of 

total recoverable iron concentration and associated 

suspended-sediment concentration for samples 

collected during the high-flow sampling (1995) in 

Stevens (1999) indicates that the total recoverable iron 

standard of 1,000 μg/L would commonly be exceeded 

in the range of suspended-sediment concentrations 

measured. This relation of mainly particulate iron with 

suspended sediment and the presence of large concentrations of suspended sediment in road-runoff samples 

indicates that road runoff to streams could contribute 

to seasonally large concentrations of total recoverable 

iron. A similar effect could exist for manganese. 

Provisions for seasonal exceedance incorporated into 

the water-quality standards might disqualify naturally 

occurring suspended-sediment-related exceedances. 

Also, the use of the 85th percentile of the water-year 

data for comparison to the chronic standard will 

reduce the influence of large, seasonal concentrations.

Acid-sulfate weathering in upper Geneva Creek 

also produces large concentrations of total recoverable 

iron (Stevens and others, 1997) that may contribute to 

water-quality-standard exceedance in affected streams. 

For about the same suspended-sediment concentration, 

total recoverable iron concentrations from upper 

Geneva Creek sites (GC6, GC7, and GC9) were much 

larger than from all other sites sampled during highflow (Stevens, 1999). Precipitating ferric iron along 

Geneva Creek is probably the cause of the iron-rich 

sediment. 

Most of the stream trace-element standards 

are not likely to be exceeded as a result of road-runoff 

discharged into streams because the standards specify 

primarily dissolved phases, and the predominant phase 

associated with road runoff in the study area seems to 

be particulate (Stevens, 1999). Some of the trace 

elements associated with particles are probably 

adsorbed to sediment. But without lowering the pH, 

these trace elements are not likely to be desorbed or 

weathered from particles (Davis and others, 1991). 

Stream reaches that are paralleled by the Guanella 

Pass road are generally of neutral pH, although 

Geneva Creek is slightly acidic between Duck and 

Scott Gomer Creeks. If desorption is contributing trace 

elements to neutral-pH streams, the effect is small 

because concentrations in these streams are small. If 

the desorbed trace elements substantially alter water 

quality in neutral-pH streams, then larger dissolved 

trace-element concentrations than those measured 

would be evident, particularly in streams that receive 

road runoff. 

Other Guidelines

Suspended-sediment concentration and turbidity 

were not regulated by the State of Colorado during 

1995–97. However, FHWA does have a Special 

Contract Requirement (SCR) that normally contains 

the following statement whenever a project might 

affect an adjacent stream (Robert Nestel, Federal 

Highway Administration, written commun., 1998):
80 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

The construction project engineer will be 

responsible for monitoring turbidity during the 

construction of this project to assure compliance 

with state water quality standards. The turbidity 

will be measured using an HF-DRT 15 turbidimeter or equivalent. Measurements will be taken 

upstream from the project area (as a control) 

and 150 m (500 feet) downstream in the area 

of highest turbidity whenever noticeable turbidity 

is being generated from the project. If these 

measurements show an increase of 10 Nephelometric Turbidity Units (NTU) or more, the Engineer shall suspend construction operations in 

the vicinity of the problem area and modify the 

erosion control plan to eliminate the cause of 

high turbidity.

Fluctuations in turbidity of Guanella Pass 

streams can exceed 10 NTU in a day (see fig. 22). 

Careful monitoring would be necessary to quantify 

the difference between naturally occurring and roadconstruction-related increases in turbidity during 

snowmelt and rainfall.

For nutrients in streams, USEPA recommends 

that eutrophication risk be controlled by limiting total 

phosphates to less than 0.05 mg/L (as phosphorus) in a 

stream at the point where it enters a lake or reservoir. 

Moreover, total phosphorus (as phosphorus) should be 

limited to concentrations less than 0.1 mg/L in streams 

that do not discharge directly into lakes or reservoirs 

(U.S. Environmental Protection Agency, 1986). 

Although total phosphates were not determined, the 

dissolved orthophosphorus concentrations in the 

Guanella Pass area streams did not exceed 0.05 mg/L. 

During storm runoff, total phosphorus concentrations 

sampled in Guanella Pass streams occasionally 

exceeded the 0.1-mg/L guideline.

Ground Water

The Colorado ground-water standards 

(drinking-water related) were used to evaluate 

ground-water quality at sites where water is used for 

human consumption (Colorado Department of Public 

Health and Environment, Water Quality Control 

Commission, 1997; U.S. Environmental Protection 

Agency, 1996). Ground water is used for drinking at 

one spring (GW6) and at Forest Service campgrounds 

and picnic grounds (GW2, GW3, GW4, GW7, GW8, 

and GW15). Drinking-water-quality standards for 

selected constituents are presented in table 31. Primary 

maximum contaminant levels (MCL’s) regulate the 

maximum permissible concentration of a contaminant 

in water at the tap, are health related, and are legally 

enforceable only when they pertain to a public 

water supply. Constituent concentrations were 

larger than the MCL only in a single well (GW3) 

for a single constituent (uranium) (data from Stevens 

and others, 1997; Stevens, 2000). Well GW3 (west 

loop of the Guanella Pass campground) contained 

67 μg/L of uranium in August 1995 and 44 μg/L in 

September 1997 (Stevens and others, 1997), exceeding 

the USEPA-proposed primary MCL of 20 μg/L. The 

bedrock in the study area is similar to common metamorphic and igneous rocks of the Colorado Front 

Range where uranium occurs (Hofstra and Hall, 1975; 

Hills and others, 1982). 

Table 31. Drinking-water-quality standards for selected 

constituents and properties

[Standards from U.S. Environmental Protection Agency (1996) and 

Colorado Department of Public Health and Environment, Water Quality 

Control Commission (1997); NTU, nephelometric turbidity units]

Water-quality constituent 

or property Standards

Major inorganic constituents

(milligrams per liter)

Sulfate 1250

Chloride 1250

Fluoride 2

4

Dissolved solids 1500

Nitrite plus nitrate 210

Trace elements

(micrograms per liter)

Arsenic 250

Barium 22,000

Cadmium 25

Chromium (total) 2100

Copper 1

1000

Iron 1300

Lead 215

Manganese 150

Mercury 2

2

Selenium 2

50

Zinc 15,000

Uranium 2,420

Other

Turbidity (NTU) 2,3.5–1.0

1Secondary maximum contaminant level. These standards apply to 

constituents in drinking water that primarily affect the esthetic qualities 

relating to the public acceptance of drinking water and are not federally 

enforceable but are intended as guidelines for States. 2

Primary maximum contaminant level. These regulations are the 

maximum permissible level of a contaminant in water at the tap and are 

health related. Standards only apply to public drinking-water supply 

systems. 3

Performance standard.

4

Proposed.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 81

Dissolved iron, manganese, and zinc concentrations approach or exceeded the secondary MCL’s 

in some of the water samples from wells (data from 

Stevens and others, 1997; and Stevens, 2000). These 

constituents may affect the appearance and taste of 

water used for drinking. The turbidity in some samples 

from wells was greater than the standard, possibly 

because of precipitating iron during sample 

processing. 

Water samples are routinely collected from 

Forest Service area campground wells by State, 

county, and private contractors for the analysis of 

nitrate, fecal coliform, and selected major ions and 

trace elements to assess drinking-water quality 

(Clear Creek Ranger District and South Platte Ranger 

District, written commun., 1995). Neither fecal 

coliform nor nitrate was reported at concentrations 

greater than the standards.

CHARACTERIZATION OF GUANELLA 

PASS ROAD RUNOFF

This section of the report presents a summary 

of selected references on the subject of forest road 

hydrology, hydrology and water quality of Guanella 

Pass road runoff, sources and transport of road runoff, 

and the potential effects of road runoff on receiving 

water.

Several components (cutslope, fillslope, road 

surface, and ditch) (fig. 27) of the Guanella Pass road 

contribute sediment and other water-quality constituents to streams from erosion. Hydraulic linkage is 

defined here as the surface-runoff connections 

between road-drainage features (roadside ditches 

and culverts) and streams or lakes. Less-direct transport to streams for dissolved constituents such as road 

salt can be caused by the infiltration of road runoff to 

ground water that then discharges to streams. 

Background Information on Forest Road 

Hydrology

 Although substantial work has been done on 

the effects of highway runoff on water quality (Dupuis 

and others, 1985; Young and others, 1996), forest 

roads are smaller in scale, have smaller traffic volume, 

and often are located in areas of more pristine water 

quality, which might not compare to highway-runoff 

studies in more urbanized areas. Hydrology and sediment transport related to forest roads, however, have 

been extensively studied. The effects studied are 

generally in the categories of water discharge, chemistry, sediment erosion, and biota. Forest road studies 

also generally emphasize erosion processes, sediment 

transport and delivery (both instream and through the 

buffer zone), and the effects of management practices.

Some studies found that road effects are related 

to changes in the timing and intensity of runoff in 

response to precipitation (King and Tennyson, 1984; 

Jones and Grant, 1996). Other studies reported no 

changes (Wright and others, 1990) or changes only 

when large areas were disturbed by roads (more than 

12 percent of the basin area) (Harr and others, 1975). 

Changes in runoff are important because of the 

influence of runoff on sediment transport, channel 

Stream

Fillslope

Buffer zone

Road surface or prism

Cross-drain or

culvert

Ditch

Cutslope

Undisturbed hillslope

Figure 27. Schematic of a forest road.
82 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

stability, and substrate particle size (MacDonald 

and others, 1991). Roads affect watershed runoff 

by decreasing infiltration capacity, increasing runoff 

to the stream, intercepting subsurface drainage, and 

increasing rates of snowmelt. Wemple and others 

(1996) suggest that roads that are hydraulically linked 

to streams are extensions of the stream-channel 

network and efficiently collect and deliver water from 

precipitation to the stream, resulting in increased 

volume and a rapid response of runoff to precipitation. 

Road runoff reaches receiving water through the linkages (rills, gullies, or ephemeral channels) that cross 

the buffer zone between the road and stream or lake. 

While paved-surface roads are less permeable than 

gravel roads, the unit hydrographs for runoff from the 

two road surfaces, paved and in-use gravel, are practically the same in timing and peak flow, indicating that 

the effect of the surface type on water discharge may 

be small (Reid and Dunne, 1984). 

The studies on the effects of forest management 

activities have focused primarily on the effects of 

silvicultural activities (such as timber harvest), not 

on road runoff exclusively. Dissolved oxygen, water 

temperature, and concentrations of nitrogen, phosphorus, and pesticides are recommended monitoring 

objectives to assess the effects of forest management 

activities (MacDonald and others, 1991). However, 

certain management activities such as mining or salt 

applications to roadways create the need for monitoring trace elements and major ions in surface water. 

Brown and Binkley (1994) analyzed available research 

for forested watersheds and concluded that water 

temperature generally increased, but dissolved 

oxygen, dissolved solids, nutrient, and pesticide/

herbicide concentrations in surface water were generally not altered substantially by forest management 

activities.

The effect of sediment transport from forest 

roads is well documented. Many studies have 

concluded that increases in suspended-sediment 

concentration (Sullivan, 1985; Harr and Fredricksen, 

1988; Davies and Nelson, 1993), turbidity (Anderson 

and Potts, 1987), and decreases in bed-material 

particle size (Eaglin and Hubert, 1993; Schnackenberg 

and MacDonald, 1998) are related to silvicultural 

activity. Several investigations have attempted to 

isolate the effects of roads and road construction 

alone (Brown and Krygier, 1971; Megahan and Kidd, 

1972; Beschta, 1978; Woolridge and Larson, 1980; 

Anderson and Potts, 1987; Grayson and others, 1993; 

Cline and others, 1982). The effects in some cases are 

short in duration, and recovery occurs with time or at 

the conclusion of the construction activity (Beschta, 

1978; Cline and others, 1982).

Research has provided information on erosional 

processes related to roads. Burroughs and King (1989) 

summarized erosion studies and management practices 

related to forest roads. They concluded that the road 

fillslope accounted for most (80 percent) of the sediment production immediately after road construction 

in an Idaho forest area, but that the road cutslope and 

roadside ditch became the primary source of sediment 

(83 percent) 4 years later. Fillslope sediment production is generally large immediately after construction 

and decreases exponentially over time (Burroughs and 

King, 1989). Sediment production sources and rates 

measured or estimated on forest roads by Reid and 

others (1981) indicate that cutslopes are a small source 

of sediment compared to the road surface for gravel 

roads, ranging from 0.4 percent (heavy-use roads) to 

50 percent (light-use roads) in a basin in Washington. 

In a sensitivity analysis of the components of 

insloping forest roads, the Water Erosion Prediction 

Project (WEPP) model estimated that the road surface 

and roadside ditches are more important contributors 

to sediment yield than the cutslope (Tysdal and others, 

1997). Road length between culverts, gradient, and 

soil type were important factors in erosion of the road 

surface, whereas the ditch length and channel roughness were important factors for the roadside ditch 

(Tysdal and others, 1997). 

Choice of road surface type can have a strong 

influence on sediment production. Heavy-use gravel 

roads in a Washington forest were estimated to 

produce 250 times more sediment than paved roads on 

average (Reid and Dunne, 1984). Paving resulted in a 

97-percent reduction of road-surface sediment production in an Idaho experiment (Burroughs and King, 

1989). When crushed rock was applied to dirt roads in 

3- to 6-inch lifts, road-surface sediment production 

was reduced by 70 to 92 percent compared to unprotected roads (Burroughs and King, 1989). 

Burroughs and King (1989) reported on the 

results of many experiments in best management 

practices. Mulches, seeding, and filter windrows 

have been shown to reduce fillslope and cutslope 

sediment production substantially. Reductions in 

fillslope-sediment production ranged from 7 to 

more than 90 percent, depending on treatment and 

site conditions. Reductions in cutslope-sediment 
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 83

production ranged from 32 to 86 percent, depending 

on treatment and site conditions. The application of 

gravel riprap to the shoulder ditch reduced sediment 

production in simulated rainfall experiments by 

24 percent. Overall, the recommended design of 

cutslope, ditch, and road surface was estimated to 

reduce sediment production by about 90 percent 

(Burroughs and King, 1989).

Other management practices such as the grading 

of roads and ditches are known to increase sediment 

yield (Grayson and others, 1993; Tysdal and others, 

1997). Increasing traffic volume also increases sediment yields (Wald, 1975; Reid and Dunne, 1984; 

Foltz, 1996). Research on logging roads in Oregon 

indicated that reduction of logging truck tire pressure 

reduced sediment production by more than 80 percent 

on some roads (Moore and others, 1995). Erosion at 

culvert outlets in one study was proportional to culvert 

spacing (Piehl and others, 1988). Sediment production 

was 4 to 17 times more on a road with marginalquality aggregate compared to good-quality aggregate 

(Foltz, 1996). Snowplowing was estimated to erode 

sediment from the road surface of the Pikes Peak road 

in Colorado, at the rate of 110 tons/acre (Chavez and 

others, 1993).

The biological effects of forest management 

activities that produce forest road runoff are not 

as well documented as the effects on sediment. Cline 

and others (1982) analyzed the effects of highway 

construction in a forest environment and determined 

that epilithic algae and benthic macroinvertebrates 

were adversely affected; however, these effects were 

short-lived and not severe. Eaglin and Hubert (1993) 

found positive correlation of fine sediment and 

embeddedness in streambeds with culvert density and 

a negative correlation of trout standing stocks with 

culvert density. In contrast, other studies indicate 

increases in primary productivity following forest 

disturbance, and this causes changes in algal and 

macroinvertebrate characteristics (Hansmann and 

Phinney, 1973; Newbold and others, 1980; Murphy 

and others, 1981). Lewis (1999) determined that 

the toxicity of magnesium chloride to boreal toads, 

rainbow trout, an invertebrate species, and an algal 

species was not substantial at the dilute concentrations 

estimated to be present after the road runoff is diluted 

by snowmelt. Reduction of light and siltation of 

substrate by sedimentation can reduce algae and 

macroinvertebrates by reducing primary productivity 

and preferred habitat (MacDonald and others, 1991).

Hydrology

Observations and monitoring of road runoff 

on Guanella Pass indicate that road runoff generally 

occurred during snowmelt and as a result of rainstorms. Ground-water seepage to the roadside 

ditches was rare, but small flows in spring and summer 

(May to August) were observed in a couple of small 

segments. Temperatures and solar radiation were low 

enough in September to allow snow accumulation on 

the road cutslopes and fillslopes, although melting 

occurred on warm days following the early fall snowstorms. Snowplowing generally kept the Guanella 

Pass road surface from becoming snowpacked until 

later in the fall. Plowed snow was stored in windrows 

mostly on the fillslope side, but some also was pushed 

to the cutslope side. Snowpack accumulation in the 

drainage area of the road (road surface, cutslopes 

and fillslopes, and roadside ditch) ranged from zero to 

several feet from September to May, depending upon 

altitude. At low-elevation road segments with southern 

exposure, melting commonly occurred on warm days 

all winter with little net accumulation. Elsewhere, 

melting of accumulated snow started at the lower 

elevations in March or April and progressed to higher 

altitudes in the following weeks. 

At high altitude (greater than 10,000 ft), snow 

accumulated on the road drainage area until late April 

or early May when vigorous melting began to occur on 

warm days. Road runoff was usually finished on lower 

segments of the road when it was just starting on 

higher segments of the road. Almost all road-related 

runoff due to melting snow was complete by the end 

of May or early June (Stevens, 2000). Culvert flows 

generally peaked in May at altitudes above 10,000 ft, 

indicating that the bulk of road runoff occurs before 

the general watershed peak-flow period, which occurs 

between late May and mid-June (Stevens, 2000).

Depending upon conditions and location, ice 

accumulated in some culverts and did not thaw before 

spring snowmelt began on the road. Plowing often left 

the roadside ditch full of snow and ice at the beginning 

of the road snowmelt period, so early runoff occupied 

the road surface near the edge of the ditch, which 

caused erosion of the roadbed. As melting of the 

plowed snowbank progressed, the runoff flow 

migrated toward the ditch. If the culvert was clogged 

with ice or snow or runoff was diverted away from the 

entrance by debris, flow continued down the road to 

the next open culvert, diversion ditch, or swale in the 
84 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

road, where it flowed across the road and continued 

downslope. Rills and deep trenches, caused by overflow of roadside ditches, formed across the road at 

times during WY’s 1995–97. After leaving the road, 

the runoff joined culvert or roadside-ditch flows and 

was diverted to the hillslope, where it flowed beneath 

the snowpack in the buffer zone. 

Rainstorms usually occurred during June 

through September on Guanella Pass, and they were 

most common in July and August. The storms were 

generally of short duration, occurring in late afternoon 

or evening. Frontal storms occasionally produced 

several days of intermittent rain. During this study, 

observations during some rainstorms indicated that 

runoff began first on the road surface (gravel or 

paved). In some areas, infiltration seemed to be occurring in the ditch because flows sometimes disappeared 

as they flowed down the ditch. Only small amounts of 

surface flow were observed on the cutslopes, although 

small slumps of slope material into the ditch occurred 

during heavy rain. Rills on some steep cutslopes indicated that overland flow does occur at times. However, 

the rills may be eroded not only during intense rain, 

but also possibly beneath snowpack as early melting 

occurs.

Instantaneous water discharge measured at 

miscellaneous culvert and roadside ditch sites generally was small compared to stream discharge and 

ranged from 0.004 to 0.153 ft3

/s (Stevens and others, 

1997; Stevens, 2000). A complete seasonal record 

of flow (WY’s 1996–97) was collected at only one 

culvert-monitoring site, CRD7 (fig. 28). The flow on 

86 percent of the days that had flow was due to snowmelt and 96 percent of the annual flow (0.408 acre-ft) 

was due to snowmelt. Maximum daily mean flow 

during WY 1996 was only 0.019 ft3

/s (Stevens, 2000). 

Site CRD7, draining an area of 0.687 acres, had flow 

for 43 days of a 144-day season in WY 1996 (Stevens, 

2000). In WY 1997, CRD7 had flow for 48 days of a 

138-day season (fig. 28). Flow on 58 percent of the 

days that had flow was due to snowmelt runoff, and 

77 percent of the annual flow (0.665 acre-ft) was due 

to snowmelt. Maximum daily mean flow during 

WY 1997 was 0.029 ft3

/s (Stevens, 2000). During 

water years 1996–97, the peak snowmelt period at 

CRD7 preceded the general basin peak flows at CC2 

and CC5, indicating that road runoff could enter 

streams when flow is low and dilution potential is 

smaller than that at peak streamflow (fig. 28). 

Water-Quality Characteristics

Water quality of road runoff was characterized 

using summary statistics of a subset (20 samples) of 

all samples (47 total) collected. Because of the eventrelated nature of the sample collection and the intense 

sampling at certain sites (over one-half the samples 

were collected at GRD6 and CRD7), a subset of 

samples was chosen such that each site was represented by a maximum of one snowmelt sample 

and one rainfall sample to avoid bias in the statistics. 

For sites with more than a single sample, the sample 

chosen was based on these criteria: samples with a 

complete constituent list were preferred over a more 

limited constituent list; dip samples at the culvert 

end were preferred over pumped samples; and, all 

other factors being equal, the sample with the median 

suspended-sediment concentration was selected. The 

subset of water-quality data used is listed in Appendix 

table 51. Statistical summaries of the snowmelt 

and rainfall road-runoff data are listed in Appendix 

tables 52 and 53. The data set includes 8 snowmelt 

samples from 8 different sites and 12 rainfall samples 

from 12 different sites along the Guanella Pass road. 

Onsite Measurements and Major Ions

For the snowmelt-runoff data set from the 

Guanella Pass road, specific conductance ranged 

from 14 to 301 μS/cm with a median of 38 μS/cm 

(Appendix table 52). For rainfall runoff, specificconductance ranged from 19 to 468 μS/cm with a 

median of 78 μS/cm (Appendix table 53). The pH 

ranged from 6.1 to 8.5, and only three samples of 

road runoff had pH values below 7.0. The two lowest 

values were from rainfall runoff (Appendix table 51), 

but medians for snowmelt and rainfall were the same 

(7.2, tables 52, 53). Turbidity values were generally 

greater than 1,000 NTU for all samples. Samples 

collected during rainstorms generally had larger 

turbidity values than snowmelt samples.

As in stream water, ground water, and 

lake/reservoir water, the median major-ion concentrations in road runoff were dominated by calcium and 

bicarbonate. The maximum concentrations of anions 

were dominated by chloride (Appendix tables 52 and 

53). Some samples exhibit major-ion compositions 

that indicate effects from deicing salt (NaCl) and dust 

inhibitor (MgCl2) applied to sections of the road. The 
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 85

0

WATER DISCHARGE, IN CUBIC FEET PER SECOND

0

0.06

0.01

0.02

0.03

0.04

0.05

OND J FMAM J J ASOND J FMAMJ J AS

1995 1996 1997

0

40

5

10

15

20

25

30

35

WATER DISCHARGE, IN CUBIC FEET PER SECOND

CRD7

CC2

0

10

2

4

6

8

SUSPENDED-SEDIMENT DISCHARGE, IN TONS PER DAY

1995 1996 1997

OND J FMAM J J ASOND J FMAMJ J AS

1.2

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

SUSPENDED-SEDIMENT DISCHARGE, IN TONS PER DAY

CC2

CRD7

Figure 28. Variation in daily mean water discharge at CRD7 (road-runoff site) and CC2 (the potential receiving 

stream), water years 1996–97.
86 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

road-runoff sample for site CRD1 (rain-related) and 

CRD7 (rain-related) were dominated by concentrations of magnesium and chloride. The road-runoff 

sample for site CRD5 (rain-related) was dominated by 

concentrations of magnesium/calcium and chloride. 

The road-runoff sample for site CRD6 (snow-related) 

and CRD9 (rain-related) were dominated by concentrations of sodium and chloride (Appendix table 51). 

These five samples also had the largest dissolvedsolids concentrations of all of the selected roadrunoff samples (Appendix table 51). The samples 

with predominant magnesium are from sites along 

the unpaved section of road that had been treated with 

magnesium chloride. The samples with predominant 

sodium are from sites along the paved section of 

road north of Lower Cabin Creek Reservoir that 

receives sodium chloride in traction materials in 

winter (Jim Cannedy, Clear Creek County, oral 

commun., 1997). Not all samples collected in these 

areas clearly show NaCl and MgCl2 effects. Those that 

do seem to be related to high dissolved-solids content 

and probably represent flushes of constituents previously applied to the road.

Nutrients

Nutrients (nitrogen and phosphorus compounds) 

were commonly detected at larger concentrations 

in road-runoff samples than in streamflow samples 

(Stevens and others, 1997; Stevens, 2000). Nitrite 

plus nitrate concentrations were generally larger 

than ammonia concentrations. Samples analyzed for 

dissolved nitrite plus nitrate collected during snowmelt had a median concentration of 0.095 mg/L as N, 

and concentrations ranged from 0.015 to 0.31 mg/L as 

N (Appendix table 52). Concentrations of dissolved 

nitrite plus nitrate collected during rain events were 

generally larger than in snowmelt-related samples, 

had a median concentration of 0.29 mg/L as N, 

and ranged from 0.055 to 1.2 mg/L as N (Appendix 

table 53). Samples collected for dissolved ammonia 

during snowmelt had a median concentration of 

0.036 mg/L as N, and concentrations ranged from 

0.010 to 0.080 mg/L as N (Appendix table 52). 

Rainfall-related ammonia concentrations had about the 

same median, 0.29 mg/L as N, but ranged to larger 

concentrations (maximum 0.20 mg/L as N). These 

forms of dissolved inorganic nitrogen are common 

chemical constituents in precipitation, and measured 

concentrations in rainfall-related road runoff (table 35) 

were larger than those measured in stream water 

(table 35) and similar to the concentrations in precipitation (table 4).

Dissolved ammonia plus organic nitrogen was 

infrequently detected (33 percent of snowmelt and 

29 percent of rain-related samples) with a median 

concentration of 0.036 mg/L as N in snowmelt-related 

samples (Appendix tables 52 and 53). The concentrations of total ammonia plus organic nitrogen were 

larger in rainfall-related samples than snowmeltrelated samples, ranging from less than 0.2 to 24 mg/L 

as N with a median of 3.5 mg/L as N (Appendix 

tables 52 and 53). The organic nitrogen in road runoff 

is probably related to organic material in suspended 

sediments in the road runoff.

Total phosphorus concentrations in road 

runoff were much larger than dissolved phosphorus or 

dissolved orthophosphorus concentrations. Rainfallrelated concentrations for total phosphorus were 

generally larger than snowmelt-related runoff concentrations, ranging from 0.055 to 7.2 mg/L as P with 

a median of 1.4 mg/L as P, compared to 0.024 to 

0.4 mg/L as P with a median of 0.060 mg/L as P 

for snowmelt (Appendix tables 52 and 53). Dissolved 

phosphorus and dissolved orthophosphorus median 

concentrations were 0.02 and 0.007 mg/L as P in 

snowmelt runoff samples, whereas the median concentrations were 0.01 mg/L as P in rainfall runoff samples 

(Appendix tables 52 and 53). Large total phosphorus 

concentrations with small dissolved phosphorus 

concentrations indicate that much of the phosphorus 

is associated with suspended sediment in road-runoff 

samples. Dissolved phosphorus can be readily 

adsorbed to sediment, which may account for the 

small concentrations of dissolved phosphorus in these 

samples. Only a portion of the total phosphorus is 

available to plant life (Sharpley and others, 1991; 

Parker, 1991) because much of the element is either 

associated with mineral grains of low solubility or is 

strongly sorbed to sediment.

A pumping sampler was used to collect some 

water-quality samples. Because power was not available, these samples were not refrigerated at the time 

of collection, and nutrient data need to be interpreted 

with caution because the concentrations could be 

affected and reactions between sediment and water 

could have occurred in the bottle.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 87

Trace Elements

The trace elements in largest concentrations in 

road-runoff samples were aluminum, iron, and manganese (Appendix table 51). Other trace elements with 

median concentrations greater than the laboratory 

reporting limit were total recoverable and dissolved 

barium, total recoverable cadmium (rainfall only), 

total recoverable chromium, total recoverable cobalt, 

total recoverable and dissolved copper, total recoverable lead, total recoverable mercury (rainfall only), 

total and dissolved molybdenum (rainfall only), total 

recoverable nickel, and total recoverable and dissolved 

zinc. Total recoverable arsenic, dissolved chromium 

(rainfall only), dissolved nickel, total recoverable 

selenium, and dissolved uranium (rainfall only) 

were detected but did not have median concentrations 

greater than the laboratory reporting limit (Appendix 

tables 52 and 53). In general, rainfall-related concentrations were larger than snowmelt concentrations.

Analytical results of water samples from runoff 

from the Guanella Pass road indicate that total recoverable trace-element concentrations were substantially 

larger (by several times) than dissolved trace-element 

concentrations (Appendix table 51), indicating that 

most trace elements are in the suspended phase. The 

particulate trace elements are components of the 

rock and soil composing the roadbed, ditches, and 

cutslopes. Vehicle emissions and wear products (brake 

linings, tires, vehicle body, fluids) also contribute to 

trace elements (such as cadmium, copper, iron, lead, 

manganese, nickel, and zinc) available on the road for 

erosion (Young and others, 1996).

Organic Carbon and Trace-Organic Constituents

Dissolved organic-carbon concentrations in road 

runoff ranged from 2.3 to 3.8 mg/L (tables 35, 52, and 

53). Total organic carbon in snowmelt runoff samples 

had a median concentration of 9.4 mg/L and a range in 

concentrations of 4.7 to 16 mg/L. Rainstorm runoff 

concentrations ranged from 5.6 to 150 mg/L, with a 

median of 94 mg/L (tables 35, 52, and 53). The large 

total organic-carbon concentrations in a few samples 

are probably related to plant detrital material. Two 

road-runoff samples collected during snowmelt and 

analyzed for trace-organic substances (organic chemicals normally present in small concentrations in the 

environment) had no detections of volatile or semivolatile organic substances greater than the laboratory 

reporting limits (Stevens and others, 1997).

Suspended Sediment and Particle Size

Suspended-sediment concentrations in snowmelt road runoff ranged from 66 to 7,360 mg/L, with 

a median concentration of 1,510 mg/L (Appendix 

table 52). Rainstorm-runoff concentrations were 

generally larger than those in snowmelt runoff and 

ranged from 34 to 38,800 mg/L, with a median of 

7,190 mg/L (Appendix table 53). The sediment was 

primarily fine grained. More than 90 percent of 

suspended sediments from snowmelt samples and 

88 percent from rainstorm samples were finer than 

0.062 mm. This fine-grained character facilitates 

transport of the sediment and diminishes the likelihood that settling or deposition of the sediments would 

occur prior to reaching a stream. Fine sediment usually 

contains a larger proportion than coarse sediment 

of trace elements, nutrients, and oxygen-consuming 

substances (Horowitz, 1995), which can degrade water 

quality. Suspended sediments that subsequently settle 

out in streams can contribute to the reduction of suitable fish-spawning areas and filling of pool habitat 

(MacDonald and others, 1991). The fine-grained character of the road-related sediment, however, might 

indicate that high flows could easily resuspend the 

sediment deposited during lower flows.

Sources and Transport of Sediment in 

Road Runoff

Information about source areas and depositional 

areas of sediment, road-runoff linkages to receiving 

waters, and seasonal transport characteristics is helpful 

for understanding sediment transport related to road 

runoff.

Sources and Deposits of Sediment

Natural sources of sediment to streams in 

montane or alpine locations are primarily streambed 

and streambank erosion (Leaf, 1996) because overland 

flow, which could erode and transport sediment from 

the nonchannel sources, is rare in the natural setting. 

Sediment sources include intermittent and ephemeral 

channels that may contribute only during runoff 

periods. In some areas, mass wasting processes (such 

as landslides or soil creep) are important sources 

(Luce, 1995). 
88 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

With the introduction of roads into mountainous areas, sediment may be introduced to streams 

by cutslopes, fillslopes, the road surface, and ditches 

(fig. 27). Many of the road cuts on the existing 

Guanella Pass road either have failed to revegetate 

naturally or support only marginal amounts of vegetation. When the road was originally constructed, many 

of the road cuts into the hillside were overly steep and 

are eroding into the hillslope. Soil materials slide or 

are washed downslope by rainfall and snowmelt. In 

some areas, road maintenance has removed vegetation 

and coarse materials at the toe of the cuts, which 

causes cutslope instability. 

Cutslope instability may be related to the character of soils and can increase sediment supply to road 

runoff. The low-cohesion soils on the south side of 

Guanella Pass in the Duck Lake area contribute to 

cutslope instability and inhibit revegetation of the 

slopes. In dry weather, sandy slope material exposed 

to the weather was observed to be eroded by wind. The 

eroded slope material generally accumulates in the 

roadside ditch. During snowmelt and rainstorms, large 

boulders eroding out of the slopes were observed on 

the roadway in several areas (fig. 29). Evidence of 

large landslides near the road, however, was not 

observed.

Although moderate erosion occurs along 

the entire road, the most extreme examples are associated with the steepest cutslopes. Cutslope erosion 

was observed as rilled, sparsely vegetated areas in 

the switchback areas just above Georgetown, the 

switchbacks below Green Lake (fig. 30), the switchbacks along South Clear Creek above Naylor Creek 

(fig. 31), much of the section of the road from the top 

of Guanella Pass to the beginning of the paved section 

below the Geneva Basin Ski area, and the Falls Hill 

section (fig. 32). These areas are potentially large 

sources of sediment to road runoff.

Fillslopes on the Guanella Pass road generally 

do not seem to concentrate runoff enough to transport 

sediment to streams. Rilling of the fillslopes is limited 

by vegetation and coarse slope material in much of the 

area. However, where Geneva Creek closely follows 

the Guanella Pass road from near Grant to Threemile 

Creek, high flows are concentrated directly on sidecast material and the fillslope, and those materials are 

eroded by and transported in Geneva Creek (fig. 33). 

Sidecast material is replenished after repair and 

regrading of the road (fig. 34). Concentrated runoff 

from culvert outflows (fig. 35) and flow concentrated 

at the outside edge of the road prism by windrows of 

plowed material from grading also were observed to 

cause erosion of fillslope material.

During many storms and during the snowmelt 

period on the road, the road surface was observed to be 

disturbed by vehicle tires (fig. 36). Flow in ruts and 

overland flow on the road surface was observed to 

erode material off the road and transport sediment to 

the roadside ditches. Damage to the road surface was 

evident in some areas but generally did not concentrate flow enough to transport the sediment far 

into the buffer zone below the road.

Figure 29. Boulders eroded from cutslope on Guanella Pass road near 

disused ski area, May 1996.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 89

Figure 30. Cutslope just north of Green Lake along Guanella Pass 

road, May 1994.

Figure 31. Cutslope along Guanella Pass road 

in the switchback road segment above Naylor 

Creek north of Guanella Pass, July 1995.
90 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Figure 32. Cutslope along Guanella Pass road in the Falls Hill segment 

just north of the Scott Gomer Creek crossing, January 1994.

Figure 33. Erosion of fillslope and side-cast material by Geneva Creek, 

high streamflow, June 1995.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 91

Figure 34. Appearance of fillslope at low streamflow in Geneva Creek 

after repair and regrading of road, August 1995.

Figure 35. Culvert outflow concentrating road runoff onto the fillslope in 

the switchback road segment above South Clear Creek, upstream from 

Naylor Creek, July 1995.
92 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Ditches that channel runoff on the shoulder of 

the road were eroded in some areas, mobilizing sediment that was transported by road runoff (fig. 37). 

Ditch erosion was often observed during snowmelt 

on the road when clogged ditches and culverts caused 

alternative flow paths for road runoff. Repairs to 

ditches were made by grading, which can loosen and 

replenish the loose sediment on the ditch bottom that 

can be eroded during subsequent runoff.

Sediment can be trapped in the buffer zone 

between the road and a potential receiving stream 

by physical obstructions, vegetation, or changes in 

slope. The buffer zone sometimes reduces transport of 

sediment in road runoff by promoting sedimentation or 

allowing infiltration of the water fraction. The deposited sediment sometimes buries the buffer-zone flora. 

Two small but extreme examples of this type 

of deposit were observed. One is in the switchback 

road segment along South Clear Creek upstream from 

Naylor Creek where flow from a culvert eroded an 

area approximately 150 ft long, up to 15 ft wide, and 

10 ft deep in colluvium on the slope (fig. 38). The 

eroded material was deposited as an alluvial fan at the 

base of the slope in a wetland area (fig. 39). Another 

area receiving large amounts of sediment is located 

approximately 1 mile south of Guanella Pass. A 

culvert discharges sediment onto an area of willows 

and tundra vegetation. The deposit of sand and gravel 

is approximately 10 to 50 ft wide and extends about 

200 ft down the slope. Low tundra vegetation is 

covered (fig. 40), and even willows do not grow on the 

thickest part of the deposit. There was no evidence, 

however, that eroded sediment had reached the stream.

Fine-sediment deposits on streambeds were 

observed in only a few areas. In general, the stream 

gradient in the area is steep, which maintains velocities sufficient to keep finer grain sizes in suspension. 

Beaver ponds, pools created by large woody debris, 

lakes, and reservoirs trap some of the large grain-size 

particles. The beaver ponds in the active channel of 

South Clear Creek downstream from Naylor Creek 

show some signs of filling by sediment. One large 

pond is completely full of sediment and was abandoned by the beaver (fig. 41). The sediment is 

eventually released downstream when the structural 

components of the dam begin to decay and the stream 

erodes through the previously deposited material. 

Along South Clear Creek many ponds in the active 

channel have been filled and sediments behind the 

dam are eroding and being transported downstream 

(fig. 42). The sediments could move downstream, 

potentially settling in the next pond downstream. The 

revegetation of the ponded sediments is too slow a 

process, once the dam is breached, to prevent the accumulated sediments from being eroded. If the channel 

shifts away from a dam and does not destroy it, or if 

the dam is off the main channel, vegetation may eventually stabilize the sediments.

Figure 36. Rutting and erosion of the road surface just south of Naylor 

Creek. 
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 93

Alluvial fans at the stream inlets to lakes or 

reservoirs were only conspicuous in one area. Where 

South Clear Creek enters Georgetown Reservoir 

upstream from Georgetown, a large delta has accumulated material ranging in size from sand to cobble-sized 

material (fig. 43). The rate of accumulation is not 

known, but the deposit could eventually disrupt the 

operation of the reservoir for diversion of water to the 

powerplant and water-treatment plant in Georgetown. 

When the reservoir is drained for maintenance, accumulated sediments could be eroded and released to 

South Clear Creek downstream from the impoundment. 

The likely source of the sediments is Leavenworth 

Creek because the other tributary stream, South Clear 

Creek, is located downstream from Lower Cabin Creek 

Reservoir and Clear Lake, which probably trap much of 

the sediment from the upper part of the basin.

A possible source of the accumulated material 

in Georgetown Reservoir is a large mine dump that 

shows evidence of erosion where Leavenworth 

Creek passes underneath the Guanella Pass road. 

In addition, high, eroding stream cutbanks, which 

are composed of mine waste materials, contribute 

sediment to Leavenworth Creek in many areas 

between the Guanella Pass road and the confluence 

of Leavenworth Creek with South Clear Creek 

(fig. 44). 

Road Drainage and Stream Linkage

One of the ways that road runoff can enter 

streams is by surface flow from culvert and roadsideditch drainage, which is referred to as a linkage in the 

following discussion. The concentrated flow in these 

drainage features can cross the buffer zone between 

a road and a stream or lake, contributing water-quality 

constituents and sediment. Evaluations of roaddrainage features and their interaction with the 

buffer zone are described in Bilby and others (1989); 

Ohlander (1994); Snyder (1996); and Wemple and 

others (1996). 

Figure 38. Eroded road-runoff channel about 

200 feet below the Guanella Pass road, located 

in the switchback road segment south of Naylor 

Creek, August 1996.

Figure 37. Ditch erosion in the switchback 

road segment, south of Naylor Creek, 

August 1998.
94 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Figure 39. Alluvial fan of material eroded from a channel cut by road 

runoff on the slope above South Clear Creek upstream from Naylor 

Creek, August 1996.

Figure 40. Deposit of road-runoff sediment 

covering tundra vegetation just north of Duck 

Lake, near the summit of Guanella Pass, 

July 1995.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 95

Figure 41. Abandoned beaver pond filled with sediment on South Clear 

Creek upstream from Lower Cabin Creek Reservoir, June 1996.

Figure 42. Sediments behind beaver dam (shown in figure 41) that is 

being eroded by South Clear Creek, June 1998.
96 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Whether or not cross-drain culvert and 

roadside-ditch drainage reached streams was determined for the existing Guanella Pass road (1997) by 

walking each culvert or roadside-ditch outflow until 

the deposition point or receiving water was located 

(Appendix table 54). If evidence that the runoff 

from the drainage feature such as sediment or a 

channel leading to the stream or lake edge was 

found, a linkage was noted in Appendix table 54. 

Other descriptive information also was noted, 

such as contributing ditch length, buffer-zone vegetation, buffer-zone sediment grain size, buffer-zone 

topography, buffer-zone drainage-channel characteristics, obstructions, sediment travel distance, 

largest grain-size transported to stream, and the 

receiving stream name. The location of drainage 

features and their linkage to receiving waters are 

shown in figure 45.

Figure 43. Alluvial fan at the inlet of South Clear Creek to Georgetown 

Reservoir, just downstream from the confluence with Leavenworth 

Creek, September 1995.

Figure 44. Cutbank in mine waste along Leavenworth Creek between 

Guanella Pass road and the confluence with South Clear Creek, 

August 1995.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 97

0 1/2 1 MILE

105°42'56"

105°42'56"

105°39'31"

39°30'31"

105°39'31"

39°27'14" 39°27'14"

39°30'31"

GCD74 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that flows into a stream or lake GCD73 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that does not flow into a stream or lake

EXPLANATION

Figure 45. Location and identification of drainage features (roadside ditches and culverts) that showed evidence of sediment 

reaching a stream.
98 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

0 1 MILE 1/2

105°44'50"

105°44'50" 39°33'46" 105°41'26" 39°33'46"

39°30'30" 39°30'30"

105°41'26"

GCD40 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that flows into a stream or lake GCD41 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that does not flow into a stream or lake

EXPLANATION

Figure 45. Location and identification of drainage features (roadside ditches and culverts) that showed evidence of sediment 

reaching a stream—Continued.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 99

0 1/2 1 MILE

105°44'19" 105°40'54"

105°40'54"

39°36'54" 39°36'54"

105°44'19" 39°33'38" 39°33'38"

GCD16 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that flows into a stream or lake GCD14 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that does not flow into a stream or lake

EXPLANATION

Figure 45. Location and identification of drainage features (roadside ditches and culverts) that showed evidence of sediment 

reaching a stream—Continued.
100 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

0 1/2 1 MILE

105°44'19"

39°36'35"

105°40'54"

39°36'35"

105°40'54" 39°39'52" 105°44'19" 39°39'52"

CCD19 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that flows into a stream or lake CCD20 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that does not flow into a stream or lake

EXPLANATION

Figure 45. Location and identification of drainage features (roadside ditches and culverts) that showed evidence of sediment 

reaching a stream—Continued.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 101

0 1/2 1 MILE

105°43'23" 39°39'22" 105°39'58" 39°39'22"

105°39'58" 39°42'39" 105°43'23" 39°42'39"

CCD40 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that flows into a stream or lake CCD49 Location and site number (table 54) of drainage feature

 (culvert of roadside ditch) that does not flow into a stream or lake

EXPLANATION

Figure 45. Location and identification of drainage features (roadside ditches and culverts) that showed evidence of sediment 

reaching a stream—Continued.
102 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

A total of 137 drainage features were located 

and described over the approximately 23.5 miles 

of the existing Guanella Pass road, 63 in the South 

Clear Creek drainage and 74 in the Geneva Creek 

drainage (Appendix table 54). Culverts accounted for 

67 percent of the drainage features on the South Clear 

Creek side and 84 percent on the Geneva Creek side of 

Guanella Pass. Fifty-six percent of the total number 

of drainage features had direct connection to the 

stream during a past runoff event. In the South Clear 

Creek drainage, 75 percent of the drainage features 

had a direct connection, and 40 percent in the Geneva 

Creek drainage had a direct connection (Appendix 

table 54).

Road-drainage density in selected study-area 

basins were computed to indicate relative effects 

of the Guanella Pass road. The estimate was enhanced 

by using the length of ditch with a direct connection to 

the stream in the basin instead of the road length. This 

was estimated by computing the length of linked road 

ditch per square mile of drainage area upstream from 

the sampling site (table 32). Sites with the highest 

road-drainage density might be most affected by the 

present road and would probably be most affected 

by any reconstruction activities. In the Leavenworth 

Creek and upper Geneva Creek Basins (CC9 and 

GC11), secondary roads also could have the same 

potential effects as the Guanella Pass road, but their 

road-runoff linkages were not determined. Even 

if all the secondary road segments in the GC11 basin 

were connected to streams, the large drainage-basin 

area would result in a relatively small road-drainage 

density. But for CC9, secondary road-drainage 

connections have the potential of relatively large 

road-drainage density. Of the selected sampling sites, 

CC9 had the smallest road-drainage density from the 

Guanella Pass road (94 ft/mi2

), CC12 (South Clear 

Creek at upper station, above Naylor Creek) had the 

largest (3,126 ft/mi2

). In general, the smallest headwater drainage basins had the largest connected roaddrainage densities. The large road-drainage density, 

combined with larger annual precipitation, indicate 

that the greatest effects of Guanella Pass road reconstruction on road runoff could occur in headwater 

basins.

Surface-runoff connections between the road 

drainage features and receiving waters depend upon 

the effectiveness of the buffer zone to attenuate runoff. 

The average sediment travel distance into the buffer 

zone of the road runoff that was stopped by the vegetative buffer (excluding blocked culverts) was 184 ft 

but ranged from less than 5 to 1,295 ft (Appendix 

table 54). The average travel distance of the road 

runoff that was not stopped by the buffer (distance 

from road to the point of entry in a stream or lake) 

also was 184 ft and ranged from 0 to 990 ft (Appendix 

table 54). These distances are for a single drainage 

feature and do not include flows from one feature to 

another.

Seasonal Characteristics of Sediment 

and Dissolved Solids in Road Runoff

To understand the seasonal characteristics 

of road runoff, four sites were instrumented with 

continuous water-stage recorders and automatic 

pumping samplers (Stevens, 2000). Three of the 

sites produced only partial water-discharge and 

suspended-sediment sample record (GRD4, GRD6, 

and CRD8) because of instrument malfunction. 

Water and suspended-sediment discharge record for 

site CRD7 was complete for the runoff seasons of 

WY’s 1996 and 1997. Characteristics of the four 

runoff monitoring sites are listed in table 33. Data 

and methods of sample collection at these sites are 

presented in Stevens (2000).

By using sediment and dissolved-solids budgets 

for the culvert-monitoring site CRD7 and the small 

watershed upstream from CC2 (South Clear Creek 

above Naylor Creek), which includes the CRD7 

segment, the influence of road runoff on a headwater basin was evaluated. Three comparisons were 

made: (1) the estimated annual road-runoff sediment 

discharge in the CC2 basin was compared to the estimated annual suspended-sediment discharge at CC2; 

(2) the daily sediment discharges from road runoff 

were compared to daily suspended-sediment 

discharges at CC2 and expressed as a percentage 

(tables 55 and 56); and (3) the potential increase 

in suspended-sediment concentration at CC2 due 

to road runoff was determined by computing a concentration of suspended sediment from the road-runoff 

sediment discharge and the water discharge at CC2 

(tables 55 and 56). The same comparisons were made 

for dissolved solids. Assumptions for the budgets are 

the following: (1) the length of Guanella Pass road in 

the watershed upstream from CC2 had a similar yield 

of sediment and dissolved solids per foot of road 

ditch (estimated from the yield per foot of road ditch 
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 103

draining to CRD7); and (2) the entire daily yield of 

sediment and dissolved solids from road ditches linked 

to the stream was transported to the stream instantaneously and then to CC2 without any loss of mass.

Because only suspended sediment was 

measured at CC2 and equipment used to sample 

suspended sediment is not able to collect large grain 

sizes, the coarse sediment fraction (sediment trapped 

behind the weir at CRD7) from the road-runoff budget 

was not included in the sediment-discharge computations. This is probably a reasonable assumption 

because coarse material is less likely to be transported 

to the stream and more likely to be deposited in the 

buffer zone. Duncan and others (1987) measured sediment delivery through an ephemeral headwater stream 

segment in a forested area of Washington and found 

that 40 to 100 percent of sediment less than 0.063 mm 

was transported downstream whereas less than 10 to 

40 percent of sediment between 0.063 and 2 mm was 

transported. Particle-size data for sediment samples 

collected at the CRD7 weir indicate a predominance 

of the less than 0.062-mm fraction (average 91 percent 

of total). Particle-size data for bulk sediment trapped 

in the box at site CRD7 indicate almost no sediment 

less than 0.062 mm (percentage finer than 0.062 mm 

averaged 3.6) (Stevens and others, 1997; Stevens, 

2000). The data indicate that most of the sediment 

transported past the weir at CRD7 is less than 

0.062 mm, and very little of the sediment less than 

0.062 mm is trapped.

Table 33. Characteristics of road-runoff monitoring sites

[ft, feet]

Site

number

(fig. 2)

Length

of road

segment

(ft)

Average

road

width

(ft)

Average

cutslope

width

(ft)

Average

fillslope

width

(ft)

Average

cutslope

slope

(degrees)

Culvert

diameter

(ft)

Soil type

on cutslope

Vegetation

on cutslope

CRD7 565 24 29 26 30 1.25 decayed, granitic gravel and 

soil

sparse grasses, 

moss

GRD6 1,416 26 30 43 29 1.25 sandy, loose, decayed granite 

and rock fragments

sparse grasses

GRD4 1,134 21 18 18 20 1.5 gravelly soil with rock 

fragments

grass; some 

aspen/conifer

CRD8 754 28 27 49 35 no culvert soil, some gravel and rock 

fragments

grasses; some 

conifer

Table 32. Road-runoff linkages and road-drainage density in basins of selected stream-sampling sites

[ft, feet; mi2, square miles; roadside ditch drainage density was computed by dividing the length of roadside ditch directly connected to the stream by the 

basin drainage area contributing to flow at the stream site]

Site

(fig. 1)

Altitude

(ft)

Sampling site

drainage area

(mi2)

Total roadside

ditch length

 (ft)

Total stream-linked

roadside ditch 

length

(ft)

Percentage

stream-linked

roadside ditch

Roadside ditch

drainage density

(ft/mi2)

CC12 11,030 1.45 6,009 4,533 75 3,126

CC2 10,710 2.19 7,459 5,983 80 2,732

CC5 10,100 11.8 18,525 13,992 76 1,186

CC9 9,280 12.0 1,404a 1,129a 80 94a

GC2 11,160 .79 4,631 1,416 31 1,792

GC5 9,750 7.78 22,782 10,112 44 1,300

GC11 8,760 74.6 52,859a 26,647a 50 357a

 aComputations include only Guanella Pass Road. Extensive secondary roads are present in CC9 (about 12.6 mi) and GC11 (about 8.6 mi).
104 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Sediment

The CRD7 water and sediment-discharge 

results for water years 1996–97 are listed in table 34. 

In water year 1996, about 0.41 acre-ft of runoff 

was produced from the approximately 0.69 acre of 

cutslope and road surface (380 acre-ft/mi2

); about 

96 percent of runoff occurred during snowmelt. Total 

sediment yield measured at the culvert was about 

0.61 ton (566 tons/mi2, 1.49 tons/acre-ft), 56 percent 

during snowmelt. The flow-weighted-mean concentrations of the total sediment load were 639 mg/L for 

snowmelt and 11,770 mg/L for rainstorm runoff.

In water year 1997, about 0.66 acre-ft of runoff 

was produced from the approximately 0.69 acre of 

cutslope and road surface (612 acre-ft/mi2

), about 

77 percent during snowmelt. Total sediment yield 

measured at the culvert was about 4.74 tons 

(4,400 tons/mi2

, 7.18 tons/acre-ft), 24 percent during 

snowmelt. The flow-weighted-mean concentrations of 

the total sediment load were 1,635 mg/L for snowmelt 

and 17,540 mg/L for rainstorm runoff (table 34). 

Annual estimates of the sediment budget 

for the road length connected to South Clear Creek 

upstream from Naylor Creek by surface drainage 

(a road segment similar in character to the CRD7 

segment) (fig. 46) were computed and compared to the 

suspended-sediment discharge at CC2. On an annual 

basis, although the road-runoff water yields (CRD7 

culvert yield multiplied by a factor of 10.6) were only 

about 0.35 percent (1996) and 0.44 percent (1997) of 

the water yield at CC2 (tables 5 and 34), the road 

runoff total sediment yield (CRD7 culvert yield multiplied by a factor of 10.6) was 29 percent (1996) and 

49 percent (1997) of the annual suspended-sediment 

load at CC2 (tables 17 and 34). 

On a daily basis, suspended-sediment loads from 

road runoff in the CC2 basin also were compared to 

CC2 watershed suspended-sediment loads to estimate 

the potential effect on stream concentrations and to 

test the sediment budget assumptions (Appendix 

tables 55–56). Comparison of the daily suspendedsediment discharges attributed to the roads in the 

CC2 basin to the estimated daily suspended-sediment 

discharges at CC2 sometimes resulted in percentages 

greater than 100 percent, which implies that more roadsediment transport was estimated than was actually 

measured at CC2 (Appendix tables 55 and 56). This 

discrepancy might be attributed to the following: 

(1) a lack of similarity between CRD7 and the larger 

road segment; (2) sediment erosion on the buffer-zone 

slope; (3) erosion on the South Clear Creek streambed 

or streambanks; or (4) inaccuracies in suspendedsediment transport estimates for the road runoff 

and the stream. 

The analysis, however, does indicate that road 

runoff was seasonal, occurring during snowmelt and 

rainstorms. Runoff from the road preceded the basinwide peak flow from snowmelt, resulting in sediment 

and water-quality constituent inputs to the stream 

when the capacity for dilution was low. In late 

summer, peak flows in streams had subsided and short 

thunderstorms caused road runoff to enter streams 

when capacity for dilution was again low. This may 

have resulted in larger concentrations of suspended 

sediment in receiving water or deposition of material 

on the streambed.

During snowmelt in 1996 (04–25–96 through 

05–31–96), road-runoff sediment discharge had the 

potential to cause suspended-sediment concentration 

increases in South Clear Creek upstream from CC2 

ranging from less than 1 to 43 mg/L, which equates 

Table 34. Water discharge, sediment transport, and dissolved-solids transport at site CRD7, water years 1996–97

[Flow-weighted-mean concentration = annual sediment discharge (in tons/day) divided by annual mean water discharge (in ft3/s) divided by 0.0027]

Water

year

Water discharge

(acre-feet)

Sediment transported

over the weir

(tons)

Sediment in

coarse-particle trap

(tons)

Flow-weightedmean sediment

concentration1

(milligrams per liter)

Dissolved solids

(tons)

Snowmelt Rainstorm

runoff Snowmelt Rainstorm

runoff Snowmelt Rainstorm 

runoff Snowmelt Rainstorm 

runoff Snowmelt Rainstorm 

runoff

1996 0.39 0.017 0.172 0.207 0.17 0.06 639 11,770 0.015 0.003

1997 .51 .15 .567 1.98 .57 1.62 1,635 17,540 .012 .050

1

Flow-weighted-mean sediment concentration includes both sediment transported over the weir and sediment collected in the coarse-particle trap.
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 105

to 0.7 to more than 3,600 percent of the suspendedsediment discharges actually estimated at CC2 

(table 55). Snowmelt road runoff during 1997 

(05–08–97 through 06–02–97) in the CC2 basin had 

the potential to cause suspended-sediment concentration increases ranging from less than 1 to 50 mg/L, 

which equates to less than 1 to 86 percent of the 

suspended-sediment discharges estimated at CC2 

(table 56). During rainstorms in 1996, road-runoff sediment discharge had the potential to cause suspendedsediment concentration increases in South Clear Creek 

upstream from CC2 ranging from 2 to 450 mg/L, which 

equates to 32 to 650 percent of the discharges estimated 

at CC2 (table 55). Rainstorm road runoff during 1997 in 

EXPLANATION

Road-drainage segment

Sampling sites

Culvert monitoring

site

Guanella

Pass

Road

Naylor Creek

0 1/2 1 MILE

0 0.5 1 KILOMETER

Short road

segment

Long road segment

COLORADO

LOCATION MAP

N

CC1

CC1

CC2

CRD7

South Clear Creek

Figure 46. Location of culvert monitoring site and the segment of the road draining to the monitoring 

site (short segment), and the location of the segment of road draining to South Clear Creek 

upstream from the CC2 sampling site.
106 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

the CC2 basin had the potential to cause suspendedsediment concentration increases ranging from less than 

1 mg/L to 2,330 mg/L, and the percentage difference of 

CRD7 to CC2 suspended-sediment discharge ranged 

from 1 to 11,400 percent (table 56).

Dissolved Solids

The CRD7 water discharge and dissolvedsolids discharge results for WY’s 1996–97 are listed 

in table 34. Dissolved-solids discharge in runoff for 

water year 1996 was about 0.018 ton, about 83 percent 

transported in snowmelt. Dissolved solids in runoff for 

WY 1997 was about 0.062 ton, about 19 percent transported in snowmelt. 

Annual estimates of the dissolved-solids budget 

produced by the road length observed to be connected 

to South Clear Creek above Naylor Creek by surface 

drainage (fig. 46) were computed and compared to the 

dissolved-solids budget at CC2. On an annual basis, 

dissolved-solids discharges produced by road runoff 

draining to CC2 (CRD7 culvert yield multiplied by a 

factor of 10.6) were 0.3 (1996) and 0.7 percent (1997) 

of the dissolved-solids load estimated at CC2. 

On a daily basis, dissolved-solids discharges 

from roads in the CC2 basin were compared to CC2 

watershed dissolved-solids discharges to estimate the 

potential effect on stream concentrations. Potential 

increases in dissolved-solids concentration in South 

Clear Creek above Naylor Creek as a result of road 

runoff were small (Appendix tables 57 and 58). 

During snowmelt in 1996, road runoff to South Clear 

Creek (CC2) had the potential to cause dissolvedsolids concentration increases ranging from less than 

1 to 12 mg/L, which equates to less than 1 to about 

16 percent of the estimated discharges at CC2 

(Appendix table 57). Snowmelt road runoff during 

1997 in the CC2 basin had the potential to cause 

dissolved-solids concentration increases ranging from 

less than 1 to about 1 mg/L, which equates to less than 

1 to 2.4 percent of the estimated discharges at CC2 

(Appendix table 58). During rainstorm road runoff in 

1996, connected road-runoff contributions to South 

Clear Creek had the potential to cause dissolved-solids 

concentration increases ranging from less than 1 to 

4 mg/L, which equates to less than 1 to 4.8 percent of 

the estimated discharges at CC2 (Appendix table 57). 

Rainstorm road-runoff during 1997 had the potential 

to cause dissolved-solids concentration increases 

ranging from less than 1 to 13 mg/L, which equates 

to less than 1 to about 24 percent of the estimated 

discharges at CC2 (Appendix table 58). 

Although concentrations of dissolved solids 

in road runoff were sometimes larger than were 

measured at CC2, dilution decreases the likelihood 

of substantial increases in daily mean dissolved-solids 

concentration at CC2. Because this road segment has 

been treated with magnesium chloride, these estimates 

might be larger than those expected for a road not 

treated with the dust inhibitor.

Potential Effects of Road Runoff 

on Receiving Water

Receiving waters are the streams, ground water, 

and lakes and reservoirs into which road runoff flows. 

If road runoff flows into receiving waters in sufficient 

amounts, the effect could be an alteration of water 

quality. By comparing the chemistry of the road runoff 

to the chemistry of the receiving water, the potential 

effects of road runoff on the receiving water can be 

qualitatively evaluated. 

Streams

The median concentrations for many 

constituents are larger in road runoff than in nearby 

streams, indicating that road runoff may increase 

stream concentrations (table 35). When compared 

to streams (Appendix tables 36–49), road runoff 

(Appendix tables 52 and 53) generally has larger 

median values of turbidity and larger median concentrations of sodium, chloride, dissolved nitrite plus 

nitrate, dissolved ammonia, total ammonia plus 

organic nitrogen, total phosphorus, dissolved phosphorus, total recoverable and dissolved aluminum, 

total recoverable barium, total recoverable chromium, 

total recoverable cobalt, total recoverable copper, 

total recoverable iron, total recoverable lead, total 

recoverable and dissolved manganese, total recoverable nickel, total recoverable zinc, total organic 

carbon, and suspended sediment. For these constituents, the median road-runoff values and concentrations 

range from 72 percent larger than stream values and 

concentrations for sodium (table 35) to more than 

700 times larger for suspended sediment (table 35 

and fig. 47).

Road runoff occurs during early spring from 

melting snow (often beginning before peak flow in 

streams) and during summer from afternoon and 

evening thunderstorms. Early snowmelt and thunderstorms often occur when streamflows are low 
C

HARACTERIZATIONOFGUANELLAPASSROADRUNOFF107

Table 35. Summary of stream and road-runoff water quality, water years 1995–97[--, insufficient data to calculate statistic; ranges of site data computed from all stream-water-quality sites; stream median statistic is the median of all individual site medthe Appendix; **, 1995 data at higher detection limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbmilligrams per liter; <, less than; μg/L, micrograms per liter; %, percentage; mm, millimeters; T/d, tons per day]

Consituent or property Units

Streams

Road runoff

Rainstorm-related Snowmelt-rela

Minimum Median Maximum Minimum Median Maximum Minimum Median 

Specific conductance, at 25 degrees Celsius μS/cm 23 44 210 19 78 468 14 38 pH units 3.8 7.6 8.8 6.1 7.2 8.5 6.9 7.2 Turbidity NTU .2 2.2 2,140 79 >1,000 >1,000 430 >1,000 Dissolved oxygen mg/L 6.7 8.8 11.6 -- -- -- 6.7 9.4 Hardness, as CaCO3 mg/L 9 18 89 1 17 160 5 15 Calcium, dissolved mg/L 2.6 5 16 .2 5.2 20 1.5 3.4 Magnesium, dissolved mg/L .6 1.2 12 .06 .9 26 .2 1.6 Sodium, dissolved mg/L .7 1.4 5.6 .2 2.6 33 .5 1.4 Potassium, dissolved mg/L .2 .6 2.0 .5 2.8 5.6 .6 1.2 Acid-neutralizing capacity, lab, as CaCO3 mg/L <.1 16 61 5.4 22 59 4.8 14 Sulfate mg/L .8 3.3 90 .4 2.4 16 .4 1.2 Chloride mg/L <.1 .3 36 .4 2.8 120 .6 4.2 Fluoride mg/L <.1 .2 .4 <.1 .2 .4 <.1 .1 Silica mg/L 4.1 6.8 13 .8 2.2 8.7 .6 3.2 Dissolved solids, residue at 180°C mg/L 10 40 128 11 64 286 34 39 Nitrogen, nitrite, dissolved as N mg/L <.01 -- .01 <.01 .01 .06 <.01 <.01 Nitrogen, nitrite plus nitrate, dissolved as N** mg/L .005 .059 .22 .055 .29 1.2 .015 .095 Nitrogen, ammonia, dissolved as N** mg/L <.002 <.002 .036 <.002 .040 .20 .010 .036 Nitrogen, ammonia plus organic, dissolved as N mg/L <.2 -- .3 <.2 <.2 .9 <.2 <.2 Nitrogen, ammonia plus organic, total as N mg/L <.2 <.2 4.3 .3 3.5 24 <.2 .3 Phosphorus, total as P mg/L <.001 .009 3.2 .055 1.4 7.2 .024 .060 Phosphorus, dissolved as P mg/L <.01 -- .04 <.01 .01 .25 <.01 .02 Phosphorus, dissolved orthophosphate as P mg/L <.001 .001 .020 .003 .010 .22 .003 .007 Aluminum, total recoverable as Al μg/L 20 -- 11,000 41,000 50,000 130,000 550 14,000 Aluminum, dissolved as Al μg/L 4 -- 4,700 30 140 280 50 150 Antimony, dissolved as Sb μg/L <1 -- <1 <1 <1 <1 <1 <1 Arsenic, total recoverable as As μg/L <1 -- <1 <1 <1 2 <1 <1 Barium, total recoverable as Ba μg/L <100 -- <100 700 1,800 2,600 100 200 Barium, dissolved as Ba μg/L 16 -- 38 9 20 48 7 16 Beryllium, total recoverable as Be μg/L <10 -- <10 <10 <10 <10 <10 <10 
108 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L <1 -- <1 <1 <1 <1 <1 <1 

Cadmium, total recoverable as Cd μg/L <1 -- 2 <1 2 7 <1 <1 

Cadmium, dissolved as Cd μg/L <1 -- 2 <1 <1 <1 <1 <1 

Chromium, total recoverable as Cr μg/L <1 -- 20 89 120 200 <1 22 

Chromium, dissolved as Cr μg/L <1 -- 2 <1 <1 <1 <1 <1 

Cobalt, total recoverable as Co μg/L <1 -- 10 20 80 110 <1 10 

Cobalt, dissolved as Co μg/L <1 -- 8 <1 <1 <1 <1 <1 

Copper, total recoverable as Cu μg/L <1 <1 92 6 74 600 <1 31 

Copper, dissolved as Cu μg/L <1 <1 37 <1 2 3 <1 1 

Iron, total recoverable as Fe μg/L 10 460 110,000 3,000 110,000 580,000 780 45,000 

Iron, dissolved as Fe μg/L <3 104 1,800 17 63 520 46 220 

Lead, total recoverable as Pb μg/L <1 <1 71 14 220 1,200 2 16 

Lead, dissolved as Pb μg/L <1 <1 2 <1 <1 <1 <1 <1 

Manganese, total recoverable as Mn μg/L <10 20 2,300 44 3,900 30,000 60 910 

Manganese, dissolved as Mn μg/L <1 5.5 760 <1 22 1,700 4 46 

Mercury, total recoverable as Hg μg/L <.1 -- .1 <.1 .1 .4 <.1 <.1 

Molybdenum, total recoverable as Mo μg/L <1 -- 2 <1 1 2 <1 <1 

Molybdenum, dissolved as Mo μg/L <1 -- <1 <1 1 3 <1 <1 

Nickel, total recoverable as Ni μg/L <1 -- 17 67 95 130 <1 16 

Nickel, dissolved as Ni μg/L <1 -- 17 <1 <1 1 <1 <1 

Selenium, total recoverable as Se μg/L <1 -- <1 <1 -- 5 <1 <1 

Silver, total recoverable as Ag μg/L <1 -- <1 <1 <1 <1 <1 <1 

Silver, dissolved as Ag μg/L <1 -- 2 <1 <1 <1 <1 <1 

Zinc, total recoverable as Zn μg/L <10 <10 430 40 460 2,200 <10 150 

Zinc, dissolved as Zn μg/L <3 5.5 320 <1 2 44 <3 3 

Uranium, natural, dissolved μg/L <1 -- 2 <1 <1 3 <1 <1 

Carbon, organic, total as C mg/L 1.0 -- 33 5.6 94 150 4.7 9.4 Carbon, organic, dissolved as C mg/L .5 -- 3.3 2.4 3.2 3.7 2.3 3.0 Sediment, suspended mg/L <1 5.5 1,180 34 7,190 38,800 66 1,510 Sediment, suspended, % finer than 0.062 mm % 14 69 100 35 88 100 37 90 Sediment, suspended, discharge T/d .001 .19 1,370 .0005 .16 13 .012 .16 

Table 35. Summary of stream and road-runoff water quality, water years 1995

–97

—Continued

[--, insufficient data to calculate statistic; ranges of site data computed from all stream-water-quality sites; stream median statistic is the median of all individual site medthe Appendix; **, 1995 data at higher detection limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turb

milligrams per liter; <, less than; μg/L, micrograms per liter; %, percentage; mm, millimeters; T/d, tons per day]

Consituent or property Units

Streams

Road runoff

Rainstorm-related Snowmelt-rela

Minimum Median Maximum Minimum Median Maximum Minimum Median 
CHARACTERIZATION OF GUANELLA PASS ROAD RUNOFF 109

and have a small capacity for dilution. For the 

WY 1996–97 estimates of road-runoff contributions to 

the CC2 basin, dilution of road-runoff water yield by 

South Clear Creek during rapid snowmelt on the road 

and early basin snowmelt (generally May) ranged 

from a factor of approximately 10 to 100 (dilution estimated from comparison of daily mean flow at CRD7 

and CC2 in Stevens [2000]). During peak basin snowmelt (late May and early June), dilution factors of 

road runoff by snowmelt generally ranged from a few 

hundred to several thousand. Dilution factors for 

late-summer-rainstorm road runoff were in the range 

of 10 to 500 (Stevens, 2000). Thus, the potential 

water-quality effects of road runoff is more substantial 

during low streamflows and possibly inconsequential 

during high streamflows because of differences in 

dilution.

Concentrations of dissolved zinc and copper and 

total recoverable iron and manganese, trace elements 

that tended to exceed stream-water-quality standards 

at some stream sites along the Guanella Pass road, 

are present in road runoff. Rainstorm and snowmelt 

road-runoff median concentrations of dissolved copper 

(2 and 1 μg/L) and dissolved zinc (3 and 2 μg/L) 

(table 35) are generally below the range in standards 

(2 to 16 μg/L for copper, 16 to 106 μg/L for zinc) 

(table 30), indicating small potential influence on 

stream-water quality. Rainstorm and snowmelt roadrunoff median concentrations of total recoverable iron 

and manganese (110,000 and 45,000 μg/L for iron; 

3,900 and 910 μg/L for manganese) (table 35) are 

generally above the standards (1,000 μg/L for iron 

and manganese) (table 30), indicating a potential 

effect on stream concentrations.

 The trace elements tend to be in particulate 

form, reducing the toxicity as defined by Colorado 

water-quality standards, which are primarily based on 

dissolved concentrations of trace elements (Colorado 

Department of Public Health and Environment, Water 

Quality Control Commission, 1996). Dissolved trace 

(21) (23) (18)

streamflow High streamflow runoff

Road

TYPE OF SAMPLE

1

100,000

2

3

4

5

7

10

20

30

40

50

70

100

200

300

400

500

700

1,000

2,000

3,000

4,000

5,000

7,000

10,000

20,000

30,000

40,000

50,000

70,000

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

EXPLANATION

Minimum value

25th percentile

Median

75th percentile

Maximum value

(21) Number of observations

Suspended-sediment concentration

Low

Figure 47. Distribution of suspended-sediment concentrations for highstreamflow, low-streamflow, and road-runoff samples.
110 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

elements may be more bioavailable than particulate 

trace elements (Rainbow and Dallinger, 1993). The 

particle-related trace elements, however, may be transported to other geochemical environments (such as 

low pH) where they could become soluble and available to biota (Sundby, 1994).

Once a small sediment particle has become 

suspended in road runoff and enters a stream, it 

may not readily settle out of the water column. The 

particle-size data for road runoff (Stevens and others, 

1997) indicates that the sediment eroding from the 

present road is primarily composed of fine particles. 

The median percentage of particles finer than 

0.062 mm from 11 road-runoff samples (Stevens and 

others, 1997) was 84 percent. For six of the samples, 

smaller particle sizes were differentiated. Of those 

samples, an average of more than 20 percent of the 

particle weight was finer than 0.002 mm. These particles would have a settling time of more than 80 hours 

in 100 cm of still water at 20°C (Guy, 1969). The fine 

particle size decreases the likelihood that settling or 

filtration of the particle will occur in the buffer zone 

between the road and stream. The fine particle size 

also increases the likelihood that the particle will 

be transported in the stream and will not settle on the 

streambed. In some basins, this means transport out of 

the basin; in others, it means that particles may not 

settle out until they enter lakes or reservoirs.

Lakes and Reservoirs

Lakes and reservoirs may be long-term storage 

sites for many of the constituents in road runoff. In 

general, the lakes and reservoirs in the area had values 

and concentrations similar to low-flow stream concentrations (Appendix tables 36–49). Road runoff has 

the potential to alter lake and reservoir inflows, as 

described in the previous section, and to flow directly 

into lakes and reservoirs near the road. Increases in 

dissolved constituents or turbidity in inflows can 

promote stratification in lakes and reservoirs because 

of density differences between inflows and lake and 

reservoir water (Cole, 1994). Studies of Alaskan 

lakes indicate that an increase of as little as 5 NTU 

of turbidity in a clear lake can reduce the euphotic 

volume by as much as 80 percent (Lloyd and others, 

1987). Increases in nutrients from road runoff may 

increase lake/reservoir algal productivity and accelerate eutrophication. Inputs of organic carbon from 

road runoff may increase oxygen demand and cause 

oxygen deficiencies in water at lake or reservoir 

bottoms. Low dissolved-oxygen concentrations 

near the bottom of lakes or reservoirs may promote 

the solubility of nutrients in the bottom sediments, 

creating a seasonal cycle of nutrient enrichment that 

could increase algal productivity (Cole, 1994). Trace 

elements, including some of the same trace elements 

delivered by road runoff, may become environmentally available during overturn of oxygen-depleted 

bottom waters of a lake or reservoir (Sundby, 1994). 

Excess sediment from road runoff may accumulate, 

causing a loss of reservoir capacity (MacDonald and 

others, 1991).

Georgetown Reservoir, the source of drinking 

water for Georgetown and water for the hydroelectric 

powerplant in Georgetown, may be sensitive to the 

effects of road runoff. Water that is relatively free 

of suspended sediment and turbidity is required for 

these uses. The large suspended-sediment concentrations and turbidity values in road runoff have the 

potential to degrade the quality of the water in the 

reservoir should the runoff reach the reservoir. 

Ground Water

The potential effects of road runoff on ground 

water primarily result from dissolved constituents; 

most particulates would be removed as the water infiltrates through soil. Even if particle-related constituents 

reached the ground-water system, particulate matter 

would probably be decreased substantially by sedimentation, precipitation, and adsorption as the water 

moves through the system (Andrews and others, 

1984). Of the dissolved constituents, median concentrations of hardness, alkalinity, the major ions (except 

sodium, potassium, and chloride), and dissolved solids 

are lower in road runoff (table 35) than in the ground 

water sampled (Appendix table 50), which indicates 

the potential for dilution of constituents in road runoff 

by ground water. The median concentrations of chloride, nitrite plus nitrate, ammonia, and dissolved 

aluminum, iron, and manganese were much larger 

in road runoff than ground water, indicating that 

ground-water concentrations of these constituents 

might increase with road-runoff infiltration. Wells near 

roads receiving sodium chloride or magnesium chloride treatments, such as the east well of Guanella Pass 

Campground, might be affected by the relatively large 

concentrations of infiltrating magnesium and chloride 

from road runoff. 
BULK ATMOSPHERIC DEPOSITION 111

BULK ATMOSPHERIC DEPOSITION

Bulk atmospheric-deposition samples were 

collected near the Guanella Pass road to assess 

particle-deposition (dust) conditions (table 1, fig. 3). 

Bulk atmospheric deposition was studied because the 

issue of dust deposition as a source of sediment to 

streams and lakes was considered important during 

initial discussions of the project. Deposited dust also 

can stress vegetation and alter acidic tundra soil chemistry near roadsides (Auerbach and others, 1997). 

Nutrients and organic chemicals from combustion 

engine emissions (from snowmobiles) have been 

shown to accumulate in roadside snowpack (Ingersoll, 

1999). The bulk atmospheric deposition in this study 

was collected in open plastic buckets anchored to the 

ground and included precipitation, atmospheric particles, side-cast or wind-blown particles, loose particles 

bouncing downslope, raindrop-impact splash, throughfall from vegetation, vegetation debris, and insects.

Effect of Road-Surface Type

In 1995, 10 sites were chosen to represent the 

range of geographical and road-surface variation in the 

study area. Particles settling to the ground or deposited 

with precipitation were measured using open-bucket 

collectors placed along several paved and unpaved 

(gravel or dirt) sections of the Guanella Pass road and 

at reference sites located at least 500 ft away from any 

road. The collectors near the road were placed 15 ft 

(horizontal distance) from the edge of the road. At 

most sites, this distance from the road was near the 

edge of the disturbed zone (cut or fill area) along the 

road. The collectors accumulated particulate matter for 

14 days in August and 21 days in October 1995. These 

time spans were long enough to include some dry 

periods and were chosen to include full weeks because 

more than twice the number of vehicles travel the road 

on weekend days than on weekdays. Just north of 

Grant, traffic counts during summer months averaged 

2,935 vehicles per week; just south of Georgetown, 

traffic counts averaged 4,375 vehicles per week 

(Federal Highway Administration, 1998). Average 

deposition rates for each site for both periods were 

computed, and then all deposition rates, by site type, 

were grouped together for computation of median 

deposition rates (fig. 48).

The comparison of deposition rates indicates 

that unpaved roads produce substantially more bulk 

atmospheric deposition near the road than paved roads 

(fig. 48). The median deposition rate near unpaved 

(gravel or dirt) roads was about 105 times the median 

rate at reference sites (located at least 500 ft away 

REFERENCE PAVED UNPAVED

ROAD SURFACE OR SITE TYPE

0

1,400

200

400

600

800

1,000

1,200

MEDIAN BULK ATMOSPHERIC-DEPOSITION RATE,

IN MILLIGRAMS PER DAY PER SQUARE FOOT

1,260

12 32

Figure 48. Comparison of median bulk atmospheric-deposition 

rates by type of site.
112 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

from a road). The median deposition rate near paved 

roads was about three times the median rate at reference sites. Because the weights of bulk deposition 

solids for the 21 days were smaller than the weights 

for the 14 days, other factors, such as precipitation or 

traffic levels, may have had a more important effect 

than the length of the collection period. A comparison 

of the deposition rates between individual sites and the 

deposition rates during the two sampling periods at the 

same site indicate that deposition rates are highly variable areally and temporally (Stevens, 1999).

Distribution Characteristics

The settling pattern of dust (less than 

2 mm in diameter) near a section of gravel road on 

Guanella Pass was investigated for 56 days in August 

and September 1996 at site G (table 1, fig. 3) located 

near the summit of Guanella Pass in the Duck Creek 

drainage upstream from Duck Lake (Stevens, 2000). 

Bucket collectors placed at increasing distances from 

the edge of both sides of the road showed an exponential decrease in the amount of deposited material with 

increasing distance from the road (fig. 49).

Some chemical-distribution characteristics 

were analyzed from samples of bulk atmospheric 

deposition in 1995. The materials captured by a 

bulk atmospheric-deposition collector consisted of 

mostly inorganic particles (rock and soil dust) with 

some organic particles (leaves and insects). Sites E, 

F, G, H, and J are on road segments that have been 

treated with magnesium chloride or sodium chloride. 

The chloride deposition rates at sites E, F, G, H, and J 

(15 ft away from road) averaged 6.85 mg/d/ft2

. Chloride deposition rates for reference sites B, C, F, H, 

and K (at least 500 ft from the road) averaged 

0.22 mg/d/ft2

 (Stevens and others, 1997). The large 

chloride deposition rates near the road indicate that 

some of the chloride is moving off the road in bulk 

atmospheric deposition.

Estimate of Bulk Atmospheric-Deposition 

Contributions from an Unpaved Road 

Section

To investigate the potential effect of 

bulk atmospheric deposition on suspendedsediment transport in a stream next to a unpaved 

(gravel) road, deposition rates in the flood plain 

of Geneva Creek were measured in August and 

September 1997 and compared to suspendedsediment load during the same period in adjacent 

Geneva Creek. Bucket collectors were placed at a 

range of locations from the road on the streamward 

100

100,000

200

500

1,000

2,000

5,000

10,000

20,000

50,000

BULK ATMOSPHERIC DEPOSITION,

IN MILLIGRAMS

East side of road

West Side

0 100 200 300 400 500 600

DISTANCE FROM ROAD, IN FEET

Figure 49. Distribution of bulk atmospheric deposition at site G, August through September 1996.
BULK ATMOSPHERIC DEPOSITION 113

side at three locations (L, M, N, table 1, fig. 3). 

Deposition rates of particles passing a 2-mm sieve 

(to remove large detrital debris) were computed for 

61 days during August 1 to September 30, 1997. 

The natural logarithm of the deposition data for 

all three sites and the natural logarithm of distance 

from the road (fig. 50) were used to develop a linear 

regression equation. The equation was used to represent a deposition function for the streamward side 

of a 3.53-mile section of the Guanella Pass road (from 

the end of pavement just north of Grant to the end 

of gravel road just south of the Scott Gomer Creek 

road crossing). The road segment was divided into 

39 subsections (most segments were 500 ft long). 

The distance from the road edge to the stream edge 

and the width of the stream at each subsection were 

measured from a map of the Guanella Pass Road 

corridor (Centennial Engineering, written commun., 

1996). Numeric integration by Simpson’s rule 

(Swokowski, 1979) was used to integrate the deposition equation (which is a function of distance from the 

road) over the width of the stream at the distance from 

the road where the active channel is located in each 

subsection. A midinterval method was then used to 

compute the deposition along the length of the stream, 

assuming that the length of the stream and the length 

of the road were similar.

Results indicate that bulk atmospheric deposition onto the active channel of Geneva Creek was 

inconsequential when compared to the low-flow 

suspended-sediment transport in Geneva Creek 

(site GC11) during August through September 1997. 

During the period, Geneva Creek transported an 

estimated 165 tons of suspended sediment (Stevens, 

2000), whereas bulk deposition directly to the active 

channel during the same period was estimated to be 

1.7 tons, about 1 percent of the stream suspendedsediment transport. 

The differences in size between bulk atmospheric deposition and suspended sediment during 

August and September could affect an assumption of 

transport in the stream. The bulk deposition estimate 

was limited to the particle size less than 2 mm, and 

suspended sediment in Geneva Creek was usually near 

100 percent finer than 0.062 mm during the low-flow 

season (Stevens and others, 1997). The percentage 

finer than 0.062 mm of nine bulk atmosphericdeposition samples collected 10 feet from the road 

ranged from 30 to 81, whereas at 49 feet from the road 

the percentage was generally greater than 80 percent 

(table 62 in Stevens [2000]). This indicates that sandsized particles (greater than 0.062 mm) might be 

deposited in the sections of stream near the road and 

could remain on the stream bottom until higher flows 

transport them.

1

1,000

2

5

10

20

50

100

200

500

DEPOSITION RATE OF PARTICLES LESS 

THAN 2 MILLIMETERS, IN MILLIGRAMS

PER DAY PER SQUARE FOOT 

5 10 20 50 100 200 500 1,000

DISTANCE FROM ROAD, IN FEET

Figure 50. Relation of bulk atmospheric-deposition (less than 2 millimeters) rate and distance from the 

Guanella Pass road for data collected at sites L, M, and N, August through September 1997.
114 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

SUMMARY AND CONCLUSIONS

This study of water quality, road runoff, 

and bulk atmospheric deposition in the Guanella 

Pass area during WY’s 1995–97 (October 1994 to 

September 1997) characterizes conditions in the South 

Clear Creek and Geneva Creek Basins about 40 miles 

west of Denver, Colorado, prior to a possible Guanella 

Pass road-reconstruction project.

During the study period, water in streams was 

relatively dilute, with specific-conductance values 

generally less than 100 μS/cm. The specific conductance of South Clear Creek generally increased in a 

downstream direction, possibly due to applications of 

magnesium chloride to portions of the Guanella Pass 

road, the effects of evapotranspiration, tributary 

inflow, or ground-water inflow. Specific conductance 

decreased in a downstream direction along Geneva 

Creek, a stream affected by acid-sulfate weathering, 

because of dilution from less concentrated tributary 

flows. 

Values of pH generally were neutral (between 

about 7 and 8) except at GC7 and GC6, mineralized 

sites in the upper part of Geneva Creek, where pH 

values as low as 3.9 were measured. Dissolved 

oxygen ranged from 6.7 mg/L to 11.6 mg/L, and 

median percentages of dissolved oxygen saturation 

at each site ranged from 99 to 104.

Stream major-ion chemistry was characterized 

by the predominance of calcium and bicarbonate at 

most sites except the stream reaches where acidsulfate weathering contributes enough sulfate to dominate the anions in stream water (upper Geneva and 

Leavenworth Creeks). Nutrient concentrations were 

generally small, except during high streamflow and 

storm runoff when particulate phases increased. 

Dissolved trace-element concentrations 

in the Guanella Pass area (excluding aluminum, 

barium, iron, and manganese) were generally less 

than 10 μg/L, except in streams affected by acidsulfate weathering. Total recoverable trace-element 

concentrations were generally larger than dissolved 

concentrations during snowmelt and stormflow, when 

suspended-sediment concentrations also were relatively large. 

In Geneva Creek, at site GC6 September 1995, 

most of the copper load was in the dissolved phase. 

As the stream flowed downstream from GC6 to GC12, 

the pH changed from 3.8 to 7.4. Dissolved copper 

decreased sharply in a downstream direction while 

total recoverable copper remained fairly steady, indicating that most of the copper changed to a suspendedsolid phase. Most of the aluminum and iron were in 

the dissolved phase at site GC6, but they precipitated 

prior to reaching GC9. The pH change did not affect 

manganese and zinc as much because the data indicate 

that most of the loads remained in the dissolved phase 

from GC6 to GC12.

Decreases in dissolved trace-element loads 

measured during rainstorms also were observed and 

might be explained by adsorption to suspended sediment. The decreases imply that sediment-laden stormflow may not degrade trace-element water quality 

because stream concentrations of dissolved trace 

elements decreased, improving water quality when 

compared to Colorado water-quality standards.

Suspended-sediment concentrations varied 

seasonally, being large during peak snowmelt and 

rainstorms and small during low flow and winter 

periods. Instantaneous suspended-sediment concentrations collected by equal-width-increment (EWI) 

methods ranged from less than 1 mg/L at many sites 

during low flow to 1,180 mg/L at a site on upper South 

Clear Creek. Median suspended-sediment concentrations (EWI’s only) at most sites were generally less 

than 20 mg/L.

The relation of annual suspended-sediment 

discharge and annual streamflow to annual suspendedsediment discharge and drainage basin area indicates 

that annual suspended-sediment discharge at each 

site is proportional to annual flow and large basins 

tend to produce large loads. Suspended-sediment 

yields per acre-foot of water discharge at Guanella 

Pass sites were within the range of mean yields at 

crystalline bedrock comparison sites in Colorado 

except for water year 1995, when they were much 

larger than the means but still within the range 

of the comparison site maximum yields.

Generally, greater than 80 percent of suspended 

sediment was transported during the rising and falling 

limbs of the annual snowmelt hydrograph (about May 

to July). Transport during rainstorms only accounted 

for less than about 15 percent of the annual suspendedsediment discharge. Transport relations, yield comparisons, and peak rain-event suspended-sediment 

concentrations indicate that upper South Clear Creek, 

a basin receiving road runoff, had a larger rate of 

suspended-sediment transport than a similar-sized, 

undeveloped basin (Deer Creek near Bailey).
SUMMARY AND CONCLUSIONS 115

Bed-material particle-size data indicate that, 

at most sites, sand-sized or smaller material accounts 

for less than 10 percent, and the silt/clay fraction 

accounts for less than 1 percent of the streambed 

material. Therefore, bed-material composition for 

algae, macroinvertebrates, and fish, which prefer 

coarser materials, seems to be adequate habitat.

Seasonal stratification patterns indicate that 

the deeper (greater than 50 ft) lakes and reservoirs 

profiled (such as Duck Lake, Clear Lake, and Green 

Lake) are dimictic, with thermoclines forming in 

summer and winter, and the lake and reservoir 

contents mix and reoxygenate during overturn 

in the spring and fall. Bottom-water hypoxia (low 

oxygen) was more pronounced in Duck Lake than 

in Clear Lake; minimum dissolved oxygen concentrations in Duck Lake generally were less than 2 mg/L 

except in October 1996.

Concentrations of major ions, nutrients, and 

trace elements in lakes and reservoirs were generally 

similar to stream concentrations. However, the large 

concentrations of ammonia, phosphorus, iron, and 

manganese in bottom-water samples of Duck and 

Clear Lakes indicate release of these constituents from 

bottom sediment, especially in Duck Lake. Both Duck 

and Clear Lakes were classified as oligotrophic in 

water year 1997 according to Carlson’s trophic state 

index.

Among lake and reservoir sites sampled 

for bottom-sediment trace elements, Green Lake 

and Georgetown Reservoir generally had the largest 

concentrations of zinc and lead. The larger concentrations of these trace elements in bottom sediment 

is related to sources of trace elements in the 

Leavenworth Creek Basin, which is the major 

water source to both impoundments.

 Ground-water samples collected from sites 

downslope from parts of the Guanella Pass road that 

were treated with magnesium chloride showed chloride concentrations that were generally larger than 

concentrations at other sites. Dissolved nutrient 

concentrations in ground water were similar to 

concentrations in stream water. Nitrite plus nitrate was 

the dissolved nutrient detected most frequently, with a 

median concentration of 0.08 mg/L as N and a range 

of less than 0.05 to 0.15 mg/L as N. Trace-element 

concentrations in ground water generally were low 

except for some large concentrations of iron, 

manganese, and zinc at some wells.

Colorado water-quality standards for samples 

collected at six stream-sampling sites adjacent to 

the Guanella Pass road were based on numeric-fixed 

standards or standard equations and were used to evaluate stream concentrations. Generally, at the six sites 

evaluated, the total recoverable iron chronic standard 

was exceeded most frequently. Zinc standards (both 

acute and chronic) were exceeded numerous times at 

the Geneva Creek at Grant site (GC11). Total phosphorus concentrations in storm runoff of Guanella 

Pass occasionally exceeded the U.S. Environmental 

Protection Agency guideline of 0.1 mg/L as P for 

streams. An analysis of a ground-water sample 

from the well on the west loop of the Guanella Pass 

campground (GW3) contained 67 μg/L of uranium 

in August 1995 and 44 μg/L in September 1997, 

exceeding the U.S. Environmental Protection 

Agency proposed primary MCL of 20 μg/L.

Road runoff occurred during snowmelt and rainstorms. Individual culvert and ditch-water discharges 

generally were small compared to stream discharge. 

At one site monitored continuously for discharge 

(WY’s 1996–97), most road runoff (77 to 96 percent) 

was a result of snowmelt. Runoff from the road 

preceded the basinwide peak streamflow, resulting in 

sediment and water-quality inputs to the stream when 

streamflow and the potential for dilution of the road 

runoff were low. For the WY 1996–97 estimates of 

road-runoff contributions to the CC2 basin, dilution of 

road-runoff water yield by South Clear Creek during 

rapid snowmelt on the road and early snowmelt in the 

watershed (generally early May) ranged from a factor 

of approximately 10 to 100 (dilution estimated from 

comparison of daily mean flow at CRD7 and CC2). 

During peak basin snowmelt (late May and early 

June), dilution factors of road runoff by snowmelt 

generally ranged from a few hundred to several thousand. Dilution factors for late-summer-rainstorm road 

runoff were in the range of 10 to 500. Thus, the potential water-quality effects of road runoff are more 

substantial during low streamflows and possibly 

inconsequential during high streamflows because 

of differences in dilution.

Specific conductance of road-runoff samples 

ranged from 14 to 468 μS/cm. The range of specific 

conductance of rainfall runoff was larger than values 

from snowmelt runoff. Major-ion composition of 

some samples indicated effects from deicing salt 

(NaCl) and dust inhibitor (MgCl2) applied to sections 

of the road.
116 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

The estimated mass of chloride from MgCl2

applied to the road for dust-suppressing purposes in 

the CC5 basin in 1987 (57.1 tons chloride), 1993 

(11.5 tons), and 1996 (15.5 tons) ranged from 80 to 

414 percent of the estimated average annual chloride 

load (13.8 tons per year) transported in South Clear 

Creek at CC5 during WY’s 1995–97. 

To estimate how chloride applied to the road 

might affect concentrations in the stream, a hypothetical set of assumptions were used to compute changes 

in annual flow-weighted-mean concentrations 

(FWMC) of chloride transported from the CC5 basin. 

For the computation, it was assumed that the mass of 

chloride from the largest known application of MgCl2

applied to the Guanella Pass road in the CC5 basin 

(57.1 tons in 1987) was added to the estimated annual 

chloride load for each year 1995–97 at CC5. That load 

was then assumed to have been transported by the 

annual flow at CC5 that year and is converted to an 

annual FWMC of chloride. The FWMC that includes 

road-applied chloride could then be compared to the 

FWMC without road-applied chloride.

Results of the FWMC comparison indicate 

hypothetical increases in chloride from MgCl2

ranging from about 3 to 12 times. In the case of 

the largest increase, the annual FWMC of chloride 

at CC5 in 1996 (0.5 mg/L) might increase 12 times 

(to 5.9 mg/L). Although this is a large percentage 

increase, the increased concentrations are still relatively minor, about 14 percent of the dissolved solids 

FWMC of 41 mg/L at CC5 in 1996.

Nutrients were commonly measured at larger 

concentrations in road-runoff samples than in streamflow. Concentrations of dissolved inorganic nitrogen 

(nitrate and ammonia) in rainfall-generated road 

runoff were more similar to the concentrations in 

precipitation than to the concentrations in stream 

water. Concentrations of total ammonia plus organic 

nitrogen (range less than 0.2 to 24 mg/L as N) and 

total phosphorus (range 0.024 to 7.2 mg/L as P) 

were generally large in snowmelt and rainstorm 

samples and were related to abundant particulate 

organic material and suspended sediment in the road 

runoff. In general, rainstorm-related median concentrations of total ammonia plus organic nitrogen and 

total phosphorus were at least an order of magnitude 

larger than snowmelt medians.

The largest concentrations of trace elements 

measured in road-runoff samples were for aluminum, 

iron, and manganese. Other trace elements with 

median concentrations greater than the laboratory 

MRL were total recoverable and dissolved barium, 

total recoverable cadmium (rainfall only), total recoverable chromium, total recoverable cobalt, total recoverable and dissolved copper, total recoverable lead, 

total recoverable mercury (rainfall only), total recoverable and dissolved molybdenum (rainfall only), total 

recoverable nickel, and total recoverable and dissolved 

zinc. In general, rainstorm-related concentrations were 

larger than snowmelt concentrations. Trace-element 

data indicate that total recoverable trace-element 

concentrations were substantially larger (by several 

times) than dissolved trace-element concentrations, 

indicating that most trace elements were particulate. 

This indicates that most of the stream trace-element 

standards would not likely be exceeded as a result 

of road-runoff constituents discharged into streams 

because the standards specify primarily dissolved 

phases, and trace elements in road runoff were 

primarily in the suspended phase. Two road-runoff 

samples collected during snowmelt and analyzed 

for trace-organic substances did not contain volatile 

or semivolatile organic substances greater than the 

laboratory MRL.

The suspended-sediment concentrations 

in snowmelt-generated road runoff ranged from 

66 to 7,360 mg/L, with a median concentration of 

1,510 mg/L. Rainstorm-runoff concentrations ranged 

from 34 to 38,800 mg/L, with a median of 7,190 mg/L. 

The sediment was primarily fine grained. More than 

90 percent of suspended sediments from snowmelt 

samples and 88 percent from rainstorm samples were 

finer than 0.062 mm. This fine-grained character facilitates transport of the sediment and diminishes the 

likelihood that settling or deposition of the sediments 

would occur prior to reaching a stream.

Assessment of road-runoff effects depends 

on establishing a connection between erosion on the 

road and delivery of runoff to the adjacent stream. 

Fifty-six percent of the total number of culvert and 

roadside-ditch drainage features on the Guanella Pass 

road showed evidence of recent runoff connection to 

the stream. The average travel distance of road runoff 

that was stopped by the vegetative buffer between the 

road and adjacent stream was 184 ft but ranged from 

less than 5 to 1,295 ft. 

The comparison of deposition rates indicates 

that unpaved roads produce substantially more bulk 

atmospheric deposition near the road than paved 

roads. The median deposition rate near unpaved 
REFERENCES CITED 117

(gravel or dirt) roads was about 105 times the median 

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Bucket collectors placed at increasing distances 

from the edge of both sides of the road indicated an 

exponential decrease in the amount of deposited 

material with increasing distance from the road. 

During August to September 1997, bulk atmospheric 

deposition directly on the active channel of a reach of 

Geneva Creek was estimated to be 1.7 tons, or about 

1 percent of the estimated 165 tons of suspended sediment transported past the nearby stream-monitoring 

site near Grant, indicating that bulk atmospheric deposition had little potential effect on suspended-sediment 

transport in Geneva Creek.

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APPENDIX—HYDROLOGIC AND 

WATER-QUALITY DATA
A

PPENDIX—HYDROLOGICANDWATER-QUALITYDATA123

Table 36. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC1 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams pemicrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe

Specific conductance μS/cm 16 100 37 11 26 27 28 34 42 pH units 10 100 -- -- 7.2 7.2 7.5 7.6 7.6 Turbidity NTU 16 100 2.4 1.2 .9 1.3 1.6 2 2.8 Dissolved oxygen mg/L 10 100 8.8 1 7.4 7.4 7.7 9.2 9.6 Dissolved oxygen saturation % 10 100 101 3.8 97 97 99 100 103 1Hardness as CaCO3 mg/L 5 100 16 4.8 11 -- -- 16 -- Calcium, dissolved mg/L 5 100 4.5 1.3 3.1 -- -- 4.6 -- Magnesium, dissolved mg/L 5 100 1.1 .3 .8 -- -- 1.1 -- Sodium, dissolved mg/L 5 100 1.3 .4 .8 -- -- 1.5 -- Potassium, dissolved mg/L 5 100 .5 .2 .2 -- -- .5 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 5 100 18 6 11 -- -- 19 -- Sulfate, dissolved mg/L 11 100 1.5 .5 .8 .8 1 1.4 1.8 Chloride, dissolved mg/L 13 100 .2 .1 .1 .1 .1 .1 .3 Fluoride, dissolved mg/L 3 67 -- -- <.1 -- -- .1 -- Silica, dissolved mg/L 5 100 6.7 1.6 4.9 -- -- 7.5 -- Dissolved solids, residue at 180 degrees Celsius mg/L 7 100 35 9.3 24 -- -- 35 -- Nitrite, dissolved as N mg/L 2 50 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L **10 60 .021 .039 <.005 <.005 <.005 .011 .016 Nitrogen, ammonia, dissolved as N mg/L **10 30 .002 .002 <.002 <.002 <.002 <.002 .002 Nitrogen, ammonia plus organic, dissolved as N mg/L 2 100 -- -- .2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 10 40 .2 .1 <.2 <.2 <.2 .2 .2 Phosphorus, total as P mg/L **10 100 .013 .006 .005 .005 .009 .012 .017 Phosphorus, dissolved as P mg/L 2 100 -- -- .02 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **8 88 .003 .002 <.001 <.001 .001 .002 .005 Aluminum, total as Al μg/L 2 100 -- -- 20 -- -- -- -- Aluminum, dissolved as Al μg/L 2 100 -- -- 20 -- -- -- -- Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- Barium, dissolved as Ba μg/L 2 100 -- -- 16 -- -- -- -- Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
124 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- <1 -- Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- <1 -- Chromium, total as Cr μg/L 2 0 -- -- <1 -- -- -- -- Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- Cobalt, total as Co μg/L 2 0 -- -- <1 -- -- -- -- Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- Copper, total as Cu μg/L 11 18 -- -- <1 -- -- <1 -- Copper, dissolved as Cu μg/L 11 27 -- -- <1 -- -- <1 -- Iron, total as Fe μg/L 11 100 810 360 270 310 460 950 1,100 1,3Iron, dissolved as Fe μg/L 11 100 430 220 140 150 230 420 700 7Lead, total as Pb μg/L 11 0 -- -- <1 -- -- <1 -- Lead, dissolved as Pb μg/L 4 0 -- -- <1 -- -- <1 -- Manganese, total as Mn μg/L 11 91 40 20 <10 10 20 30 50 Manganese, dissolved as Mn μg/L 11 91 11 5 <1 5 8 11 15 Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- Molybdenum, total as Mo μg/L 2 0 -- -- <1 -- -- -- -- Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- Nickel, total as Ni μg/L 2 0 -- -- <1 -- -- -- -- Nickel, dissolved as Ni μg/L 2 0 -- -- <1 -- -- -- -- Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- Zinc, total as Zn μg/L 11 0 -- -- <10 -- -- <10 -- Zinc, dissolved as Zn μg/L 11 54 4 1 <3 3 4 4 5 Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- Carbon, organic total as C mg/L 2 100 -- -- 6.4 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 3.3 -- -- -- -- Sediment, suspended, concentration mg/L 16 100 5 6 1 1 2 4 5 Sediment, suspended, % finer than 0.062 mm % 3 100 -- -- 35 -- -- 55 -- Sediment, load T/d 15 100 .10 .21 .001 .001 .002 .01 .08 

Table 36. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC1 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); *limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams pe

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 125

Table 37. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC2 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); μS

centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; mm, millimeter

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe

Specific conductance μS/cm 49 100 37 77 

pH units 44 100 -- -- 7.2 8 Turbidity NTU 44 100 .4 2.6 Dissolved oxygen mg/L 38 100 8.7 1.2 6.8 7 7.7 8.6 9.7 Dissolved oxygen saturation % 35 100 100 6.6 84 93 97 101 105 1Hardness as CaCO3 mg/L 30 100 39 19 16 16 22 38 52 

Calcium, dissolved mg/L 30 100 8.7 3.5 4.1 4.3 5.6 8.6 12 Magnesium, dissolved mg/L 30 100 4.2 2.6 1.4 1.5 2 3.9 5.5 Sodium, dissolved mg/L 30 100 1.8 .9 .8 1 1.1 1.6 1.9 Potassium, dissolved mg/L 30 100 .8 .4 .5 .6 .6 .7 .8 Acid-neutralizing capacity, lab as CaCO3 mg/L 29 100 36 14 16 16 22 41 48 Sulfate, dissolved mg/L 42 100 3.8 1.6 1.3 1.9 2.4 3.6 4.7 Chloride, dissolved mg/L 44 100 2.8 6.3 .5 .6 .8 1.2 1.6 Fluoride, dissolved mg/L 5 80 -- -- <.1 -- -- .2 -- Silica, dissolved mg/L 30 100 6.4 1.1 4.1 5 5.5 6.4 7.3 Dissolved solids, residue at 180 degrees Celsius mg/L 31 100 60 22 28 34 44 56 72 

Dissolved solids, sum of constituents mg/L 29 100 52 22 24 24 32 53 65 Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 37 86 .028 .031 <.005 .006 .01 .02 .03 Nitrogen, ammonia, dissolved as N mg/L 17 35 .002 .002 <.002 <.002 <.002 <.002 .003 Nitrogen, ammonia plus organic, dissolved as N mg/L 2 50 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 37 43 .3 .8 <.2 <.2 <.2 <.2 .4 Phosphorus, total as P mg/L 37 97 .21 .62 <.001 .006 .008 .01 .042 Phosphorus, dissolved as P mg/L 2 50 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L 17 88 .003 .002 <.001 <.001 .001 .002 .004 Aluminum, total as Al μg/L 2 100 -- -- 60 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 10 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 18 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
126 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 50 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 42 60 5 9 <1 <1 <1 1 2 

Copper, dissolved as Cu μg/L 42 57 1 .4 <1 1 1 1 1 

Iron, total as Fe μg/L 42 100 7,300 17,000 60 300 380 600 3,500 35

Iron, dissolved as Fe μg/L 42 100 220 110 26 67 160 210 310 

Lead, total as Pb μg/L 42 31 5 12 <1 <1 <1 <1 2 

Lead, dissolved as Pb μg/L 8 0 -- -- <1 -- -- <1 -- 

Manganese, total as Mn μg/L 42 67 210 460 <10 1 3 21 98 

Manganese, dissolved as Mn μg/L 42 90 11 24 <1 1 2 3 9 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 50 -- -- <1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 50 -- -- <1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 0 -- -- <1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 42 26 20 50 <10 <10 <10 <10 10 

Zinc, dissolved as Zn μg/L 42 40 3 3 <3 <3 <3 <3 5 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 4.1 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 3.3 -- -- -- -- Sediment, suspended, concentration mg/L 55 94 93 270 <1 1 2 6 28 Sediment, suspended, % finer than 0.062 mm % 22 100 66 24 34 35 42 65 87 Sediment, discharge T/d 55 94 1.2 2.7 .001 .001 .01 .07 .52 

Table 37. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC2 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); μS

centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; mm, millimeter

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 127

Table 38. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC5 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **, limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; %, T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 9

perc

Specific conductance μS/cm 62 100 69 13 51 55 59 64 81 87 

pH units 38 100 -- -- 7.3 7.5 7.6 7.7 7.9 8Turbidity NTU 49 100 22 36 .3 1.2 1.7 2.9 21 77 Dissolved oxygen mg/L 31 100 8.8 1 7.1 7.4 8 8.8 9.7 10Dissolved oxygen saturation % 27 100 101 5 98 93 98 100 103 108 Hardness as CaCO3 mg/L 16 100 28 4.2 25 25 25 27 29 36 

Calcium, dissolved mg/L 16 100 7 1 6.3 6.3 6.3 6.8 7.2 9Magnesium, dissolved mg/L 16 100 2.5 .4 2.2 2.2 2.3 2.4 2.5 3Sodium, dissolved mg/L 16 100 1.3 .2 1.1 1.2 1.2 1.2 1.3 1Potassium, dissolved mg/L 16 100 .9 .3 .7 .7 .7 .9 1 1Acid-neutralizing capacity, lab as CaCO3 mg/L 16 100 28 4.9 23 24 24 26 30 38 Sulfate, dissolved mg/L 29 100 3.6 .9 2.2 2.9 3.1 3.4 3.7 4Chloride, dissolved mg/L 34 100 .7 .4 .3 .3 .3 .6 1 1Fluoride, dissolved mg/L 8 50 -- -- <.1 <.1 <.1 <.1 .1 Silica, dissolved mg/L 16 100 5.5 .5 4.3 4.6 5.2 5.5 5.9 6Dissolved solids, residue at 180 degrees Celsius mg/L 30 100 45 9 23 34 39 44 52 61 Dissolved solids, sum of constituents mg/L 16 100 39 5 35 36 37 37 39 46 Nitrite, dissolved as N mg/L 8 12 -- -- <.01 <.01 <.01 <.01 <.01 Nitrite plus nitrate, dissolved as N mg/L 28 100 .09 .04 .048 .05 .06 .08 .11 Nitrogen, ammonia, dissolved as N mg/L **18 28 <.002 .003 <.002 <.002 <.002 <.002 .002 Nitrogen, ammonia plus organic, dissolved as N mg/L 8 12 -- -- <.2 <.2 <.2 <.2 <.2 Nitrogen, ammonia plus organic, total as N mg/L 28 21 <.2 .3 <.2 <.2 <.2 <.2 <.2 Phosphorus, total as P mg/L 28 96 .08 .25 .001 <.01 .01 .02 .07 Phosphorus, dissolved as P mg/L 8 12 -- -- <.01 <.01 <.01 <.01 <.01 Phosphorus, dissolved orthophosphate as P mg/L **18 50 .001 .001 <.001 <.001 <.001 .001 .002 Aluminum, total as Al μg/L 8 100 1,100 880 100 190 660 980 1,400 2,200 Aluminum, dissolved as Al μg/L 8 100 45 35 7 16 28 35 52 78 Antimony, dissolved as Sb μg/L 8 0 -- -- <1 -- -- <1 -- -- Arsenic, total as As μg/L 8 0 -- -- <1 -- -- <1 -- -- Barium, total as Ba μg/L 8 0 -- -- <100 -- -- <100 -- -- Barium, dissolved as Ba μg/L 8 100 28 1 27 27 27 28 28 29 Beryllium, total as Be μg/L 8 0 -- -- <10 -- -- <10 -- -- 
128 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 8 0 -- -- <1 -- -- <1 -- 

Cadmium, total as Cd μg/L 11 0 -- -- <1 -- -- <1 -- Cadmium, dissolved as Cd μg/L 8 0 -- -- <1 -- -- <1 -- Chromium, total as Cr μg/L 8 75 3 3 <1 1 1 2 5 Chromium, dissolved as Cr μg/L 8 12 -- -- <1 -- -- <1 -- Cobalt, total as Co μg/L 8 62 2 1 <1 <1 1 2 3 Cobalt, dissolved as Co μg/L 8 0 -- -- <1 -- -- <1 -- Copper, total as Cu μg/L 32 72 5 16 <1 <1 <1 1 3 Copper, dissolved as Cu μg/L 29 24 1 <1 <1 <1 <1 <1 1 Iron, total as Fe μg/L 32 100 5,400 1,900 120 250 330 700 3,400 7,5Iron, dissolved as Fe μg/L 29 100 110 63 35 54 72 97 120 2Lead, total as Pb μg/L 32 28 2 9 <1 <1 <1 <1 1 Lead, dissolved as Pb μg/L 13 0 <1 <1 <1 <1 <1 Manganese, total as Mn μg/L 32 88 130 400 <10 3 10 22 100 2Manganese, dissolved as Mn μg/L 29 100 7 3 2 4 6 7 8 Mercury, total as Hg μg/L 8 0 -- -- <.1 -- -- <.1 -- Molybdenum, total as Mo μg/L 8 12 -- -- <1 -- -- <1 -- Molybdenum, dissolved as Mo μg/L 8 0 -- -- <1 -- -- <1 -- Nickel, total as Ni μg/L 8 62 2 2 <1 <1 <1 1 4 4 Nickel, dissolved as Ni μg/L 8 50 -- -- <1 -- -- 1 -- Selenium, total as Se μg/L 8 0 -- -- <1 -- -- <1 -- Silver, total as Ag μg/L 8 0 -- -- <1 -- -- <1 -- Silver, dissolved as Ag μg/L 8 0 -- -- <1 -- -- <1 -- Zinc, total as Zn μg/L 32 34 20 60 <10 <10 <10 <10 10 Zinc, dissolved as Zn μg/L 29 55 3 3 <3 <3 <3 <3 4 Uranium, natural dissolved μg/L 8 0 -- -- <1 -- -- <1 -- Carbon, organic total as C mg/L 7 100 4.6 3.7 2.1 -- -- 3.5 -- Carbon, organic dissolved as C mg/L 4 100 1.6 .4 1.1 -- -- 1.6 -- Sediment, suspended, concentration mg/L 71 100 38 69 1 3 5 14 40 Sediment, suspended, % finer than 0.062 mm % 29 100 72 23 34 40 51 70 95 1Sediment, load T/d 71 100 4.1 14 .01 .02 .12 .57 2.7 

Table 38. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC5 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **, limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; %, T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 9

perc
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 129

Table 39. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC7 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe

Specific conductance μS/cm 43 100 92 15 68 -- -- 87 -- pH units 17 100 -- -- 7.4 -- -- 7.9 -- Turbidity NTU 26 100 3.1 4.6 .2 -- -- 1.6 -- Dissolved oxygen mg/L 17 100 9.1 .8 7.6 -- -- 9.1 -- Dissolved oxygen saturation % 12 100 103 7 93 -- -- 101 -- Hardness as CaCO3 mg/L 5 100 40 5 36 -- -- 38 -- 

Calcium, dissolved mg/L 5 100 11 1.4 9.7 -- -- 10 -- Magnesium, dissolved mg/L 5 100 3.3 .4 3 -- -- 3.1 -- Sodium, dissolved mg/L 5 100 1.5 .1 1.4 -- -- 1.5 -- Potassium, dissolved mg/L 5 100 1.2 .1 1.1 -- -- 1.2 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 5 100 40 4.6 37 -- -- 39 -- Sulfate, dissolved mg/L 6 100 5.2 .6 4.5 -- -- 5.2 -- Chloride, dissolved mg/L 6 100 1 .7 .5 -- -- .7 -- Fluoride, dissolved mg/L 4 100 .2 .1 .1 -- -- .2 -- Silica, dissolved mg/L 5 100 6.4 .3 6.2 -- -- 6.3 -- Dissolved solids, residue at 180 degrees Celsius mg/L 23 100 58 8 44 -- -- 57 -- Dissolved solids, sum of constituents mg/L 5 100 54 5 49 -- -- 53 -- Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 6 100 .1 .01 .09 -- -- .1 -- Nitrogen, ammonia, dissolved as N mg/L **4 25 -- -- <.002 -- -- <.002 -- Nitrogen, ammonia plus organic, dissolved as N mg/L 2 0 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 6 0 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L **4 100 -- -- .001 -- -- .002 -- Phosphorus, dissolved as P mg/L 2 0 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **4 0 -- -- <.001 -- -- <.001 -- Aluminum, total as Al μg/L 2 100 -- -- 30 -- -- -- -- Aluminum, dissolved as Al μg/L 2 100 -- -- 4 -- -- -- -- Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- Barium, dissolved as Ba μg/L 2 100 -- -- 26 -- -- -- -- Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
130 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- <1 -- 

Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- <1 -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 6 0 -- -- <1 -- -- <1 -- 

Copper, dissolved as Cu μg/L 6 0 -- -- <1 -- -- <1 -- 

Iron, total as Fe μg/L 6 100 100 97 40 -- -- 80 -- 

Iron, dissolved as Fe μg/L 6 100 23 19 10 -- -- 18 -- 

Lead, total as Pb μg/L 6 17 -- -- <1 -- -- <1 -- 

Lead, dissolved as Pb μg/L 4 0 -- -- <1 -- -- <1 -- 

Manganese, total as Mn μg/L 6 17 -- -- <10 -- -- <10 -- 

Manganese, dissolved as Mn μg/L 6 33 -- -- <1 -- -- <1 -- 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 100 -- -- 1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 50 -- -- <1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 6 0 -- -- <10 -- -- <10 -- 

Zinc, dissolved as Zn μg/L 6 66 -- -- <3 -- -- 4 -- 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 2 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 1.2 -- -- -- -- Sediment, suspended, concentration mg/L 47 100 7 6 1 -- -- 4 -- Sediment, suspended, % finer than 0.062 mm % 13 100 71 21 26 -- -- 69 -- Sediment, discharge T/d 47 100 .59 .81 .01 -- -- .24 -- 

Table 39. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC7 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 131

Table 40. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC9 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe

Specific conductance μS/cm 44 100 88 38 42 48 55 70 131 pH units 19 100 -- -- 7.0 7.2 7.4 7.5 7.8 Turbidity NTU 35 100 9.5 33 .2 .3 .6 1.5 2.8 Dissolved oxygen mg/L 16 100 9.7 .8 8.4 8.7 9.3 9.8 10.2 Dissolved oxygen saturation % 14 100 101 5.5 93 93 98 101 104 Hardness as CaCO3 mg/L 5 100 31 17 17 -- -- 24 -- 

Calcium, dissolved mg/L 5 100 8.5 4.5 4.6 -- -- 6.5 -- Magnesium, dissolved mg/L 5 100 2.4 1.3 1.3 -- -- 2 -- Sodium, dissolved mg/L 5 100 1.3 .4 .9 -- -- 1.1 -- Potassium, dissolved mg/L 5 100 .7 .2 .4 -- -- .6 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 5 100 18 7 12 -- -- 17 -- Sulfate, dissolved mg/L 6 100 16 10 7.9 -- -- 12 -- Chloride, dissolved mg/L 6 100 .3 .2 .1 -- -- .3 -- Fluoride, dissolved mg/L 3 67 -- -- <.1 -- -- .2 -- Silica, dissolved mg/L 5 100 6.2 1.2 4.8 -- -- 5.9 -- Dissolved solids, residue at 180 degrees Celsius mg/L 28 100 55 18 32 -- -- 51 -- Dissolved solids, sum of constituents mg/L 5 100 48 23 28 -- -- 37 -- Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L **3 100 -- -- .044 -- -- .085 -- Nitrogen, ammonia, dissolved as N mg/L **2 50 -- -- <.002 -- -- -- -- Nitrogen, ammonia plus organic, dissolved as N mg/L 2 50 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 6 0 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L **3 67 -- -- <.001 -- -- .008 -- Phosphorus, dissolved as P mg/L 2 0 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **2 100 -- -- .001 -- -- .002 -- Aluminum, total as Al μg/L 2 100 -- -- 40 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 20 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 27 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
132 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 3 33 -- -- <1 -- -- <1 -- 

Cadmium, dissolved as Cd μg/L 3 0 -- -- <1 -- -- <1 -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 7 100 7 5 1 -- -- 6 -- 

Copper, dissolved as Cu μg/L 6 83 -- -- <1 -- -- 4 -- 

Iron, total as Fe μg/L 7 100 760 970 10 -- -- 320 -- 

Iron, dissolved as Fe μg/L 6 100 52 39 4 -- -- 50 -- 

Lead, total as Pb μg/L 7 100 33 28 2 -- -- 36 -- 

Lead, dissolved as Pb μg/L 4 100 -- -- 1 -- -- 2 -- 

Manganese, total as Mn μg/L 7 71 -- -- <10 -- -- 80 -- 

Manganese, dissolved as Mn μg/L 6 100 23 16 7 -- -- 18 -- 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 50 -- -- <1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 100 -- -- 1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 100 -- -- 1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 7 100 220 100 130 -- -- 190 -- 

Zinc, dissolved as Zn μg/L 6 100 170 72 80 -- -- 170 -- 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 1.7 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 1.2 -- -- -- -- Sediment, suspended, concentration mg/L 53 94 20 51 <1 1 3 4 16 Sediment, suspended, % finer than 0.062 mm % 19 100 51 24 22 27 33 44 62 Sediment, discharge T/d 53 94 -- -- <.004 -- -- .23 -- 

Table 40. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC9 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 133

Table 41. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC11 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe

Specific conductance μS/cm 10 100 46 10 34 35 38 42 58 

pH units 9 100 -- -- 7.9 7.9 7.9 7.9 7.9 Turbidity NTU 10 100 1.4 .6 .8 .8 .9 1.3 1.8 Dissolved oxygen mg/L 10 100 8.8 .9 7.4 8.1 8.2 8.6 9.4 Dissolved oxygen saturation % 7 100 101 1 99 100 100 101 102 1Hardness as CaCO3 mg/L 4 100 20 5.3 15 -- -- 19 -- 

Calcium, dissolved mg/L 4 100 5.8 1.6 4.3 -- -- 5.6 -- Magnesium, dissolved mg/L 4 100 1.2 .3 .9 -- -- 1.2 -- Sodium, dissolved mg/L 4 100 1.6 .3 1.3 -- -- 1.6 -- Potassium, dissolved mg/L 4 100 .7 .1 .6 -- -- .6 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 4 100 20 6 14 -- -- 20 -- Sulfate, dissolved mg/L 5 100 2.7 .6 2.1 -- -- 2.4 -- Chloride, dissolved mg/L 5 100 .2 .06 .2 -- -- .2 -- Fluoride, dissolved mg/L 2 100 -- -- .2 -- -- -- -- Silica, dissolved mg/L 4 100 7.8 1.3 6.4 -- -- 7.8 -- Dissolved solids, residue at 180 degrees Celsius mg/L 4 100 45 8.3 36 -- -- 44 -- Dissolved solids, sum of constituents mg/L 3 100 35 8 25 -- -- 39 -- Nitrite, dissolved as N mg/L 1 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 5 100 .059 .016 .039 -- -- .058 -- Nitrogen, ammonia, dissolved as N mg/L **3 0 -- -- <.002 -- -- <.002 -- Nitrogen, ammonia plus organic, dissolved as N mg/L 1 0 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 5 20 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L **4 100 -- -- .005 -- -- .008 -- Phosphorus, dissolved as P mg/L 1 0 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **3 67 -- -- <.001 -- -- .001 -- Aluminum, total as Al μg/L 1 100 -- -- 20 -- -- -- -- Aluminum, dissolved as Al μg/L 1 100 -- -- 10 -- -- -- -- Antimony, dissolved as Sb μg/L 1 0 -- -- <1 -- -- -- -- Arsenic, total as As μg/L 1 0 -- -- <1 -- -- -- -- Barium, total as Ba μg/L 1 0 -- -- <100 -- -- -- -- Barium, dissolved as Ba μg/L 1 100 -- -- 17 -- -- -- -- Beryllium, total as Be μg/L 1 0 -- -- <10 -- -- -- -- 
134 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 1 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 1 0 -- -- <1 -- -- -- -- 

Cadmium, dissolved as Cd μg/L 1 0 -- -- <1 -- -- -- -- 

Chromium, total as Cr μg/L 1 0 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 1 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 1 0 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 1 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 5 20 -- -- <1 -- -- <1 -- 

Copper, dissolved as Cu μg/L 5 60 -- -- <1 -- -- 1 -- 

Iron, total as Fe μg/L 5 100 260 66 160 -- -- 290 -- 

Iron, dissolved as Fe μg/L 5 100 110 42 70 -- -- 110 -- 

Lead, total as Pb μg/L 5 0 -- -- <1 -- -- <1 -- 

Lead, dissolved as Pb μg/L 3 0 -- -- <1 -- -- <1 -- 

Manganese, total as Mn μg/L 5 40 -- -- <10 -- -- <10 -- 

Manganese, dissolved as Mn μg/L 5 100 3 2 2 -- -- 2 -- 

Mercury, total as Hg μg/L 1 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 1 100 -- -- 2 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 1 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 1 0 -- -- <1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 1 0 -- -- <1 -- -- -- -- 

Selenium, total as Se μg/L 1 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 1 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 1 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 5 0 -- -- <10 -- -- <10 -- 

Zinc, dissolved as Zn μg/L 5 20 -- -- <3 -- -- <3 -- 

Uranium, natural dissolved μg/L 1 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 1 100 -- -- 2.6 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 2.1 -- -- -- -- Sediment, suspended, concentration mg/L 11 91 6 9 <1 1 2 2 8 Sediment, suspended, % finer than 0.062 mm % 3 100 -- -- 36 -- -- 67 -- Sediment, discharge T/d 8 100 .16 .25 .004 .02 .03 .04 .13 

Table 41. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at CC11 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 135

Table 42. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC1 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

p

Specific conductance μS/cm 5 100 33 4 29 -- -- 31 -- 

pH units 7 100 7.6 .2 7.4 7.5 7.5 7.5 7.7 Turbidity NTU 5 100 1.6 .5 1 -- -- 1.5 -- Dissolved oxygen mg/L 8 100 7.7 .6 6.7 7.1 7.3 7.7 8.1 Dissolved oxygen saturation % 7 100 102 6 97 97 98 99 106 Hardness as CaCO3 mg/L 4 100 -- -- 10 -- -- 12 -- 

Calcium, dissolved mg/L 4 100 -- -- 2.8 -- -- 3.4 -- Magnesium, dissolved mg/L 4 100 -- -- .8 -- -- .9 -- Sodium, dissolved mg/L 4 100 -- -- .7 -- -- .8 -- Potassium, dissolved mg/L 4 100 -- -- .6 -- -- .6 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 4 100 -- -- 12 -- -- 12 -- Sulfate, dissolved mg/L 5 100 2.3 .4 1.8 -- -- 2.2 -- Chloride, dissolved mg/L 5 60 -- -- <.1 -- -- .1 -- Fluoride, dissolved mg/L 3 33 -- -- <.1 -- -- <.1 -- Silica, dissolved mg/L 4 100 -- -- 4.1 -- -- 4.4 -- Dissolved solids, residue at 180 degrees Celsius mg/L 4 100 -- -- 16 -- -- 24 -- Dissolved solids, sum of constituents mg/L 3 100 -- -- 20 -- -- 20 -- Nitrite, dissolved as N mg/L 2 50 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L **3 100 -- -- .02 -- -- .033 -- Nitrogen, ammonia, dissolved as N mg/L **2 0 -- -- <.002 -- -- -- -- Nitrogen, ammonia plus organic, dissolved as N mg/L 2 0 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 5 20 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L **3 100 -- -- .01 -- -- .01 -- Phosphorus, dissolved as P mg/L 2 0 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **2 100 -- -- .001 -- -- -- -- Aluminum, total as Al μg/L 2 100 -- -- 20 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 5 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 16 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
136 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Chromium, total as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 5 20 -- -- <1 -- -- <1 -- 

Copper, dissolved as Cu μg/L 5 20 -- -- <1 -- -- <1 -- 

Iron, total as Fe μg/L 5 100 200 80 100 -- -- 210 -- 

Iron, dissolved as Fe μg/L 5 100 90 30 50 -- -- 90 -- 

Lead, total as Pb μg/L 5 0 -- -- <1 -- -- <1 -- 

Lead, dissolved as Pb μg/L 2 0 -- -- <1 -- -- -- -- 

Manganese, total as Mn μg/L 5 60 -- -- <10 -- -- 10 -- 

Manganese, dissolved as Mn μg/L 5 100 3 1 2 -- -- 3 -- 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 0 -- -- <1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 50 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 5 0 -- -- <10 -- -- <10 -- 

Zinc, dissolved as Zn μg/L 5 60 -- -- <3 -- -- <3 -- 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 1.9 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 1.1 -- -- -- -- Sediment, suspended, concentration mg/L 5 80 -- -- <1 -- -- 3 -- Sediment, suspended, % finer than 0.062 mm % 2 100 -- -- 48 -- -- -- Sediment, discharge T/d 5 80 -- -- <.003 -- -- .02 -- 

Table 42. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC1 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

p
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 137

Table 43. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC2 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

p

Specific conductance μS/cm 6 100 39 14 23 -- -- 40 -- 

pH units 8 100 -- -- 7 -- -- 7.6 7.7 Turbidity NTU 6 100 3 .8 2 -- -- 2.8 -- Dissolved oxygen mg/L 8 100 8.1 1 6.7 6.8 7.3 8.2 8.6 Dissolved oxygen saturation % 5 100 100 6 94 95 96 100 101 Hardness as CaCO3 mg/L 4 100 -- -- 9 -- -- 11 -- 

Calcium, dissolved mg/L 4 100 -- -- 2.6 -- -- 3 -- Magnesium, dissolved mg/L 4 100 -- -- .7 -- -- .8 -- Sodium, dissolved mg/L 4 100 -- -- .9 -- -- 1 -- Potassium, dissolved mg/L 4 100 -- -- .5 -- -- .6 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 4 100 -- -- 9 -- -- 11 -- Sulfate, dissolved mg/L 5 100 2.4 1.2 1.4 -- -- 1.8 -- Chloride, dissolved mg/L 5 100 .5 .4 .2 -- -- .3 -- Fluoride, dissolved mg/L 2 100 -- -- .2 -- -- -- -- Silica, dissolved mg/L 4 100 -- -- 5.1 -- -- 5.6 -- Dissolved solids, residue at 180 degrees Celsius mg/L 4 100 -- -- 26 -- -- 30 -- Dissolved solids, sum of constituents mg/L 4 100 -- -- 18 -- -- 22 -- Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L **3 100 -- -- .017 -- -- .019 -- Nitrogen, ammonia, dissolved as N mg/L **2 100 -- -- .002 -- -- -- -- Nitrogen, ammonia plus organic, dissolved as N mg/L 2 50 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 5 80 -- -- <.2 -- -- .2 -- Phosphorus, total as P mg/L 5 100 -- -- .009 -- -- .013 -- Phosphorus, dissolved as P mg/L 2 50 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **2 100 -- -- .001 -- -- -- -- Aluminum, total as Al μg/L 2 100 -- -- 30 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 20 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 16 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
138 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- -- -- Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- -- -- Chromium, total as Cr μg/L 2 100 -- -- 2 -- -- -- -- Chromium, dissolved as Cr μg/L 2 50 -- -- <1 -- -- -- -- Cobalt, total as Co μg/L 2 0 -- -- <1 -- -- -- -- Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- Copper, total as Cu μg/L 5 20 -- -- <1 -- -- <1 -- Copper, dissolved as Cu μg/L 5 20 -- -- <1 -- -- <1 -- Iron, total as Fe μg/L 5 100 740 220 510 -- -- 720 -- Iron, dissolved as Fe μg/L 5 100 400 150 270 -- -- 370 -- Lead, total as Pb μg/L 5 0 -- -- <1 -- -- <1 -- Lead, dissolved as Pb μg/L 3 0 -- -- <1 -- -- <1 -- Manganese, total as Mn μg/L 5 60 -- -- <10 -- -- 10 -- Manganese, dissolved as Mn μg/L 5 100 7 2 5 -- -- 6 -- Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- Molybdenum, total as Mo μg/L 2 0 -- -- <1 -- -- -- -- Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- Nickel, total as Ni μg/L 2 0 -- -- <1 -- -- -- -- Nickel, dissolved as Ni μg/L 2 0 -- -- <1 -- -- -- -- Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- Zinc, total as Zn μg/L 5 0 -- -- <10 -- -- <10 -- Zinc, dissolved as Zn μg/L 5 100 7 3 4 -- -- 6 -- Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- Carbon, organic total as C mg/L 2 100 -- -- 2.9 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 2.2 -- -- -- -- Sediment, suspended, concentration mg/L 6 100 6 4 2 -- -- 6 -- Sediment, suspended, % finer than 0.062 mm % 4 100 -- -- 61 -- -- 79 -- Sediment, discharge T/d 5 100 .095 .12 .005 -- -- .01 -- 

Table 43. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC2 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams pe

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

p
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 139

Table 44. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC5 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); μS

centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; mm, millimeter

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percent- ile 25th percent- ile Median 75th percent- ile 

p

Specific conductance μS/cm 45 100 37 47 

pH units 47 100 -- -- 7.1 -- -- 7.7 -- Turbidity NTU 43 100 .9 2.3 Dissolved oxygen mg/L 42 100 8.4 .8 7.2 7.5 7.8 8.2 8.7 Dissolved oxygen saturation % 32 100 99 3 91 94 97 99 101 Hardness as CaCO3 mg/L 31 100 17 2.4 13 15 15 17 19 

Calcium, dissolved mg/L 31 100 5.1 .7 3.8 4.3 4.4 5.1 5.8 Magnesium, dissolved mg/L 31 100 1.1 .1 .9 1 1 1.1 1.2 Sodium, dissolved mg/L 31 100 1.6 .2 1.2 1.3 1.4 1.7 1.8 Potassium, dissolved mg/L 31 100 .9 .1 .7 .7 .8 .9 1 Acid-neutralizing capacity, lab as CaCO3 mg/L 30 100 19 2 15 16 17 19 21 Sulfate, dissolved mg/L 40 100 3.2 .7 2.1 2.3 2.8 3.2 3.5 Chloride, dissolved mg/L 40 100 .6 .2 .3 .3 .4 .5 .7 Fluoride, dissolved mg/L 7 100 .2 .04 .2 .2 .2 .2 .2 Silica, dissolved mg/L 31 100 7.4 .5 6.3 6.6 7 7.3 8 Dissolved solids, residue at 180 degrees Celsius mg/L 31 100 37 13 10 22 28 36 45 Dissolved solids, sum of constituents mg/L 30 100 25 32 Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 39 97 .048 .03 .006 .011 .023 .048 .065 Nitrogen, ammonia, dissolved as N mg/L 16 31 .006 .012 <.002 <.002 <.002 <.002 .003 Nitrogen, ammonia plus organic, dissolved as N mg/L 2 0 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 39 13 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L 37 100 .011 .018 .002 .002 .004 .006 .008 Phosphorus, dissolved as P mg/L 2 0 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L 16 75 .001 .001 <.001 .001 .001 .001 .002 Aluminum, total as Al μg/L 2 100 -- -- 30 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 6 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 24 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
140 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 45 38 1 1 <1 <1 <1 <1 2 

Copper, dissolved as Cu μg/L 40 22 1 .5 <1 <1 <1 <1 1 

Iron, total as Fe μg/L 45 100 650 850 140 170 210 300 740 

Iron, dissolved as Fe μg/L 40 100 84 47 43 45 52 70 99 

Lead, total as Pb μg/L 45 13 -- -- <1 -- -- <1 -- 

Lead, dissolved as Pb μg/L 8 0 -- -- <1 <1 <1 <1 <1 

Manganese, total as Mn μg/L 45 62 20 20 <10 <10 <10 10 25 

Manganese, dissolved as Mn μg/L 40 98 6 4 <1 2 3 5 6 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 100 -- -- 1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 0 -- -- <1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 45 9 -- -- <10 -- -- <10 -- 

Zinc, dissolved as Zn μg/L 40 45 3 2 <3 <3 <3 <3 4 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 2.3 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 1.4 -- -- -- -- Sediment, suspended, concentration mg/L 54 96 8.2 13 <1 1 2 5 8 Sediment, suspended, % finer than 0.062 mm % 23 100 65 22 29 36 48 63 83 Sediment, discharge T/d 54 100 .68 2.5 .003 .01 .01 .12 .42 

Table 44. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC5 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); μScentimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; mm, millimeter

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percent- ile 25th percent- ile Median 75th percent- ile 

p
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 141

Table 45. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC7 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams pe

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percent- ile 25th percent- ile Median 75th percent- ile 

pe

Specific conductance μS/cm 8 100 79 18 59 62 66 76 87 1

pH units 13 100 5.4 1.3 3.9 4 4.8 5 6.8 Turbidity NTU 8 100 24 33 .9 2.4 5.3 8 25 Dissolved oxygen mg/L 12 100 9.1 1.2 7.7 7.9 8.2 8.9 9.8 Dissolved oxygen saturation % 8 100 104 5.8 97 98 100 102 106 1Hardness as CaCO3 mg/L 3 100 -- -- 22 -- -- 24 -- 

Calcium, dissolved mg/L 3 100 -- -- 5.4 -- -- 6.1 -- Magnesium, dissolved mg/L 3 100 -- -- 2 -- -- 2.2 -- Sodium, dissolved mg/L 3 100 -- -- 1 -- -- 1.2 -- Potassium, dissolved mg/L 3 100 -- -- .8 -- -- .9 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 3 100 -- -- <.1 -- -- 4.6 -- Sulfate, dissolved mg/L 5 100 30 14 18 -- -- 23 -- Chloride, dissolved mg/L 5 100 .4 .3 .1 -- -- .2 -- Fluoride, dissolved mg/L 2 50 -- -- <.1 -- -- -- Silica, dissolved mg/L 3 100 -- -- 5.8 -- -- 7.2 -- Dissolved solids, residue at 180 degrees Celsius mg/L 3 100 -- -- 41 -- -- 70 -- Dissolved solids, sum of constituents mg/L 2 100 -- -- 37 -- -- -- -- Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 5 100 .075 .007 .07 -- -- .07 -- Nitrogen, ammonia, dissolved as N mg/L **2 50 -- -- <.002 -- -- -- -- Nitrogen, ammonia plus organic, dissolved as N mg/L 2 0 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 5 20 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L **3 100 -- -- .002 -- -- .004 -- Phosphorus, dissolved as P mg/L 2 0 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L 2 50 -- -- <.001 -- -- -- -- Aluminum, total as Al μg/L 2 100 -- -- 2,500 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 120 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 30 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
142 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 50 -- -- <1 -- -- -- -- 

Cadmium, dissolved as Cd μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 100 -- -- 2 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 50 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 5 100 13 6 6 -- -- 17 -- 

Copper, dissolved as Cu μg/L 5 100 8 8 2 -- -- 3 -- 

Iron, total as Fe μg/L 5 100 5,100 8,900 1,000 -- -- 1,200 -- 

Iron, dissolved as Fe μg/L 5 100 330 110 210 -- -- 290 -- 

Lead, total as Pb μg/L 5 20 -- -- <1 -- -- <1 -- 

Lead, dissolved as Pb μg/L 2 0 -- -- <1 -- -- -- -- 

Manganese, total as Mn μg/L 5 100 280 160 150 -- -- 190 -- 

Manganese, dissolved as Mn μg/L 5 100 270 170 120 -- -- 190 -- 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 50 -- -- <1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 100 -- -- 5 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 100 -- -- 2 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 5 100 90 60 40 -- -- 70 -- 

Zinc, dissolved as Zn μg/L 5 100 96 68 24 -- -- 67 -- 

Uranium, natural dissolved μg/L 2 50 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 1 -- -- -- -- Carbon, organic dissolved as C mg/L 0 -- -- -- -- -- -- -- -- Sediment, suspended, concentration mg/L 10 100 70 112 7 8 9 18 94 Sediment, suspended, % finer than 0.062 mm % 5 100 81 14 66 -- -- 83 -- Sediment, discharge T/d 8 100 9.6 16.9 .38 -- -- 1.6 -- 

Table 45. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC7 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); *limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams pe

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percent- ile 25th percent- ile Median 75th percent- ile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 143

Table 46. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC8 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

per

Specific conductance μS/cm 10 100 41 7 32 35 36 41 44 

pH units 10 100 -- -- 7.2 7.2 7.4 7.8 7.9 Turbidity NTU 10 100 12 24 1 1.1 1.6 2.2 7.2 Dissolved oxygen mg/L 10 100 9 .9 7.7 8.1 8.5 8.7 9.2 Dissolved oxygen saturation % 5 100 101 4 96 97 99 99 103 1Hardness as CaCO3 mg/L 3 100 -- -- 14 -- -- 14 -- 

Calcium, dissolved mg/L 3 100 -- -- 3.5 -- -- 3.6 -- Magnesium, dissolved mg/L 3 100 -- -- 1.2 -- -- 1.2 -- Sodium, dissolved mg/L 3 100 -- -- 1 -- -- 1.1 -- Potassium, dissolved mg/L 3 100 -- -- .5 -- -- .6 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 3 100 -- -- 10 -- -- 10 -- Sulfate, dissolved mg/L 5 100 6.5 1.3 5.3 -- -- 5.8 -- Chloride, dissolved mg/L 5 100 .3 .2 .1 -- -- .3 -- Fluoride, dissolved mg/L 2 0 -- -- <.1 -- -- -- -- Silica, dissolved mg/L 3 100 -- -- 5.8 -- -- 6.1 -- Dissolved solids, residue at 180 degrees Celsius mg/L 3 100 -- -- 34 -- -- 37 -- Dissolved solids, sum of constituents mg/L 3 100 -- -- 25 -- -- 25 -- Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L **3 100 -- -- .025 -- -- .051 -- Nitrogen, ammonia, dissolved as N mg/L **2 50 -- -- <.002 -- -- -- -- Nitrogen, ammonia plus organic, dissolved as N mg/L 2 0 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 5 40 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L **3 100 -- -- .002 -- -- .007 -- Phosphorus, dissolved as P mg/L 2 50 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **2 50 -- -- <.001 -- -- -- -- Aluminum, total as Al μg/L 2 100 -- -- 100 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 40 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 50 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 26 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
144 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 50 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 5 100 6 6 1 1 1 3 10 

Copper, dissolved as Cu μg/L 5 40 -- -- <1 -- -- <1 -- 

Iron, total as Fe μg/L 5 100 1,700 3,000 120 120 130 260 1,000 4,7

Iron, dissolved as Fe μg/L 5 100 66 31 38 45 55 57 61 

Lead, total as Pb μg/L 5 20 -- -- <1 -- -- <1 -- 

Lead, dissolved as Pb μg/L 2 0 -- -- <1 -- -- -- -- 

Manganese, total as Mn μg/L 5 100 140 230 20 20 20 20 80 3

Manganese, dissolved as Mn μg/L 5 100 12 4 8 8 9 11 16 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 100 -- -- 1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 50 -- -- <1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 50 -- -- <1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 5 60 -- -- <10 -- -- 10 -- 

Zinc, dissolved as Zn μg/L 5 100 -- -- 5 -- -- 5 -- 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 2 -- -- 1.9 -- -- -- -- Carbon, organic dissolved as C mg/L 1 1 -- -- 1.2 -- -- -- -- Sediment, suspended, concentration mg/L 10 10 37 55 2 2 4 10 37 1Sediment, suspended, % finer than 0.062 mm % 5 5 67 33 14 34 63 71 88 Sediment, discharge T/d 7 7 3.4 7.3 .03 .042 .13 .4 1.7 

Table 46. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC8 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 145

Table 47. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC10 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 9

perc

Specific conductance μS/cm 9 100 36 7 26 27 31 36 40 4

pH units 10 100 -- -- 7.3 7.3 7.4 7.7 7.8 Turbidity NTU 9 100 5.5 7.6 1.5 1.7 2 2.2 5 1Dissolved oxygen mg/L 10 100 9.1 1.1 7.4 8 8.4 9.1 9.6 1Dissolved oxygen saturation % 7 100 103 5 97 98 98 104 106 10Hardness as CaCO3 mg/L 3 100 -- -- 10 -- -- 13 -- 

Calcium, dissolved mg/L 3 100 -- -- 2.9 -- -- 4.1 -- Magnesium, dissolved mg/L 3 100 -- -- .6 -- -- .8 -- Sodium, dissolved mg/L 3 100 -- -- .8 -- -- 1.6 -- Potassium, dissolved mg/L 3 100 -- -- .6 -- -- .8 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 3 100 -- -- 11 -- -- 15 -- Sulfate, dissolved mg/L 5 100 2 .4 1.3 -- -- 2 -- Chloride, dissolved mg/L 5 100 .3 .2 .1 -- -- .3 -- Fluoride, dissolved mg/L 2 100 -- -- .1 -- -- -- -- Silica, dissolved mg/L 3 100 -- -- 4.4 -- -- 8.7 -- Dissolved solids, residue at 180 degrees Celsius mg/L 3 100 -- -- 26 -- -- 29 -- Dissolved solids, sum of constituents mg/L 3 100 -- -- 19 -- -- 28 -- Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 5 100 .05 .02 .033 -- -- .06 -- Nitrogen, ammonia, dissolved as N mg/L **2 0 -- -- <.002 -- -- -- -- Nitrogen, ammonia plus organic, dissolved as N mg/L 2 50 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 5 60 -- -- <.2 -- -- .2 -- Phosphorus, total as P mg/L 5 100 .04 .07 .008 -- -- .013 -- Phosphorus, dissolved as P mg/L 2 50 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **2 100 -- -- .001 -- -- -- -- Aluminum, total as Al μg/L 2 100 -- -- 40 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 10 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 0 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 16 -- -- -- -- 
146 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 

Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, dissolved as Cd μg/L 2 0 -- -- <1 -- -- -- -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 50 -- -- <1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 0 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 5 20 -- -- <1 -- -- <1 -- 

Copper, dissolved as Cu μg/L 5 0 -- -- <1 -- -- <1 -- 

Iron, total as Fe μg/L 5 100 2,200 3,100 480 -- -- 790 -- 

Iron, dissolved as Fe μg/L 5 100 280 50 210 -- -- 280 -- 

Lead, total as Pb μg/L 5 20 -- -- <1 -- -- <1 -- 

Lead, dissolved as Pb μg/L 2 0 -- -- <1 -- -- -- -- 

Manganese, total as Mn μg/L 5 100 60 90 10 -- -- 20 -- 

Manganese, dissolved as Mn μg/L 5 100 5 3 3 -- -- 4 -- 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 50 -- -- <1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 50 -- -- <1 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 0 -- -- <1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 50 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 5 0 -- -- <10 -- -- <10 -- 

Zinc, dissolved as Zn μg/L 5 60 -- -- <3 -- -- <3 -- 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 2.9 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 1.9 -- -- -- -- Sediment, suspended, concentration mg/L 9 100 26 44 2 2 3 8 21 Sediment, suspended, % finer than 0.062 mm % 6 100 75 26 40 -- -- 82 -- Sediment, discharge T/d 7 100 9.7 22 .1 -- -- 1.8 -- 

Table 47. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC10 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 9

per
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 147

Table 48. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC11 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per 

micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe

Specific conductance μS/cm 38 100 65 18 41 48 49 56 87 

pH units 47 100 -- -- 7 7.1 7.3 7.5 7.7 Turbidity NTU 29 100 7.6 17 2.3 2.9 3.4 4.3 5.5 Dissolved oxygen mg/L 40 100 8.9 1 7.2 7.9 8.2 8.8 9.6 Dissolved oxygen saturation % 37 100 100 4.7 88 93 98 100 103 1Hardness as CaCO3 mg/L 26 100 21 5.3 15 16 17 19 25 

Calcium, dissolved mg/L 26 100 5.5 1.4 3.9 4.4 4.5 4.9 6.6 Magnesium, dissolved mg/L 26 100 1.7 .5 1.2 1.3 1.4 1.5 2.1 Sodium, dissolved mg/L 26 100 1.6 .5 1.2 1.2 1.3 1.4 2 Potassium, dissolved mg/L 26 100 .8 .2 .6 .6 .7 .8 .9 Acid-neutralizing capacity, lab as CaCO3 mg/L 26 100 9.8 2.2 5.8 7.2 8.9 9.4 11 Sulfate, dissolved mg/L 39 100 15 6 7.7 9.7 11 13 16 Chloride, dissolved mg/L 39 97 .3 .1 <.1 .2 .2 .3 .3 Fluoride, dissolved mg/L 4 75 -- -- <.1 -- -- .2 -- Silica, dissolved mg/L 26 100 8.1 1.5 6.3 6.6 6.9 7.4 9.4 Dissolved solids, residue at 180 degrees Celsius mg/L 26 100 47 15 28 33 36 43 54 Dissolved solids, sum of constituents mg/L 25 100 41 11 29 32 33 35 48 Nitrite, dissolved as N mg/L 2 0 -- -- <.01 -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 38 100 .06 .02 .024 .04 .05 .06 .07 Nitrogen, ammonia, dissolved as N mg/L **18 50 .005 .008 <.002 <.002 <.002 <.002 .004 Nitrogen, ammonia plus organic, dissolved as N mg/L 2 50 -- -- <.2 -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 38 29 <.2 .1 <.2 <.2 <.2 <.2 .2 Phosphorus, total as P mg/L 36 100 .034 .09 .003 .004 .007 .011 .017 Phosphorus, dissolved as P mg/L 2 0 -- -- <.01 -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L **18 72 .001 .001 <.001 <.001 .001 .001 .002 Aluminum, total as Al μg/L 2 100 -- -- 750 -- -- -- -- 

Aluminum, dissolved as Al μg/L 2 100 -- -- 60 -- -- -- -- 

Antimony, dissolved as Sb μg/L 2 0 -- -- <1 -- -- -- -- 

Arsenic, total as As μg/L 2 0 -- -- <1 -- -- -- -- 

Barium, total as Ba μg/L 2 50 -- -- <100 -- -- -- -- 

Barium, dissolved as Ba μg/L 2 100 -- -- 18 -- -- -- -- 

Beryllium, total as Be μg/L 2 0 -- -- <10 -- -- -- -- 
148 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, dissolved as Be μg/L 2 0 -- -- <1 -- -- -- -- 

Cadmium, total as Cd μg/L 5 20 -- -- <1 -- -- <1 -- 

Cadmium, dissolved as Cd μg/L 3 0 -- -- <1 -- -- <1 -- 

Chromium, total as Cr μg/L 2 50 -- -- <1 -- -- -- -- 

Chromium, dissolved as Cr μg/L 2 0 -- -- <1 -- -- -- -- 

Cobalt, total as Co μg/L 2 100 -- -- 1 -- -- -- -- 

Cobalt, dissolved as Co μg/L 2 50 -- -- <1 -- -- -- -- 

Copper, total as Cu μg/L 43 100 7 8 2 3 4 5 9 

Copper, dissolved as Cu μg/L 39 100 1.9 <1 1 1 2 2 2 

Iron, total as Fe μg/L 43 100 2,200 3,800 230 470 570 840 1,800 

Iron, dissolved as Fe μg/L 39 95 120 78 <3 12 77 120 160 

Lead, total as Pb μg/L 43 30 2 4 <1 <1 <1 <1 1 

Lead, dissolved as Pb μg/L 7 14 -- -- <1 -- -- -- -- 

Manganese, total as Mn μg/L 43 100 160 130 60 70 80 130 180 

Manganese, dissolved as Mn μg/L 39 100 110 54 30 52 62 100 130 

Mercury, total as Hg μg/L 2 0 -- -- <.1 -- -- -- -- 

Molybdenum, total as Mo μg/L 2 100 -- -- 1 -- -- -- -- 

Molybdenum, dissolved as Mo μg/L 2 0 -- -- <1 -- -- -- -- 

Nickel, total as Ni μg/L 2 100 -- -- 4 -- -- -- -- 

Nickel, dissolved as Ni μg/L 2 100 -- -- 1 -- -- -- -- 

Selenium, total as Se μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Silver, dissolved as Ag μg/L 2 0 -- -- <1 -- -- -- -- 

Zinc, total as Zn μg/L 43 100 50 29 <3 20 30 40 60 

Zinc, dissolved as Zn μg/L 39 97 31 18 20 13 17 27 36 

Uranium, natural dissolved μg/L 2 0 -- -- <1 -- -- -- -- 

Carbon, organic total as C mg/L 2 100 -- -- 2.3 -- -- -- -- Carbon, organic dissolved as C mg/L 1 100 -- -- 1.4 -- -- -- -- Sediment, suspended, concentration mg/L 48 100 38 140 4 6 7 8 12 Sediment, suspended, % finer than 0.062 mm % 19 100 68 24 20 31 56 69 80 Sediment, load T/d 48 100 50 215 .2 .28 .43 1.8 5.7 

Table 48. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at GC11 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); **limit not included in computations; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per micrograms per liter; mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 149

Table 49. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at DC1 (fig. 1)[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); μS

centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; mm, millimeter

Property or constituents Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

p

Specific conductance μS/cm 33 100 40 7 30 32 34 38 46 

pH units 43 100 -- -- 7.3 -- -- 7.6 -- Turbidity NTU 29 100 2.4 5.4 .3 .4 .6 .7 1.7 Dissolved oxygen mg/L 27 100 9.1 .8 7.6 8 8.6 8.9 9.6 Dissolved oxygen saturation % 22 100 101 7 88 90 99 100 106 Hardness as CaCO3 mg/L 28 100 14 2.1 11 11 12 13 15 

Calcium, dissolved mg/L 28 100 3.7 .5 3 3.1 3.3 3.7 4 Magnesium, dissolved mg/L 28 100 1 .2 .8 .8 .9 1 1.1 Sodium, dissolved mg/L 28 100 1.7 .2 1.4 1.5 1.5 1.6 1.8 Potassium, dissolved mg/L 28 100 .7 .1 .5 .5 .6 .6 .8 Acid-neutralizing capacity, lab as CaCO3 mg/L 26 100 16 2.1 12 13 14 16 17 Sulfate, dissolved mg/L 44 100 2.5 .4 1.7 2.1 2.2 2.4 2.7 Chloride, dissolved mg/L 44 98 .2 .1 <.1 .1 .2 .2 .3 Fluoride, dissolved mg/L 1 0 -- -- <.1 -- -- -- -- Silica, dissolved mg/L 28 100 9.1 .9 7.3 7.8 8.3 9.2 9.7 Dissolved solids, residue at 180 degrees Celsius mg/L 28 100 36 17 16 22 24 33 45 Nitrite, dissolved as N mg/L -- -- -- -- -- -- -- -- -- Nitrite plus nitrate, dissolved as N mg/L 43 100 .073 .035 .026 .04 .056 .066 .08 Nitrogen, ammonia, dissolved as N mg/L 20 35 .005 .01 <.002 <.002 <.002 <.002 .006 Nitrogen, ammonia plus organic, dissolved as N mg/L -- -- -- -- -- -- -- -- -- Nitrogen, ammonia plus organic, total as N mg/L 43 26 <.2 <.2 <.2 <.2 <.2 <.2 .2 Phosphorus, total as P mg/L 43 100 .015 .023 .001 .003 .005 .006 .011 Phosphorus, dissolved as P mg/L -- -- -- -- -- -- -- -- -- Phosphorus, dissolved orthophosphate as P mg/L 20 70 .001 .001 <.001 <.001 .001 .001 .002 Aluminum, total as Al μg/L -- -- -- -- -- -- -- -- -- 

Aluminum, dissolved as Al μg/L -- -- -- -- -- -- -- -- -- 

Antimony, dissolved as Sb μg/L -- -- -- -- -- -- -- -- -- 

Arsenic, total as As μg/L -- -- -- -- -- -- -- -- -- 

Barium, total as Ba μg/L -- -- -- -- -- -- -- -- -- 

Barium, dissolved as Ba μg/L -- -- -- -- -- -- -- -- -- 

Beryllium, total as Be μg/L -- -- -- -- -- -- -- -- -- 

Beryllium, dissolved as Be μg/L -- -- -- -- -- -- -- -- -- 
150 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Cadmium, total as Cd μg/L -- -- -- -- -- -- -- -- -- 

Cadmium, dissolved as Cd μg/L -- -- -- -- -- -- -- -- -- 

Chromium, total as Cr μg/L -- -- -- -- -- -- -- -- -- 

Chromium, dissolved as Cr μg/L -- -- -- -- -- -- -- -- -- 

Cobalt, total as Co μg/L -- -- -- -- -- -- -- -- -- 

Cobalt, dissolved as Co μg/L -- -- -- -- -- -- -- -- -- 

Copper, total as Cu μg/L 47 34 1 1 <1 <1 <1 <1 1 

Copper, dissolved as Cu μg/L 44 25 1 1 <1 <1 <1 <1 1 

Iron, total as Fe μg/L 47 100 500 890 20 50 70 140 520 

Iron, dissolved as Fe μg/L 44 100 23 12 7 9 14 19 28 

Lead, total as Pb μg/L 46 24 1 1 <1 <1 <1 <1 1 

Lead, dissolved as Pb μg/L 4 0 -- -- <1 -- -- <1 -- 

Manganese, total as Mn μg/L 47 30 16 29 <10 <10 <10 <10 20 

Manganese, dissolved as Mn μg/L 44 20 1 1 <1 <1 <1 <1 1 

Mercury, total as Hg μg/L -- -- -- -- -- -- -- -- -- 

Molybdenum, total as Mo μg/L -- -- -- -- -- -- -- -- -- 

Molybdenum, dissolved as Mo μg/L -- -- -- -- -- -- -- -- -- 

Nickel, total as Ni μg/L -- -- -- -- -- -- -- -- -- 

Nickel, dissolved as Ni μg/L -- -- -- -- -- -- -- -- -- 

Selenium, total as Se μg/L -- -- -- -- -- -- -- -- -- 

Silver, total as Ag μg/L -- -- -- -- -- -- -- -- -- 

Silver, dissolved as Ag μg/L -- -- -- -- -- -- -- -- -- 

Zinc, total as Zn μg/L 47 4 -- -- <10 -- -- <10 -- 

Zinc, dissolved as Zn μg/L 44 41 3 2 <3 <3 <3 3 4 

Uranium, natural dissolved μg/L -- -- -- -- -- -- -- -- -- 

Carbon, organic total as C mg/L -- -- -- -- -- -- -- -- -- Carbon, organic dissolved as C mg/L -- -- -- -- -- -- -- -- -- Sediment, suspended, concentration mg/L 35 94 8 11 <1 1 2 3 10 Sediment, suspended, % finer than 0.062 mm % 12 100 55 18 27 30 43 50 70 Sediment, discharge T/d 35 100 .6 .95 .002 .01 .05 .15 .65 

Table 49. Summary of water-quality statistics for analyses of samples collected, water years 1995–97, at DC1 (fig. 1)—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); μS

centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; %, percentage; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter; mm, millimeter

Property or constituents Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

p
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 151

Table 50. Summary of water-quality statistics for analyses of ground-water samples collected, water years 1995–97[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); °C

microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe

Water temperature °C 7 100 5.6 1.9 3.0 -- -- 5.5 -- 

Specific conductance μS/cm 15 100 170 156 24 52 66 104 220 3

pH units 15 100 -- -- 6.5 6.9 7.0 7.3 7.6 Turbidity NTU 8 100 6 7.7 .2 .4 .9 1.9 9.1 Hardness as CaCO3 mg/L 15 100 77 77 7 16 24 41 96 2

Calcium, dissolved mg/L 15 100 19 17 2.1 4.6 6.9 11 24 Magnesium, dissolved mg/L 15 100 7.1 8.4 .5 1.0 1.9 3.4 9.0 Sodium, dissolved mg/L 15 100 4.3 6.2 1.3 1.4 1.9 2.3 3.4 Potassium, dissolved mg/L 15 100 1.4 1 .4 .7 .9 1.1 1.4 Acid-neutralizing capacity, lab as CaCO3 mg/L 15 100 73 81 6.3 18 23 42 78 1Sulfate, dissolved mg/L 15 100 11 8.1 1.8 3.1 5 8.1 16 Chloride, dissolved mg/L 15 93 2.4 4.6 <.1 .1 .2 .6 3.3 Fluoride, dissolved mg/L 14 86 .3 .3 <.1 <.1 .1 .2 .6 Silica, dissolved mg/L 15 100 9.5 2.7 5.7 6.7 7.3 8.7 12 Dissolved solids, residue at 180 degrees Celsius mg/L 15 100 101 83 28 35 50 67 126 1Dissolved solids, sum of constituents mg/L 15 100 101 86 19 37 46 65 120 2Nitrite, dissolved as N mg/L 13 0 -- -- <.01 -- -- <.01 -- Nitrite plus nitrate, dissolved as N mg/L 15 80 .074 .043 <.05 .014 .032 .08 .11 Nitrogen, ammonia, dissolved as N mg/L 15 13 -- -- <.015 -- -- <.015 -- Nitrogen, ammonia plus organic, dissolved as N mg/L 14 0 -- -- <.2 -- -- <.2 -- Nitrogen, ammonia plus organic, total as N mg/L 10 0 -- -- <.2 -- -- <.2 -- Phosphorus, total as P mg/L 10 70 .012 .011 <.01 .002 .003 .01 .022 Phosphorus, dissolved as P mg/L 14 29 -- -- <.01 -- -- <.01 -- Phosphorus, dissolved orthophosphate as P mg/L 15 13 -- -- <.01 -- -- <.01 -- Aluminum, total as Al μg/L 8 75 40 36 <10 <10 <10 40 60 1

Aluminum, dissolved as Al μg/L 8 75 7 7 <1 <1 1 6 10 

Antimony, dissolved as Sb μg/L 8 0 -- -- <1 -- -- <1 -- 

Arsenic, total as As μg/L 8 0 -- -- <2 -- -- <2 -- 

Barium, total as Ba μg/L 8 0 -- -- <100 -- -- <100 -- 

Barium, dissolved as Ba μg/L 8 100 51 28 14 25 32 47 67 
152 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Beryllium, total as Be μg/L 8 0 -- -- <10 -- -- <10 -- 

Beryllium, dissolved as Be μg/L 8 0 -- -- <1 -- -- <1 -- Cadmium, total as Cd μg/L 9 11 -- -- <1 -- -- <1 -- Cadmium, dissolved as Cd μg/L 9 11 -- -- <1 -- -- <1 -- Chromium, total as Cr μg/L 8 0 -- -- <1 -- -- <1 -- Chromium, dissolved as Cr μg/L 8 0 -- -- <1 -- -- <1 -- Cobalt, total as Co μg/L 8 0 -- -- <1 -- -- <1 -- Cobalt, dissolved as Co μg/L 8 0 -- -- <1 -- -- <1 -- Copper, total as Cu μg/L 9 67 12 12 <1 1 2 5 23 Copper, dissolved as Cu μg/L 14 57 2 3 <1 <1 <1 1 4 Iron, total as Fe μg/L 9 89 660 940 <10 10 60 210 1,200 2Iron, dissolved as Fe μg/L 15 60 60 100 <3 <3 <3 13 41 Lead, total as Pb μg/L 9 56 2 2 <1 1 1 2 4 Lead, dissolved as Pb μg/L 9 11 -- -- <1 -- -- <1 -- Manganese, total as Mn μg/L 9 67 40 70 <10 <10 <10 10 60 Manganese, dissolved as Mn μg/L 15 60 25 60 <1 <1 <1 2 23 Mercury, total as Hg μg/L 8 0 -- -- <.1 -- -- <.1 -- Molybdenum, total as Mo μg/L 8 88 2 1 <1 <1 1 2 2 Molybdenum, dissolved as Mo μg/L 8 38 -- -- <1 -- -- <1 -- Nickel, total as Ni μg/L 8 38 -- -- <1 -- -- <1 -- Nickel, dissolved as Ni μg/L 8 50 1 1 <1 <1 <1 1 2 Selenium, total as Se μg/L 8 0 -- -- <1 -- -- <1 -- Silver, total as Ag μg/L 8 0 -- -- <1 -- -- <1 -- Silver, dissolved as Ag μg/L 8 12 -- -- <1 -- -- <1 -- Zinc, total as Zn μg/L 9 67 970 1,300 <10 40 110 470 1,400 4Zinc, dissolved as Zn μg/L 14 71 640 1,300 <3 <3 <3 4 860 3Uranium, natural dissolved μg/L 8 62 10 23 <1 <1 <1 2 4 Carbon, organic total as C mg/L 8 100 2 1.2 .5 .7 1.5 1.8 2.2 Carbon, organic dissolved as C mg/L 8 100 1.4 .8 .5 .6 .8 1.2 1.9 

Table 50. Summary of water-quality statistics for analyses of ground-water samples collected, water years 1995–97—Continued[--, insufficient data to calculate statistic; statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn (1988); °C

microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; mg/L, milligrams per liter; <, less than; μg/L, micrograms per liter]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

pe
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 153

Table 51. Selected water-quality data collected at road-runoff sites, water years 1995–97[--, no data; >, greater than; <, less than; d, dip method; p, pump sample; dfwm, daily flow-weighted-mean concentration; ft3/s, cubic feet per second; deicer is NaCl histo

suppressant is MgCl2 historically applied; mm, millimeters; Hg, mercury; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per cent

liter; μg/L, micrograms per liter; T/d, tons per day; P, paved; G, gravel]

Site

number

(fig. 2)

Date

(mm/dd/yy)

Time

(hhmm)

Water

temperature

(degrees Celsius)

Air pressure

(mm of Hg)

Discharge,

instantaneous

(ft3/s)

Turbidity

(NTU)

Specific

conductance

(μS/cm at

25 degrees

Celsius)

Oxygen,

dissolved

(mg/L)

pH, field

(standard 

units)

Nitrite,

dissolved

(mg/L as 

CRD1 08/22/95 1200 -- -- 0.007 >1,000 468 -- 7.6 0.01 CRD2 06/10/95 1705 1 500 .144 430 44 10.2 7.3 <.01 CRD3 06/10/95 1510 20 510 .015 >1,000 56 6.7 7.5 <.01 CRD4 05/21/95 1305 4.5 510 .024 >1,000 107 9.9 7.3 <.01 CRD5 08/30/95 1630 -- -- -- >1,000 264 -- 8.5 .01 CRD6 04/06/95 1345 2 530 .008 -- 301 9.2 7.2 <.01 GRD1 08/22/95 1230 -- -- .153 >1,000 19 -- 7.2 <.01 GRD2 06/10/95 1305 4.5 500 .016 680 30 9.5 6.9 <.01 GRD3 08/22/95 1240 -- -- -- >1,000 51 -- 7.3 <.01 GRD4 04/06/95 1655 .5 520 .066 -- 14 9.2 7.2 .002 GRD5 08/23/95 1130 -- -- .004 >1,000 20 -- 7 <.01 CRD7 08/21/96 1540 -- -- .014 61,000 455 -- 6.4 -- CRD7 05/14/97 1700 -- -- .033 1,130 31 -- 7.1 -- GRD6 08/23/96 1235 -- -- .088 32,000 105 -- 8 -- GRD6 05/10/97 1630 -- -- .043 1,430 32 -- 7.3 -- GRD4 08/21/96 1611 -- -- .011 390 24 -- 7 -- CRD8 08/06/97 1528 7.7 -- .005 79 45 -- 7.7 -- GRD8 08/04/97 1600 -- -- .012 10,000 113 -- 8 -- CRD9 10/16/96 1415 -- -- .019 3,400 244 -- 7.1 .06 GRD7 07/09/96 1940 -- -- .035 >1,000 48 -- 6.1 .02 
154 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Table 51. Selected water-quality data collected at road-runoff sites, water years 1995–97—Continued [--, no data; >, greater than; <, less than; d, dip method; p, pump sample; dfwm, daily flow-weighted-mean concentration; ft3/s, cubic feet per second; deicer is NaCl histo

suppressant is MgCl2 historically applied; mm, millimeters; Hg, mercury; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per cent

liter; μg/L, micrograms per liter; T/d, tons per day; P, paved; G, gravel] Site number (fig. 2) Date (mm/dd/yy) Time (hhmm) Nitrogen, ammonia plus organic, total (mg/L as N) Nitrogen, ammonia plus organic, dissolved (mg/L as N) Phosphorus, total (mg/L as P) Phosphorus, dissolved (mg/L as P) Phosphorus, ortho, dissolved (mg/L as P) Hardness, total (mg/L as CaCO3) Calcium, dissolved (mg/L as Ca) Magnesium

dissolved (mg/L as Mg

CRD1 08/22/95 1200 0.9 <0.2 1.5 <0.01 <0.01 160 20 26 CRD2 06/10/95 1705 .2 .2 .05 .02 .01 18 3.5 2.3 CRD3 06/10/95 1510 .6 <.2 .4 .01 .02 17 3.3 2.1 CRD4 05/21/95 1305 <.2 <.2 .03 <.01 <.01 49 11 5.1 CRD5 08/30/95 1630 6.1 <.2 6 .02 <.01 99 15 15 CRD6 04/06/95 1345 .3 <.2 .08 <.01 <.01 6 1.9 .4 GRD1 08/22/95 1230 .7 <.2 .33 .01 .01 6 1.9 .35 GRD2 06/10/95 1305 .3 .2 .07 .03 .03 13 3.4 1.1 GRD3 08/22/95 1240 .6 <.2 .53 <.01 <.01 18 5.3 1.1 GRD4 04/06/95 1655 <.2 <.2 .044 .03 <.01 5 1.5 .25 GRD5 08/23/95 1130 4.7 <.2 4 <.01 .02 8 2.4 .38 CRD7 08/21/96 1540 15 -- -- -- -- 130 18 21 CRD7 05/14/97 1700 .3 -- .024 -- .003 -- -- -- GRD6 08/23/96 1235 3.5 -- .23 -- -- 34 8.1 3.3 GRD6 05/10/97 1630 .4 -- .17 -- .01 -- -- -- GRD4 08/21/96 1611 -- -- -- -- -- 6 1.7 .38 CRD8 08/06/97 1528 .3 -- .055 -- .003 1 .2 .06 GRD8 08/04/97 1600 5 -- 3 -- .019 45 15 2 CRD9 10/16/96 1415 2.1 .7 1.3 .1 .11 16 5.2 .66 GRD7 07/09/96 1940 24 .9 7.2 .25 .22 11 3.4 .72 
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 155

Table 51. Selected water-quality data collected at road-runoff sites, water years 1995–97—Continued[--, no data; >, greater than; <, less than; d, dip method; p, pump sample; dfwm, daily flow-weighted-mean concentration; ft3/s, cubic feet per second; deicer is NaCl histo

suppressant is MgCl2 historically applied; mm, millimeters; Hg, mercury; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per cent

liter; μg/L, micrograms per liter; T/d, tons per day; P, paved; G, gravel]

Site

number

(fig. 2)

Date

(mm/dd/yy)

Time

(hhmm)

Acid-neutralizing

capacity, water,

unfiltered, titration

to 4.5, lab

(mg/L as CaCO3)

Sulfate,

dissolved,

(mg/L as SO4)

Chloride,

dissolved

(mg/L as Cl)

Fluoride,

dissolved

(mg/L as F)

Silica,

dissolved

(mg/L as SiO2)

Solids,

residue on

evaporation at

180 degrees

Celsius, dissolved

(mg/L)

Dissolved

solids,

sum of

constituents

(mg/L)

Aluminum

total

(μg/L as A

CRD1 08/22/95 1200 19 6.1 120 0.3 1.9 286 206 42,000 CRD2 06/10/95 1705 14 1.3 4.3 .1 2.5 39 25 6,600 CRD3 06/10/95 1510 23 1.1 8.9 .1 4 34 39 120,000 CRD4 05/21/95 1305 43 4.4 5.8 <.1 7.1 70 64 32,000 CRD5 08/30/95 1630 42 5.8 60 .2 1.4 166 134 110,000 CRD6 04/06/95 1345 10 3.2 79 <.1 1.2 149 147 12,000 GRD1 08/22/95 1230 16 .4 .5 .2 1.4 11 18 130,000 GRD2 06/10/95 1305 13 1.4 1.5 .2 3.9 34 22 17,000 GRD3 08/22/95 1240 22 2.6 .5 .2 8.7 38 36 41,000 GRD4 04/06/95 1655 4.8 .4 .6 .04 .62 -- 7 550 GRD5 08/23/95 1130 23 .6 .4 <.1 1.2 18 21 50,000 CRD7 08/21/96 1540 14 6.3 120 -- 4.7 276 210 -- CRD7 05/14/97 1700 -- 1.2 4 -- -- -- -- -- GRD6 08/23/96 1235 35 3 14 -- 2.6 58 61 -- GRD6 05/10/97 1630 -- 1.1 1.1 -- -- -- -- -- GRD4 08/21/96 1611 5.4 1.4 .8 -- .8 16 11 -- CRD8 08/06/97 1528 15 1.7 3.1 .1 2.4 36 27 -- GRD8 08/04/97 1600 59 2.3 .8 .4 4.5 74 65 -- CRD9 10/16/96 1415 36 16 40 -- 1.4 150 123 -- GRD7 07/09/96 1940 37 1.6 2.4 -- 4.1 70 41 -- 
156 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Table 51. Selected water-quality data collected at road-runoff sites, water years 1995–97—Continued [--, no data; >, greater than; <, less than; d, dip method; p, pump sample; dfwm, daily flow-weighted-mean concentration; ft3/s, cubic feet per second; deicer is NaCl histo

suppressant is MgCl2 historically applied; mm, millimeters; Hg, mercury; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per cent

liter; μg/L, micrograms per liter; T/d, tons per day; P, paved; G, gravel] Site number (fig. 2) Date (mm/dd/yy) Time (hhmm) Arsenic, total

(μg/L as As)

Barium,

total

(μg/L as Ba)

Barium,

dissolved

(μg/L as Ba)

Beryllium,

total

(μg/L as Be)

Beryllium,

dissolved

(μg/L as Be)

Cadmium,

total

(μg/L as Cd)

Cadmium,

dissolved

(μg/L as Cd)

Chromium,

total

(μg/L as Cr)

CRD1 08/22/95 1200 <1 700 48 <10 <1 <1 <1 120 CRD2 06/10/95 1705 <1 100 16 <10 <1 <1 <1 19 CRD3 06/10/95 1510 <1 2,500 18 <10 <1 2 <1 140 CRD4 05/21/95 1305 1 700 41 <10 <1 <1 <1 32 CRD5 08/30/95 1630 <2 2,600 48 <10 <1 4 <1 150 CRD6 04/06/95 1345 <1 200 13 <10 <1 <1 <1 22 GRD1 08/22/95 1230 1 2,100 9 <10 <1 2 <1 100 GRD2 06/10/95 1305 <1 200 15 <10 <1 <1 <1 22 GRD3 08/22/95 1240 <1 1,000 20 <10 <1 3 <1 97 GRD4 04/06/95 1655 <1 <100 7 <10 <1 <1 <1 <1 GRD5 08/23/95 1130 2 1,800 10 <10 <1 2 <1 140 CRD7 08/21/96 1540 -- -- -- -- -- -- -- -- CRD7 05/14/97 1700 -- -- -- -- -- -- -- -- GRD6 08/23/96 1235 -- -- -- -- -- -- -- -- GRD6 05/10/97 1630 -- -- -- -- -- -- -- -- GRD4 08/21/96 1611 -- -- -- -- -- <1 -- -- CRD8 08/06/97 1528 -- -- -- -- -- -- -- -- GRD8 08/04/97 1600 -- -- -- -- -- -- -- -- CRD9 10/16/96 1415 -- -- -- -- -- 7 <1 200 GRD7 07/09/96 1940 -- -- -- -- -- 3 -- 89 
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 157

Table 51. Selected water-quality data collected at road-runoff sites, water years 1995–97—Continued[--, no data; >, greater than; <, less than; d, dip method; p, pump sample; dfwm, daily flow-weighted-mean concentration; ft3/s, cubic feet per second; deicer is NaCl histo

suppressant is MgCl2 historically applied; mm, millimeters; Hg, mercury; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per cent

liter; μg/L, micrograms per liter; T/d, tons per day; P, paved; G, gravel]

Site

number

(fig. 2)

Date

(mm/dd/yy)

Time

(hhmm)

Cobalt,

dissolved

(μg/L as Co)

Copper,

total

(μg/L as Cu)

Copper,

dissolved

(μg/L as Cu)

Iron,

total

(μg/L as Fe)

Iron,

dissolved

(μg/L as Fe)

Lead,

total

(μg/L as Pb)

Lead,

dissolved

(μg/L as Pb)

Manganese,

total

(μg/L as Mn)

CRD1 08/22/95 1200 <1 75 <1 59,000 50 37 <1 3,900 CRD2 06/10/95 1705 <1 10 1 220,000 230 6 <1 380 CRD3 06/10/95 1510 <1 250 1 220,000 1,100 120 <1 9,500 CRD4 05/21/95 1305 <1 72 3 58,000 350 20 <1 1,400 CRD5 08/30/95 1630 <1 290 2 280,000 34 320 <1 13,000 CRD6 04/06/95 1345 <1 44 1 32,000 46 49 <1 980 GRD1 08/22/95 1230 <1 100 <1 140,000 290 200 <1 7,300 GRD2 06/10/95 1305 <1 25 1 32,000 370 13 <1 630 GRD3 08/22/95 1240 <1 61 2 56,000 150 36 <1 1,400 GRD4 04/06/95 1655 <1 <1 <1 0,780 46 2 <1 60 GRD5 08/23/95 1130 <1 72 <1 75,000 110 460 <1 3,400 CRD7 08/21/96 1540 -- 310 1 500,000 20 440 -- 30,000 CRD7 05/14/97 1700 -- 18 <1 23,000 220 13 -- 840 GRD6 08/23/96 1235 -- 560 2 580,000 110 610 -- 24,000 GRD6 05/10/97 1630 -- 37 1 72,000 160 42 -- 1,700 GRD4 08/21/96 1611 -- 14 1 16,000 25 41 <1 510 CRD8 08/06/97 1528 -- 6 2 3,000 55 14 -- 44 GRD8 08/04/97 1600 -- 51 2 85,000 17 160 -- 2,700 CRD9 10/16/96 1415 -- 600 -- 170,000 71 1,200 <1 8,000 GRD7 07/09/96 1940 -- 53 3 130,000 520 240 -- -- 
158 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Table 51. Selected water-quality data collected at road-runoff sites, water years 1995–97—Continued [--, no data; >, greater than; <, less than; d, dip method; p, pump sample; dfwm, daily flow-weighted-mean concentration; ft3/s, cubic feet per second; deicer is NaCl histo

suppressant is MgCl2 historically applied; mm, millimeters; Hg, mercury; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per cent

liter; μg/L, micrograms per liter; T/d, tons per day; P, paved; G, gravel] Site number (fig. 2) Date (mm/dd/yy) Time (hhmm) Molybdenum, total

(μg/L as Mo)

Molybdenum,

dissolved

(μg/L as Mo)

Nickel,

total

(μg/L as Ni)

Nickel,

dissolved

(μg/L as Ni)

Selenium,

total

(μg/L as Se)

Silver,

total

(μg/L as Ag)

Silver,

dissolved

(μg/L as Ag)

Zinc,

total

(μg/L as Zn

CRD1 08/22/95 1200 1 1 130 1 <2 <1 <1 180 CRD2 06/10/95 1705 <1 <1 15 1 <1 <1 <1 50 CRD3 06/10/95 1510 <1 <1 140 <1 2 <1 <1 740 CRD4 05/21/95 1305 <1 <1 23 2 <1 <1 <1 280 CRD5 08/30/95 1630 1 1 120 <1 <1 <1 <1 900 CRD6 04/06/95 1345 1 1 16 <1 <1 <1 <1 190 GRD1 08/22/95 1230 <1 <1 95 <1 <10 <1 <1 550 GRD2 06/10/95 1305 <1 <1 13 <1 <1 <1 <1 110 GRD3 08/22/95 1240 2 2 70 <1 <1 <1 <1 200 GRD4 04/06/95 1655 <1 <1 <1 <1 <1 <1 <1 <10 GRD5 08/23/95 1130 <1 <1 78 <1 5 <1 <1 490 CRD7 08/21/96 1540 -- -- -- -- -- -- -- 1,900 CRD7 05/14/97 1700 -- -- -- -- -- -- -- 80 GRD6 08/23/96 1235 -- -- -- -- -- -- -- 2,200 GRD6 05/10/97 1630 -- -- -- -- -- -- -- 264 GRD4 08/21/96 1611 -- -- -- -- -- -- -- 160 CRD8 08/06/97 1528 -- -- -- -- -- -- -- 45 GRD8 08/04/97 1600 -- -- -- -- -- -- -- 434 CRD9 10/16/96 1415 -- -- 130 -- -- -- -- 2,200 GRD7 07/09/96 1940 -- -- 67 -- -- -- -- 420 
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 159

Table 51. Selected water-quality data collected at road-runoff sites, water years 1995–97—Continued[--, no data; >, greater than; <, less than; d, dip method; p, pump sample; dfwm, daily flow-weighted-mean concentration; ft3/s, cubic feet per second; deicer is NaCl histo

suppressant is MgCl2 historically applied; mm, millimeters; Hg, mercury; ft3/s, cubic feet per second; NTU, nephelometric turbidity units; μS/cm, microsiemens per cen

liter; μg/L, micrograms per liter; T/d, tons per day; P, paved; G, gravel]

Site

number

(fig. 2)

Date

(mm/dd/yy)

Time

(hhmm)

Carbon,

organic, total

(mg/L as C)

Carbon,

organic,

dissolved

(mg/L as C)

Oil and

grease,

total

(mg/L)

Sediment,

suspended,

concentration

(mg/L)

Sediment,

suspended,

percent

finer than0.062 mm

Sediment,

suspended,

discharge

(T/d)

Sampling

method

Precipitation

type

CRD1 08/22/95 1200 31 3.2 -- 10,600 35 0.2 d rain CRD2 06/10/95 1705 7.1 -- <1 7,360 90 2.86 d snow CRD3 06/10/95 1510 16 -- <1 7,280 90 .29 d snow CRD4 05/21/95 1305 11 -- <1 4,720 45 .31 d snow CRD5 08/30/95 1630 130 3.7 -- 8,190 88 -- d rain CRD6 04/06/95 1345 10 2.3 <1 680 91 .015 d snow GRD1 08/22/95 1230 140 2.4 -- 30,800 37 12.7 d rain GRD2 06/10/95 1305 8.9 -- <1 550 84 .024 d snow GRD3 08/22/95 1240 12 2.4 -- 1,120 100 -- d rain GRD4 04/06/95 1655 4.7 3.8 <1 66 37 .012 d snow GRD5 08/23/95 1130 140 3.5 -- 6,190 42 .067 d rain CRD7 08/21/96 1540 -- -- -- 38,800 100 1.47 p rain CRD7 05/14/97 1700 -- -- -- 973 91 .087 d snow GRD6 08/23/96 1235 -- -- -- 24,800 100 5.89 p rain GRD6 05/10/97 1630 -- -- -- 2,040 97 .24 p, dfwm snow GRD4 08/21/96 1611 -- -- -- 492 -- .015 p rain CRD8 08/06/97 1528 -- -- -- 34 95 .0005 d rain GRD8 08/04/97 1600 -- -- -- 3,360 70 .11 d rain CRD9 10/16/96 1415 -- -- -- -- -- -- d rain GRD7 07/09/96 1940 -- -- -- -- -- -- d rain 
160 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Table 52. Summary of water-quality statistics for analyses of selected samples collected, water years 1995–97, at road-runoff sites durin

[--, insufficient data to calculate statistic; * indicates statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn 

second; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; >, greater than; mg/L, milligrams per liter; <, less than; μg/L, mi

mm, millimeters; T/d, tons per day] Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

Discharge ft3/s 8 100 0.044 0.045 0.008 0.013 0.016 0.029 0.144 

Specific conductance μS/cm 8 100 77 95 14 25 31 38 69 

pH units 8 100 -- -- 6.9 -- -- 7.2 -- Turbidity NTU 6 100 -- -- 430 -- -- >1,000 -- Dissolved oxygen mg/L 6 100 9.1 1.2 6.7 -- -- 9.4 -- Hardness as CaCO3 mg/L 6 100 18 16 5 -- -- 15 -- 

Calcium, dissolved mg/L 6 100 4.1 3.5 1.5 -- -- 3.4 -- Magnesium, dissolved mg/L 6 100 1.9 1.8 .2 -- -- 1.6 -- Sodium, dissolved mg/L 6 100 10 22 .5 -- -- 1.4 -- Potassium, dissolved mg/L 6 100 1.3 .7 .6 -- -- 1.2 -- Acid-neutralizing capacity, lab as CaCO3 mg/L 6 100 18 14 4.8 -- -- 14 -- Sulfate, dissolved mg/L 8 100 1.8 1.3 .4 .9 1.1 1.2 1.8 Chloride, dissolved mg/L 8 100 13 27 .6 1.0 1.4 4.2 6.6 Fluoride, dissolved mg/L 6 67 -- -- <.1 -- -- .1 -- Silica, dissolved mg/L 6 100 3.2 2.3 .6 -- -- 3.2 -- Dissolved solids, residue at 180 degrees Celsius mg/L 5 100 65 49 34 -- -- 39 -- Dissolved solids, sum of constituents mg/L 6 100 51 51 7 -- -- 32 -- Nitrite, dissolved as N mg/L 6 17 -- -- <.01 -- -- <.01 -- Nitrite plus nitrate, dissolved as N mg/L *8 88 .11 .091 .015 .015 .036 .095 .12 Nitrogen, ammonia, dissolved as N mg/L 8 100 .037 .023 .010 .015 .019 .036 .050 Nitrogen, ammonia plus organic, dissolved as N mg/L 6 33 -- -- <.2 -- -- <.2 -- Nitrogen, ammonia plus organic, total as N mg/L *8 75 .3 .15 <.2 <.2 <.2 .3 .4 Phosphorus, total as P mg/L 8 100 .110 .130 .024 .028 .041 .060 .10 Phosphorus, dissolved as P mg/L 6 67 -- -- <.01 -- -- .02 -- Phosphorus, dissolved orthophosphate as P mg/L *8 62 .01 .01 .003 .002 .003 .007 .018 Aluminum, total as Al μg/L 6 100 31,000 45,000 550 -- -- 14,000 -- Aluminum, dissolved as Al μg/L 6 100 170 120 50 -- -- 150 -- Antimony, dissolved as Sb μg/L 6 0 -- -- <1 -- -- <1 -- Arsenic, total as As μg/L 6 17 -- -- <1 -- -- <1 -- Barium, total as Ba μg/L 6 83 -- -- 100 -- -- 200 -- Barium, dissolved as Ba μg/L 6 100 18 12 7 -- -- 16 -- Beryllium, total as Be μg/L 6 0 -- -- <10 -- -- <10 -- 
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 161

Beryllium, dissolved as Be μg/L 6 0 -- -- <1 -- -- <1 -- 

Cadmium, total as Cd μg/L 6 17 -- -- <1 -- -- <1 -- 

Cadmium, dissolved as Cd μg/L 6 0 -- -- <1 -- -- <1 -- 

Chromium, total as Cr μg/L 6 83 -- -- <1 -- -- 22 -- 

Chromium, dissolved as Cr μg/L 6 17 -- -- <1 -- -- <1 -- 

Cobalt, total as Co μg/L 6 83 -- -- <1 -- -- 10 -- 

Cobalt, dissolved as Co μg/L 6 0 -- -- <1 -- -- <1 -- 

Copper, total as Cu μg/L *8 88 57 81 <1 3 12 31 65 

Copper, dissolved as Cu μg/L *8 75 1 .8 <1 <1 1 1 1 

Iron, total as Fe μg/L 8 100 82,000 88,000 780 16,000 30,000 45,000 110,000 

Iron, dissolved as Fe μg/L 8 100 320 340 46 46 130 220 360 

Lead, total as Pb μg/L 8 100 33 39 2 5 11 16 44 

Lead, dissolved as Pb μg/L 6 0 -- -- <1 -- -- <1 -- 

Manganese, total as Mn μg/L 8 100 1,900 3,100 60 280 570 910 1,500 

Manganese, dissolved as Mn μg/L 8 100 40 21 4 18 25 46 51 

Mercury, total as Hg μg/L 6 17 -- -- <.1 -- -- <.1 -- 

Molybdenum, total as Mo μg/L 6 17 -- -- <1 -- -- <1 -- 

Molybdenum, dissolved as Mo μg/L 6 17 -- -- <1 -- -- <1 -- 

Nickel, total as Ni μg/L 6 83 -- -- <1 -- -- 16 -- 

Nickel, dissolved as Ni μg/L 6 33 -- -- <1 -- -- <1 -- 

Selenium, total as Se μg/L 6 17 -- -- <1 -- -- <1 -- 

Silver, total as Ag μg/L 6 0 -- -- <1 -- -- <1 -- 

Silver, dissolved as Ag μg/L 6 0 -- -- <1 -- -- <1 -- 

Zinc, total as Zn μg/L *8 88 220 230 <10 <3 <3 150 280 

Zinc, dissolved as Zn μg/L *8 75 3 .9 <3 <3 <3 3 4 

Uranium, natural dissolved μg/L 6 0 -- -- <1 -- -- <1 -- 

Carbon, organic total as C mg/L 6 100 9.6 3.8 4.7 -- -- 9.4 -- Carbon, organic dissolved as C mg/L 2 100 -- -- 2.3 -- -- 3 -- Oil and grease, total mg/L 6 0 -- -- <1 -- -- <1 -- Sediment, suspended, concentration mg/L 8 100 2,960 3,050 66 405 648 1,510 5,360 Sediment, suspended, % finer than 0.062 mm % 8 100 78 23 37 43 74 90 91 Sediment, discharge T/d 8 100 .48 .97 .012 .014 .021 .16 .30 

Table 52. Summary of water-quality statistics for analyses of selected samples collected, water years 1995–97, at road-runoff sites durin[--, insufficient data to calculate statistic; * indicates statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn 

second; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; >, greater than; mg/L, milligrams per liter; <, less than; μg/L, mi

mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 
162 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Table 53. Summary of water-quality statistics for analyses of selected samples collected, water years 1995–97, at road-runoff sites duri

[--, insufficient data to calculate statistic; *, indicates statistics estimated using robust log-probability regression technique for censored data described in Helsel and Cohn 

second; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; >, greater than; mg/L, milligrams per liter; <, less than; μg/L, mi

mm, millimeters; T/d, tons per day] Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 

Discharge ft3/s 10 100 0.035 0.049 0.004 0.005 0.008 0.013 0.031 

Specific conductance μS/cm 12 100 155 165 19 20 40 78 249 pH units 12 100 -- -- 6.1 -- -- 7.2 -- Turbidity NTU 12 100 -- -- 79. -- -- >1,000 -- Dissolved oxygen mg/L 0 -- -- -- -- -- -- -- -- Hardness as CaCO3 mg/L 12 100 44 54 1 6 8 17 58 

Calcium, dissolved mg/L 12 100 8.0 7.1 .2 1.7 2.3 5.2 15 Magnesium, dissolved mg/L 12 100 5.9 9.2 .06 .4 .4 .9 6.2 Sodium, dissolved mg/L 12 100 7.2 9.9 .2 .3 1 2.6 9.7 Potassium, dissolved mg/L 12 100 2.9 2 .5 .6 1 2.8 4.6 Acid-neutralizing capacity, lab as CaCO3 mg/L 12 100 27 15 5.4 14 16 22 36 Sulfate, dissolved mg/L 12 100 4.0 4.3 .4 .7 1.6 2.4 5.9 Chloride, dissolved mg/L 12 100 30 46 .4 .5 .7 2.8 45 Fluoride, dissolved mg/L 7 86 -- -- <.1 -- -- .2 -- Silica, dissolved mg/L 12 100 2.9 2.3 .8 1.2 1.4 2.2 4.2 Dissolved solids, residue at 180 degrees Celsius mg/L 12 100 100 98 11 16 32 64 154 Dissolved solids, sum of constituents mg/L 12 100 79 72 11 18 26 51 126 Nitrite, dissolved as N mg/L 7 57 -- -- <.01 -- -- .01 -- Nitrite plus nitrate, dissolved as N mg/L 11 100 .42 .35 .055 .10 .16 .29 .62 Nitrogen, ammonia, dissolved as N mg/L *9 78 .06 .06 <.002 .01 .023 .04 .08 Nitrogen, ammonia plus organic, dissolved as N mg/L 7 29 -- -- <.2 -- -- <.2 -- Nitrogen, ammonia plus organic, total as N mg/L 11 100 5.7 7.4 .3 .6 .8 3.5 5.6 Phosphorus, total as P mg/L 10 100 2.4 2.6 .055 .21 .38 1.4 3.8 Phosphorus, dissolved as P mg/L 7 57 -- -- <.01 -- -- .01 -- Phosphorus, dissolved orthophosphate as P mg/L *9 78 .043 .075 .003 .001 .003 .01 .065 Aluminum, total as Al μg/L 5 100 75,000 42,000 41,000 -- -- 50,000 -- 

Aluminum, dissolved as Al μg/L 5 100 130 100 30 -- -- 140 -- 

Antimony, dissolved as Sb μg/L 5 0 -- -- <1 -- -- <1 -- 

Arsenic, total as As μg/L 5 40 -- -- <1 -- -- <1 -- 

Barium, total as Ba μg/L 5 100 1,600 780 700 -- -- 1,800 -- 

Barium, dissolved as Ba μg/L 5 100 27 20 9 -- -- 20 -- 

Beryllium, total as Be μg/L 5 0 -- -- <10 -- -- <10 -- 
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 163

Beryllium, dissolved as Be μg/L 5 0 -- -- <1 -- -- <1 -- 

Cadmium, total as Cd μg/L *8 75 3 2 <1 1 1 2 4 

Cadmium, dissolved as Cd μg/L 6 0 -- -- <1 -- -- <1 -- 

Chromium, total as Cr μg/L 7 100 130 39 89 -- -- 120 -- 

Chromium, dissolved as Cr μg/L 5 0 -- -- <1 -- -- <1 -- 

Cobalt, total as Co μg/L 5 100 70 35 20 -- -- 80 -- 

Cobalt, dissolved as Co μg/L 5 0 -- -- <1 -- -- <1 -- 

Copper, total as Cu μg/L 12 100 180 210 6 18 52 74 300 

Copper, dissolved as Cu μg/L *11 73 2 1 <1 1 1 2 2 

Iron, total as Fe μg/L 12 100 170,000 190,000 3,000 20,000 58,000 110,000 200,000 4

Iron, dissolved as Fe μg/L 12 100 120 150 17 20 32 63 120 

Lead, total as Pb μg/L 12 100 310 340 14 36 40 220 440 

Lead, dissolved as Pb μg/L 7 0 -- -- <1 -- -- <1 -- 

Manganese, total as Mn μg/L 11 100 8,600 10,000 44 510 2,000 3,900 10,000 

Manganese, dissolved as Mn μg/L *12 92 210 480 <1 1 5 22 260 

Mercury, total as Hg μg/L 5 60 -- -- <.1 -- -- .1 -- 

Molybdenum, total as Mo μg/L 5 60 -- -- <1 -- -- 1 -- 

Molybdenum, dissolved as Mo μg/L 5 60 -- -- <1 -- -- 1 -- 

Nickel, total as Ni μg/L 7 100 99 28 67 -- -- 95 -- 

Nickel, dissolved as Ni μg/L 5 20 -- -- <1 -- -- <1 -- 

Selenium, total as Se μg/L 5 20 -- -- <1 -- -- -- -- 

Silver, total as Ag μg/L 5 0 -- -- <1 -- -- <1 -- 

Silver, dissolved as Ag μg/L 5 0 -- -- <1 -- -- <1 -- 

Zinc, total as Zn μg/L 12 100 810 810 40 160 200 460 1,200 

Zinc, dissolved as Zn μg/L *12 58 8 13 <1 <1 <1 2 10 

Uranium, natural dissolved μg/L 5 20 -- -- <1 -- -- <1 -- 

Carbon, organic total as C mg/L 8 100 83 63 5.6 10 26 94 140 Carbon, organic dissolved as C mg/L 5 100 3.0 .6 2.4 -- -- 3.2 -- Oil and grease, total mg/L 0 -- -- -- -- -- -- -- -- Sediment, suspended, concentration mg/L 10 100 12,400 14,000 34 446 1,680 7,190 21,200 Sediment, suspended, % finer than 0.062 mm % 9 100 74 29 35 37 42 88 100 Sediment, discharge T/d 8 100 2.6 4.6 .0005 .01 .05 .16 2.6 

Table 53. Summary of water-quality statistics for analyses of selected samples collected, water years 1995–97, at road-runoff sites durin[--, insufficient data to calculate statistic; *, indicates statistics estimated using robust log-probability regression technique for censored data described in Helsel and Coh

second; μS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; >, greater than; mg/L, milligrams per liter; <, less than; μg/L, m

mm, millimeters; T/d, tons per day]

Property or constituent Units Number of samples Percent detections Mean Standard deviation Min- imum 10th percentile 25th percentile Median 75th percentile 
164 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 Table 54. Drainage-feature evaluation data [--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside d

ditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prrefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel] Site number (fig. 45) Latitude (degrees minutes seconds) Longitude (degrees minutes seconds) Altitude (feet) Type of feature Contributing ditch length (feet) Ditch length from other upslope culverts (feet) Predominant buffer-zone vegetation Slope material Predominant buffer-zone grain size Cutslop

CCD1 39 35 57 105 42 35 11,512 culvert 790 -- alpine tundra colluvium, soil medium moderat

some v

CCD2 39 36 01 105 42 37 11,486 roadside ditch 440 -- conifer colluvium medium moderat

some v

CCD3 39 35 58 105 42 33 11,459 culvert 275 790 willow colluvium medium highly 

little v

CCD4 39 35 57 105 42 28 11,420 roadside ditch 571 -- willow colluvium, soil medium highly 

little v

CCD5 39 35 59 105 42 31 11,410 culvert 480 790+275 conifer colluvium, soil medium highly 

little v

CCD6 39 36 08 105 42 36 11,302 culvert 728 440 conifer colluvium, soil medium moderat

some v

CCD7 39 36 10 105 42 39 11,295 culvert 526 -- willow colluvium, soil medium highly 

little v

CCD8 39 36 12 105 42 40 11,280 culvert 240 -- willow colluvium, soil medium highly 

little v

CCD9 39 36 16 105 42 45 11,266 culvert 475 -- conifer colluvium, talus coarse highly 

little v

CCD10 39 36 20 105 42 48 11,187 roadside ditch 665 -- conifer colluvium, soil medium highly 

little v

CCD11 39 36 18 105 42 43 11,144 culvert 565 -- conifer colluvium medium highly 

little v

CCD12 39 36 17 105 42 41 11,128 roadside ditch 254 475 conifer colluvium, soil medium highly 

little v

CCD13 39 36 21 105 42 45 11,108 culvert 492 565 willow colluvium medium highly 

little v

CCD14 39 36 27 105 42 50 11,020 culvert 668 -- conifer colluvium, soil medium moderat

some v

CCD15 39 36 31 105 42 55 10,974 roadside ditch 720 -- conifer colluvium, soil medium moderat

some v

CCD16 39 36 34 105 42 54 10,908 roadside ditch 290 -- conifer colluvium, soil medium highly 

little v
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 165

CCD17 39 36 34 105 43 00 10,882 culvert 579 720 conifer colluvium, soil medium highly 

little ve

CCD18 39 36 34 105 43 04 10,872 culvert 416 -- conifer soil fine highly 

little ve

CCD19 39 36 44 105 43 01 10,784 roadside ditch 610 -- willow colluvium, soil medium moderate

some ve

CCD20 39 36 46 105 43 01 10,777 culvert 305 -- willow soil fine low er

reveg

CCD21 39 36 48 105 43 00 10,764 culvert 197 -- willow soil fine moderate

some ve

CCD22 39 36 53 105 42 58 10,734 culvert 556 -- willow soil, litter fine moderate

some ve

CCD23 39 37 02 105 42 56 10,688 culvert 885 -- willow soil fine moderate

some ve

CCD24 39 37 08 105 42 54 10,662 culvert 903 -- willow soil fine moderate

some ve

CCD25 39 37 16 105 42 51 10,636 culvert 211 -- willow soil, litter fine moderate

some ve

CCD26 39 37 22 105 42 49 10,610 culvert 412 -- grass soil, litter fine moderate

some ve

CCD27 39 37 25 105 42 47 10,600 culvert 255 -- grass soil fine moderate

some ve

CCD28 39 37 28 105 42 46 10,583 culvert 220 -- grass colluvium medium moderate

some ve

CCD29 39 37 39 105 42 45 10,508 culvert 1270 -- willow soil fine moderate

some ve

CCD30 39 37 42 105 42 43 10,492 culvert 79 -- willow colluvium medium moderate

some ve

CCD31 39 38 00 105 42 39 10,393 culvert 777 -- conifer soil fine low er

reveg

CCD32 39 38 07 105 42 36 10,351 roadside ditch, 

bridge crossing

611 -- willow colluvium medium low er

reveg

CCD33 39 38 06 105 42 35 10,347 roadside ditch 297 -- willow soil fine moderate

some ve

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslope 
166 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 CCD34 39 38 21 105 42 28 10,216 roadside ditch 1495 -- willow soil fine moderate

some ve

CCD35 39 38 31 105 42 28 10,206 culvert 988 -- conifer colluvium medium moderate

some ve

CCD36 39 38 52 105 42 28 10,081 culvert 2350 -- conifer soil, litter fine moderate

some ve

CCD37 39 39 05 105 42 28 10,013 roadside ditch 979 -- willow colluvium, soil medium moderate

some ve

CCD38 39 39 05 105 42 29 10,016 culvert (north and south ditches) 1794 -- willow colluvium, soil medium moderate

some ve

CCD39 39 39 23 105 42 31 10,045 culvert 467 -- grass talus, colluvium, soil coarse highly 

little ve

CCD40 39 39 26 105 42 31 10,075 culvert 257 -- grass talus, colluvium coarse highly 

little ve

CCD41 39 39 49 105 42 22 10,055 culvert 178 -- grass talus, colluvium coarse moderate

some ve

CCD42 39 39 59 105 42 14 9,963 culvert 1167 -- grass talus, soil coarse moderate

some ve

CCD43 39 40 06 105 42 13 9,931 culvert 1388 -- conifer talus, colluvium coarse highly 

little ve

CCD44 39 40 29 105 42 22 9,917 culvert 105 -- grass talus coarse moderate

some ve

CCD45 39 40 32 105 42 21 9,927 culvert 136 -- grass talus coarse moderate

some ve

CCD46 39 40 46 105 42 11 9,809 roadside ditch 958 -- grass rock, talus, 

colluvium

coarse highly 

little ve

CCD47 39 40 40 105 42 09 9,776 culvert 731 -- grass rock, talus, 

colluvium

coarse moderate

some ve

CCD48 39 40 36 105 41 59 9,727 roadside ditch 932 -- conifer talus, colluvium coarse highly 

little ve

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslop
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 167

CCD49 39 40 42 105 42 03 9,655 roadside ditch 754 -- conifer colluvium medium highly 

little ve

CCD50 39 40 52 105 42 10 9,547 roadside ditch 1134 -- conifer colluvium, soil,

litter

medium low er

reveg

CCD51 39 40 59 105 42 10 9,501 roadside ditch 815 -- none talus, colluvium coarse moderate

some ve

CCD52 39 40 58 105 42 09 9,478 culvert 105 -- aspen colluvium medium moderate

some ve

CCD53 39 40 56 105 42 07 9,442 roadside ditch 170 -- conifer soil, litter fine moderate

some ve

CCD54 39 41 01 105 42 07 9,415 roadside ditch 314 -- none talus, colluvium coarse highly 

little ve

CCD55 39 41 23 105 41 57 9,274 culvert 1812 -- aspen colluvium, soil medium moderate

some ve

CCD56 39 41 28 105 41 55 9,183 culvert 269 -- none colluvium medium moderate

some ve

CCD57 39 41 39 105 41 49 9,173 culvert 1163 -- willow rock, talus coarse moderate

some ve

CCD58 39 42 03 105 41 50 8,927 culvert 2200 -- conifer soil, litter fine moderate

some ve

CCD59 39 42 06 105 42 02 8,864 roadside ditch 1085 -- conifer rock, colluvium, 

soil

coarse highly 

little ve

CCD60 39 42 10 105 41 44 8,700 roadside ditch 1572 -- conifer talus, colluvium coarse highly 

little ve

CCD61 39 42 09 105 41 55 8,677 culvert 597 -- conifer colluvium, soil medium highly 

little ve

CCD62 39 42 11 105 42 01 8,661 culvert 715 -- conifer colluvium, soil medium highly 

little ve

CCD63 39 42 13 105 41 53 8,546 roadside ditch 1100 1572+597 conifer colluvium, soil medium moderate

some ve

Total ditch = 44,492

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslope 
168 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 GD1 39 35 37 105 42 44 11,666 culvert 747 -- tundra soil fine moderate

some ve

GD2 39 35 23 105 43 06 11,561 culvert 2330 -- tundra colluvium, soil medium moderate

some ve

GD3 39 35 09 105 43 07 11,496 culvert 1416 -- tundra colluvium, soil medium highly 

little ve

GD4 39 35 07 105 43 07 11,482 culvert 138 -- conifer colluvium medium highly 

little ve

GD5 39 34 52 105 43 13 11,315 culvert 1486 -- conifer soil fine highly 

little ve

GD6 39 34 46 105 43 18 11,259 culvert 703 -- conifer colluvium, soil medium moderate

some ve

GD7 39 34 38 105 43 18 11,233 roadside ditch 1010 -- conifer talus, colluvium,

soil

coarse moderate

some ve

GD8 39 34 39 105 43 20 11,217 roadside ditch 112 -- grass talus, colluvium coarse moderate

some ve

GD9 39 34 32 105 43 30 11,171 roadside ditch 400 -- none rock, talus coarse moderate

some ve

GD10 39 34 32 105 43 33 11,138 roadside ditch 190 -- conifer colluvium medium moderate

some ve

GD11 39 34 22 105 43 28 11,062 culvert 973 -- conifer talus, colluvium coarse moderate

some ve

GD12 39 34 20 105 43 28 11,049 culvert 283 -- conifer talus, soil coarse moderate

some ve

GD13 39 34 16 105 43 28 11,013 culvert 183 -- conifer talus, colluvium coarse moderate

some ve

GD14 39 34 11 105 43 28 10,977 culvert 703 -- conifer colluvium, soil medium moderate

some ve

GD15 39 33 45 105 43 11 10,761 culvert 2863 -- conifer talus, colluvium,

soil

coarse highly 

little ve

GD16 39 33 39 105 43 09 10,656 culvert 645 -- conifer talus, colluvium,

soil

coarse highly 

little ve

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslop
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 169

GD17 39 33 32 105 43 04 10,649 culvert 1062 -- conifer rock, talus, soil coarse highly 

little ve

GD18 39 33 29 105 43 04 10,610 culvert 552 -- willow talus, soil coarse moderate

some ve

GD19 39 33 24 105 43 03 10,639 culvert 390 -- conifer talus, colluvium,

soil

coarse moderate

some ve

GD20 39 33 16 105 43 03 10,554 culvert 815 -- conifer colluvium, soil medium moderate

some ve

GD21 39 33 08 105 43 03 10,492 roadside ditch 776 -- willow talus coarse low er

reveg

GD22 39 33 13 105 43 05 10,469 culvert 534 -- aspen rock, talus, soil coarse low e

reveg

GD23 39 33 16 105 43 07 10,413 culvert 170 815 aspen talus, colluvium,

soil

coarse low e

reveg

GD24 39 33 18 105 43 08 10,423 culvert 132 -- aspen talus, colluvium,

soil

coarse low e

reveg

GD25 39 33 22 105 43 10 10,390 culvert 640 1062 grass soil fine low e

reveg

GD26 39 33 22 105 33 13 10,373 roadside ditch 568 -- grass colluvium, soil medium moderate

some ve

GD27 39 33 20 105 43 13 10,357 roadside ditch 460 -- grass colluvium, soil medium moderate

some ve

GD28 39 33 10 105 43 15 10,314 culvert 904 -- grass soil fine moderate

some ve

GD29 39 32 55 105 43 09 10,246 roadside ditch 1135 -- grass colluvium, soil medium low er

reveg

GD30 39 32 54 105 43 08 10,239 culvert 222 -- willow colluvium medium low e

reveg

GD31 39 32 52 105 43 07 10,259 culvert 217 -- willow soil fine low er

reveg

GD32 39 32 42 105 43 09 10,157 culvert 1134 -- grass soil fine moderate

some ve

GD33 39 32 27 105 43 16 10,111 culvert 1499 -- willow rock, colluvium,

soil

coarse moderate

some ve

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslope 
170 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 GD34 39 32 19 105 43 27 10,045 culvert 904 -- willow soil fine moderate

some ve

GD35 39 32 15 105 43 33 10,013 culvert 533 -- conifer rock, colluvium, soil coarse moderate

some ve

GD36 39 31 49 105 43 49 9,849 culvert 2773 -- conifer colluvium, soil medium moderate

some ve

GD37 39 31 37 105 43 52 9,799 culvert 1353 -- willow soil fine moderate

some ve

GD38 39 31 28 105 43 51 9,760 culvert 896 -- willow soil fine low e

reveg

GD39 39 31 21 105 43 48 9,747 culvert 700 -- willow soil fine low e

reveg

GD40 39 31 15 105 43 44 9,714 culvert 730 -- willow soil fine low e

reveg

GD41 39 31 13 105 43 41 9,717 culvert 515 -- willow soil fine low e

reveg

GD42 39 31 06 105 43 32 9,711 culvert 730 -- willow soil fine low e

reveg

GD43 39 31 02 105 43 28 9,698 culvert 513 -- willow soil fine low e

reveg

GD44 39 31 01 105 43 23 9,691 culvert 510 -- grass soil fine low e

reveg

GD45 39 31 00 105 43 20 9,694 culvert 144 -- grass soil fine low e

reveg

GD46 39 30 55 105 43 08 9,675 culvert 1680 -- grass soil fine low e

reveg

GD47 39 30 48 105 42 51 9,658 culvert 950 -- grass soil fine low e

reveg

GD48 39 30 47 105 42 48 9,658 culvert 250 -- grass soil fine low e

reveg

GD49 39 30 34 105 42 39 9,629 culvert 310 -- grass soil fine low e

reveg

GD50 39 30 32 105 42 41 9,632 roadside ditch 195 -- grass soil fine low e

reveg

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslop
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 171

GD51 39 30 28 105 42 36 9,570 culvert 725 -- grass talus, colluvium coarse highly 

little ve

GD52 39 30 25 105 42 32 9,511 culvert 352 -- aspen talus, colluvium coarse highly 

little ve

GD53 39 30 28 105 42 26 9,494 culvert 612 -- aspen talus, colluvium coarse highly 

little ve

GD54 39 30 29 105 42 21 9,504 roadside ditch 400 -- conifer colluvium medium highly 

little ve

GD55 39 30 22 105 42 29 9,399 roadside ditch 948 612 conifer colluvium medium highly 

little ve

GD56 39 30 22 105 42 24 9,360 culvert 361 -- conifer talus, colluvium,

soil

coarse low e

reveg

GD57 39 30 19 105 42 18 9,320 culvert 558 -- conifer soil fine low er

reveg

GD58 39 30 18 105 42 15 9,327 roadside ditch 279 -- none rock, colluvium coarse low er

evege

GD59 39 30 15 105 42 09 9,347 culvert 635 -- conifer soil fine low er

reveg

GD60 39 30 11 105 42 08 9,314 culvert 287 -- conifer soil fine low er

reveg

GD61 39 30 00 105 42 00 9,199 culvert 323 -- conifer colluvium, soil medium low er

reveg

GD62 39 29 38 105 41 45 9,189 culvert 1,085 -- conifer colluvium, soil medium moderate

some ve

GD63 39 29 31 105 41 46 9,064 culvert 1,155 -- conifer soil fine moderate

some ve

GD64 39 29 27 105 41 45 9,019 culvert 394 -- conifer soil fine low er

reveg

GD65 39 29 17 105 41 39 8,992 culvert 920 -- conifer soil fine moderate

some ve

GD66 39 29 08 105 41 39 8,996 culvert 974 -- conifer soil fine moderate

some ve

GD67 39 28 42 105 41 19 9,009 culvert 3,140 -- conifer soil fine moderate

some ve

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslope 
172 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 GD68 39 28 38 105 41 18 8,854 culvert 293 -- conifer soil fine moderate

some ve

GD69 39 28 34 105 41 07 8,959 culvert 1,170 -- willow talus, colluvium coarse moderate

some ve

GD70 39 28 24 105 41 00 8,933 culvert 965 -- willow talus, colluvium coarse moderate

some ve

GD71 39 28 21 105 40 55 8,871 culvert 472 -- willow talus, colluvium coarse moderate

some ve

GD72 39 28 06 105 40 28 8,756 culvert 2,964 -- willow colluvium, soil medium moderate

some ve

GD73 39 27 56 105 40 22 8,697 culvert 1,515 -- willow soil fine low e

reveg

GD74 39 27 49 105 40 02 8,635 culvert 74 -- willow colluvium, soil medium low e

reveg

Total ditch = 59,679

Site

number

(fig. 45)

Obstructions

Sediment travel

distance into

buffer zone

(feet)

Natural or

artificial

channel

Channel

width

(feet)

Channel

depth

(feet)

Deposition or

erosion in

buffer zone

Largest

particle size

transported

to stream

Runoff reaches

stream or lake

Factors cau

sediment to d

in buffer zo

CCD1 none 130 (to CCD3) natural 1 to 2 ft 1 to 2 ft erosion gravel always (via CCD3, 

CCD5)

not deposi

CCD2 fallen trees 360 (to CCD6) natural 2 to 3 ft 0.5 ft erosion gravel always (via CCD6) not deposiCCD3 none 150 (to CCD5) natural 2 to 4 ft 1 to 2 ft erosion gravel always (via CCD5) not deposiCCD4 fallen trees 210 natural 1.5 ft 0.5 ft erosion n/a never slope CCD5 fallen trees 875 natural 2 to 4 ft 0.5 to 2 ft both gravel always not deposiCCD6 fallen trees 650 artificial 2 to 20 ft 0.5 to 10 ft erosion gravel always not deposiCCD7 fallen trees, rocks 710 natural 2 to 3 ft 1 to 2.5 ft erosion gravel always not deposiCCD8 fallen trees 560 artificial 1 to 3 ft 1 to 3 ft erosion n/a never slope CCD9 fallen trees, rocks 210 (to CCD12) artificial 2 to 4 ft 0.5 ft both gravel always (via CCD12) not deposiCCD10 fallen trees 495 artificial 1 to 3 ft 0.5 ft both n/a never slope CCD11 fallen trees 170 (to CCD13) artificial 2 to 3 ft 0.5 to 1 ft both gravel always (via CCD13) not deposiCCD12 none 215 artificial 1 to 2 ft 0.5 to 1 ft erosion gravel always not deposi

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]

Site

number

(fig. 45)

Latitude 

(degrees 

minutes 

seconds)

Longitude

(degrees

minutes

seconds)

Altitude

(feet)

Type of

feature

Contributing

ditch length

(feet)

Ditch length

from other

upslope culverts

(feet)

Predominant

buffer-zone

vegetation

Slope material

Predominant

buffer-zone

grain size

Cutslop
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 173

CCD13 fallen trees, rocks 75 artificial 2 to 4 ft 2 to 5 ft erosion cobble always not deposiCCD14 none 195 artificial 2 ft 1 ft both gravel always not deposiCCD15 fallen trees, rocks 322 (to CCD17) artificial 1 to 2 ft 0.5 to 1 ft erosion gravel always (via CCD17) not deposiCCD16 fallen trees 120 artificial 1 to 3 ft 0.5 ft both gravel always not deposiCCD17 fallen trees 990 artificial 2 to 4 0.5 both sand always not deposiCCD18 fallen trees 345 natural and 

artificial

1 to 8 0.5–1 both gravel always not deposi

CCD19 fallen trees 70 artificial 1 to 4 0.5–1 both gravel always not deposiCCD20 beaver dams 200 natural 1 to 2 0.5 both n/a probably not obstructio

(beaver dam

CCD21 beaver dams 155 natural 1 to 2 <0.5 both n/a never slope, vegeta

beaver da

CCD22 beaver dams 170 artificial 1 to 3 0.5 both n/a never slope, vegeta

beaver da

CCD23 beaver dams 160 natural 1 to 3 0.5 both n/a never slope, vegeta

beaver da

CCD24 none 70 artificial 1 to 2 0.5 both n/a never slope, vegeta

infiltratio

CCD25 swale 25 natural 1 <0.5 deposition n/a never slope, vegetaCCD26 none 47 natural 1 to 2 0.5 both sand always not deposiCCD27 none 25 artificial 1 to 3 0.5 both gravel always not deposiCCD28 none 0 artificial n/a n/a erosion gravel always not deposiCCD29 none 134 artificial 2 to 4 1 deposition sand always not deposiCCD30 rocks 35 natural 1 to 2 0.5 erosion gravel always not deposiCCD31 rocks 70 artificial 2 1 both gravel always not deposiCCD32 rocks 40 artificial 1 to 2 0.5–1 erosion gravel always not deposiCCD33 none 10 artificial 1 to 2 0.5 both sand always not deposiCCD34 none 25 artificial 1 to 2 0.5–1 both gravel always not deposiCCD35 none 15 artificial 1 to 2 1 erosion gravel always not deposiCCD36 closed drainages 153 artificial 1 to 10 0.5 both silt/clay sometimes slope, vegeta

infiltratio

CCD37 beaver dam 253 artificial 4 to 5 1 to 2 both silt/clay sometimes beaver da

Site

number

(fig. 45)

Obstructions

Sediment travel

distance into

buffer zone

(feet)

Natural or

artificial

channel

Channel

width

(feet)

Channel

depth

(feet)

Deposition or

erosion in

buffer zone

Largest

particle size

transported

to stream

Runoff reaches

stream or lake

Factors cau

sediment to d

in buffer zo

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine = sand/silt, medium = gravel and coarse = larger than gravel]
174 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 CCD38 beaver dam 253 artificial 1 to 5 1 to 2 both silt/clay sometimes beaver da

CCD39 none 200 (est) artificial unknown unknown unknown unknown probably not deposiCCD40 none 150 (est) artificial unknown unknown deposition sand always not deposiCCD41 rocks 250 (est) natural 1 to 3 0.5 both sand always not deposiCCD42 none 800 natural 1 to 4 0.5 both sand always not deposiCCD43 none 125 natural 1 to 3 1 erosion gravel always not deposiCCD44 none 5 natural 1 <0.5 erosion sand always not deposiCCD45 none 5 natural 1 0.5 erosion sand always not deposiCCD46 rocks, closed drainages 120 artificial 1 to 3 0.5 both n/a never obstructio

infiltratio

CCD47 rocks 300 artificial 1 to 4 0.5 both gravel always infiltratioCCD48 rocks 25 artificial 1 to 2 0.5–1 erosion gravel always not deposiCCD49 closed drainages 10 artificial 1 to 2 1 both n/a never obstructio

infiltratio

CCD50 none 75 artificial 1 to 3 0.5 deposition n/a never slope CCD51 none 50 artificial 2 to 10 2 to 5 erosion gravel sometimes obstructioCCD52 closed drainage 120 artificial 1 0–Jan both n/a never closed drainCCD53 none 25 artificial 1 to 2 0.5 both n/a never slope, infiltrCCD54 rocks 40 artificial 2 to 3 1 to 2 erosion gravel always not deposiCCD55 closed drainages 350 artificial 1 to 3 0.5 deposition silt/clay sometimes slope, infiltrCCD56 none 0 artificial n/a n/a erosion sand always not deposiCCD57 rocks 15 artificial 1 to 2 0.5 both gravel always not deposiCCD58 none 200 artificial 1 to 2 0.5 deposition n/a never infiltratioCCD59 none 200 (est) artificial 1 to 3 0.5–1 both n/a never slope, infiltrCCD60 rocks 250 (est) artificial 1 to 2 1 both gravel always not deposiCCD61 none 150 to CCD62 artificial 1 to 2 0.5 both sand sometimes via 

CCD62

not deposi

CCD62 sediment settling

basin

(flows under road 

into ditch for CCD62)

artificial n/a n/a deposition silt/clay sometimes via 

CCD62

lack of flo

sediment b

Site

number

(fig. 45)

Obstructions

Sediment travel

distance into

buffer zone

(feet)

Natural or

artificial

channel

Channel

width

(feet)

Channel

depth

(feet)

Deposition or

erosion in

buffer zone

Largest

particle size

transported

to stream

Runoff reaches

stream or lake

Factors cau

sediment to d

in buffer zo

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine= sand/silt, medium= gravel and coarse= larger than gravel]
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 175

CCD63 urban obstacles n/a artificial n/a n/a both sand sometimes n/a GD1 none 30 artificial 1 <0.5 deposition n/a never slope, vegetaGD2 none 510 artificial 1 to 10 0.5–1.5 both n/a never vegetation, infiGD3 rocks 405 artificial 1 to 8 0.5–3 erosion gravel always not deposiGD4 fallen trees, rocks 155 artificial 1 to 3 0.5 deposition n/a never slope, infiltra

vegetatio

GD5 closed drainages 240 artificial 1 to 3 0.5–1.0 both n/a never obstructions, 

infiltratio

GD6 fallen trees, rocks 390 artificial 1 to 4 <0.5 both gravel always not deposiGD7 closed drainages 340 artificial 1 to 5 <0.5–1 erosion n/a never closed drainGD8 rocks, closed 

drainages

30 artificial 1 0.5 deposition n/a never closed drain

GD9 rocks, closed 

drainages

20 artificial 1 0.5 deposition n/a never closed drain

GD10 none <5 artificial 2 to 3 0.5 erosion gravel always not deposiGD11 fallen trees, rocks 770 both 1 to 3 0.5–1 both sand always not deposiGD12 fallen trees, rocks 510 artificial 1 to 2 0.5 both sand always not deposiGD13 fallen trees, rocks 50 artificial 1 0.5 deposition n/a never infiltratioGD14 fallen trees, rocks 1246 artificial 1 to 4 0.5–1 both n/a never slope GD15 fallen trees rocks 775 natural 1 to 8 0.5–1.5 both sand always not deposiGD16 fallen trees, rocks 760 artificial 1 to 8 0.5–1.5 both sand always not deposiGD17 fallen trees, rocks 1295 natural 1 to 4 0.5–3 both sand never slope, vegeta

infiltratio

GD18 fallen trees, rocks 295 natural 0.5 to 1 0.5–1.5 both n/a never infiltratioGD19 fallen trees, rocks 160 artificial 0.5–2 0.5–1 both n/a never vegetation, infiGD20 fallen trees, rocks 175 (to GD23 ditch) artificial 1 to 4 0.5–1 both n/a never (via GD25) not deposiGD21 fallen trees, rocks 320 artificial 2 to 4 0.5–1 both n/a never slope, infiltrGD22 fallen trees, rocks 335 artificial 1 to 2 0.5 both n/a never slope GD23 fallen trees, rocks 250 artificial 1 to 5 0.5 both n/a never slope GD24 fallen trees, rocks 60 artificial 1 0.5 both n/a never slope GD25 rocks 545 natural 2 to 4 1 to 3 erosion n/a never slope, vegeta

infiltratio

GD26 none 0 artificial 1 to 2 0.5 erosion sand always not deposi

Site

number

(fig. 45)

Obstructions

Sediment travel

distance into

buffer zone

(feet)

Natural or

artificial

channel

Channel

width

(feet)

Channel

depth

(feet)

Deposition or

erosion in

buffer zone

Largest

particle size

transported

to stream

Runoff reaches

stream or lake

Factors cau

sediment to d

in buffer zo

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine= sand/silt, medium= gravel and coarse= larger than gravel]
176 Assessment of Water Quality, Road Runoff, and Bulk Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97 GD27 none 0 artificial 1 to 2 0.5 erosion sand sometimes vegetation, infi

GD28 closed drainages 20 artificial 1 0.5 deposition n/a never closed drain

vegetation, infi

GD29 rocks 0 artificial 1.5 0.5 both silt/clay always not deposiGD30 none 45 natural 4 to 6 0.5 erosion silt/clay always not deposiGD31 closed drainages 200 natural 1 to 2 0.5 to 1 deposition n/a never slope, vegeta

infiltratio

GD32 none 50 artificial 1 <0.5 deposition n/a never slope, vegeta

infiltratio

GD33 fallen trees, rocks 80 artificial 1 to 2 <0.5 both n/a never slope, vegeta

infiltratio

GD34 fallen trees, rocks 105 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD35 fallen trees, rocks 505 natural 1 to 3 0.5–1 both n/a never obstructions, veGD36 fallen trees, rocks 120 natural 1 to 2 0.5–1 both sand sometimes infiltratioGD37 none 165 artificial 1 to 3 0.5 both n/a never slope, vegeta

infiltratio

GD38 none 25 artificial 1 0.5 deposition n/a never slope, vegeta

infiltratio

GD39 culvert blocked 0 n/a n/a n/a n/a n/a never obstructioGD40 none 15 artificial 1 0.5 erosion sand always not deposiGD41 none 5 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD42 none 10 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD43 none <5 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD44 none <5 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD45 none 10 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD46 none 10 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD47 none 45 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

Site

number

(fig. 45)

Obstructions

Sediment travel

distance into

buffer zone

(feet)

Natural or

artificial

channel

Channel

width

(feet)

Channel

depth

(feet)

Deposition or

erosion in

buffer zone

Largest

particle size

transported

to stream

Runoff reaches

stream or lake

Factors cau

sediment to d

in buffer zo

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine= sand/silt, medium= gravel and coarse= larger than gravel]
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 177

GD48 none 10 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD49 none 10 artificial 1 0.5 both n/a never slope, vegeta

infiltratio

GD50 rocks, closed

drainages

95 artificial 1 to 2 0.5–1 both n/a never obstructio

infiltratio

GD51 culvert blocked n/a artificial n/a n/a n/a n/a probably never obstructioGD52 rocks 300 artificial 1 to 5 0.5–1 both gravel always not deposiGD53 fallen trees, rocks 200 natural 1 to 2 0.5 both gravel always(via GD55) not deposiGD54 rocks 40 artificial 1 0.5 erosion gravel always not deposiGD55 rocks 70 artificial 1 to 2 0.5 both gravel always not deposiGD56 rocks 30 artificial 1 to 2 0.5 both n/a never obstructio

infiltratio

GD57 none 55 artificial 1 to 2 0.5 both n/a never slope, vegetaGD58 rocks 20 artificial 1 0.5 erosion sand sometimes not deposiGD59 none 10 artificial 0.5 <0.5 both sand always not deposiGD60 rocks 35 artificial 1 to 2 0.5 both sand always not deposiGD61 rocks 45 artificial 1 to 4 0.5 both n/a never slope GD62 rocks 40 artificial 1 0.5 both gravel always not deposiGD63 none 5 artificial 1 to 2 0.5 both sand always not deposiGD64 fallen trees 40 artificial 1 to 2 0.5–1 both n/a never slope, obstruc

infiltratio

GD65 none 90 artificial 1 to 4 <0.5 both n/a never slope, obstruc

infiltratio

GD66 rocks 50 artificial 1 to 2 0.5 both sand always not deposiGD67 rocks 3 artificial 1 <0.5 both sand always not deposiGD68 rocks 15 artificial 1 0.5 both sand always not deposiGD69 rocks 4 artificial 1 <0.5 erosion sand always not deposiGD70 rocks 8 artificial 1 0.5 erosion gravel always not deposiGD71 rocks 4 artificial 1 0.5 erosion sand always not deposiGD72 none 10 artificial 1 to 2 0.5 both sand always not deposiGD73 blocked culvert n/a artificial n/a n/a n/a n/a n/a n/a GD74 rocks 40 natural 1 0.5 both sand sometimes not deposi

Site

number

(fig. 45)

Obstructions

Sediment travel

distance into

buffer zone

(feet)

Natural or

artificial

channel

Channel

width

(feet)

Channel

depth

(feet)

Deposition or

erosion in

buffer zone

Largest

particle size

transported

to stream

Runoff reaches

stream or lake

Factors cau

sediment to d

in buffer zo

Table 54. Drainage-feature evaluation data—Continued[--, no data; CCD, South Clear Creek drainage; GD, Geneva Creek drainage; n/a, not applicable; culvert refers to the end of a cross drain on the fillslope side; roadside dditch channels road runoff away from the road, such as at a switchback; note: table is in two parts and midway through this table a new set of column headings begins; prerefers to soil or sediment cover on the slope where fine= sand/silt, medium= gravel and coarse= larger than gravel]
178 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Table 55. Suspended-sediment discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of suspended-sediment discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1996

[Estimate of road runoff suspended-sediment discharge was based on CRD7 sediment discharge extrapolated by road length (CRD7 sediment discharge 

times 10.6, which is the ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road 

suspended-sediment discharge is expressed as percentage of suspended-sediment discharge measured at CC2, and the potential change in concentration 

under flow conditions at CC2 if the estimated road sediment discharge is added to that of CC2]

Date

Percentage of

suspendedsediment

discharge

at CC2

Potential change

in concentration

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of

suspended

sediment

discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of

suspendedsediment

discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

sediment discharge

04/25/96 290 3 06/13/96 0.0 0 08/01/96 0.0 0

04/26/96 2,890 34 06/14/96 .0 0 08/02/96 .0 0

04/27/96 3,610 43 06/15/96 32 2 08/03/96 .0 0

04/28/96 2,080 25 06/16/96 .0 0 08/04/96 .0 0

04/29/96 1,920 23 06/17/96 .0 0 08/05/96 .0 0

04/30/96 630 11 06/18/96 .0 0 08/06/96 .0 0

05/01/96 26 4 06/19/96 .0 0 08/07/96 .0 0

05/02/96 26 4 06/20/96 .0 0 08/08/96 .0 0

05/03/96 29 5 06/21/96 56 3 08/09/96 .0 0

05/04/96 55 10 06/22/96 64 3 08/10/96 .0 0

05/05/96 36 8 06/23/96 .0 0 08/11/96 .0 0

05/06/96 37 9 06/24/96 .0 0 08/12/96 .0 0

05/07/96 22 6 06/25/96 .0 0 08/13/96 .0 0

05/08/96 14 4 06/26/96 .0 0 08/14/96 .0 0

05/09/96 12 3 06/27/96 .0 0 08/15/96 .0 0

05/10/96 5.2 1 06/28/96 .0 0 08/16/96 .0 0

05/11/96 8.2 3 06/29/96 .0 0 08/17/96 .0 0

05/12/96 34 11 06/30/96 .0 0 08/18/96 .0 0

05/13/96 18 6 07/01/96 .0 0 08/19/96 .0 0

05/14/96 4.0 2 07/02/96 .0 0 08/20/96 .0 0

05/15/96 2.7 1 07/03/96 .0 0 08/21/96 100 59

05/16/96 2.5 1 07/04/96 .0 0 08/22/96 .0 0

05/17/96 1.2 1 07/05/96 .0 0 08/23/96 650 450

05/18/96 1.5 1 07/06/96 .0 0 08/24/96 .0 0

05/19/96 .7 0 07/07/96 .0 0 08/25/96 .0 0

05/20/96 2.3 0 07/08/96 .0 0 08/26/96 .0 0

05/21/96 13 1 07/09/96 .0 0 08/27/96 78 31

05/22/96 11 1 07/10/96 .0 0 08/28/96 .0 0

05/23/96 1.3 0 07/11/96 .0 0 08/29/96 .0 0

05/24/96 7.3 1 07/12/96 .0 0 08/30/96 .0 0

05/25/96 .0 0 07/13/96 .0 0 08/31/96 .0 0

05/26/96 .0 0 07/14/96 .0 0 09/01/96 .0 0

05/27/96 .0 0 07/15/96 .0 0 09/02/96 .0 0

05/28/96 .0 0 07/16/96 .0 0 09/03/96 .0 0

05/29/96 2.5 0 07/17/96 .0 0 09/04/96 .0 0

05/30/96 56 4 07/18/96 .0 0 09/05/96 .0 0

05/31/96 3.0 0 07/19/96 .0 0 09/06/96 480 440

06/01/96 .0 0 07/20/96 .0 0 09/07/96 .0 0

06/02/96 .0 0 07/21/96 .0 0 09/08/96 .0 0

06/03/96 .0 0 07/22/96 .0 0 09/09/96 .0 0

06/04/96 .0 0 07/23/96 .0 0 09/10/96 .0 0

06/05/96 .0 0 07/24/96 .0 0 09/11/96 .0 0

06/06/96 .0 0 07/25/96 .0 0 09/12/96 480 190
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 179

06/07/96 0.0 0 07/26/96 0.0 0 09/13/96 0.0 0

06/08/96 .0 0 07/27/96 .0 0 09/14/96 300 39

06/09/96 .0 0 07/28/96 .0 0 09/15/96 1,060 56

06/10/96 .0 0 07/29/96 .0 0 09/16/96 .0 0

06/11/96 .0 0 07/30/96 .0 0 09/17/96 .0 0

06/12/96 .0 0 07/31/96 .0 0

Table 56. Suspended-sediment discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of suspended-sediment discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1997

[Estimate of road runoff suspended-sediment discharge was based on CRD7 sediment discharge extrapolated by road length (CRD7 sediment discharge 

times 10.6, which is the ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road 

suspended-sediment discharge is expressed as percentage of suspended-sediment discharge measured at CC2, and the potential change in concentration 

under flow conditions at CC2 if the estimated road sediment discharge is added to that of CC2]

Date

Percentage of

suspendedsediment

discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of 

suspendedsediment

discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of 

suspendedsediment 

discharge 

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge

05/08/97 70 6 06/26/97 0.0 0 08/14/97 0.0 0

05/09/97 25 3 06/27/97 .0 0 08/15/97 .0 0

05/10/97 78 12 06/28/97 .0 0 08/16/97 .0 0

05/11/97 69 13 06/29/97 .0 0 08/17/97 .0 0

05/12/97 2.9 1 06/30/97 .0 0 08/18/97 .0 0

05/13/97 86 50 07/01/97 .0 0 08/19/97 .0 0

05/14/97 40 16 07/02/97 .0 0 08/20/97 .0 0

05/15/97 13 9 07/03/97 .0 0 08/21/97 .0 0

05/16/97 16 11 07/04/97 .0 0 08/22/97 .0 0

05/17/97 2.6 5 07/05/97 .0 0 08/23/97 .0 0

05/18/97 3.3 4 07/06/97 .0 0 08/24/97 .0 0

05/19/97 2.7 3 07/07/97 .0 0 08/25/97 .0 0

05/20/97 4.5 2 07/08/97 .0 0 08/26/97 .0 0

05/21/97 9.9 2 07/09/97 .0 0 08/27/97 .0 0

05/22/97 20 3 07/10/97 .0 0 08/28/97 .0 0

05/23/97 5.7 3 07/11/97 .0 0 08/29/97 .0 0

05/24/97 7.2 2 07/12/97 .0 0 08/30/97 .0 0

05/25/97 5.8 2 07/13/97 .0 0 08/31/97 .0 0

05/26/97 .0 0 07/14/97 .0 0 09/01/97 .0 0

05/27/97 .0 0 07/15/97 .0 0 09/02/97 .0 0

05/28/97 .3 0 07/16/97 .0 0 09/03/97 1,410 2,330

05/29/97 30 5 07/17/97 .0 0 09/04/97 .0 0

05/30/97 3.6 2 07/18/97 .0 0 09/05/97 .0 0

05/31/97 1.1 2 07/19/97 .0 0 09/06/97 .0 0

06/01/97 .1 0 07/20/97 .0 0 09/07/97 .0 0

Table 55. Suspended-sediment discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of suspended-sediment discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1996—Continued

[Estimate of road runoff suspended-sediment discharge was based on CRD7 sediment discharge extrapolated by road length (CRD7 sediment discharge 

times 10.6, which is the ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road 

suspended-sediment discharge is expressed as percentage of suspended-sediment discharge measured at CC2, and the potential change in concentration 

under flow conditions at CC2 if the estimated road sediment discharge is added to that of CC2]

Date

Percentage of

suspendedsediment

discharge

at CC2

Potential change

in concentration

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of

suspended

sediment

discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of

suspendedsediment

discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

sediment discharge
180 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

06/02/97 .2 0 07/21/97 0.0 0 09/08/97 0.0 0

06/03/97 .0 0 07/22/97 .0 0 09/09/97 .0 0

06/04/97 .0 0 07/23/97 .0 0 09/10/97 .0 0

06/05/97 .0 0 07/24/97 .0 0 09/11/97 .0 0

06/06/97 7.4 5 07/25/97 .0 0 09/12/97 .0 0

06/07/97 3.9 6 07/26/97 1,220 740 09/13/97 .0 0

06/08/97 4.7 5 07/27/97 460 420 09/14/97 .0 0

06/09/97 .2 0 07/28/97 50 220 09/15/97 .0 0

06/10/97 .0 0 07/29/97 .0 0 09/16/97 .0 0

06/11/97 2.2 0 07/30/97 .0 0 09/17/97 .0 0

06/12/97 .0 0 07/31/97 44. 28 09/18/97 .0 0

06/13/97 300 64 08/01/97 58. 34 09/19/97 2,120 98

06/14/97 6.4 1 08/02/97 .0 0 09/20/97 689 36

06/15/97 .0 0 08/03/97 6.8 6 09/21/97 11,400 303

06/16/97 .0 0 08/04/97 .0 0 09/22/97 130 9

06/17/97 .0 0 08/05/97 8.0 4 09/23/97 .0 0

06/18/97 .0 0 08/06/97 18. 13 09/24/97 .0 0

06/19/97 .0 0 08/07/97 50 21 09/25/97 .0 0

06/20/97 .0 0 08/08/97 .0 0 09/26/97 .0 0

06/21/97 .0 0 08/09/97 200 224 09/27/97 .0 0

06/22/97 .0 0 08/10/97 18 44 09/28/97 .0 0

06/23/97 .0 0 08/11/97 180 84 09/29/97 .0 0

06/24/97 .0 0 08/12/97 .0 0 09/30/97 .0 0

06/25/97 .0 0 08/13/97 .0 0

Table 57. Dissolved-solids discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of dissolved-solids discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1996

[Estimate of road runoff dissolved-solids (DS) discharge was based on CRD7 DS discharge extrapolated by road length (CRD7 DS times 10.6, which is the 

ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road DS is expressed as percentage of 

DS measured at CC2, and the potential change in concentration under flow conditions at CC2 if the estimated road DS is added to that of CC2]

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road 

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

04/25/96 1.4 1 06/13/96 0.0 0 08/01/96 0.0 0

04/26/96 10.7 8 06/14/96 .0 0 08/02/96 .0 0

04/27/96 16.1 12 06/15/96 1.1 .4 08/03/96 .0 0

04/28/96 15.1 11 06/16/96 .0 0 08/04/96 .0 0

04/29/96 12.7 9 06/17/96 .0 0 08/05/96 .0 0

04/30/96 5.7 4 06/18/96 .0 0 08/06/96 .0 0

05/01/96 1.9 1 06/19/96 .0 0 08/07/96 .0 0

Table 56. Suspended-sediment discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of suspended-sediment discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1997—Continued

[Estimate of road runoff suspended-sediment discharge was based on CRD7 sediment discharge extrapolated by road length (CRD7 sediment discharge 

times 10.6, which is the ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road 

suspended-sediment discharge is expressed as percentage of suspended-sediment discharge measured at CC2, and the potential change in concentration 

under flow conditions at CC2 if the estimated road sediment discharge is added to that of CC2]

Date

Percentage of

suspendedsediment

discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of 

suspendedsediment

discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge

Date

Percentage of 

suspendedsediment 

discharge 

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road

sediment discharge
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 181

05/02/96 1.5 .9 06/20/96 .0 0 08/08/96 .0 0

05/03/96 1.8 1 06/21/96 .3 .1 08/09/96 .0 0

05/04/96 3.1 2 06/22/96 .4 .2 08/10/96 .0 0

05/05/96 2.8 1 06/23/96 .0 0 08/11/96 .0 0

05/06/96 1.9 .9 06/24/96 .0 0 08/12/96 .0 0

05/07/96 1.3 .6 06/25/96 .0 0 08/13/96 .0 0

05/08/96 .8 .4 06/26/96 .0 0 08/14/96 .0 0

05/09/96 .9 .4 06/27/96 .0 0 08/15/96 .0 0

05/10/96 .7 .3 06/28/96 .0 0 08/16/96 .0 0

05/11/96 .8 .3 06/29/96 .0 0 08/17/96 .0 0

05/12/96 1.5 1.6 06/30/96 .0 0 08/18/96 .0 0

05/13/96 1.4 .6 07/01/96 .0 0 08/19/96 .0 0

05/14/96 .8 .3 07/02/96 .0 0 08/20/96 .0 0

05/15/96 .7 .2 07/03/96 .0 0 08/21/96 1.1 .8

05/16/96 .6 .2 07/04/96 .0 0 08/22/96 .0 0

05/17/96 .3 .1 07/05/96 .0 0 08/23/96 .5 .3

05/18/96 .4 .1 07/06/96 .0 0 08/24/96 .0 0

05/19/96 .3 .1 07/07/96 .0 0 08/25/96 .0 0

05/20/96 .1 .03 07/08/96 .0 0 08/26/96 .0 0

05/21/96 .2 .1 07/09/96 .0 0 08/27/96 .6 .4

05/22/96 .1 .04 07/10/96 .0 0 08/28/96 .0 0

05/23/96 .03 .01 07/11/96 .0 0 08/29/96 .0 0

05/24/96 .1 .02 07/12/96 .0 0 08/30/96 .0 0

05/25/96 .0 0 07/13/96 .0 0 08/31/96 .0 0

05/26/96 .0 0 07/14/96 .0 0 09/01/96 .0 0

05/27/96 .0 0 07/15/96 .0 0 09/02/96 .0 0

05/28/96 .0 0 07/16/96 .0 0 09/03/96 .0 0

05/29/96 .04 .01 07/17/96 .0 0 09/04/96 .0 0

05/30/96 .2 .05 07/18/96 .0 0 09/05/96 .0 0

05/31/96 .0 0 07/19/96 .0 0 09/06/96 4.2 3

06/01/96 .0 0 07/20/96 .0 0 09/07/96 .0 0

06/02/96 .0 0 07/21/96 .0 0 09/08/96 .0 0

06/03/96 .0 0 07/22/96 .0 0 09/09/96 .0 0

06/04/96 .0 0 07/23/96 .0 0 09/10/96 .0 0

06/05/96 .0 0 07/24/96 .0 0 09/11/96 .0 0

06/06/96 .0 0 07/25/96 .0 0 09/12/96 4.8 4

06/07/96 .0 0 07/26/96 .0 0 09/13/96 .0 0

06/08/96 .0 0 07/27/96 .0 0 09/14/96 1.0 .7

06/09/96 .0 0 07/28/96 .0 0 09/15/96 .0 0

06/10/96 .0 0 07/29/96 .0 0 09/16/96 .0 0

06/11/96 .0 0 07/30/96 .0 0 09/17/96 .0 0

06/12/96 .0 0 07/31/96 .0 0

Table 57. Dissolved-solids discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of dissolved-solids discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1996—Continued

[Estimate of road runoff dissolved-solids (DS) discharge was based on CRD7 DS discharge extrapolated by road length (CRD7 DS times 10.6, which is the 

ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road DS is expressed as percentage of 

DS measured at CC2, and the potential change in concentration under flow conditions at CC2 if the estimated road DS is added to that of CC2]

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration 

at CC2 due to 

estimated road 

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge
182 Assessment of Water Quality, Road Runoff, and Bulk Atmospheric Deposition, Guanella Pass Area, 

Clear Creek and Park Counties, Colorado, Water Years 1995–97

Table 58. Dissolved-solids discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of dissolved-solids discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1997

[Estimate of road runoff dissolved-solids (DS) discharge was based on CRD7 DS discharge extrapolated by road length (CRD7 DS times 10.6, which is the 

ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road DS is expressed as percentage of 

DS measured at CC2, and the potential change in concentration under flow conditions at CC2 if the estimated road DS is added to that of CC2]

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

05/08/97 0.5 0.2 06/26/97 0.0 0 08/14/97 0.0 0

05/09/97 .4 .1 06/27/97 .0 0 08/15/97 .0 0

05/10/97 .8 .3 06/28/97 .0 0 08/16/97 .0 0

05/11/97 1.5 .5 06/29/97 .0 0 08/17/97 .0 0

05/12/97 .3 .1 06/30/97 .0 0 08/18/97 .0 0

05/13/97 2.4 .8 07/01/97 .0 0 08/19/97 .0 0

05/14/97 1.4 .5 07/02/97 .0 0 08/20/97 .0 0

05/15/97 1.2 .4 07/03/97 .0 0 08/21/97 .0 0

05/16/97 .4 .1 07/04/97 .0 0 08/22/97 .0 0

05/17/97 .6 .2 07/05/97 .0 0 08/23/97 .0 0

05/18/97 .7 .2 07/06/97 .0 0 08/24/97 .0 0

05/19/97 .4 .1 07/07/97 .0 0 08/25/97 .0 0

05/20/97 .4 .1 07/08/97 .0 0 08/26/97 .0 0

05/21/97 .4 .1 07/09/97 .0 0 08/27/97 .0 0

05/22/97 .3 .1 07/10/97 .0 0 08/28/97 .0 0

05/23/97 .3 .1 07/11/97 .0 0 08/29/97 .0 0

05/24/97 .3 .1 07/12/97 .0 0 08/30/97 .0 0

05/25/97 .2 .1 07/13/97 .0 0 08/31/97 .0 0

05/26/97 .0 0 07/14/97 .0 0 09/01/97 .0 0

05/27/97 .0 0 07/15/97 .0 0 09/02/97 .0 0

05/28/97 .01 .004 07/16/97 .0 0 09/03/97 19.6 10

05/29/97 .3 .1 07/17/97 .0 0 09/04/97 .0 0

05/30/97 .1 .02 07/18/97 .0 0 09/05/97 .0 0

05/31/97 .05 .02 07/19/97 .0 0 09/06/97 .0 0

06/01/97 .02 .007 07/20/97 .0 0 09/07/97 .0 0

06/02/97 .01 .003 07/21/97 .0 0 09/08/97 .0 0

06/03/97 .0 0 07/22/97 .0 0 09/09/97 .0 0

06/04/97 .0 0 07/23/97 .0 0 09/10/97 .0 0

06/05/97 .0 0 07/24/97 .0 0 09/11/97 .0 0

06/06/97 .7 .2 07/25/97 .0 0 09/12/97 .0 0

06/07/97 .5 .2 07/26/97 5.5 3 09/13/97 .0 0

06/08/97 .4 .13 07/27/97 24.3 13 09/14/97 .0 0

06/09/97 .01 .004 07/28/97 7.2 4 09/15/97 .0 0

06/10/97 .0 0 07/29/97 .0 0 09/16/97 .0 0

06/11/97 .1 .025 07/30/97 .0 0 09/17/97 .0 0

06/12/97 .0 0 07/31/97 1.8 .9 09/18/97 .0 0

06/13/97 .3 .1 08/01/97 1.5 .7 09/19/97 1.7 1

06/14/97 .2 .06 08/02/97 .0 0 09/20/97 9.2 5

06/15/97 .0 0 08/03/97 2.6 1 09/21/97 10.4 5
APPENDIX—HYDROLOGIC AND WATER-QUALITY DATA 183

06/16/97 .0 0 08/04/97 .0 0 09/22/97 .4 .2

06/17/97 .0 0 08/05/97 .6 .3 09/23/97 .0 0

06/18/97 .0 0 08/06/97 1.9 .8 09/24/97 .0 0

06/19/97 .0 0 08/07/97 2.6 1 09/25/97 .0 0

06/20/97 .0 0 08/08/97 .0 0 09/26/97 .0 0

06/21/97 .0 0 08/09/97 4.5 2 09/27/97 .0 0

06/22/97 .0 0 08/10/97 3.1 1 09/28/97 .0 0

06/23/97 .0 0 08/11/97 4.4 2 09/29/97 .0 0

06/24/97 .0 0 08/12/97 .0 0 09/30/97 .0 0

06/25/97 .0 0 08/13/97 .0 0

Table 58. Dissolved-solids discharge from Guanella Pass road segment upstream from Naylor Creek expressed as a 

percentage of dissolved-solids discharge at CC2 and as a potential change in concentration at CC2, during CRD7 flow 

period, water year 1997—Continued

[Estimate of road runoff dissolved-solids (DS) discharge was based on CRD7 DS discharge extrapolated by road length (CRD7 DS times 10.6, which is the 

ratio of the road length draining to CC2 and the road length draining to CRD7); concentration in milligrams per liter; road DS is expressed as percentage of 

DS measured at CC2, and the potential change in concentration under flow conditions at CC2 if the estimated road DS is added to that of CC2]

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge

Date

Percentage of

DS discharge

at CC2

Potential change

in concentration

at CC2 due to

estimated road

DS discharge