Water Quality Assessment for the
Tongue River Watershed,
Montana
August 2, 2007
FINAL DRAFT
Prepared by:
U.S. Environmental Protection Agency
Montana Operations Office and Tetra Tech, Inc.
Project Manager: Ron Steg
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Water Quality Assessment for
the Tongue River Watershed,
Montana
FINAL DRAFT
August 2, 2007
Prepared by:
U.S. Environmental Protection Agency
Montana Operations Office
and Tetra Tech, Inc.
Project Manager: Ron Steg
Cover photo by USGS
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Acronyms
Acronyms
ARM
Administrative Rules of Montana
BEHI
Bank erosion hazard index
BLM
Bureau of Land Management
CBM
Coal bed methane
CFS
Cubic feet per second
CWA
Clean Water Act
DNRC
Montana Department of Natural Resources and Conservation
DO
Dissolved oxygen
EC
Electrical conductivity
EIS
Environmental Impact Statement
GIS
Geographic information system
HII
Human Influence Index
MDEQ
Montana Department of Environmental Quality
MFWP
Montana Fish, Wildlife, and Parks
mg/L
Milligrams per liter
MLRA
Major land resource area
MRLC
Multi-Resolution Land Characterization
NASS
National Agricultural Statistics Service
NCEPD
Northern Cheyenne Environmental Protection Department
NOAA
National Oceanic and Atmospheric Administration
NRCS
Natural Resources Conservation Service
NTU
Nephelometric turbidity units
NWIS
National Water Information System
RBC
Riparian and bank condition
RBS
Relative bed stability
REMAP
Regional Environmental Monitoring and Assessment Program
SAR
Sodium adsorption ratio
SC
Specific conductance
TDS
Total dissolved solids
TMDL
Total maximum daily load
TN
Total nitrogen
TP
Total phosphorus
TR
Total Recoverable
TRR
Tongue River Reservoir
TRWU
Tongue River Water Users
TSI
Trophic state index
TSS
Total suspended solids
T&Y
Tongue and Yellowstone Irrigation District
ljg/L
Micrograms per liter
|jS/cm
Microsiemens per centimeter
USDI
United States Department of Interior
USEPA
United States Environmental Protection Agency
USFS
United States Forest Service
USGS
United States Geological Survey
USLE
Universal Soil Loss Equation
WDEQ
Wyoming Department of Environmental Quality
WQ
Water quality
WRCC
Western Regional Climate Center
WWDC
Wyoming Water Development Commission
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Table of Contents
Table of Contents
Executive Summary xm
1.0 Introduction 1
1.1 Montana 303(d) List Status 3
1.2 Wyoming 303(d) List Status 6
2.0 Applicable Water Quality Standards 7
3.0 Tongue River 9
3.1 Salinity 10
3.1.1 Spatial Characterization 12
3.1.2 Relationship between Specific Conductance and Discharge 14
3.1.3 Comparison to Applicable Standards 16
3.1.3.1 Instantaneous Maximum Standard. 16
3.1.3.2 Monthly Average Standards 17
3.1.3.3 Nondegradation 20
3.1.4 Sources of Salinity and Their Influence on the Tongue River 23
3.2 Sodium Adsorption Ratio 25
3.2.1 Spatial Characterization 27
3.2.2 Relationship between SAR and Discharge 29
3.2.3 Comparison to Applicable Standards 31
3.2.3.1 Instantaneous Maximum SAR Standards 31
3.2.3.2 Monthly Average SAR Standards 31
3.2.3.3 Nondegradation 33
3.2.4 Sources of SAR and Their Influence on Tongue River 36
3.3 Metals 36
3.3.1 State Line to the Tongue River Reservoir 37
3.3.2 Tongue River Reservoir Dam to the T&Y Diversion Dam 38
3.3.3 T&Y Diversion Dam to the Mouth 40
3.3.3.1 Iron 40
3.3.3.2 Copper 41
3.3.3.3 Lead. 42
3.3.3.4 Cadmium 43
3.3.3.5 Zinc 43
3.3.3.6 Nickel 44
3.3.4 Metals and Sediment 44
3.3.5 Sources of Metals 47
3.4 Total Suspended Solids 48
3.4.1 Spatial Characterization 50
3.4.2 Comparison to Other Great Plains Streams 52
3.4.3 Sediment Source Identification and Load Quantification 52
3.4.3.1 Tongue River Reservoir (Suspended Solids Sink) 52
3.4.3.2 Upland Sediment Loading (Suspended Solids Source) 53
3.4.3.3 Bank Erosion (Suspended Solids Source) 53
3.4.3.4 Suspended Solids Mass Balance 54
3.5 Other Inorganics (Sulfates) 56
4.0 Hanging Woman Creek 57
4.1 Salinity 58
4.1.1 Spatial Characterization 60
4.1.2 Relationship between Specific Conductance and Discharge 61
4.1.3 Comparison to Applicable Standards 62
4.1.3.1 Instantaneous Maximum Salinity Standard 62
iii
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Table of Contents
4.1.3.2 Monthly Average Salinity Standard 63
4.1.3.3 Nondegradation 64
4.1.4 Sources of Salinity and Their Influence on Hanging Woman Creek 64
4.2 SAR 65
4.2.1 Spatial Characterization 65
4.2.2 Relationship between SAR and Discharge 66
4.2.3 Comparison to Applicable Standards 67
4.2.3.1 Instantaneous Maximum SAR Standard 67
4.2.3.2 Monthly Average SAR Standard 68
4.2.3.3 Nondegradation 69
4.2.4 Sources of SAR and Their Influence on Hanging Woman Creek 70
4.3 Metals 70
4.4 Siltation/Suspended Solids 71
4.4.1 1990 Nonpoint Source Stream Reach Assessment and Physical Characterization 72
4.4.2 Relative Bed Stability Index 73
4.4.3 HII 73
4.4.4 Riparian and Bank Condition 73
4.4.5 Rapid Habitat Assessment 73
4.4.6 NRCS Riparian Assessment 74
4.4.7 In-Stream Sediment Concentrations 77
4.4.8 Sediment Source Identification and Load Quantification 79
5.0 Otter Creek 81
5.1 Salinity 82
5.1.1 Spatial Characterization 84
5.1.2 Relationship between Specific Conductance and Discharge 86
5.1.3 Comparison to Applicable Standards 86
5.1.3.1 Instantaneous Maximum Salinity Standard 87
5.1.3.2 Monthly Average Salinity Standard 88
5.1.3.3 Nondegradation 89
5.1.4 Sources of Salinity and Their Influence on Otter Creek 89
5.2 SAR 90
5.2.1 Spatial Characterization 90
5.2.2 Relationship between SAR and Discharge 93
5.2.3 Comparison to Applicable Standards 93
5.2.3.1 Instantaneous Maximum SAR Standard 94
5.2.3.2 Monthly Average SAR Standard 95
5.2.3.3 Nondegradation 97
5.2.4 Sources of SAR and Their Influence on Otter Creek 97
5.3 Metals 98
5.4 Suspended Solids 99
5.4.1 Relative Bed Stability Index 100
5.4.2 HII 100
5.4.3 Riparian and Bank Condition 100
5.4.4 NRCS Assessment 100
5.4.5 In-Stream Sediment Concentrations 103
5.4.6 Sediment Source Identification and Load Quantification 105
6.0 Pumpkin Creek 107
6.1 Salinity 108
6.1.1 Spatial Characterization 110
6.1.2 Relationship between Specific Conductance and Discharge Ill
6.1.3 Comparison to Applicable Standards Ill
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Table of Contents
6.1.3.1 Instantaneous Maximum Salinity Standard 112
6.1.3.2 Monthly Average Salinity Standard 113
6.1.3.3 Nondegradation 114
6.1.4 Sources of Salinity and Their Influence on Pumpkin Creek 115
6.2 SAR 115
6.2.1 Spatial Characterization 115
6.2.2 Relationship between SAR and Discharge 117
6.2.3 Comparison to Applicable Standards 118
6.2.3.1 Instantaneous Maximum SAR Standard 118
6.2.3.2 Monthly Average SAR Standard 119
6.2.3.3 Nondegradation 121
6.2.4 Sources of SAR and Their Influence on Pumpkin Creek 122
6.3 Thermal Modifications 122
6.3.1 Measured Stream Temperature 122
6.3.2 Comparison to Other Streams 125
6.3.3 Temperature Sources 128
6.3.3.1 Flow 128
6.3.3.2 Habitat Alterations 128
7.0 Tongue River Reservoir 131
7.1 Salinity 132
7.2 Sodium Adsorption Ratio 134
7.3 Nutrients 135
7.3.1 Total Phosphorus and Total Nitrogen 135
7.3.2 Chlorophyll-a 138
7.3.3 Comparison to Other Reservoirs and Literature Values 138
7.3.4 Carlson's TSI 141
7.3.5 Dissolved Oxygen 142
7.3.6 Nutrient Sources 145
7.4 Suspended Solids 147
7.4.1 Measured Data 147
7.4.2 Sediment Sources 147
8.0 Summary and Conclusions 149
9.0 References 151
V
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Table of Contents
Appendices
Appendix A - Montana Narrative Water Quality Standards
Appendix B - Methodology for Applying Montana's Water Quality Standards
Appendix C - Coefficients for Calculating Montana Metals Standards
Appendix D - Wyoming and Northern Cheyenne Water Quality Standards
Appendix E - Monthly SC Analysis
Appendix F - Monthly SAR Analysis
Appendix G - Groundwater Concentrations in the Hanging Woman Creek, Otter Creek, and Pumpkin
Creek Watersheds
Appendix H - Hydrology of the Tongue River Watershed
Appendix I - Biological Assemblages and Application of the Multimetric Index (MMI), and the River
Invertebrate Prediction and Classification System (RIVPACS) in the Tongue River
Watershed
Appendix J - Tongue River Model Scenarios
Appendix K - Comparison of Great Plains Streams Water Chemistry Data
Appendix L - 2003 Water Quality Sampling Data
VI
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Table of Contents
Tables
Table 1-1.
Table 1-2.
Table 1-3.
Table 2-1.
Table 2-2.
Table 2-3.
Table 2-4.
Table 3-1.
Table 3-2.
Table 3-3.
Table 3-4.
Table 3-5.
Table 3-6.
Table 3-7.
Table 3-8.
Table 3-9.
Table 3-10.
Table 3-11.
Table 3-12.
Table 3-13.
Table 3-14.
Table 3-15.
Table 3-16.
Table 3-17.
Table 3-18.
Table 3-19.
Table 3-20.
Table 3-21.
Table 3-22.
Table 3-23.
Table 3-24.
Table 3-25.
Table 3-26.
Table 3-27.
Table 5-1.
Streams and impaired beneficial uses listed on the Montana 1996 and 2006 303(d) lists for the
Tongue River watershed 3
Probable causes of water quality impairment in the Tongue River watershed identified in the 1996
and 2006 Montana 303(d) lists 4
Impaired streams within the Tongue River watershed on the 2006 Wyoming 303(d) list 6
Montana's numeric salinity (measured as electrical conductivity (EC)) criteria fort the Tongue River
watershed 7
Montana's numeric SAR criteria for the Tongue River watershed 7
Aquatic life standards for dissolved oxygen (mg/L) 8
Montana numeric criteria for metals 8
Specific conductance (SC) data for the main stem Tongue River. 10
Specific conductance statistics for various time periods, flows, and stations on the mainstem
Tongue River, all available grab samples. 13
Average monthly SC data and exceedances of the average monthly water quality standards for the
Tongue River for the last five years assuming > four grab and/or continuous samples per month.118
Simulated mean SC under three modeled scenarios and percent change from the existing condition
scenario 24
SAR data for the main stem Tongue River. 25
SAR statistics for various time periods, flows, and stations on the mainstem Tongue River, all
available grab samples. 28
Average monthly SAR data and exceedances of the average monthly water quality standards for
the Tongue River for the last five years assuming > four samples per month.1 32
Summary of hardness data in the Tongue River 36
Summary of metals data in the Tongue River between the MT-WY border and the Tongue River
Reservoir 37
Summary of the iron exceedances in the Tongue River between the MT-WY border and the
Tongue River Reservoir 37
Stations with metals data - Tongue River Reservoir Dam to the T&Y Diversion Dam 38
Summary of metals data in the Tongue River between the Tongue River Reservoir Dam and the
T&Y Diversion Dam 38
Summary of the iron exceedances in the Tongue River between the Tongue River Reservoir Dam
and the T&Y Diversion Dam 39
Summary of metals data in the Tongue River between the T&Y Diversion Dam and the mouth 40
Summary of the iron exceedances in the Tongue River between the T&Y Diversion Dam and the
Mouth 40
Summary of the copper exceedances in the Tongue River between the T&Y Diversion Dam and the
Mouth 41
Summary of the lead exceedances in the Tongue River between the T&Y Diversion Dam and the
Mouth 42
Summary of the cadmium exceedances in the Tongue River between the T&Y Diversion Dam and
the Mouth 43
Summary of the zinc exceedances in the Tongue River between the T&Y Diversion Dam and the
Mouth 43
Summary of the zinc exceedances in the Tongue River between the T&Y Diversion Dam and the
Mouth 44
Paired total and dissolved metals concentrations in the Tongue River at Miles City, Montana 46
Summary of TSS and SSC grab samples in the mainstem Tongue River. 48
TSS/SSC statistics for various time periods and stations on the mainstem Tongue River, all
available grab samples. 51
Summary of suspended solids concentrations collected upstream and downstream of the Tongue
River Reservoir. Montana 52
Relationship between flow and SSC at four representative Tongue River stations 55
Estimated yearly suspended solids load in the Tongue River, Montana (tons/year) 55
Summary of surface water sulfate data in the Tongue River (mg/L) 56
Specific conductance (SC) data for the main stem Otter Creek. 82
VII
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Table of Contents
Table 5-2.
Table 5-3.
Table 5-4.
Table 5-5.
Table 5-6.
Table 5-7.
Table 5-8.
Table 5-9.
Table 5-10
Table 5-11
Table 5-12
Table 6-1.
Table 6-2.
Table 6-3.
Table 6-4.
Table 6-5.
Table 6-6.
Table 6-7.
Table 6-8.
Table 6-9.
Table 6-10
Table 7-1.
Table 7-2.
Table 7-3.
Table 7-4.
Table 7-5.
Table 7-6.
Table 7-7.
Table 7-8.
Table 7-9.
Table 7-10.
Specific conductance statistics for various time periods, flows, and stations on the mainstem Otter
Creek, all available grab samples. 85
SC data and exceedances of the instantaneous maximum water quality standard for Otter Creek;
daily and grab samples 87
Average monthly SC data and exceedances of the average monthly water quality standard for Otter
Creek for the last five years assuming > four daily and/or grab samples per month 88
SAR data for the main stem Otter Creek. 90
SAR statistics for various time periods, flows, and stations on the mainstem Otter Creek, all
available grab samples. 92
SAR data and exceedances of the Instantaneous maximum water quality standards for Otter
Creek: daily and grab samples 94
Average monthly SAR data and exceedances of the average monthly water quality standards for
Otter Creek: daily and grab samples 96
Summary of metals data in Otter Creek 98
Summary of the iron exceedances in Otter Creek 99
Results of the NRCS riparian assessment in Otter Creek 101
Summary of TSS and SSC data. Otter Creek 103
Specific conductance (SC) data for the mainstem Pumpkin Creek. 108
Specific conductance statistics for various time periods, flows, and stations on the mainstem
Pumpkin Creek, all available grab samples. 110
SC data and exceedances of the instantaneous maximum water quality standards for Pumpkin
Creek: daily and grab samples 112
Average monthly SC data and exceedances of the average monthly water quality standards for
Pumpkin Creek assuming > four daily and/or grab samples per month 113
SAR data for the mainstem Pumpkin Creek. 115
SAR statistics for various time periods, flows, and stations on the mainstem Pumpkin Creek, all
available grab samples. 116
SAR data and exceedances of the Instantaneous maximum water quality standards for Pumpkin
Creek: daily and grab samples 118
Average monthly SAR data and exceedances of the average monthly water quality standards for
Pumpkin Creek near the mouth - USGS Gage 06308400; daily and grab samples 120
Summary of surface water temperature data (grab samples) in Pumpkin Creek (°F) 123
Results of the NRCS riparian assessment in Pumpkin Creek 129
Summary of all available surface water SC data, Tongue River Reservoir (pS/cm) 132
Summary of SAR data. Tongue River Reservoir (March 2-October 31) 134
Summary of all available total phosphorus data, Tongue River Reservoir (mg/L) 135
Summary of all available total nitrogen data, Tongue River Reservoir (mg/L) 136
Summary of all available chlorophyll a data in the Tongue River Reservoir (|ig/L) 138
Number of nutrient samples per reservoir and associated period of record 138
Carlson's TSI values for the Tongue River Reservoir 142
Summary of dissolved oxygen data. Tongue River Reservoir (mg/L) 143
Total modeled nutrient loads for various scenarios for the Tongue River watershed draining to the
Tongue River Reservoir (modeling subbasin 3001) 146
Summary of all available TSS data. Tongue River Reservoir (mg/L) 147
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Figures
Figure 1-1. Location of the Tongue River watershed 2
Figure 1-2. Location of the Tongue River watershed and the 303(d) listed streams 5
Figure 3-1. Tongue River watershed and location of the main stem Tongue River surface water salinity
monitoring stations (stations with 10 or more sample dates are shown) 11
Figure 3-2. Specific conductance statistics for USGS stations with 10 or more samples in the main stem
Tongue River. The entire period of record is shown for each station; grab samples only 12
Figure 3-3. Relationship between flow and SC at selected USGS stations on the main stem Tongue River.
Entire period of record is shown; grab samples only 15
Figure 3-4. Specific conductance versus flow percentile (growing season only) for the Tongue River at Miles
City, Montana (USGS Gage 06308500). Entire period of record is shown; continuous data and
grab samples 16
Figure 3-5. Average monthly growing season SC values at the Birney Day School Bridge (past five years with
4 or more samples per month) versus flow percentile 19
Figure 3-6. Average monthly growing season SC values at Miles City (past five years with 4 or more samples
per month) versus flow percentile 19
Figure 3-7. Application of Montana's nondegradation policy to electrical conductivity (EC) in the main stem
Tongue River (MDEQ. 2007) 20
Figure 3-8. SC data and nondegradation thresholds for USGS gages downstream of the Tongue River
Reservoir Entire period of record is shown: grab samples only 21
Figure 3-9. SC data and nondegradation thresholds for USGS gages upstream of the Tongue River Reservoir.
Entire period of record is shown: grab samples only 22
Figure 3-10. Modeled existing versus natural salinity (SC) in the Tongue River at State Line (USGS Gage
06306300) and Miles City (USGS Gage 06308500) 24
Figure 3-11. Tongue River watershed and location of the mainstem Tongue River surface water SAR monitoring
stations (stations with 10 or more sample dates are shown) 26
Figure 3-12. SAR statistics for USGS stations with 10 or more samples in the main stem Tongue River. The
entire period of record is shown for each station: grab samples only 27
Figure 3-13. Relationship between flow and SAR at selected USGS stations on the main stem Tongue River.
Entire period of record is shown: grab samples only 30
Figure 3-14. SAR data and nondegradation thresholds for the Tongue River downstream of the Tongue River
Reservoir Dam. Entire period of record is shown: grab samples only 34
Figure 3-15. SAR data and nondegradation thresholds for the Tongue River upstream of the Tongue River
Reservoir Dam. Entire period of record is shown: grab samples only 35
Figure 3-16. Total metals concentrations versus TSS/SSC data in the Tongue River at Miles City (USGS Gage
06308500). Period of Record June 1999 to August 2006 45
Figure 3-17. Synoptic sampling results for total and dissolved metals concentrations at various sites in the
Tongue River. Montana (May 24-26. 2004) 47
Figure 3-18. Tongue River watershed and location of the TSS/SSC monitoring stations (stations with 10 or more
sample dates are shown) 49
Figure 3-19. TSS/SSC statistics for USGS stations with 10 or more samples in the mainstem Tongue River.
The entire period of record is shown for each station: grab samples only 50
Figure 3-20. Relationship between flow and SSC in the Tongue River near the Brandenberg Bridge, Montana. 54
Figure 3-21. Sulfate data at three USGS stations in the Tongue River. Montana 56
Figure 4-1. Surface water quality monitoring stations on the main stem of Hanging Woman Creek 59
Figure 4-2. Statistics for USGS stations with 10 or more samples in the mainstem Hanging Woman Creek.
The entire period of record is shown for each station 60
Figure 4-3. Relationship between flow and SC at selected USGS stations on the main stem of Hanging Woman
Creek. Entire period of record is shown: grab samples only 61
Figure 4-4. Specific conductance versus flow percentile for Hanging Woman Creek near the mouth (USGS
Gage 06307600). Entire period of record is shown: grab samples only 62
Figure 4-5. SC data and nondegradation thresholds for Hanging Woman Creek (near the mouth). Entire period
of record is shown: grab samples only 64
Figure 4-6. SAR Statistics for USGS stations with 5 or more samples in the mainstem Hanging Woman Creek.
The entire period of record is shown for each station: grab samples only 65
Figure 4-7. Relationship between flow and SAR at selected USGS stations on the main stem of Hanging
Woman Creek. Entire period of record is shown: grab samples only 67
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Figure 4-8. SAR versus flow percentile for Hanging Woman Creek near the mouth (USGS Gage 06307600).
Growing season grab samples only 68
Figure 4-9. SAR data and nondegradation thresholds for Hanging Woman Creek (near the mouth). Entire
period of record is shown; grab samples only 70
Figure 4-10. NRCS riparian assessment for Hanging Woman Creek 76
Figure 4-11. TSS and SSC data for Hanging Woman Creek near the mouth (USGS Gage 06307600) 78
Figure 4-12. TSS and SSC data for Hanging Woman Creek stations 06307540, 06307570, and 06307600 78
Figure 5-1. Surface water quality monitoring stations on the main stem of Otter Creek 83
Figure 5-2. Statistics for stations with 10 or more samples in the mainstem Otter Creek. The entire period of
record is shown for each station; grab samples only 84
Figure 5-3. Relationship between flow and SC at selected USGS stations on the main stem of Otter Creek.
Entire period of record is shown; grab samples only 86
Figure 5-4. Specific conductance versus flow percentile for Otter Creek near the mouth (USGS Gage
06307740). Entire period of record is shown; grab samples only 87
Figure 5-5. SC data and nondegradation thresholds for Otter Creek (near the mouth). Entire period of record is
shown: grab samples only 89
Figure 5-6. SAR statistics for USGS stations with 10 or more samples in the mainstem Otter Creek. The entire
period of record is shown for each station: grab samples only 91
Figure 5-7. Relationship between flow and SAR at selected USGS stations on the mainstem of Otter Creek.
Entire period of record is shown: grab samples only 93
Figure 5-8. SAR versus flow percentile for Otter Creek near the mouth (USGS Gage 06307740). Growing
season grab samples only 94
Figure 5-9. SAR data and nondegradation thresholds for Otter Creek (near the mouth). Entire period of record
is shown: grab samples only 97
Figure 5-10. NRCS assessment for Otter Creek 102
Figure 5-11. TSS and SSC data for Otter Creek near the mouth (USGS Gage 06307740) 104
Figure 5-12. TSS and SSC data for Otter Creek stations with 10 or more samples per site (sites 06307740,
06307725. 06307717. and 06307665) 104
Figure 6-1. Surface water quality monitoring stations on the main stem of Pumpkin Creek 109
Figure 6-2. Statistics for stations with 10 or more samples in the mainstem Pumpkin Creek. The entire period
of record is shown for each station: grab samples only 110
Figure 6-3. Relationship between flow and SC at selected USGS stations on the mainstem of Pumpkin Creek.
Entire period of record is shown: grab samples only 111
Figure 6-4. Specific conductance versus flow percentile for Pumpkin Creek near the mouth (USGS Gage
06308400). Entire period of record is shown: grab samples only 112
Figure 6-5. SC data and nondegradation thresholds for Pumpkin Creek (USGS Gage 06308400). Entire period
of record is shown: grab samples only 114
Figure 6-6. SAR statistics for stations with 10 or more samples in the mainstem Pumpkin Creek. The entire
period of record is shown for each station: grab samples only 116
Figure 6-7. Relationship between flow and SAR at selected USGS stations on the mainstem of Pumpkin
Creek. Entire period of record is shown: grab samples only 117
Figure 6-8. SAR versus flow percentile for Pumpkin Creek near the mouth (USGS Gage 06308400). Growing
season grab samples only, entire period of record 118
Figure 6-9. SAR data and nondegradation thresholds for Pumpkin Creek (near the mouth). Entire period of
record is shown: grab samples only 121
Figure 6-10. Stream temperatures in Pumpkin Creek (all stations, grab samples) 123
Figure 6-11. Hourly stream temperatures in Pumpkin Creek at two stations. 2003 125
Figure 6-12. Average daily temperature at four sites in the Tongue River watershed, April-October, 2003 126
Figure 6-13. Comparison of water temperature data for 16 Great Plains streams in southeast Montana and
northeast Wyoming. 1974-1985 127
Figure 6-14. NRCS in-channel assessment for Pumpkin Creek (Little Pumpkin Creek to the mouth) 130
Figure 7-1. Tongue River Reservoir bathymetry and location of the water quality monitoring stations 133
Figure 7-2. SC sampling by depth for 2003 Tongue River Reservoir sampling at station near dam
(Y15TNGRR03) 134
Figure 7-3. Total phosphorus concentrations at depth in the Tongue River Reservoir near the Dam (Station
Y15TNGRR03) 136
Figure 7-4. TN:TP ratio for the Tongue River Reservoir 137
x
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Figure 7-5. Relationship between total phosphorus and chlorophyll a for all paired samples in the Tongue River
Reservoir 137
Figure 7-6. Comparison of total phosphorus data from the Tongue River Reservoir to other reservoirs and
literature values 140
Figure 7-7. Comparison of total nitrogen data from the Tongue River Reservoir to other reservoirs and
literature values 140
Figure 7-8. Comparison of chlorophyll-a data from the Tongue River Reservoir to other reservoirs and literature
values 141
Figure 7-9. Dissolved oxygen data for Tongue River Reservoir by depth (2001 and 2003 sampling near TRR
Dam) 144
xi
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Executive Summary
EXECUTIVE SUMMARY
This document presents an assessment of water quality in the Tongue River, Tongue River Reservoir, and
Hanging Woman, Otter, and Pumpkin Creeks. This assessment is based on data and information through
September 2006 (this varies on a case-by-case basis depending upon data availability) and the focus is on
the listed pollutants and impaired beneficial uses from the 1996 and 2006 Montana Clean Water Act
Section 303(d) lists. Pollutants addressed included salinity, sodium adsorption ratio (SAR), metals,
sulfates, sediment, nutrients, dissolved oxygen, and temperature. The primary purpose of this assessment
was to compare the available water quality data to the applicable Montana water quality standards and, in
cases where exceedances of Montana's standards are observed, provide insight into the cause (i.e.,
natural, anthropogenic, or a combination of both) based on the results of modeling and other analyses.
This assessment has been conducted for informational purposes, outside of any regulatory context to
provide watershed stakeholders and decision makers with baseline information regarding the current
condition of the waters in the Tongue River Watershed. Formal interpretation of Montana's water quality
standards and 303(d) impairment decisions are beyond the scope of these analyses and are not provided.
A list of the waters and pollutants that have been addressed and qualitative, summary assessment results
are presented in Table 1. The results in this table are not provided as conclusions regarding water quality
impairment status under Clean Water Act Section 303(d). Rather, these summary results are intended to
identify where exceedances of Montana's water quality standards have been observed based on the data
considered in this assessment. The circumstances around the exceedances reported in Table 1 and details
regarding the magnitude, duration and frequency of the exceedances are presented in the document.
Water quality impairment status will be determined by the Montana Department of Environmental
Quality based on their interpretation of their water quality standards and application of their assessment
protocols.
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Executive Summary
Table 1. Summary listing of the waters and pollutants addressed and qualitative results.
Waterbody
Waterbody ID
Pollutants Addressed
Has the Standard or Indicator Value Been
Exceeded?
Tongue River-WY
Border to Tongue
River Reservoir
MT42B001-001
Salinity
Yes
SAR
No
Metals
Yes
Sulfate
Requires interpretation of Montana's
narrative standards
Tongue River - TRR
Dam to the
Confluence with
Hanging Woman
Creek
MT42B001-020
Salinity
No
SAR
No
Sulfate
Requires interpretation of Montana's
narrative standards
Sediment
Requires interpretation of Montana's
narrative standards
Tongue River-
Hanging Woman
Creek to T&Y
Diversion Dam
(MT42C001-001)
MT42C001-012
Salinity
Yes
SAR
No
Metals
Yes
Sediment
Requires interpretation of Montana's
narrative standards
Tongue River-T&Y
Diversion dam to
Mouth
(MT42C001-001)
MT42C001-011
Salinity
Yes
SAR
No
Metals
Yes
Sediment
Requires interpretation of Montana's
narrative standards
Tongue River
Reservoir
MT42B003-010
Salinity
No
SAR
No
Nutrients
Requires interpretation of Montana's
narrative standards
Dissolved oxygen
Yes
Sediment
Requires interpretation of Montana's
narrative standards
Hanging Woman
Creek
(MT42B002-003)
MT42B002-031
Salinity
Yes
SAR
Yes
Metals
Yes
Sediment
Requires interpretation of Montana's
narrative standards
Otter Creek
MT42C002-020
Salinity
Yes
SAR
Yes
Metals
Yes
Sediment
Requires interpretation of Montana's
narrative standards
Pumpkin Creek
MT42C002-060
Salinity
Yes
SAR
Yes
Temperature
Requires interpretation of Montana's
narrative standards
xiv
-------
Introduction
1.0 INTRODUCTION
This document presents an assessment of water quality in the Tongue River and includes a summary and
evaluation of available chemical, physical, and biological data for the water bodies in the Tongue River
Watershed that have previously appeared on Montana's 303(d) lists. The analyses presented in this report
specifically focus on the listed pollutants and impaired beneficial uses from the 1996a and 2006 Montana
303(d) lists (see Section 1.1). Salinity and sodium adsorption ratio (SAR) are also considered in each of
the subject streams to provide a watershed-scale perspective for these two pollutants, whether they
appeared on the 303(d) lists for these pollutants or not. The main stem Tongue River, the Tongue River
Reservoir, Hanging Woman Creek, Otter Creek, and Pumpkin Creek are addressed (Figure 1-1) and the
water quality characteristics of these water bodies within both Wyoming and Montana are considered.
This document compares the available water quality data to the applicable Montana water quality
standards and, where exceedances are observed, provides insight regarding the potential cause of the
exceedances (i.e., natural versus anthropogenic). Montana's water quality standards are used as a point of
reference. Formal interpretation of Montana's water quality standards and 303(d) impairment decisions
are outside the scope of these analyses and are not provided.
This document first presents the 303(d) list status of waters within the Tongue River watershed. This is
followed by a water body-by-water body review of the available chemical and physical data for each
listed water body.
The document entitled "Modeling Report for the Tongue River Watershed" (hereafter referred to as the
"Modeling Report") is a companion to this document and is incorporated by reference (USEPA, 2007).
The following detailed information and supporting technical analyses are presented in appendices:
Appendix A -
Appendix B -
Appendix C -
Appendix D -
Appendix E -
Appendix F -
Appendix G -
Appendix H -
Appendix I -
Appendix K -
Appendix L -
Montana Narrative Water Quality Standards
Methodology for Applying Montana's Water Quality Standards
Coefficients for Calculating Montana's Metals Standards
Wyoming and Northern Cheyenne Water Quality Standards
Monthly SC Analysis
Monthly SAR analysis
Groundwater Concentrations in Hanging Woman Creek, Otter Creek, and
Pumpkin Creek
Hydrology of the Tongue River Watershed
Biological Assemblages and Application of the Multi-Metric Index (MMI) and
the River Invertebrate Prediction and Classification System (RIVPACS) in the Tongue River
Watershed
Appendix J - Tongue River Model Scenarios
Comparison of Great Plains Streams Water Chemistry Data
2003 Water Quality Sampling Data
a At this point in time, Montana is compelled by a Settlement Agreement between the Montana Department of Environmental Quality, U.S.
Environmental Protection Agency, and Friends of the Wild Swan et. al to address waters appearing on the 1996 303(d) list even though a more recent
303(d) list has been completed and approved.
1
-------
Introduction
Brandenberg
Ashland
ythern
[eyenrie
Birney
Crow
Dayton
WYOMING
CUSTER;
COUNT
ROSEBUD*1
COUNTY
Lame Deer
BIG HORN
COUNTY,
f
POWDER RIVER
^COUNTY
Moorhead
BIG HORN
COUNTY
SHERIDAN
COUNTY
N
20 Miles
B Cites and Towns
Counties
Roads
/\ / Tongue River Malnstem
Streams
Tribal Land
~ Tongue River Watershed
Figure 1-1. Location of the Tongue River watershed.
2
-------
Introduction
1.1 Montana 303(d) List Status
A summary of the Montana 1996 and 2006 303(d) lists is provided in Table 1-1 and Table 1-2. Figure 1-
2 shows the locations of probable impaired and threatened segments within the Tongue River watershed,
as identified in the 1996 to 2006 303(d) lists. The Montana 1996 303(d) list reported that the Tongue
River, Tongue River Reservoir, Hanging Woman Creek, Otter Creek, and Pumpkin Creek were impaired
(MDEQ, 1996). In 2006, the Montana 303(d) list reported that the Tongue River, Tongue River
Reservoir, and Hanging Woman Creek were impaired (MDEQ, 2006a). Combined, the listed probable
causes of impairment for these waterbodies included flow alteration, nutrients, organic enrichment/low
dissolved oxygen, algal growth/chlorophyll-a, suspended solids/siltation, metals, other inorganics
(sulfate), salinity, total dissolved solids, chlorides, other habitat alterations, and thermal modifications.
The most common impaired beneficial uses appearing on the 303(d) lists were fisheries and aquatic life.
USEPA has made a determination that some categories of water quality impairment are not considered
pollutants subject to regulation under the Clean Water Act (Dodson, 2001). Causes of impairment,
including habitat alterations, fish habitat degradation, channel incisement, bank erosion, riparian
degradation, stream dewatering, and flow alterations have all been placed in a general category of
"pollution" for which TMDLs are not required. On the other hand, TMDLs are required to address
impairments caused by discrete "pollutants", such as heavy metals, nutrients, and sediment (Dodson,
2001). This document focuses on this latter impairment cause category, but attempts to understand the
relationships between general pollution problems (e.g., bank erosion) and those caused by specific
pollutants (e.g., sediment).
Table 1-1. Streams and impaired beneficial uses listed on the Montana 1996 and 2006 303(d) lists for
the Tongue River watershed.
Waterbody & Stream Description
Waterbody #
Use Class
Year
Aquatic Life
Fisheries
Drinking
Water
Swimmable/
(Recreation)
Agriculture
Industry
Tongue River-WY Border to Tongue
River Reservoir
MT42B001-001
B2
1996
P
P
N
2006
X
X
X
X
X
X
Tongue River Reservoir
MT42B003-010
B2
1996
P
P
P
2006
P
X
X
P
F
F
Tongue River - TRR Dam to the
Confluence with Hanging Woman Creek
MT42B001-020
B3
1996
P
p
2006
X
X
X
X
X
X
Tongue River - Hanging Woman Creek
to T&Y Diversion Dam
(MT42C001-001)
MT42C001-012
B3
1996
p
p
P
2006
X
X
X
X
X
X
Tongue River-T&Y Diversion Dam to
Mouth
(MT42C001-001)
MT42C001-011
B3
1996
p
p
p
2006
p
p
X
p
F
F
Hanging Woman Creek
(MT42B002-003)
MT42B002-031
C3
1996
p
p
P
2006
p
p
X
X
X
X
Otter Creek
MT42C002-020
C3
1996
p
p
P
2006
X
X
X
X
X
X
Pumpkin Creek
MT42C002-060
C3
1996
p
p
p
2006
X
X
X
X
X
X
F= Full Support; P= Partial Support; N= Not Supported; T= Threatened; X= Not Assessed (Insufficient Credible Data).
3
-------
Introduction
Table 1-2. Probable causes of water quality impairment in the Tongue River watershed identified in the
1996 and 2006 Montana 303(d) lists.
Waterbody
1996 Causes1
2006 Causes1
Tongue River-WY Border to Tongue River Reservoir
Flow alteration
Not Assessed
Tongue River Reservoir
Nutrients
Organic enrichment/
dissolved oxygen
Suspended solids
Chlorophyll-a
Tongue River - TRR Dam to the confluence with
Hanging Woman Creek
Flow alteration
Not Assessed
Tongue River - Hanging Woman Creek to T&Y
Diversion Dam
Flow alteration
Metals
Other inorganics
Salinity/TDS/chlorides
Suspended solids
Not Assessed
Tongue River-T&Y Diversion Dam to Mouth
Flow alteration
Metals
Other inorganics
Salinity/TDS/chlorides
Suspended solids
Low Flow Alterations
Hanging Woman Creek
Flow alteration
Metals
Salinity/TDS/chlorides
Siltation
Otter Creek
Metals
Other habitat alterations
Salinity/TDS/chlorides
Suspended solids
Not Assessed
Pumpkin Creek
Flow alteration
Salinity/TDS/chlorides
Thermal modifications
Not Assessed
'Nonpollutants for which TMDLs are not required are italicized.
4
-------
Introduction
yenne
Crow
Temp#rntur«
MONTANA
WYOMING
10 20 40 Miles
' ¦ ' ' ' ' '
WYOMING
Streams
Johnson
County
1398 Littoo? are fltnwi in BED
2MB uanffs « &JU£
ItateffiiS '.Id not require TMCu
Counties
TribaJ Land
[ | Tongue River Watershed
Wyoming 303(d) Listed Streams
Montana SOjUtlj Listed Streams
Custer
County
twder River
County
All Other Wyoming Streams -Fecal CoHforms
MONTANA
SclMy/reS/C^r sri rfe •
GtfM r bnarga
Tata) Suspendad Solids
Metila
Flow Alteration*
Sarin Ify/TQS fCh I oiidt s
Other Inoroanlct
Total Suspended Solids
MataJf
r'6ii Arfefflfioa#
SaltoMynTDSJChlortde*
Therm aS Modifications
Pott AfterJtflom
Big Horn
County
Hu1riin4»
Or®«n(c EnOflimtrit'Low DC
Totvl Suspended SoUdr
Algal GcowthrChlorophyll-a
^Marvgenesa
-Sadlmant
Si I rat i vi
Saiinit
WtfaU
A
¦> TD5iCh1oride»
?*r*t}ont
K "5 a I In lly/TD S/Ch I on da a
Total Suspended Sal Ida
Matata
_jytrmr ^ahiTaf ^ITararaim
Figure 1-2. Location of the Tongue River watershed and the 303(d) listed streams.
5
-------
Introduction
1.2 Wyoming 303(d) List Status
A summary of the 2006 Wyoming 303(d) list is provided in Table 1-3. Figure 1-2 shows the locations of
impaired and threatened segments within the Tongue River watershed, as identified in the most recent
approved Wyoming 303(d) list (WDEQ, 2006). While this document does not specifically address the
water body/pollutant combinations appearing on Wyoming's 303(d) list, this information is presented to
provide a watershed scale perspective of potential water quality issues.
Table 1-3. Impaired streams within the Tongue River watershed on the 2006 Wyoming 303(d) list.
Waterbody & Stream Description
Use Class
Aquatic Life
Fisheries
Drinking
Water
Contact
Recreation
Cause of
Impairment
Tongue River - Goose Creek downstream
2AB
N
Temperature
Beaver Creek - Big Goose Creek to upstream
2AB
N
Fecal Coliform
Big Goose Creek - Sheridan to above Beckton
2AB
N
Fecal Coliform
Columbus Creek - Confluence with Tongue River to above
Highway 14
2AB
N
Fecal Coliform
Five Mile Creek - Confluence with Tongue River to above
Ranchester
3B
N
Fecal Coliform
Goose Creek - Confluence of Big and Little Goose Creeks to
downstream
2AB
N
Fecal Coliform
Goose Creek - Within City of Sheridan
2AB
N
N
Sediment
Jackson Creek - Little Goose Creek to upstream
2AB
N
Fecal Coliform
Kruse Creek - Little Goose Creek to upstream
2AB
N
Fecal Coliform
Little Goose Creek - Sheridan upstream to above Big Horn
2AB
N
Fecal Coliform
Little Goose Creek - Within City of Sheridan
2AB
N
N
Sediment
Little Tongue River - Confluence with Tongue River to above
Dayton
2AB
N
Fecal Coliform
McCormick Creek - Little Goose Creek to upstream
2AB
N
Fecal Coliform
North Tongue River - Confluence of Bull Creek upstream to
above Hwy 14A
1
N
Fecal Coliform
Park Creek - Big Goose Creek to upstream
2AB
N
Fecal Coliform
Prairie Dog Creek - Entire Prairie Dog Creek Drainage
2AB
N
Fecal Coliform
Prairie Dog Creek-Tongue River to upstream
2AB
N
Manganese
Rapid Creek - Big Goose Creek to upstream
2AB
N
Fecal Coliform
Sacket Creek - Little Goose Creek to upstream
2AB
N
Fecal Coliform
Smith Creek - Confluence with Tongue River to above Dayton
2AB
N
Fecal Coliform
Soldier Creek - Goose Creek to upstream
2AB
N
Fecal Coliform
F= Full Support; P= Partial Support; N= Not Supported; T= Threatened; X= Not Assessed (Insufficient Credible Data).
6
-------
Applicable Water Quality Standards
2.0 APPLICABLE WATER QUALITY STANDARDS
The following pollutants have been considered in this analysis: electrical conductivity (EC), sodium
adsorption ratio (SAR), sediment, nutrients, dissolved oxygen, metals, and temperature. The Tongue
River watershed is encompassed by four jurisdictional entities that have, or could have, applicable water
quality standards. These entities are the State of Montana, the State of Wyoming, the Northern Cheyenne
Tribe, and the Crow Tribe. The States of Wyoming and Montana have adopted water quality standards
under Section 303 of the Clean Water Act for water bodies within each State's respective jurisdiction.
The Northern Cheyenne Tribe has received Treatment as a State for Clean Water Act water quality
standards purposes but has not yet submitted standards to EPA for approval for Clean Water Act
purposes. The Northern Cheyenne Tribe has tribally-adopted water quality standards. The Crow Tribe
has not received Clean Water Act Treatment as a State for Clean Water Act purposes and does not have
tribally-adopted water quality standards. This assessment focuses on Montana's water quality standards.
Montana has numeric water quality standards for EC, SAR, dissolved oxygen, and metals. Sediment,
nutrients and temperature are addressed in Montana with narrative standards. Montana's numeric
standards are summarized in Table 2-1 to Table 2-4 and the narrative standards are presented in Appendix
A. Details regarding how both the numeric and narrative standards have been applied to facilitate a
comparison to the available water quality data are provided in Appendix B. The Wyoming and Northern
Cheyenne Tribal water quality standards are presented in Appendix D. The Crow Tribe does not, at this
time, have approved or adopted water quality standards.
Throughout this document, Montana's numeric water quality standards for EC and SAR are used as a
watershed-wide, common point of reference for purposes of characterizing current water quality
conditions in both Montana and Wyoming. This is not intended to imply that Montana's water quality
standards are directly applicable within the jurisdictional boundaries of Wyoming. Montana's values are
used only to provide a single watershed-scale point of reference.
Table 2-1. Montana's numeric salinity (measured as electrical conductivity (EC)) criteria fort the
Tongue River watershed.
Waterbody
Season
Monthly Average EC
(|jS/cm)
Maximum EC (pS/cm)
Tongue River
Nov 1 - Mar 1
1,500
2,500
Mar2-Oct 31
1,000
1,500
Tongue River Tributaries
Nov 1 - Mar 1
500
500
Mar 2 - Oct 31
500
500
Tongue River Reservoir
Nov 1 - Mar 1
1,000
1,500
Mar2-Oct 31
1,000
1,500
MDEQ, 2006b
Table 2-2. Montana's numeric SAR criteria for the Tongue River watershed.
Waterbody
Season
Monthly Average SAR
Maximum SAR
Tongue River
Nov 1 - Mar 1
5.0
7.5
Mar2-Oct 31
3.0
4.5
Tongue River Tributaries
Nov 1 - Mar 1
5.0
7.5
Mar2-Oct 31
3.0
4.5
Tongue River Reservoir
Nov 1 - Mar 1
3.0
4.5
Mar2-Oct 31
3.0
4.5
MDEQ, 2006b
7
-------
Applicable Water Quality Standards
Table 2-3. Aquatic life standards for dissolved oxygen (mg/L).
Time Period
Use Class B-2
Use Classes B-3 and C-3
Early Life Stages''
Other Life Stages
Early Life Stages
Other Life Stages
30-day average
NA
6.5
NA
5.5
7-day average
9.5 (6.5)
NA
6.0
NA
7-day average minimum
NA
5.0
NA
4.0
1-day minimum
8.0 (5.0)
4.0
5.0
3.0
"These are water column concentrations recommended to achieve the required intergravel DO concentrations shown in parentheses. For species that
have early life stages exposed directly to the water column, the figures in parentheses apply.
Table 2-4. Montana numeric criteria for metals.
Parameter
Aquatic Life (acute) (|jg/L)''
Aquatic Life (chronic) (|jg/L)b
Human Health
(M9/L)"
Arsenic (TR)
340
150
10
Cadmium (TR)
6.74 @310 mg/L hardness0
0.63 @310 mg/L hardness0
5
Chromium (III) (TR)
4,554 @310 mg/L hardness0
218 @310 mg/L hardness0
—
Copper (TR)
41 @310 mg/L hardness0
25 @ 310 mg/L hardness0
1,300
Iron (TR)
—
1,000
—
Lead (TR)
345 @310 mg/L hardness0
13 @ 310 mg/L hardness0
15
Nickel (TR)
1,222 @310 mg/L hardness0
136 @ 310 mg/L hardness0
100
Selenium (TR)
20
5
50
Silver (TR)
28 @ 310 mg/L hardness0
—
100
Zinc (TR)
312 @ 310 mg/L hardness0
312 @310 mg/L hardness0
2,000
aMaximum allowable concentration.
bNo four-day (96-hour) or longer period average concentration shall exceed these values.
cStandard is dependent on the hardness of the water, measured as the concentration of total hardness at the time of sampling (CaCOs) (mg/L). The
average hardness of the Tongue River (310 mg/L) is presented in this table for an example.
TR - Total Recoverable.
8
-------
Tongue River
3.0 TONGUE RIVER
The Tongue River flows 286 miles from its origin in the Big Horn Mountains in Wyoming to the
confluence with the Yellowstone River near Miles City, Montana (see Figure 1-1). The total watershed
covers roughly 5.400 square miles. In 1996, Montana DEQ included four segments of the Tongue River
on the 303(d) list of impaired waters - Tongue River from the Wyoming border to the Tongue River
Reservoir (MT42B001-001); Tongue River from
the Tongue River Reservoir Dam to the
confluence with Hanging Woman Creek
(MT42B001-020); Tongue River from the
confluence with Hanging Woman Creek to the
T&Y Diversion Dam (MT42C001-012); and
Tongue River from the diversion dam to the
mouth (MT42C001-011) (see Table 1-1) (MDEQ,
1996). However, the basis for the 1996 listings is
unknown. A revised listing for each segment
appeared on Montana's 2006 303(d) list, and only
the Tongue River from the T&Y Diversion Dam
to the mouth was listed as impaired, and only due
to flow alterations (see Table 1-1 and Table 1-2)
(MDEQ, 2006a).
This analysis specifically addresses the listed
pollutants and impaired beneficial uses from the Montana 1996 and 2006 303(d) lists (i.e., impairments to
the agriculture, warm-water fishery, and aquatic life beneficial uses associated with
salinity/TDS/chlorides, suspended solids, sulfates, and metals). Sodium adsorption ratio (SAR) is also
addressed given its potential importance related to future Coal Bed Methane development in the
watershed. The purpose of this analysis is to determine if Montana's water quality standards are currently
exceeded in the Tongue River, and, if so, provide insight into the potential cause of the exceedance (i.e.,
natural versus anthropogenic).
Tongue River near Ashland, Montana
(Photo by NRCS)
The remainder of this section includes summaries
and evaluations of available data, and
comparisons between the available data and the
applicable Montana water quality standards for
salinity, sulfates, chlorides, suspended solids, and
metals. Biological data for the Tongue River are
discussed in Appendix I, and Appendix H
provides a general overview of the hydrologic
characteristics of the Tongue River watershed
The Tongue River Reservoir is discussed in
Section 7.0.
Tongue River near the Montana-Wyoming state line
(Photo by Tetra Tech, Inc.)
9
-------
Tongue River
3.1 Salinity
Salinity in the Tongue River is measured primarily as specific conductance (SC), with units of
microSiemens per centimeter. SC data for the Tongue River are available from the late 1950's to the
present, and include both grab and continuous samples. Grab samples are available from over 100
stations in the Tongue River in Montana and Wyoming, dating from 1959 to 2006, and collected by
multiple governmental agencies and private organizations. USGS also collected continuous flow and
salinity data at the Tongue River at Monarch, WY (06299980), State Line (06306300), below the Tongue
River Reservoir (06307500), Birney Day School Bridge (06307616), Brandenberg Bridge (06307830),
above the T&Y Diversion Dam (06307990), and Miles City (06308500) for various years between 1980
and the present. The available data are listed in Table 3-1 and the sample site locations are shown in
Figure 3-1. Where summary statistics are provided in the following sections (i.e., mean, median,
maximum, minimum), only salinity grab samples are used so that the continuous data do not bias the
re suits b
Table 3-1. Specific conductance (SC) data for the main stem Tongue River.1
Segment
Station ID
Station Name
Agency
River
Mile
n
Period of
Record
Headwaters to the MT-WY
Border
06298000
Tongue River Near Dayton. WY
USGS
271.3
216
1966-1981:
1998-2002
06299980
Tongue River at Monarch. WY
USGS
246.3
744
1974-1983:
2004-2006
MT-WY Border to the Tongue
River Reservoir
06306300
Tongue River at State Line Near
Decker. MT
USGS
215.4
3.703
1985-2006
1975TO02
Tongue River just upstream of the
Tongue River Reservoir
MDEQ
212.1
11
1974-1977
Tongue River Reservoir Dam to
the T&Y Diversion Dam
2075T004
Tongue River just downstream of the
Tongue River Reservoir Dam
MDEQ
201.2
13
1974-1977
06307500
Tongue River at Tongue River Dam
Near Decker, MT
USGS
201.0
3,126
1975-2006
2277TO01
Tongue River at confluence with
Hanging Woman Creek
MDEQ
179.5
27
1975-1979;
1990
2278TO01
Tongue River downstream of Hanging
Woman Creek
MDEQ
165.2
19
1974-1977
06307610
Tongue River Below Hanging Woman
Creek Near Birney, MT
USGS
164.9
66
1974-1979
06307616
Tongue River at Birney Day School
Bridge Near Birney, MT
USGS
154.3
961
1979-2006
2579TO02
Tongue River near Ashland, MT
MDEQ
125.8
13
1975-1977
06307830
Tongue River Below Brandenberg
Bridge Near Ashland, MT
USGS
88.1
1699
1974-1985;
2000-2006
06307990
Tongue River Above T&Y Diversion
Dam Near Miles City, MT
USGS
28.0
410
2004-2006
T&Y Diversion Dam to the
Mouth
3582TO01
Tongue River downstream of the T&Y
Dam
MDEQ
8.2
25
1973-1980
06308500
Tongue River at Miles City, MT
USGS
2.5
1178
1959;
1962-2006
Stations with 10 or more samples are included in this table. Entire period of record is shown. Highlighted stations are used in the analyses presented
in the following sections.
b Continuous salinity data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years
of record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
10
-------
Tongue River
06308500
\358ZTO01
¦4 06307990
kiOS307830
lyenne
* 0630761
¦06507610,
» 2278T001
2277T001
Od 307500
MONTANA
WYOMING
'I975T002
06306300j
40 Miles
_i I
WYOMNG
¦ Water Quality Monitoring Stations
Streams
| Ccwnties
Tribal Land
| | Tongue River Watershed
Rosebud
County
Shot I d an
County
MONTANA
Figure 3-1. Tongue River watershed and location of the main stem Tongue River surface water salinity
monitoring stations (stations with 10 or more sample dates are shown).
11
-------
Tongue River
3.1.1 Spatial Characterization
The USGS sample stations highlighted above in Table 3-1 have been used to provide a general spatial
characterization of SC in the Tongue River. As shown in Figure 3-2 and Table 3-2, specific conductance
increases in a downstream direction, from a mean of 238 (iS/cm at Dayton, Wyoming, to 589 (iS/cm at
the Stateline, and 831 (iS/cm at Miles City. The largest increase in mean salinity per river mile occurs
between Dayton, Wyoming and Monarch, Wyoming, where there is an average increase of 7.0 (iS/cm per
river mile. The next highest increase in average salinity occurs between Monarch, Wyoming and the
Montana-Wyoming Stateline (5.7 (iS/cm increase per river mile). The increase in average salinity per
river mile is relatively low downstream of the Tongue River Reservoir, with a maximum increase of 1.8
(iS/cm occurring between the Birney Day School Bridge and the Brandenberg Bridge.
—~—75th Percentile —¦—25th Percentile a Median —x—Average —sk—Max —•—Min
River Mile (miles from the mouth)
Figure 3-2. Specific conductance statistics for USGS stations with 10 or more samples in the main stem
Tongue River. The entire period of record is shown for each station; grab samples only.
12
-------
Tongue River
Table 3-2. Specific conductance statistics for various time periods, flows, and stations on the
mainstem Tongue River, all available grab samples.1
Station
Statistic
Full Period of
Record
Last Five
Years''
Low
Flow'
High
Flow'
Average
Flow'
Tongue River at Dayton, WY
(USGS Gage 06298000)
n
216
1
58
54
104
Min
50
222
200
121
50
Max
360
222
340
260
360
Mean
238
222
269
178
252
Median
250
222
268
172
255
Tongue River at Monarch, WY
(USGS Gage 06299980)
n
135
44
33
33
67
Min
170
193
393
170
272
Max
660
535
560
520
660
Mean
413
384
469
288
445
Median
432
404
460
263
450
Tongue River at State Line Near
Decker, MT
(USGS Gage 06306300)
n
241
95
60
60
120
Min
175
186
495
175
232
Max
1,280
990
1,280
991
862
Mean
589
624
747
325
640
Median
630
636
730
265
635
Tongue River at Tongue River Dam
Near Decker, MT
(USGS Gage 06307500)
n
299
67
75
74
150
Min
190
282
430
190
289
Max
996
800
931
947
996
Mean
617
620
718
411
669
Median
658
653
728
369
681
Tongue River at Birney Day School
Bridge Near Birney, MT
(USGS Gage 06307616)
n
227
66
57
57
113
Min
198
319
476
229
198
Max
1,080
807
990
785
1,080
Mean
632
634
749
420
680
Median
662
663
756
390
681
Tongue River Below Brandenberg
Bridge Near Ashland, MT
(USGS Gage 06307830)
n
198
82
49
49
99
Min
260
337
640
260
408
Max
1,300
1,070
1,300
1,150
1,260
Mean
751
730
865
560
788
Median
780
759
859
490
780
Tongue River Above T&Y Diversion
Dam Near Miles City, MT
(USGS Gage 06307990)
n
37
37
9
9
19
Min
351
351
830
351
579
Max
1,000
1,000
1,000
772
963
Mean
764
764
939
518
798
Median
830
830
947
455
831
Tongue River at Miles City, MT
(USGS Gage 06308500)
n
610
66
145
145
288
Min
60
60
60
252
420
Max
2,480
2,280
2,280
1,500
2,480
Mean
831
918
1,017
620
863
Median
850
968
1,030
617
867
"Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
3 Low flow, average flow, and high flow were determined from paired flow and SC data at the representative station. Low flow is defined as the lowest
25 percent of flows (0-25th percentile); average flow as the middle 50 percent of flows (25th-75th percentile); high flow as the highest 25 percent of flows
(75 -100th percentile).
13
-------
Tongue River
3.1.2 Relationship between Specific Conductance and Discharge
As evidenced in Figure 3-3, SC in the Tongue River increases with decreasing flow. The relationship
between SC and flow is strongest upstream of the Tongue River Reservoir Dam, as exemplified at the
Dayton, Monarch, and Stateline stations in Figure 3-3. Downstream of the Tongue River Reservoir Dam,
the relationship weakens, with the weakest relationship (R2 = 0.3821) occurring at the Miles City gage.
14
-------
Tongue River
Dayton (06298000)
Monarch (06299980)
2,500
2,000
1,500
O 1,000
c/3
500
0
2,500
2,000
§ 1,500
25
O 1,000
10
y = 606.51 xj
R2 = 0.6507
2,000 4,000
Flow (cfs)
Stateline (06306300)
6,000
500
0
y = 3633.6X 03465
R2 = 0.715
o—
O
im> O n
OU <>¦ * ^ U
2,000 4,000
Flow (cfs)
6,000
Birney Day School (06307616)
2,000 4,000
Flow (cfs)
Miles City (06308500)
6,000
2,000 4,000
Flow (cfs)
6,000
2,500
2,000
1,500
O 1,000
tn
-0.2584
y= 1393.2X"
R2 = 0.6189
500
0
2,000 4,000 6,000
Flow (cfs)
Below TRR Dam (06307500)
2,000 4,000
Flow (cfs)
6,000
Brandenberg Bridge (06307830)
2,500
2,000
1,500
-------
Tongue River
3.1.3 Comparison to Applicable Standards
Of the three jurisdictions that border the Tongue River (Wyoming, Montana, and the Northern Cheyenne
Tribe), only Montana has approved numeric water quality standards for salinity. Wyoming's salinity
standards are narrative, and while the Northern Cheyenne Tribe has adopted standards, they have not yet
been approved by USEPA. As a result, this analysis focuses on Montana's salinity standards (described
in Appendix B). The USGS sample stations (highlighted in Table 3-1) have been used to compare
measured data to the salinity standards in the Tongue River.
Since there is no guidance in the Administrative Rules of Montana (ARM), it is assumed that the
"electrical conductivity" standard can be applied to "specific conductance" (SC) data, which is simply
electrical conductivity that has been corrected to a temperature of 25° Celsius. The standards are
seasonal, with separate criteria for the growing season (March 2 - October 31) and non-growing season
(November 1 - March 1) and include monthly average criteria as well as instantaneous maximum criteria.
To facilitate comparison to Montana's standards, the available data have been stratified by the growing
season and non-growing season.
3.1.3.1 Instantaneous Maximum Standard
The instantaneous maximum salinity criteria for the main stem Tongue River are 1,500 (iS/cm for the
growing season and 2,500 (iS/cm for the non-growing season. These criteria have only been exceeded in
the Tongue River at Miles City, only during the growing season, and only once. The single exceedance
occurred during a low flow period in October 2001 at which time an SC of 2,280 (iS/cm was measured in
the river. SC values of 1,500 (iS/cm were observed twice, once in 1979 and once in 1986 during relatively
high flow conditions (78th and 75th flow percentiles - see Figure 3-4).
o Station 06308500 (Miles City) \Nater Quality Standard - Monthly Average VMater Quality Standard - Inst. Max
2,500
2,000
E
%
3
g 1,500
c
TO
U
3
¦o
c
u 1 ,ooo
O
'u
a>
Q.
500
0 ,
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Flow Percentile (%)
Figure 3-4. Specific conductance versus flow percentile (growing season only) for the Tongue River at
Miles City, Montana (USGS Gage 06308500). Entire period of record is shown; continuous data and grab
samples.
16
-------
Tongue River
3.1.3.2 Monthly Average Standards
The monthly average salinity standards for the Tongue River are 1,000 (iS/cm for the growing season and
1,500 (iS/cm for the non-growing season. However, the Administrative Rules of Montana (ARM
17.30.670) do not provide guidance regarding the minimum number of samples needed to calculate
"monthly average" values. In the absence of such guidance, the available data were screened to
determine the quantity of available data on a monthly basis (i.e., 1, 2, 3, >4 data points per month) and
whether or not the available data represent the full range of flow conditions and the current time period.
Since the quantity of available data varies on a station-by-station basis, this screening analysis was
conducted for each of the USGS stations. This analysis is presented in Appendix E and shows that, in
general:
• The period of record varies from a maximum of approximately 47 years at Miles City, Montana
to a minimum of approximately two years above the T&Y Diversion Dam, Montana.
• There is considerably less data during the non-growing season when compared to the growing
season.
• In most cases, with the exception of the last five years when USGS began continuous SC data
collection, there are few months with greater than one sample per month.
• Given the variability in SC on a monthly basis (maximum measured change in one month of 801
(iS/cm at Miles City, July 1963), it is logical to conclude that more samples per month would
better represent the "monthly average" than fewer samples per month.
• Even though there are only > 4 samples per month for a relatively small proportion of the period
of record, those months generally represent the current time period (i.e., the last 5 years) and also
represent the full range of flow conditions (high flows, low flows, average flows).
Therefore, for the purposes of providing a comparison of the available data to the monthly average
criteria, only the last five years have been considered and monthly average SC was only calculated in
cases were at least four monthly samples were available0. The frequency of exceedances for each USGS
station is shown in Table 3-3. Exceedances have only been observed at two locations; the Tongue River
at the Birney Day School Bridge - USGS Gage 06307616, and the Tongue River at Miles City - USGS
Gage 06308500. All of the exceedances occurred during low flow conditions (i.e., < 20th flow percentile)
and during the growing season (Figure 3-5 and Figure 3-6). It should be noted, however, that data are
limited for the non-growing season at all stations except the Tongue River at the Montana-Wyoming State
Line - USGS Gage 06306300 and only one sample has been collected in the Tongue River at Dayton,
Wyoming in the last five years. The ability to reach conclusions during the non-growing season,
therefore, may be restricted by limited data.
c The monthly average salinity standard was exceeded in August 2001, when the monthly average SC reached 1,331 us/cm in the Tongue River at
Montana-Wyoming State Line (USGS Gage 06306300). 31 average daily SC samples are available for August 1 to August 31 from the USGS
continuous SC sampler, and also one grab sample for a total of 32 samples. August 2001 had the second lowest recorded volume of water on record
at the State Line gage (803 acre-feet of water), and all of the average daily flows were in the bottom one percent of the measured average daily flows
on record (flows ranged from 7 to 25 cfs in August 2001).
17
-------
Tongue River
Table 3-3. Average monthly SC data and exceedances of the average monthly water quality standards
for the Tongue River for the last five years assuming > four grab and/or continuous samples per month.1
Station
Season
Numeric
Standard
#
Months
with > 4
Samples
# Months
Exceeding
% Months
Exceeding
Tongue River at Dayton - USGS Gage
06298000
Growing
Season
< 1000
|jS/cm
0
NA
NA
Nongrowing
Season
< 1500
|jS/cm
0
NA
NA
Tongue River at Monarch - USGS Gage
06299980
Growing
Season
< 1000
MS/cm
21
0
0.00%
Nongrowing
Season
< 1500
|jS/cm
0
NA
NA
Tongue River at the Montana-Wyoming State
Line — USGS Gage 06306300
Growing
Season
< 1000
MS/cm
39
0
0.00%
Nongrowing
Season
< 1500
|jS/cm
16
0
0.00%
Tongue River below the Tongue River
Reservoir Dam - USGS Gage 06307500
Growing
Season
< 1000
|jS/cm
21
0
0.00%
Nongrowing
Season
< 1500
|jS/cm
7
0
0.00%
Tongue River at the Birney Day School
Bridge - USGS Gage 06307616
Growing
Season
< 1000
|jS/cm
22
1
4.45%
Nongrowing
Season
< 1500
MS/cm
5
0
0.00%
Tongue River at the Brandenberg Bridge -
USGS Gage 06307830
Growing
Season
< 1000
|jS/cm
37
0
0.00%
Nongrowing
Season
< 1500
|jS/cm
6
0
0.00%
Tongue River above the T&Y Diversion Dam
- USGS Gage 06307990
Growing
Season
< 1000
|jS/cm
15
0
0.00%
Nongrowing
Season
< 1500
|jS/cm
1
0
0.00%
Tongue River at Miles City - USGS Gage
06308500
Growing
Season
< 1000
MS/cm
22
10
45.45%
Nongrowing
Season
< 1500
|jS/cm
0
NA
NA
1 Montana's numeric water quality standards for EC are used as a watershed-wide, common point of reference for purposes of characterizing current water quality
conditions in both Montana and Wyoming. This is not intended to imply that Montana's water quality standards are directly applicable within the jurisdictional
boundaries of Wyoming. Montana's values are used only to provide a single watershed-scale point of reference.
18
-------
Tongue River
~ Birney Day School Bridge Growing Season
WQ Standard - Monthly Avg
1,200
1,000
800
600
400
200
0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Row Percentile (Total Monthly Volume)
Figure 3-5. Average monthly growing season SC values at the Birney Day School Bridge (past five
years with 4 or more samples per month) versus flow percentile.
liles City Growing Season
WQ Standard - Monthly Avg
1,400
1,200
1,000
800
600
400
200
Vo
~ ~
~
~
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Flow Percentile (Total Monthly Volume)
Figure 3-6. Average monthly growing season SC values at Miles City (past five years with 4 or more
samples per month) versus flow percentile.
19
-------
Tongue River
3.1.3.3 Nondegradation
Nondegradation is designed to maintain the existing quality of water when that existing quality is better
than the minimum requirements specified in the water quality standards. Montana's State nondegradation
policy requires that when ambient water quality is below 40 percent of the standard (anti-degradation
trigger), up to a 10 percent change in a harmful parameter (such as SC and SAR) can be allowed without
being considered significant (ARM 17.30.715)d. This is illustrated for SC in the Tongue River mainstem
in Figure 3-7. Increases larger than 10 percent are deemed significant. If deemed significant, an
authorization to degrade would be required from the Montana Department of Environmental Quality.
A monthly comparison of SC to the nondegradation threshold is presented in Figure 3-8 and Figure 3-9.
The nondegradation threshold is exceeded at least some of the time during all months at all of the
evaluated Montana USGS gages from Monarch downstream to Miles City.
1000
900
800
7QG
o 400
LU
300
200
100
0
Nonslgniflcance Threshold (49% of Seasonal Standard)
Antldegradatlon Threshold (40% of Seasonal Standard)
Jm. tab. mroi flpril mm .line July Rug. Sett. Oct Nok Dec.
Figure 3-7. Application of Montana's nondegradation policy to electrical conductivity (EC) in the main
stem Tongue River (MDEQ, 2007).
11 Montana adopted its State nondegradation policy for the parameters of Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) in
March 2006. In June 2006, Montana submitted this change in its regulations to EPA for approval for federal Clean Water Act purposes. EPA has
not yet acted on Montana's submission.
20
-------
Tongue River
125th-75th Percentile
~ Median
E
u
if)
O
V)
3,000
2,500
2,000
1,500
| Min-Max
Average
o
j§ 1,000
500
0
3,000
<2 2,500
o
-------
Tongue River
25th-75th Percentile
~ Median
I Min-Max
Average
3,000
~ 2,500
|
S 2,000
o
500
0
3,000
~ 2,500
E
u
3 2,000
o
-------
Tongue River
3.1.4 Sources of Salinity and Their Influence on the Tongue River
As described above, exceedances of Montana's salinity standards (predominantly the monthly average
criterion) have been observed in the Tongue River. However, it is unclear if the observed exceedances
are due to natural or anthropogenic sources (or a combination of both). Factors that potentially influence
SC levels in the Tongue River include:
• Stock ponds
• Irrigation
o High altitude reservoirs
o High altitude diversions
o Interbasin transfers
o Irrigation withdrawal
o Irrigation return
o Direct discharge
o Discharge to pond
o On-channel
o Off-channel
• Coal mining
• Municipal WWTP
• Tongue River Reservoir and Dam operations
• Soils/geology
All of these factors except for soils and geology are human caused. A modeling analysis was conducted to
estimate the salinity levels that may have occurred in the absence of human influence (see the Modeling
Report; USEPA, 2007). To accomplish this, two model scenarios were developed - the "existing"
condition and "natural" condition (see Appendix J). In the natural scenario, all of the anthropogenic
sources listed above were removed from the model except for the Tongue River Reservoir and high
altitude reservoirs (e.g., Dome Lake, Park Reservoir), which remained but were modeled as though they
were not managed. The existing scenario simulated the anthropogenic sources as they existed as of
September 2006.
As shown in Figure 3-10, simulated salinity in the natural scenario is significantly less than the existing
scenario in the main stem Tongue River at State Line and Miles City. The difference in mean SC was
167.0 (iS/cm and 200.5 (iS/cm at State Line and Miles City, respectively. The mean, median, minimum,
maximum, 25th percentile and 75th percentile values are reported in Appendix J. Model uncertainty is
discussed in Section 7.0 of the Modeling Report.
• Agriculture
o
o
Irrigated
Non-irrigated
• CBM
23
-------
Tongue River
Miles City State Line
~ 25th-75th Percentile ~ Median | Min-Max Average | 25th-75th Percentile ~ Median | Mn-Max Average
E
o
5)
3
0
O
c
n
t>
3
73
C
o
o
o
o
o
a
c/>
1,800
1,600
1,400
1,200
1,000
800
600
400
200
0
E
o
5)
3
0
O
c
n
t>
3
U
C
o
o
o
o
o
a
c/>
1,800
1,600
1,400
1,200
1,000
800
600
400
200
0
Existing Natural Existing Natural
Figure 3-10. Modeled existing versus natural salinity (SC) in the Tongue River at State Line (USGS Gage
06306300) and Miles City (USGS Gage 06308500).
Additional model scenarios were evaluated to assess the relative importance of two of the anthropogenic
sources of salinity - discharge of CBM wastewater and irrigation. These two scenarios were evaluated
because it was hypothesized that they are the most significant sources. Additional modeling and analysis
would be necessary to test this hypothesis and to determine the relative importance of each of the
anthropogenic factors that influence salinity levels in the Tongue River. Details regarding the model
inputs for these scenarios are included in Appendix J.
Mean SC values for the existing condition scenario and the two scenarios where CBM discharge ("No
CBM") and irrigation ("No Irrigation") were removed from the model input files are presented in Table 3-
4). The percent difference between each of these scenarios and the existing condition scenario are also
presented in Table 3-4.
Based on model results, both the discharge of CBM wastewater and irrigation are contributing to elevated
salinity levels in the Tongue River. Given the conservative nature of the components that make up
salinity (Thomann and Mueller, 1987; Wang and Periera, 1987), the effects of CBM carry downstream to
Miles City even though there are no discharges of CBM downstream of the confluence with Hanging
Woman Creek. Irrigation occurs throughout the entire watershed. The estimated contribution from
irrigation ranges from 20 to 21 percent while the contribution from CBM discharge ranges from 4 to 5
percent Table 3-4.
Table 3-4. Simulated mean SC under three modeled scenarios and percent change from the existing
condition scenario.
Location
Existing
No CBM
No Irrigation
|jS/cm
|jS/cm
% A
|jS/cm
% A
Stateline
647
613
-5%
510
-21%
Above T&Y Diversion
728
696
-4%
585
-20%
Miles City
754
725
-4%
595
-21%
24
-------
Tongue River
3.2 Sodium Adsorption Ratio
The sodium adsorption ratio (SAR) is the ratio of sodium to calcium plus magnesium concentrations
expressed as milliequivalents. SAR data for the Tongue River are available from the late 1950's to the
present, and include both grab and continuous samples. Grab samples are available from 54 stations in
the Tongue River in Montana and Wyoming, dating from 1959 to 2006, and collected by multiple
governmental agencies and private organizations. USGS also collected continuous flow and SAR data at
the Tongue River at Monarch, WY (06299980), State Line (06306300), Brandenberg Bridge (06307830),
and Miles City (06308500) between 2004 and the present. The available data are listed in Table 3-5 and
the sample site locations are shown in Figure 3-11. Where summary statistics are provided in the
following sections (i.e., mean, median, maximum, minimum), only SAR grab samples are used so that the
continuous data do not bias the results/
Table 3-5. SAR data for the main stem Tongue River.1
Segment
Station ID
Station Name
Agency
River
Mile
n
Period of
Record
Headwaters to the MT-WY
Border
06298000
Tongue River Near Dayton, WY
USGS
271.3
220
1966-1981;
1999-2002
06299980
Tongue River at Monarch, WY
USGS
246.3
733
1974-1980;
2004-2006
MT-WY Border to the Tongue
River Reservoir
06306300
Tongue River at State Line Near
Decker, MT
USGS
215.4
2,071
1985-1986;
1991-2006
Tongue River Reservoir Dam
to the T&Y Diversion Dam
2075T004
Tongue River just downstream of
the Tongue River Reservoir Dam
MDEQ
201.2
10
1975-1977
06307500
Tongue River at Tongue River
Dam Near Decker, MT
USGS
201.0
236
1975-2006
2277TO01
Tongue River at confluence with
Hanging Woman Creek
MDEQ
179.5
13
1975-1979;
1990
6307610
Tongue River Below Hanging
Woman Creek Near Birney, MT
USGS
164.9
63
1974-1979
06307616
Tongue River at Birney Day
School Bridge Near Birney, MT
USGS
154.3
144
1979-1993;
2004-2006
06307830
Tongue River Below
Brandenberg Bridge Near
Ashland, MT
USGS
88.1
759
1974-1981;
2000-2006
06307990
Tongue River Above T&Y
Diversion Dam Near Miles City,
MT
USGS
28.0
35
2004-2006
T&Y Diversion Dam to the
Mouth
3582TO01
Tongue River downstream of the
T&Y Dam
MDEQ
8.2
20
1973-1980
06308500
Tongue River at Miles City, MT
USGS
2.5
1,034
1959;1962-
2006
Stations with 10 or more samples are included in this table. Entire period of record is shown. Highlighted stations are used in the analyses presented
in the following sections.
f Continuous SAR data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years of
record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
25
-------
Tongue River
> ssmooi
<4 MltTtfft
airier n
ayetine
2277TO#1 r
207STOM
CfOW
MONTANA
WYOMING
MONTANA
Streams
Counties
TribaS Land
| | Tongue River Watershed
« Vfeter Quality Monitoring Stations
JL
r
10 20 40 Miles
_l _J_ L i, j_ 1 J
ohnsori
bounty
Figure 3-11. Tongue River watershed and location of the mainstem Tongue River surface water SAR
monitoring stations (stations with 10 or more sample dates are shown).
26
-------
Tongue River
3.2.1 Spatial Characterization
The USGS sample stations highlighted above in Table 3-5 have been used to provide a general spatial
characterization of SAR in the mainstem Tongue River. As shown in Figure 3-12 and Table 3-6, SAR
increases in a downstream direction (indicating an increasing fraction of sodium in the total salinity load),
from a mean of 0.07 at Dayton, Wyoming, to 0.85 at the Stateline, and 1.55 at Miles City. The largest
increase in mean SAR per river mile occurs between Dayton, Wyoming and Monarch, Wyoming, where
there is an average SAR increase of 0.02 per river mile. The next highest increase in average SAR occurs
between Monarch, Wyoming and the Montana-Wyoming Stateline (0.01 per river mile). Downstream of
the Tongue River Reservoir, the maximum increase in SAR per river mile occurs between the station just
upstream of the T&Y Diversion Dam and Miles City (increase of 0.004 per river mile).
» 75th Percentile —¦—25th Percentile a Median x Average x Max —o— Min
River Mile (miles from the mouth)
Figure 3-12. SAR statistics for USGS stations with 10 or more samples in the main stem Tongue River.
The entire period of record is shown for each station; grab samples only.
27
-------
Tongue River
Table 3-6. SAR statistics for various time periods, flows, and stations on the mainstem Tongue River,
all available grab samples.1
Station
Statistic
Full Period of
Record
Last Five
Years''
Low
Flow'
High
Flow'
Average
Flow'
Tongue River at Dayton, WY
(USGS Gage 06298000)
n
220
1
60
55
105
Min
0.00
0.06
0.03
0.02
0.00
Max
0.31
0.06
0.15
0.14
0.31
Mean
0.07
0.06
0.06
0.07
0.07
Median
0.06
0.06
0.06
0.07
0.06
Tongue River at Monarch, WY
(USGS Gage 06299980)
n
122
43
30
61
31
Min
0.13
0.16
0.27
0.20
0.13
Max
3.72
3.72
3.01
2.98
3.72
Mean
0.65
0.99
0.73
0.64
0.59
Median
0.43
0.37
0.46
0.46
0.30
Tongue River at State Line Near
Decker, MT
(USGS Gage 06306300)
n
134
90
34
34
66
Min
0.21
0.28
0.47
0.21
0.50
Max
2.77
2.73
2.77
2.73
2.64
Mean
0.85
0.94
1.16
0.53
0.86
Median
0.74
0.79
0.96
0.38
0.74
Tongue River at Tongue River Dam
Near Decker, MT
(USGS Gage 06307500)
n
236
51
59
59
118
Min
0.30
0.36
0.70
0.30
0.39
Max
2.44
2.44
1.42
1.14
2.44
Mean
0.81
1.10
0.94
0.55
0.87
Median
0.81
1.04
0.91
0.50
0.81
Tongue River at Birney Day School
Bridge Near Birney, MT
(USGS Gage 06307616)
n
144
51
36
36
72
Min
0.31
0.43
0.66
0.31
0.63
Max
2.03
2.03
2.03
1.18
2.00
Mean
1.00
1.18
1.25
0.61
1.06
Median
0.99
1.18
1.24
0.57
0.99
Tongue River Below Brandenberg
Bridge Near Ashland, MT
(USGS Gage 06307830)
n
165
78
41
41
83
Min
0.48
0.48
0.82
0.48
0.71
Max
2.20
2.13
2.20
1.88
2.13
Mean
1.25
1.32
1.52
0.88
1.29
Median
1.28
1.32
1.52
0.78
1.30
Tongue River Above T&Y Diversion
Dam Near Miles City, MT
(USGS Gage 06307990)
n
35
35
9
9
17
Min
0.49
0.49
1.76
0.54
0.49
Max
2.13
2.13
2.13
1.42
1.80
Mean
1.38
1.38
1.88
0.88
1.38
Median
1.46
1.46
1.83
0.81
1.46
Tongue River at Miles City, MT
(USGS Gage 06308500)
n
466
54
117
117
232
Min
0.37
0.37
1.00
0.45
0.37
Max
3.93
3.74
3.74
3.70
3.93
Mean
1.55
1.80
1.98
1.20
1.51
Median
1.48
1.55
2.00
1.00
1.48
"Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
3 Low flow, average flow, and high flow were determined from paired flow and SAR data at the representative station. Low flow is defined as the lowest
25 percent of flows (0-25th percentile); average flow as the middle 50 percent of flows (25th-75th percentile); high flow as the highest 25 percent of flows
(75 -100th percentile).
28
-------
Tongue River
3.2.2 Relationship between SAR and Discharge
As evidenced by Figure 3-13, SAR tends to increase with decreasing flow. The relationship between
SAR and flow is strongest at the Stateline gage (R2 of 0.8044). However, the relationship grows weaker
towards the Bighorn Mountains, where there is almost no relationship between SAR and flow (Dayton
gage R2 of 0.0016). Downstream of the Tongue River Reservoir Dam, the relationship between the two
parameters is fairly constant, with R2 values between 0.4002 and 0.5738.
29
-------
Tongue River
Dayton (06298000)
Monarch (06299980)
n ni—7-7 U.U 10
y = 0.0577x
R2 = 0.0016
2,000 4,000 6,000
Flow (cfs)
Stateline (06306300)
y = 5.2332x"°387
R2 = 0.8044
~
0 2,000 4,000
Flow (cfs)
6,000
Birney Day School (06307616)
0 2,000 4,000 6,000
Flow (cfs)
Miles City (06308500)
.4_4J61_3x"r_
R2 = 0.4002
oo0o
2,000 4,000
Flow (cfs)
6,000
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
4 4 -0.2263
_ _y_=4U492x
R2 = 0.2426
0
Br o o
•*$&><£ 66 V~b
2,000 4,000 6,000
Flow (cfs)
Below TRR Dam (06307500)
y = 2.7893x"°24'
R2 = 0.4448
2,000 4,000
Flow (cfs)
6,000
Brandenberg Bridge (06307830)
4.0
4.0
3.5
y = 4.5915x"° 2978
3.5
R2 = 0.5738
3.0
3.0
2.5
2.5
a:
2.0
< 2.0
tn
1.5
1.5
1.0
K° °
1.0
^ o
0.5
TP. - ** 1 i U
WOO 0 ^
0.5
0.0
0.0
|- AAA i -0.271
y = 5.2324x
R2 = 0.5496
>
MF> o
Wtet ® o°
o
- 0 »
2,000 4,000
Flow (cfs)
6,000
Figure 3-13. Relationship between flow and SAR
River. Entire period of record
at selected USGS stations on the main stem Tongue
is shown; grab samples only.
30
-------
Tongue River
3.2.3 Comparison to Applicable Standards
Of the three jurisdictions that border the Tongue River (Wyoming, Montana, and the Northern Cheyenne
Tribe), only Montana has approved numeric water quality standards for SAR. Wyoming's SAR standards
are narrative, and while the Northern Cheyenne Tribe has adopted standards, they have not yet been
approved by USEPA. As a result, this analysis focuses on Montana's SAR standards (described in
Appendix B). The standards are seasonal, with separate criteria for the growing season (March 2 -
October 31) and non-growing season (November 1 - March 1) and include monthly average criteria as
well as instantaneous maximum criteria.
3.2.3.1 Instantaneous Maximum SAR Standards
The instantaneous maximum SAR criteria for the mainstem Tongue River are 4.5 for the growing season
and 7.5 for the non-growing season. None of the available SAR data for the mainstem Tongue River has
ever exceeded these criteria.
3.2.3.2 Monthly Average SAR Standards
The monthly average SAR standards for the Tongue River are 3.0 for the growing season and 5.0 for the
non-growing season. However, as with salinity, the Administrative Rules of Montana (ARM 17.30.670)
do not provide guidance regarding the minimum number of samples needed to calculate "monthly
average" values. In the absence of such guidance, the available data were screened to determine the
quantity of available data on a monthly basis (i.e., 1, 2, 3, >4 data points per month) and whether or not
the available data represent the full range of flow conditions and the current time period. Since the
quantity of available data varies on a station-by-station basis, this screening analysis was conducted for
each of the mainstem USGS stations with 10 or more samples. This analysis is presented in Appendix F
and shows that, in general:
• The period of record varies from a maximum of approximately 47 years at Miles City, Montana
to a minimum of approximately two years above the T&Y Diversion Dam, Montana.
• There is considerably less data during the non-growing season when compared to the growing
season.
• In most cases, with the exception of the last five years when USGS began continuous SAR data
collection, there are few months with greater than one sample per month.
• Given the variability in SAR on a monthly basis (maximum measured change in one month of
3.54 at Monarch, Wyoming, June 2006), it is logical to conclude that more samples per month
would better represent the "monthly average" than fewer samples per month.
• Even though there are only > 4 samples per month for a relatively small proportion of the period
of record, those months generally represent the current time period (i.e., the last 5 years) and also
represent the full range of flow conditions (high flows, low flows, average flows).
Therefore, for the purposes of providing a comparison of the available data to the monthly average SAR
criteria, only the last five years have been considered and monthly average SAR was only calculated in
cases where at least four monthly samples were available. The frequency of exceedances for each USGS
station is shown in Table 3-7. In the past 5 years, no exceedances of the average monthly criteria have
been observed. It should be noted, however, that data are limited for the non-growing season at all
stations except the Tongue River at the Montana-Wyoming State Line - USGS Gage 06306300. The
ability to reach conclusions during the non-growing season, therefore, may restricted by limited data.
31
-------
Tongue River
Table 3-7. Average monthly SAR data and exceedances of the average monthly water quality
standards for the Tongue River for the last five years assuming > four samples per month.1
Station
Season
Numeric
Standard
#
Months
with > 4
Samples
# Months
Exceeding
% Months
Exceeding
Tongue River at Dayton - USGS Gage
06298000
Growing
Season
< 3
0
NA
NA
Nongrowing
Season
< 5
0
NA
NA
Tongue River at Monarch - USGS Gage
06299980
Growing
Season
< 3
21
0
0.00%
Nongrowing
Season
< 5
0
NA
NA
Tongue River at the Montana-Wyoming State
Line — USGS Gage 06306300
Growing
Season
< 3
39
0
0.00%
Nongrowing
Season
< 5
16
0
0.00%
Tongue River below the Tongue River
Reservoir Dam - USGS Gage 06307500
Growing
Season
< 3
5
0
0.00%
Nongrowing
Season
< 5
0
NA
NA
Tongue River at the Birney Day School Bridge
-USGS Gage 06307616
Growing
Season
< 3
5
0
0.00%
Nongrowing
Season
< 5
0
NA
NA
Tongue River at the Brandenberg Bridge -
USGS Gage 06307830
Growing
Season
< 3
23
0
0.00%
Nongrowing
Season
< 5
1
0
0.00%
Tongue River above the T&Y Diversion Dam -
USGS Gage 06307990
Growing
Season
< 3
5
0
0.00%
Nongrowing
Season
< 5
0
NA
NA
Tongue River at Miles City - USGS Gage
06308500
Growing
Season
< 3
22
0
0.00%
Nongrowing
Season
< 5
0
NA
NA
1 Montana's numeric water quality standards for SAR are used as a watershed-wide, common point of reference for purposes of characterizing current water quality
conditions in both Montana and Wyoming. This is not intended to imply that Montana's water quality standards are directly applicable within the jurisdictional
boundaries of Wyoming. Montana's values are used only to provide a single watershed-scale point of reference.
32
-------
Tongue River
3.2.3.3 Nondegradation
Montana's State nondegradation policy requires that when ambient water quality is below 40 percent of
the standard (anti-degradation trigger), up to a 10 percent change in a harmful parameter (such as SC and
SAR) can be allowed without being considered significant (ARM 17.30.715)8. This is illustrated for SC in
Figure 3-7 in Section 3.1.3.3. If deemed significant, an authorization to degrade would be required from
the Montana Department of Environmental Quality.
A monthly comparison of SAR to the nondegradation threshold is presented in Figure 3-14 and Figure 3-
15. The nondegradation threshold is rarely exceeded during the nongrowing season. Some exceedances
have been observed at all of the evaluated stations except Dayton, Wyoming during the growing season.
The greatest frequency of exceedance occurs at Miles City, where it is exceeded approximately 50 percent
of the time during the growing season.
8 Montana adopted its State nondegradation policy for the parameters of Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) in
March 2006. In June 2006, Montana submitted this change in its regulations to EPA for approval for federal Clean Water Act purposes. EPA has
not yet acted on Montana's submission.
33
-------
Tongue River
25th-75th Ftercentile
~ Median
| Min-Max
Average
Feb Mar Apr
25th-75th Ffercentile
May Jun
~ Median
Aug Sep
| Min-Max
Nov Dec
Average
Jan Feb Mar Apr May Jun J
~ 25th-75th Ftercentile ~ Median
j| Aug Sep Oct Nov Dec
1 Min-Max Average
i ill
4-
*
-frj-
HH
1
1 1 i
1
1
- L 1 1
1
__
i
. _ 1 _ .
i
...j
¦ 4-
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Figure 3-14. SAR data and nondegradation thresholds for the Tongue River downstream of the Tongue
River Reservoir Dam. Entire period of record is shown; grab samples only.
34
-------
Tongue River
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
Q 25th-75th Ftercentile
~ Median
| Mi n- Max
Average
Jan Feb Mar Apr
D 25th-75th Ftercentile
May Jun Jul Aug Sep Oct Nov Dec
~ Median | Min-Max Average
Jan Feb Mar Apr May Jun
I 25th-75th Ftercentile ~ Median
Aug Sep Oct Nov Dec
| Min-Max Average
Figure 3-15. SAR data and nondegradation thresholds for the Tongue River upstream of the Tongue
River Reservoir Dam. Entire period of record is shown; grab samples only.h
h Montana's numeric water quality standards for SAR are used as a watershed-wide, common point of reference for purposes of characterizing
current water quality conditions in both Montana and Wyoming. This is not intended to imply that Montana's water quality standards are directly
applicable within the jurisdictional boundaries of Wyoming. Montana's values are used only to provide a single watershed-scale point of
reference.
35
-------
Tongue River
3.2.4 Sources of SAR and Their Influence on the Tongue River
Since there have been no observed exceedances of the instantaneous maximum or average monthly SAR
standards in the main stem Tongue River, no source analysis has been conducted.
3.3 Metals
Aquatic life and fishery beneficial uses in the Tongue River (confluence with Hanging Woman Creek to
the mouth) were listed as impaired because of metals on the Montana 1996 303(d) list (Segments
MT42C001_012 and MT42C001_011). No specific metals were listed as the cause of impairment, but
the metals listing on the 1996 list applies to one or more of the following parameters - arsenic, cadmium,
chromium, copper, iron, lead, nickel, selenium, silver, and zinc (Personal communications, Montana
DEQ, 2002). Metals were not listed as a cause of impairment on the 2006 303(d) list.
As described in Appendix B, metals data for the following analysis consist only of USGS, USEPA, and
Montana DEQ data collected between January 1, 1997 and the present. Data were compared to the
Montana total recoverable metals standards, but both "total" and "total recoverable" data were used in the
assessment. Where no hardness data were available, the average values shown in Table 3-8 were used to
calculate hardness dependent criteria.
Table 3-8. Summary of hardness data in the Tone
ue River.
Station Name
Station
Number
Count
Average
(mg/L)
Minimum
(mg/L)
Maximum
(mg/L)
Tongue River near the State Line
06306300
151
264
81
417
Tongue River below the Tongue River
Reservoir Dam
06307500
253
280
86
450
Tongue River at the Birney Day School
Bridge
06307616
161
282
110
450
Tongue River near the Brandenberg
Bridge
06307830
181
308
140
490
Tongue River at Miles City
06308500
483
322
56
590
Metals data were analyzed for the entire Tongue River in Montana. The river was divided into three
segments for the analysis - Wyoming border to the Tongue River Reservoir (Segment MT42B001_010);
Tongue River Reservoir Dam to the T&Y Diversion Dam (Segments MT42B001 020 and
MT42C001_012); and T&Y Diversion Dam to the Mouth (Segment MT42C001_011). These segments
correspond to the 1996 303(d) listed segments. The two 303(d) segments between the Tongue River
Reservoir Dam and the T&Y Diversion Dam were combined for the purpose of this analysis. The
following sections summarize the metals data for each segment of the Tongue River.
36
-------
Tongue River
3.3.1 State Line to the Tongue River Reservoir
Table 3-9 presents a summary of the available metals data obtained in the Tongue River between the
Montana-Wyoming border and the Tongue River Reservoir. In general, 53 samples were obtained for
each parameter. Data were available between May 15, 2001 and May 15, 2006, and all of the samples
were obtained at USGS gage 06306300 (Tongue River at the Stateline).
Table 3-9. Summary of metals data in the Tongue River between the MT-WY border and the Tongue
River Reservoir.
Parameter
Count
Average
(M9/L)
Min
(M9/L)
Max
(M9/L)
Period of Record
Arsenic (Total) (pg/L as As)
53
1.13
0.44
3.00
5/15/01-5/15/06
Cadmium (Total) (pg/L as Cd)
53
0.03
0.02
0.35
5/15/01-5/15/06
Chromium (Total) (pg/L as Cr)
53
0.99
0.40
7.00
5/15/01-5/15/06
Copper (Total) (pg/L as Cu)
53
2.47
0.80
15.20
5/15/01-5/15/06
Iron, (Total), (pg/L as Fe)
54
590
66
7,530
5/15/01-5/15/06
Lead (Total) (pg/L as Pb)
53
0.68
0.04
10.80
5/15/01-5/15/06
Nickel (Total) (pg/L as Ni)
53
2.93
0.75
12.10
5/15/01-5/15/06
Selenium (Total) (pg/L as Se)
53
0.47
0.20
1.60
5/15/01-5/15/06
Zinc (Total) (pg/L as Zn)
53
5.53
1.00
44.00
5/15/01-5/15/06
Seven iron samples (13 percent) exceeded the chronic criterion of 1,000 \xgfL. The date of the
exceedances, the concentrations, and the percent increase from the standard are presented in Table 3-10.
At most, iron samples were obtained once per month, and therefore the exceedances of the chronic
criterion were based on single samples rather than an average of several values. No other metals samples
exceeded the metals standards in this segment.
Table 3-10. Summary of the iron exceedances in the Tongue River between the MT-WY border and the
Tongue River Reservoir.
Station
Date of the Exceedance
Chronic
Standard
Value
% Increase from the Standard
06306300
5/15/2001
1,000 |jg/L
1,680 |jg/L
68%
06306300
6/19/2001
1,000 |jg/L
1,090 |jg/L
9%
06306300
6/5/2002
1,000 |jg/L
1,020 |jg/L
2%
06306300
7/10/2002
1,000 |jg/L
1,090 |jg/L
9%
06306300
5/6/2003
1,000 |jg/L
1,120 |jg/L
12%
06306300
6/4/2003
1,000 |jg/L
1,050 |jg/L
5%
06306300
5/12/2005
1,000 |jg/L
7,530 |jg/L
653%
37
-------
Tongue River
3.3.2 Tongue River Reservoir Dam to the T&Y Diversion Dam
Metals data were available at eight stations between the Tongue River Reservoir Dam and the T&Y
Diversion Dam (Table 3-11). The frequency, number, and type of samples obtained at each station varied
at each station. The number of samples per parameter varied between 6 and 89. Data were available
between March 27, 2002 and May 16, 2006. Table 3-12 presents a summary of the available metals data
for this segment.
Table 3-11. Stations with metals data - Tongue River Reservoir Dam to the T&Y Diversion Dam.
Station Name
Station ID
Agency
RM Miles
Tongue River at Tongue River Reservoir Dam near Decker MT
06307500
USGS
201.0
Tongue River below Hanging Woman Creek near Birney, MT
Y16TNGR01
MDEQ
164.9
Tongue River at Birney Day School Bridge near Birney MT
06307616
USGS
154.3
Tongue River near Birney at the Birney Day School, MT
Y16TNGR02
MDEQ
153.9
Tongue River below Brandenberg Bridge near Ashland MT
06307830
USGS
88.1
Tongue River near Brandenberg
Y16TONGR01
MDEQ
87.4
Tongue River above T&Y Diversion Dam near Miles City, MT
06307990
USGS
28.0
Tongue River at the T&Y Dam
Y16TR80
MDEQ
21.1
Table 3-12. Summary of metals data in the Tongue River between the Tongue River Reservoir Dam and
the T&Y Diversion Dam.
Parameter
Count
Average
(M9/L)
Min
(M9/L)
Max
(M9/L)
Period of Record
Arsenic (Total) (pg/L as As)
74
1.28
0.80
5.00
3/27/02-5/16/06
Cadmium (Total) (pg/L as Cd)
81
0.04
0.02
0.22
4/26/03-5/16/06
Chromium (Total) (pg/L as Cr)
73
2.05
0.50
10.00
3/27/02-5/16/06
Copper (Total) (pg/L as Cu)
85
3.13
0.38
15.90
3/27/02-5/16/06
Iron, (Total), (pg/L as Fe)
89
731
22
8,480
3/27/02-5/16/06
Lead (Total) (pg/L as Pb)
82
0.81
0.03
9.33
3/27/02-5/16/06
Nickel (Total) (pg/L as Ni)
80
3.39
0.01
13.40
3/27/02-5/16/06
Selenium (Total) (pg/L as Se)
80
0.53
0.20
2.00
4/26/03-5/16/06
Silver (Total) (pg/L as Ag)
6
0.43
0.25
1.50
4/26/03-10/02/03
Zinc (Total) (pg/L as Zn)
84
4.20
0.01
34.00
4/18/02-5/16/06
38
-------
Tongue River
Fourteen iron samples (16 percent) exceeded the chronic criterion of 1,000 (ig/L. The date of the
exceedance, the concentration, and the percent increase from the standard are presented in Table 3-13. At
most, iron samples were obtained once per month, and therefore the exceedances of the chronic criterion
were based on single samples rather than an average of several values. No other metals samples exceeded
the metals standards in this segment.
Table 3-13. Summary of the iron exceedances in the Tongue River between the Tongue River Reservoir
Dam and the T&Y Diversion Dam.
Station
Date of the
Exceedance
Standard
Value
% Increase from the
Standard
Y16TR80
3/27/2002
1,000 |jg/L
4,860 |jg/L
386%
Y16TNGR01
4/26/2003
1,000 |jg/L
1,180 |jg/L
18%
Y16TONGR01
6/21/2004
1,000 |jg/L
1,010 |jg/L
1%
6307616
8/23/2004
1,000 |jg/L
4,300 |jg/L
330%
6307830
8/23/2004
1,000 |jg/L
1,000 |jg/L
0%
6307830
5/16/2005
1,000 |jg/L
6,880 |jg/L
588%
6307616
5/16/2005
1,000 |jg/L
1,300 |jg/L
30%
6307990
5/18/2005
1,000 |jg/L
8,480 |jg/L
748%
6307990
6/7/2005
1,000 |jg/L
2,760 |jg/L
176%
6307990
6/21/2005
1,000 |jg/L
5,310 |jg/L
431%
Y16TONGR01
7/13/2005
1,000 |jg/L
1,170 |jg/L
17%
6307990
10/4/2005
1,000 |jg/L
5,290 |jg/L
429%
6307990
3/6/2006
1,000 |jg/L
1,070 |jg/L
7%
6307990
4/5/2006
1,000 |jg/L
2,820 |jg/L
182%
39
-------
Tongue River
3.3.3 T&Y Diversion Dam to the Mouth
Table 3-14 presents a summary of the available metals data obtained in the Tongue River between the
T&Y Diversion Dam and the mouth. In general, 22 to 34 samples were obtained for each parameter.
Data were available between June 15, 1999 and May 17, 2006, and all of the samples were obtained at
USGS gage 06308500 (Tongue River at Miles City).
Table 3-14. Summary of metals data in the Tongue River between the T&Y Diversion Dam and the
mouth.
Parameter
Count
Average
(M9/L)
Min
(M9/L)
Max
(M9/L)
Period of Record
Arsenic (Total) (pg/L as As)
33
2.45
0 69
8.00
6/15/99-5/17/06
Cadmium (Total) (pg/L as Cd)
32
0.24
0.02
1.85
6/15/99-5/17/06
Chromium (Total) (pg/L as Cr)
30
8.46
0.40
51.00
6/15/99-5/17/06
Copper (Total) (pg/L as Cu)
33
15.42
1.60
120.00
6/15/99-5/17/06
Iron, (Total), (pg/L as Fe)
24
8,125
86
46,900
4/18/02-5/17/06
Lead (Total) (pg/L as Pb)
32
10.53
0.06
90.20
6/15/99-5/17/06
Nickel (Total) (pg/L as Ni)
32
16.44
1.30
123.00
6/15/99-5/17/06
Selenium (Total) (pg/L as Se)
22
0.73
0.24
2.50
2/04/04-5/17/06
Zinc (Total) (pg/L as Zn)
32
39.38
1.00
337.00
6/15/99-5/17/06
Cadmium, copper, iron, lead, nickel, and zinc concentrations exceeded the metals standards in the Tongue
River between the T&Y Diversion Dam and the mouth. No other metals exceeded standards. The
following sections summarize the individual exceedances.
3.3.3.1 Iron
Ten iron samples (42 percent) exceeded the chronic criterion of 1,000 (ig/L. The date of the exceedance,
the concentration, and the percent increase from the standard are presented in Table 3-15. At most, iron
samples were obtained once per month, and therefore the exceedances of the chronic criterion were based
on single samples rather than an average of several values.
Table 3-15. Summary of the iron exceedances in the Tongue River between the T&Y Diversion Dam and
the Mouth.
Station
Date of the
Exceedance
Standard
Value
% Increase from the
Standard
6308500
March 11, 2004
1,000 |jg/L
_l
=L
O
h-
h-
c\T
177%
6308500
May 25, 2004
1,000 |jg/L
46,900 |jg/L
4590%
6308500
June 23, 2004
1,000 |jg/L
1,080 |jg/L
8%
6308500
October 13, 2004
1,000 |jg/L
1,010 |jg/L
1%
6308500
May 17, 2005
1,000 |jg/L
12,500 |jg/L
1150%
6308500
June 9, 2005
1,000 |jg/L
42,400 |jg/L
4140%
6308500
August 23, 2005
1,000 |jg/L
18,600 |jg/L
1760%
6308500
October 5, 2005
1,000 |jg/L
35,200 |jg/L
3420%
6308500
March 6, 2006
1,000 |jg/L
2,590 |jg/L
159%
6308500
April 5, 2006
1,000 |jg/L
25,600 |jg/L
2460%
40
-------
Tongue River
3.3.3.2 Copper
Seven copper samples (21 percent) exceeded the chronic copper criterion. The date of the exceedances,
the concentrations, and the percent increase from the standard are presented in Table 3-16. At most,
copper samples were obtained once per month, and therefore the exceedances of the chronic criterion
were based on single samples rather than an average of several values. Six of the seven copper samples
also exceeded the acute criterion.
Table 3-16. Summary of the copper exceedances in the Tongue River between the T&Y Diversion Dam
and the Mouth.
Station
Date of the
Exceedance
Standard1
Value
% Increase from the
Standard
06308500
June 5, 2001
Acute: 30.5 |jg/L
Chronic: 18.9 |jg/L
Human Health: 1,300 |jg/L
32.6 |jg/L
Acute: 7%
Chronic: 72%
Human Health: NA
06308500
May 25, 2004
Acute: 22.5 |jg/L
Chronic: 14.4 |jg/L
Human Health: 1,300 |jg/L
79.3 |jg/L
Acute: 252%
Chronic: 451%
Human Health: NA
06308500
May 17, 2005
Acute: 33.7 |jg/L
Chronic: 22.9 |jg/L
Human Health: 1,300 |jg/L
23.6 |jg/L
Acute: NA
Chronic: 3%
Human Health: NA
06308500
June 9, 2005
Acute: 8.2 |jg/L
Chronic: 5.8 |jg/L
Human Health: 1,300 |jg/L
120.0 |jg/L
Acute: 1,356%
Chronic: 1,979%
Human Health: NA
06308500
August 23, 2005
Acute: 22.5 |jg/L
Chronic: 14.3 |jg/L
Human Health: 1,300 |jg/L
30.8 |jg/L
Acute: 37%
Chronic: 115%
Human Health: NA
06308500
October 5, 2005
Acute: 42.1 |jg/L
Chronic: 25.3 |jg/L
Human Health: 1,300 |jg/L
69.5 |jg/L
Acute: 65%
Chronic: 174%
Human Health: NA
06308500
April 5, 2006
Acute: 42.1 |jg/L
Chronic: 25.3 |jg/L
Human Health: 1,300 |jg/L
44.7 |jg/L
Acute: 6%
Chronic: 76%
Human Health: NA
Acute and chronic criteria are hardness dependant. See Appendix C for the methodology for calculating the criteria.
41
-------
Tongue River
3.3.3.3 Lead
Eight lead samples (25 percent) exceeded the chronic lead criterion. The date of the exceedances, the
concentrations, and the percent increase from the standard are presented in Table 3-17. At most, lead
samples were obtained once per month, and therefore the exceedances of the chronic criterion were based
on single samples rather than an average of several values. One of the eight lead samples also exceeded
the acute criterion, and six of the samples exceeded the human health criterion of 15 (ig/L.
Table 3-17. Summary of the lead exceedances in the Tongue River between the T&Y Diversion Dam and
the Mouth.
Station
Date of the
Exceedance
Standard1
Value
% Increase from the
Standard
06308500
June 15, 1999
Acute: 109.2 |jg/L
Chronic: 4.3 |jg/L
Human Health: 15 |jg/L
8.1 |jg/L
Acute: NA
Chronic: 90%
Human Health: NA
06308500
June 5, 2001
Acute: 233.9 |jg/L
Chronic: 9.1 |jg/L
Human Health: 15 |jg/L
29.4 |jg/L
Acute: NA
Chronic: 223%
Human Health: 96%
06308500
May 25, 2004
Acute: 155.2 |jg/L
Chronic: 6.0 |jg/L
Human Health: 15 |jg/L
79.8 |jg/L
Acute: NA
Chronic: 1,220%
Human Health: 432%
06308500
May 17, 2005
Acute: 311.6 |jg/L
Chronic: 12.1 |jg/L
Human Health: 15 |jg/L
15.0 |jg/L
Acute: NA
Chronic: 24%
Human Health: NA
06308500
June 9, 2005
Acute: 39.9 |jg/L
Chronic: 1.6 |jg/L
Human Health: 15 |jg/L
90.2 |jg/L
Acute: 126%
Chronic: 5,699%
Human Health: 501%
06308500
August 23, 2005
Acute: 154.9 |jg/L
Chronic: 6.0 |jg/L
Human Health: 15 |jg/L
23.2 |jg/L
Acute: NA
Chronic: 284%
Human Health: 55%
06308500
October 5, 2005
Acute: 361.8 |jg/L
Chronic: 14.1 |jg/L
Human Health: 15 |jg/L
41.7 |jg/L
Acute: NA
Chronic: 196%
Human Health: 178%
06308500
April 5, 2006
Acute: 361.8 |jg/L
Chronic: 14.1 |jg/L
Human Health: 15 |jg/L
38.4 |jg/L
Acute: NA
Chronic: 172%
Human Health: 156%
Acute and chronic criteria are hardness dependant. See Appendix C for the methodology for calculating the criteria.
42
-------
Tongue River
3.3.3.4 Cadmium
Five cadmium samples (16 percent) exceeded the chronic cadmium criterion. The date of the
exceedances, the concentrations, and the percent increase from the standard are presented in Table 3-18.
At most, cadmium samples were obtained once per month, and therefore the exceedances of the chronic
criterion were based on single samples rather than an average of several values. One of the five cadmium
samples also exceeded the acute criterion.
Table 3-18. Summary of the cadmium exceedances in the Tongue River between the T&Y Diversion Dam
and the Mouth.
Station
Date of the
Exceedance
Standard1
Value
% Increase from the
Standard
06308500
June 15, 1999
Acute: 2.69 |jg/L
Chronic: 0.32 |jg/L
Human Health: 5 |jg/L
0.50 |jg/L
Acute: NA
Chronic: 56%
Human Health: NA
06308500
May 25, 2004
Acute: 3.56 |jg/L
Chronic: 0.39 |jg/L
Human Health: 5 |jg/L
1.21 pg/L
Acute: NA
Chronic: 208%
Human Health: NA
06308500
June 9, 2005
Acute: 1.20 |jg/L
Chronic: 0.18 |jg/L
Human Health: 5 |jg/L
1.85 |jg/L
Acute: 54%
Chronic: 937%
Human Health: NA
06308500
August 23, 2005
Acute: 3.56 |jg/L
Chronic: 0.39 |jg/L
Human Health: 5 |jg/L
0.42 |jg/L
Acute: NA
Chronic: 7%
Human Health: NA
06308500
October 5, 2005
Acute: 7.00 |jg/L
Chronic: 0.64 |jg/L
Human Health: 5 |jg/L
0.84 |jg/L
Acute: NA
Chronic: 31%
Human Health: NA
Acute and chronic criteria are hardness dependant. See Appendix C for the methodology for calculating the criteria.
3.3.3.5 Zinc
Two zinc samples (6 percent) exceeded the chronic zinc criterion. The date of the exceedances, the
concentrations, and the percent increase from the standard are presented in Table 3-19. At most, zinc
samples were obtained once per month, and therefore the exceedances of the chronic criterion were based
on single samples rather than an average of several values. Both of the zinc samples also exceeded the
acute criterion.
Table 3-19. Summary of the zinc exceedances in the Tongue River between the T&Y Diversion Dam and
the Mouth.
Station
Date of the
Exceedance
Standard1
Value
% Increase from the
Standard
06308500
May 25, 2004
Acute: 184 |jg/L
Chronic: 184 |jg/L
Human Health: 2,000 |jg/L
247 |jg/L
Acute: 34%
Chronic: 34%
Human Health: NA
06308500
June 9, 2005
Acute: 74 |jg/L
Chronic: 74 |jg/L
Human Health: 2,000 |jg/L
337 |jg/L
Acute: 352%
Chronic: 352%
Human Health: NA
Acute and chronic criteria are hardness dependant. See Appendix C for the methodology for calculating the criteria.
43
-------
Tongue River
3.3.3.6 Nickel
Two nickel samples (6 percent) exceeded the chronic nickel criterion. The date of the exceedances, the
concentrations, and the percent increase from the standard are presented in Table 3-20. At most, nickel
samples were obtained once per month, and therefore the exceedances of the chronic criterion were based
on single samples rather than an average of several values. One of the nickel samples also exceeded the
human health criterion.
Table 3-20. Summary of the zinc exceedances in the Tongue River between the T&Y Diversion Dam and
the Mouth.
Station
Date of the
Exceedance
Standard1
Value
% Increase from the
Standard
06308500
May 25, 2004
Acute: 719 |jg/L
Chronic: 80 |jg/L
Human Health: 100 |jg/L
85 |jg/L
Acute: NA
Chronic: 6%
Human Health: NA
06308500
June 9, 2005
Acute: 292 |jg/L
Chronic: 32 |jg/L
Human Health: 100 |jg/L
123 |jg/L
Acute: NA
Chronic: 279%
Human Health: 23%
Acute and chronic criteria are hardness dependant. See Appendix C for the methodology for calculating the criteria.
3.3.4 Metals and Sediment
The Tongue River has a naturally high sediment load (see Section 3.4). Metals are bound to sediment in
varying degrees, depending on the local geology and sources. Both total recoverable and total metals
laboratory analyses measure the sediment-bound metals in the sample, in addition to the dissolved water
column metals. Therefore, when a water sample has more sediment, it is likely that the total or total
recoverable metals sample will have higher metals concentrations. This phenomenon is demonstrated in
Figure 3-16 below, which shows that total cadmium, copper, iron, lead, nickel, and zinc concentrations
are all highly correlated with suspended solids at USGS station 06308500 (Tongue River at Miles City).
These data indicate that the Tongue River may naturally exceed the various metals standards at times due
to high sediment loads.
To support this theory, dissolved metals concentrations were analyzed to determine if the majority of the
metals concentrations were in the dissolved or suspended form when standards were exceeded. Table 3-
21 shows that the paired dissolved and total metals data collected in the Tongue River at Miles City
mostly consisted of suspended metals, with very little dissolved concentrations. This is significant
because it is primarily the dissolved form that causes aquatic toxicity, and USEPA has recommended that
criteria for metals be re-expressed as dissolved concentrations (USEPA, 1996).
44
-------
Tongue River
O)
=3
E
d
E
"O
03
o
"ro
-I—1
o
2.5
2.0
1.5
1.0
0.5
0.0
y = 0.0002X + 0.0496
R2 = 0.9488
10 100 1,000 10,000
TSS (mg/L)
70,000
60,000
50,000
40,000
30,000
20,000
10,000
0
160
140
120
100
80
60
40
20
0
y = 6.9243X + 1955.5
R2 = 0.8397
©ocaxxx&P
10 100 1,000 10,000
TSS (mg/L)
y = 0.0166x +3.3293
R2 = 0.9605
10 100 1,000
TSS (mg/L)
10,000
0
CL
CL
O
O
"ro
-t—'
o
73
ro
-------
Tongue River
Table 3-21. Paired total and dissolved metals concentrations in the Tongue River at Miles City, Montana.
Station
Parameter
Date
Total
Concentration
Dissolved
Concentration
% Suspended
% Dissolved
6308500
Copper
5/5/04
79.3 |jg/L
3.2 pg/L
96.1 %
3.9%
6308500
Copper
6/9/05
120 |jg/L
4.6 |jg/L
96.3%
3.7%
6308500
Copper
8/23/05
30.8 |jg/L
5 pg/L
86.0%
14.0%
6308500
Copper
10/5/05
69.5 |jg/L
3.1 pg/L
95.7%
4.3%
6308500
Copper
4/5/06
44.7 |jg/L
5.1 pg/L
89.7%
10.3%
6308500
Cadmium
5/25/04
1.21 |jg/L
0.02 pg/L
98.4%
1.6%
6308500
Cadmium
6/9/05
1.85 |jg/L
0.02 pg/L
98.9%
1.1%
6308500
Cadmium
10/5/05
0.84 |jg/L
0.02 pg/L
97.7%
2.3%
6308500
Zinc
6/9/05
337 |jg/L
6 pg/L
98.2%
1.8%
6308500
Lead
5/25/04
79.8 |jg/L
0.10 pg/L
99.8%
0.2%
6308500
Lead
5/17/05
15 pg/L
0.04 pg/L
99.8%
0.2%
6308500
Lead
6/9/05
90.2 |jg/L
0.23 pg/L
99.8%
0.2%
6308500
Lead
8/23/05
23.2 |jg/L
0.14 pg/L
99.4%
0.6%
6308500
Lead
10/5/05
41.7 |jg/L
0.04 pg/L
100%
0%
6308500
Lead
4/5/06
38.4 |jg/L
0.04 pg/L
99.9%
0.1%
6308500
Iron
3/11/04
2,770 |jg/L
3 pg/L
99.9%
0.1%
6308500
Iron
5/25/04
46,900 |jg/L
6 pg/L
100%
0%
6308500
Iron
6/23/04
1,080 |jg/L
3 pg/L
99.8%
0.2%
6308500
Iron
10/13/04
1,010 |jg/L
3 pg/L
99.7%
0.3%
6308500
Iron
5/17/05
12,500 |jg/L
3 pg/L
100%
0%
6308500
Iron
6/9/05
42,400 |jg/L
15 pg/L
100%
0%
6308500
Iron
8/23/05
18,600 |jg/L
5 pg/L
100%
0%
6308500
Iron
10/5/05
35,200 |jg/L
4 pg/L
100%
0%
6308500
Iron
3/6/06
2,590 |jg/L
5 pg/L
99.9%
0.1%
6308500
Iron
4/5/06
25,600 |jg/L
6 pg/L
100%
0%
46
-------
Tongue River
3.3.5 Sources of Metals
Potential anthropogenic metals sources (e.g., coal mines, CBM, oil and gas fields) in the Tongue River
watershed are located upstream of the Tongue River Reservoir Dam. However, most exceedances were
not observed in this reach. Rather, exceedances (other than iron) were only observed at the most
downstream sampling location at Miles City. Total metals concentrations tend to increase in a
downstream direction, corresponding to increases in the sediment load. This is verified in the synoptic
sampling conducted by USGS in the Tongue River between May 24 and May 26, 2004 (Figure 3-17).
Dissolved concentrations of copper, lead, and iron do not show the same pattern, and do not indicate any
localized impacts from downstream sources.
It is possible that unknown sources (other than in-stream sediment) are causing the increases in total
metals concentrations in a downstream direction. However, a detailed source assessment would be
needed to determine the amount and impact from the unknown sources.
Figure 3-17. Synoptic sampling results for total and dissolved metals concentrations at various sites in
the Tongue River, Montana (May 24-26, 2004).
47
-------
Tongue River
3.4 Total Suspended Solids
The Tongue River from the confluence with Hanging Woman Creek to the mouth was listed on the
Montana 1996 303(d) list as impaired because of suspended solids (MDEQ, 1996). Suspended solids
were not listed as a cause of impairment on the 2006 303(d) list. The following sections present the
suspended solids data for the mainstem Tongue River.
As described in Appendix B, both total suspended solids (TSS) and suspended sediment concentration
(SSC) data were collected in the Tongue River watershed. Where available, both SSC and TSS data are
presented in the following sections to increase the total number and temporal range of samples in the
Tongue River. Summary tables and figures denote where data are SSC, TSS, or a combination of both.
TSS and SSC data for the mainstem Tongue River are available from 1974 to the present, and include
both grab and continuous samples. Grab samples are available from 53 stations in the Tongue River in
Montana and Wyoming, dating from 1974 to 2006, and were collected by multiple governmental agencies
and private organizations. USGS also collected continuous SSC data at the Tongue River at the Stateline
(06306300) and at the Brandenberg Bridge (06307830) for various years between 1974 and 1985. The
available grab sample data are listed in Table 3-22 and the sample site locations are shown in Figure 3-18.
Table 3-22. Summary of TSS and SSC grab samples in the mainstem Tongue River.1
Segment
Station ID
Station Name
Agency
River
Mile
Count
Period of
Record
Headwaters to the
Wyoming Border
06298000
Tongue River Near Dayton,
Wyoming
USGS
271.3
78
1974-1980;
1999-2001
06299980
Tongue River At Monarch,
Wyoming
USGS
246.3
67
1974-1977;
2004-2006
Wyoming Border to the
Tongue River Reservoir
06306300
Tongue River at State Line Near
Decker MT
USGS
215.4
104
2000-2006
1975TO02
Tongue River near the Tongue
River Reservoir
MDEQ
212.1
10
1975-1977
Tongue River Reservoir
Dam to the T&Y Diversion
Dam
2075T004
Tongue River below the Tongue
River Reservoir
MDEQ
201.2
12
1975-1977
06307500
Tongue River at Tongue River
Dam Near Decker, Montana
USGS
201.0
242
1974-1995;
2004-2006
2277TO01
Tongue River near Birney, MT
MDEQ
179.5
25
1975-1979;
1990
06307610
Tongue River Below Hanging
Woman Creek Near Birney,
Montana
USGS
164.9
63
1944-1979
06307616
Tongue River at Birney Day
School Bridge Near Birney,
Montana
USGS
154.3
130
1979-1986;
2004-2006
06307830
Tongue River Below
Brandenberg Bridge Near
Ashland, Montana
USGS
88.1
169
1974-1981;
2000-2006
06307990
Tongue River Above T&Y
Diversion Dam Near Miles City,
Montana
USGS
28.0
45
2004-2006
T&Y Diversion Dam to the
mouth
3582TO01
Tongue River near the Mouth
MDEQ
8.2
17
1975-1980
06308500
Tongue River at Miles City,
Montana
USGS
2.5
265
1974-2006
Data shown for stations with 10 or more samples. Highlighted stations are used in the analyses presented in the following sections.
48
-------
Tongue River
V358IT001
• OMO7M0
jjJiam
eyenne
»»307SI8
*06307610
207STO0J
0BMT5OO
Crow
MONTANA
WYOMING
OWOWOaftftTSTOM
Streams
Counties
Tribal Land
| j Tongue River Watershed
¦ Water Duality Monitoring Stations
s
+
abud
40 Miles
_J
WYOMNG
MONTANA
Big Horn
County
tJbi RiVBf
:ounty
Figure 3-18. Tongue River watershed and location of the TSS/SSC monitoring stations (stations with 10
or more sample dates are shown).
49
-------
Tongue River
3.4.1 Spatial Characterization
The USGS sample stations highlighted above in Table 3-22 have been used to provide a general spatial
characterization of TSS and SSC in the Tongue River. As shown in Figure 3-19 and Table 3-23,
concentrations increases in a downstream direction from the headwaters to the Tongue River Reservoir.
A decrease is then observed from the State line station downstream to the USGS sample station
downstream of the Tongue River Reservoir, resulting from settling in the reservoir. Concentrations
increase again from the Tongue River Reservoir Dam to the mouth.
—~—75th Percentile —¦—25th Percentile —a—Median —*—Average —*—Max —•—Min
River Mile (miles from the mouth)
Figure 3-19. TSS/SSC statistics for USGS stations with 10 or more samples in the mainstem Tongue
River. The entire period of record is shown for each station; grab samples only.
50
-------
Tongue River
Table 3-23. TSS/SSC statistics for various time periods and stations on the mainstem Tongue River, all
available grab samples.1
Station
Statistic
Full Period of Record
Last Five Years''
Tongue River at Dayton, WY
(USGS Gage 06298000)
n
65
0
Min
1
NA
Max
86
NA
Mean
10
NA
Median
4
NA
Tongue River at Monarch, WY
(USGS Gage 06299980)
n
59
43
Min
1
2
Max
352
266
Mean
32
23
Median
14
13
Tongue River at State Line Near Decker, MT
(USGS Gage 06306300)
n
94
78
Min
3
6
Max
697
697
Mean
53
48
Median
39
36
Tongue River at Tongue River Dam Near Decker,
MT
(USGS Gage 06307500)
n
232
51
Min
1
1
Max
213
43
Mean
22
12
Median
16
8
Tongue River at Birney Day School Bridge Near
Birney, MT
(USGS Gage 06307616)
n
120
51
Min
2
2
Max
780
205
Mean
42
26
Median
24
20
Tongue River Below Brandenberg Bridge Near
Ashland, MT
(USGS Gage 06307830)
n
159
78
Min
5
6
Max
23,100
513
Mean
256
69
Median
42
39
Tongue River Above T&Y Diversion Dam Near
Miles City, MT
(USGS Gage 06307990)
n
35
35
Min
11
11
Max
1,750
1,750
Mean
146
146
Median
57
57
Tongue River at Miles City, MT
(USGS Gage 06308500)
n
235
58
Min
5
10
Max
14,000
8,110
Mean
439
476
Median
81
88
Grab samples only. Daily (i.e., continuous) data are not included in this analysis.
2 "Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
51
-------
Tongue River
3.4.2 Comparison to Other Great Plains Streams
TSS and SSC data from multiple sites in the main stem Tongue River were compared to other similar
streams in the Great Plains ecoregion (see Appendix H for further details). Data from 14 streams (25
sites) show that the Tongue River had relatively low TSS and SSC concentrations within the ecoregion.
The median concentrations for all sites in the Tongue River, for both the grab sample and continuous
data, fall within the lower 25th percentile of the data set.
3.4.3 Sediment Source Identification and Load Quantification
Compared to rivers in some other parts of the country, the Tongue River has naturally high suspended
solids due to soils, geology, and topography (see the Tongue River TMDL Status Report - MDEQ, 2003).
Historic accounts (early 1800s) state that the Tongue River was very muddy and shallow, with shifting
sand bars and quicksand present in the channel near Miles City (as summarized in NRCS, 2002).
Furthermore, several species of fish found in the Tongue River are adapted to the high turbidity waters
(paddlefish, sturgeon chub, sauger) (MFWP, 2003). However, there are anthropogenic suspended solid
sources and sinks in the watershed, and the net effect from the sources and sinks is unknown. The
following sections discuss the various suspended solid sources, sinks, and loads throughout the Tongue
River watershed.
3.4.3.1 Tongue River Reservoir (Suspended Solids Sink)
Reservoirs can settle out suspended solids due to slow moving currents and long retention times (Tongue
River Reservoir = 89 days). To determine the effects of the Tongue River Reservoir on suspended solids,
data collected upstream and downstream of the reservoir were evaluated. Data were collected at the
Tongue River near the State Line (station 06306300) and the Tongue River downstream of the Tongue
River Reservoir Dam (station 06307500). Each site has data collected from January 2004 through
September 2006, and has a similar number of suspended solid samples (61). The average concentration
upstream of the reservoir was 46 mg/L, and the average concentration downstream of the reservoir was 13
mg/L. On average, the data suggest that 72 percent of the suspended solids entering the Tongue River
Reservoir are settled out. This effectively divides the Tongue River into two segments - upstream and
downstream of the reservoir. The remainder of this section focuses on the Tongue River downstream of
the reservoir because the reservoir settles out 72 percent of the suspended solids from the Tongue River
upstream of the reservoir. The potential affects of sediment sources above the reservoir are, therefore,
largely inconsequential in the downstream portions of the Tongue River that are the focus of this analysis.
Table 3-24. Summary of suspended solids concentrations collected upstream and downstream of the
Tongue River Reservoir, Montana.
Station
Count
Average
(mg/L)
Median
(mg/L)
Minimum
(mg/L)
Maximum
(mg/L)
Period of
Record
State Line
(06306300)
61
46
31
8
697
2004-2006
Below Tongue River
Reservoir Dam
(06307500)
61
13
8
1
43
2004-2006
52
-------
Tongue River
3.4.3.2 Upland Sediment Loading (Suspended Solids Source)
The Universal Soil Loss Equation (USLE) was used to evaluate upland sediment loading to two Tongue
River tributaries - Hanging Woman Creek and Otter Creek - which comprise 33 percent of the area of the
Tongue River watershed downstream of the Tongue River Reservoir (see Sections 4.4 and 5.4). Two
scenarios were evaluated in each watershed - existing conditions (i.e., existing grazing and agriculture),
and natural conditions (i.e., no grazing or agriculture). The results of the analysis suggest that upland
loads associated with grazing and agriculture are only a small percentage of the total load in each
watershed (0.4 percent in Hanging Woman Creek, and 0.3 percent in Otter Creek). Using this
information, it is conservatively assumed that only a small percentage of the suspended solids load in the
Tongue River (downstream of the reservoir) is due to upland anthropogenic sources.
3.4.3.3 Bank Erosion (Suspended Solids Source)
NRCS performed a Rapid Aerial Assessment and a Riparian Analysis of the Tongue River in 2001 and
2002 (NRCS, 2001, 2002). The Tongue River in Big Horn County and Custer County was surveyed. A
summary of the results pertaining to bank condition are shown below (NRCS, 2001):
• Total Tongue River Length Surveyed: 104.8 miles
• Total Length of Natural Erosion: 2.1 miles (2.0 percent)
• Total Length of Erosion (Unknown Source): 0.68 miles (0.6 percent)
• Total Length of Bank Erosion Affected by Animal Grazing: 0.14 miles (0.1 percent)
In total, there were 0.82 miles of potential anthropogenic erosion observed by NRCS in the Tongue River
in Big Horn and Custer counties. Assuming that erosion occurred at a similar rate in Rosebud County,
there would be an estimated total of 1.74 miles of anthropogenic erosion along the main stem Tongue
River in Montana.
53
-------
Tongue River
3.4.3.4 Suspended Solids Mass Balance
Suspended solid loads in the Tongue River were evaluated at four representative stations - State Line
(06306300), below Tongue River Reservoir Dam (06307500), Brandenberg Bridge (06307830), and
Miles City (06308500) - to estimate sediment load fluxes from upstream to downstream. Since the data
were not collected at the same time, it was not possible to directly compare one station to another.
The relationship between suspended solids
(measured as suspended sediment concentration,
SSC) and flow was evaluated at each station to
facilitate calculation of suspended solids loads for
comparable time periods at each site.
As shown in Table 3-25 and, Figure 3-20 there was
a moderate positive relationship between flow and
SSC at three of the four stations. Just downstream
of the Tongue River Reservoir Dam, no
relationship could be determined, presumably
because of the regulating effect of the reservoir.
Using the flow-SSC relationships, along with daily
flows, daily SSC concentrations were calculated
for each station between January 2000 and
December 2004. This time period was chosen to
represent post construction conditions in the
Tongue River Reservoir, and because the most data
were available for this period. Daily and yearly
loads were then calculated at the State Line,
Brandenberg Bridge, and Miles City. Loads were
estimated at the Tongue River just downstream of
the Tongue River Reservoir Dam using the average
reduction in suspended solids discussed above (74
percent reduction in suspended solids). On
average, concentrations downstream of the
reservoir are 26 percent of the concentrations just
upstream of the reservoir.
100,000
10,000
1,000
SSC = 0.0733(Flow)1.1099
R2 = 0.5227
O)
E.
o
w
OT
100
10
10
100 1,000
Flow (cfs)
10,000
Figure 3-20. Relationship between flow and
SSC in the Tongue River near the Brandenberg
Bridge, Montana.
The uncertainty associated with the use of regression equations to predict SSC based on flow is
acknowledged. However, the general trend of reduced sediment loads downstream of the reservoir is
supported by the observed data. This methodology was merely relied upon as a means to estimate
the relative significance of the load reductions.
54
-------
Tongue River
Table 3-26 shows the estimated suspended solids loads in the Tongue River. The Tongue River Reservoir
removes an estimated 74 percent of the suspended solids load between the State Line and the Tongue
River Reservoir Dam. Loads then increase in a downstream direction up to the Tongue and Yellowstone
(T&Y) Diversion Dam. The T&Y Canal diverts an estimated average of 132 cubic feet per second of
water from the Tongue River between the months of May and October (DNRC, 2006). Assuming that the
suspended solids concentration at the point of diversion is the same as that observed at the closest
upstream point in the Tongue River (Brandenberg Bridge), this results in an estimated average annual loss
of 2,237 tons of suspended solids (Table 3-26). Combined with the suspended solid loss from the Tongue
River Reservoir, the two dams reduce the total suspended solids load at Miles City by an estimated
average of 50 percent (19,071 versus 38,927 tons per year).
As shown above, anthropogenic bank erosion and upland sources constitute a small portion of the total
load at Miles City (together, an average of 2 percent of the total existing load). Even with these
anthropogenic sources, the Tongue River at Miles City has estimated 48 percent less suspended solids
load than would otherwise be present under natural conditions.
Table 3-25. Relationship between flow and SSC at four representative Tongue River stations.
Tongue River Location
Station
Number
Period of
Record
Number of
SSC Samples
Regression Equation
R2
State Line3
06306300
06305500
1971-2004
235
SSC = 1.1681 (Flow)0 6947
0.46
Below Tongue River
Reservoir Dam
06307500
1975-2004
201
NA
NA
Brandenberg Bridgeb
03307830
1974-2004
2,585
SSC = 0.0733(Flow)11099
0.52
Miles Cityb
06308500
1974-2004
3,240
SSC = 0.967(Flow)07"6
0.30
aDue to lack of data at station 06306300, relationship was developed in combination with data from 06306300 and 06305500.
bData obtained from grab samples and from USGS continuous sediment samplers.
Table 3-26. Estimated yearly suspended solids load in the Tongue River, Montana (tons/year).
Year
State Line
TRR Dam
Brandenberg
Bridge''
Miles City
T&Y Ditch
Total Output"
2000
45,170
8,518
5,785
28,430
2,416
30,847
2001
6,768
1,445
3,627
7,275
976
8,251
2002
6,623
1,371
2,161
2,514
969
3,483
2003
43,522
8,355
36,785
53,335
5,349
58,684
2004
5,456
1,476
3,011
3,803
1,474
5,277
Average
21,508
4,233
10,274
19,071
2,237
21,308
incomplete data for 2000 and 2004.
bThe total load that would be delivered to the Yellowstone River if not for the T&Y Diversion Dam.
55
-------
Tongue River
3.5 Other Inorganics (Sulfates)
The agriculture, warm-water fishery and aquatic life beneficial uses of the Tongue River were listed as
impaired by "other inorganics" on the Montana 1996 303(d) list; the other inorganics listing was in
reference to sulfates. Sulfate was not identified as a cause of impairment for any uses on the 2006 303(d)
lists.
Sulfate data for the Tongue River are summarized in Table 3-27 and Figure 3-21. The data do not
indicate any areas of localized sulfate loading, and there are no indications of increasing sulfate
concentrations.
Table 3-27. Summary of surface water sulfate data in the Tongue River (mg/L).
Tongue River Segment
Station
ID
River
Mile
Count
Average
Min
Max
Period of
Record
T&Y Diversion Dam to the Mouth
06308500
2.5
463
226
38
730
1962-2006
Tongue River Reservoir Dam to the
T&Y Diversion Dam
06307990
28.0
34
185
57
268
2004-2006
06307830
88.1
162
194
49
430
1974-2006
06307616
154.3
143
158
34
330
1979-2006
06307610
164.9
64
193
47
420
1974-1979
06307500
201.0
234
145
23
320
1975-2006
WY-MT border to the Tongue River
Reservoir
06306300
215.4
133
116
16
302
1985-2006
Headwaters to the WY-MT Border
06299980
246.3
121
59
11
240
1974-2006
06298000
271.3
220
5
0
19
1966-2002
Data collected by USGS. Stations with 20 or more total sample dates are shown.
© State Line ~ Bradenberg i Miles City
800
A
700 -
600 -
j 500 -
-S-tDOOOCN-S-tDOOOCN-S-tDOOOCN-'S-tD
l"^l"^l"^000000000005050505050000
0)0)0)0)0)0)0)0)0)0)0)0)0)0000
t— t— t— t— t— t— t— t— t— t— t— t— t— (\JC\JC\JCNJ
Figure 3-21. Sulfate data at three USGS stations in the Tongue River, Montana.
56
-------
Hanging Woman Creek
4.0 HANGING WOMAN CREEK
Hanging Woman Creek flows 62 miles from its
origin in Sheridan County, Wyoming to the
confluence with the Tongue River near Birney,
Montana (Figure 4-1). The total watershed covers
roughly 477 square miles. The agriculture, warm-
water fishery and aquatic life beneficial uses were
listed as impaired by flow alterations,
salinity/TDS/chlorides, and metals on the Montana
1996 303(d) list (MDEQ, 1996). The basis for the
1996 listing is unknown. The 2006 303(d) list
reported that aquatic life and fishery beneficial
uses in Hanging Woman Creek were impaired
because of siltation from Stroud Creek to the
mouth (MDEQ, 2006). DEQs Assessment
Record Sheet provides the basis for the listing:
Hanging Woman Creek near the mouth
(Photo by Tetra Tech, Inc.)
"A 1990 assessment conducted for DEO revealed erosion problems due to grazing activity," and,
"obvious signs of livestock watering, bank trampling, tracks on creek bottom; some grazing related cut
and slough; bottom has not been scoured for at least 12 years; gravel is completely buried under silt and
muck," (MDEQ, 1999).
No segments of Hanging Woman Creek have appeared on the Wyoming 303(d) list.
This analysis specifically addresses the listed pollutants and impaired beneficial uses from the 1996 and
2006 303(d) lists (i.e., impairments to the agriculture, warm-water fishery, and aquatic life beneficial uses
associated with salinity/TDS/chlorides, siltation, and metals). Sodium Adsorption Ratio (SAR) is also
addressed given its potential importance related to future Coal Bed Methane development in the
watershed. The purpose of this analysis was to determine if Montana's water quality standards are
currently exceeded in Hanging Woman Creek and, if so, provide insight regarding the potential cause of
the exceedance (i.e., natural versus anthropogenic).
The remainder of this section provides a summary
and evaluation of the available data, and
comparison to the applicable Montana water
quality standards, one pollutant at a time.
Biological data for Hanging Woman Creek are
discussed in Appendix I, and Appendix H
provides a general overview of the hydrologic
characteristics of the Hanging Woman Creek
watershed.
Hanging Woman Creek near the confluence with Horse Creek
(Photo by Tetra Tech, Inc.)
57
-------
Hanging Woman Creek
4.1 Salinity
Specific conductance (SC) data for Hanging Woman Creek are available from 1974 to the present, and
include both grab and continuous samples. Grab samples are available from 20 stations in Hanging
Woman Creek in Montana and Wyoming, dating from 1974 to 2006, and collected by multiple
governmental agencies and private organizations (see Figure 4-1). USGS also collected continuous flow
and salinity data at Hanging Woman Creek near the mouth (06307600) from November 1, 1980 to
September 30, 1987, and from June 1, 2004 to the present. The available data from stations with at least
five samples are listed in Table 4-1 and the sample site locations are shown in Figure 4-1. Where
summary statistics are provided in the following sections (i.e., mean, median, maximum, minimum), only
salinity grab samples are used so that the continuous data do not bias the results.1
Table 4-1. Specific conductance (SC) data for the main stem Hanging Woman Creek.1
Station ID
Station Name
Aqency
River
Mile
n
Period of Record
06307540
Hanging Woman Creek at State Line near Otter,
MT
USGS
46.8
7
1980-1983
2078HA01
Hanging Women Creek
MDEQ
24.5
23
1974-1979
6307570
Hanging Woman Cr Below Horse Creek Near
Birney MT
USGS
24.2
65
1977-1987; 2005
6307600
Hanging Woman Creek Near Birney, MT
USGS
4.0
2,160
1974-1995; 2004-
2006
2278HA01
Hanging Women Creek
MDEQ
3.3
32
1974-1979; 1990
Stations with 5 or more samples are included in this table. Entire period of record is shown. Highlighted stations are used in the analyses presented
in the following sections.
1 Continuous salinity data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years of
record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
58
-------
Hanging Woman Creek
HWC-6-1A
22T8HAI
2178KA02
L178HA01
HWC-S-1
HWC-4-1A
NWC-3-1 ,
06107570
Y15HGWC2-1
C6J0754QJ ^1878 HA01
J4WCJ-1A _
0 2 4 8 Miles
1 i I I I I J I !
HWC4-2
Rosebud
County 451J40J
Big Horn
County
MONTANA
WYOMING
Powder River
County
Sheridan
Courtly
SIrearra
Counbes
[ Hanflirg Woman Creek Watershed
¦ Surface Water Quality Monitoring Stations
HWC-1-3#
HWC-1 -2-_
Figure 4-1, Surface water quality monitoring stations on the main stem of Hanging Woman Creek,
59
-------
Hanging Woman Creek
4.1.1 Spatial Characterization
The USGS sample stations highlighted above in
Table 4-1 have been used to provide a general
spatial characterization of SC in the Hanging
Woman Creek. As shown in Figure 4-2 and Table
4-2, specific conductance decreases in a
downstream direction, from a mean of 7,096 (iS/cm
near the Montana-Wyoming Stateline to 2,412
(iS/cm near the mouth. This may be due to
localized saline seeps, high salinity soils, and
geology in the upper Hanging Woman Creek
watershed which are not present in the lower
watershed (see Appendix G.l.l). However, the
exact cause is unknown.
-75th Percentile
Median
-Max
-25th Percentile
-Average
-Min
14,000
50 25 0
River Mile (miles from the mouth)
Figure 4-2. Statistics for USGS stations with 10 or
more samples in the mainstem Hanging Woman
Creek. The entire period of record is shown for each
station.
Table 4-2. Specific conductance statistics for various time periods, flows, and stations on the
Station
Stat
Full Period of
Record
Last Five
Years2
Low
Flow3
High
Flow3
Average
Flow
Hanging Woman Creek at Stateline
near Otter, Montana
(USGS Gage 06307540)
n
7
NA
NA
NA
NA
Min
785
NA
NA
NA
NA
Max
12,500
NA
NA
NA
NA
Mean
7,096
NA
NA
NA
NA
Median
10,000
NA
NA
NA
NA
Hanging Woman Creek below Horse
Creek near Birney, MT
(USGS Gage 06307570)
n
65
7
17
16
32
Min
473
2,784
1,730
473
2,510
Max
7,010
5,000
5,000
7,010
5,800
Mean
4,050
4,009
3,539
3,918
4,388
Median
4,180
4,243
3,750
4,580
4,410
Hanging Woman Creek near Birney,
Montana
(USGS Gage 06307600)
n
225
33
56
56
113
Min
226
1,650
1,400
226
990
Max
4,220
3,410
3,410
4,220
3,590
Mean
2,412
2,146
2,216
2,093
2,667
Median
2,500
2,130
2,165
2,405
2,700
"Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
3 Low flow, average flow, and high flow were determined from paired flow and SC data at the representative station. Low flow is defined as the lowest
25 percent of flows (0-25th percentile); average flow as the middle 50 percent of flows (25th-75th percentile); high flow as the highest 25 percent of flows
(75 -100th percentile).
60
-------
Hanging Woman Creek
4.1.2 Relationship between Specific Conductance and Discharge
The relationship between discharge and SC was evaluated at two stations in Hanging Woman Creek -
Hanging Woman Creek near the mouth (USGS Gage 06307600) and Hanging Woman Creek near the
confluence with Horse Creek (USGS gage 06307570). The relationship between flow and SC varies
depending on the magnitude of the flow. At less than 8 cubic feet per second, salinity increases with
increasing flow. Above 8 cubic feet per second, salinity decreases with increasing flow.
Near Horse Creek (06307570)
8,000
7,000
6,000
IT 5,000
.O
¦3 4,000
go 3,000
2,000
1,000
0
0.001 0.1 10 1000
Flow (cfs)
Near the Mouth (06307600)
8,000
7,000
6,000
E- 5,000
.o
4,000
w 3,'000
2,000
1,000
0
0.001 0.1 10 1000
Flow (cfs)
Figure 4-3. Relationship between flow and SC at selected USGS stations on the main stem of Hanging
Woman Creek. Entire period of record is shown; grab samples only.
61
-------
Hanging Woman Creek
4.1.3 Comparison to Applicable Standards
Of the two jurisdictions in the Hanging Woman Creek watershed (Wyoming and Montana), only Montana
has approved numeric water quality standards for salinity. Wyoming's salinity standards are narrative.
As a result, this analysis focuses on Montana's salinity standards (described in Appendix B). In the
absence of guidance in the Administrative Rules of Montana (ARM), it is assumed that the "electrical
conductivity" standard can be applied to "specific conductance" (SC) data, which is simply electrical
conductivity that has been corrected to a temperature of 25° Celsius. Both the instantaneous maximum
and monthly average salinity standards for tributaries to the Tongue River (i.e., Hanging Woman Creek)
are 500 (iS/cm. The standards in Hanging Woman Creek do not vary by season.
4.1.3.1 Instantaneous Maximum Salinity Standard
The instantaneous maximum salinity criterion for Hanging Woman Creek is 500 (iS/cm. Based on all of
the available data, the instantaneous maximum salinity standard has been exceeded 99 percent of the time
(2,318 out of 2,331 samples) (Table 4-3). As shown in Figure 4-4, the only time the standard was not
exceeded was during the highest 5 percent of flows.
Table 4-3. SC data and exceedances of the instantaneous maximum water quality standards for
Hanging Woman Creek; daily and grab samples.
Time Period
Season
Numeric
Standard
#
Samples
#
Exceeding
%
Exceeding
"All Data" - October 2,
1974 to June 16, 2006
Growing Season
(March 2 to October 31)
< 500 pS/cm
1623
1618
99.69%
Nongrowing Season
(November 1 to March 1)
< 500 pS/cm
708
700
98.87%
"Past 5 Years" -
October 1,2001 to
September 30, 2006
Growing Season
(March 2 to October 31)
< 500 pS/cm
295
294
99.66%
Nongrowing Season
(November 1 to March 1)
< 500 pS/cm
10
10
100%
4,500
4,000
3,500
3,000
?
£ 2.500
O 2,000
1,500
1,000
500
0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Flow Percentile (%)
Figure 4-4. Specific conductance versus flow percentile for Hanging Woman Creek near the mouth
(USGS Gage 06307600). Entire period of record is shown; grab samples only.
Station 06307600 (near mouth)
... -Water Quality Standard
~ ~
O 8
o * I O o
00 0 *c o«
o O o o
* 1" ~!" V ° Ov !""
> • « 8 OO^ O ®
-©- +¦ ~ o - o O
o to o O ° O /s
o <£ <»
o ~ »o g o °°6 *8 o Oo 8 ^ 0« <» S
? °S° o °«o8 <> 8 o O i o o e
8 o % t
o°o o 0 0 ° °
o o o
o O
o -" O
to o O
o o O O
o °<>o
o
o
O o
o
-t>
o
OOo
o%-
O %
62
-------
Hanging Woman Creek
4.1.3.2 Monthly Average Salinity Standard
The monthly average salinity standard for Hanging Woman Creek is 500 (iS/cm (the same as the
instantaneous maximum standard). However, the Administrative Rules of Montana (ARM 17.30.670) do
not provide guidance regarding the minimum number of samples needed to calculate "monthly average"
values. In the absence of such guidance, the available data were screened to determine the quantity of
available data on a monthly basis and whether or not the available data represent the full range of flow
conditions and the current time period. This analysis is presented in Appendix E and shows that, in
general:
• There are four or more samples per month at only one USGS station - Hanging Woman Creek
near the mouth (06307600) and even here, daily data are limited to two time periods - between
November 1980 and September 1987, and May 2004 to July 2006.
• There is considerably less data during the non-growing season when compared to the growing
season.
• Given the variability in SC on a monthly basis (maximum measured change in one month of
2,708 (iS/cm near the mouth, March 1986), it is logical to conclude that more samples per month
would better represent the "monthly average" than fewer samples per month.
Given the limited data, separate evaluations have been conducted: 1) using the full period of record and;
2) using only the data collected in the past five years. Only months with 4 or more samples were used in
the analysis. The frequency of exceedance is shown in Table 4-4. The monthly average standard is
always exceeded during both the growing season and nongrowing season (where data were available).
Table 4-4. Average monthly SC data and exceedances of the average monthly water quality standards
Time Period
Sampling
Frequency
Season
Numeric
Standard
# Months
with
Samples
# Months
Exceeding
% Months
Exceeding
"All Data" -
October 2,1974
to June 16,2006
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 500
pS/cm
50
50
100%
Nongrowing
Season
(November 1 to
March 1)
< 500
pS/cm
20
20
100%
"Past 5 Years" -
October 1,2001
to September
30, 2006
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 500
pS/cm
12
12
100%
Nongrowing
Season
(November 1 to
March 1)
< 500
pS/cm
0
NA
NA
63
-------
Hanging Woman Creek
4.1.3.3 Nondegradation
Montana's State nondegradation policy requires that when ambient water quality is below 40 percent of
the standard (anti-degradation trigger), up to a 10 percent change in a harmful parameter (such as SC and
SAR) can be allowed without being considered significant (ARM 17.30.715)'. This is illustrated for SC in
Figure 3-7, Section 3.1.3.3. If deemed significant, an authorization to degrade would be required from the
Montana Department of Environmental Quality.
A monthly comparison of SC at station 06307600 to the nondegradation threshold is presented in Figure
4-5. The nondegradation threshold (200 (iS/cm) is exceeded all of the time. It is also exceeded 100
percent of the time at all other available Hanging Woman Creek monitoring stations.
4,500 :
_ 4,000
E
o
-------
Hanging Woman Creek
4.2 SAR
Sodium adsorption ratio (SAR) data for Hanging Woman Creek are available from 1974 to the present,
and include both grab and continuous samples. Grab samples are available from 24 stations in Hanging
Woman Creek in Montana and Wyoming, dating from 1974 to 2006, and collected by multiple
governmental agencies and private organizations. USGS also collected continuous flow and SAR data at
Hanging Woman Creek near the mouth (06307600) from May 22, 2004 to June 16, 2006. The available
data from stations with at least five samples are listed in Table 4-5 and the sample site locations are
shown in Figure 4-1. Where summary statistics are provided in the following sections (i.e., mean, median,
maximum, minimum), only SAR grab samples are used so that the continuous data do not bias the
re suits k
Table 4-5. SAR data for the mainstem Hanging Woman Creek.1
Station ID
Station Name
Agency
River
Mile
n
Period of Record
06307540
Hanging Woman Creek at State Line near Otter,
MT
USGS
46.8
7
1980-1983
2078HA01
Hanging Women Creek
MDEQ
24.5
10
1974-1979
6307570
Hanging Woman Cr Below Horse Creek Near
Birney MT
USGS
24.2
65
1977-1987; 2003;
2005
6307600
Hanging Woman Creek Near Birney, MT
USGS
4.0
405
1974-1995; 2003-
2006
2278HA01
Hanging Women Creek
MDEQ
3.3
17
1974-1979; 1990
4.2.1 Spatial Characterization
The USGS sample stations highlighted in Table 4-1
have been used to provide a general spatial
characterization of SAR in Hanging Woman Creek.
As shown in Figure 4-6 and Table 4-6, SAR
decreases in a downstream direction, from a mean of
10.92 near the Montana-Wyoming Stateline to 4.94
near the mouth. This is potentially due to localized
saline seeps, high SAR soils, and geology in the
upper Hanging Woman Creek watershed which are
not present in the lower watershed (see Appendix
G.l.l).
a:
ss
-75th Ftercentile
Median
-Max
-25th Ftercentile
-Average
-Min
25 0
River Mile (miles from the mouth)
Figure 4-6. SAR Statistics for USGS stations
with 5 or more samples in the mainstem Hanging
Woman Creek. The entire period of record is
shown for each station; grab samples only.
Continuous SAR data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years of
record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
65
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Hanging Woman Creek
Table 4-6. SAR statistics for various time periods, flows, and stations on the mainstem Hanging
Woman Creek, all available grab samples.1
Station
Statistic
Full Period of
Record
Last Five
Years'
Low
Flow'
High
Flow'
Average
Flow'
Hanging Woman Creek at Stateline
near Otter, Montana
(USGS Gage 06307540)
n
7
0
2
2
3
Min
3.19
NA
15.50
3.19
4.27
Max
17.19
NA
17.19
5.79
15.81
Mean
10.92
NA
16.34
4.49
11.58
Median
14.65
NA
16.34
4.49
14.65
Hanging Woman Creek below Horse
Creek near Birney, MT
(USGS Gage 06307570)
n
65
1
17
16
32
Min
2.07
8.59
4.56
2.07
5.50
Max
11.91
8.59
8.59
11.91
10.08
Mean
7.25
8.59
6.83
7.00
7.59
Median
7.49
8.59
6.78
8.27
7.60
Hanging Woman Creek near Birney,
Montana
(USGS Gage 06307600)
n
177
32
46
44
87
Min
0.33
0.33
0.33
0.70
0.36
Max
8.08
6.00
8.08
8.08
7.17
Mean
4.94
3.55
4.25
4.96
5.29
Median
5.04
4.39
4.52
5.28
5.44
"Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
3 Low flow, average flow, and high flow were determined from paired flow and SAR data at the representative station. Low flow is defined as the lowest
25 percent of flows (0-25th percentile); average flow as the middle 50 percent of flows (25th-75th percentile); high flow as the highest 25 percent of flows
(75 -100th percentile).
4.2.2 Relationship between SAR and Discharge
The relationship between discharge and SAR was evaluated at two stations in Hanging Woman Creek -
Hanging Woman Creek near the mouth (USGS Gage 06307600) and Hanging Woman Creek near the
confluence with Horse Creek (USGS gage 06307570). Similar to salinity, the relationship between flow
and SAR varies depending on the flow magnitude. At flows less than 8 cubic feet per second, SAR
increases with increasing flow. After 8 cubic feet per second, SAR decreases with increasing flow.
66
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Hanging Woman Creek
Near Horse Creek (06307570)
a:
<
-------
Hanging Woman Creek
Table 4-7. SAR data and exceedances of the Instantaneous maximum water quality standards for
Hanging Woman Creek; daily and grab samples.
Time Period
Season
Numeric
Standard
#
Samples
#
Exceeding
%
Exceeding
"All Data" - October 2,
1974 to June 16, 2006
Growing Season
(March 2 to October 31)
< 4.5
455
320
70.33%
Nongrowing Season
(November 1 to March 1)
< 7.5
84
5
5.95%
"Past 5 Years" -
October 1,2001 to
September 30, 2006
Growing Season
(March 2 to October 31)
< 4.5
274
170
62.04%
Nongrowing Season
(November 1 to March 1)
< 7.5
7
0
0%
© Station 06307600 (near mouth) ... . Inst Max WQ Standard
A
1
1
1
o
1 1
L !_ o
O
0 « <*>°
o ; |
o
o ° o o° «
0 o ^
o
o 0
© o
» ©
© ©
& oo
~ i ~~
© © © ©
O
©o © °
<***> A . o ©
. © ©° © 0
o © § ©
- - v -<£ f - -by ¦
o ] O <*>©
_0
I 1
O.
. ©
1
"©""""
0
1
t
o
0
0
0
1
1
1
1 1
1 1 <
1
1
1
" 1 1
1 1
1 1
1 1 1 o
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
How Percentile (%)
Figure 4-8. SAR versus flow percentile for Hanging Woman Creek near the mouth (USGS Gage
06307600). Growing season grab samples only.
4.2.3.2 Monthly Average SAR Standard
The monthly average SAR standards for Hanging Woman Creek are 3.0 for the growing season and 5.0
for the nongrowing season. However, the Administrative Rules of Montana (ARM 17.30.670) do not
provide guidance regarding the minimum number of samples needed to calculate "monthly average"
values. In the absence of such guidance, the available data were screened to determine the quantity of
available data on a monthly basis and whether or not the available data represent the full range of flow
conditions and the current time period. This analysis is presented in Appendix F and shows that, in
general:
• There are four or more samples per month at only one USGS station - Hanging Woman Creek
near the mouth (06307600). Daily data were collected between May 2004 and June 2006.
• There is considerably less data during the non-growing season when compared to the growing
season.
• Given the variability in SAR on a monthly basis (maximum measured change in one month of 4.5
in June 2006), it is logical to conclude that more samples per month would better represent the
"monthly average" than fewer samples per month.
68
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Hanging Woman Creek
There is limited data to evaluate the monthly average standard using months with 4 or more samples. The
months with 4 or more samples only occurred between 2004 and 2006, which were relatively dry years.
Therefore, for the purposes of providing a comparison of the available data to the monthly average SAR
criteria, all of the available data were compared to the monthly average standard, as well as only data
collected in the past five years. The frequency of exceedance is shown in Table 4-4.
Table 4-8. Average monthly SAR data and exceedances of the average monthly water quality
standards for Hanging Woman Creek; daily and grab samples.
Time Period
Sampling
Frequency
Season
Numeric
Standard
# Months
with
Samples
# Months
Exceeding
% Months
Exceeding
"All Data" -
October 2,1974
to June 16,2006
1 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
114
112
98.25%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
52
49
94.23%
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
11
11
100%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
0
NA
NA
"Past 5 Years" -
October 1,2001
to September
30, 2006
1 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
18
17
94.44%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
7
5
71.43%
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
11
11
100%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
0
NA
NA
4.2.3.3 Nondegradation
Montana's State nondegradation policy requires that when ambient water quality is below 40 percent of
the standard (anti-degradation trigger), up to a 10 percent change in a harmful parameter (such as SC and
SAR) can be allowed without being considered significant (ARM 17.30.715)'. This is illustrated for SC in
Figure 3-7 and Section 3.1.3.3. If deemed significant, an authorization to degrade would be required from
the Montana Department of Environmental Quality.
A monthly comparison of SAR at station 06307600 to the nondegradation threshold is presented in Figure
4-9. The nondegradation threshold (2.0 and 1.2) is exceeded most of the time during all months.
1 Montana adopted its State nondegradation policy for the parameters of Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) in
March 2006. In June 2006, Montana submitted this change in its regulations to EPA for approval for federal Clean Water Act purposes. EPA has
not yet acted on Montana's submission.
69
-------
Hanging Woman Creek
D 25th-75th Ftercentile ~ Median I Min-Max Average
9.00
8.00
7.00
6.00
< 5.00
-------
Hanging Woman Creek
samples were obtained at USGS Gage 06307600. Between 7 and 24 samples were obtained for each
parameter, and data were available between October 16, 2002 and May 16, 2006.
Table 4-9. Summary of metals data in Hanging Woman Creek near the mouth.
Parameter
Count
Average
(M9/L)
Min
(M9/L)
Max
(M9/L)
Period of Record
Arsenic (Total) (pg/L as As)
24
1.47
0.76
4.00
10/16/02-5/16/06
Cadmium (Total) (pg/L as Cd)
23
0.04
0.02
0.20
4/26/03-5/16/06
Chromium (Total) (pg/L as Cr)
21
3.40
0.50
14.00
5/30/03-5/16/06
Copper (Total) (pg/L as Cu)
24
5.05
2.00
11.80
10/16/02-5/16/06
Iron, (Total), (pg/L as Fe)
24
474.00
202.00
1,410
10/16/02-5/16/06
Lead (Total) (pg/L as Pb)
23
0.49
0.07
1.50
4/26/03-5/16/06
Nickel (Total) (pg/L as Ni)
23
5.84
0.01
10.00
4/26/03-5/16/06
Selenium (Total) (pg/L as Se)
23
1.02
0.21
3.00
4/26/03-5/16/06
Silver (Total) (pg/L as Ag)
7
0.68
0.25
2.00
10/16/02-10/02/03
Zinc (Total) (pg/L as Zn)
24
11.46
0.01
120.00
10/16/02-5/16/06
One iron sample exceeded the chronic criterion of 1,000 (ig/L. The date of the exceedance, the
concentration, and the percent increase from the standard are presented in Table 4-10. At most, iron
samples were obtained once per month, and therefore the exceedances of the chronic criterion were based
on single samples rather than an average of several values. No other metals samples exceeded the metals
standards in Hanging Woman Creek.
Table 4-10. Summary of the iron exceedances in Hanging Woman Creek.
Station
Date of the Exceedance
Chronic
Standard
Value
% Increase from the Standard
Y15HNGWC01
June 27, 2003
1,000 |jg/L
1,410 |jg/L
40.0%
4.4 Siltation/Suspended Solids
Hanging Woman Creek was not listed as impaired because of siltation on the 1996 303(d) list (MDEQ,
1996). The 2006 303(d) lists reported that aquatic life and fishery beneficial uses in Hanging Woman
Creek from Stroud Creek to the mouth were impaired because of siltation (MDEQ, 2006a). Grazing and
agriculture were cited as the source of the siltation impairment, based primarily on a 1990 field survey of
riparian conditions in lower Hanging Woman Creek (MDEQ, 1990).
In the absence of formal numeric sediment criteria, the following presents an evaluation of a suite of
indicators that have been selected to create a measurable point of reference for Montana's narrative
sediment criteria. Details regarding each of the factors discussed below are provided in Appendix B.
It should be noted that application of Montana's narrative sediment standards to Hanging Woman Creek
is complicated by the following factors:
• In their natural condition, prairie streams have more fine sediments than streams in the mountains
or foothills regions in Montana (Bramblett et al., 2005; Zelt et al., 1999; USEPA, 2005). Human
activities that increase fine sediment may simply mimic natural conditions; thus differentiating
between natural and human caused in-stream sediment conditions is especially challenging in this
region.
71
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Hanging Woman Creek
• The harsh environment in this region creates the possibility that natural factors will, on occasion,
impact biota irrespective of human influence (Bramblett et al., 2004). Therefore, it is not always
possible to determine the specific cause of impairment using biological data. This is true when
trying to differentiate between human versus naturally caused biological impairments and also
when trying to determine which pollutant or pollutants (e.g., sediment, metals, salinity, etc.) are
causing the biological impairment.
• Having an understanding of the reference or natural condition is a prerequisite to the application
of Montana's narrative water quality standards for sediment (ARM 17.30.602(19); ARM
17.30.629(2)[d]; ARM 17.30.629(2)[f]). Human influence, though often subtle, is pervasive in the
eastern plains of Montana, and defining reference conditions is difficult. As a result, little
reference data are currently available for defining the natural condition in prairie streams relative
to sediment.
4.4.1 1990 Nonpoint Source Stream Reach Assessment and Physical
Characterization
The Montana Water Quality Bureau conducted a survey of Hanging Woman Creek in October of 1990
using the standardized forms "Nonpoint Source Stream Reach Assessment" and "Physical
Characterization/Water Quality Field Data Sheet", (MDEQ, 1990). This was a qualitative, visual field
survey of Hanging Woman Creek from Stroud Creek to the mouth and represents an interpretation of
conditions existing roughly 17 years ago. Therefore the results should be used with caution. A summary
of the results from the Field Data Sheet (MDEQ, 1990) is provided below.
• Stream was intermittent for most of the reach, having seasonal flows during wet weather and
spring runoff.
• Noted that grazing is affecting bank stability.
• There are a significant number of naturally exposed soils and knobs, possibly aggravated by
livestock.
• Watershed is dominated by grazing and limited cultivation.
• High erosion/sediment loads are natural in the watershed, but the overall condition is aggravated
by grazing.
• Noted moderate to substantial instability, frequent areas of bank erosion/failure (10-40 percent of
the total stream length).
• Mixed streamside vegetation, ranging from "fair" to excellent depending on location.
• Beaver dams, small irrigation dams affecting flows.
• Noted that channel may be dry for periods of time and low enough to preclude/impact aquatic
organisms.
• Grazing noted in 100 percent of the stream corridor.
Overall, there were impacts to Hanging Woman Creek that possibly affected sediment erosion and
delivery. However, the stream is also naturally high in sediment due to naturally exposed soils and
badland areas (NRCS, 2002). Also, it should be noted that only a small portion of the stream was
evaluated and this survey was conducted 17 years ago.
72
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Hanging Woman Creek
4.4.2 Relative Bed Stability Index
The relative bed stability (RBS) metric is used to determine if a stream has excessive sediment
(Kaufmann et al., 1999). Basically, the metric compares the measured median substrate size in the
streambed to the maximum substrate size carried during bankfull events (see Appendix B). The RBS was
calculated at one site in 2001 as part of the EMAP program (Station EMAPS05). Hanging Woman Creek
scored -2.16, which indicates that substrate conditions were "good" with respect to expected substrate
conditions. However, lack of data for other years or segments limit the use of this result.
4.4.3 HII
Bramblett et al. (2004) developed a human influence index (HII) to systematically compare human
disturbance among multiple watersheds (see Appendix B). Measured HII scores ranged from 235 to 845,
and scores greater than 615 were considered "good" (Tom Johnson, personal communications, January
31, 2005). In Hanging Woman Creek, the HII score was calculated at one site in 2001 as part of the
EMAP program (Station EMAPS05). Hanging Woman Creek scored 701, which indicates that there were
few anthropogenic stressors in Hanging Woman Creek as compared to other southeast Montana streams.
4.4.4 Riparian and Bank Condition
Bank stability and riparian vegetation assessments were combined to form a riparian and bank condition
(RBC) index (see Appendix B) (USEPA, 2005). The RBC was calculated at one site in 2001 as part of the
EMAP program (Station EMAPS05). Hanging Woman Creek scored 90, which indicates that bank
stability and vegetation were good with respect to other Great Plains streams.
4.4.5 Rapid Habitat Assessment
As described in Appendix B, rapid habitat assessments are a methodology for quickly evaluating physical
stream parameters. Confluence Consulting assessed stream channel and riparian condition in Hanging
Woman Creek near the confluence with Corral Creek (Station BLMHWC10) (Confluence Consulting,
2003). The site was evaluated with the USEPA forms developed by Peck et. al (2003). Results from the
survey were mixed - while there was little evidence of channel alteration or flow modifications, there was
some evidence of grazing and sediment deposition (Table 4-11). The report stated that:
Livestock grazing was the primary influence on this reach. While banks were stable,
streamside graminoids consisted of short stubble. Extensive stock trails traversed the
area. Green ash andpeachleaf willow (Salix amygdaloides) occurred as isolated, mature
specimens. Relatively large pools and undercut banks provided fish habitat through most
of the reach. Fine, organic muck dominated the streambed. The stream channel was
relatively entrenched; however, it was not clear if this was due to land use or was natural
(Confluence Consulting, 2003).
The site scored a total of 73 percent on the rapid habitat assessment form, which is less than the 81
percent threshold for optimal conditions (see Appendix B).
73
-------
Hanging Woman Creek
Table 4-11. Results of the Rapid Habitat Assessment for site BLM-HWC10.
Parameter
Score (Out of 20
Possible Points)
Bank vegetative protection
15
Channel alteration
19
Channel flow status
19
Channel sinuosity
15
Condition of banks
15
Epifaunal substrate
15
Grazing or other disruptive pressure
8
Instream cover
12
Pool substrate characterization
12
Pool variability
16
Riparian vegetation zone width
19
Sediment deposition
11
Percent of possible score
73%
>81 % indicates an optimal condition 75-56% indicates a sub-optimal condition
<49-29% indicates a marginal condition <23% indicates a poor condition
4.4.6 NRCS Riparian Assessment
NRCS inventoried point and linear features for Hanging Woman Creek in Big Horn County (see
Appendix B). There were few identified features - floodplain dikes, channel plugs, and bridges/fords
(Figure 4-10) (NRCS, 2001). Features in Rosebud County were not inventoried. Channelization was
noted in several areas; however, NRCS could not determine if the channelization was natural or
anthropogenic. Woody vegetation was absent from most of the upstream portions of Hanging Woman
Creek (Figure 4-10, Reach 1). NRCS noted that the upstream reaches were also intermittent with
groundwater-fed pools. Saline soils and seeps were common in the upstream reaches (evidenced by alkali
deposits, pan spots, exposure of salt bearing shales, salt crusts, and greasewood), and likely limited
riparian establishment as evidenced during the survey (NRCS, 2001). Near the mouth of Hanging
Woman Creek, the gradient is low and flows are affected by backwater from the Tongue River. Increased
sediment deposition was noted here (Reach 6) due to this phenomenon.
Only three floodplain dikes were noted as limiting floodplain access in Hanging Woman Creek. NRCS
reported that, "numerous other such systems were noted, however, dike placement did not appear to have
much potential to limit regular floodplain access, and so were not recorded," (NRCS, 2001). Dikes are
more prevalent in the downstream reaches (Rosebud County), where flows are higher. However,
information about these systems was not available at the time of this report.
Results of the riparian assessment showed that most Hanging Woman Creek segments were ranked as
"sustainable," indicating good channel and riparian conditions (NRCS, 2002). The most upstream reach
(Reach 1), however, was ranked as "Not Sustainable," (Table 4-12). This was mostly due to a high
degree of incisement, lack of woody vegetation, and lack of deep binding root mass, which may or may
not be related to recent human-caused sources. Overall, NRCS noted that, "sediment supply and
deposition appeared to be in balance" throughout the watershed (NRCS, 2002).
74
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Hanging Woman Creek
Table 4-12. Results of the NRCS riparian assessment in Hanging Woman Creek
Segment1'
Incisement
Lateral Cutting
Sediment Balance
Soil
Binding Root
Mass
Woody
Establishment
% Utilization
Riparian/Wetland
Characteristics
Floodplain
Irrigation Impacts
Land Use
Activities
Subtotal
Potential Score
% of Potential
Sustainability
Rating
HWC-1-1
4
R
3
o
NA
NA
o
o
NA
NA
15
41
37%
Not Sustainable
HWC-1-2
6
6
6
3
4
NA
NA
4
6
8
8
51
57
89%
Sustainable
HWC-1-3
6
6
6
3
4
NA
NA
4
6
NA
NA
35
41
85%
Sustainable
HWC-2-1
8
6
6
3
6
NA
NA
6
6
8
6
55
57
96%
Sustainable
HWC-3-1
6
6
6
3
6
NA
NA
6
6
8
6
53
57
93%
Sustainable
HWC-4-1
6
6
4
3
4
2
4
4
6
8
6
53
69
77%
Sustainable
HWC-5-1
6
6
4
3
4
4
4
6
6
8
6
57
69
83%
Sustainable
HWC-6-1
6
6
4
3
6
4
4
6
6
8
6
59
69
86%
Sustainable
HWC-6-2
6
6
4
3
6
6
3
6
6
8
8
62
69
90%
Sustainable
Sustainable: >75%; At Risk: 50-75%; Not Sustainable: <50%
Note: targets were adopted from the NRCS Report, "Tongue River Stream Corridor Assessment Montana Reaches - Phase II - Physical Habitat
Assessment."
aSee Figure 4-10 for segment locations.
75
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Hanging Woman Creek
Streams
' Counties
/ V
Linear and Point Features
• Bridge
o Channel Plugs
o Ford
m Floodplain Dike
NRCS Reach Numbers
A/1 A/4
l a/
Rosebud
County
Powder River
County
Sheridan
County
Big Horn
County
Figure 4-10. NRCS riparian assessment for Hanging Woman Creek.
76
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Hanging Woman Creek
4.4.7 In-Stream Sediment Concentrations
Total suspended solids (TSS) and suspended sediment concentrations (SSC) were collected at multiple
sites and years in Hanging Woman Creek (Table 4-13). Between 1974 and 2006, there were 314 TSS or
SSC samples collected in the stream. As described in Appendix B, TSS and SSC data are combined and
used together in this analysis.
Without an appropriate reference stream, it is impossible to determine if the available TSS and SSC data
are exceeding reference conditions. Overall, there were no discernable temporal trends in the data (Figure
4-11). Also, concentrations were relatively similar at all stations and did not indicate localized sediment
loading (Figure 4-12).
Table 4-13. Summary of TSS and SSC data, Hanging Woman Creek.
Station
Count
Median
Average
Min
Max
Period of
Record
2278HA01 (Downstream)
24
22
26
4
131
1975-1990
6307600
173
65
87
7
650
1974-2006
Y15HNGWC01
6
9
16
2
58
2003-2003
2278EA01
18
2
9
0.4
47
1978-1979
2178HA02
1
11
11
11
11
1979-1979
2178HA01
1
14
14
14
14
1979-1979
Y15HNGWC02
5
43
39
17
63
2003-2003
6307570
60
47
62
5
609
1977-1987
2078HA01
18
9
12
2
31
1978-1979
Y15HGWC2-1
1
14
14
14
14
2002-2002
6307540 (Upstream)
7
24
37
9
120
1980-1983
All Stations
314
14
30
0.4
650
1975-2006
Data collected by USGS, NRCS, and MDEQ. Station locations shown in Figure 4-1.
Suspended sediment data from Hanging Woman Creek were compared to other similar streams in the
Great Plains ecoregion (see Appendix K). Data from 19 streams (21 sites) show that Hanging Woman
Creek had relatively low TSS and SSC concentrations (fourth lowest median concentration), and similar
variability to other streams in the ecoregion. There was no indication of elevated TSS or SSC
concentrations when compared to other regional streams.
77
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Hanging Woman Creek
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006
Figure 4-11. TSS and SSC data for Hanging Woman Creek near the mouth (USGS Gage 06307600).
—~—75th Percentile —*—Median —a—Max Min —•—Average —x- 25th Percentile
700
0 —
50
Figure 4-12.
45 40 35 30 25 20 15 10 5 0
River Mile
TSS and SSC data for Hanging Woman Creek stations 06307540, 06307570, and 06307600.
78
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Hanging Woman Creek
4.4.8 Sediment Source Identification and Load Quantification
As described in the March 2003 Phase I report (MDEQ, 2003), soils in the Hanging Woman Creek
watershed are naturally highly erodible, with slow to very slow infiltration rates. These attributes, in
combination with semiarid conditions, flashy rain events, and sparse ground cover, result in naturally high
sediment erosion. Buttes and badlands occur throughout the landscape, and saline or sodic soils limit
plant growth in several areas. NRCS (2002) reported that:
The majority of the Tongue River watershed is mapped as yielding 0.2 to 0.5 acre-
feet/mile2/year of sediment. Using an average bulk density of sixty-pounds/cubic foot,
these volumes would be equivalent to 0.4 to 1.0 tons/acre/year. Juvan estimated percent
contribution of erosion source was forty-percent gully and sixty percent sheet erosion
within most of the Tongue River-Montana watershed (Juvan, undated).
Bison were once native to this area and likely impacted streams and upland rangeland.
Historic accounts (mid 1800s) indicated that there was widespread scarcity of grasses and water
throughout the Tongue River watershed due to bison (NRCS, 2002). Cattle are currently the predominant
agricultural resource in the watershed (NASS, 2002). It is well documented that cattle have the potential
to impact the landscape, if not managed properly (Hoorman and McCutcheon, 2007; Haan et al., 2004).
In the uplands, decreased ground cover, increased erosion, and the promotion of invasive species can
occur from overgrazing. In the lowlands and stream valleys, cattle grazing can have direct impacts to the
stream and riparian area (destabilized stream banks, lack of riparian cover, habitat degradation).
However, the relative contribution of sediment to the stream is unknown.
Other potential sediment sources within the watershed may include unpaved roads, irrigated agriculture,
various drainage features (stock ponds and irrigation dikes) that may alter both the flow and sediment
dynamics in the system, and disturbed lands associated with the construction and operation of coal bed
methane development. Irrigation can affect flows and sediment supply in the stream, resulting in a lack
of flushing flows and sediment imbalances. The effect of irrigation on in-stream sediment and sediment
supply is unknown and unquantiflable at the time of this report.
Upland sediment loads were estimated using soil survey data, GIS, and the Universal Soil Loss Equation
(USLE). Details of the analysis for all watersheds are described in Appendix B. In the Hanging Woman
Creek watershed, there was very little difference between the existing and "natural" upland sediment
delivery. Natural conditions are defined as "no human alterations, resulting in no active agricultural land
and increased total vegetative ground cover." USLE calculations showed that there is only a 0.42 percent
increase in sediment load over naturally occurring conditions (17,992 versus 18,069 tons of sediment per
year). This suggests that human management has not had a major effect on upland sources in the
Hanging Woman Creek watershed. It should be noted that this analysis does not take into account
streambank erosion or riparian degradation.
As evidenced by NRCS (2002), cattle have impacted riparian areas and stream banks in several areas.
The extent of this effect is unknown, although NRCS did not find any major areas of bank erosion in their
2001 survey (NRCS, 2002). The 1990 Montana Water Quality Bureau survey noted moderate to
substantial instability with frequent areas of bank erosion/failure (10-40 percent of the total stream
length).
To estimate bank erosion in Hanging Woman Creek, a simple analysis was performed using literature
values and conservative assumptions. It was assumed that stream banks are eroding an average of 0.10
feet per year, and have a height of one foot (adapted from Rosgen, 1996). Although the 2001 NRCS
riparian assessment found 43.0 of 47.8 assessed miles to be "sustainable", it is conservatively assumed
79
-------
Hanging Woman Creek
that bank erosion occurs along 40 percent (based on the worst-case estimate from the previously
discussed 1990 survey) of the total stream bank length (126 miles), and all of that erosion is human-
caused. Assuming an average bulk density of 60 pounds per cubic feet, this equates to an average
sediment load of 786 tons of sediment per year from bank erosion. From this worst-case analysis, it is
estimated that 18,000 tons of sediment per year are contributed to the stream from upland sources.
Therefore, using conservative estimates, streambank erosion is less than five percent of the total sediment
load delivered to the stream. This analysis shows that streambank erosion is relatively small compared to
the total amount of sediment contributed from upland erosion.
80
-------
Otter Creek
5.0 OTTER CREEK
Otter Creek flows 103 miles from its origin in
Powder River County, Montana to the confluence
with the Tongue River near Ashland. Montana
(Figure 5-1). The total watershed covers roughly
709 square miles. The agriculture, warm-water
fishery, and aquatic life beneficial uses were
listed as impaired by salinity/ TDS/chlorides,
metals, suspended solids, and other habitat
alterations on the Montana 1996 303(d) list
(Segment MT42C002-020) (MDEQ, 1996). The
basis for the 1996 listing is unknown. There
were insufficient credible data to make an
impairment determination for the 2006 303(d) list
(MDEQ, 2006a).
Otter Creek near Ashland, Montana
(Photo by Tetra Tech, Inc.)
This analysis specifically addresses the listed
pollutants and impaired beneficial uses from the
1996 303(d) list (i.e., impairments to the agriculture, warm-water fishery, and aquatic life beneficial uses
associated with salinih/TDS/chlorides. suspended solids, and metals). Sodium Adsorption Ratio (SAR)
is also addressed given its potential importance related to future Coal Bed Methane development in the
watershed. The purpose of this analysis was to determine if Montana's water quality standards are
currently exceeded in Otter Creek and, if so, provide insight regarding the potential cause (i.e., natural
versus anthropogenic).
The remainder of this section provides a summary and evaluation of the available data, and comparison to
the applicable Montana water quality standards, one pollutant at a time. Biological data for Otter Creek
are discussed in Appendix X, and Appendix H provides a general overview of the hydrologic
characteristics of the Otter Creek watershed.
81
-------
Otter Creek
5.1 Salinity
Specific conductance (SC) data for Otter Creek are available from 1974 to the present, and include both
grab and continuous samples. Grab samples are available from 40 stations in the main stem of Otter
Creek, collected by multiple governmental agencies and private organizations (see Figure 5-1). USGS
collected continuous flow and salinity data at Otter Creek near the mouth (06307740) from November 1,
1980 to August 31, 1985, and from May 25, 2004 to the present. Continuous flow and salinity data were
also obtained at Otter Creek below Fifteen Mile Creek (USGS Gage 06307717) from October 5, 1983 to
September 30, 1985. The available data are listed in Table 5-1 and the sample site locations (i.e., those
with 10 or more data points) are shown in Figure 5-1. Where summary statistics are provided in the
following sections (i.e., mean, median, maximum, minimum), only salinity grab samples are used so that
the continuous data do not bias the results™
Table 5-1. Specific conductance (SC) data for the main stem Otter Creek.1
Station ID
Station Name
Agency
River
Mile
n
Period of Record
06307665
Otter Creek Near Otter, MT
USGS
90.06
56
1977-1984
06307717
Otter Cr Below Fifteenmile Creek Near Otter, MT
USGS
43.01
994
1982-1985
06307725
Otter Creek Above Tenmile Creek Near Ashland,
MT
USGS
37.07
39
1977-1983
2579OT01
Otter Creek
MDEQ
4.40
29
1974-1983
06307740
Otter Creek at Ashland MT
USGS
3.27
2,339
1974-1995; 2004-
2006
Stations with 10 or more samples are included in this table.
m Continuous salinity data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years
of record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
82
-------
Otter Creek
2380QT01
06307717
OC-6-1 I
I281OT01
4S1T3210608f1
> StBDOTOI
WMTPsfSsVI ¦
451330106100201 *
oe-o-t ,
4511341 06095901
45043710605521
453601106161001
4535S7106161401
OC-10-1
06307740
25790T01
OC-9-1
4533231D61J5&D1
43314.510612410^
453117106110501
24300T01
45J017106102601
OG-7-1
452933106101601 \
452849106095701
452657106095501
452S4210S09t20l
OC-5-1
06307725
Rosebud
County
OC-4-1 ,
Y160TRC
4521061060B5301'
• JflBIOTOI
* 06307665
Big Horn
County
Powder Rtvcr
County
MONTANA
WYOMING
Streams
Counties
Otter Creek Watershed
Surface Water Quality Monitoring Stations
8 Miles
Sheridan
County
WVOMIMG
HOOTftttA
Figure 5-1. Surface water quality monitoring stations on the main stem of Otter Creek.
83
-------
Otter Creek
5.1.1 Spatial Characterization
The USGS sample stations in Table 5-1 have been used to provide a general spatial characterization of SC
in Otter Creek. As shown in Figure 5-2 and Table 5-2, specific conductance decreases in a downstream
direction, from a mean of 6,164 (iS/cm near Otter, Montana to 2,728 (iS/cm near the mouth at Ashland,
Montana. This is potentially due to localized saline seeps, high salinity soils, and geology in the upper
Otter Creek watershed which are not present in the lower watershed (see Appendix G.2.1).
-75th Percentile
-25th Percentile
Median
Average
- Max
-Min
E
o
-------
Otter Creek
Table 5-2. Specific conductance statistics for various time periods, flows, and stations on the
mainstem Otter Creek, all available grab samples.1
Station
Statistic
Full Period of
Record
Last Five
Years''
Low
Flow'
High
Flow'
Average
Flow'
Otter Creek near Otter MT
(USGS Gage 06307665)
n
56
0
16
14
26
Min
2,070
NA
2,070
4,300
5,350
Max
8,480
NA
8,480
6,700
7,000
Mean
6,164
NA
6,228
5,869
6,283
Median
6,200
NA
6,400
5,900
6,200
Otter Creek below Fifteenmile Creek
near Otter, MT
(USGS Gage 06307717)
n
32
0
8
6
18
Min
1,440
NA
3,300
1,440
2,430
Max
3,940
NA
3,940
3,650
3,580
Mean
3,253
NA
3,681
2,808
3,211
Median
3,325
NA
3,660
2,865
3,240
Otter Creek above Tenmile Creek
near Ashland, MT
(USGS Gage 06307725)
n
39
0
10
10
19
Min
680
NA
2,830
680
2,520
Max
4,400
NA
4,400
3,490
3,730
Mean
3,159
NA
3,457
2,902
3,138
Median
3,160
NA
3,340
3,175
3,110
Otter Creek near Ashland, MT
(MDEQ Gage 2579OT01)
n
29
0
3
4
8
Min
2,250
NA
2,670
3,000
2,359
Max
3,399
NA
2,950
3,310
3,399
Mean
2,912
NA
2,827
3,163
2,890
Median
2,900
NA
2,860
3,050
2,900
Otter Creek at Ashland, MT
(USGS Gage 06307740)
n
218
41
56
53
109
Min
325
1,960
2,200
325
1,840
Max
3,960
3,180
3,420
3,960
3,900
Mean
2,728
2,688
2,786
2,479
2,819
Median
2,800
2,760
2,795
2,700
2,820
"Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
3 Low flow, average flow, and high flow were determined from paired flow and SC data at the representative station. Low flow is defined as the lowest
25 percent of flows (0-25th percentile); average flow as the middle 50 percent of flows (25th-75th percentile); high flow as the highest 25 percent of flows
(75 -100th percentile).
85
-------
Otter Creek
5.1.2 Relationship between Specific Conductance and Discharge
The relationship between discharge and SC was evaluated at two stations in Otter Creek - Otter Creek
near the mouth (USGS Gage 06307740) and Otter Creek near Otter, Montana (USGS gage 06307665).
There is a weak inverse relationship between flow and SC at both stations.
Near Otter, MT (06307665)
E
.o
W
3
o
w
0.01
0.1
y = -100.64Ln(x) +5897.4
R2 = 0.027
1 10
Flow (cfs)
100 1000
9,000
8,000
7,000
~ 6,000
55 5.°00
— 4,000
O
3,000
2,000
1,000
0
Near the Mouth (06307740)
y = -128.43Ln(x)+ 2810.5
R2 = 0.1186
°° o
0.01
0.1
Figure 5-3.
1 10 100 1000
Flow (cfs)
Relationship between flow and SC at selected USGS stations on the main stem of Otter
Creek. Entire period of record is shown; grab samples only.
5.1.3 Comparison to Applicable Standards
The following sections compare the available observed salinity data in Otter Creek to Montana's numeric
salinity standards. Since there is no guidance in the Administrative Rules of Montana (ARM), it is
assumed that the "electrical conductivity" standard can be applied to "specific conductance" (SC) data,
which is simply electrical conductivity that has been corrected to a temperature of 25° Celsius. Both the
instantaneous maximum and monthly average salinity standards for tributaries to the Tongue River (i.e.,
Otter Creek) are 500 (iS/cm. The standards do not vary per season.
86
-------
Otter Creek
5.1.3.1 Instantaneous Maximum Salinity Standard
The instantaneous maximum salinity criterion for Otter Creek is 500 (iS/cm. Based on all of the available
data in the main stem of Otter Creek, the instantaneous maximum salinity standard has been exceeded
almost 100 percent of the time during both the growing and nongrowing seasons. As shown in Figure 5-
4, the only time the standard was not exceeded was during the highest 5 percent of flows.
Table 5-3. SC data and exceedances of the instantaneous maximum water quality standard for Otter
Time Period
Season
Numeric
Standard
#
Samples
#
Exceeding
%
Exceeding
"All Data" - January 17,
1974 to September 30, 2006
Growing Season
(March 2 to October 31)
< 500 pS/cm
2,523
2,519
99.8%
Nongrowing Season
(November 1 to March 1)
< 500 pS/cm
994
993
99.9%
"Past 5 Years" -
October 1,2001 to
September 30, 2006
Growing Season
(March 2 to October 31)
< 500 pS/cm
543
543
100%
Nongrowing Season
(November 1 to March 1)
< 500 pS/cm
7
7
100%
O Station 06307740 (near mouth)
Water Quality Standard
E
o
4,500
4,000
3,500
3,000
2,500
O 2,000
co
1,500
1,000
500
0
0
o
O vv
£*4 .~ * - :j -j- ;
~.* -~*1'?~S1 - IK t». ..
0
0
:<>
^ _
^ ~ ~
>1 ® ° <00 0
oo ~ O o
% °
0
oc
o
o o
o
1 1 1 1
: *
; ;
y - ^
0% 10% 20% 30% 40% 50% 60%
Flow Percentile (%)
70%
80%
90%
100%
Figure 5-4. Specific conductance versus flow percentile for Otter Creek near the mouth (USGS Gage
06307740). Entire period of record is shown; grab samples only.
87
-------
Otter Creek
5.1.3.2 Monthly Average Salinity Standard
The monthly average salinity standard for Otter Creek is 500 (iS/cm. However, the Administrative Rules
of Montana (ARM 17.30.670) do not provide guidance regarding the minimum number of samples
needed to calculate "monthly average" values. In the absence of such guidance, the available data were
screened to determine the quantity of available data on a monthly basis and whether or not the available
data represent the full range of flow conditions and the current time period. This analysis is presented in
Appendix E and shows that, in general:
• There are four or more samples per month at only one USGS station - Otter Creek near the mouth
(06307740). Daily data were collected between November 1980 and August 1985, and May 2004
to September 2006.
• There is considerably less data during the non-growing season when compared to the growing
season.
• Given the variability in SC on a monthly basis (maximum measured change in one month of
3,090 (iS/cm near the mouth, January 1975), it is logical to conclude that more samples per month
would better represent the "monthly average" than fewer samples per month.
For the purposes of providing a comparison of the available data to the monthly average SC criteria, all of
the available data were compared to the monthly average standard, as well as only data collected in the
past five years. Only months with 4 or more samples were used in the analysis. The frequency of
exceedances is shown in Table 5-4. The monthly average standard is always exceeded during both the
growing season and nongrowing season (where data were available).
Table 5-4. Average monthly SC data and exceedances of the average monthly water quality standard
for Otter Creek for the last five years assuming > four daily and/or grab samples per month.
Time Period
Sampling
Frequency
Season
Numeric
Standard
# Months
with
Samples
# Months
Exceeding
% Months
Exceeding
"All Data" -
January 17,1974
to September 30,
2006
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 500
pS/cm
56
56
100%
Nongrowing
Season
(November 1 to
March 1)
< 500
pS/cm
20
20
100%
"Past 5 Years" -
October 1,2001
to September 30,
2006
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 500
pS/cm
20
20
100%
Nongrowing
Season
(November 1 to
March 1)
< 500
pS/cm
0
NA
NA
88
-------
Otter Creek
5.1.3.3 Nondegradation
Montana's State nondegradation policy requires that when ambient water quality is below 40 percent of
the standard (anti-degradation trigger), up to a 10 percent change in a harmful parameter (such as SC and
SAR) can be allowed without being considered significant (ARM 17.30.715)". This is illustrated for SC in
Figure 3-7, Section 3.1.3.3. If deemed significant, an authorization to degrade would be required from the
Montana Department of Environmental Quality.
A monthly comparison of SC at station 06307740 to the nondegradation threshold is presented in Figure
5-5. The nondegradation threshold (200 (iS/cm) is exceeded all of the time.
4,500
4,000
3,500
3,000
O
W 2,500
CO 2,000
1,500
1,000
500
0
Figure 5-5. SC data and nondegradation thresholds for Otter Creek (near the mouth). Entire period of
record is shown; grab samples only.
[| 25th-75th Ftercentile ~ Median
| Min-Max
Average
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
5.1.4 Sources of Salinity and Their Influence on Otter Creek
As described above, exceedances of Montana's salinity standards have been observed in Otter Creek.
However, it is unclear if the observed exceedances were due to natural or anthropogenic sources (or a
combination of both).
A modeling analysis similar to that which was described in Section 3.1.4 was conducted to estimate the
salinity levels that may have occurred in the absence of human influence (see Appendix J).
Mean SC is slightly lower (at P = 0.05) under the simulated natural condition when compared to the
simulated existing condition (i.e., a mean of 2,806 (iS/cm versus a mean of 2,826 (iS/cm). However, the
simulated values are so close (i.e., < 1 percent difference) that the model results suggest the exceedances
of the salinity standard in Otter Creek are due largely to natural causes. See the Modeling Report for
details and a discussion of uncertainty.
n Montana adopted its State nondegradation policy for the parameters of Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) in
March 2006. In June 2006, Montana submitted this change in its regulations to EPA for approval for federal Clean Water Act purposes. EPA has
not yet acted on Montana's submission.
89
-------
Otter Creek
5.2 SAR
Sodium adsorption ratio (SAR) data for Otter Creek are available from 1974 to the present, and include
both grab and continuous samples. Grab samples are available from 23 stations in the main stem of Otter
Creek, and were collected by multiple governmental agencies and private organizations. USGS also
collected continuous flow and SAR data at Otter Creek near the mouth (06307740) from May 25, 2004 to
Present. The available data are listed in Table 5-5 and the sample site locations (i.e., those with 10 or
more data points) are shown in Figure 5-1. Where summary statistics are provided in the following
sections (i.e., mean, median, maximum, minimum), only SAR grab samples are used so that the
continuous data do not bias the results.0
Table 5-5. SAR data for the main stem Otter Creek.1
Station ID
Station Name
Aqency
River
Mile
n
Period of Record
06307665
Otter Creek Near Otter, MT
USGS
90.06
55
1977-1984
4517321060850012
Otter Creek Below Taylor Creek Near Otter,
MT
USGS
62.55
12
1977-1983; 2003;
2005
06307717
Otter Cr Below Fifteenmile Creek Near Otter,
MT
USGS
43.01
30
1982-1985
06307725
Otter Creek Above Tenmile Creek Near
Ashland, MT
USGS
37.07
37
1977-1983
2579OT01
Otter Creek
MDEQ
4.40
13
1974-1983
063077403
Otter Creek at Ashland MT
USGS
3.27
666
1974-1995; 2003-
2006
Stations with 10 or more grab samples are included in this table.
includes samples from station Y16OTTRC02, which was sampled at the same location as the USGS gage by USEPA in 2003.
includes samples from station Y16OTTRC01, which was sampled at the same location as the USGS gage by USEPA in 2003.
5.2.1 Spatial Characterization
The USGS sample stations in Table 5-5 have been used to provide a general spatial characterization of
SAR the Otter Creek. As shown in Figure 5-6 and Table 5-6, SAR decreases in a downstream direction,
from a mean of 7.53 near Otter, Montana to 5.41 near the mouth. This is potentially due to localized
saline seeps, high SAR soils, and geology in the upper Otter Creek watershed (see Appendix G).
0 Continuous SAR data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years of
record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
90
-------
Otter Creek
-75th Percentile —¦—25th Percentile a Median —x—Average —*—Max —•—Min
Figure 5-6.
90 80 70 60 50 40
River Mile (miles from the mouth)
SAR statistics for USGS stations with 10 or more samples in the mainstem Otter Creek. The
entire period of record is shown for each station; grab samples only.
91
-------
Otter Creek
Table 5-6. SAR statistics for various time periods, flows, and stations on the mainstem Otter Creek, all
available grab samples.1
Station
Statistic
Full Period of
Record
Last Five
Years''
Low
Flow'
High
Flow'
Average
Flow'
Otter Creek near Otter MT
(USGS Gage 06307665)
n
55
0
15
14
26
Min
4.14
NA
4.14
5.89
6.60
Max
10.68
NA
10.15
8.91
10.68
Mean
7.53
NA
7.71
7.25
7.57
Median
7.46
NA
8.05
7.26
7.42
Otter Cr below Taylor Creek near
Otter, MT
(USGS Gage 451732106085001)
n
12
7
3
3
5
Min
4.04
4.80
4.91
4.28
4.07
Max
5.87
5.87
5.50
5.01
5.87
Mean
5.00
5.37
5.30
4.74
5.15
Median
4.97
5.49
5.49
4.93
5.15
Otter Creek below Fifteenmile Creek
near Otter, MT
(USGS Gage 06307717)
n
30
0
8
8
14
Min
4.23
NA
5.30
4.27
4.23
Max
6.52
NA
6.52
5.35
5.94
Mean
5.32
NA
5.85
4.87
5.27
Median
5.32
NA
5.70
4.82
5.40
Otter Creek above Tenmile Creek
near Ashland, MT
(USGS Gage 06307725)
n
37
0
9
9
19
Min
1.78
NA
4.99
1.78
4.35
Max
7.32
NA
7.32
5.68
6.70
Mean
5.25
NA
6.00
4.70
5.16
Median
5.09
NA
5.79
5.03
5.09
Otter Creek near Ashland, MT
(MDEQ Gage 2579OT01)
n
13
0
NA
NA
NA
Min
5.42
NA
NA
NA
NA
Max
6.79
NA
NA
NA
NA
Mean
5.84
NA
NA
NA
NA
Median
5.75
NA
NA
NA
NA
Otter Creek at Ashland, MT
(USGS Gage 06307740)
n
182
40
47
45
90
Min
0.34
0.34
0.78
1.00
0.34
Max
7.16
6.86
7.16
6.96
6.86
Mean
5.36
4.41
5.88
4.96
5.30
Median
5.74
5.63
6.16
5.36
5.69
"Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
3 Low flow, average flow, and high flow were determined from paired flow and SAR data at the representative station. Low flow is defined as the lowest
25 percent of flows (0-25th percentile); average flow as the middle 50 percent of flows (25th-75th percentile); high flow as the highest 25 percent of flows
(75th-100th percentile).
92
-------
Otter Creek
5.2.2 Relationship between SAR and Discharge
The relationship between discharge and SAR was evaluated at two stations in Otter Creek - Otter Creek
near the mouth (USGS Gage 06307740) and Otter Creek near the Otter, Montana (USGS gage
06307665). There is a weak inverse relationship between flow and SAR at both stations.
Near Otter, MT (06307665)
12
10
a.
< 6
w
4
2
oo
11
o
•' 'o ~
0.01 0.1
y = -0.1365Ln(x) +7.1674
R2 = 0.0364
1 10 100 1000
Flow (cfs)
12
10
01 r.
< 6
w
Near the Mouth (06307740)
y=-0.3916Ln(x) +5.9814
R2 = 0.3907
0.01
0.1
1 10 100 1000
Flow (cfs)
Figure 5-7. Relationship between flow and SAR at selected USGS stations on the mainstem of Otter
Creek. Entire period of record is shown; grab samples only.
5.2.3 Comparison to Applicable Standards
The following sections compare the available observed SAR data in Otter Creek to Montana's numeric
SAR standards. The standards are seasonal, with separate criteria for the growing season (March 2 -
October 31) and non-growing season (November 1 - March 1) and include monthly average criteria as
well as instantaneous maximum criteria.
93
-------
Otter Creek
5.2.3.1 Instantaneous Maximum SAR Standard
The instantaneous maximum SAR criteria for Otter Creek are 4.5 during the growing season and 7.5
during the nongrowing season. Based on all of the available data, the instantaneous maximum SAR
standard has been exceeded 96.2 percent of the time during the growing season, and 4.8 percent of the
time during the nongrowing season (Table 5-7). As shown in Figure 5-8, the exceedances during the
growing season occur at the full range of flows except for the highest two percent.
Table 5-7. SAR data and exceedances of the Instantaneous maximum water quality standards for Otter
Time Period
Season
Numeric
Standard
#
Samples
#
Exceeding
%
Exceeding
"All Data" - October 2,
1974 to June 16, 2006
Growing Season
(March 2 to October 31)
< 4.5
764
735
96.2%
Nongrowing Season
(November 1 to March 1)
< 7.5
84
4
4.8%
"Past 5 Years" -
October 1,2001 to
September 30, 2006
Growing Season
(March 2 to October 31)
< 4.5
532
522
98.1%
Nongrowing Season
(November 1 to March 1)
< 7.5
7
0
0%
O Station 06307740 (near mouth)
Inst Max WQ Standard
< .
c/i 4
I I I
0
1 1 1 1
o
o ^ yv A
o° o © °
00 o
t « r O
> §
; i
>
00 o
8
o . o
o °o
o
o
o
§
o
o $
OO/s a o 0 o
~ Y * ~» •
<> * t t
O o 0
O J o ~
O 0 40O ! o O ~
o 0% oo
o
oo
o
1 1
II 1 1 o
o
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Flow Percentile (%)
Figure 5-8. SAR versus flow percentile for Otter Creek near the mouth (USGS Gage 06307740). Growing
season grab samples only.
94
-------
Otter Creek
5.2.3.2 Monthly Average SAR Standard
The monthly average SAR standards for Otter Creek are 3.0 for the growing season and 5.0 for the
nongrowing season. However, the Administrative Rules of Montana (ARM 17.30.670) do not provide
guidance regarding the minimum number of samples needed to calculate "monthly average" values. In
the absence of such guidance, the available data were screened to determine the quantity of available data
on a monthly basis and whether or not the available data represent the full range of flow conditions and
the current time period. This analysis is presented in Appendix F and shows that, in general:
• There are four or more samples per month at only one USGS station - Otter Creek near the mouth
(06307740). Daily data were collected between May 2004 to September 2006.
• There is considerably less data during the non-growing season when compared to the growing
season.
• Given the variability in SAR on a monthly basis (maximum measured change in one month of 6.4
in April 2006), it is logical to conclude that more samples per month would better represent the
"monthly average" than fewer samples per month.
There are limited data to evaluate the monthly average standard using months with 4 or more samples.
The months with 4 or more samples only occurred between 2004 and 2006, which were relatively dry
years. Therefore, for the purposes of providing a comparison of the available data to the monthly average
SAR criteria, all of the available data were compared to the monthly average standard, as well as only
data collected in the past five years. The frequency of exceedances is shown in Table 5-8. The monthly
average standard was almost always exceeded during both the growing season and nongrowing season
(where data were available).
95
-------
Otter Creek
Table 5-8. Average monthly SAR data and exceedances of the average monthly water quality
standards for Otter Creek; daily and grab samples.
Time Period
Sampling
Frequency
Season
Numeric
Standard
# Months
with
Samples
# Months
Exceeding
% Months
Exceeding
"All Data" -
October 2,1974
to September 30,
2006
1 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
125
123
98.40%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
47
47
100%
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
20
20
100%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
0
NA
NA
"Past 5 Years" -
October 1,2001
to September 30,
2006
1 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
27
27
100%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
7
7
100%
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
20
20
100%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
0
NA
NA
96
-------
Otter Creek
5.2.3.3 Nondegradation
Montana's State nondegradation policy requires that when ambient water quality is below 40 percent of
the standard (anti-degradation trigger), up to a 10 percent change in a harmful parameter (such as SC and
SAR) can be allowed without being considered significant (ARM 17.3 0.715 )p. This is illustrated for SC in
Figure 3-7 and Section 3.1.3.3. If deemed significant, an authorization to degrade would be required from
the Montana Department of Environmental Quality.
A monthly comparison of SAR at station 06307740 to the nondegradation threshold is presented in Figure
5-9. The nondegradation threshold (2.0 and 1.2) was exceeded most of the time during all months.
D 25th-75th Percentile ~ Median I Min-Max Average
9.0
8.0
7.0
6.0
< 5.0
-------
Otter Creek
5.3 Metals
Aquatic life and fishery beneficial uses in Otter Creek (headwaters to the mouth) were listed as impaired
because of metals on the Montana 1996 303(d) list (Segment MT42C002-020) (MDEQ, 1996). No
specific metals were listed as the cause of impairment, but the metals listing on the 1996 list applies to
one or more of the following parameters - arsenic, cadmium, chromium, copper, iron, lead, nickel,
selenium, silver, and zinc (Personal communications, Montana DEQ, 2002). Metals were not listed as a
cause of impairment on the 2006 303(d) list.
As described in Appendix B, metals data for the following analysis consist only of USGS, USEPA, and
Montana DEQ data collected between January 1, 1997 and the present. Data were compared to the
Montana total recoverable metals standards, but both "total" and "total recoverable" data were used in the
assessment (see Appendix B). Where no hardness data were available, the average value for Otter Creek
was used to calculate hardness dependant criteria.
Table 5-9 presents a summary of the available metals data obtained in Otter Creek. Samples were
available at two sites: Otter Creek near the mouth (USGS Gage 06307740 and MTDEQ Gage
Y16OTTRC01) (see Figure 5-1). Most of the samples were obtained at USGS Gage 06307740. Between
7 and 28 samples were obtained for each parameter, and data were available between October 16, 2002
and May 16, 2006.
Table 5-9. Summary of metals data in Otter Creek.
Parameter
Count
Average
(M9/L)
Min
(M9/L)
X -1
i!
Period of Record
Arsenic (Total) (pg/L as As)
28
2.04
1.00
6.00
10/16/02-5/16/06
Cadmium (Total) (pg/L as Cd)
27
0.04
0.02
0.07
4/24/03-5/16/06
Chromium (Total) (pg/L as Cr)
25
4.34
0.50
14.00
5/30/03-5/16/06
Copper (Total) (pg/L as Cu)
27
6.81
0.50
20.10
4/24/03-5/16/06
Iron, (Total), (pg/L as Fe)
28
844.54
150.00
2,220
10/16/02-5/16/06
Lead (Total) (pg/L as Pb)
27
0.97
0.07
2.24
4/24/03-5/16/06
Nickel (Total) (pg/L as Ni)
27
6.20
0.01
10.00
4/24/03-5/16/06
Selenium (Total) (pg/L as Se)
27
1.61
0.82
3.00
4/24/03-5/16/06
Silver (Total) (pg/L as Ag)
7
0.54
0.25
1.50
10/16/02-10/02/03
Zinc (Total) (pg/L as Zn)
27
6.89
0.01
20.00
4/24/03-5/16/06
Nine iron samples (32 percent) exceeded the chronic criterion of 1,000 j^ig/L. The date of the exceedance,
the concentration, and the percent increase from the standard are presented in Table 5-10. At most, iron
samples were obtained once per month, and therefore the exceedances of the chronic criterion were based
on single samples rather than an average of several values. No other metals samples exceeded the metals
standards in Otter Creek.
98
-------
Otter Creek
Table 5-10. Summary of the iron exceedances in Otter Creek.
Station
Date of the
Exceedance
Standard
Value
% Increase from the Standard
Y16OTTRC01
April 24, 2003
1,000 |jg/L
2,220 |jg/L
122%
Y16OTTRC01
May 30, 2003
1,000 |jg/L
1,160 |jg/L
16.00%
6307740
April 26, 2004
1,000 |jg/L
1,360 |jg/L
36.00%
6307740
May 24, 2004
1,000 |jg/L
1,030 |jg/L
3.00%
6307740
August 18, 2004
1,000 |jg/L
1,600 |jg/L
60.00%
6307740
April 5, 2005
1,000 |jg/L
1,120 |jg/L
12.00%
6307740
May 16, 2005
1,000 |jg/L
2,030 |jg/L
103%
6307740
August 2, 2005
1,000 |jg/L
2,220 |jg/L
122%
6307740
May 16, 2006
1,000 |jg/L
1,080 |jg/L
8.00%
5.4 Suspended Solids
Aquatic life and fishery beneficial uses in Otter Creek were listed as impaired because of suspended
solids on the Montana 1996 303(d) list (Segment MT42C002-020) (MDEQ, 1996). Beneficial uses were
not evaluated for the 2006 303(d) list. At the time of this report, there are no definitive measurable
indicators available for direct application of Montana's narrative sediment standards to Otter Creek. In the
absence of formal numeric sediment criteria, the following presents an evaluation of a suite of indicators
that have been selected to create a measurable point of reference for Montana's narrative sediment
criteria. Details regarding each of the factors discussed below are provided in Appendix B.
It should be noted that application of Montana's narrative sediment standards is complicated by the
following factors:
• In their natural condition, prairie streams have more fine sediments than streams in the mountains
or foothills regions in Montana (Bramblett et al., 2005; Zelt et al., 1999; USEPA, 2005). Human
activities that increase fine sediment may simply mimic natural conditions; thus differentiating
between natural and human caused in-stream sediment conditions is especially challenging in this
region.
• The harsh environment in this region creates the possibility that natural factors will, on occasion,
impact biota irrespective of human influence (Bramblett et al., 2004). Therefore, it is not always
possible to determine the specific cause of impairment using biological data. This is true when
trying to differentiate between human versus naturally caused biological impairments and also
when trying to determine which pollutant or pollutants (e.g., sediment, metals, salinity, etc.) are
causing the biological impairment.
• Having an understanding of the reference or natural condition is a prerequisite to the application
of Montana's narrative water quality standards for sediment (ARM 17.30.602(19); ARM
17.30.629(2)[d]; ARM 17.30.629(2)[f]). Human influence, though often subtle, is pervasive in the
eastern plains of Montana, and defining reference conditions is difficult. As a result, little
reference data are currently available for defining the natural condition in prairie streams relative
to sediment.
99
-------
Otter Creek
5.4.1 Relative Bed Stability Index
The relative bed stability (RBS) metric is used to determine if a stream has excessive sediment
(Kaufmann et al., 1999). Basically, the metric compares the measured median substrate size in the
streambed to the maximum substrate size carried during bankfull events (see Appendix B). The relative
bed stability index (RBS) was calculated at one site in 2000 as part of the REMAP program (Station
REMAP200). Otter Creek scored -3.55, which indicates that the channel substrates were "poor" with
respect to expected conditions. However, lack of data for other years or segments limit the use of this
information.
5.4.2 HII
Bramblett et al. (2004) developed a human influence index (HII) to systematically compare human
disturbance among multiple watersheds (see Appendix B). Measured HII scores ranged from 235 to 845,
and scores greater than 615 were considered "good" (Tom Johnson, personal communications, January
31, 2005). The HII was calculated at one site in 2000 as part of the REMAP program (Station
REMAP200). Otter Creek scored 384, which indicates that Otter Creek had more human influence when
compared to other REMAP streams.
5.4.3 Riparian and Bank Condition
Bank stability and riparian vegetation assessments were combined to form a riparian and bank condition
(RBC) index (see Appendix B) (USEPA, 2005). The RBC was calculated at one site in 2001 as part of
the REMAP program (Station REMAP200). Otter Creek scored 90, which indicates that bank stability
and vegetation were good with respect to other Great Plains streams. However, lack of data for other
years or segments limit the use of this information.
5.4.4 NRCS Assessment
NRCS inventoried point and linear features for Otter Creek in Powder River and Rosebud counties from
the confluence with Bear Creek to the mouth (the majority of the main stem of Otter Creek). There were
64 identified point features in Otter Creek (Figure 5-10) (NRCS, 2001). Most of the point features were
in-channel features: culverts, bridges, channel plugs, and waterspreading check structures related to the
extensive irrigation along the stream corridor. Four linear features were also found with a total length of
1,700 feet. The largest linear feature was "channelized reach," accounting for about 64 percent of the
linear features. Other linear features included car bodies, floodplain dikes, and riprap rocks. The
presence of channelization, car bodies, and riprap rocks suggests that bank erosion and unstable channel
conditions are present in some places. However, the total length of these features (1,700 feet) is less than
one percent of the total surveyed reach.
Results of the riparian assessment showed that most Otter Creek sites were ranked as "sustainable,"
indicating good channel and riparian conditions. Two reaches were rated "At Risk," primarily due to a
lack of deep, binding root mass and woody vegetation (NRCS, 2002) (Table 5-11). Extensive beaver
activity and grazing in the lower reaches were the primary cause of the lack of woody vegetation.
However, NRCS noted that, "banks were generally stable," and "woody species did not appear to be
critical to the stability of Otter Creek," (NRCS, 2002). None of the reaches were rated as "Not
Sustainable." While streambanks appear to be intact, NRCS noted that the riparian community is capable
of supporting more woody vegetation, and improved grazing practices would help facilitate this
community.
100
-------
Otter Creek
Table 5-11. Results of the NRCS riparian assessment in Otter Creek.
Segment
Incisement
Lateral Cutting
Sediment Balance
Soil
Binding Root
Mass
Woody
Establishment
% Utilization
Riparian/Wetland
Characteristics
Floodplain
Irrigation Impacts
Land Use
Activities
Subtotal
Potential Score
% of Potential
Sustainability
Rating
OC-O-1
R
R
0
o
o
o
4
o
0
NA
NA
o
59
en
00
At Risk
OC-1-1
8
6
4
3
6
6
3
8
6
8
2
20
93
81
Sustainable
OC-3-1
8
6
6
3
6
4
4
8
6
8
8
34
93
98
Sustainable
OC-4-1
8
6
6
3
6
6
4
8
6
8
8
34
93
99
Sustainable
OC-5-1
8
4
4
3
4
4
4
6
6
8
6
30
93
83
Sustainable
OC-6-1
8
6
6
3
4
4
1
4
6
6
4
28
93
80
Sustainable
OC-7-1U
8
6
4
3
2
0
1
0
6
8
4
30
93
68
At Risk
OC-7-1D
8
6
4
3
4
0
1
8
6
6
4
30
93
81
Sustainable
OC-8-1
8
6
4
3
4
4
3
6
6
8
6
34
93
87
Sustainable
OC-9-1
8
4
4
3
4
4
1
4
6
8
4
32
93
78
Sustainable
Sustainable: >75%; At Risk: 50-75%; Not Sustainable: <50%
101
-------
Otter Creek
Powder River
County
~near and Point Features
o
Bridge
•
Channel Plugs
o
Ford
•
Water Spreading System
o
Floodplain Dike
o
Channelized Reach
Q
Culvert
o
Animal Feeding Operation
Rosebud
County
Big Horn
County
5 Miles
Counties
Streams
Figure 5-10. NRCS assessment for Otter Creek.
102
-------
Otter Creek
5.4.5 In-Stream Sediment Concentrations
Total suspended solids (TSS) and suspended sediment concentrations (SSC) were collected at multiple
sites and years in Otter Creek (Table 5-12). Between 1974 and 2006, there were 340 TSS or SSC samples
collected in the stream. As described in Appendix B, TSS and SSC data are combined and used together
in this analysis.
Without an appropriate reference stream, it is impossible to determine if the available TSS and SSC data
are exceeding reference conditions. However, there were no discernable temporal trends in the data
(Figure 5-11). Also, concentrations were relatively similar at all stations and did not indicate localized
sediment loading (Figure 5-12).
Table 5-12. Summary of TSS and SSC data, Otter Creek.
Station
Count
Median
Average
Min
Max
Period of
Record
2584OT01 (Downstream)
1
24
24
24
24
1977-1977
Y16OTTRC01
6
33
44
8
100
2003-2003
6307740
179
78
95
2
536
1974-2006
2579OT01
20
23
26
7
68
1975-1983
24800T01
1
48
48
48
48
1979-1979
6307725
35
24
38
4
132
1977-1981
23800T01
1
6
6
6
6
1979-1979
6307717
30
51
57
1
178
1982-1985
2281OT01
2
11
11
10
12
1978-1978
Y16OTTRC02
5
3
3
1
9
2003-2003
21800T01
5
12
23
1
61
1979-1979
WMTP99-0697
1
21
21
21
21
2002-2002
2081OT01
1
1
1
1
1
1979-1979
6307665 (Upstream)
53
47
79
5
490
1977-1984
All Stations
340
24
34
1
536
1974-2006
Data collected by USGS, NRCS, and MDEQ. Site locations are shown in Figure 5-1.
103
-------
Otter Creek
o o
° %
<& o A 00
0°oOoo0o^<^(> O
o^<8^ O <>o o
fl.O O.O
^ w^VoN4 o o
o
<>0 o
O O O o Q o
A ° O
o° $ O O o
Oo
O %$
O 00
-------
Otter Creek
5.4.6 Sediment Source Identification and Load Quantification
As described in the March 2003 Phase I report (MDEQ, 2003), soils in the Otter Creek watershed are
naturally highly erodible, with slow to very slow infiltration rates. These attributes, in combination with
semiarid conditions, flashy rain events, and sparse ground cover, result in naturally high sediment erosion.
Buttes and badlands occur throughout the landscape, and saline or sodic soils limit plant growth in several
areas. NRCS (2002) reported that
The majority of the Tongue River watershed is mapped as yielding 0.2 to 0.5 acre-
feet/mile2/year of sediment. Using an average bulk density of sixty-pounds/cubic foot,
these volumes would be equivalent to 0.4 to 1.0 tons/acre/year. Juvan estimated percent
contribution of erosion source was forty-percent gully and sixty percent sheet erosion
within most of the Tongue River-Montana watershed (Juvan, undated).
Cattle are currently the predominant agricultural resource in the watershed, having 1.37 cattle per 100
acres of land in Powder River County, Montana (USDA, 2002). It is well documented that cattle have the
potential to impact the landscape, if not managed properly (Meehan, 1991). In the uplands, decreased
ground cover, increased erosion, and the promotion of invasive species can occur from overgrazing. In
the lowlands and stream valleys, cattle grazing can have direct impacts to the stream and riparian area
(destabilized stream banks, lack of riparian cover, habitat degradation) (Meehan, 1991). Cattle are grazed
in the lowlands in Otter Creek from December to March, and usually moved to upland areas when the
ground thaws in the spring (R. Iron, personal communications, February 25, 2005).
Irrigated agriculture is another potential source of sediment. Irrigated fields in Otter Creek generally
consist of hay and alfalfa, and are plowed and reseeded every 5 to 10 years (or as necessary due to disease
or crop failure) (R. Iron and C. Hillard, personal communications, February 25, 2005). When plowing
does occur, it occurs in the spring, and fields are generally reseeded immediately. Overall, there is a
small window of time every 5 to 10 years when the ground is in a bare, disturbed state, leaving little
opportunity for excessive erosion from fields. Furthermore, irrigated fields have denser groundcover than
what would otherwise be present, and act as a sediment buffer to the stream. As evidenced by the NRCS
survey (NRCS, 2002), most sediment contributions from agriculture are caused by small, localized
disturbances, such as headcuts and cattle trampling.
Although fires are considered a natural phenomenon, they can result in soil erosion, soil nutrient loss,
stream channel effects, and water yield effects (Emmerich and Cox, 1994; Marcos et al., 2000; Belillas
and Roda, 1993). A wildfire has the potential to affect the characteristics of soils by reducing the soil
aggregate stability, reducing permeability, increasing runoff and erosion, and reducing organic
matter/nutrient status (USGS, 2003). These combined effects can cause the runoff following a storm
event to increase significantly, increasing the overland flow available to initiate soil erosion, as either
sheet or rill erosion. The potential for erosion increases with slope and burn severity. In 2000, 10 percent
of the Otter Creek watershed burned, mostly in upland areas of the Custer National Forest. The fires have
likely increased sediment delivery to streams over the past six years, especially during intense summer
storms (USGS, 2003).
Upland sediment loads were estimated using soil survey data, GIS, and the Universal Soil Loss Equation
(USLE). Details of the analysis for all watersheds are described in Appendix B. In the Otter Creek
watershed, there was very little difference between the existing and "natural" upland sediment delivery.
Natural conditions are defined as "no human alterations, resulting in no active agricultural land and
increased total vegetative ground cover." USLE calculations showed that there is only a 0.31 percent
increase in sediment load over naturally occurring conditions (19,496 versus 19,558 tons of sediment per
105
-------
Otter Creek
year). This suggests that human management has not had a major effect on upland sources in the Otter
Creek watershed. It should be noted that this analysis does not take into account streambank erosion or
riparian degradation.
As evidenced by the NRCS riparian assessment, cattle have impacted riparian areas and stream banks in
several areas (NRCS, 2002). The extent of this effect is unknown, although NRCS attributed lack of deep
binding root mass and woody vegetation at two segments to grazing impacts (NRCS, 2002).
To estimate bank erosion in Otter Creek, a simple analysis was performed using literature values and
conservative assumptions. It was assumed that stream banks are eroding an average of 0.10 feet per year,
and have a height of one foot (adapted from Rosgen, 1996). The 2001 NRCS riparian assessment found
59.9 of 76.6 assessed miles to be "sustainable." It is conservatively assumed that bank erosion occurs
along the entire length of both banks of the total length rated "at risk" (33.4 miles), and that all of that
erosion is human caused (note: this assumption is a gross over estimate presented as a "worst case"
analysis). Assuming an average bulk density of 60 pounds per cubic feet, this equates to an average
sediment load of 529 tons of sediment per year from bank erosion. From the USLE analysis, it is
estimated that 19,500 tons of sediment per year are contributed to the stream from upland sources.
Therefore, under this worst-case scenario, streambank erosion is less than three percent of the total
sediment load delivered to the stream. This analysis shows that streambank erosion is relatively small
compared to the total amount of sediment contributed from upland erosion.
106
-------
Pumpkin Creek
6.0 PUMPKIN CREEK
Pumpkin Creek flows 171 miles from its origin in
Powder River County, Montana to the confluence
with the Tongue River near the T&Y irrigation
dam (Figure 6-1). The total watershed covers
roughly 707 square miles. The agriculture, warm-
water fishery and aquatic life beneficial uses were
listed as impaired by flow alterations,
salinity/TDS/chlorides, and thermal modifications
on the Montana 1996 303(d) list (Segment
MT42C002-060) (MDEQ, 1996). The basis for
the 1996 listings is unknown. Beneficial uses
were not evaluated for the 2006 list because of
insufficient credible data.
This analysis specifically addresses the listed Pumpkin Creek near the mouth
pollutants and impaired beneficial uses from the (Photo by Tetra Tech, inc.)
1996 303(d) list (i.e., impairments to the
agriculture, warm-water fishery, and aquatic life beneficial uses associated with salinity/TDS/chlorides
and thermal modifications). Sodium adsorption ratio (SAR) is also addressed given its potential
importance related to future Coal Bed Methane development in the watershed. The purpose of this
analysis was to determine if Montana's water quality standards are currently exceeded in Pumpkin Creek
and, if so. provide insight into the potential cause (i.e., natural versus anthropogenic).
The remainder of this section provides a summary and evaluation of the available data, and comparison to
the applicable Montana water quality standards one pollutant at a time. Biological data for Pumpkin
Creek are discussed in Appendix I, and Appendix H provides a general overview of the hydrologic
characteristics of the Pumpkin Creek watershed.
107
-------
Pumpkin Creek
6.1 Salinity
Specific conductance (SC) data for Pumpkin Creek are available from 1974 to the present, and include
both grab and continuous samples. Grab samples are available from 14 stations in Pumpkin Creek, dating
from 1974 to 2006, and collected by multiple governmental agencies and private organizations (see
Figure 6-1). USGS also collected continuous flow and salinity data at Pumpkin Creek near the mouth
(06308400) from May 25, 2004 to the present. The available stations with more than 10 grab samples are
summarized in Table 6-1 and the sample site locations are shown in Figure 6-1. Where summary statistics
are provided in the following sections (i.e., mean, median, maximum, minimum), only salinity grab
samples are used so that the continuous data do not bias the re suits.q
Table 6-1. Specific conductance (SC) data for the mainstem Pumpkin Creek.1
Station ID
Station Name
Aqency
River Mile
n
Period of Record
06308160
Pumpkin Creek near Loesch, MT
USGS
103.91
28
1975-1979
06308400
Pumpkin Creek near Miles City, MT
USGS
7.67
380
1975-1985; 2003-2006
3483PU01
Pumpkin Creek near the mouth
MDEQ
6.36
24
1974-1979
Stations with 10 or more samples are included in this table.
q Continuous salinity data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years
of record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
108
-------
Pumpkin Creek
PC-4-1
Y16PMKC4'
455136TO54O10O1
r-»S30S19Q
[983PU01
* 4547 3$1GS430701
06308160
45424610!
• 06308080
• 452423'
503001
Surface Water Quality Monitoring Stations
Coster
County
Powder River
Countv
MONTANA
WYOMING
Y16PUMPC10
461450105444601
Y16PMPKC01
PC-8-1
Streams
Counties
j Pumpkin Creek Watershed
3483 PU011
06308400
PC-7-1 j
Y16PMPKC03
0 2-5 5 10 Miles
1 i i i I i i l I
Figure 6-1. Surface water quality monitoring stations on the main stem of Pumpkin Creek.
109
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Pumpkin Creek
6.1.1 Spatial Characterization
The USGS sample stations listed in Table 6-1 have been used to provide a general spatial characterization
of SC in the Pumpkin Creek. As shown in Figure 6-2 and Table 6-2, specific conductance decreases in a
downstream direction, from a mean of 5,146 (iS/cm near Loesch, Montana to 2,600 (iS/cm near the
mouth.
- 75th Ftercentile
- 25th Ftercentile
Median
-Average
- Max
¦ Min
E
.o
-------
Pumpkin Creek
6.1.2 Relationship between Specific Conductance and Discharge
The relationship between discharge and SC was evaluated at two stations in Pumpkin Creek - Pumpkin
Creek near the mouth (USGS Gage 06308400) and Pumpkin Creek near Loesch, Montana (USGS gage
06308160). There is a weak inverse relationship between flow and SC at both stations.
Near Loesch, MT (06308160)
0.01 0.1 1 10 100 1000 10000
Flow (cfs)
Near the Mouth (06308400)
Flow (cfs)
Figure 6-3. Relationship between flow and SC at selected USGS stations on the mainstem of Pumpkin
Creek. Entire period of record is shown; grab samples only.
6.1.3 Comparison to Applicable Standards
The following sections compare the available observed salinity data in Pumpkin Creek to Montana's
numeric salinity standards. Since there is no guidance in the Administrative Rules of Montana (ARM), it
is assumed that the "electrical conductivity" standard can be applied to "specific conductance" (SC) data,
which is simply electrical conductivity that has been corrected to a temperature of 25° Celsius. Both the
instantaneous maximum and monthly average salinity standards for tributaries to the Tongue River (i.e.,
Pumpkin Creek) are 500 (iS/cm. The standards do not vary per season.
111
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Pumpkin Creek
6.1.3.1 Instantaneous Maximum Salinity Standard
The instantaneous maximum salinity criterion for Pumpkin Creek is 500 (iS/cm. Based on all of the
available data in the main stem of Pumpkin Creek, the instantaneous maximum salinity standard has been
exceeded more than 88 percent of the time. As shown in Figure 6-4, exceedances have occurred under all
flow conditions.
Table 6-3. SC data and exceedances of the instantaneous maximum water quality standards for
Time Period
Season
Numeric
Standard
#
Samples
#
Exceeding
%
Exceeding
"All Data" - January 1,
1974 to September 30,
2006
Growing Season
(March 2 to October 31)
< 500 pS/cm
431
384
89.1%
Nongrowing Season
(November 1 to March 1)
< 500 pS/cm
35
30
85.7%
"Past 5 Years" -
October 1,2001 to
September 30, 2006
Growing Season
(March 2 to October 31)
< 500 pS/cm
332
295
88.9%
Nongrowing Season
(November 1 to March 1)
< 500 pS/cm
5
5
100%
O Station 06308400 (near mouth)
Water Quality Standard
9,000
8,000
7,000
6,000
E
5,000
3
o
4,000
in
3,000
2,000
1,000
0
0%
~~ ! ! !
0
I I I I I
!
! ! !~ ! O
i i i i i
1
~ * ~~~ ~ r
o
o
o
0% o
? ~ ~ \*o
I
I
I
« °oo 0
~ ~ Ot ~ ~~ o ~
o - - [¦ L.. -O L lO- -o| ^O0- - -og-
0
0
O 0
I
I
. °o 1 ~
10% 20% 30% 40% 50% 60%
Flow Percentile (%)
70%
80%
90%
100%
Figure 6-4.
Specific conductance versus flow percentile for Pumpkin Creek near the mouth (USGS Gage
06308400). Entire period of record is shown; grab samples only.
112
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Pumpkin Creek
6.1.3.2 Monthly Average Salinity Standard
The monthly average salinity standard for Pumpkin Creek is 500 (iS/cm. However, the Administrative
Rules of Montana (ARM 17.30.670) do not provide guidance regarding the minimum number of samples
needed to calculate "monthly average" values. In the absence of such guidance, the available data were
screened to determine the quantity of available data on a monthly basis and whether or not the available
data represent the full range of flow conditions and the current time period. This analysis is presented in
Appendix E and shows that, in general:
• There are four or more samples per month at only one USGS station - Pumpkin Creek near the
mouth (06308400). Daily data were collected between May 2004 and September 2006.
• There is considerably less data during the non-growing season when compared to the growing
season.
• Given the variability in SC on a monthly basis (maximum measured change in one month of
2,688 (iS/cm near the mouth, May 2006), it is logical to conclude that more samples per month
would better represent the "monthly average" than fewer samples per month.
For the purposes of providing a comparison of the available data to the monthly average SC criteria, all of
the available data were compared to the monthly average standard, as well as only data collected in the
past five years. Only months with 4 or more samples were used in the analysis. The frequency of
exceedances is shown in Table 6-4. The monthly average standard was always exceeded during the
growing season. No data were available for the nongrowing season.
Table 6-4. Average monthly SC data and exceedances of the average monthly water quality standards
for Pumpkin Creek assuming > four daily and/or g
rab samples
per month.
Time Period
Sampling
Frequency
Season
Numeric
Standard
# Months
with
Samples
# Months
Exceeding
% Months
Exceeding
"All Data" -
January 1,1974
to September 30,
2006
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 500
pS/cm
15
15
100%
Nongrowing
Season
(November 1 to
March 1)
< 500
pS/cm
0
NA
NA
"Past 5 Years" -
October 1,2001
to September 30,
2006
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 500
pS/cm
15
15
100%
Nongrowing
Season
(November 1 to
March 1)
< 500
pS/cm
0
NA
NA
113
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Pumpkin Creek
6.1.3.3 Nondegradation
Montana's State nondegradation policy requires that when ambient water quality is below 40 percent of
the standard (anti-degradation trigger), up to a 10 percent change in a harmful parameter (such as SC and
SAR) can be allowed without being considered significant (ARM 17.30.715)r. This is illustrated for SC in
Figure 3-7, Section 3.1.3.3. If deemed significant, an authorization to degrade would be required from the
Montana Department of Environmental Quality.
A monthly comparison of SC at station 06308400 to the nondegradation threshold is presented in Figure
6-5. The nondegradation threshold (200 (iS/cm) was exceeded most of the time for most months, with the
exception of February and March where the threshold was exceeded approximately 25 to 40 percent of
the time.
I 25th-75th Ftercentile
~ Median
| Min-Max
Average
-------
Pumpkin Creek
6.1.4 Sources of Salinity and Their Influence on Pumpkin Creek
As described above, exceedances of Montana's salinity standards have been observed in Pumpkin Creek.
However, it is unclear if the observed exceedances are due to natural or anthropogenic sources (or a
combination of both).
A modeling analysis similar to that which was described in Section 3.1.4 was conducted to estimate the
salinity levels that may have occurred in the absence of human influence (see Appendix J). Mean SC is
slightly higher under the simulated natural condition when compared to the simulated existing condition
(i.e., a mean of 1,200 (iS/cm versus a mean of 1,103 (iS/cm). This is thought to be a result of the way in
which the model simulates impervious surfaces under the existing condition (i.e., there are areas of
impervious surfaces associated with roadways that contribute lower SC water) and suggests that the
observed exceedances are largely due to natural causes. See the Modeling Report for details and a
discussion of uncertainty.
6.2 SAR
Sodium adsorption ratio (SAR) data for Pumpkin Creek are available from 1974 to the present, and
include both grab and continuous samples. Grab samples are available from 8 stations in the main stem
of Pumpkin Creek, and were collected by multiple governmental agencies and private organizations. No
continuous SAR data have been collected in Pumpkin Creek. Stations with 10 or more SAR grab samples
are summarized in Table 6-5, and the sample sites are shown in Figure 6-1. Where summary statistics are
provided in the following sections (i.e., mean, median, maximum, minimum), only SAR grab samples are
used so that the continuous data do not skew the results.8
Table 6-5. SAR data for the mainstem Pumpkin Creek.1
Station ID
Station Name
Agency
River Mile
n
Period of Record
06308160
Pumpkin Creek near Loesch MT
USGS
103.91
28
1975-1979
06308400
Pumpkin Creek near Miles City MT
USGS
7.67
82
1975-1985; 2003-2006
3483PU01
Pumpkin Creek
MDEQ
6.36
20
1974-1979
Stations with 10 or more samples are included in this table.
6.2.1 Spatial Characterization
The USGS sample stations in Table 6-5 have been used to provide a general spatial characterization of
SAR the Pumpkin Creek. As shown in Figure 6-6 and Table 6-6, SAR is relatively similar between the
upstream and downstream sites, although maximum values are higher at the downstream stations.
s Continuous SAR data have been collected for specific discrete periods of time, whereas the grab samples are spread out over multiple years of
record. Including the numerous continuous data points in the summary statistics would bias the results to those periods in which continuous
monitoring was conducted.
115
-------
Pumpkin Creek
Figure 6-6.
70 60 50 40
River Mile (rriles from the nrouth)
SAR statistics for stations with 10 or more samples in the mainstem Pumpkin Creek. The
entire period of record is shown for each station; grab samples only.
Table 6-6. SAR statistics for various time periods, flows, and stations on the mainstem Pumpkin
Station
Statistic
Full Period of
Record
Last Five
Years2
Low
Flow3
High
Flow3
Average
Flow
Pumpkin Creek near Loesch, MT
(USGS Gage 06308160)
n
28
0
7
7
14
Min
2
NA
8.37
2.14
6.54
Max
10
NA
10.01
7.35
9.09
Mean
8
NA
9.52
5.64
7.81
Median
8
NA
9.69
5.81
7.74
Pumpkin Creek near Miles City, MT
(USGS Gage 06308400)
n
82
27
21
21
40
Min
0.25
0.25
0.25
0.63
0.34
Max
24.75
15.00
24.75
12.58
15.30
Mean
7.87
6.01
10.44
5.63
7.70
Median
7.45
6.66
10.16
5.40
8.56
Pumpkin Creek near the Mouth
(MDEQ Gage 3483PU01)
n
20
0
NA
NA
NA
Min
1
NA
NA
NA
NA
Max
21
NA
NA
NA
NA
Mean
9
NA
NA
NA
NA
Median
9
NA
NA
NA
NA
"Last 5 Years" is defined as data collected between October 1, 2001 and September 30, 2006.
3 Low flow, average flow, and high flow were determined from paired flow and SAR data at the representative station. Low flow is defined as the lowest
25 percent of flows (0-25th percentile); average flow as the middle 50 percent of flows (25th-75th percentile); high flow as the highest 25 percent of flows
(75 -100th percentile).
116
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Pumpkin Creek
6.2.2 Relationship between SAR and Discharge
The relationship between discharge and SAR was evaluated at two stations in Pumpkin Creek - Pumpkin
Creek near the mouth (USGS Gage 06308400) and Pumpkin Creek near Loesch, Montana (USGS gage
06308160). There was no apparent relationship near Loesch, Montana, while there is a weak inverse
relationship between discharge and SAR near the mouth.
Near Loesch, MT (06308160)
y = 13.028x
R2 = 0.0574
1 10 100 1000 10000
Flow (cfs)
Near the Mouth (06308400)
30
25
20
Ql
< 15
w
10
5
0
0.01 0.1 1 10 100 1000 10000
Flow (cfs)
Figure 6-7. Relationship between flow and SAR at selected USGS stations on the mainstem of Pumpkin
Creek. Entire period of record is shown; grab samples only.
y = 9.1818x"01422
R2 = 0.3754
_ J OO L _
v o
O ® o
o
e
* °°
%
. ~ o
^ -I- -
o0o o
117
-------
Pumpkin Creek
6.2.3 Comparison to Applicable Standards
The following sections compare the available observed SAR data in Pumpkin Creek to Montana's
numeric SAR standards. The standards are seasonal, with separate criteria for the growing season (March
2 - October 31) and non-growing season (November 1 - March 1) and include monthly average criteria
as well as instantaneous maximum criteria.
6.2.3.1 Instantaneous Maximum SAR Standard
The instantaneous maximum SAR criteria for Pumpkin Creek are 4.5 during the growing season and 7.5
during the nongrowing season. Based on all of the available data, the instantaneous maximum SAR
standard was exceeded 81.7 percent of the time during the growing season, and 54.9 percent of the time
during the nongrowing season (Table 6-7). The frequency of exceedance is less for the last five years.
The reason for the difference is unknown, but may be due to limited data from the recent time period. As
shown in Figure 6-8, the exceedances during the growing season occur at the full range of flows except
for the highest two percent.
Table 6-7. SAR data and exceedances of the Instantaneous maximum water quality standards for
Pumpkin Creek; daily and grab sam
pies.
Time Period
Season
Numeric
Standard
#
Samples
#
Exceeding
%
Exceeding
"All Data" - October 2,
1974 to June 16, 2006
Growing Season
(March 2 to October 31)
<4.5
120
98
81.7%
Nongrowing Season
(November 1 to March 1)
< 7.5
31
17
54.9%
"Past 5 Years" -
October 1, 2001 to June
21,2006
Growing Season
(March 2 to October 31)
<4.5
33
22
66.7%
Nongrowing Season
(November 1 to March 1)
< 7.5
3
1
33.3%
20
18
16
14
12
OT 10
8
6
4
2
0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Flow Percentile (%)
Figure 6-8. SAR versus flow percentile for Pumpkin Creek near the mouth (USGS Gage 06308400).
Growing season grab samples only, entire period of record.
O Station 06308400 (near mouth) Water Quality Standard
118
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Pumpkin Creek
6.2.3.2 Monthly Average SAR Standard
The monthly average SAR standards for Pumpkin Creek are 3.0 for the growing season and 5.0 for the
nongrowing season. However, the Administrative Rules of Montana (ARM 17.30.670) do not provide
guidance regarding the minimum number of samples needed to calculate "monthly average" values. In
the absence of such guidance, the available data were screened to determine the quantity of available data
on a monthly basis and whether or not the available data represent the full range of flow conditions and
the current time period. This analysis is presented in Appendix F and shows that, in general:
• There are few data at this gage. Only four months had four or more SAR samples.
• There is considerably less data during the non-growing season when compared to the growing
season.
• Given the variability in SAR on a monthly basis (maximum measured change in one month of 6.4
in April 2006), it is logical to conclude that more samples per month would better represent the
"monthly average" than fewer samples per month.
There are limited data to evaluate the monthly average standard using months with 4 or more samples.
Therefore, for the purposes of providing a comparison of the available data to the monthly average SAR
criteria, all of the available data were compared to the monthly average standard, as well as only data
collected in the past five years. The frequency of exceedances is shown in Table 6-8. The monthly
average standard has been exceeded greater than 83 percent of the time during both the growing season
and nongrowing season (where data were available).
119
-------
Pumpkin Creek
Table 6-8. Average monthly SAR data and exceedances of the average monthly water quality
standards for Pumpkin Creek near the mouth - USGS Gage 06308400; daily and grab samples.
Time Period
Sampling
Frequency
Season
Numeric
Standard
# Months
with
Samples
# Months
Exceeding
% Months
Exceeding
"All Data" -
October 15,
1975 to June
21,2006
1 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
50
49
98.00%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
18
15
83.33%
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
4
4
100%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
0
NA
NA
"Past 5 Years"
- October 1,
2001 to June
21,2006
1 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
14
13
92.86%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
3
3
100%
4 or more
samples per
month
Growing Season
(March 2 to
October 31)
< 3.0
4
4
100%
Nongrowing
Season
(November 1 to
March 1)
< 5.0
0
NA
NA
120
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Pumpkin Creek
6.2.3.3 Nondegradation
Montana's State nondegradation policy requires that when ambient water quality is below 40 percent of
the standard (anti-degradation trigger), up to a 10 percent change in a harmful parameter (such as SC and
SAR) can be allowed without being considered significant (ARM 17.30.715)'. This is illustrated for SC in
Figure 3-7 and Section 3.1.3.3. If deemed significant, an authorization to degrade would be required from
the Montana Department of Environmental Quality.
A monthly comparison of SAR at station 06307600 to the nondegradation threshold is presented in Figure
6-9. The nondegradation threshold (2.0 and 1.2) has been exceeded most of the time during all months.
D 25th-75th Ftercentile ~ Median I Min-Max Average
30.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 6-9. SAR data and nondegradation thresholds for Pumpkin Creek (near the mouth). Entire
period of record is shown; grab samples only.
1 Montana adopted its State nondegradation policy for the parameters of Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) in
March 2006. In June 2006, Montana submitted this change in its regulations to EPA for approval for federal Clean Water Act purposes. EPA has
not yet acted on Montana's submission.
121
-------
Pumpkin Creek
6.2.4 Sources of SAR and Their Influence on Pumpkin Creek
As described above, exceedances of Montana's salinity standards have been observed in Pumpkin Creek.
However, it is unclear if the observed exceedances are due to natural or anthropogenic sources (or a
combination of both).
As a result of insufficient data, it was not possible to quantitatively calibrate and or evaluate model
performance for SAR in Pumpkin Creek. Therefore, no modeling analysis has been conducted (see the
Modeling Report).
6.3 Thermal Modifications
Pumpkin Creek (Class C-3) was listed as impaired for thermal modifications on the 1996 303(d) list
(Segment MT42C002-060) (MDEQ, 1996). Beneficial uses for Pumpkin Creek were not evaluated for
the 2006 list. This section presents an updated evaluation of Pumpkin Creek relative to thermal
modifications. Montana Class C-3 water quality standards state that, for waters classified as B-3 and C-3,
the maximum allowable increase over naturally occurring temperature (if the naturally occurring
temperature is less than 77° Fahrenheit) is 3° (F) and the rate of change cannot exceed 2°F per hour. If
the natural occurring temperature is greater than 79.5° F, the maximum allowable increase is 0.5° F,"
(ARM 17.30.625(e), ARM 17.30.629(e)). Narrative standards also apply to thermal modifications (ARM
17.30.637).
The temperature analysis is divided into two sections: (1) analysis of measured data to provide an
understanding of in-stream water temperatures, and; (2) comparison of Pumpkin Creek temperatures to
similar Great Plains streams.
6.3.1 Measured Stream Temperature
Data were compiled from various sources to characterize water temperatures in Pumpkin Creek. Grab
samples (collected at one day and time) are available at various sites from 1974 to 2006, and data are
summarized in Table 6-9 and Figure 6-10. The data indicate that stream temperatures are dynamic
throughout the stream, ranging from 32 °F to 85.1 degrees °F. There was no indication of temporal or
spatial trends in the data.
122
-------
Pumpkin Creek
Table 6-9. Summary of surface water temperature data (grab samples) in Pumpki
n Creek (°F).
Station ID
Count
Average
Min
Max
Period of
Record
Y16PUMPC10 (Downstream)
2
67.2
59.2
75.2
2001-2001
PC-8-1
1
61.3
61.3
61.3
2002-2002
3483PU01
26
59.0
32.0
83.8
1974-1979
06308400
87
51.8
32.0
85.1
1975-2006
REMAP_165_1
3
60.3
53.2
69.6
1999-2000
Y16PMPKC03
3
62.6
38.7
75.2
2005-2005
PC-7-1
1
62.8
62.8
62.8
2002-2002
PC-6-1
1
64.9
64.9
64.9
2002-2002
06308190
9
49.3
32.0
80.6
1975-1977
2983PU01
2
54.5
53.6
55.4
1974-1975
PC-1-2
1
54.0
54.0
54.0
2002-2002
06308160
28
51.7
32.0
78.8
1975-1979
452423105503001 (Upstream)
2
51.8
41.0
62.6
1978-1978
All Sites
166
58.8
32.0
85.1
1974-2005
Data collected by USGS, NRCS, and MDEQ. Site locations are shown in Figure 6-1.
25th-75th Percentile
~ iredian
Q.
E
100
90
80
70
60
50
40
30
| Min-Max
6308160 887 PC-1-2 6308190 PC-6-1 PC-7-1 REMAP165 6308400 Y16FMPKC01 PC-8-1
Figure 6-10. Stream temperatures in Pumpkin Creek (all stations, grab samples).
123
-------
Pumpkin Creek
In 2003, temperature data loggers were deployed at
two sites in Pumpkin Creek. The data loggers
recorded hourly stream temperatures between April
24, 2003 and October 1, 2003.
• Site Y16PMKC02 - Pumpkin Creek
approximately 5 miles upstream of the
mouth to a deep pool (in an area with
cottonwood trees and other large woody
vegetation). The data logger at this site was
activated on April 24, 2003 and removed on
September 30, 2003.
• Site Y16PMKC01 - Pumpkin Creek
approximately 0.5 river miles upstream
from the mouth in a deep pool near the
Tongue River Road Bridge (near an area
with poor riparian cover, lack of shade).
The data logger at this site was activated on
April 24, 2003 and removed on October 1,
2003.
Data from the upstream data logger (Y16PMKC02)
show that water temperatures between April 24 and
August 10 ranged from 46 to 75 degrees F, with an
average temperature of 66 degrees F (Figure 6-11).
Pumpkin Creek dried up at this site on August 10,
and did not have water for the remainder of the
season.
Pumpkin Creek monitoring site Y16PMKC02
(Photo by Tetra Tech, Inc.)
Temperatures at the downstream site showed more
variation, and suggest a pattern of daily warming Pumpkin Creek monitoring site Y16PMKC01
, , , , ^ , • . , (Photo by Tetra Tech, Inc.)
and cooling closely matching air temperatures.
This data probe was also placed in a deep pool;
however, the pool did not dry up during the 2003 season. Monthly site visits found that after April,
there was no flow at this site, and by August, the pool was almost dry.
124
-------
Pumpkin Creek
6.3.2 Comparison to Other Streams
Temperature standards for Montana are both numeric and narrative, and generally suggest that stream
temperatures should strive towards a reference condition. However, there is little information about
natural, or minimally impacted, stream temperatures in prairie streams. Because of this, stream
temperatures in Pumpkin Creek were compared to other prairie streams in southeast Montana and
northeast Wyoming to better understand regional patterns and trends.
In 2003, six temperature data loggers were deployed in tributaries to the Tongue River watershed.
• Pumpkin Creek near the Tongue River Road Bridge (Y16PMKC01).
• Pumpkin Creek five miles upstream from the mouth (Y16PMKC02).
• Hanging Woman Creek near the mouth (06307600)
• Hanging Woman Creek near Horse Creek (06307570)
• Otter Creek near the mouth (06307740)
• Otter Creek near Taylor Creek (451732106085001)
Two of the data loggers - Hanging Woman Creek near Horse Creek and Otter Creek near the mouth -
were lost due to flood events or theft. Data from the four remaining temperature loggers are shown in
Figure 6-12. The data suggest that temperatures near the mouth of Pumpkin Creek are similar to stream
temperatures in Hanging Woman Creek near the mouth. On average, Pumpkin Creek near the mouth had
the highest stream temperatures of the four data loggers, having one-degree higher temperatures than
Hanging Woman Creek. However, this is somewhat expected, as flows and elevations are higher in
Hanging Woman Creek, resulting in naturally lower stream temperatures.
125
-------
Pumpkin Creek
Hanging Wbman Creek (06307600) Otter Creek (451732106085001) Purrpkin Creek (Y16PMKC02) Purrpkin Creek (Y16FMKC01)
80 n
40
35
30 J , , , , , r
Apr May Jun Jul Aug Sep Oct
Figure 6-12. Average daily temperature at four sites in the Tongue River watershed, April-October, 2003.
Grab sample water temperatures in Pumpkin Creek at station 06308400 were compared to other Great
Plains streams to obtain an understanding of regional stream temperatures. Data for station 06308400
were not available from 1986 to 2004 so the comparison covered the period from 1974 to 1985. Data
from Appendix K shows that Pumpkin Creek generally has similar temperatures to other Great Plains
streams, and had the fourth lowest median stream temperature (46 degrees F) (Figure 6-13).
126
-------
100
90
80
70
60
50
40
30
Figure 6-13. Comparison of water temperature data for 16 Great Plains streams in southeast Montana and northeast Wyoming, 1974-1985.
~ 25th-75th Percentile ~median | Min-Max
Squirrel Rosebud L. Donkey Cherry Armells Sarpy Hanging Beaver O'fallon Pumpkin Otter Cr. Salt Cr. Rosebud Antelope L. Rosebud Belle
Cr. Cr. - Thunder Cr. Cr. Cr. Cr. Woman Cr. Cr. Creek Cr. - Cr. Powder Cr. - Fourche
Kirby Cr. Cr. Colstrip R. @ mouth R.
Dry Cr.
Small Watershed Size Large Watershed Size
-------
Pumpkin Creek
6.3.3 Temperature Sources
The following sections document potential indirect human impacts to stream temperature in Pumpkin
Creek.
6.3.3.1 Flow
USGS maintained a continuous flow gage between 1972 and 1985 on Pumpkin Creek near the mouth
(USGS gage 06308400). The gage was then reinstated in 2004. Flows in the creek are very low, with a
median daily flow of 0.04 cubic feet per second and a mean annual discharge of 10,324 acre-feet per year.
The stream is dynamic in that flows rapidly increase and decrease in response to storm events and
snowmelt, resulting in steep "spikes" in the hydrograph (see Appendix H). Low flows occur in the
summer, where flows are generally less than one cubic feet per second. In a shallow, low velocity, low
volume, highly sinuous prairie stream like Pumpkin Creek, water temperatures are expected to be
variable, with high water temperatures in the summer months. Stream temperatures are also expected to
have large daily fluctuations that correspond to diurnal air temperatures fluctuations.
However, irrigation is prevalent throughout Pumpkin Creek, and may result in less water volume and
longer travel times (see Section 3.5.2 of the modeling report). Flow alterations may, therefore, indirectly
increase stream temperatures by reducing the amount of water in the stream, and also cause more
variability in stream temperature (higher maximum and lower minimum temperatures). Due to a poor fit
between predicted and observed discharge in Pumpkin Creek with the Tongue River LSPC model, no
analysis of the magnitude of human-caused flow alteration has been conducted (see Modeling Report).
6.3.3.2 Habitat Alterations
Habitat alterations are another indirect source that can increase stream temperature. Riparian vegetation,
and particularly large woody vegetation, provides shade to a stream, and if removed, can result in
increased stream temperatures (Beschta, 1997; Poole and Berman, 2001; Li et al., 1994). Riparian
vegetation along Pumpkin Creek was evaluated by NRCS in 2001 and 2002 from the confluence with
Little Pumpkin Creek to the mouth (NRCS, 2001; NRCS, 2002). Scores for each of the eight segments
are shown in Table 6-10, and stream segments are shown in Figure 6-14. NRCS found that (NRCS,
2002):
The banks along the entire creek were stable and well vegetated with prairie cordgrass,
and several species of sedges, rushes and bulrushes. Emergent vegetation was prevalent
within the channel bottom. It was not until the lower reaches, six to eight, that Kentucky
bluegrass became a dominant component in the riparian vegetation. Even then, the
banks appeared stable. Boxelder was evident on all of the upper reaches, but dropped
out of the plant community in the lower reaches, as did all of the other woody species. In
the upper five reaches, boxelder maple, currant, wild rose and western snowberry were
common. Chokecherry was found scattered throughout the upper drainage. In the lower
three reaches, the woody component dropped out completely.
The potential for a boxelder maple and/or green ash canopy on Pumpkin Creek exists
throughout nearly the entire stream but may be limited in the lower reaches due to higher
salinity levels associated with the Lake Glendive sediments. The potential for an
understory of shrubs including snowberry, wild rose and chokecherry existed as well.
Past and present grazing practices have probably limited the extent and diversity of these
species in most of the reaches. The amount of Kentucky bluegrass in the lower reaches is
128
-------
Pumpkin Creek
K
n .
to
¦*Sr.
MOM
Lack of large woody vegetation and shade at Pumpkin
Creek segment 6. (Photo by NRCS).
a cause for concern for the long-term
stability of the banks since it has a
shallow, relatively weak root system that
offers little protection during high flow
events.
Five of the eight reaches assessed on
Pumpkin Creek were rated in the
'Sustainable' category. The lower three
reaches, occurring on the lacustrine or
glacial lake deposits, were found to be in
the 'At Risk' categon> mainly due to the
lack of deep-rooted species in the riparian
zone. These are the reaches that more
frequently have flowing water.
Overall, the evidence suggests that the lower three
reaches of Pumpkin Creek (Reaches 6, 7, and 8 in Figure 6-14) have degraded riparian habitat, "mainly
due to the lack of deep-rooted species [i.e., non-native Kentucky bluegrass as opposed to native
herbaceous species] in the riparian zone ". The potential for shade in the lower reaches of Pumpkin Creek
from a shrub or tree canopy, however, "may be limited" due to natural soil conditions. This evidence
suggests that the lower reaches of Pumpkin Creek may be meeting their potential from a shade
perspective. Therefore, human-caused habitat alterations may not be contributing to a potential
temperature problem.
Segment
Incisement
Lateral Cutting
Sediment Balance
Soil
Binding Root
Mass
Woody
Establishment
% Utilization
Riparian/Wetland
Characteristics
Flood plain
Irrigation impacts
Land Use
Activities
Subtotal
Potential Score
% of Potential
Sustainabiiity
Rating
PC-1-2
8
6
6
3
6
4
4
8
6
4
4
59
69
86%
Sustainable
PC-2-1
8
6
6
3
4
4
4
6
6
NA
NA
47
53
89%
Sustainable
PC-3-1
8
6
6
3
6
4
4
8
6
NA
NA
51
53
96%
Sustainable
PC-4-1
8
6
6
3
6
4
4
8
6
NA
NA
51
53
96%
Sustainable
PC-5-1
6
4
6
3
6
2
4
8
6
NA
NA
45
53
85%
Sustainable
PC-6-1
8
4
6
3
4
0
0
2
6
6
4
43
69
62%
At Risk
PC-7-1
8
4
6
3
4
0
0
2
6
8
4
45
69
65%
At Risk
PC-8-1
8
4
6
3
4
0
0
4
4
8
4
45
69
65%
At Risk
129
-------
Pumpkin Creek
Custer
County
Powder River
County
NRCS Reach Number
A/1 /Vs
A/8
Streams
Counties
NRCS Channel Assessment
• Channel Plug
« Water Spreading System
o Pump Site
Figure 6-14. NRCS in-channel assessment for Pumpkin Creek (Little Pumpkin Creek to the mouth)
130
-------
Tongue River Reservoir
7.0 TONGUE RIVER RESERVOIR
The Montana 1996 303(d) list reported that the Tongue River Reservoir (Segment ID MT42B003-010)
was impaired because of nutrients, organic enrichment/dissolved oxygen, and suspended solids (MDEQ,
1996). Aquatic life, fishery, and recreation/swimmable beneficial uses were impaired by these causes in
1996. The basis for the 1996 listing is unknown.
In 2006, MDEQ identified the Tongue River
Reservoir as impaired due only to algal
growth/chlorophyll-a (MDEQ, 2006a).
Aquatic life and recreational uses were
determined to be partially impaired
because of algal growth/chlorophyll-a. DEQ's
Assessment Record Sheet states that, "the TRR
is eutrophic due to entrophication caused by
phosphorus loads from agriculture and the
Sheridan Wastewater Treatment Plant. "
(MDEQ, 2006a). Agricultural and industrial
uses were found to be fully supporting in the
2006 303(d) report and drinking water and
fishery uses were not assessed.
This analysis specifically addresses the listed pollutants and impaired beneficial uses from the 1996 and
2006 303(d) lists. Salinity and sodium adsorption ratio (SAR) are also addressed given their potential
importance related to existing and future coal bed methane development in the watershed. The purpose of
this analysis is to determine if Montana's water quality standards are currently exceeded in the Tongue
River Reservoir and, if so, provide insight regarding the cause (i.e., natural versus anthropogenic).
The remainder of this section provides a summary and evaluation of the available data, and comparison to
the applicable Montana water quality standards one pollutant at a time. The methods by which Montana's
water quality standards have been applied are presented in Appendix B. Information about the operation
of the Tongue River Reservoir is presented in Appendix H, and sampling locations and reservoir
bathometry are presented in Figure 7-1. Biological data for the Tongue River Reservoir are discussed in
Appendix I.
Tongue River Reservoir and Dam.
Photo by Montana DNRC
131
-------
Tongue River Reservoir
7.1 Salinity
Limited amounts of SC data are available for the Tongue River Reservoir. MDEQ collected 40 samples
during the period 1974 to 1976 and then no data were collected until MDEQ performed additional
sampling during the summer and fall of 2001. USEPA collected additional data in the summer and fall of
2003. No additional reservoir salinity data have been collected since 2003.
All of the available data are summarized in Table 7-1 and station locations are shown in Figure 7-1. Most
SC values range between 200 (iS/cm and 800 (iS/cm with the 2001 samples typically higher than the 1974
to 1976 and 2003 data. The 2001 samples were collected from July to October when the reservoir volume
was relatively low (approximately 20,000 acre feet compared to 65,000 acre feet in 2003) and this might
have contributed to the higher values. Of the 237 salinity samples analyzed in the Tongue River
Reservoir, none has ever exceeded the 1,000 (iS/cm monthly average standard or the 1,500 (iS/cm
maximum standard.
Table 7-1. Summary of all available surface water SC data, Tongue River Reservoir (|jS/cm).
Station ID
Count
Average
Min
Max
Period of
Record
1975TO04
R
298
201
LO
1976
1975TO05
3
272
254
284
1975
2075T001
14
538
213
879
1975
2075T002
1
775
775
775
1974
2075T003
16
440
237
830
1975
TRR-1-1
1
430
430
430
2002
Y15TNGRR01
29
353
168
470
2003
Y15TNGRR02
46
375
173
733
2003
Y15TNGRR03
54
483
327
967
2003
Y15TRR10
49
695
6.3
782
2001
Y15TRR20
30
701
595
833
2001
Y15TRR31
6
693
655
767
2001
Y15TRR32
7
795
768
865
2001
Data collected by MDEQ and USEPA. Site locations are shown in Figure 7-1. Statistics are for all dates and sample depths.
132
-------
Tongue River Reservoir
.Y1STRR10
301401
2075TOQ2
Y15TRR3;
1975TI
STNGl
Y15TRRI
MONTANA
WYOMING
Figure 7-1. Tongue River Reservoir bathymetry and location of the water quality monitoring stations.
Y15TNGRR03'
Sampling Siles
Majoi Roads
Shoreline
Conlours (4 Ft)
Main Stem Tongue River
0 0.5 1 2 Miles
1 i ' ' i i i i i
133
-------
Tongue River Reservoir
The variability of salinity by depth in the reservoir is presented graphically in Figure 7-2, which
summarizes SC observations at the station near the dam (Y15TNGRR03) for the 2003 sampling events.
The data indicate that SC typically increases with depth, with values near the bottom of the reservoir
occasionally being greater than values at the surface.
o July 29, 2003
o August 21, 2003
o October 3, 2003
0
2
4
6
'e
8
.c
10
3"
Q
12
14
16
18
20
o
o
o
o
o
o
o
o
o
300 400 500 600 700
EC (us/cm)
Q.
-------
Tongue River Reservoir
7.3 Nutrients
As described in Section 7.0, the Tongue River Reservoir was listed as impaired for nutrients and organic
enrichment/dissolved oxygen on the 1996 303(d) list. In the 2006 303(d) list, nutrients were not
identified as a cause of impairment for the reservoir. However, aquatic life and fishery uses in 2006 were
listed as impaired because of chlorophyll-a (MDEQ, 2006a). Because of the interrelated nature of
nutrients, organic enrichment/low dissolved oxygen, and algal growth/chlorophyll-a impairments, they
are discussed together in this section under the general heading of nutrients.
As described in Appendix B, Montana's nutrient standards are narrative. In the absence of formal
numeric nutrient criteria, a suite of measurable indicators are presented below to provide insight into
current nutrient conditions in the Tongue River Reservoir relative to Montana's narrative nutrient
standards.
7.3.1 Total Phosphorus and Total Nitrogen
Total phosphorus (TP) and total nitrogen (TN) data for the Tongue River Reservoir are summarized in
Table 7-3 and Table 7-4. Median TP concentrations at the 13 stations range from 0.023 to 0.235 mg/L,
and median TN concentrations range from 0.23 to 1.33 mg/L. Concentrations of both nutrients are
somewhat higher during the 2001 and 2003 sampling compared to the 1975 sampling. As shown in
Figure 7-3, phosphorus resuspension and release from bottom sediments appears to be present at times,
causing significantly higher concentrations at depth.
Table 7-3. Summary of all available total phos
phorus data, Ton
gue River Reservoir (mg/L).
Station ID
Count
Median
Min
Max
Period of Record
1975TO05
3
0.030
0.020
0.040
1975
2075T001
4
0.023
0.020
0.050
1975
2075T003
3
0.030
0.020
0.040
1975
301401
8
0.040
0.022
0.141
1975
301402
10
0.052
0.043
0.148
1975
301403
5
0.060
0.045
0.112
1975
Y15TNGRR01
15
0.040
0.020
0.300
2003
Y15TNGRR02
13
0.032
0.020
0.057
2003
Y15TNGRR03
12
0.030
0.020
0.210
2003
Y15TRR10
4
0.035
0.014
0.048
2001
Y15TRR20
3
0.069
0.040
0.093
2001
Y15TRR31
1
0.235
0.235
0.235
2001
Y15TRR32
3
0.078
0.075
0.106
2001
Data collected by MDEQ and USEPA. Site locations are shown in Figure 7-1. Statistics are for all dates and sample depths. Detection limited data
were used as the detection limit value.
135
-------
Tongue River Reservoir
Table 7-4. Summary of all available total nitrogen data, Tongue River Reservoir (mg/L)
Station
Count
Median
Min
Max
Period of
Record
1975TO05
3
0.32
0.31
0.41
1975
2075T001
3
0.36
0.34
0.68
1975
2075T003
3
0.23
0.17
0.29
1975
301401
8
0.51
0.41
1.21
1975
301402
10
0.62
0.41
1.01
1975
301403
5
0.61
0.42
0.75
1975
Y15TNGRR01
15
0.71
0.52
0.93
2003
Y15TNGRR02
17
0.61
0.50
1.73
2003
Y15TNGRR03
15
0.62
0.12
2.21
2003
Y15TRR10
1
1.07
1.07
1.07
2001
Y15TRR20
1
1.02
1.02
1.02
2001
Y15TRR32
2
1.33
1.12
1.54
2001
Data collected by MDEQ and USEPA. Site locations are shown in Figure 7-1. Statistics are for all dates and sample depths. Detection limited data
were used as Vz the detection limit value.
April 25, 2003
June 27, 2003
July 29, 2003
August 21, 2003
October 3, 2003
Figure 7-3. Total phosphorus concentrations at depth in the Tongue River Reservoir near the Dam
(Station Y15TNGRR03).
A rough rule of thumb for assessing which nutrient limits plant growth relates to the nitrogen-to-
phosphorus ratio. Since the ratio of nitrogen to phosphorus in algal biomass (Redfield ratio) is
approximately 7.2, an N:P ratio in the water that is greater than 7.2:1 suggests that phosphorus is limiting
(Chapra, 1997). As displayed in Figure 7-4, N:P ratios in the Tongue River Reservoir average
approximately 18:1, suggesting that phosphorus is typically the limiting nutrient. Figure 7-5 also
suggests that there is a moderate positive relationship between paired TP and chlorophyll a data in the
reservoir.
136
-------
Tongue River Reservoir
50
45
40
35
30
25
20
15
10
5
0
1974
1 Limiting Nutrient Threshhold
(Approximate)
o
o
o
e
$
2.
*
e
o
<>
0-
o
1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Figure 7-4. TN:TP ratio for the Tongue River Reservoir.
50.0
45.0
40.0
3
*
35.0
<
30.0
_i
_i
25.0
0.
20.0
_l
T
15.0
O
10.0
5.0
0.0
0.00
0.05
0.10 0.15
TOTAL P (MG/L)
y = 105.23X + 6.4137
R2 = 0.3975
0.20
0.25
Figure 7-5. Relationship between total phosphorus and chlorophyll a for all paired samples in the
Tongue River Reservoir.
137
-------
Tongue River Reservoir
7.3.2 Chlorophyll-a
Chlorophyll a data for the Tongue River Reservoir are summarized in Table 7-5. Median chlorophyll a
concentrations range from 6.2 to 45.0 j^ig/L. Concentrations are similar over the entire period of record.
No information is available on the algal taxa present in the reservoir (i.e., the extent to which the biomass
is dominated by blue-green or other types of algae). As described in Appendix I, anecdotal evidence
suggests that nuisance algal blooms are not uncommon in the reservoir.
Station ID
Count
Median
Min
Max
Period of
Record
301401
3
16.9
7 3
20.5
1975
301402
3
20.5
11.2
24.5
1975
301403
3
7.3
4.9
38.8
1975
2075T001
1
20.0
20.0
20.0
1993
Y15TNGRR01
6
14.0
6.0
20.0
2003
Y15TNGRR02
5
9.0
8.0
13.0
2003
Y15TNGRR03
6
10.5
7.0
12.0
2003
Y15TRR10
3
6.2
5.6
14.0
2001
Y15TRR20
3
12.0
8.6
35.0
2001
Y15TRR31
3
45.0
4.5
54.0
2001
Composite samples from the euphotic zone. Data collected by MDEQ and USEPA. Site locations are shown in Figure 7-1. Detection limited data
were used as the detection limit value.
7.3.3 Comparison to Other Reservoirs and Literature Values
The purpose of this section is to compare total phosphorus, total nitrogen, and chlorophyll-a data from the
Tongue River Reservoir to other reservoirs that are located near, or in a similar ecoregional setting to the
Tongue River watershed. The spatial extent of the analysis was determined by a number of factors
including climate, elevation, ecoregion, stream type, contributing drainage area, and data availability.
The goal was to select lakes and reservoirs that had characteristics similar to the Tongue River Reservoir
watershed. Based on this, four reservoirs were selected from Montana, Wyoming, and North Dakota -
Big Horn Reservoir (also referred to as Yellowtail Reservoir on the Big Horn River), Keyhole Reservoir
(Belle Fourche River), Lake DeSmet (Piney Creek and Shell Creek), and Boysen Reservoir (Wind River).
Data from these reservoirs were plotted with the data collected in the Tongue River Reservoir to provide a
preliminary comparison. It should be noted that the number of samples and period of record varied for
each reservoir, and recent data were limited in all of the reservoirs (Table 7-6). Because of the limited
data, all available data (regardless of location within the reservoir, depth, or time period) are presented.
Table 7-6. Number of nutrient samples per reservoir and associated period of record.
Reservoir
# TP Samples
# TN Samples
# Chlorophyll-a Samples
Period of Record1
Tongue River Reservoir
88
83
27
1975; 1993; 2001; 2003
Big Horn Reservoir
35
60
65
1975; 1980; 1984-1985
Boysen Reservoir
67
67
25
1975; 1981
Keyhole Reservoir
53
53
21
1975; 1981
Lake Desmet
27
64
6
1975
Period of Record for all three parameters combined.
138
-------
Tongue River Reservoir
It should also be noted that the reservoirs selected for this analysis are not meant to represent "reference
conditions" for the Tongue River Reservoir. It is beyond the scope of this analysis to conduct a detailed
assessment for each of the four reservoirs. Rather, the purpose of this analysis is to put nutrient data in
the Tongue River Reservoir into context with similar neighboring reservoirs to better understand existing
conditions.
Nutrient data were also compared to nutrient targets obtained from a literature review. South Dakota
developed ecoregional Carlson's Trophic State Index (Carlson, 1977) (TSI) targets for lakes and
reservoirs. For reservoirs classified as "warm water permanent fisheries", South Dakota considers a TSI
value greater than 58.5 as "impaired", and a score lower than 58.5 as "not impaired," (SDDNR, 2005).
Using the formulas below, a Carlson's TSI score of 58.5 translates into a total phosphorus target of 0.043
mg/L, and a chlorophyll-a target of 17 (ig/L.
TSI (TP) = 10 x (6 - Ln(48/ TP) ^ ^ w|lcrc yp js jn ^g/L (Carlson, 1977)
Ln2
TSI (CM) = 10 x ( 6 - 3^1—0.68(Ln(Chl)\ ^ w|lcrc chlorophyll-a is in (ig/L (Carlson, 1977)
^ Ln2 J
USEPA developed nutrient guidance for lakes and reservoirs using the 25th percentile of a large set of
data obtained throughout a defined nutrient ecoregion. The 25th percentile approach assumes that 25
percent of the sampled lakes and reservoirs (e.g., the "best" 25 percent) are surrogates for reference
conditions (USEPA, 2001). The Tongue River is located in nutrient Ecoregion 4 (Great Plains Grass and
Shrublands), where the recommended nutrient targets are as follows: 0.020 mg/L TP, 0.44 mg/L TN, and
2.0 (ig/L chlorophyll-a (USEPA, 2001).
The Tongue River watershed LSPC and CE-QUAL-W2 models were used to examine what conditions
would be like in the Tongue River Reservoir in the absence of human actions (i.e., the "natural"
condition). All human influences were removed from the two models (e.g., diversions, irrigation,
developed land, point sources, etc.) and model output was examined. The average annual median
concentrations for TP, TN, and chlorophyll-a under the natural condition were 0.010 mg/L, 0.028 mg/L,
and 1.5 (ig/L, respectively. The Modeling Report has additional details about model setup, use, and
uncertainty, while the natural scenario is further defined in Appendix J.
The various reservoir data, literature values, and model results are presented graphically in Figure 7-6 and
Figure 7-7. The following sections discuss total phosphorus, total nitrogen, and chlorophyll-a
individually.
Total Phosphorus
The median TP value for the Tongue River Reservoir (0.040 mg/L) was similar to other median values
found in reservoirs throughout the region (medians ranging from 0.029 to 0.061 mg/L), and it was less
than the South Dakota recommended target of 0.043 mg/L. The maximum TP value (0.300 mg/L) was
significantly less than those found in Big Horn and Keyhole Reservoirs (0.950 and 1.000 mg/L,
respectively). However, the median value for the Tongue River Reservoir exceeded the modeled
"natural" and USEPA targets.
139
-------
Tongue River Reservoir
0 25-75 Ftercentile
~ Median
Min-Max
Average
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Tongue River Big Horn Lake DeSmet Keyhole Boysen
Reservoir Reservoir Reservoir Reservoir
Modeled South Dakota USEPA
"Natural" "Full Support" Reference
Target Condition
Figure 7-6. Comparison of total phosphorus data from the Tongue River Reservoir to other reservoirs
and literature values.
Total Nitrogen
The median TN value for the Tongue River Reservoir (0.63 mg/L) was higher than all of the other median
values for reservoirs throughout the region (medians ranging from 0.42 to 0.62 mg/L), and it was higher
than the USEPA recommended target of 0.44 mg/L. The maximum TN value (2.21 mg/L) was more than
those found in the Big Horn, Keyhole, and Lake DeSmet Reservoirs (1.23, 1.41, and 1.53 mg/L,
respectively). Boysen Reservoir was the only reservoir with a higher maximum TN value (2.80 mg/L).
All of the reservoirs exceeded the annual median modeling target of 0.027 for "natural" conditions.
25-75 Ftercentile
~ Median
Min-Max
Average
3.00
Tongue River
Reservoir
Keyhole
Reservoir
Boysen
Reservoir
Modeled
"Natural"
USEPA
Reference
Condition
Figure 7-7. Comparison of total nitrogen data from the Tongue River Reservoir to other reservoirs and
literature values.
140
-------
Tongue River Reservoir
Chlorophyll-a
The median chlorophyll-a value for the Tongue River Reservoir (11 (ig/L) was higher than all of the other
median values for reservoirs throughout the region (medians ranging from 2 to 10 (ig/L). The maximum
chlorophyll-a value (54 (ig/L) was higher than those found in the Boysen, Keyhole, and Lake DeSmet
Reservoirs (14, 14, and 21 (ig/L, respectively). Big Horn Reservoir was the only reservoir with a higher
maximum chlorophyll-a value (69 (ig/L). All of the reservoirs exceeded the annual median modeling
target of 1.4 (ig/L for "natural" conditions, and all of the median values except for Boysen Reservoir
exceeded the USEPA target of 2.0 j^ig/L. The South Dakota target of 17 j^ig/L was not exceeded.
| 25-75 Ftercentile
~ Median
Min-Max
Average
.c
Q.
g
o
£
o
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
Tongue River Big Horn Lake DeSrret Keyhole Boysen South Dakota Modeled USEPA
Reservoir Reservoir Reservoir Reservoir "Full Support" "Natural" Reference
Target Condition
Figure 7-8. Comparison of chlorophyll-a data from the Tongue River Reservoir to other reservoirs and
literature values.
7.3.4 Carlson's TSI
Secchi disk transparency, chlorophyll a, and total phosphorus are often used to define the degree of
eutrophication or trophic status of a lake. The concept of trophic status is based on the fact that changes in
nutrient levels (measured by total phosphorus) usually cause changes in algal biomass (measured by
chlorophyll a) which in turn causes changes in lake clarity (measured by Secchi disk transparency).
A trophic state index is a convenient way to quantify this relationship. One popular index was developed
by Carlson (1977). His index uses a log transformation of Secchi disk values as a measure of algal
biomass on a scale from 0 to 110. Each increase of ten units on the scale represents a doubling of algal
biomass. Companion measures are based on TP and chlorophyll-a concentrations.
The Carlson trophic state index is useful for comparing lakes within a region and for assessing changes in
trophic status over time. However, the index was developed for use with lakes that have few rooted
aquatic plants and little non-algal turbidity. Because non-algal turbidity can be significant in the Tongue
River Reservoir, the index is used to provide primarily a qualitative perspective on the condition of the
reservoir. The formulas for calculating Carlson's TSI are shown below.
141
-------
Tongue River Reservoir
TSI (TP) = 10 x (6 - Ln(48/ TP) ^ ^ ^.|lcrc yp js jn ^g/L (Carlson, 1977)
Ln2
TSI (Chi) = 10 x [ 6 : :—-———- j. where chlorophyll-a is in (ig/L (Carlson, 1977)
^ Ln2 J
Chlorophyll-a and total phosphorus samples were obtained in the Tongue River Reservoir in 2001 and
2003 at three locations - north end, middle, and south end. TSI values were calculated for samples
obtained in the surface layer between May 15 and September 15 of each year. A summary of the values
is shown in Table 7-7. Values ranged from 42 to 83, indicating a range of conditions from mesotrophic
(i.e., water moderately clear; increasing probability of hypolimnetic anoxia during summer) to
hypereutrophic (i.e., light limited productivity with algal scum and few macrophytes) (Carlson and
Simpson, 1996).
Year
Parameter
Min
Max
Average
2001
Chlorophyll-a
48
68
56
Total Phosphorus
42
83
61
2003
Chlorophyll-a
50
59
54
Total Phosphorus
49
71
55
7.3.5 Dissolved Oxygen
The available dissolved oxygen data for the reservoir are summarized in Table 7-8. The average
dissolved oxygen concentration from the 2001 and 2003 surveys is approximately 6 mg/L. However, 29
percent of all dissolved oxygen samples were below the 5.0 mg/L minimum water quality standard (74
out of 255 samples). Most samples below 5.0 mg/L occur at lower depths (Figure 7-9). These areas of
low oxygen limit the extent of suitable habitat for various sensitive aquatic life species, but are not
thought to be a major concern to the fishery (Brad Schmitz, Montana Fish, Wildlife and Parks, personal
communication June 24, 2005).
142
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Tongue River Reservoir
Table 7-8. Summary of dissolved oxygen data, Tongue River Reservoir (mg/L).
Station
Count
Average
Min
Max
Period of
Record
2075T001
3
10.8
10.1
11.7
1976
301401
8
9.0
4.2
13.2
1975
301402
10
9.4
4.2
14.8
1975
301403
5
10.1
9.6
11.4
1975
TR5
1
8.5
8.5
8.5
1976
TR6
4
10.6
6.5
14.5
1975
TR7
3
7.6
3.1
10.9
1975
Y15TNGRR01
29
7.4
2.6
11.1
2003
Y15TNGRR02
46
6.5
0.1
12.0
2003
Y15TNGRR03
54
3.9
0.1
9.5
2003
Y15TRR10
49
4.8
0.1
9.2
2001
Y15TRR20
30
7.2
0.2
11.0
2001
Y15TRR31
6
9.6
8.5
11.0
2001
Y15TRR32
7
9.8
6.9
12.0
2001
Data collected by MDEQ and USEPA. Site locations are shown in Figure 7-1. Statistics are for all dates and sample depths.
143
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Tongue River Reservoir
o July 26, 2001
o August 16, 2001
o September 26, 2001
-C
Q.
<1)
Q
0
2
4
6
8
10
12
14
16
18
20
8
o
o
o
2 4 6 8 10
DO (mg/L)
0
2
4
6
8 £
o
10 4
12
14
16
18
20
0
8
o
o
o
o
2 4 6 8 10
DO (mg/L)
-------
Tongue River Reservoir
The occurrence of stratification in a reservoir is a function of morphometry, weather, and release patterns
(Krenkel and Novotny, 1980; Wetzel, 2001). Most deep reservoirs in temperate zones will stratify, and
oxygen depletion in the hypolimnion will occur if stratification lasts long enough. Few data are available
to determine the typical length of stratification in the Tongue River Reservoir but it was stratified for at
least two months in 2001 and three months in 2003 (see Figure 7-9).
Oxygen depletion in the hypolimnion occurs as a result of both internal production of carbon and external
loading of carbon (Wetzel, 2001). Phosphorus loading is an indicator of internal production, and is also
typically correlated to landscape carbon loading. As a guide, Welch and Perkins (1979) estimated the
hypolimnetic oxygen depletion rate as a function of external phosphorus load and residence time:
log ODR = 1.51 + 0.39 log (L/p)
where ODR is the hypolimnetic oxygen depletion rate (mg/m2/d), L is the external phosphorus loading
rate (mg/m2/T), and p is the overlow rate (1/T). Given the oxygen depletion rate and the volume of the
hypolimnion, the time required to reach hypoxia can be estimated. Using this equation and data from the
LSPC and W2 models, the number of days in the Tongue River Reservoir with anoxic conditions could
be estimated. Under the existing condition scenario, the estimated number of days with anoxic conditions
was 1,011 out of 2,159 (47 percent). Under the natural scenario, the estimated number of days with
anoxic conditions was 865 out of 2,159 (40 percent). Appendix J provides further details regarding the
simulation of the existing and natural conditions.
7.3.6 Nutrient Sources
The potential sources of nutrients to the Tongue River Reservoir include:
• Upstream "natural" loads associated with groundwater and upland and streambank erosion
• Upstream applications of fertilizers to crops and residential lawns
• Upstream wastewater treatment effluent flows
• Other upstream point sources (i.e., CBM, coal mines)
• Upstream cattle grazing impacts
• In-reservoir cycling of phosphorus from the bottom sediments of the reservoir
• In-reservoir shoreline erosion
Summary information on the point sources is presented in Appendix A of the Modeling Report. Failing
septic systems are assumed to be a minor source of total nutrient loadings due to the large size and
sparsely populated nature of the watershed.
The LSPC model was used to estimate nutrient loads from upstream sources to the Tongue River
Reservoir. Existing and natural condition scenarios were run, as well as scenarios to evaluate the impacts
of irrigation, CBM, and wastewater treatment plants. Model output was evaluated at subbasin 3001,
which is the last modeling subbasin before the Tongue River Reservoir. The total simulated TN and TP
loads for various scenarios are shown in Table 7-9. In the absence of anthropogenic sources (i.e., the
natural scenario), TN and TP loads would be 22 and 24 percent lower than the existing condition
scenario. CBM had the largest impact on total nitrogen loads in the Tongue River (8 percent lower than
existing conditions without CBM), followed by wastewater treatment and then irrigation.
By far, based on model results, the wastewater treatment plants appear to have the largest impact on total
phosphorus (29 percent difference), and CBM is only a relatively small contributor (3 percent difference).
The model suggests that without irrigation, total phosphorus loading would be higher than in the existing
145
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Tongue River Reservoir
condition, although this phenomenon is assumed to be due to the associated flow alterations and not with
any "treatment" of phosphorus by irrigation practices. Note that model uncertainty is discussed in the
Modeling Report.
Table 7-9. Total modeled nutrient loads for various scenarios for the Tongue River watershed draining
to the Tongue River Reservoir (modeling subbasin 3001).
Parameter
Existing Load
(tons)
Natural
No Irrigation
NoCBM
No WWTP
tons
% \
tons
% \
tons
% \
tons
% \
Total Nitrogen
945.8
739.5
-22%
895.2
-5%
867.7
-8%
891.9
-6%
Total Phosphorus
151.6
115.0
-24%
165.2
9%
147.3
-3%
107.3
-29%
No data are available on the extent of phosphorus recycling from the bottom of the reservoir. However,
under certain conditions, bottom sediments can be important sources of phosphorus to the overlying
waters of reservoirs, particularly if the reservoir is shallow or experiences period of low dissolved oxygen
(Chapra, 1997). Under well-oxygenated conditions, phosphorus forms insoluble ferric hydroxide
complexes and sediments out of the water column. Under low-oxygen conditions these complexes
dissociate and phosphorus may be released from the sediment layer, entering the water column and
contributing to loading (Chapra, 1997). Indicators of potential nutrient loading from sediment sources
include probable high concentrations of phosphorus in the sediment and known low-oxygen conditions in
the waterbody, or evidence of algal blooms following turnover.
The CE-QUAL-W2 reservoir model assumed a TP load equal to 0.015 times the SOD rate, or 18.75 mg-
P/m2/d from the bottom sediments for those days and in those areas where the reservoir becomes anoxic
(oxygen less than 0.1 mg/L). Because profile data for nutrients in the reservoir were lacking, this rate
could not be calibrated. In addition, much of this sediment phosphorus release will eventually be sorbed
and recycled back to the sediments, and the release will not occur under aerobic conditions. The CE-
QUAL-W2 parameter thus provides an approximate upper bound on the likely recycle rate of phosphorus
from the sediments.
Another perspective on the net contribution of phosphorus recycling from the sediment can be obtained
by applying the method of Nurnberg (1984; cited in Welch and Jacoby, 2004). This approach applies an
empirical TP retention coefficient for oxic conditions without sediment regeneration of TP, based on
flushing rate and average depth to the inflow TP, then uses the difference between predicted and observed
inlake TP to estimate net sediment recycling. Specifically,
Lint = zp [TP-TP.-(l-R)],
where Lmt is the net internal loading rate, z is the mean depth, p is the flushing rate, TP is the inlake
average TP concentration, TP; is the influent average TP concentration, and R is the net recycle rate for
oxic conditions, estimated as 15/(18 + zp).
Using data from 2000-2006, the mean depth of the Tongue River Reservoir is 5.06 m, flushing rate 4.155
yr"1, influent TP 56.66 (ig/L, and inlake TP average 55.38 (ig/L. Applying Nurnberg's method yields an
estimated net sediment phosphorus recycle rate of 1.18 mg/P/m2/d - as an average over all portions of the
bottom sediment and all times of the year. The total resulting load is 4,308 kg/yr (4.75 tons/yr), which is
much smaller than the existing external load - suggesting that net recycling from the sediment is likely of
minor importance for the total P balance of the reservoir.
146
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Tongue River Reservoir
Shoreline erosion is an additional potential source of sediment and TP because of the frequently changing
reservoir volumes and subsequent wetting and drying of the shoreline soils. No information is available
with which to make an estimate of shoreline erosion.
7.4 Suspended Solids
As described in Section 7.0, the Tongue River Reservoir was listed as impaired for total suspended solids
(TSS) on the 1996 303(d) list. The basis of this listing is unknown. Suspended solids were not identified
as a cause of impairment on the 2006 303(d) list. This section presents an updated evaluation of the
Tongue River Reservoir relative to siltation/suspended solids.
The analysis is divided into two sections: (1) an evaluation of measured data and; (2) analysis of sources.
7.4.1 Measured Data
All available SSC and TSS data for the Tongue River Reservoir are summarized in Table 7-10. Data
collected in the Tongue River are presented in Section 3.4. Most concentrations in the reservoir are
relatively low (less than 10 mg/L) and range from 2 to 121 mg/L. The median value of all samples is 8
mg/L.
Concentrations near the dam are usually less than concentrations in the upstream (southern) portion of the
reservoir. This may be due to the settling of the larger particles as they move downstream. DNRC reports
that most large soil particles settle out prior to even reaching the reservoir and therefore sedimentation of
the reservoir has not historically been a problem (Personal Communications, Kevin Smith, March 21,
2005). As shown in Section 3.4.3, approximately 72 percent of the suspended solids are settled out the
Tongue River between the USGS gage at the state line (06306300) and downstream of the Tongue River
Reservoir Dam (06307500).
Table 7-10. Summary of all available TSS data, Tongue River Reservoir (mg/L).
Station ID
Count
Average
Min
Max
Period of Record
198
15
6.4
2.0
14.4
1975-1976
137
3
22.0
2.0
42.0
1975
196
14
CO
CO
4.9
13.1
1975-1976
136
6
20.7
5.4
51.3
1976
Y15TRR01
8
10.0
10.0
10.0
2001
Y15TRR03
4
38.5
21.0
73.0
2001
Y15TRR02
6
22.8
10.0
50.0
2001
Y15TNGRR03
13
14.0
4.0
121.0
2003
Y15TNGRR02
12
6.4
4.0
23.0
2003
Y15TNGRR01
12
12.1
4.0
60.0
2003
Data collected by MDEQ and USEPA. Site locations are shown in Figure 7-1.
7.4.2 Sediment Sources
Soils in the Tongue River watershed are naturally highly erodible (see the Status Report; MDEQ,
2003). These attributes, in combination with semiarid conditions, flashy rain events, and sparse
ground cover, result in naturally high sediment erosion. Buttes and badlands occur throughout
the landscape, and saline or sodic soils limit plant growth in several areas.
147
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Tongue River Reservoir
Cattle are the predominant agricultural resource in the watershed (NASS, 2002) and it is well documented
that cattle have the potential to impact the landscape, if not managed properly (Meehan, 1991). In the
uplands, decreased ground cover, increased erosion, and the promotion of invasive species can occur from
overgrazing. In the lowlands and stream valleys, cattle grazing can have direct impacts to the stream and
riparian area (destabilized stream banks, lack of riparian cover, habitat degradation) (Meehan, 1991).
However, the relative contribution of sediment to the stream is unknown.
Other potential sediment sources upstream of the Tongue River Reservoir may include unpaved roads,
irrigated agriculture, various drainage features (return flows and irrigation dikes) that may alter both the
flow and sediment dynamics in the system, and disturbed lands associated with the construction and
operation of coal mines and coal bed methane development. Both water spreading and sprinkler irrigation
are common throughout the mainstem of the Tongue River, but both are generally constructed to
minimize water loss and erosion from a field (NRCS, 2002). Irrigation can affect flows and sediment
supply in the stream, resulting in a lack of flushing flows and sediment imbalances. The effect of
irrigation on in-stream sediment and sediment supply is unknown, and unquantifiable at the time of this
report.
Another potential source of sediment loading to the reservoir is shoreline erosion. Shoreline erosion in a
reservoir occurs when wave activity undercuts poorly consolidated soils and the higher slopes undergo
mass movement into the water (Wetzel, 2001). This type of erosion is considered to potentially be
significant in the Tongue River Reservoir because of (1) the large month-to-month variability in water
volumes (which exposes large surface areas; see Appendix H); and (2) high winds that contribute to
frequent wave activity. At the time of this report, no data have been collected with which to quantify the
magnitude of shoreline erosion.
148
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Summary and Conclusions
8.0 SUMMARY AND CONCLUSIONS
This document presents an assessment of water quality in the Tongue River, Tongue River Reservoir, and
Hanging Woman, Otter, and Pumpkin Creeks. This assessment is based on data and information through
September 2006 (this varies on a case-by-case basis depending upon data availability). The focus was on
the listed pollutants and impaired beneficial uses from the 1996 and 2006 Montana 303(d) lists.
Pollutants addressed included salinity, sodium adsorption ratio (SAR), metals, sulfates, sediment,
nutrients, dissolved oxygen, and temperature. The primary purpose of this assessment was to compare the
available water quality data to the applicable Montana water quality standards. This comparison has been
made for informational purposes to provide watershed stakeholders and decision makers with baseline
information regarding the current condition of the waters in the Tongue River Watershed. Formal
interpretation of Montana's water quality standards and 303(d) impairment decisions are beyond the
scope of these analyses and are not provided.
149
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