Water-Quality Characteristics of 

Quaternary Unconsolidated-Deposit 

Aquifers and Lower Tertiary Aquifers of the 

Bighorn Basin, Wyoming and Montana, 

1999-2001 

By Timothy T. Bartos, Cheryl A. Eddy-Miller, Jodi R. Norris, Merry E. Gamper, and 

Laura L. Hallberg 

Prepared as part of the 

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM 

Scientific Investigations Report 2004-5252 

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

Gale A. Norton, Secretary 

U.S. Geological Survey 

Charles G. Groat, Director 

U.S. Geological Survey, Reston, Virginia: 2005 

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


Box 25286, Denver Federal Center


Denver, CO 80225


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duce any copyrighted materials contained within this report.


Information regarding the National Water-Quality Assessment (NAWQA) Program is available on the Internet via the 

World Wide Web. You may connect to the NAWQA Home Page using the Universal Resource Locator (URL): 

http://wwwrvares.er.usgs.gov/nawqa/nawqa_home.html> 
iii 

FOREWORD 

The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and timely scientific information that helps enhance and protect the overall quality of life, and facilitates effective management of water, biological, energy, and mineral resources. (http://www.usgs.gov/). 

Information on the quality of the Nation’s water resources is of critical interest to the USGS 

because it is so integrally linked to the long-term availability of water that is clean and safe for 

drinking and recreation and that is suitable for industry, irrigation, and habitat for fish and wildlife. 

Escalating population growth and increasing demands for the multiple water uses make water 

availability, now measured in terms of quantity and quality, even more critical to the long-term 

sustainability of our communities and ecosystems. 

The USGS implemented the National Water-Quality Assessment (NAWQA) Program to support 

national, regional, and local information needs and decisions related to water-quality management and policy. (http://water.usgs.gov/nawqa/). Shaped by and coordinated with ongoing 

efforts of other Federal, State, and local agencies, the NAWQA Program is designed to answer: 

What is the condition of our Nation’s streams and ground water? How are the conditions changing 

over time? How do natural features and human activities affect the quality of streams and ground 

water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. NAWQA results 

can contribute to informed decisions that result in practical and effective water-resource management and strategies that protect and restore water quality. 

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more than 

50 of the Nation’s most important river basins and aquifers, referred to as Study Units. 

(http://water.usgs.gov/nawqa/nawqamap.html). Collectively, these Study Units account for more 

than 60 percent of the overall water use and population served by public water supply, and are 

representative of the Nation’s major hydrologic landscapes, priority ecological resources, and 

agricultural, urban, and natural sources of contamination. 

Each assessment is guided by a nationally consistent study design and methods of sampling and 

analysis. The assessments thereby build local knowledge about water-quality issues and trends 

in a particular stream or aquifer while providing an understanding of how and why water quality 

varies regionally and nationally. The consistent, multi-scale approach helps to determine if certain 

types of water-quality issues are isolated or pervasive, and allows direct comparisons of how 

human activities and natural processes affect water quality and ecological health in the Nation’s 

diverse geographic and environmental settings. Comprehensive assessments on pesticides, nutrients, volatile organic compounds, trace metals, and aquatic ecology are developed at the national 

scale through comparative analysis of the Study-Unit findings. 

(http://water.usgs.gov/nawqa/natsyn.html). 

The USGS places high value on the communication and dissemination of credible, timely, and relevant science so that the most recent and available knowledge about water resources can be 

applied in management and policy decisions. We hope this NAWQA publication will provide you 

the needed insights and information to meet your needs, and thereby foster increased awareness 

and involvement in the protection and restoration of our Nation’s waters. 
iv 

The NAWQA Program recognizes that a national assessment by a single program cannot address 

all water-resource issues of interest. External coordination at all levels is critical for a fully integrated understanding of watersheds and for cost-effective management, regulation, and conservation of our Nation’s water resources. The Program, therefore, depends extensively on the 

advice, cooperation, and information from other Federal, State, interstate, Tribal, and local agencies, non-government organizations, industry, academia, and other stakeholder groups. The assistance and suggestions of all are greatly appreciated. 

Robert M. Hirsch 

Associate Director for Water 
v 

Contents 

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


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


Appendix 1-1.—Land use and land cover mapped within 500-meter radius of sampled wells,


Appendix 1-2.—Land use and land cover mapped within 500-meter radius of sampled wells, lower 


Appendix 2-1.—Replicate data for major ions, trace elements, nutrients, and dissolved organic 


Appendix 2-2.—Replicate data for major ions, trace elements, nutrients, and dissolved organic 


Appendix 2-3.—Concentrations and calculated relative-percent differences of pesticides detected 


Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2


Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Description of the study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Geographic, physiographic, and geologic setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Hydrogeologic setting and ground-water use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7


Climate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


Methods of investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


Ancillary data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


Land use and land cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


Site selection and well construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


Sample collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17


Chemical analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17


Quality assurance and quality-control samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23


Blank samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23


Replicate samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32


Field-matrix spike samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37


Major-ion balances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38


Statistical methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38


Ground-water quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39


Ground-water age . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39


Physical characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40


Major ions and related water-quality characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40


Trace elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49


Nutrients and dissolved organic carbon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56


Radionuclides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61


Pesticide compounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64


Volatile organic compounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69


Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75


References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77


Quaternary aquifers, 1999-2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84


Tertiary aquifers, 2000-2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86


carbon, samples from Quaternary aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88


carbon, samples from lower Tertiary aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91


in replicate samples from the Quaternary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

vi 

Appendix 2-4.—Concentrations and calculated relative-percent differences of volatile organic 

compounds (VOCs) detected in replicate samples using unrounded data, 

Quaternary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96


Appendix 2-5.—Concentrations and calculated relative-percent differences of volatile organic 


compounds (VOCs) detected in replicate samples from the lower Tertiary aquifers . . . . . . 97


Appendix 3-1.—Graph showing pesticide field-matrix spike recoveries, samples from Quaternary 


aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98


Appendix 3-2.—Graph showing pesticide field-matrix spike recoveries, samples from Quaternary 


aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99


Appendix 3-3.—Graph showing pesticide field-matrix spike recoveries, samples from lower Tertiary 


aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100


Appendix 3-4.—Graph showing pesticide field-matrix spike recoveries, samples from lower Tertiary 


aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101


Appendix 3-5.—Graph showing volatile organic compound (VOC) field-matrix spike recoveries, 


samples from Quaternary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102


Appendix 3-6.—Graph showing volatile organic compound (VOC) field-matrix spike recoveries, 


samples from Tertiary aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103


Appendix 4-1.—Analyses for physical characteristics, samples fromQuaternary aquifers . . . . . . . . . . . . . . . . .104


Appendix 4-2.—Analyses for physical characteristics, samples from lower Tertiary aquifers. . . . . . . . . . . . . . .105


Appendix 5-1.—Analyses for major ions and related water-quality characteristics, samples from 


Quaternary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106


Appendix 5-2.—Analyses for major ions and related water-quality characteristics, samples from 


lower Tertiary aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .108


Appendix 6-1.—Analyses for trace elements, samples from Quaternary aquifers . . . . . . . . . . . . . . . . . . . . . . . . . .110


Appendix 6-2.—Analyses for trace elements, samples from lower Tertiary aquifers. . . . . . . . . . . . . . . . . . . . . . . .112


Appendix 7-1.—Analyses for nutrients and dissolved organic carbon, samples from Quaternary 


aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114


Appendix 7-2.—Analyses for nutrients and dissolved organic carbon, samples from lower Tertiary 


aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115


Appendix 8-1.—Analyses for radionuclides, samples from Quaternary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . .116


Appendix 8-2.—Analyses for radionuclides, samples from lower Tertiary aquifers . . . . . . . . . . . . . . . . . . . . . . . . .118


Appendix 9-1.—Analyses for pesticides, samples from Quaternary aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120


Appendix 9-2.—Analyses for pesticides, samples from lower Tertiary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . .130


Appendix 10-1.—Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers. . . . .140


Appendix 10-2.—Analyses for volatile organic compounds (VOCs), samples from lower Tertiary 


aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148


Figures 

1. 	 Map showing location of the Bighorn Basin study area in relation to the Yellowstone River 


Basin NAWQA study unit, Wyoming, Montana, and North Dakota. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3


2. 	 Map showing generalized geology and physiographic provinces, Bighorn Basin study area 


and Yellowstone River Basin NAWQA study unit, Wyoming, Montana, and North Dakota. . . . . . . . . . .5


3. 	 Schematic geologic section across the central part of the Bighorn Basin in Wyoming . . . . . . . . . . . . . .6


4.	 Map showing location of Tertiary-age Willwood and Fort Union Formations and sampled 


wells in the Bighorn Basin study area, Wyoming and Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

vii 

5.	 Map showing location of Quaternary unconsolidated deposits and sampled wells in the 


Bighorn Basin study area, Wyoming and Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .9


6.	 Simplified schematic diagram showing relation of domestic, stock, and monitoring wells to 


hydrogeology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11


7.	 Map showing distribution of land use and land cover on Quaternary unconsolidated deposits 


in the Bighorn Basin, Wyoming and Montana. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13


8.	 Map showing distribution of land use and land cover on or overlying lower Tertiary rocks in 


the Bighorn Basin, Wyoming and Montana. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


9.	 Graph showing physical characteristics of ground-water samples collected from Quaternary 


and lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2001. . . . . . . . . . . . . . . . . . . 45


10.	 Graph showing major-ion concentrations and related water-quality characteristics of ground­


water samples collected from Quaternary and lower Tertiary aquifers, Bighorn Basin,


Wyoming and Montana, 1999-2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46


11.	 Trilinear diagram showing major-ion composition and dissolved-solids concentrations for 


ground-water samples collected from Quaternary aquifers, Bighorn Basin, Wyoming and 


Montana, 1999-2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50


12.	 Stiff diagrams showing areal distribution of major-ion composition and dissolved-solids 


concentrations for ground-water samples collected from Quaternary aquifers,Bighorn 


Basin, Wyoming and Montana, 1999-2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51


13.	 Trilinear diagram showing major-ion composition and dissolved-solids concentrations for 


ground-water samples collected from lower Tertiary aquifers, Bighorn Basin, Wyoming 


and Montana, 2000-2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52


14.	 Stiff diagrams showing areal distribution of major-ion composition and dissolved-solids 


concentrations for ground-water samples collected from lower Tertiary aquifers, 


Bighorn Basin, Wyoming and Montana, 2000-2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53


15-17. Graphs showing: 

15. 	 Trace-element concentrations in ground-water samples collected from Quaternary 


and lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2001. . . . . . . . . . . . . 54


16.	 Nutrient and dissolved organic carbon (DOC) concentrations in ground-water 


samples collected from Quaternary and lower Tertiary aquifers, Bighorn Basin, 


Wyoming and Montana, 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58


17.	 Radionuclide concentrations in ground-water samples collected from Quaternary 


and lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2001. . . . . . . . . . . . . 62


18.	 Map showing pesticide detections in ground-water samples collected from Quaternary 


aquifers, Bighorn Basin, Wyoming and Montana, 1999-2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66


19.	 Map showing pesticide detections in ground-water samples collected from lower Tertiary 


aquifers, Bighorn Basin, Wyoming and Montana, 2000-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68


20.	 Graph showing twenty most commonly used pesticides in the Bighorn Basin, Wyoming 


and Montana, 1994, and comparison with frequency of detection in ground-water samples 


collected from Quaternary and lower Tertiary aquifers, 1999-2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69


21.	 Graph showing crop types and percentage of total crop production for the years 1994 and 


2000 in the Bighorn Basin, Wyoming and Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70


22.	 Map showing volatile organic compounds (VOCs) detected in ground-water samples 


collected from Quaternary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2000. . . . . . . . . . . 72


23.	 Map showing volatile organic compounds (VOCs) detected in ground-water samples 


collected from lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 2000-2001 . . . . . . . . 74

viii 

Tables 

1. 	 Percent land use and land cover mapped within 500-meter radius of sampled wells.. . . . . . . . . . . . . . 15


2. 	 Well construction and related ancillary information for sampled wells completed in Quaternary 


aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18


3. 	 Well construction and related ancillary information for sampled wells completed in lower 


Tertiary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20


4. 	 Laboratory methods used to analyze ground-water samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24


5. 	 Pesticides analyzed, trade name, pesticide action, class, laboratory reporting levels, and U.S. 


Environmental Protection Agency health benchmarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25


6. 	 Volatile organic compounds (VOCs) analyzed, laboratory reporting levels, and related U.S. 


Environmental Protection Agency standards.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29


7. 	 Summary of major ions, trace elements, nutrients, and dissolved organic carbon detected in


field-equipment blank samples and in environmental samples collected during sampling of 


Quaternary aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 33


8.	 Summary of major ions, trace elements, nutrients, and dissolved organic carbon detected


in field-equipment blank samples and in environmental samples collected duringsampling 


of lower Tertiary aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34


9. 	 Summary of volatile organic compounds (VOCs) detected in field-equipment blank samples 


and respective environmental samples collected during sampling of the Quaternary aquifers. . . . . 35


10. 	 Summary of volatile organic compounds (VOCs) detected in field-equipment blank samples 


and respective environmental samples collected during sampling of the lower Tertiary aquifers.. . 36


11. 	 Summary of inorganic ground-water quality, Quaternary aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41


12. 	 Summary of inorganic ground-water quality, lower Tertiary aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 43


13. 	 Dissolved-solids concentrations in waters from Quaternary and lower Tertiary aquifers 


compared to U.S. Geological Survey salinity classification.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48


14. 	 Summary of pesticides detected in ground-water samples collected from Quaternary 


aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65


15. 	 Summary of pesticides detected in ground-water samples collected from lower Tertiary 


aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67


16. 	 Summary of volatile organic compounds (VOCs) detected in ground-water samples collected


 from Quaternary aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71


17. 	 Summary of volatile organic compounds (VOCs) detected in ground-water samples collected 


from lower Tertiary aquifers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

ix 

Conversion Factors and Datum 

Multiply By To obtain 

Length 

inch (in.) 25.4 millimeter (mm) 

inch (in.) 2.54 centimeter (cm) 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

Volume 

liter (L) 33.82 ounce (oz) 

milliliter (mL) 0.0338 ounce (oz) 

Flow rate 

gallon per minute (gal/min) 0.06309 liter per second (L/s) 

Temperature can be converted to degrees Fahrenheit (°F) or degrees Celsius (°C) as follows: 

°F = 9/5 (°C) + 32 

°C = 5/9 (°F - 32) 

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29). 

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD27). 

Abbreviated water-quality units used in this report: 

Ci curie 

mg/L milligram per liter 

μg/L microgram per liter 

μS/cm microsiemens per centimeter at 25 degrees Celsius 

pCi/L picocuries per liter 

TU tritium units 
x 

Abbreviations and acronyms used in this report:


ΑΑ

ΑL 

ΑΜCL 

ΑSΤ

BLM 

BTEX 

CaCO3 

DO 

DOC 

GC/MS 

GFAA 

H 

3H 

HAL 

ICP 

LRL 

MCL 

MDC 

MRL 

MS 

NAWQA 

NIST 

NWQL 

PVC 

QA/QC 

QC 

RPD 

RSD5 

SMCL 

TIC 

USEPA 

USGS 

UV 

VOC 

YRB 

atomic absorption 

Action Level 

Alternate Maximum Contaminant Level 

above-ground storage tank 

Bureau of Land Management 

benzene, toluene, ethylxylene, and xylenes 

calcium carbonate 

dissolved oxygen 

dissolved organic carbon 

gas chromatography/mass spectrometry 

graphite furnace atomic absorption spectrophotometry 

hydrogen 

tritium 

Health Advisory Level 

inductively-coupled plasma 

laboratory reporting level 

Maximum Contaminant Level 

minimum detectable concentration 

minimum reporting level 

mass spectrometry 

National Water-Quality Assessment 

National Institute for Standards and Technology 

National Water Quality Laboratory of U.S. Geological Survey 

polyvinyl chloride 

quality assurance/quality control 

quality control 

relative-percent difference 

risk-specific dose at 10-5 cancer risk 

Secondary Maximum Contaminant Level 

tentatively identified compound 

U.S. Environmental Protection Agency 

U.S. Geological Survey 

ultraviolet 

volatile organic compound 

Yellowstone River Basin 
Water-Quality Characteristics of Quaternary 

Unconsolidated-Deposit Aquifers and Lower Tertiary 

Aquifers of the Bighorn Basin, Wyoming and Montana, 

1999-2001 

By Timothy T. Bartos, Cheryl A. Eddy-Miller, Jodi R. Norris, Merry E. Gamper, and Laura L. Hallberg 

Abstract 

As part of the Yellowstone River Basin National Water 

Quality Assessment study, ground-water samples were collected from Quaternary unconsolidated-deposit and lower Tertiary aquifers in the Bighorn Basin of Wyoming and Montana 

from 1999 to 2001. Samples from 54 wells were analyzed for 

physical characteristics, major ions, trace elements, nutrients, 

dissolved organic carbon, radionuclides, pesticide compounds, 

and volatile organic compounds (VOCs) to evaluate current 

water-quality conditions in both aquifers. 

Water-quality samples indicated that waters generally 

were suitable for most uses, and that natural conditions, rather 

than the effects of human activities, were more likely to limit 

uses of the waters. Waters in both types of aquifers generally 

were highly mineralized, and total dissolved-solids concentrations frequently exceeded the U.S. Environmental Protection 

Agency (USEPA) Secondary Maximum Contaminant Level 

(SMCL) of 500 milligrams per liter (mg/L). Because of generally high mineralization, waters from nearly one-half of the 

samples from Quaternary aquifers and more than one-half of the 

samples from lower Tertiary aquifers were not classified as 

fresh (dissolved-solids concentration were not less than 

1,000 mg/L). The anions sulfate, fluoride, and chloride were 

measured in some ground-water samples at concentrations 

greater than SMCLs. Most waters from the Quaternary aquifers 

were classified as very hard (hardness greater than 180 mg/L), 

but hardness varied much more in waters from the lower Tertiary aquifers and ranged from soft (less than 60 mg/L) to very 

hard (greater than 180 mg/L). 

Major-ion chemistry varied with dissolved-solids concentrations. In both types of aquifers, the predominant anion 

changes from bicarbonate to sulfate with increasing dissolvedsolids concentrations. Samples from Quaternary aquifers with 

fresh waters generally were calcium-bicarbonate, calciumsodium-bicarbonate, and calcium-sodium-sulfate-bicarbonate 

type waters, whereas samples with larger concentrations generally were calcium-sodium-sulfate, calcium-sulfate, or sodiumsulfate-type waters. In the lower Tertiary aquifers, samples 

with fresh waters generally were sodium-bicarbonate or 

sodium-bicarbonate-sulfate type waters, whereas samples with 

larger concentrations were sodium-sulfate or calcium-sodiumsulfate types. 

Concentrations of most trace elements in both types of 

aquifers generally were small and most were less than applicable USEPA standards. The trace elements that most often did 

not meet USEPA secondary drinking-water standards were iron 

and manganese. In fact, the SMCL for manganese was the most 

frequently exceeded standard; 68 percent of the samples from 

the Quaternary aquifers and 31 percent of the samples from the 

lower Tertiary aquifers exceeded the manganese standard. 

Geochemical conditions may control manganese in both aquifers as concentrations in Quaternary aquifers were negatively 

correlated with dissolved oxygen concentrations and concentrations in lower Tertiary aquifers decreased with increasing pH. 

Elevated nitrate concentrations, in addition to detection of 

pesticides and VOCs in both aquifers, indicated some effects of 

human activities on ground-water quality. Nitrate concentrations in 36 percent of the wells in Quaternary aquifers and 

28 percent of the wells in lower Tertiary aquifers were greater 

than 1 mg/L, which may indicate ground-water contamination 

from human sources. The USEPA drinking-water Maximum 

Contaminant Level (MCL) for nitrate, 10 mg/L, was exceeded 

in 8 percent of samples collected from Quaternary aquifers and 

3 percent from lower Tertiary aquifers. Nitrate concentrations 

in Quaternary aquifers were positively correlated with the percentage of cropland and other agricultural land (non-cropland), 

and negatively correlated with rangeland and riparian land. In 

the lower Tertiary aquifers, nitrate concentrations only were 

correlated with the percentage of cropland. 

Concentrations of some naturally occurring radionuclides 

exceeded USEPA primary drinking-water standards. Grossalpha activities in 9 of 24 samples from Quaternary aquifers and 

6 of 26 samples from lower Tertiary aquifers were larger than 

the USEPA MCL of 15 picocuries per liter (pCi/L). Uranium 

concentrations were greater than the MCL of 30 micrograms 
2 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

per liter (μg/L) in 2 samples from Quaternary aquifers. Radon 

concentrations generally were large in samples from both types 

of aquifers. All samples from Quaternary aquifers and all but 

2 samples from the lower Tertiary aquifers had concentrations 

larger than the proposed MCL of 300 pCi/L. One sample from 

the lower Tertiary aquifers had a radon concentration larger 

than the proposed alternative MCL of 4,000 pCi/L. 

Organic compounds (pesticide compounds and VOCs), 

which generally are indicators of effects from human activities 

on ground-water quality, were detected in both types of aquifers. At least one pesticide compound was detected in 15 of 

25 well samples from Quaternary aquifers and in 4 of 29 well 

samples from lower Tertiary aquifers. Most detections in both 

types of aquifers were herbicides or herbicide breakdown 

products—only one insecticide was detected. All pesticide concentrations were much smaller than applicable USEPA standards and most measured concentrations were at trace levels 

(less than 0.1 μg/L). Most of the pesticides detected in ground 

water in both types of aquifers are commonly associated with 

agriculture. However, the detection frequency of some pesticide compounds in ground water did not necessarily match frequency of use in the Bighorn Basin. Prometon and tebuthiuron, 

which were among the most frequently detected pesticides, 

were not used exclusively for agricultural purposes. 

VOCs were detected in both types of aquifers and more 

frequently in Quaternary aquifers. At least one VOC was 

detected in samples from 21 of 25 wells in Quaternary aquifers 

and from 14 of 29 wells in lower Tertiary aquifers. Nine different VOCs were detected in samples from the Quaternary aquifers, six of which commonly are associated with gasoline. The 

VOCs detected in lower Tertiary aquifers were different from 

those detected in Quaternary aquifers as only two detections in 

lower Tertiary aquifers were of gasoline compounds. All concentrations were much smaller than USEPA MCLs. In fact, 

most detected VOC concentrations were smaller than the laboratory reporting level and the lowest laboratory calibration standard. The relatively high frequency of VOC detection in both 

aquifers was unexpected and may be attributable to use of very 

sensitive analytical methods with very low laboratory reporting 

levels. Despite very stringent quality-assurance/quality-control 

procedures, some very low VOC detections may be attributable 

to random sample contamination. 

Introduction 

The U.S. Geological Survey (USGS) began full implementation of the National Water-Quality Assessment (NAWQA) 

Program in 1991. Long-term goals of the program are to 

describe status and trends in the quality of the Nation’s surfaceand ground-water resources and to determine natural and 

human factors that affect water quality (Gilliom and others, 

1995). 

The Yellowstone River Basin (YRB) NAWQA study 

began in 1997. Three ground-water studies were conducted as 

part of the larger YRB NAWQA study. Two of the studies were 

NAWQA studies known as subunit surveys. Subunit surveys 

are designed to provide an assessment of current water-quality 

conditions in major aquifers by analyzing well samples for a 

wide variety of constituents. 

Because of the size of the YRB study area (about 

70,000 square miles), a smaller area (the Bighorn Basin) within 

the YRB study area boundary (fig. 1) was selected to conduct 

two subunit surveys. Shallow aquifers in the Bighorn Basin 

were selected for study because rural residents in the basin without access to public drinking-water supplies commonly use 

them for domestic purposes. These aquifers also are frequently 

used for stock supplies. Shallow aquifers most frequently used 

by rural residents occur in unconsolidated deposits of Quaternary age and sedimentary rocks of lower Tertiary age. Therefore, subunit surveys were conducted of Quaternary unconsolidated-deposit aquifers (“Quaternary aquifers”) and lower 

Tertiary aquifers. Quaternary aquifers, primarily composed of 

sand and gravel interbedded with finer-grained silt and clay, 

have a small extent and occur mostly as alluvium or terrace 

deposits within and adjacent to narrow valleys along streams in 

the Bighorn Basin. In contrast, lower Tertiary aquifers are wide 

in extent and are composed primarily of sandstone beds interbedded with fine-grained sedimentary rocks. The areal extent 

of Quaternary aquifers coincides with much of the rural population and irrigated cropland, making these aquifers particularly 

susceptible to human activities at the land surface. In addition, 

Quaternary aquifers directly overlie lower Tertiary aquifers in 

many areas, and the two aquifers are likely in hydraulic connection in some areas. 

Ground-water samples were collected from the Quaternary 

and lower Tertiary aquifers in the Bighorn Basin of Wyoming 

and Montana from 1999 to 2001. Samples from 54 wells were 

analyzed for physical characteristics, major ions, trace elements, nutrients, dissolved organic carbon (DOC), radionuclides, pesticide compounds, and volatile organic compounds 

(VOCs) to evaluate current water-quality characteristics in both 

aquifers. Historical ground-water-quality data were available 

for both aquifers, but most analyses were for major ions and a 

small number of other constituents; therefore, data collected 

from both studies should provide a broader description of current ground-water-quality in both aquifers. 

Purpose and Scope 

This report describes current (1999-2001) ground-water 

quality characteristics in Quaternary and lower Tertiary aquifers in the Bighorn Basin part of the Yellowstone River Basin 

NAWQA study unit. Results are presented for samples from 

24 new wells and one preexisting well in Quaternary aquifers 

(sampled October 1999 to March 2001) and 29 preexisting 

wells in lower Tertiary aquifers (sampled March 2000 to 

June 2001) that were analyzed for a variety of constituents. 
Introduction 3 

111° 110° 109° 108° 107° 106° 105° 104° 

47° 

46° 

45° 

44° 

43° 

Kalispell 

Helena 

Yellowstone 

National 

Park 

Cheyenne 

Riverton 

Billings 

Fort Peck 

INDEX 

MAP 

Casper 

MONTANA 

WYOMING 

NORTH 

DAKOTA 

MONTANA 

WYOMING 

N

O

RT

H

AK

O

TA 

S

O

U

T

H DA

Clarks River 

D

K

O

TA 

ID 

Wind 

AH

O

Boundary of Worland Yellowstone 

National Park 

Yellowstone 

Yellowstone

 Lake 

Ocean Boysen

Bighorn Basin

Lake Reservoir boundary 

Bighorn Lake Sheridan 

Red Tongue River 

Reservoir 

River 

Missouri 

ighorn 

River 

River 

Tongue 

wde

Shoshone 

Lodge 

River 

B

Po

r 

River 

River 

Fork 

Lander 

Billings Livingston 

Miles 

City 

Cody 

Lander

Glendive 

Gillette 

Riverton 

study area

boundary 

Yellowstone River Basin 

NAWQA study unit

48° 

Base modified from U.S. Geological Survey 0 20 40 60 80 100 KILOMETERS

digital data, 1:2,000,000, 1972


Albers Equal-area Conic projection


Standard parallels 29°30′ and 45°30′,


central meridian -107°30′

Figure 1. Location of the Bighorn Basin study area in relation to the Yellowstone River Basin NAWQA study unit, 

Wyoming, Montana, and North Dakota. 

0 20 40 60 80 100 MILES
4 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

 Water-quality results presented in this report include 

physical characteristics (water temperature, pH, turbidity, dissolved oxygen, specific conductance, and alkalinity), major 

ions, trace elements, nutrients, DOC, radionuclides (grossalpha activity, gross-beta activity, radon, tritium, uranium, and 

three isotopes of radium), pesticides, and VOCs. Results of tritium analyses were used to characterize the age of water from 

the two types of aquifers. 

Acknowledgments 

The authors appreciate the assistance of many individuals 

and organizations in the completion of both aquifer subunit surveys. Many private landowners granted permission for installation of wells and collection of ground-water-quality samples. 

Zig Napkora, Victor Trickey, and Kenneth Hanify, Bureau of 

Land Management (BLM), helped to obtain permission to 

install monitoring wells or sample existing wells on BLM lands. 

Mike Bies (BLM) helped to locate drilling locations on BLM 

lands so that historical and cultural resources would not be disturbed. Tom Gustafson, Natural Resources Conservation Service, provided descriptions of soils near sampled wells. The 

Ground-water Information Center, Montana Bureau of Mines 

and Geology and Montana Tech of the University of Montana, 

provided information describing wells in Montana. 

Acknowledged for their assistance with obtaining permission to install or sample wells on their respective managed or 

owned lands are: John Lawson, Rick Clark, and Bruce Pedersen 

(Bureau of Reclamation); Dave Hunt (Wyoming Game and 

Fish Commission); Jim Darling (Montana Fish, Wildlife, and 

Parks); Lyle Bjornestad (University of Wyoming, Powell 

Research and Extension Center); Frank Page, Robin Perdue, 

and Christine Algarme (Park County Engineer’s Office, Wyoming); Gary Collins (Tribal Water Engineer, Shoshone and 

Arapaho Tribes, Wind River Indian Reservation); Vick Struby, 

Joe Holloway, and Martin Kidner (Wyoming Department of 

Transportation); Paul Rasmussen (Bench Canal Company/ 

Greybull Valley Irrigation District); and Michael W. Donnell 

(Worland City Engineer). 

Finally, we thank USGS colleagues Peter R. Wright and 

Jon P. Mason for their extraordinary assistance with site establishment and collection of ground-water samples, Ron Zelt 

(USGS) for providing geographic information system assistance throughout both subunit surveys, and Suzanne C. Roberts 

for preparation of illustrations and Emily A. Sabado for editorial assistance. 

Description of Study Area 

This section of the report describes the geographic, physiographic, geologic, and hydrogeologic settings of the Bighorn 

Basin. Ground-water use and climate within the study area also 

are described. 

Geographic, Physiographic, and Geologic Setting 

The name Bighorn Basin can be used to refer to both a 

structural basin and a surface drainage basin. The geographic 

extent of the structural basin and a portion of the drainage basin 

generally coincide and both can be used to define the basin. In 

this report, all use of the name Bighorn Basin refers to the structural basin. The boundary or outline of the study area within the 

basin was selected to generally coincide with exposures of Paleozoic rocks that flank and define the structural basin. 

Most of the Bighorn Basin study area lies in the Middle 

Rocky Mountains physiographic province (labeled “B” in 

fig. 2) although a small part in the north lies in the unglaciated 

Missouri Plateau section of the Great Plains Province (labeled 

“A2” in fig. 2) (Fenneman and Johnson, 1946). The Middle 

Rocky Mountains Province is characterized by widely varying 

landforms, ranging from intermontane basins (for example, 

Bighorn Basin) to high plateaus and mountain ranges, whereas 

the unglaciated Missouri Plateau section is characterized primarily by gently rolling topography. The reader is referred to Zelt 

and others (1999) for a more thorough description of the physiography of the Yellowstone River Basin NAWQA study unit 

area, including the Bighorn Basin area. 

The Bighorn Basin study area in Wyoming is primarily 

drained by the perennial Bighorn River and its tributaries. The 

Yellowstone River and its tributaries (including the Bighorn 

River) drain the Montana part of the study area (fig. 1). Most 

perennial streams in the study area originate in mountainous 

areas and the quantity of streamflow is primarily dependant 

upon snowmelt in the mountains (Peterson and others, 1987). 

Ephemeral or intermittent streams primarily originate in the 

structural basins; flow in ephemeral drainages is primarily in 

direct response to precipitation, and flow in intermittent streams 

is primarily seasonal surface runoff and some ground-water discharge (Peterson and others, 1987). 

The Bighorn Basin is an intermontane basin in the Rocky 

Mountain foreland formed during the Laramide orogeny (Late 

Cretaceous to early Tertiary Period). Folded and faulted Paleozoic and Mesozoic rocks form the flanks of adjacent mountain 

ranges and anticlinal uplifts that surround most of the basin 

(figs. 2 and 3). Many geologic structures (primarily anticlinal) 

and associated rocks comprising the flanks of the basin are 

important sources of oil and gas. The basin center is covered by 

relatively flat-lying rocks of early Tertiary age (Paleocene and 

Eocene). The Pryor Mountains to the northeast, the Bighorn 

Mountains to the east, the Owl Creek Mountains to the south, 

and the Beartooth Mountains to the northwest bound the basin 

(fig. 2). The Absaroka Range bounds the western margin of the 

basin and some of the Bighorn Basin sedimentary rock 

sequence is partially concealed beneath Absaroka volcanic 

rocks (Love, 1939; Thom, 1952; Blackstone, 1986) (fig. 3). 

The structural northern boundary of the basin is located in Montana in a relatively “open,” topographically low, folded and 

faulted zone known as the Nye-Bowler lineament (Wilson, 

1936; Eckleman and Poldervaart, 1957; Thomas, 1965) (fig. 2). 
Description of Study Area 5

Figure 2. Generalized geology and physiographic provinces, Bighorn Basin study area and Yellowstone River Basin NAWQA

study unit, Wyoming, Montana, and North Dakota.

Geology modified from Clayton, 1980; Love and

Christiansen, 1985; and Ross and others, 1955

Physiographic provinces modified from

Fenneman and Johnson, 1946

MONTANA

WYOMING

M

O

N

TA

N

A

N. D

A

KOTA

111° 104° 110° 109° 108° 107° 106° 105°

48° 

47° 

46° 

45° 

44° 

43° 

Base modified from U.S. Geological Survey

digital data, 1:2,000,000, 1972

Albers Equal-area Conic projection

Standard parallels 29°30′ and 45°30′,

central meridian -107°30′ EXPLANATION

100 MILES

0 20 40 60 80 100 KILOMETERS

0 20 40 60 80

A1

A2

B

C

C

D

D

 Quaternary unconsolidated

 deposits

Geologic unit

Cretaceous sedimentary rocks

 Quaternary volcanic rocks Paleozoic and Mesozoic

 sedimentary rocks

 Tertiary sedimentary rocks Precambrian crystalline rocks

 Tertiary and Cretaceous intrusive

 and volcanic rocks

Boundary of physiographic

 province or section

 Great Plains Province

 Glaciated Missouri Plateau section

 Unglaciated Missouri Plateau section

 Middle Rocky Mountains Province

 Wyoming Basin Province

 Northern Rocky Mountains Province

Physiographic province

A

A1

A2

B
WEST 

A

5,000 

10,000 

Elevation,

 in feet above 

NGVD 29 

Absaroka Range 

Eocene volcanic and intrusive rocks 

Thorofare Plateau Yellow Mtn. 

Da

0 

-5,000 

-10,000 -15,000 

Mo

Figure 3. Schematic geologic section across the central part of the Bighorn Basin in Wyoming. See inset for location of geologic section. 

Oligocene(?

at 9

Willwood Formation 

Willwood Formation 

Tatman 

Formation Squaw Buttes 

Fort Union Formation 

Cretaceousu

ndivided Precambrianb as

Mesozoic Precambrian basemen 

o z 

-Paleozoicundivided t 

Mes 

ic

ozo 

n

v ic-Pal i e o

und

i

ivided 

Cretaceous

u

d

ded 

? 

? 

? 

0 5 10 15 20 MILES

Folded and faulted 

Paleozoic and Mesozoic rocks 

Horizontal scale 

VERTICAL EXAGGERATION X8 reverse fault 

Oregon Basin 
Description of Study Area 7 

The Bighorn Basin is highly asymmetric, with the structurally 

deepest part of the basin located close to the western 

margin—an area where the basin floor is bounded by the steeply 

westward-dipping Oregon Basin reverse fault (fig. 3). The sedimentary rock sequence is thickest in the deepest part of the 

basin, and depth to the Precambrian basement is greater than 

20,000 feet (ft) below NGVD 29 along the basin axis southeast 

of Cody (Jensen, 1972; Blackstone, 1993). 

The geology of the study area is further described for the 

Tertiary and Quaternary geologic units that contain the aquifers 

of interest for this study. Lower Tertiary rocks are areally 

extensive (fig. 4), and are composed primarily of fine- to 

coarse-grained sandstone beds interbedded with shale and other 

fine-grained rocks, although some conglomerate and coal are 

locally present as well. Individual sandstones are sheet or channel sandstones that vary widely in geometry and thickness in the 

Bighorn Basin (for example, Neasham and Vondra, 1972; 

Bown, 1975). These sandstones are assigned to the Paleoceneage Fort Union Formation (sometimes referred to as the Polecat 

Bench Formation) and the early Eocene-age Willwood Formation. Many channel sandstones in the Willwood Formation are 

ribbon sandstones (also known as “shoestring” sandstones) of 

very small width and thickness (generally less than about 10 ft 

in thickness) (Kraus, 2001, and references therein). The Fort 

Union Formation is primarily exposed along the Bighorn Basin 

margins in Wyoming and throughout the Montana part of the 

study area, whereas the Willwood Formation is exposed 

throughout the central part of the basin, primarily in Wyoming 

(fig. 4). The Fort Union Formation unconformably underlies 

the Willwood Formation around the margins of the Bighorn 

Basin, although the two formations are probably conformable in 

the structurally deepest parts of the basin (Keefer and others, 

1998). The Fort Union and Willwood Formations are very similar in most characteristics and it is very difficult to distinguish 

one formation from another, especially in the subsurface 

(Keefer and others, 1998). In most locations in the Bighorn 

Basin, the Willwood Formation is highly variegated, but the 

presence or absence of this characteristic is not a criterion to differentiate it from the underlying Fort Union Formation, even 

though many earlier investigators used this characteristic to differentiate the two formations in places (Keefer and others, 

1998, and references therein). 

Sediments comprising rocks of both Tertiary formations 

accumulated during subsidence of the Bighorn Basin during the 

Laramide orogeny. Rocks of the Fort Union and Willwood Formations are continental in origin and were deposited primarily 

in fluvial and alluvial environments, although lacustrine and 

paludal sediments also were deposited in some areas (Van 

Houten, 1944; Neasham and Vondra, 1972; Rea and Barlow, 

1975; Hickey, 1980; Gingerich, 1983; Hickey and Yuretich, 

1997; Davies-Vollum and Kraus, 2001). Based on measured 

surface sections, the proportion of sandstone to fine-grained 

rocks in the Fort Union Formation (and by inference, the Willwood Formation) varies greatly by location and sequence 

examined (Roberts, 1998, and references therein). 

Reported thicknesses of both Tertiary formations vary 

depending on location and whether measured surface sections 

or subsurface data are used. Estimates of maximum thickness 

of the Fort Union Formation vary widely and, using measured 

surface sections or subsurface methods, range from 1,000 to 

1,500 ft along the east and south basin margins to nearly 7,500 

to 11,500 ft in the structurally deepest parts of the basin along 

the west or northwest basin margins (Hewett, 1926; Stow, 1938; 

Rogers and others, 1948; Pierce, 1948; Moore, 1961; Horn, 

1963; Hickey, 1980; Keefer and others, 1998; Taylor, 1998). 

Estimates of the maximum thickness of the Willwood Formation in selected locations range from about 800 ft to nearly 

5,000 ft (Van Houten, 1944; Neasham and Vondra, 1972; Gingerich, 1983; Keefer and others, 1998). The formations generally thicken from east to west, and the maximum thickness 

occurs in the structurally deepest parts of the basin along the 

western margin (fig. 3). 

Unconsolidated deposits primarily are composed of sand 

and gravel interbedded with finer-grained sediments such as silt 

and clay, although coarser deposits such as cobbles and boulders can occur locally. These deposits have a small areal extent 

and primarily occur as alluvium or terrace deposits along narrow valleys and in adjacent upland areas, and along streams and 

rivers in the Bighorn Basin (fig. 5); however, some deposits 

(primarily in the northwestern part of the basin) are glaciofluvial in origin. Terrace deposits of the Bighorn Basin are present 

in many different terrace levels alongside rivers draining the 

basin and in adjacent upland areas. The terrace sequence has 

been studied by many investigators because the sequence is 

considered a model of late Cenozoic erosional history, as well 

as a model to study the fluvial history and mechanics of basin 

rivers (Mackin, 1937, 1947; Moss and Bonini, 1961; Ritter, 

1967, 1975; Palmquist, 1978, 1979, 1983; Reheis, 1982; Ritter 

and Kauffman, 1983). Total thickness of unconsolidated 

deposits in the Wyoming portion of the basin can be as much as 

100 ft, but total thicknesses are usually much less (Lowry and 

others, 1976, and references therein; Libra and others, 1981). 

Hydrogeologic Setting and Ground-Water Use 

Much of the population in the Bighorn Basin is rural, and 

a large percentage relies upon ground water for domestic use. A 

few public water supply systems obtain water from deep, highcapacity wells. In Wyoming, these deep public-supply wells 

often are completed in aquifers in karstic Paleozoic rocks. In 

contrast, the population in the Bighorn Basin not served by public water systems must use private domestic wells installed at 

relatively shallow depths to obtain water for domestic use. 

For economic reasons, most domestic wells are installed at 

shallow depths (generally less than 500 ft deep)—most commonly in aquifers in Cenozoic (Tertiary and Quaternary in age) 

rocks because they are present at or near land surface throughout much of the basin. A large number of stock wells also are 

completed in aquifers in Cenozoic rocks. 
8 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Figure 4. Location of Tertiary-age Willwood and Fort Union Formations and sampled wells in the Bighorn Basin study area,

Wyoming and Montana.

INDEX MAP

Helena

Cheyenne

Billings

WYOMING

MONTANA

Bighorn Basin

study area

River

River

Stillwater River

Yellowstone

Yellowstone

Clarks

Fork

Creek

Rock

Bighorn

Nowood

River

River

Greybull

Shoshone

River

River

Creek

Gooseberry

R

Wood

Boysen

Reservoir

Bighorn Lake

 Buffalo

 Bill

Reservoir

Cooney

Reservoir

Tensleep

Billings

Powell

Red

Lodge

Lovell

Greybull

Basin

Meeteetse

Emblem

Cody

Worland

Thermopolis

14

434

16

16

20

20

212

I-90

310

Alt

14

120

120

MONTANA

WYOMING

Carbon

County

Big Horn

County

Washakie

County

Hot Springs

County

Natrona

County

Park

County

Stillwater

County

109°00′

108°30′

107°30′

45°30′

45°00′

44°30′

44°00′

43°30′

109°30′

108°00′

3

4

5

7

8

9

12 11

19

22

15 14

16 17

20

18

24

23

25 26

27

29

28 30

10

13

6

2

1

28

Fort Union Formation outcrop

Willwood Formation outcrop

EXPLANATION

Well location and subunit survey (SUS2) number

0

0 20 40 MILES

20 40 60 KILOMETERS

Base modified from Digital Chart of the World

digital data, 1:1,000,000, 1993

Albers Equal-area Conic projection

Standard parallels 43°00′ and 47°00′

central meridian -107°30′
9 

River 

River 

Yellowstone 

Yellowstone 

Clarks 

Fork 

Creek 

Rock 

Bighorn 

Nowood 

River 

River 

Gr eybull 

Shos h o n e 

River 

River 

Creek 

G o se b e r r y 

R 

Wood 

S t i l l w a t er River 

o 

Billings 

16 

Carbon 

County 

Washakie 

Park 

County 

1 

11 

27 

30 

28 

7 

Description of Study Area 

109°30′

MONTANA 

Helena Stillwater 109°00′ I-90

Billings

Cooney 6

45°30′ Reservoir 

212 

Bighorn Basin WYOMING 

study area 

5 Cheyenne 

108°30′ INDEX MAP 

MONTANA 

Red 

Lodge 

45°00′

WYOMING 

Bighorn Lake

310 17 108°00′

4 

Lovell Alt 

8 14

3 16 9 Powell 

120 

Cody County 

Emblem Greybull 14 

44°30′

 Buffalo 20 16 18 

Bill 2 

Reservoir 14 19 Big Horn 

Basin 

29 

County 

107°30′

10 

434 

Meeteetse 

13 25 

44°00′ Worland Tensleep 

Hot Springs 

County County 24 

Base modified from Digital Chart of the World 120 

digital data, 1:1,000,000, 1993 12 

Albers Equal-area Conic projection 

Standard parallels 43°00′ and 47°00′

central meridian -107°30′ Thermopolis 

22 

0 20 40 60 KILOMETERS

43°30′

0 20 40 MILES 20 Natrona 

EXPLANATION County 

Boysen Quaternary unconsolidated deposits Reservoir 

22 Well location and subunit survey (SUS1) number 

Figure 5. Location of Quaternary unconsolidated deposits and sampled wells in the Bighorn Basin study area, Wyoming 

and Montana. 
10 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Aquifers in Cenozoic rocks in the Bighorn Basin were selected 

for study because of their widespread use as a source of domestic water for the rural population without access to a public 

water supply and because of their occurrence and use at relatively shallow depths. Most frequently, these wells are completed in Quaternary unconsolidated-deposit and lower Tertiary 

bedrock aquifers. 

Unconsolidated-deposit aquifers in sediments of Quaternary age (“Quaternary aquifers”) locally can be highly productive and are the source of water for many shallow wells in the 

Bighorn Basin. Many wells completed in Quaternary aquifers 

are located close to streams and rivers because deposits commonly are less than 1 mile wide near streams in the basin. 

Along the floodplains, wells completed in alluvium are likely in 

hydraulic connection with streams and rivers. Well yields in 

Quaternary aquifers are directly related to the size and sorting 

of materials comprising the deposits, as well as the saturated 

thickness of the deposits. In places, well yields are high 

because of large saturated thicknesses and very coarse deposits. 

Reported yields for wells completed in Quaternary aquifers 

range from less than 5 to 600 gallons per minute (gal/min) but 

most yields are less than 10 gal/min (Lowry and others, 1976; 

Cooley and Head, 1979a, 1979b, 1982; Plafcan and others, 

1993). Ground-water flow in most Quaternary aquifers is 

towards rivers or in the direction of streamflow (Levings, 1986; 

Plafcan and others, 1993; Susong and others, 1993; Plafcan and 

Ogle, 1994). The areal extent of Quaternary aquifers coincides 

with much of the rural population and irrigated cropland in the 

Bighorn Basin, making these aquifers particularly susceptible 

to contamination from human activities at the land surface. 

The chemical evolution of waters in some Quaternary 

aquifers is likely very complex. Recharge to many Quaternary 

aquifers is not only from precipitation, but also from infiltration 

of diverted surface water from unlined irrigation canals and 

ditches as well as from water applied to fields (Swenson, 1957; 

Robinove and Langford, 1963; Cooley and Head, 1979a, 

1979b, 1982; Plafcan and others, 1993). Most unconsolidated 

terrace deposits in the Bighorn Basin were not saturated prior to 

irrigation, indicating that recharge of diverted surface water is 

likely the dominant source of recharge (Swenson, 1957). Water 

levels in many terrace deposits are directly related to irrigation 

diversions. During the irrigation season, water levels in these 

deposits, at some locations, can be the same elevation as water 

levels in unlined irrigation canals and ditches (Robinove and 

Langford, 1963; Plafcan and others, 1993). Water levels in terrace deposit aquifers typically begin to rise some time after irrigation begins (generally mid April in the Bighorn Basin in 

Wyoming), continue to rise after irrigation ceases (generally 

mid- to late-October in Wyoming) as surface soils continue to 

drain, and reach maximum water levels in December (Plafcan 

and others, 1993). Consequently, water quality in these Quaternary aquifers is likely to vary during the year in response to 

application of diverted surface water, variation of surface-water 

quality throughout the irrigation season, and subsequent infiltration and percolation of these waters. Evaluation of possible 

ground-water quality changes in response to the irrigation 

water-quality changes was beyond the scope of this study. Only 

one ground-water sample was collected from each well during 

the study of Quaternary aquifers, so temporal water-quality 

variability was not evaluated. 

Individual sandstone beds in the Fort Union and Willwood 

Formations comprise the main water-bearing units in lower 

Tertiary aquifers; in many cases, these beds may be relatively 

thin, lenticular, and discontinuous. Sandstone beds comprising 

the aquifers are interbedded and commonly separated by finegrained rocks with low hydraulic conductivities such as shale, 

mudstone, or siltstone. Consequently, water in the sandstone 

aquifers is likely under varying degrees of confinement and 

hydraulic isolation. Water-table conditions may exist in the 

shallowest sandstones, and semiconfined or confined conditions are likely to exist in deeper sandstones. In general, finegrained sedimentary rocks in both formations are not likely to 

yield sufficient quantities of water to be considered aquifers, 

even though they may be saturated, and static water levels in 

wells completed in the fine-grained rocks may be the same as in 

adjacent beds of sandstone. Well yields in both the Willwood 

and Fort Union Formations are directly related to the number 

and thickness of sandstone lenses or beds (“aquifers”) penetrated. Typical well yields in both the Willwood and Fort Union 

Formations range from 1 to 20 gal/min (Libra and others, 1981; 

Plafcan and others, 1993; Susong and others, 1993; Plafcan and 

Ogle, 1994; Robinove and Langford, 1963). Well yields of as 

much as 30 gal/min are not uncommon (Lowry and others, 

1976; Libra and others, 1981; Plafcan and others, 1993). Some 

well yields higher than 30 gal/min have been reported (Libra 

and others, 1981; Plafcan and others, 1993). Even though they 

are not highly permeable, lower Tertiary aquifers in the Bighorn 

Basin are an important source of water because of their wide 

areal extent at or near the land surface, and because enough 

water can usually be obtained for domestic or stock purposes 

(even though quality varies widely). 

Recharge to lower Tertiary aquifers is likely primarily 

from areal infiltration and percolation of precipitation, as well 

as localized recharge beneath ephemeral drainages during periods of runoff. Recharge also is possible in areas where lower 

Tertiary aquifers are overlain by saturated Quaternary unconsolidated deposits. 

Potentiometric-surface maps of lower Tertiary aquifers in 

the Bighorn Basin have not been constructed and regional 

ground-water flow has not been described. The discontinuous 

and lenticular characteristics of the sandstones comprising the 

aquifers makes it difficult to create and interpret such maps. In 

addition, the sandstones are interbedded with fine-grained rocks 

so the amount of hydraulic connection between individual sandstone aquifers is difficult to assess. However, the authors suspect that ground-water flow in the shallow aquifers (including 

most sampled during this study) is primarily local and related to 

topography with discharge occurring in some areas along 

streams adjacent to local recharge areas. The amount of 

regional ground-water flow and the relation between local 

ground-water flow and possible intermediate and regional 

ground-water flow is unknown. 
Description of Study Area 11 

The lower Tertiary aquifers sampled represented very little 

of the total thickness of either the Willwood or Fort Union Formations. The maximum depth of the sampled wells was less than

500 feet (most wells were less than 300 ft deep) and this represents just a part of the total thickness of both formations, which 

ranges from hundreds to thousands of feet as noted previously

and shown on fig. 3. Therefore, water-quality characteristics of

the lower Tertiary aquifers sampled represents near-surface conditions of aquifers in both formations, and water-quality characteristics of aquifers in deeper parts of both formations may be different. 

Water-quality samples were collected from three different

types of wells completed in Quaternary and lower Tertiary aquifers—domestic-supply wells, monitoring wells, and stock wells. 

In the Bighorn Basin, these wells are constructed in several different ways in both aquifers (fig. 6). In the Bighorn Basin, 

domestic wells are often completed in the same manner as stock 

wells, although different types of pumps often are used. Monitoring wells installed for the Quaternary aquifers subunit survey 

were completed only in Quaternary deposits (for example, wells 

M1 and M2, fig. 6) and with short screen intervals (typically 10

ft long). In some places, monitoring wells were installed in saturated unconsolidated Quaternary deposits that are not used, and 

would not necessarily be defined as aquifers because of very low

yield (less than 1 gal/min); however, the purpose of the study was 

to document water-quality conditions in saturated Quaternary

deposits, regardless of whether deposits were currently being

used. In addition, Quaternary deposits directly overlie other aquifers in the basin (most notably lower Tertiary aquifers because of

wide areal extent), and water in these deposits has the potential to 

move down to deeper aquifers at some locations. Domestic and

stock wells in the Bighorn Basin may be completed in one aquifer 

(for example, wells D1, D3, and D4, fig. 6) or in multiple aquifers 

in the same geologic formation (for example, well D2, fig. 6). 

Some domestic and stock wells may be completed in multiple 

aquifers in different geologic formations (for example, well D5, 

fig. 6); these types of wells were avoided when selecting existing 

wells for sampling. Domestic and stock wells in the basin commonly are completed in multiple aquifers to increase yields;

many wells in lower Tertiary aquifers must penetrate more than 

one sandstone lens or bed (each of which may be considered an

aquifer) to obtain sufficient yield. In addition, wells often are 

screened not only to aquifers that yield water, but also to finegrained materials separating aquifers (for example, well D5, 

fig. 6). These types of construction are common in the Bighorn 

Basin, and some wells sampled had both types of completion. 

D2 

M2 D3 D4 D5 

D1 

Terrace deposit 

aquifer M1 

Alluvial aquifer 

Sandstone aquifers 

Sandstone aquifers 

Not to scale EXPLANATION 

Quaternary unconsolidated deposits Water table in Quaternary

 unconsolidated deposits Sandstone in Willwood or Fort Union Formation Monitor well 

Fine-grained rock in Willwood or Fort Union Formation

 (claystone, mudstone, siltstone, or shale) Domestic or stock well 

Figure 6. Simplified schematic diagram showing relation of domestic, stock, and monitoring wells to hydrogeology. 
12 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Climate 

Climate in the Bighorn Basin study area varies, primarily 

with altitude (Martner, 1986). Precipitation is strongly affected 

by mountain ranges surrounding the Bighorn Basin and varies 

spatially because of orographic effects. Consequently, mean 

annual precipitation for 1971-2000 is much smaller in the central part of the basin (in Wyoming) than in the surrounding 

mountains (Western Regional Climate Center, 2003a). The climate of much of the study area is classified as desert (primarily 

the central part of the basin in Wyoming) or as a “steppe climate 

typical of semiarid grassland prairies” (Martner, 1986, p. 3). 

The mean annual temperature in Worland, Wyoming (within 

the area classified as desert) for 1971 to 2000 was 44.9 degrees 

Fahrenheit and the mean annual precipitation was 8.03 inches, 

but temperature and precipitation vary widely in the Bighorn 

Basin study area, depending upon the location and season 

(Western Regional Climate Center, 2003b). Estimated mean 

annual evaporation greatly exceeds mean annual precipitation 

in much of the study area; mean annual evaporation estimated 

from Class-A pans is greater than 55 inches per year in much of 

the Wyoming portion of the study area (Martner, 1986, p. 177, 

and references therein). Estimated mean annual potential 

evapotranspiration also exceeds precipitation in most of the 

study area in Wyoming for 1951 through 1980 and was about 

16 to 24 inches, based on the Thornthwaite method (Martner, 

1986, p. 182). The reader is referred to Zelt and others (1999) 

for a more detailed description of climate in the study area and 

the rest of the Yellowstone NAWQA study unit. 

Methods of Investigation 

Many methods were used in the collection and analyses of 

water-quality data for this study. This section describes the 

methods used for the collection of ancillary data and land use 

and land cover, statistical methods used in data analyses, site 

selection and well construction, collection of samples, and 

chemical analyses. The collection and analyses of qualityassurance and quality-control samples and the major-ion balances of the environmental samples also are described. 

Ancillary Data 

Ancillary data were collected for all wells and included 

descriptions of the sampling location, the well, the subsurface, 

and land use/land cover within a 500-meter (1,640-ft) radius 

surrounding the well. Data were collected in a nationally consistent and quantitative manner following NAWQA guidance 

provided in Koterba (1998). Requirements for ancillary data 

collection were designed to document activities that might 

affect shallow ground-water quality. 

Land Use and Land Cover 

Basinwide land use and land cover from the National Land 

Cover Database (U.S. Geological Survey, 2000) are shown on 

the Quaternary unconsolidated deposits in figure 7 and lower 

Tertiary rocks in figure 8. Figure 8 includes areas that directly 

overlie lower Tertiary rock and areas that have intervening Quaternary unconsolidated deposits. Rangeland (shrubland and 

herbaceous upland) vegetation was the most common land use 

and land cover overlying both Quaternary unconsolidated 

deposits (about 74 percent, fig. 7) and overlying lower Tertiary 

rocks (about 88 percent, fig. 8). Cropland—pasture/hay, row 

crops, small grains, and fallow lands (unused cropland at time 

of mapping)—was the next most common land use and land 

cover, overlying about 22 percent of Quaternary unconsolidated 

deposits and about 10 percent of lower Tertiary rocks. All 

remaining land-use and land-cover categories (water, urban/ 

developed land, barren land, forest, and wetlands) comprised 

less than about 4 percent of the land use and land cover overlying Quaternary unconsolidated deposits and less than 2 percent 

overlying lower Tertiary rocks. 

Because land use and land cover can influence the presence and distribution of constituents in ground water, land use 

and land cover were mapped at great detail within a 500-meter 

(m) radius around each well (appendix 1) using aerial photographs and onsite reconnaissance. Mapping was conducted 

using standardized NAWQA land-use and land-cover mapping 

procedures (Koterba, 1998). Many different land-use and landcover classification categories (appendix 1; Koterba, 1998) 

were used for mapping purposes, but these were generalized 

into six land-use and land-cover categories (table 1). 

Cropland (table 1) included row crops, small grains, fallow 

lands, and hayfields. Other agricultural land included pastures; 

corrals and other animal enclosures; and houses, trailers, 

garages, barns, parking lots, irrigation ditches, silos, and storage 

areas in agricultural areas. Rangeland was primarily open range 

that may or may not have been used for animal grazing at time 

of mapping. Riparian land use included open water (streams 

and lakes) and associated riparian vegetation (wetlands). Urban 

land use included all commercial businesses, schools, churches, 

municipal offices, post offices, firestations, parking lots, public 

access areas and parks, railroad tracks and associated right of 

ways, major roads and associated right of ways, and residential 

housing. The “other” land use category included barren land 

(typically badlands), mining (active and inactive sand and 

gravel pits; oil and gas wells and associated equipment), and 

other miscellaneous land uses that comprised a relatively small 

percentage of total land use within 500 m of the wells. 

Rangeland was the most abundant land use within 500 m 

of the wells in both subunit surveys, averaging about 28 percent 

for the Quaternary aquifers and about 49 percent for the lower 

Tertiary aquifers (table 1). Cropland was the second most abundant land use within 500 m of the wells in both subunit surveys, 

averaging about 27 percent for the Quaternary aquifers and 

about 23 percent for the lower Tertiary aquifers (table 1). 
Methods of Investigation 13 

EXPLANATION 

LAND COVER 

River 

River 

Stillwater River 

Yellowstone 

Yellowstone 

Clarks 

Fork 

Creek 

Rock 

Bighorn 

Nowood 

River 

River 

Gr eybull 

Shos h o n e 

River 

River 

Creek 

G o o se b e r r y 

R 

Wood 

Boysen

Reservoir 

Bighor n Lake 

Buf falo Bill 

Reservoir 

Cooney

Reservoir 

Billings 

Powell 

Red 

Lodge 

Lovell 

Greybull 

Basin 

Meeteetse 

Emblem 

Cody 

Worland 

Tensleep 

Thermopolis 

14 

434 

16 

16 

20 

20 

212 

I-90 

310 

Alt 

14 

120 

120 

MONTANA 

WYOMING 

Carbon 

County 

Big Horn 

County 

Washakie 

County 

Hot Springs 

County 

Natrona 

County 

Park 

County 

Stillwater 

County 

109°00′

108°30′

107°30′

45°30′

45°00′

44°30′

44°00′

43°30′

109°30′

108°00′

0 

0 20 40 MILES

20 40 60 KILOMETERS

National land cover data modified from 

U.S. Geological Survey, EROS Data Center, 2000 

Base modified from Digital Chart of the World 

digital data, 1:1,000,000, 1993 

Albers Equal-area Conic projection 

Standard parallels 43°00′ and 47°00′, 

central meridian -107°30′

Barren

 Row crops 

Forested upland (forested)

 Small grains 

Shrubland (rangeland)

 Fallow 

Herbaceous upland natural/

 semi-natural vegetation

 (rangeland) 

Herbaceous planted/

 cultivated (agricultural) 

Wetland 

Developed (urban)

 Pasture/hay 

Water 

Figure 7. Distribution of land use and land cover on Quaternary unconsolidated deposits in the Bighorn Basin, Wyoming 

and Montana. 
14 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

EXPLANATION 

LAND COVER 

River 

River 

StillwaterRiver 

Yellowstone 

Yellowstone 

Clarks 

Fork 

Creek 

Rock 

Bighorn 

Nowood 

River 

River 

Gr eybull 

Shos h o n e 

River 

River 

Creek 

G o o se b e r r y 

R 

Wood 

Boysen

Reservoir 

Bighor n Lake 

Buf falo Bill 

Reservoir 

Cooney

Reservoir 

Billings 

Powell 

Red 

Lodge 

Lovell 

Greybull 

Basin 

Meeteetse 

Emblem 

Cody 

Worland 

Tensleep 

Thermopolis 

14 

434 

16 

16 

20 

20 

212 

I-90 

310 

Alt 

14 

120 

120 

MONTANA 

WYOMING 

Carbon 

County 

Big Horn 

County 

Washakie 

County 

Hot Springs 

County 

Natrona 

County 

Park 

County 

Stillwater 

County 

Barren

 Row crops 

Forested upland (forested)

 Small grains 

Shrubland (rangeland)

 Fallow 

Herbaceous upland natural/

 semi-natural vegetation

 (rangeland) 

Herbaceous planted/

 cultivated (agricultural) 

Wetland 

Developed (urban)

 Pasture/hay 

Water 

109°00′

108°30′

107°30′

45°30′

45°00′

44°30′

44°00′

43°30′

109°30′

108°00′

20 40 MILES

0 20 60 KILOMETERS

0 

40 

National land cover data modified from 

U.S. Geological Survey, EROS Data Center, 2000 

Base modified from Digital Chart of the World 

digital data, 1:1,000,000, 1993 

Albers Equal-area Conic projection 

Standard parallels 43°00′ and 47°00′, 

central meridian -107°30′

Figure 8. Distribution of land use and land cover on or overlying lower Tertiary rocks in the Bighorn Basin, Wyoming 

and Montana. 
Methods of Investigation 15 

Table 1. Percent land use and land cover mapped within 500-meter radius of sampled wells 

Generalized land-use and land-cover categories 

Other 

agricultural 

Well Cropland land Rangeland Riparian Urban Other Total 

number (percent) (percent) (percent) (percent) (percent) (percent) (percent) 

Quaternary aquifers 

SUS1-1 12.4 6.6 55.4 25.6 0.0 0.0 100.0 

SUS1-2 32.7 8.2 14.9 44.2 0.0 0.0 100.0 

SUS1-3 89.2 10.8 0.0 0.0 0.0 0.0 100.0 

SUS1-4 27.1 12.1 38.7 22.0 0.0 0.0 100.0 

SUS1-5 11.5 34.2 8.4 44.5 1.4 0.0 100.0 

SUS1-6 28.0 22.9 0.0 26.9 17.8 4.4 100.0 

SUS1-7 77.8 15.8 0.0 0.0 0.0 6.4 100.0 

SUS1-8 81.0 19.0 0.0 0.0 0.0 0.0 100.0 

SUS1-9 63.8 14.1 20.7 0.0 0.0 1.5 100.0 

SUS1-10 0.0 20.1 49.5 30.5 0.0 0.0 100.0 

SUS1-11 0.0 33.2 40.0 25.0 0.0 1.9 100.0 

SUS1-12 0.0 2.8 61.7 35.5 0.0 0.0 100.0 

SUS1-13 0.0 2.3 50.5 22.9 0.0 24.3 100.0 

SUS1-14 10.6 28.7 21.8 38.9 0.0 0.0 100.0 

SUS1-16 39.1 11.2 33.1 16.6 0.0 0.0 100.0 

SUS1-17 43.5 12.7 0.0 0.0 38.1 5.7 199.9 

SUS1-18 81.6 12.5 0.0 0.0 5.9 0.0 100.0 

SUS1-19 0.0 0.3 23.0 76.7 0.0 0.0 100.0 

SUS1-22 10.4 11.8 44.6 22.4 11.0 0.0 100.0 

SUS1-24 18.4 0.0 50.0 28.2 0.0 3.5 100.0 

SUS1-25 0.0 4.1 0.0 19.7 75.5 0.7 100.0 

SUS1-27 0.0 6.6 66.9 26.5 0.0 0.0 100.0 

SUS1-28 30.5 4.6 12.6 25.2 0.0 27.1 100.0 

SUS1-29 12.0 2.0 22.9 62.2 0.0 0.8 100.0 

SUS1-30 0.0 0.0 84.8 12.6 2.6 0.0 100.0 

Average 26.8 11.9 28.0 24.2 6.1 3.1 

Lower Tertiary aquifers 

SUS2-1 0.0 45.7 9.8 0.0 0.0 44.4 199.9 

SUS2-2 0.0 63.3 18.2 18.5 0.0 0.0 100.0 

SUS2-3 47.9 10.9 38.2 0.0 0.0 3.0 100.0 

SUS2-4 17.2 36.2 15.4 29.9 1.3 0.0 100.0 

SUS2-5 8.2 0.0 88.1 0.0 3.7 0.0 100.0 

SUS2-6 0.0 0.0 95.3 0.0 0.0 4.8 100.0 

SUS2-7 0.0 0.0 80.5 18.2 1.3 0.0 100.0 

SUS2-8 82.0 18.0 0.0 0.0 0.0 0.0 100.0 

SUS2-9 0.0 36.9 63.1 0.0 0.0 0.0 100.0 

SUS2-10 30.9 19.9 23.1 9.5 16.7 0.0 100.0 

SUS2-11 85.4 8.0 0.0 0.0 0.0 6.6 100.0 

SUS2-12 20.1 8.0 45.9 26.0 0.0 0.0 100.0 

SUS2-13 25.9 0.0 61.5 0.0 0.0 12.6 100.0 

SUS2-14 53.6 33.1 13.3 0.0 0.0 0.0 100.0 

SUS2-15 58.3 12.2 29.5 0.0 0.0 0.0 100.0 

SUS2-16 7.8 5.2 60.2 26.6 0.2 0.0 100.0 
16 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 1. Percent land use and land cover mapped within 500-meter radius of sampled wells—Continued 

Generalized land-use and land-cover categories 

Other 

agricultural 

Well Cropland land Rangeland Riparian Urban Other Total 

number (percent) (percent) (percent) (percent) (percent) (percent) (percent) 

Lower Tertiary aquifers--Continued 

SUS2-17 5.8 0.0 82.4 0.0 0.0 11.8 100.0 

SUS2-18 34.1 6.4 55.4 0.0 4.1 0.0 100.0 

SUS2-19 22.2 15.4 33.4 26.3 0.0 2.7 100.0 

SUS2-20 0.0 0.0 100.0 0.0 0.0 0.0 100.0 

SUS2-22 0.0 0.3 99.7 0.0 0.0 0.0 100.0 

SUS2-23 0.0 0.5 99.5 0.0 0.0 0.0 100.0 

SUS2-24 79.0 21.0 0.0 0.0 0.0 0.0 100.0 

SUS2-25 40.2 3.1 37.0 19.7 0.0 0.0 100.0 

SUS2-26 0.0 3.7 76.7 19.6 0.0 0.0 100.0 

SUS2-27 11.4 39.3 0.0 14.6 34.7 0.0 100.0 

SUS2-28 7.9 43.4 30.3 10.8 7.7 0.0 100.0 

SUS2-29 34.5 36.8 28.3 0.0 0.5 0.0 100.0 

SUS2-30 0.0 0.0 100.0 0.0 0.0 0.0 100.0 

Average 23.2 16.1 49.3 7.6 2.4 3.3 

1Individual percentages for each land-use and land-cover category, when summed, did not equal 100 percent due to rounding. 

Riparian land was substantial within 500 m of wells in the Quaternary aquifers (averaging about 24 percent) but was much less 

substantial near the wells in the lower Tertiary aquifers (about 

8 percent). The other substantial land use for wells in both 

types of aquifers was other agricultural land, averaging about 

12 percent for the Quaternary aquifers and about 16 percent for 

lower Tertiary aquifers. Urban and “other” land use within 

500 m of wells in both aquifers was small compared to other 

land uses (table 1). 

Site Selection and Well Construction 

Twenty-five wells completed in Quaternary aquifers and 

29 wells completed in lower Tertiary aquifers were sampled. 

New wells installed for this study and existing wells were used. 

Of the 25 wells sampled for the subunit survey of Quaternary 

aquifers, 24 were monitoring wells installed specifically for the 

study and 1 well was an existing domestic well. Well construction and related information for all sampled wells completed in 

Quaternary aquifers is summarized in table 2. Potential site 

locations were selected randomly using a stratified-randomselection process described by Scott (1990). One primary and 

several alternate sites were selected. Each potential site was 

examined by conducting onsite reconnaissance within a 1-mile 

radius of each potential site to determine if a suitable location 

for well installation could be found. A site was considered suitable for well installation in unconsolidated Quaternary deposits 

if: (1) deposits appeared to be saturated; (2) the selected site was 

accessible by a drilling rig; and (3) permission was granted for 

installation of a monitoring well. If the primary site did not 

meet these criteria, then alternate sites were evaluated until suitable sites were found. 

 Monitoring wells were installed using procedures 

described in Lapham and others (1995). All wells were 

installed using a hollow-stem auger drill rig. Boreholes were 

logged during drilling by a geologist employed by the contractor used to install the wells. Well casings were 2-inch (in.) 

diameter, flush-threaded, factory-sealed schedule-40 polyvinyl 

chloride (PVC) riser. Well screens were constructed of factorysealed schedule-40 PVC and were 5 to 15 ft long with factoryslotted openings (0.010 or 0.020 in. wide). The filter pack 

around the screen was silica sand (generally 10/20 size) above 

which a layer of bentonite pellets or grout was installed. An 

annular seal of concrete was placed above the bentonite and a 

locking steel protective cover was cemented in place. At the 

request of some landowners, several wells were completed 

flush with the land surface for aesthetic reasons. After installation, wells were developed by surging with a surge block and 

pumping with a submersible pump. 

Of the 29 existing wells sampled for the lower Tertiary 

aquifers subunit survey, 15 were domestic wells, 8 were used 

for both mixed domestic and stock purposes, and 6 were stock 

wells. Well construction and related information for all sampled wells completed in lower Tertiary aquifers are summarized 

in table 3. Pre-existing wells completed in lower Tertiary aqui­
fers were selected randomly from wells listed in the Wyoming 

State Engineer’s Office database and the Montana GroundWater Information Center database using a stratified-randomselection process (Scott, 1990). One primary and several alternate wells were selected for sampling. Preexisting wells were 

considered suitable for sampling if: (1) wells were completed 

only in lower Tertiary aquifers and some type of lithologic 

description (“log”) was available; (2) well depths and screen 

intervals were known; (3) well casing material was known 

(PVC casing was preferred over metal casing); (4) water level 

in the well could be measured; (5) wells were equipped with 

submersible pumps rather than other types of pumps; (6) a water 

sample could be obtained before a pressure tank or any treatment system; and (7) permission was obtained to sample. If the 

primary well did not meet these criteria, then alternate wells 

were selected and evaluated until a suitable well was found. In 

a few cases, suitable wells meeting all of these criteria in a particular area could not be found and wells were selected and sampled even though they did not meet all criteria.

 Sample Collection 

Ground-water samples were collected once during October 1999 to March 2000 (Quaternary aquifers subunit survey) 

and from March 2000 to June 2001 (lower Tertiary aquifers 

subunit survey). Ground-water samples were collected and 

processed in a mobile water-quality laboratory using NAWQA 

ground-water sampling procedures described in Koterba and 

others (1995). All materials in contact with the water sample 

were either Teflon or stainless steel. To minimize the risk of 

sample contamination, most samples were collected and preserved in dedicated sampling chambers consisting of clear polyethylene bags supported by tubular PVC frames. Sampling 

equipment from the wellhead to the sampling chamber inside 

the mobile laboratory was decontaminated thoroughly between 

wells using nonphosphate detergent, tapwater, methanol (some 

but not all parts), and deionized water. 

Most wells were sampled after a minimum of three wellcasing volumes were removed (purged) and onsite measurements of specific conductance, pH, water temperature, turbidity, and dissolved oxygen were stable for five consecutive readings (recorded 5 minutes apart). Some low-yielding wells went 

dry prior to removal of three casing volumes, even at low purge 

rates. In those cases, the water level in the well was allowed to 

recover prior to sampling. Dissolved-oxygen concentrations 

did not stabilize in several pre-existing wells (lower Tertiary 

aquifers subunit survey) because of water “cascading” down the 

casing during purging. Dissolved-oxygen measurements are 

not reported for wells where this occurred. 

Alkalinity, major ion, trace element, nutrient, and radionuclide samples were filtered onsite using a 0.45-micron pore-size 

disposable-capsule filter, and collected in precleaned plastic 

bottles that were rinsed onsite with filtered ground water. Samples to be analyzed for major cations, trace elements, and radionuclides were preserved to a pH of less than 2 standard units 

Methods of Investigation 17 

using ultrapure nitric acid. Samples for major anions and tritium did not require preservation. Radon samples were collected using a glass syringe to withdraw 10 milliliters (mL) of 

water from a special back pressure valve; the water sample was 

then injected into a glass scintillation vial below mineral oil and 

shipped to a laboratory within 24 hours. Nutrient samples were 

filtered using a 0.45-micron pore-size disposable-capsule filter, 

collected in rinsed brown plastic bottles without preservation, 

chilled on ice immediately after collection, and shipped to a laboratory within 24 hours. 

Dissolved organic carbon (DOC) samples were filtered 

onsite using 0.45-micron pore size silver filters; the filters 

impart trace concentrations of silver that prevent biological 

activity that could affect DOC concentrations. DOC samples 

were forced through the silver filters using purified nitrogen gas 

at a pressure that did not exceed 15 pounds per square inch. 

DOC samples were collected in cleaned and baked amber glass 

bottles, were chilled on ice immediately after collection, and 

shipped to a laboratory within 24 hours. 

Water samples analyzed for pesticide compounds were filtered using a methanol-rinsed stainless-steel filter chamber that 

contained a baked 0.7-micron pore size glass-fiber filter. Samples were collected in precleaned amber-colored glass bottles, 

chilled on ice immediately after collection, and shipped to a laboratory within 24 hours. 

Samples for volatile organic compound (VOC) analyses 

were not filtered and were collected in three precleaned 40-mL 

amber vials with septa, and the vials were filled with no headspace. VOC samples were preserved to a pH of less than 2 standard units using one to five drops of specially prepared 

1:1 hydrochloric acid, were chilled on ice immediately after 

collection, and shipped to a laboratory within 24 hours. 

Chemical Analyses 

Samples were analyzed for major ions, trace elements, 

nutrients, DOC, radon, gross-alpha activity, gross-beta activity, 

pesticide compounds, and VOCs at the USGS National WaterQuality Laboratory (NWQL) in Denver, Colorado. Samples 

were analyzed for radium-224 and radium-226 isotopes at Duke 

Engineering and Services in Bolton, Massachusetts, and samples were analyzed for radium-228 at Severn Trent Laboratories 

in Richland, Washington. Samples were analyzed for tritium at 

the USGS Isotope Tracers Project Laboratory in Menlo Park, 

California. Methods used to analyze water samples are shown 

in table 4. 

Laboratory analytical results for most constituents were 

reported relative to laboratory reporting levels (LRLs) or to 

minimum reporting levels (MRLs). LRLs are set by the NWQL 

to minimize both false positive and false negative measurement 

error (Childress and others, 1999). MRLs are the minimum 

concentrations of a constituent that can be reported reliably 

using a given analytical method (Timme, 1995). In this report, 

LRLs are reported for organic constituents and MRLs are 

reported for inorganic constituents. 
18 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 2. Well construction and related ancillary 

[DMS, degrees, minutes, seconds; NGVD 29, National Geodetic Vertical Datum of 1929; WY, Wyoming; MT, Montana; 

U.S. Geological Date of well Land-surface 

Well Survey North West Use of construction elevation 

number	 site-identification latitude longitude General location well (month/day/ (feet above 

(fig. 5) number (DMS) (DMS) County State type year) NGVD 29) 

SUS1-1 440629109092401 44 06 28.9 109 09 23.6 Park WY MON 08/18/99 6,710 

SUS1-2 442618109130202 44 26 18.1 109 13 01.7 Park WY MON 11/30/99 5,400 

SUS1-3 444500109013101 44 44 59.6 109 01 30.9 Park WY MON 08/25/99 5,100 

SUS1-4 445613109081401 44 56 12.7 109 08 14.3 Park WY MON 08/25/99 4,115 

SUS1-5 451411109134301 45 14 10.7 109 13 42.5 Carbon MT MON 02/08/00 5,255 

SUS1-6 453101108512801 45 31 10.8 108 51 32.1 Carbon MT MON 09/01/99 3,510 

SUS1-7 451033108575401 45 10 34.6 108 57 53.5 Carbon MT MON 09/02/99 3,800 

SUS1-8 444639108452601 44 46 39.6 108 45 25.5 Park WY MON 12/01/99 4,370 

SUS1-9 444126108513401 44 41 24.8 108 51 38.4 Park WY DOM 03/15/28 4,490 

SUS1-10 441556108473201 44 15 55.8 108 47 32.2 Park WY MON 12/02/99 5,330 

SUS1-11 440213108583501 44 02 13.2 108 58 34.6 Park WY MON 08/19/99 6,435 

SUS1-12 434334108351101 43 43 34.1 108 35 10.7 Hot Springs WY MON 11/29/99 5,340 

SUS1-13 440027108264501 44 00 27.2 108 26 45.0 Washakie WY MON 12/16/99 4,965 

SUS1-14 442354108255801 44 23 54.4 108 25 57.6 Big Horn WY MON 08/17/99 4,390 

SUS1-16 444424108354001 44 44 23.7 108 35 40.3 Park WY MON 08/26/99 4,085 

SUS1-17 445014108224301 44 50 14.2 108 22 42.6 Big Horn WY MON 08/26/99 3,815 

SUS1-18 443023108233201 44 30 22.9 108 23 32.4 Big Horn WY MON 08/23/99 4,445 

SUS1-19 442258108141201 44 22 58.0 108 14 12.4 Big Horn WY MON 08/17/99 4,080 

SUS1-22 433519108125201 43 35 18.9 108 12 51.5 Hot Springs WY MON 08/10/99 4,370 

SUS1-24 435010107214701 43 50 10.0 107 21 47.2 Washakie WY MON 12/14/99 4,640 

SUS1-25 440054107581401 44 00 54.4 107 58 14.0 Washakie WY MON 08/11/99 4,045 

SUS1-27 440952107405101 44 09 52.2 107 40 50.6 Washakie WY MON 12/15/99 4,175 

SUS1-28 441554107560001 44 15 54.5 107 55 59.7 Big Horn WY MON 08/13/99 3,920 

SUS1-29 441821108014701 44 18 21.1 108 01 47.5 Big Horn WY MON 08/16/99 3,900 

SUS1-30 444719108050501 44 47 18.8 108 05 05.5 Big Horn WY MON 08/31/99 4,280 

1Water level measured in nearby stock well at similar land-surface elevation completed to similar depth because water level could not be measured in 

sampled well. 
Methods of Investigation 19 

information for sampled wells completed in Quaternary aquifers 

DOM, domestic well; MON,monitoring well installed for this study; PVC, polyvinyl chloride; FS, factory-slotted well screen] 

Depth of Screened Casing Diameter of Diameter of casing 

well Water level Date of or open material casing material Casing material comprising 

(feet below (feet below water-level interval above above screened material in Type of screened or 

land land measure- (feet below screened or or open interval screened or openings in open interval 

surface) surface) ment land surface) open interval (inches) open interval interval (inches) 

16 4.39 10-19-99 6-16 PVC 2 PVC FS 2 

30 24.62 03-29-00 20-30 PVC 2 PVC FS 2 

22 7.23 10-13-99 7-22 PVC 2 PVC FS 2 

19 7.58 10-13-99 4-19 PVC 2 PVC FS 2 

38 26.03 03-30-00 28-38 PVC 2 PVC FS 2 

22 4.46 11-01-99 7-22 PVC 2 PVC FS 2 

28 16.36 11-02-99 13-28 PVC 2 PVC FS 2 

23 6.15 12-13-99 13-23 PVC 2 PVC FS 2 

19 1

11.15 10-12-99 5.5-19 Tile 20 Tile Walled 20 

13 6.41 12-15-99 8-13 PVC 2 PVC FS 2 

15 4.53 10-18-99 5-15 PVC 2 PVC FS 2 

15 6.50 12-16-99 5-15 PVC 2 PVC FS 2 

24 14.44 03-28-00 14-24 PVC 2 PVC FS 2 

15 4.26 01-11-00 5-15 PVC 2 PVC FS 2 

15 5.58 10-14-99 5-15 PVC 2 PVC FS 2 

22 8.05 11-03-99 7-22 PVC 2 PVC FS 2 

15 6.26 10-20-99 5-15 PVC 2 PVC FS 2 

17 5.12 01-12-00 7-17 PVC 2 PVC FS 2 

15 1.87 10-05-99 5-15 PVC 2 PVC FS 2 

42 29.11 01-10-00 32-42 PVC 2 PVC FS 2 

15 4.57 10-06-99 5-15 PVC 2 PVC FS 2 

15.5 8.50 01-13-00 10.5-15.5 PVC 2 PVC FS 2 

20 7.68 10-07-99 5-20 PVC 2 PVC FS 2 

20 8.97 10-21-99 5-20 PVC 2 PVC FS 2 

29 15.74 11-04-99 14-29 PVC 2 PVC FS 2 
20 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 3. Well construction and related ancillary information 

[DMS, degrees, minutes, seconds; NGVD 29, National Geodetic Vertical Datum of 1929; MT, Montana, WY, Wyoming; PVC, polyvinyl 

U.S. Geological Date of well Land- surface 

Well Survey North West construction elevation 

number	 site-identification latitude longitude General location (month/day/ (feet above 

(fig. 4) number (DMS) (DMS) County State Use of well year) NGVD 29) 

SUS2-1 451608109223001 45 16 08.1 109 22 30.2 Carbon MT DOM 09/14/94 5,300


SUS2-2 452239109191101 45 22 39.4 109 19 10.6 Carbon MT DOM1 06/05/95 4,495


SUS2-3 452326109065301 45 23 25.7 109 06 53.2 Carbon MT DOM 09/04/90 4,500 

SUS2-4 451407109133901 45 14 06.9 109 13 38.7 Carbon MT DOM 01/16/96 5,280 

SUS2-5 450210109030601 45 02 09.6 109 03 06.1 Carbon MT UNSTO 05/23/86 4,070 

SUS2-6 450658109010401 45 06 57.7 109 01 03.6 Carbon MT STO 10/16/95 3,970 

SUS2-7 445246109084101 44 52 46.1 109 08 41.3 Park WY DOM 11/21/96 4,220 

SUS2-8 444509109010901 44 45 08.7 109 01 09.2 Park WY DOM 10/09/91 5,085 

SUS2-9 444911108444501 44 49 11.5 108 44 44.9 Park WY DOM 02/05/95 4,415 

SUS2-10 444107108550201 44 41 06.7 108 55 02.3 Park WY DOM/STO 12/06/84 4,565 

SUS2-11 444326108424501 44 43 26.1 108 42 45.0 Park WY DOM1 09/10/97 4,310 

SUS2-12 444417108381001 44 44 17.0 108 38 10.0 Park WY DOM 04/30/79 4,205 

SUS2-13 443426108593501 44 34 26.3 108 59 34.7 Park WY DOM/STO 03/01/93 4,925 

SUS2-14 442639108220201 44 26 39.0 108 22 02.5 Big Horn WY DOM/STO 12/28/77 4,380 

SUS2-15 442933108211201 44 29 32.5 108 21 11.6 Big Horn WY DOM 06/14/89 4,440 

SUS2-16 442239108362001 44 22 38.6 108 36 20.3 Park WY DOM 09/22/98 4,795 

SUS2-17 442258108260301 44 22 57.8 108 26 02.5 Big Horn WY DOM/STO 10/05/95 4,460 

SUS2-18 442348108082301 44 23 48.3 108 08 23.2 Big Horn WY DOM 09/26/86 4,025 

SUS2-19 441220108513301 44 12 20.5 108 51 32.5 Park WY DOM 406/01/97 5,620 

SUS2-20 441639108195501 44 16 38.8 108 19 55.3 Big Horn WY UNSTO5 06/23/73 4,345 

SUS2-22 440943108455001 44 09 42.5 108 45 50.3 Park WY STO 04/15/78 5,880 

SUS2-23 440306108160601 44 03 06.4 108 16 09.9 Washakie WY STO 12/02/65 4,455 

SUS2-24 441046107562201 44 10 46.4 107 56 22.4 Big Horn WY DOM/STO 08/26/88 4,020 
Methods of Investigation 21 

for sampled wells completed in lower Tertiary aquifers

 chloride; FS, factory-slotted well screen; DOM, domestic well; UNSTO, unused stock well; STO, stock well; --, not applicable; Flow, flowing well] 

Depth of Screened Casing Diameter of Diameter of casing 

well Water level Date of or open material casing material Casing material comprising 

(feet below (feet below water-level interval above above screened material in Type of screened or 

land land measure- (feet below screened or or open interval screened or openings in open interval 

surface) surface) ment land surface) open interval (inches) open interval interval (inches) 

250 93.12 02-26-01 220-230	 Steel 8.62 PVC FS 4.5 

PVC 4.5 

240 2.35 08-08-00 60-80 Steel 6.62 PVC FS 4


140-160 PVC 4 PVC FS 4


200-220
 PVC FS 4 

92 17.1 08-07-00 32-72 Steel 6.62 PVC FS 4.5 

PVC 4.5 

160 26.1 08-09-00 100-140 Steel 6.62 PVC FS 4 

PVC 4 

130 31.87 02-28-01 40-72 Steel 8.62 Steel FS 8 

100-120 PVC 5 PVC FS 5 

400 41.46 02-27-01 240-280 Steel 6.62 PVC FS 4.5 

PVC 4.5 

120 44.62 07-31-00 95-105 Steel 6.62 PVC FS 4.5 

PVC 4.5 

140 41.2 08-01-00 70-85 PVC 6 PVC FS 4.5 

120-140 PVC 4.5 PVC FS 4.5 

60 9.42 08-02-00 35-58 PVC 7.88 PVC FS 7.88 

190 36.72 08-03-00 70-100 Steel 7 PVC FS 6 

155-180 PVC 6 PVC FS 6 

100 31.48 05-23-01 41-46 PVC 6 PVC FS 4.5 

68-76 PVC 4.5 PVC FS 4.5 

130 19.32 03-01-01 45-125 PVC 6 PVC FS 4 

PVC 4 

200 53.8 06-06-01 2165-180 PVC 6 PVC FS 4.5 

PVC 4.5 

155 370 312-28-77 90-155 Steel 7 Unknown FS 6 

Unknown 6 

120 21.28 09-18-00 60-120 PVC 5 PVC FS 5 

160 350 309-22-98 80-100 PVC 6 PVC FS 4.5 

140-160 PVC 4.5 PVC FS 4.5 

190 126.72 07-10-00 163-190 PVC 6 PVC FS 4.5 

PVC 4.5 

160 17.85 07-11-00 100-160 PVC 4 PVC FS 4 

4

190 21.5 09-20-00 435-45 PVC 6 PVC FS 4.5 

4

70-80 PVC 4.5 PVC FS 4.5 

4

180-190 PVC FS 4.5 

115 6.61 10-24-00 --5 Steel 7 --5 --5 --5 

160 43.77 10-25-00 31-160 Steel 8.62 PVC FS 6.62 

PVC


250 6Flow 10-18-00 243-250 Steel 6 None Open -­


PVC
 hole


410 27.37 07-12-00 110-120 Steel 8 PVC FS 5


175-380 PVC 5 PVC FS 5


385-400 PVC FS 5

22 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 3. Well construction and related ancillary information 

U.S. Geological General location Date of well Land- surface 

Well Survey North West construction elevation 

number site-identification latitude longitude (month/day/ (feet above 

(fig. 5) number (D M S) (D M S) County State Use of well year) sea level) 

SUS2-25 440008108272601 44 00 08.5 108 27 26.2 Washakie WY DOM/STO7 12/30/96 4,985 

SUS2-26 435735108074101 43 57 35.2 108 07 40.6 Washakie WY DOM/STO 04/11/95 4,325 

SUS2-27 440207107553001 44 02 07.2 107 55 29.9 Washakie WY DOM1 08/09/97 4,090 

SUS2-28 435143108090501 43 51 42.6 108 09 05.2 Washakie WY DOM 08/24/93 4,205 

SUS2-29 435556107580101 13 55 55.9 107 58 07.3 Washakie WY DOM/STO 04/10/97 4,220 

SUS2-30 435115107454801 43 51 18.4 107 45 50.2 Washakie WY STO 10/15/41 4,520 

1

Water from well only used for lawn watering. 2

Completion report open interval is stated to be 180-200 feet below land surface. According to driller’s log, this interval is in clay. Driller’s log states that 

sandstone with water is at 165-180 feet below land surface. Assumed open interval is actually 165-180 feet below land surface. 3No access for water-level measurement; water level obtained from Wyoming State Engineer’s Office well permit. 4

Original well drilled in about 1900, about 80-feet deep. Well redrilled to 190 feet below land surface in 1997. 5

Former stock well, portable sample pump used. No completion information could be located. Sandstone at 76-88 feet below land surface and 95-105 feet 

below land surface. 6Flowing well, no pump required for sampling. 7

Flowing well with pump to increase well yield for domestic use. 

Radionuclides were reported in relation to a samplespecific minimum detectable concentration (MDC) and an analytical uncertainty value (also known as a counting error). The 

MDC is “the minimum quantity of a specific radionuclide 

detected by the counting instrument for any sample for a given 

analysis,” and it is “defined by the requirement that the counted 

radioactivity must differ from the background count by three 

times the standard deviation of the background count” (Focazio 

and others, 2001, p. 24). MDCs are determined for each 

radionuclide analysis based on instrument conditions at the time 

of measurement and reported by the laboratory for each analysis. 

Ground-water samples were analyzed for 109 different 

pesticides or pesticide breakdown products (herein referred to 

as pesticide compounds) using either C-18 solid-phase extraction and capillary-column gas chromatography/mass spectrometry (GC/MS) (Zaugg and others, 1995) or graphitized carbonbased solid-phase extraction and high-performance liquid chromatography/mass spectrometry (Furlong and others, 2001) 

(table 5). The latter analytical method (Furlong and others, 

2001) was used prior to final approval in April 2001 by the U.S. 

Geological Survey’s Office of Water Quality. Although the 

analytical method did not change following approval, samples 

analyzed prior to April 2001 and prior to approval of the method 

were considered provisional. Pesticide compounds detected in 

samples from the Quaternary aquifers using this method prior to 

approval are reported and qualified as “M” values (pesticide 

detected, but not quantified) because of laboratory quality 

assurance/quality control (QA/QC) problems. Recommended 

laboratory holding times were exceeded and pesticide degradation may have occurred. Degradation may have resulted in 

fewer pesticides being detected than were actually present in 

samples and may have affected measured concentrations of pesticides and pesticide breakdown products (Furlong and others, 

2003). The laboratory QA/QC problems did not affect samples 

collected from the lower Tertiary aquifers. 

Ground-water samples were analyzed for 85 VOCs using 

a purge and trap capillary GC/MS method (Connor and others, 

1998) (table 6). Samples collected from the lower Tertiary 

aquifers also were analyzed for tentatively identified compounds (TICs). A TIC is a VOC that is identified by a gas chromatography/mass spectrometry library search routine and compared to mass spectra in a reference library, typically the 

National Institute for Standards and Technology (NIST) library. 

The VOC is considered "tentatively identified" until a reference 

standard is obtained and analyzed in the same manner (Donna 

Rose, U.S. Geological Survey, written commun., 2003). 
Methods of Investigation 23 

for sampled wells completed in lower Tertiary aquifers--Continued 

Depth of 

well 

(feet below 

land 

surface) 

Water level 

(feet below 

land 

surface) 

Date of 

water-level 

measurement 

Screened 

or open 

interval

 (feet below 

land surface) 

Casing 

material 

above 

screened or 

open interval 

Diameter of 

casing material 

above screened 

or open interval 

(inches) 

Casing 

material in 

screened or 

open interval 

Type of 

openings in 

interval 

Diameter of casing 

material comprising 

screened or 

open interval 

(inches) 

141 345 04-11-95 110-141 Steel 6 PVC FS 4.5 

PVC 4.5 

141 26.1 09-19-00 41-61 Steel 8 PVC FS 5 

121-141 PVC 5 PVC FS 5 

110 11.48 05-16-00 50-110 Steel 6 Unknown FS 4.5 

PVC 4.5 

190 105.01 07-13-00 110-130 PVC 6 PVC FS 4.5 

150-190 PVC 4.5 PVC FS 4.5 

225 151.4 10-23-00 150-225 PVC 6.62 

5 

None Open 

hole 

--

440 Flow7 10-26-00 400-440 Steel 

PVC 

6 

4.5 

PVC FS 4.5 

Quality Assurance and Quality-Control Samples 

In addition to collection of environmental ground-waterquality samples, several types of QA/QC samples were collected. QA/QC samples included several types of blanks, replicate environmental samples, and field matrix-spike samples. 

The QA/QC samples were collected, preserved, and analyzed 

using the same methods and equipment as for environmental 

samples. Collection and evaluation of QA/QC samples, in addition to strict sample collection, processing, and analysis procedures, composed the quality-assurance program. 

Blank Samples

Several types of blank samples were collected to evaluate 

bias from the potential introduction of contamination to environmental samples during field sample collection, field equipment cleaning, and laboratory analytical procedures. Specially 

prepared water for all blank samples was provided by the USGS 

for the NAWQA program, and was certified to be free of inorganic (inorganic-free blank water) and organic (organic-free 

blank water) constituents. Field-equipment blanks were collected subsequent to collection of environmental samples and 

cleaning of the sampling equipment. Field-equipment blanks 

were collected during sampling trips to determine if cleaning 

procedures removed constituents from sampling equipment 

between sampling sites and to ensure that field and laboratory 

methods had not contaminated environmental samples. After 

cleaning was completed, the field-equipment blank was collected by passing blank water through all sampling equipment 

and then collecting and preserving the sample using the same 

procedures as for environmental samples. Trip blanks consisted 

of vials filled with organic-free blank water and sealed at the 

USGS NWQL. Trip blanks were used to verify that VOC vials 

were not contaminated during storage, sampling, or shipment to 

the NWQL. Source-solution blanks were collected by filling 

sample bottles directly with organic-free blank water instead of 

passing it through the sampling equipment. Source-solution 

blanks were collected to ensure that the certified organic-free 

blank water was free of detectable DOC and VOCs. 

One field-equipment blank was collected prior to both subunit surveys at the USGS office in Cheyenne. This blank sample (referred to herein as an “office blank”) was collected to 

ensure that the sampling equipment and procedures did not 

introduce any contaminants into environmental samples. In 

general, the office blank indicated that the sampling equipment 
24 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 4. Laboratory methods used to analyze ground-water samples 

[USGS, U.S. Geological Survey; AA, atomic absorption; ICP, inductively-coupled plasma; MS, mass spectrometry; GFAA, graphite furnace atomic absorption 

spectrophotometry; UV, ultraviolet; GC/MS, gas chromatography/mass spectrometry] 

Constituent or constituent group 

USGS schedule 

(SC) or laboratory 

code (LC) Analysis method 

Inorganic Constituents 

Method reference 

Major ions SC2750 AA spectrometry, colorimetry, ionexchange chromatography, ICP 

atomic emission spectrometry, and 

MS 

Fishman and Friedman (1989) 

and Fishman (1993) 

Alkalinity, laboratory LC2109 Fixed endpoint method Fishman and Friedman (1989) 

Trace elements SC2703, SC2710 ICP MS and GFAA Fishman and Friedman 

(1989); Faires (1993); McLain 

(1993); Garbarino (1999); and 

Jones and Garbarino (1999) 

Nutrients SC2752 Colorimetry Fishman (1993) 

Dissolved organic carbon (DOC) LC113 UV-light promoted persulfate 

oxidation and infrared spectrometry 

Brenton and Arnett (1993) 

Radionuclides 

Gross-alpha and gross-beta activity SC1263 Evaporation 1U.S. Environmental Protection Agency (1980) method 

900.0 with modification 

Radium isotopes (Ra-224, Ra-226, 

and Ra-228) 

SC1263 Alpha spectrometry 1For Ra-228, U.S. Environmental Protection Agency 

(1980) method 900.0 with 

modification, proprietary 

method for Ra-224 and Ra226 

Radon-222 LC1369 Liquid scintillation American Society for Testing 

and Materials (1996) 

Tritium LC1565 Electrolytic enrichment Ostlund and Dorsey (1975) 

Organic Compounds 

Pesticides SC2001 Solid-phase extraction using a C-18 

cartridge and GC/MS 

Zaugg and others (1995) 

Pesticides LC9060, SC2060 Graphitized carbon-based solid-phase 

extraction and high-performance 

liquid chromatography/MS 

Furlong and others (2001) 

Volatile organic compounds (VOCs) SC2020, SC2021 Purge and trap-capillary-column GC/ 

MS 

Connor and others (1998) 

1

Modifications to U.S. Environmental Protection Agency method 900.0 included sample preparation and counting within 72 hours of sample collection 

and recounting after 30 days. In addition, gross-alpha activities were based on a thorium-230 curve and gross-beta activities were based on a cesium-137 

curve (Ann Mullin, U.S. Geological Survey, written commun., 2004) 
Table 5. Pesticides analyzed, trade name, pesticide action, class, laboratory reporting levels, and U.S. Environmental Protection Agency health benchmarks

25 

Table 5. Pesticides analyzed, trade name, pesticide action, class, laboratory reporting levels, and U.S. Environmental Protection Agency health benchmarks[USGS, U.S. Geological Survey; μg/L, micrograms per liter; USEPA, U.S. Environmental Protection Agency. Blue text, pesticide detected in Quaternary aquifers; red text, pesticide detected in lower Tertiary aquifers; green text, pesticide detected in both Quaternary and lower Tertiary aquifers; USGS analytical method type: 1=USGS laboratory schedule SC2001, 2=USGS laboratory code LC9060/schedule SC2060; NA, not applicable; U, chemical analyzed for, but not detected; --, not applicable] 

USEPA 

USGS Primary Other preferred

USGS analytical laboratory laboratory human

Pesticide class laboratory method reporting reporting health 

(or parent parameter (see level levels benchmark 

Pesticide Trade name Pesticide action compound class) code headnote) (μg/L) (μg/L) (μg/L) 

Acetochlor Guardian, Harness, Relay Preplant herbicide Chloroacetamide 49260 1 0.002 0.004 --Acifluorfen Blazer, Tackle 2S, Astic Herbicide Miscellaneous 49315 2 .06 .01 110 

Alachlor Alanex, Lasso, Shroud Herbicide Acetanilide 46342 1 .002 -- 12 Aldicarb Temik Insecticide, nematicide, Carbamate 49312 2 .08 .04 1,23 

acaricide 

Aldicarb sulfone Standak, aldoxycarb, aldicarb Insecticide Carbamate 49313 2 .2 .02 1,22 

metabolite 

Aldicarb sulfoxide Aldicarb breakdown product -- Carbamate 49314 2 .03 .01 1,24 Atrazine Aatrex, Atranex Herbicide Triazine 39632 1 .001 .005 13 

.006.007

.07 

Azinphos-methyl Guthion, Crysthyon Insecticide Organophosphate 82686 1 .001 .05 --Bendiocarb Ficam, Garrox, Turcam Insecticide Carbamate 50299 2 .06 .03 --Benfluralin Balan, Benefin Herbicide Dinitroaniline 82673 1 .002 .01 -­Benomyl Benlate, Benex Fungicide Carbamate 50300 2 .02 -- --Bensulfuron, methyl Escuri, Londax Herbicide Sulfonylurea 61693 2 .05 .02 --Bentazon Basagram, Bentzone Herbicide Miscellaneous 38711 2 .02 .01 3200 Bromacil Hyvar X Herbicide Uracil 04029 2 .08 .03 390 Bromoxynil Buctril, Brominal, Agristar Herbicide Miscellaneous 49311 2 .06 .02 -­Butylate Sutan+, Genate Plus Herbicide Carbamate 04028 1 .002 -- 3400 Carbaryl Carbatox, Sevin Insecticide Carbamate 49310 2 .06 .03 3700 Carbaryl Carbatox, Sevin Insecticide Carbamate 82680 1 .003 .04 3700 Carbofuran Furadan, Futura Insecticide Carbamate 49309 2 .06 .01 140 Carbofuran Furadan, Futura Insecticide Carbamate 82674 1 .003 .02 140 Chloramben, methyl ester Chloramben Herbicide Miscellaneous 61188 2 .1 .02 3100 Chlorimuron Classic, Darban, Lory Herbicide Sulfonylurea 50306 2 .04 .01 -­Chlorothalonil4 Bravo Fungicide Organochlorine 49306 2 0.05 0.04 15 Chlorpyrifos Dursban, Lorsban Insecticide Organophosphate 38933 1 .004 .005 320 Clopyralid Stinger, Lontrel Herbicide Miscellaneous 49305 2 .04 .01 -­

Methods of Investigation 
26 

Table 5. Pesticides analyzed, trade name, pesticide action, class, laboratory reporting levels, and U.S. Environmental Protection Agency health benchmarks—Continued

USEPA 

USGS Primary Other preferred

USGS analytical laboratory laboratory human

Pesticide class laboratory method reporting reporting health 

(or parent parameter (see level levels benchmark 

Pesticide Trade name Pesticide action compound class) code headnote) (μg/L) (μg/L) (μg/L) 

Cyanazine Bladex Selective herbicide 

Triazine 04041 1 .004 -- 31 

Cycloate Ro-Neet Selective herbicide 

Thiocarbamate 04031 2 .05 .01 -­

2,4-D 

Dacamine, Weed-B-Gon Herbicide 

Chlorophenoxy 39732 2 .08 .02 170 

2,4-DB Butoxone, Butyrac Selective herbicide 

Chlorophenoxy 38746 2 .07 .02 -­

2,4-D methyl ester 

Chlorophenoxy 50470 2 .05 .009 -­

.09 

Dacthal monoacid Dacthal breakdown product -- Organochlorine 49304 2 .09 .007 -­

.01 

DCPA Dacthal 

Herbicide Organochlorine 82682 1 .002 .003 370 

p,p’-DDE DDT breakdown -- Organochlorine 34653 1 .003 .006 41 

product 

Deethylatrazine Atrazine breakdown product -- Triazine 04040 1 .002 .006 --Deethyl deisopropylatrazine Atrazine breakdown product -- Triazine 04039 2 .06 .01 --Deisopropylatrazine Atrazine/cyanazine/simazine -- Triazine 04038 2 .07 .04 -­

breakdown product 

Diazinon Basudin, Spectracide, Knoxout Insecticide, nematicide Organophosphate 39572 1 .002 .005 3.6 

Dicamba 

Banvel, Banex Herbicide Benzoic Acid 38442 2 .01 .1 3200 

1,2-Dichlorobenzene 

Telone II, Ortho-Dichlorobenzene Herbicide, insecticide, Miscellaneous 34536 1 .05 .2 1600 

solvent, soil fumigant 

Dichlorprop 

Weedone, Polymone Herbicide 

Chlorophenoxy 49302 2 .05 .01 -­

Dieldrin Panoram D-31, Octalox Insecticide Organochlorine 39381 1 .001 .005 4.02 2,6-Diethylaniline 

Alachlor breakdown product -- Acetanilide 82660 1 .003 .002 --

Dinoseb Premerge Herbicide 

Nitrophenolic 49301 2 .04 .01 17 

Diphenamid Dymid, Enide Selective herbicide 

Amide 04033 2 .06 .03 3200 

Disulfoton Di-Syston Insecticide, acaricide 

Organophosphate 82677 1 .02 -- 3.3 

Diuron Durashield, Karmex Herbicide 

Urea 49300 2 .08 .01 310 

EPTC Eptam, Eradicane 

Herbicide Carbamate 82668 1 0.002 0.007 --

Ethalfluralin 

Eptam, Eradicane 

Herbicide Dinitroaniline 82663 1 .004 .009 --

Ethoprop Mocap, Prophos Insecticide, nematicide Organophosphate 82672 1 .003 .005 --Fenuron 

Fenuron Herbicide 

Urea 49297 2 .07 .03 --

Flumetsulam 

Broadstrike, Python Herbicide Sulfonamide 61694 2 .09 .01 --

Fluometuron Cotoran 

Herbicide Urea 38811 2 .06 .03 390 

Fonofos Dyfonate Insecticide Organophosphate 04095 1 .003 -- 310 

Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 
27 

Table 5. Pesticides analyzed, trade name, pesticide action, class, laboratory reporting levels, and U.S. Environmental Protection Agency health benchmarks—Continued

USEPA 

USGS Primary Other preferred

USGS analytical laboratory laboratory human

Pesticide class laboratory method reporting reporting health 

(or parent parameter (see level levels benchmark 

Pesticide Trade name Pesticide action compound class) code headnote) (μg/L) (μg/L) (μg/L) 

alpha-HCH Insecticide Organochlorine 34253 1 .002 .005 4.06 

gamma-HCH Lindane, Isotoz Insecticide Organochlorine 39341 1 .004 -- 1.2 Hydroxyatrazine Atrazine breakdown product -- Triazine 50355 2 .2 .008 -­3-Hydroxycarbofuran Carbofuran breakdown product -- Carbamate 49308 2 .06 .01 --Imazaquin Scepter Herbicide Imidazolinone 50356 2 .1 .02 --Imazethapyr New Path, Pursuit Herbicide Imidazolinone 50407 2 .09 .02 --Imidacloprid Admire, Provado Insecticide Chloronicotynil 61695 2 .1 .007 -­3-keto Carbofuran Carbofuran breakdown product -- Carbamate 50295 2 .07 1.5 --Linuron Linurex, Lorox Herbicide Urea 38478 2 .07 .01 --Linuron Linurex, Lorox Herbicide Urea 82666 2 .002 .035 -­Malathion Cythion, Malaspray Insecticide Organophosphate 39532 2 .005 .03 3100 MCPA Solve, MCP Herbicide Chlorophenoxy 38482 2 .06 .02 34 MCPB Butoxone M40, Thistrol Herbicide Chlorophenoxy 38487 2 .06 .01 --Metalaxyl Apron, Ridamil, Subdue Fungicide Miscellaneous 50359 2 .06 .02 --Methiocarb Mesurol Insecticide Carbamate 38501 2 .08 .01 --Methomyl Lannate, Nudrin Insecticide Carbamate 49296 2 .08 .004 3200 Methomyloxime Methomyl breakdown product -- Carbamate 61696 2 .01 -- -­Methyl parathion Penncap-M, Paratox Insecticide Organophosphate 82667 1 .006 -- 32 Metolachlor Bicep, Dual Herbicide Amide 39415 1 .002 .001 3100 Metribuzin Lexone, Sencor Herbicide Triazine 82630 1 .004 .006 3200 Metsulfuron Ally, Escort Herbicide Sulfonylurea 61697 2 .1 .03 --Molinate Hydram, Ordram Herbicide Carbamate 82671 1 .004 .002 --Napropamide Devrinol Herbicide Amide 82684 1 .003 .007 --Neburon Granurex, Propuron Herbicide Urea 49294 2 .07 .01 --Nicosulfuron Accent, OneHope Herbicide Sulfonylurea 50364 2 .07 .01 --Norflurazon Zorial, Solicam Herbicide Miscellaneous 49293 2 .08 .02 --Oryzalin Surflan Herbicide Dinitroaniline 49292 2 .07 .02 --Oxamyl Vydate Insecticide, acaricide, Carbamate 38866 2 .02 .01 1200 

nematicide 

Oxamyloxime Oxamyl breakdown product -- Carbamate 50410 2 .06 .01 -­Parathion Alkron, Bladan, Fighter Insecticide Organophosphate 39542 1 .004 .007 --Pebulate Tillam Herbicide Carbamate 82669 1 .004 .002 -­

Methods of Investigation 
28 

Table 5. Pesticides analyzed, trade name, pesticide action, class, laboratory reporting levels, and U.S. Environmental Protection Agency health benchmarks—Continued

USEPA 

USGS Primary Other preferred

USGS analytical laboratory laboratory human

Pesticide class laboratory method reporting reporting health 

(or parent parameter (see level levels benchmark 

Pesticide Trade name Pesticide action compound class) code headnote) (μg/L) (μg/L) (μg/L) 

Pendimethalin Prowl, Sto

mp Herbicide Dinitroaniline 82683 1 .004 .01 -­

cis-Permethrin 

Ambush, Pounce Insecticide 

Pyrethroid 82687 1 .005 .006 -­

Phorate 

Thimet, Rampart Insecticide Organophosphate 82664 1 .002 .01 -­

Picloram Tordon Herbicide amine 49291 2 .07 .02 1500 

Prometon Pramitol, Gesafram 

Herbicide Triazine 04037 1 .018 .015 3100 

Pronamide Kerb Herbicide 

Amide 82676 1 .003 .004 350 

Propachlor 

Ramrod, Prolex Herbicide 

Amide 04024 1 .007 .01 390 

Propanil Stamp Herbicide 

Amide 82679 1 .004 .01 --

Propargite 

Comite, Omite Insecticide, acaricide 

Miscellaneous 82685 1 .013 .02 --

Propham 

Chem Hoe 

Herbicide Carbamate 49236 2 .07 .01 3100 

Propiconazole Banner 

Fungicide Miscellaneous 50471 2 .06 .02 --

Propoxur Baygone, Suncide Fungicide Carbamate 38538 2 .06 .01 --Siduron Tupersan Herbicide 

Urea 38548 2 .09 .01 -­

Simazine Aquazine, Princep 

Herbicide Triazine 04035 1 .005 .01 14 

Sulfo

metruron, methyl Oust Herbicide Sulfonylurea 50337 2 .04 .009 --

Tebuthiuron Graslan, Spike 

Herbicide Urea 82670 1 .01 .02 3500 

Terbacil Sinbar, Herbicide 732 Herbicide 

Uracil 04032 2 .1 .01 390 

Terbacil Sinbar, Herbicide 732 Herbicide 

Uracil 82665 1 .007 .03 390 

Terbufos Counter, Contraven Insecticide Organophosphate 82675 1 0.013 0.02 30.9 Terbuthylazine 

Gardoprim Herbicide 

Triazine 04022 1 U -- --

Thiobencarb 

Bolero, Saturn Herbicide 

Carbamate 82681 1 .002 .005 --

Triallate Far-Go, Avadex BW Herbicide 

Carbamate 82678 1 .001 .002 --

Tribenuron Express, Urgent Herbicide Sulfonylurea 51159 2 .07 .01 --Triclopyr Garlon Herbicide 

Chlorophenoxy 49235 2 .1 .02 -­

Trifluralin Treflan, Trim Herbicide 

Dinitroaniline 82661 1 .002 .009 35 

Urea, 3,4-Chlorophenyl, methyl Diuron breakdown product -- Urea 61692 2 .09 .02 -­

1U.S. Environmental Protection Agency 

Maximum Contaminant Level (MCL) (U.S. Environmental Protection Agency, 2002). 2

The MCL is under administrative stay pending revie

w by U.S. Environmental Protection Agency. The MC

L for any combination of 2 or more of these 3 che

micals (aldicarb, aldicarb sulfoxide, and aldicarb

sulfone) should not exceed 7 μg/L because of similar mode of action. 3U.S. Environmental Protection Agency Lifetime Health Advisory (HAL) (

U.S. Environmental Protection Agency, 2002) 4

U.S. Environmental Protection Agency Risk-Specific Dose at 10-5 Cancer Risk (RSD5) (U.S. Environmental Protection Agency, 2003a, 2003b). 

Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 
Table 6. Volatile organic compounds (VOCs) analyzed, laboratory reporting levels, and related U.S. Environmental Protection Agency standa

Table 6. Volatile organic compounds (VOCs) analyzed, laboratory reporting levels, and related U.S. Environmental Protection Agency standa[USGS, U.S. Geological Survey; μg/L, micrograms per liter; USEPA, U.S. Environmental Protection Agency; --, not applicable] 

USGS Other 

laboratory Chemical Abstract Laboratory laboratory 

parameter Service (CAS) reporting level reporting level

Volatile organic compound (VOC) Common name code number (μg/L) (μg/L) 

Acetone Acetone 81552 67-64-1 7 35 tert-Amyl methyl ether tert-amyl methyl ether (TAME) 50005 994-05-8 .1 .6 Benzene -- 34030 71-43-2 .04 .2 

Bromobenzene Phenyl bromide 81555 108-86-1 .04 .2 Bromochloromethane Methylene chlorobromide 77297 74-97-5 .04 .2 Bromodichloromethane Dichlorobromomethane 32101 75-27-4 .05 .2 Bromoethene Vinyl Bromide 50002 593-60-2 .1 .5 Bromomethane Methyl bromide 34413 74-83-9 .3 1 

2-Butanone Methyl ethyl ketone (MEK) 81595 78-93-3 2 8 n-Butylbenzene 1-Phenylbutane 77342 104-51-8 .2 .9 Carbon disulfide Carbon Disulfide 77041 75-15-0 .07 .4 Chlorobenzene Monochlorobenzene 34301 108-90-7 .03 .1 Chloroethane Ethyl chloride 34311 75-00-3 .1 .6 Chloroethene Vinyl Chloride 39175 75-01-4 .1 .6 Chloromethane Methyl chloride 34418 74-87-3 .5 3 1-Chloro-2-methylbenzene o-Chlorotoluene 77275 95-49-8 .04 .2 1-Chloro-4-methylbenzene p-Chlorotoluene 77277 106-43-4 .06 .3 3-Chloro-1-propene 3-Chloropropene 78109 107-05-1 .2 1 Dibromochloromethane Dibromochloromethane 32105 124-48-1 .2 .9 1,2-Dibromo-3-chloropropane DBCP, Nemagon 82625 96-12-8 .2 1 1,2-Dibromoethane Ethylene dibromide (EDB) 77651 106-93-4 .04 .2 Dibromomethane Methylene dibromide 30217 74-95-3 .05 .3 1,2-Dichlorobenzene o-Dichlorobenzene 34536 95-50-1 .05 .2 1,3-Dichlorobenzene m-Dichlorobenzene 34566 541-73-1 .05 .3 1,4-Dichlorobenzene p-Dichlorobenzene 34571 106-46-7 .05 .3 trans-1,4-Dichloro-2-butene (Z)-1,4-Dichloro-2-butene 73547 110-57-6 .7 4 Dichlorodifluoromethane CFC 12, Freon 12 34668 75-71-8 .3 1 

1,1-Dichloroethane Ethylidene dichloride 34496 75-34-3 .07 .3 1,2-Dichloroethane Ethylene dichloride 32103 107-06-2 .1 .7 

1,1-Dichloroethene Vinylidene chloride 34501 75-35-4 .04 .2 cis-1,2-Dichloroethene (Z)-1,2-Dichloroethene 77093 156-59-2 0.04 0.2 trans-1,2-Dichloroethene (E)-1,2-Dichlorothene 34546 156-60-5 .03 .2 
30 Table 6. Volatile organic compounds (VOCs) analyzed, laboratory reporting levels, and related U.S. Environmental Protection Agency standards—Continued

USGS Other 

laboratory Chemical Abstract Laboratory laboratory 

parameter Service (CAS) reporting level reporting levels USEPA standard 

Volatile organic compound (VOC) Common name code number (μg/L) (μg/L) (μg/L) 

Dichloromethane 

Methylene chloride 34423 75-09-2 .4 2 15 

1,2-Dichloropropane 

Propylene dichloride 34541 78-87-5 .07 .3 15 

1,3-Dichloropropane 

Trimethylene dichloride 77173 142-28-9 .1 .6 -­

2,2-Dichloropropane -- 77170 594-20-7 .05 .3 -­1,1-Dichloropropene -- 77168 563-58-6 .03 .1 -­cis-1,3-Dichloropropene (Z)-1,3-Dichloropropene 34704 10061-01-5 .09 .5 4 4 trans-1,3-Dichloropropene (E)-1,3-Dichloropropene 34699 10061-02-6 .09 .5 44 Diethyl ether 

Ethyl ether 81576 60-29-7 .2 .8 --

Diisopropyl ether 

Diisopropylether (DIPE) 81577 108-20-3 .1 .5 -­

1,2-Dimethylbenzene o-Xylene 77135 95-47-6 .04 .2 1,510,000 

1,3- 1,4-Dimethylbenzene m-& 

p-Xylene 85795 m-108-38-3 .06 .3 1,5 10,000 

p-106-42-3 

(1,1-Dimethylethyl)benzene tert-butylbenzene 77353 98-06-6 .06 .3 --Ethenylbenzene Styrene 77128 100-42-5 .04 .2 1100 

Ethylbenzene 

Phenylethane 34371 100-41-4 .03 .2 1700 

Ethyl methacrylate Ethyl methacrylate 73570 97-63-2 .2 .9 -­Ethyl tert-butyl ether 

Ethyl-t-butyl ether (ETBE) 50004 637-92-3 .05 .3 -­

2-Ethyltoluene o-Ethyltoluene 77220 611-14-3 .06 .3 -­1,1,2,3,4,4-Hexachloro-1,3-butadiene Hexachlorobutadiene 39702 87-68-3 .1 .7 21 1,1,1,2,2,2-Hexachloroethane Hexachloroethane 34396 67-72-1 .2 .9 21 2-Hexanone Methyl butyl ketone (MBK) 77103 591-78-6 .7 4 --Iodomethane Methyl iodide 77424 74-88-4 .1 .6 -­1-Isopropyl-4-methylbenzene 

p-Cymene 77356 99-87-6 .07 .4 -­

Methyl acrylonitrile 

Methacrylonitrile 81593 126-98-7 .6 3 --

Methylbenzene 

Toluene 34010 108-88-3 .05 .3 11000 

(1-Methylethyl)benzene Cumene 77223 98-82-8 .03 .2 -­Methyl methacrylate Methyl-2-methacrylate 81597 80-62-6 .3 2 -­4-Methyl-2-pentanone Methyl isobutyl ketone (

MIK) 78133 108-10-1 .4 2 -­

Methyl-2-propenoate 

Methyl Acrylate 49991 96-33-3 1 7 -­

(1-Methylpropyl)benzene sec-butylbenzene 77350 135-98-8 0.03 0.2 -­Methyl tert-butyl ether 

MTBE 78032 1634-04-4 .2 .8 2,6 20 

Naphthalene -- 34696 91-20-3 .2 1 220 

2-Propenenitrile 

Acrylonitrile 34215 107-13-1 1 6 4.06 

n-Propylbenzene Isocumene 77224 103-65-1 .04 .2 -­

Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 
31 

Table 6. Volatile organic compounds (VOCs) analyzed, laboratory reporting levels, and related U.S. Environmental Protection Agency standards—Continued

USGS Other 

laboratory Chemical Abstract Laboratory laboratory 

parameter Service (CAS) reporting level reporting levels USEPA standard 

Volatile organic compound (VOC) Common name code number (μg/L) (μg/L) (μg/L) 

1,1,1,2-Tetrachloroethane -- 77562 630-20-6 .03 .2 410 

1,1,2,2-Tetrachloroethane -- 34516 79-34-5 .09 .5 2.3 Tetrachloroethene Perchloroethene (PCE) 34475 127-18-4 .1 .5 15 Tetrachloromethane Carbon tetrachloride 32102 56-23-5 .06 .3 15 Tetrahydrofuran Diethylene oxide 81607 109-99-9 2 11 -­1,2,3,4-Tetramethylbenzene Prehitene 49999 488-23-3 .2 1 -­1,2,3,5-Tetramethylbenzene Isodurene 50000 527-53-7 .2 1 --Tribromomethane Bromoform 32104 75-25-2 .06 .3 1,380 1,2,3-Trichlorobenzene -- 77613 87-61-6 .3 1 -­1,2,4-Trichlorobenzene -- 34551 120-82-1 .2 .9 170 1,1,1-Trichloroethane Methylchloroform 34506 71-55-6 .03 .2 1200 1,1,2-Trichloroethane Vinyl trichloride 34511 79-00-5 .06 .2 15 Trichloroethene TCE 39180 79-01-6 .04 .2 15 Trichlorofluoromethane CFC 11, Freon 11 34488 75-69-4 .09 .5 22,000 

Trichloromethane Chloroform 32106 67-66-3 .05 .3 1,380 

1,2,3-Trichloropropane Allyl trichloride 77443 96-18-4 .2 .8 240 1,1,2-Trichloro-1,2,2-trifluoroethane CFC 113, Freon 113 77652 76-13-1 .06 .3 -­1,2,3-Trimethylbenzene Hemimellitene 77221 526-73-8 .1 .6 -­1,2,4-Trimethylbenzene Pseudocumene 77222 95-63-6 .06 -- -­1,3,5-Trimethylbenzene Mesitylene 77226 108-67-8 .04 .2 -­

1U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) (U.S. Environmental Protection Agency, 2002).
2U.S. Environmental Protection Agency Lifetime Health Advisory (HAL) (U.S. Environmental Protection Agency, 2002).
3Total for all trihalomethanes combined cannot exceed 80 μg/L level (U.S. Environmental Protection Agency, 2002).
4U.S. Environmental Protection Agency Risk-Specific Dose at 10-5 Cancer Risk (RSD5) (U.S. Environmental Protection Agency, 2003a, 2003b).
5Total for all xylenes combined cannot exceed the 10,000 μg/L level (U.S. Environmental Protection Agency, 2002).
6The U.S. Environmental Protection Agency drinking-water advisory level ranges from 20-40 μg/L (U.S. Environmental Protection Agency, 2002).
 M

ethods of Investigation 
--------------------------------------------------

32 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

was clean and would not contribute contaminants to future environmental samples; only three inorganic constituents (ammonia 

plus organic nitrogen, calcium, and manganese) and one 

organic constituent (the VOC 1,2,4-trimethylbenzene) were 

detected at trace concentrations in the office blank. The source 

of the 1,2,4-trimethylbenzene was likely the organic-free blank 

water because it was detected in the source-solution blank at a 

much higher concentration. 

Three or four field-equipment blank samples (number of 

blank samples varied based on constituent) were collected during sampling of the Quaternary aquifers and three field-equipment blank samples were collected during sampling of the lower 

Tertiary aquifers and analyzed for major ions, trace elements, 

nutrients, and DOC. Few constituents were detected in fieldequipment blank samples collected during either subunit survey 

(tables 7 and 8); concentrations generally were very small and 

generally much smaller than concentrations measured in environmental samples. Results of field blank samples indicated that 

decontamination procedures used during both subunit surveys 

were adequate, and that field and laboratory contamination of 

environmental samples by inorganic constituents was minimal. 

Three field-equipment blank samples were collected and 

analyzed for pesticide compounds during sampling of both the 

Quaternary and lower Tertiary aquifers. No pesticide compounds were detected in the six field-equipment blanks, indicating that field and laboratory methods did not result in contamination of samples. 

Four field-equipment blank samples were collected and 

analyzed for VOCs during sampling of Quaternary aquifers. Six 

different VOCs were detected in blank samples (total of eight 

VOC detections), five of which also were detected in environmental samples (table 9). All eight detections were below the 

LRL and were qualified as estimated concentrations by the 

NWQL. VOC detections in field-equipment blank samples were 

used to censor associated environmental samples. In this report, 

all compounds that were detected in both the environmental 

sample and associated field-equipment blank sample were censored, and reported as nondetections if the environmental concentration was less than 10 times the concentration of the compound detected in the blank. Consequently, all detections of five 

VOCs (ortho-xylene, meta- and para-xylene, phenylethane, toluene (methylbenzene), and trichloromethane (chloroform)) in 

environmental samples were censored and reported as nondetections because of suspected field or laboratory contamination. 

Toluene, a common component of gasoline, was detected in two 

of four field-equipment blank samples. Toluene is one of four 

VOCs (benzene, toluene, ethylbenzene, and xylenes, commonly 

known as BTEX compounds) that are commonly found together 

in ground water contaminated by gasoline. The toluene detections were censored because the concentrations in the environmental samples were very similar to the blank concentrations 

(table 9) and because no other BTEX compounds were detected 

in most environmental samples with toluene detections. 

Three field-equipment blank samples were collected and 

analyzed for VOCs during sampling of lower Tertiary aquifers. 

Five different VOCs were detected in blank samples (total of six 

VOC detections), two of which (toluene and 1,2,4-trimethylbenzene (pseudocumene)) also were detected in environmental samples (table 10). Consequently, all detections of toluene and 

1,2,4-trimethylbenzene in environmental samples from the 

lower Tertiary aquifers were censored because concentrations in 

environmental samples were very similar to blank concentrations. 

One trip blank was collected during each subunit survey. 

VOCs were not detected in either trip blank. 

Replicate Samples

A replicate sample (duplicate) is a sample collected immediately after the primary ground-water sample (environmental 

sample); both are analyzed for the same constituents to assess 

combined effects of field and laboratory procedures on measurement variability (precision). The relative-percent difference (RPD) was calculated to compare constituent concentrations measured in both samples using the following equation: 

⎛ ⎞ ⎜ sample1-sample2 ⎟

RPD = absolute value ⎜--------------------------------------------------------⎟ × 100 ⎜⎛sample1 + sample2⎞⎟ ⎝⎝ 2 ⎠⎠

RPDs were not calculated for inorganic sample pairs where one 

value was reported as less than the MRL and the other value was 

reported as greater than the MRL or was estimated. 

Four pairs of replicate samples were collected and analyzed for major ions, trace elements, nutrients, and DOC as part 

of the Quaternary aquifers subunit survey (appendix 2-1). 

RPDs for most constituents were less than 10 percent, and indicated very good precision (reproducibility) for most inorganic 

constituents. Exceptions to this generalization were arsenic, 

nickel, ammonia plus organic nitrogen, phosphorus, and orthophosphate. RPDs greater than 10 percent generally were attributable to small concentration differences that resulted in relatively large RPDs because both environmental and replicate 

sample concentrations were small. 

Four pairs of replicate samples were collected and analyzed for the same inorganic constituents (major ions, trace elements, nutrients, and DOC) during the lower Tertiary aquifers 

subunit survey (appendix 2-2). RPDs for most of these constituents were less than 10 percent, and indicated very good precision (reproducibility) for most inorganic constituents. Major 

ions with at least one RPD greater than 10 percent were potassium, sulfate, and fluoride. Numerous trace elements had at 

least one RPD greater than 10 percent: aluminum, arsenic, barium, boron, bromide, chromium, copper, lithium, molybdenum, 

nickel, selenium, vanadium, and zinc. Only one nutrient, orthophosphate, had at least one RPD greater than 10 percent. RPDs 

greater than 10 percent generally were attributable to small concentration differences that resulted in relatively large RPDs 

because both environmental and replicate sample concentrations were small. 
Methods of Investigation 33 

Table 7. Summary of major ions, trace elements, nutrients, and dissolved organic carbon detected in field-equipment blank samples 

and in environmental samples collected during sampling of Quaternary aquifers 

[E, estimated concentration; <, less than; mg/L, milligrams per liter; M, constituent detected but not quantified; N, nitrogen; P, phosphorus; C, carbon] 

Blank samples Environmental samples 

Number of Number of 

detections/number detections/number Range of 

Constituent of samples Concentrations of samples concentrations 

Major ions, in milligrams per liter 

Calcium 2/3 E0.02, 0.28, <0.02 25/25 28.8-525 

Magnesium 2/3 E0.007, 1.68, <0.014 25/25 9.47-1,440 

Sodium 1/3 <0.1, 0.6, <0.1 25/25 4.9-4,530 

Potassium 0/3 <0.24, <0.24, <0.24 25/25 1.38-12.1 

Chloride 0/3 <0.3, <0.3, <0.3 25/25 1-399 

Sulfate 0/3 <0.3, <0.3, <0.3 25/25 4.7-14,600 

Fluoride 0/3 <0.1, <0.1, <0.1 24/25 <0.1-4.7 

Silica 0/3 <0.02, <0.02, <0.02 25/25 11.2-37.5 

Trace elements, in micrograms per liter unless otherwise noted 

Aluminum 1/4 <0.3, M, <1, <0.3 16/25 <1-<5 

Arsenic 0/4 <2, <2, <0.9, <2 10/25 <0.9-4.8 

Barium 0/4 <0.2, <0.2, <1, <0.2 25/25 6.9-210 

Boron 1/4 <2, <2, <12, <3 3/3 E8-235 

Bromide (mg/L) 0/3 <0.01, <0.01, <0.01 23/25 <0.01-0.99 

Chromium 0/4 <.0.2, <0.2, <1, <0.2 11/25 E0.5-9.1 

Cobalt 0/4 <0.3, <0.2, <1, <0.2 11/25 <1-7.04 

Copper 1/4 0.3, <0.2, <1, <0.2 24/25 <1-45.4 

Iron 0/3 <3, <3, <3 13/25 M-6,710 

Lithium 0/1 <0.3 3/3 3.7-471 

Manganese 0/4 <0.1, <0.1, <1, <0.1 21/25 <1-3,800 

Molybdenum 0/4 <0.2, <0.2, <1, <0.2 23/25 <1-9 

Nickel 0/4 <0.5, <0.5, <1, <0.5 25/25 1.41-22.1 

Selenium 0/4 <2.4, <2.4, <0.7, <2.4 10/25 <0.7-29.5 

Strontium 0/4 <0.1, <0.1, <0.2, <0.1 3/3 149-11,700 

Vanadium 0/1 <1 1/3 <1-1 

Thallium 0/4 <0.1, <0.1, <0.9, <0.1 0/3 <1 

Zinc 1/4 M, <0.5, <1, <0.5 18/25 <1-460 

Nutrients and dissolved organic carbon, in milligrams per liter 

Nitrite, as N 0/4 <0.01, <0.01, <0.01, <0.01 5/25 <0.01-0.115 

Nitrite + Nitrate, as N 0/4 <0.05, <0.05, <0.05, <0.05 12/25 <0.05-12.6 

Ammonia, as N 0/4 <0.02, <0.02, <0.02, <0.02 13/25 <0.02-0.427 

Ammonia + organic nitrogen, 1/4 <0.1, <0.1, E0.06, <0.1 23/25 E0.08-2.2 

as N 

Phosphorus, as P 0/4 <0.006, <0.006, <0.006, <0.006 24/25 E0.003-0.07 

Orthophosphate, as P 1/4 0.01, <0.01, <0.01, <0.01 16/25 <0.01-0.058 

Dissolved organic carbon, as C 1/3 10.24, <0.33, <0.33 25/25 0.61-38 

1Detection was attributed to contamination of blank water because of similar concentration (0.25 milligram per liter) in associated source-solution blank. 
34 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 8. Summary of major ions, trace elements, nutrients, and dissolved organic carbon detected in field-equipment blank samples 

and in environmental samples collected during sampling of lower Tertiary aquifers 

E, estimated concentration; <, less than; mg/L, milligrams per liter; M, constituent detected but not quantified; N, nitrogen; P, phosphorus; C, carbon] 

Blank samples Environmental samples 

Number of Number of 

detections/number detections/number Range of 

Constituent of samples Concentrations of samples concentrations 

Major ions, in milligrams per liter 

Calcium 2/3 E0.01, E0.01, <0.02 29/29 0.96-407 

Magnesium 0/3 <0.014, <0.008, <0.014 29/29 0.144-214 

Sodium 0/3 <0.1, <0.1, <0.1 29/29 11.4-1,490 

Potassium 0/3 <0.24, <0.09, <0.24 29/29 0.51-13.6 

Chloride 0/3 <0.3, <0.1, <0.3 29/29 1.3-180 

Sulfate 0/3 <0.3, <0.1, <0.3 29/29 0.8-3,240 

Fluoride 0/3 <0.1, <0.2, <0.1 29/29 0.4-7 

Silica 0/3 <0.1, <0.1, <0.1 29/29 6.1-24.1 

Trace elements, in micrograms per liter unless otherwise noted 

Aluminum 1/3 5, <1, <1 14/29 <1-22 

Antimony 0/3 <1, <0.05, <1 5/29 0.1-6.3 

Arsenic 0/3 <0.9, <0.2, <0.9 20/29 E0.1-7.4 

Barium 0/3 <1, <1, <1 29/29 3.9-113 

Boron 0/3 <12, <7, <12 29/29 26-635 

Bromide (mg/L) 0/3 <0.01, <0.01, <0.01 29/29 0.02-1.21 

Cadmium 0/3 <1, <0.04, <1 5/29 E0.02-9.36 

Chromium 0/2 <0.8, <0.8 8/29 E0.4-1.6 

Cobalt 0/3 <1, <0.01, <1 13/29 E0.01-8.99 

Copper 2/3 1.1, 1.1, <1 25/29 E0.1-28.9 

Iron 0/3 <10, <10, <10 16/29 M-1,540 

Lithium 1/3 <0.3, <0.3, 0.4 29/29 5.6-265 

Manganese 1/3 <1, 0.1, <1 24/29 0.5-230 

Molybdenum 0/3 <1, <0.2, <1 26/29 0.6-4,730 

Nickel 0/3 <1, <0.06, <1 14/29 E0.04-24 

Selenium 0/3 <0.7, <0.3, <0.7 22/29 E0.2-92.5 

Silver 0/3 <1, <1, <1 0/29 <1-<5 

Strontium 2/3 <0.2, E0.05, E0.15 29/29 24.9-6,450 

Thallium 0/3 <0.9, <0.04, <0.9 6/29 E0.03-0.72 

Vanadium 1/3 <1, E0.1, <1 14/29 <0.2-12.2 

Zinc 1/3 2, <1, <1 25/29 <1-153 

Nutrients and dissolved organic carbon, in milligrams per liter 

Nitrite, as N 0/3 <0.01, <0.006, <0.01 8/29 E0.003-0.396 

Nitrite + Nitrate, as N 0/3 <0.05, <0.047, <0.05 17/29 E0.036-17.7 

Ammonia, as N 0/3 <0.02, <0.041, <0.02 25/29 <0.02-4.31 

Ammonia + organic nitrogen, 1/3 <0.1, <0.1, E0.07 28/29 <0.1-3.7 

 as N 

Phosphorus, as P 0/3 <0.006, <0.006, <0.006 24/29 E0.003-0.113 

Orthophosphate, as P 0/3 <0.01, <0.018, <0.01 20/29 <0.01-0.102 

Dissolved organic carbon, as C 0/3 <0.33, <0.33, <0.33 29/29 E0.32-8.2 
35 

Table 9. Summary of volatile organic compounds (VOCs) detected in field-equipment blank samples and respective environmental samples collected during sampling of the Quaternary aquifers[USGS, U.S. Geological Survey; LRL, laboratory reporting level; μg/L, micrograms per liter; E, estimated concentration; ND, not detected] 

Number of Concentrations Number of 

USGS detections in blank Uncensored uncensored 

laboratory samples/number of Environmental environmental detections/number

Volatile organic compound parameter blank samples sample LRL Blank sample sample range of environmental 

(VOC) Common name code collected ( μg/L) (μg/L) (μg/L) samples collected 

Dichloromethane Methylene chloride 34423 1/4 0.4 E0.1 ND 0/25 1,2-Dimethylbenzene ortho-xylene 77135 1/4 0.04 E0.01 ND - E0.02 1/25 1,3- & 1,4-Dimethylbenzene meta- and para-xylene 85795 1/4 0.06 E0.06 ND - E0.03 1/25 

Ethylbenzene Phenylethane 34371 1/4 0.03 E0.02 ND - E0.04 1/25 Methylbenzene Toluene 34010 2/4 0.05 1E0.005, E0.01 ND - E0.08 10/25 

Trichloromethane Chloroform 32106 2/4 0.05 E0.01, E0.01 ND - E0.01 3/25 

1Volatile organic compound (VOC) also was detected at the same concentration in the source-solution blank associated with this sample. 

Methods of Investigation 
36 

Table 10. Summary of volatile organic compounds (VOCs) detected in field-equipment blank samples and respective environmental samples collected during sampling of the 

lower Tertiary aquifers

[USGS, U.S. Geological Survey; L

R

L, laboratory reporting level; μg/L, micrograms per liter; E, estimated concentration; ND, not detected] 

Concentrations Number of 

USGS Number of detections Uncensored uncensored 

laboratory in blank samples/ Environmental environmental detections/number of 

Volatile organic compound parameter number of blank sample LRL Blank sample sample range environmental

(VOC) Common name code samples collected (μg/L) (μg/L) (μg/L) samples collected 

1,2-Dimethylbenzene ortho-xylene 77135 1/3 0.04 

E0.04 ND 0/29 

1,3- & 1,4-Dimethylbenzene meta- and para-xylene 85795 1/3 0.06 

E0.08 ND 0/29 

Ethylbenzene 

Phenylethane 34371 1/3 0.03 

E0.03 ND 0/29 

Methylbenzene 

Toluene 34010 1/3 0.05 1E0.01 

N

D - E0.01 1/29 

1,2,4-Trimethylbenzene 

Pseudocumene 77222 2/3 0.06 1E0.02, E0.05 

ND - 0.2 14/29 

1Volatile organic compound (VOC) also was detected in the source-solution blank associated with this sample. 

Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 
Methods of Investigation 37 

Four pairs of replicate samples were collected and analyzed 

for pesticide compounds during the Quaternary aquifers subunit 

survey. Eleven different pesticide compounds were detected in 

at least one of the environmental or replicate samples of the four 

pairs (appendix 2-3). The measured concentrations in both the 

environmental and replicate samples for 8 of 44 paired compounds were below the LRL and were reported as estimated concentrations. RPDs for pesticide compounds detected at concentrations greater than the LRL were all less than 5 percent, 

indicating very good precision (reproducibility). RPDs were 

higher for some pesticides with estimated concentrations, but 

these RPDs should be used with caution because estimated concentrations have very poor precision. 

Four pairs of replicate samples were collected and analyzed 

for pesticides during the lower Tertiary aquifers study. Pesticides 

were not detected at concentrations greater than the LRL in either 

the environmental or replicate samples in any sample pair. 

Four pairs of replicate samples were collected from the Quaternary aquifers for VOC analysis. Thirteen different VOCs were 

detected in either the environmental or replicate sample of at least 

one of the four pairs (appendix 2-4). Most uncensored VOC concentrations were smaller than the LRL and were estimated concentrations. RPDs were less than 15 percent for all VOCs except 

1,2,4-trimethylbenzene. Of the three pairs of replicate samples 

with at least one detection of 1,2,4-trimethylbenzene, RPDs in 

two sample pairs were greater than 100 percent, and the RPD 

could not be calculated in the third sample pair because the VOC 

was only detected in one sample. This poor replication indicates 

that reported 1,2,4-trimethylbenzene concentrations and detections may be unreliable and should be used with caution. 

Four pairs of replicate samples were collected from the 

lower Tertiary aquifers for VOC analysis (appendix 2-5). Three 

different VOCs were detected in either the environmental or replicate sample of at least one of the four pairs, but concentrations 

were not greater than the LRL in both the environmental and replicate samples for any given sample pair. RPDs for two of three 

detected VOCs were less than 15 percent. Of the three pairs of 

replicate samples with at least one detection of 1,2,4-trimethylbenzene, RPDs in two sample pairs were greater than 100 percent, and the RPD could not be calculated in the third sample pair 

because the VOC was detected only in one sample. In addition, 

as noted earlier, 1,2,4-trimethylbenzene was detected in two of 

three field-equipment blank samples and one source-solution 

blank. Because of both QA/QC problems, 1,2,4-trimethylbenzene detections in the lower Tertiary aquifers were censored and 

reported as nondetections. 

Field-Matrix Spike Samples

Field-matrix spike samples for pesticides and VOCs were 

analyzed to evaluate bias and variability from ground-water 

matrix interference or potential degradation of constituent concentrations during sample processing, storage, and analysis. 

Field-matrix spike samples were collected during the field-matrix 

spiking process by injecting known concentrations of selected 

pesticides and VOCs into replicate environmental samples. 

Pesticide field-matrix spike samples were collected from 

Quaternary aquifers and analyzed using two analytical methods. 

Three pairs of pesticide field-matrix spike and field-matrix spike 

replicate samples were analyzed using C-18 solid-phase extraction and capillary-column gas chromatography/mass spectrometry (appendix 3-1) (Zaugg and others, 1995). While spike recoveries for several pesticide compounds were greater than 

120 percent, tebuthiuron was the only pesticide compound 

detected in environmental samples from Quaternary aquifers; this 

suggests the tebuthiuron concentrations in environmental samples were likely biased high. 

Only one pair of samples collected from Quaternary aquifers was analyzed using graphitized carbon-based solid-phase 

extraction and high-performance liquid chromatography/mass 

spectrometry (Furlong and others, 2001, 2003). This new laboratory analytical method was in development by the USGS NWQL 

at the time of sampling. About one-third of sample pairs had 

recoveries between 0 and 60 percent, one-third between 60 and 

120 percent, and one-third above 120 percent (appendix 3-2). 

During development of this new method over one year (Furlong 

and others, 2001, 2003), median recoveries for 17 compounds 

were less than 60 percent and 2 were greater than 120 percent and 

these compound concentrations were reported as estimated 

(shown as open squares in Appendix 3-2). Eight additional compounds also were qualified as estimated because the variability in 

the recovery of the compound was outside the acceptable range 

(Furlong and others, 2001, 2003). The discrepancy between 

recoveries reported during method development and the fieldmatrix spike recoveries reported for samples collected during the 

Quaternary aquifers subunit survey is likely due to differences in 

sample size—many more samples were used for method development than were collected for the Quaternary aquifers subunit 

survey. Strict adherence to NAWQA protocols should have minimized differences but the possibility exists of sample degradation during sampling, preservation, or transport. The highly variable results of the sample spiking indicates that the concentrations obtained using the new method (Furlong and others, 

2001, 2003) during the Quaternary aquifers subunit survey 

should be considered estimates. 

Pesticide field-matrix spike samples collected from the 

lower Tertiary aquifers were analyzed using the same two analytical methods as for the Quaternary aquifer samples; however, the 

graphitized carbon-based solid-phase extraction and highperformance liquid chromatography/mass spectrometry analytical method (Furlong and others, 2001, 2003) was published by 

the time of sampling and was no longer in development. Four 

sets of field-matrix spike samples were collected during sampling 

of the lower Tertiary aquifers and analyzed using both pesticide 

analytical methods (appendixes 3-3 and 3-4). 

Spike recoveries of most compounds for the solid-phase 

extraction and capillary-column gas chromatography/mass spectrometry were near 100 percent. Most recoveries of tebuthiuron 

and thiobencarb were greater than 100 percent. Recoveries of 

chlorpyrifos, p,p’-DDE, deethylatrazine, disulfoton, cispermethrin, phorate, propargite, and terbufos consistently had 

recoveries less than 100 percent. Of these pesticide compounds 
38 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

with recoveries consistently greater than 100 percent, deethylatrazine was the only compound detected in environmental samples (1 sample) and the concentration may be biased high. Terbuthylazine was never recovered in the spiked sample, and would 

therefore not likely have been detected in an environmental sample if it was present. 

Spike recoveries for the graphitized carbon-based solidphase extraction and high-performance liquid chromatography/ 

mass spectrometry analytical method for lower Tertiary aquifers 

were variable and most recoveries were biased low (appendix 

3D). Three pesticide compounds—bentazon, clopyralid, and 

deethylisopropylatrazine—were detected in samples collected 

from lower Tertiary aquifers using this analytical method 

(table 5). These pesticide compounds were biased low in fieldmatrix spike samples, so sample concentrations of these three 

compounds also were likely biased low. 

Five VOC field-matrix spike samples (two pairs and one 

single sample) were collected from Quaternary aquifers and analyzed using GC/MS (Connor and others, 1998). Most of the 

spiked VOC recoveries were between 40 and 100 percent (appendix 3-5). The median spike recoveries of the five field-spiked 

samples for all VOCs were between 50 and 102 percent. These 

data show that for most VOC compounds the values for the environmental samples should show either no bias or a slight low 

bias. The field-spiked samples have generally lower concentrations than the laboratory-spike samples, and may be an indication 

of some sample degradation. 

Six field-matrix spike samples (three sample pairs) were 

collected from lower Tertiary aquifers and analyzed for VOCs 

using GC/MS. Most of the spiked VOC recoveries were between 

60 and 100 percent (appendix 3-6). The median field-spiked 

recoveries of the six samples for all VOCs were between 54 and 

104 percent. The median spike recoveries for the laboratory 

spikes associated with the field-matrix spike sample were 

between 88 and 131 percent. These data show that for most VOC 

compounds the field-spiked samples and the laboratory-spiked 

samples are comparable and that environmental samples have 

minimal bias. 

Major-Ion Balances 

Major-ion data were quality assured by calculating ion balances. The ion balance was calculated (in milliequivalents per 

liter) as the total dissolved-cation equivalence minus the total 

dissolved-anion equivalence divided by the total equivalence of 

ions dissolved in solution. Calculated balances for all samples 

from both aquifers were less than 6 percent, which was considered acceptable for both subunit surveys. 

Statistical Methods 

Water-quality data commonly are not normally distributed 

and some constituents concentrations are less than laboratory 

reporting levels (censored data). In addition, nonnormality is difficult to detect with small sample sizes. Nonparametric statistics 

do not rely on an assumption that data are normally distributed, 

are resistant to the effects of outliers, and are more appropriate 

when sample sizes are small (Helsel and Hirsch, 1992). Therefore, nonparametric statistical methods commonly are used to 

describe and analyze water-quality data in this report. 

Summary statistics of constituent concentrations that 

included censored data were estimated using robust methods 

(Helsel and Cohn, 1988; Helsel and Hirsch, 1992). Robust methods use distributions fit to data that are greater than the reporting 

levels to estimate summary statistics. In this report, summary statistics for most data sets with censored values were estimated 

using log-probability regression. 

Boxplots were constructed for many constituents to summarize data and to qualitatively compare concentrations between the 

types of aquifers. For convenience, results from quantitative 

comparisons (rank-sum tests) of constituents between the Quaternary and lower Tertiary aquifers are presented on the boxplots. 

Boxplots constructed for most constituents with censored values 

were truncated at the highest laboratory reporting level (Helsel 

and Hirsch, 1992). Many trace elements had multiple laboratory 

reporting levels, so boxplots were constructed showing the highest and lowest laboratory reporting level; the boxplot was truncated at the lowest laboratory reporting level. 

The two-sided version of the rank-sum test (Helsel and Hirsch, 1992) was the nonparametric hypothesis test used to determine the probability that median concentrations of various constituents were the same between Quaternary and lower Tertiary 

aquifers. The rank-sum test, like most nonparametric hypothesis 

tests, requires no assumptions about population distribution, is 

resistant to outliers and censoring, and is more appropriate for 

small sample sizes where nonnormality is difficult to detect. The 

null hypothesis of identical median concentrations between aquifers was rejected if the probability (p-value) of obtaining identical 

medians by chance was less than 0.05. 

Two nonparametric methods were used to calculate correlation coefficients to compare constituent concentrations with 

selected continuous variables. Spearman’s rho and Kendall’s tau 

were used to measure the strength of monotonic correlation 

between two continuous variables (Helsel and Hirsch, 1992). 

Spearman’s rho was calculated when sample sizes were larger 

than 20; Kendall’s tau was calculated when samples sizes were 

smaller than 20 (Helsel and Hirsch, 1992). Correlation coefficients are calculated using ranks of data rather than actual data 

values; therefore, test statistics are resistant to outliers and can be 

used for datasets with moderate censoring. Spearman’s rho and 

Kendall’s tau are dimensionless and range between –1 and 1. 

When one variable increases as the second increases, the coefficient is positive; if the variables vary in opposite directions, the 

coefficient is negative. If a strong and statistically significant correlation is observed, tau and rho, like any correlation coefficients, 

do not explain the cause of the correlation. Correlation coefficients were considered statistically significant when probabilities 

(p-values) were less than 0.05; the null hypothesis of no correlation between variables was rejected if the probability of obtaining 

a correlation by chance was less than 0.05. In this report, 

p-values greater than 0.05 but less than 0.08, although not signif­
icant with an alpha level of 0.05, were considered indicative of 

“weak” correlation between two continuous variables of interest. 

Ground-Water Quality 

Natural processes and human activities can affect groundwater quality. The primary natural factors that can affect the type 

and quantities of dissolved constituents in ground water include 

the source and chemical composition of recharge water, lithologic and hydrologic properties of the geologic unit, various 

chemical processes occurring within the geologic unit, the 

amount of time the water has remained in contact with the geologic unit (residence time), and mixing of waters from different 

geologic units. Many different human activities can affect 

ground-water quality—effects are often negative and some can 

impair the quality of water in relation to some uses. Because of 

the generally rural nature of the area studied, the number of 

potential sources of ground-water contamination to aquifers studied in the Bighorn Basin are somewhat small. Potential sources 

include both point sources such as leachate from individual septic 

systems and leaks and spills from above-ground fuel and chemical storage, and nonpoint sources such as infiltration and return 

flow from irrigated cropland and pasture, agricultural and nonagricultural application of pesticides and fertilizers, and infiltration 

of runoff from roads. The apparent age of ground water was 

determined for this study to provide an indication of the relative 

vulnerability of the aquifers to contamination from these potential sources. 

Ground-water quality data presented in this report are compared with several U.S. Environmental Protection Agency 

(USEPA) drinking-water standards for finished (treated) water 

established in the Safe Drinking Water Act. The USEPA has 

established standards for physical properties and chemical constituents in drinking water that may have adverse effects on 

human health or that may cause cosmetic effects (such as skin or 

tooth discoloration) or aesthetic effects (such as color, taste, or 

odor) of water. The Maximum Contaminant Level (MCL) is 

legally enforceable and health-based and is the maximum permissible level for a constituent in drinking water that is delivered 

to a user of a public-water system (U.S. Environmental Protection Agency, 2002). The Health Advisory Level (HAL) is a nonenforceable standard that establishes acceptable constituent concentrations for different exposure periods (1 day, 10 day, longterm, and lifetime). A Lifetime HAL is the concentration of a 

chemical that would not result in any known or anticipated 

adverse noncarcinogenic health effects over a lifetime of exposure (70 years) (U.S. Environmental Protection Agency, 2002). 

The Risk-Specific Dose at 10-5 cancer risk (RSD5) is a concentration of a chemical with a specific risk level under certain exposure conditions over a lifetime (70 years) (U.S. Environmental 

Protection Agency, 2002, 2003a, 2003b). An action level (AL) is 

a concentration of a chemical, which, if exceeded, requires treatment by the public-water supplier (U.S. Environmental Protection Agency, 2002, 2003a, 2003b). Secondary drinking-water 

Ground-Water Quality 39 

regulations (U.S. Environmental Protection Agency, 2002), such 

as Secondary Maximum Contaminant Levels (SMCLs), are nonenforceable standards related to the cosmetic or aesthetic effects 

of drinking water (standards are not health-based) and are the 

maximum recommended levels for constituents in drinking 

water. Although these USEPA standards only apply to drinking 

water supplied by public-water systems, and not to individual 

well owners, the levels are useful to determine the suitability of 

water collected from wells for human consumption. 

The reader should note that drinking-water standards established by the USEPA are based on total constituent concentrations, which refer to combined concentrations of both dissolved 

and suspended phases of the water sample. Results reported 

herein by the USGS as dissolved-constituent concentrations may 

have been less than those obtained if samples were analyzed for 

total constituent concentrations. 

Ground-water samples collected from wells completed in 

Quaternary and lower Tertiary aquifers were analyzed for physical characteristics, major ions, trace elements, nutrients, DOC, 

radionuclides, pesticide compounds, and VOCs. Results of these 

analyses are described and summarized in this section of the 

report; individual analytical results for all constituents analyzed 

in samples from all wells are presented in Appendixes 4-9 in the 

back of the report. 

Ground-Water Age 

The apparent age of ground water is important because it 

can be used to determine the relative vulnerability to contamination from human activities at the land surface. Aquifers with 

“modern” or recently recharged water (waters that entered or 

recharged aquifers within the last 50 years) generally are more 

vulnerable than aquifers with “old” waters (waters older than 

50 years). 

Tritium (3

H), a radioactive isotope of hydrogen (H) present 

in some water molecules, was used to determine the apparent age 

of ground water sampled. Tritium in Quaternary and lower Tertiary aquifers ultimately came from precipitation that infiltrated 

downward to the aquifers (ground-water recharge). Tritium has 

a half-life of 12.43 years so its concentration in water decreases 

with time through radioactive decay. Atmospheric concentrations of tritium increased above natural levels beginning in the 

early 1950’s as a result of thermonuclear weapons testing—this 

testing affected precipitation throughout the world. Therefore, 

tritium in precipitation that recharged aquifers during and after 

thermonuclear device testing can be measured in ground-water 

samples to estimate when water became isolated from the atmospheric source of tritium and entered the aquifers. 

Tritium concentrations have varied considerably, both spatially and temporally (Michel, 1989), so tritium is often used to 

qualitatively age-date ground waters. Tritium concentrations are 

expressed in picocuries per liter (pCi/L) or tritium units (TU) 

where 1 TU is equal to 1 3

H atom in 1018 atoms of H, or 1 TU is 

equal to about 3.24 pCi/L (Plummer and others, 1993). In general, tritium concentrations in ground water recharged prior to 
40 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

nuclear device testing (referred to as “old” water in this report) 

would be less than about 0.8 TU or 2.6 pCi/L; greater concentrations would indicate ground water that has been recharged after 

the early 1950’s when atmospheric thermonuclear device testing 

began (referred to as “modern” water in this report) or ground 

water that is a mixture of old and modern waters (Plummer and 

others, 1993; Clark and Fritz, 1997). 

All water samples collected from the Quaternary aquifers 

contained greater than 0.8 TU of tritium, indicating that the 

waters are modern and were recharged after the early 1950’s. In 

contrast, tritium concentrations in 14 of 29 samples from the 

lower Tertiary aquifers were smaller than 0.8 TU, indicating that 

the waters are old; concentrations in the remaining 15 samples 

were greater than 0.8 TU, indicating that these waters are modern 

or a mixture of old and modern waters. 

Tritium concentrations in lower Tertiary aquifers significantly decreased with increasing depth to the first open well 

interval (p-value=0.0075; Spearman’s rho=-0.5145). Ground 

water from greater well depths would be expected to have lower 

tritium concentrations due to longer ground-water flowpath or 

longer residence time in comparison to ground water from shallower well depths. 

Physical Characteristics 

Onsite measurements of physical characteristics of ground 

water from both Quaternary and lower Tertiary aquifers (appendixes 4-1 and 4-2) are summarized and compared to applicable 

USEPA standards in tables 11 and 12 and in boxplots (fig. 9). 

Median concentrations of pH and dissolved oxygen were significantly different between aquifers (p<0.0001 and p=0.0079, 

respectively, fig. 9). Field pH measurements for all samples from 

both aquifers were alkaline (pH greater than 7.0) and all measurements from the Quaternary aquifers were within the USEPA 

SMCL of 6.5 to 8.5; 7 of 29 field pH measurements from the 

lower Tertiary aquifers were greater than the upper SMCL value 

(8.5). The SMCL for turbidity, an indicator of the “cloudiness” 

of water, was exceeded in 2 of 25 samples from the Quaternary 

aquifers and 3 of 25 samples from the lower Tertiary aquifers. 

The amount of dissolved oxygen (DO) in ground water can 

be used to infer the oxidation/reduction (redox) state of ground 

water. The redox state can affect the solubility and speciation of 

dissolved constituents in ground water. Ground water with little 

to no DO indicates reducing (anoxic or anaerobic) or nearreducing conditions, and ground water with DO indicates oxygenated (oxic or aerobic) conditions. DO concentrations generally were low in waters from both aquifers, although concentrations varied over a large range for both aquifers and indicate both 

oxic and anoxic conditions (tables 11 and 12; fig. 9). The median 

concentration of 0.7 milligrams per liter (mg/L) for the Quaternary aquifers was significantly different than the median concentration of 0.3 mg/L for the lower Tertiary aquifers (p-value= 

0.0079, fig. 9). DO concentrations were not reported for 3 of 

29 lower Tertiary wells sampled because of oxygen introduced 

into the sampled water as a result of water cascading down the 

well casing during purging. 

Concentrations of DO in ground water generally are related 

to the amount of infiltrating water, the amount of DO in this 

water, the amount of organic carbon or material in the aquifer 

sediments (solid organic carbon) and dissolved in ground water 

(dissolved organic carbon), and the rate of oxidation of the 

organic material. Modern waters would be expected to have 

more DO than older waters because older water would contact 

more aquifer material (and possibly organic carbon), and dissolved oxygen is decreased during oxidation of organic carbon. 

This hypothesis was confirmed as DO in the lower Tertiary aquifers significantly increased with increasing tritium concentrations 

(p-value=0.025; Spearman’s rho=0.4487). The lower DO in both 

aquifers could indicate oxidation of carbon during infiltration and 

movement of water through aquifers. In this report, concentrations of DO were used as an indication of the redox conditions of 

waters in the aquifers sampled. 

Major ions and Related Water-Quality Characteristics 

Major ions comprise most of the dissolved constituents in 

ground water and generally occur naturally as a result of recharge 

composition and interactions between water and soil or rock. 

Water samples from both types of aquifers were analyzed for the 

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

sulfate, and fluoride. Silica, an uncharged species, is described 

with the major ions for convenience. Alkalinity as CaCO3 (calcium carbonate), a measure of the acid-buffering capacity of a filtered water sample, was determined onsite and in the laboratory. 

Bicarbonate and carbonate were calculated from alkalinity values 

measured onsite (Hem, 1985). The major ions, and general 

water-quality characteristics calculated from their measurement, 

are summarized and compared to applicable USEPA standards in 

tables 11 and 12 and in boxplots (fig. 10). Results from individual analyses are presented in appendixes 5-1 and 5-2. The reader 

also is referred to both appendixes for selected water-quality 

characteristics calculated from or related to major-ion concentrations but not discussed in the text of this report or shown in fig. 10 

(for example, specific conductance and sodium-adsorption ratio). 

Median concentrations of three cations (calcium, magnesium, sodium) were significantly different (p-values less than 

0.05) between aquifers (fig. 10). Median concentrations of the 

anion fluoride, silica, and hardness also were significantly different. 

Several anions were detected at concentrations greater than 

USEPA standards. The SMCL for chloride (250 mg/L) was 

exceeded in only one sample from the Quaternary aquifers. Sulfate concentrations in waters from both types of aquifers frequently were larger than the SMCL of 250 mg/L; samples from 

15 of 25 wells in the Quaternary aquifers and samples from 19 of 

29 wells in the lower Tertiary aquifers exceeded the standard. A 

common source of sulfate in ground water related to human activities probably is fertilizer. The probable source of most natural 
Table 11. Summary of inorganic ground-water quality, Quaternary aquifers 

Ground-Water Quality 41 

Table 11. Summary of inorganic ground-water quality, Quaternary aquifers 

[USGS, U.S. Geological Survey; NWIS, National Water Information System; MRL, minimum reporting level; USEPA, U.S. Environmental Protection Agency; 

°C, degrees Celsius; --, not applicable; SMCL, Secondary Maximum Contaminant Level; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μS/cm, 

microsiemens per centimeter at 25° Celsius; HCO3, bicarbonate; CaCO3, calcium carbonate; E, estimated concentration; MCL, Maximum Contaminant Level; 

HAL, Health Advisory Level; C, carbon; AL, Action Level; PMCL, proposed Maximum Contaminant Level; AMCL, proposed Alternate Maximum Contaminant 

Level] 

Number of USGS USEPA drinking- Minimum Median Maximum 

detections/ NWIS water standards concen­ concen­ concennumber of parameter Highest Lowest or health tration or tration or tration or 

Constituent or characteristic samples code MRL MRL advisories value value value 

Physical characteristics 

Water temperature (°C) 25/25 00010 -- -- -- 8 11.5 17 

pH, field (standard units) 25/25 00400 -- -- 6.5-8.5 (SMCL) 6.9 7.3 7.7 

Turbidity (NTU) 25/25 61028 -- -- 5.0 (SMCL) <0.1 1.2 710 

Dissolved oxygen (mg/L) 25/25 00300 -- -- -- .3 .7 6.9 

Major ions and related water-quality characteristics, in milligrams per liter unless otherwise noted, dissolved 

(sample filtered through 0.45-micrometer filter) 

Calcium 25/25 00915 -- -- -- 28.8 93.6 525 

Magnesium 25/25 00925 -- -- -- 9.47 40.7 1,440 

Sodium 25/25 00930 -- -- -- 4.9 201 4,530 

Potassium 25/25 00935 -- -- -- 1.38 3.96 12.1 

Bicarbonate (mg/L as HCO3) 25/25 00453 -- -- -- 143 392 1,670 

Chloride 25/25 00940 -- -- 250 (SMCL) 1 12 399 

Sulfate 25/25 00945 -- -- 250 (SMCL) 4.7 412 14,600 

Fluoride 24/25 00950 0.1 0.1 4.0 (MCL) <.1 .4 4.7 

2.0 (SMCL) 

Silica 25/25 00955 -- -- -- 11.2 E18.3 37.5 

Dissolved solids (mg/L) 25/25 70300 -- -- 500 (SMCL) 128 956 24,300 

Alkalinity, field (mg/L as CaCO3) 25/25 39086 -- -- -- 117 321 1,370 

Hardness, total (mg/L as CaCO3) 25/25 00900 calculated calculated -- 110 330 6,800 

Specific conductance (μS/cm) 25/25 00095 -- -- -- 240 1,420 21,500 

Sodium-adsorption ratio (SAR) 25/25 00931 calculated calculated -- .2 3 29 

Trace elements, in micrograms per liter unless otherwise noted, dissolved 

(sample filtered through 0.45-micrometer filter) 

Aluminum 16/25 01106 5 1 50-200 (SMCL) <1 11.4 <5 

Antimony 0/25 01095 5 1 -- <1 <1 <5 

Arsenic 10/25 01000 2 .9 10 (MCL) <.9 11.4 4.8 

Barium 25/25 01005 -- -- 2,000 (MCL) 6.9 26 210 

Beryllium 0/25 01010 5 1 4 (MCL) <1 <1 <5 

Boron 3/3 01020 -- -- 600 (Draft E8 119 235 

HAL) 

Bromide (mg/L) 23/25 71870 .01 .01 -- <.01 .05 .99 

Cadmium 0/25 01025 5 1 5 (MCL) <1 <1 <5 

Chromium 11/25 01030 4 .8 100 (MCL) E.5 1

.65 9.1 

Cobalt 11/25 01035 5 1 -- <1 1

.77 7.04 

Copper 24/25 01040 1 1 1,300 (AL) <1 3.4 45.4 

1,000 (SMCL) 

Iron 13/25 01046 30 10 300 (SMCL) <10 1

12.5 6,710 

Lead 0/25 01049 5 1 15 (AL) <1 <1 <5 

Lithium 3/3 01130 -- -- -- 3.7 14.8 471 

Manganese 21/25 01056 1 1 50 (SMCL) <1 146 3,800 

Molybdenum 23/25 01060 1 1 40 (HAL) <1 2.8 9 
42 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 11. Summary of inorganic ground-water quality, Quaternary aquifers—Continued 

Number of USGS USEPA drinking- Minimum Median Maximum 

detections/ NWIS water standards concen­ concen­ concennumber of parameter Highest Lowest or health tration or tration or tration or 

Constituent or characteristic samples code MRL MRL advisories value value value 

Trace elements, in micrograms per liter unless otherwise noted, dissolved 

(sample filtered through 0.45-micrometer filter)--Continued 

Nickel 25/25 01065 -- -- 100 (HAL) 1.41 3.43 22.1 

Selenium 10/25 01145 2.4 0.7 50 (MCL) <.7 1.7 29.5 

Silver 0/25 01075 5 1 100 (HAL/ <1 <1 <5 

SMCL) 

Strontium 3/3 01080 -- -- 17,000 (HAL) 149 585 11,700 

Thallium 0/3 01057 .9 .9 2 (MCL) <.9 <.9 <.9 

Vanadium 1/3 01085 1 1 -- <1 <1 1 

Zinc 18/25 01090 1 1 2,000 (HAL) <1 2.3 460 

5,000 (SMCL) 

Nutrients, in milligrams per liter, dissolved (sample filtered through 0.45-micrometer filter), 

and dissolved organic carbon 

Nitrite, as nitrogen 5/25 00613 .01 .01 1 (MCL) <.01 .00045 .115 

Nitrite + nitrate, as nitrogen 12/25 00631 .05 .05 10 (MCL) <.05 .19 12.6 

Ammonia, as nitrogen 13/25 00608 .02 .02 30 (HAL) <.02 .02 .427 

Ammonia + organic nitrogen, as 23/25 00623 .1 .1 -- E.08 .23 2.2 

nitrogen 

Phosphorus, as phosphorus 24/25 00666 .006 .006 -- E.003 .012 .07 

Orthophosphate, as phosphorus 16/25 00671 .01 .01 -- <.01 .013 .058 

Dissolved organic carbon (mg/L as 25/25 00681 -- -- -- .61 3.1 38 

C) 

Radionuclides, in picocuries per liter unless otherwise noted, dissolved 

(sampled filtered through 0.45-micrometer filter) 

Gross-alpha activity 16/24 04126 3 3 2

15 (MCL) <3 7.42 121 

Gross-beta activity 15/24 03515 4 4 -- <4 6.20 48.8 

Radium-224 25/25 50833 -- -- -- 3

-.12 4.58 10.6 

Radium-226 25/25 09503 -- -- 55(MCL) 3-.03 4

.11 .26 

Radium-228 25/25 81366 -- -- 55 (MCL) .33 .54 2.11 

Radon-222 (unfiltered) 25/25 82303 -- -- 300 (PMCL) 325 682 1,360 

4,000 (AMCL) 

Tritium (unfiltered) 25/25 07000 -- -- -- 20.2 51.5 101 

Uranium (μg/L) 23/25 22704 <1 <1 30 (MCL) <1 6.35 163 

1Median value was less than highest minimum reporting level and was estimated using log-probability regression (Helsel and Cohn, 1988).
 2Not including radon or uranium.
 3

Negative value indicates measurement was less than background radiation level at time of analysis.
 4Negative values not included in summary statistics calculations.
 5Maximum contaminant level (MCL) is for the sum of radium-226 and radium-228.

Table 12. Summary of inorganic ground-water quality, lower Tertiary aquifers 

Ground-Water Quality 43 

Table 12. Summary of inorganic ground-water quality, lower Tertiary aquifers 

[USGS, U.S. Geological Survey; NWIS, National Water Information System; MRL, minimum reporting level; USEPA, U.S. Environmental Protection Agency; 

°C, degrees Celsius; --, not applicable; SMCL, Secondary Maximum Contaminant Level; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μS/ 

cm, microsiemens per centimeter at 25° Celsius; HCO3, bicarbonate; CaCO3, calcium carbonate; E, estimated concentration; MCL, Maximum Contaminant 

Level; HAL, Health Advisory Level; C, carbon; AL, Action Level; NC, not calculated; PMCL, Proposed Maximum Contaminant Level; AMCL, proposed 

Alternate Maximum Contaminant Level] 

USGS USEPA drinking- Minimum Median Maximum 

Number of NWIS water standards concen­ concen­ concendetections/ parameter Highest Lowest or health tration or tration or tration or 

Constituent or characteristic samples code MRL MRL advisories value value value 

Physical characteristics 

Water temperature (°C) 29/29 00010 -- -- -- 8 12 14.5 

pH, field (standard units) 29/29 00400 -- -- 6.5-8.5 (SMCL) 6.7 8.1 9.3 

Turbidity (NTU) 29/29 61028 -- -- 5.0 .1 .6 160 

Dissolved oxygen (mg/L) 26/26 00300 -- -- -- .1 .3 8 

Major ions and related water-quality characteristics, in milligrams per liter unless otherwise noted, dissolved 

(sample filtered through 0.45-micrometer filter) 

Calcium 29/29 00915 -- -- -- .96 29.6 407 

Magnesium 29/29 00925 -- -- -- .144 10.6 214 

Sodium 29/29 00930 -- -- -- 11.4 276 1,490 

Potassium 29/29 00935 -- -- -- .51 2.61 13.6 

Bicarbonate (mg/L as HCO3) 29/29 00453 -- -- -- 186 451 1,070 

Chloride 29/29 00940 -- -- 250 (SMCL) 1.3 16.5 180 

Sulfate 29/29 00945 -- -- 250 (SMCL) .8 576 3,240 

Fluoride 29/29 00950 -- -- 4.0 (MCL) .4 1 7 

2.0 (SMCL) 

Silica 29/29 00955 -- -- -- 6.1 7.1 24.1 

Dissolved solids (mg/L) 29/29 70300 -- -- 500 (SMCL) 352 1,300 5,800 

Alkalinity, field (mg/L as CaCO3) 24/24 39086 -- -- -- 186 370 874 

Hardness, total (mg/L as CaCO3) 29/29 00900 calculated calculated -- 3 130 1,900 

Specific conductance (μS/cm) 29/29 00095 -- -- -- 607 1,860 7,480 

Sodium-adsorption ratio (SAR) 29/29 00931 calculated calculated -- .2 27 58 

Trace elements, in micrograms per liter unless otherwise noted, dissolved 

(sample filtered through 0.45-micrometer filter) 

Aluminum 14/29 01106 3 1 50-200 (SMCL) <1 1 22 

Antimony 5/29 01095 1 .05 -- .1 1.01 6.3 

Arsenic 20/29 01000 1.8 .2 10 (MCL) E.1 1.74 7.4 

Barium 29/29 01005 -- -- 2,000 (MCL) 3.9 9.6 113 

Beryllium 2/25 01010 5 .06 4 (MCL) E.04 NC E.52 

Boron 29/29 01020 -- -- 600 (Draft HAL) 26 184 635 

Bromide (mg/L) 29/29 71870 .01 .01 -- .02 .11 1.21 

Cadmium 5/25 01025 5 .04 5 (MCL) E.02 1.03 9.36 

Chromium 8/29 01030 1 .8 100 (MCL) E.4 .5 1.6 

Cobalt 13/29 01035 2 1 -- E.01 .13 8.99 

Copper 25/29 01040 1 1 1,300 (AL) E.1 2.2 28.9 

1,000 (SMCL) 

Iron 16/29 01046 50 10 300 (SMCL) <10 113.7 1,540 

Lead 7/25 01049 5 1 15 (AL) E.08 1.09 .36 

Lithium 29/29 01130 -- -- -- 5.6 31.7 265 

Manganese 24/29 01056 1 1 50 (SMCL) .5 6.5 230 

Molybdenum 26/29 01060 5 1 40 (HAL) .6 1

2.4 4,730 

Nickel 14/29 01065 2 .06 100 (HAL) E.04 1.16 24 
44 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Table 12. Summary of inorganic ground-water quality, lower Tertiary aquifers—Continued 

USGS USEPA drinking- Minimum Median Maximum 

Number of NWIS water standards concen- concen- concendetections/ parameter Highest Lowest or health tration or tration or tration or 

Constituent or characteristic samples code MRL MRL advisories value value value 

Trace elements, in micrograms per liter, unless otherwise dissolved 

(sample filtered through 0.45-micrometer filter)--Continued 

Selenium 22/29 01145 0.7 0.3 50 (MCL) E0.2 0.9 92.5 

Silver 0/25 01075 5 1 100 (HAL/ -- -- -­

SMCL) 

Strontium 29/29 01080 -- -- 17,000 (HAL) 24.9 414 6,450 

Thallium 6/29 01057 5 .04 2 (MCL) E.03 1.04 .72 

Vanadium 14/29 01085 5 .2 -- <.2 1.5 12.2 

Zinc 25/29 01090 7 1 2,000 (HAL) <1 15 153 

5,000 SMCL) 

Nutrients, in milligrams per liter, dissolved (sample filtered through 0.45-micrometer filter), 

and dissolved organic carbon 

Nitrite, as N 8/29 00613 .01 .006 1 (MCL) E.003 .0043 .396 

Nitrite + nitrate, as nitrogen 17/29 00631 .05 .047 10 (MCL) E.036 .083 17.7 

Ammonia, as nitrogen 25/29 00608 .041 .02 30 (HAL) <.02 .49 4.31 

Ammonia + organic nitrogen, as 28/29 00623 .1 .1 -- <.1 .58 3.7 

nitrogen 

Phosphorus, as phosphorus 24/29 00666 .006 .006 -- E.003 .01 .113 

Orthophosphate, as phosphorus 20/29 00671 .018 .01 -- <.01 .015 .102 

Dissolved organic carbon (mg/L as 29/29 00681 -- -- -- E.32 1.6 8.2 

C) 

Radionuclides, in picocuries per liter unless otherwise noted, dissolved 

(sample filtered through 0.45-micrometer filter) 

Gross-alpha activity 15/26 04126 <3 <3 215 (MCL) <3 4.61 40.5 

Gross-beta activity 15/28 03515 <4 <4 -- <4 4.64 36.5 

Radium-224 28/28 50833 -- -- -- 3

-.01 4.21 4.3 

Radium-226 28/28 09503 -- -- 55 (MCL) .01 .22 1.15 

Radium-228 29/29 81366 -- -- 55 (MCL) .26 .83 1.36 

Radon-222 (unfiltered) 29/29 82303 -- -- 300 (PMCL) 246 658 4,420 

4,000 (AMCL) 

Tritium (unfiltered) 24/28 07000 <1 <1 -- .3 20.5 69.1 

Uranium (μg/L) 20/29 22704 <1 <1 30 (MCL) .03 1.77 28.9 

1

Median value was less than highest minimum reporting level and was estimated using log-probability regression (Helsel and Cohn, 1988).
 2Not including radon or uranium.
 3

Negative values indicates measurement was less than background radiation level at time of analysis.
 4

Negative values not included in summary statistics calculations.
 5Maximum contaminant level (MCL) is for the sum of radium-226 and radium-228.

Ground-Water Quality 45 

(25)	 (29) (25) (29) 

p = 0.2655 p < 0.0001 

SMCL 

W

SMCL ATER TEMPERATURE, FIELD MEASUREMENT, IN DEGREES CELSIUS pH, FIELD MEASUREMENT, IN STANDARD UNITS 

6 

8 

10 

12 

14 

16 

18 

6 

7 

8 

9 

10 

(25)	 (29) (25)	 (26) 

p = 0.0921 p = 0.0079

SMCL 

DISSOLVED OXYGEN, FIELD MEASUREMENT,

IN MILLIGRAMS PER LITER

TURBIDITY, FIELD MEASUREMENT, IN

NEPHELOMETRIC TURBIDITY UNITS (NTU) 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

0.001 

0.004 

0.01 

0.04 

0.1 

0.4 

1 

4 

10 

40 

100 

400 

1,000 

QUATERNARY LOWER QUATERNARY LOWER 

AQUIFERS	 TERTIARY AQUIFERS TERTIARY 

AQUIFERS AQUIFERS 

EXPLANATION 

(25)	 Number of ground-water samples 

Data values outside the 10th and 90th percentiles 

Percentile--Percentage of analyses equal to or less than the indicated value 

90th percentile 

75th percentile 

Median (50th percentile) 

25th percentile 

10th percentile 

SMCL Secondary Maximum Contaminant Level (U.S. Environmental

 Protection Agency, 2002) 

p = 0.0079 The two-sided probability (p-value) from the rank-sum statistical test.

 Probabilities (p-values) less than 0.05 are assumed to be statistically

 significant 

Figure 9. Physical characteristics of ground-water samples collected from Quaternary and lower Tertiary aquifers, Bighorn 

Basin, Wyoming and Montana, 1999-2001. 
46 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

(25) (29) (25) (29) 

800
 2,000 

500


200


1,000


500


p = 0.0001 p = 0.0003 

BICARBONATE, DISSOLVED, CALCULATED

FROM ALKALINITY (FIELD MEASUREMENT),

IN MILLIGRAMS PER LITER SODIUM, DISSOLVED, CALCIUM, DISSOLVED,

AS CALCIUM CARBONATE (CaCO ) IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER 3 

CHLORIDE, DISSOLVED, PO

TASSIUM, DISSOLVED, MAGNESIUM, DISSOLVED,


IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER IN MILLIGRAMS PER LITER


100


50


20


10


5


2


1


0.5 

200


100


50


20


10


5


2


1


0.5 

0.2 0.2 

0.1 0.1 

(25) (29) (25) (29) 

6,000 16


2,000 

p = 0.006 

14


p = 0.1873 

1,000 

12


500


200


100


10


8


50


6
 20


10
 4


5


2


2


1
 0 

(25) (29) (25) (29) 

1,800 450


p = 0.6931 

SMCL 

p = 0.3579 

1,600 400


1,400 

1,200 

1,000 

800


600


400


350


300


250


200


150


100


200
 50


0 0 

QUATERNARY LOWER TERTIARY QUATERNARY LOWER TERTIARY 

AQUIFERS AQUIFERS AQUIFERS AQUIFERS 

Figure 10. Major-ion concentrations and related water-quality characteristics of ground-water samples collected from Quaternary 

and lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2001. 
Ground-Water Quality 47 

(25) (29)	 (25) (29) 

20,000 8 

10,000 

7 

p = 0.8081 

SMCL 

1 

MCL 

p = 0.0001 

SMCL 

ALKALINITY, FIELD MEASUREMENT,

IN MILLIGRAMS PER LITER AS SULFATE, DISSOLVED, IN MILLIGRAMS

PER LITER

FLUORIDE, DISSOLVED, IN MILLIGRAMS


PER LITER


6 

5 

4 

3 

2 

1 

4,000 

1,000 

400 

100 

40 

10 

4 

1 

0.4 

0.1 0

(25) (29)	 (25) (29)

50 40,000

p < 0.0001 

SMCL 

p = 0.4001 

CALCIUM CARBONATE (CaCO )3 SILICA, DISSOLVED, IN MILLIGRAMS

40 

30 

HARDNESS, IN MILLIGRAMS PER LITER DISSOLVED SOLIDS, MEASURED,

3 IN MICROGRAMS PER LITER AS CALCIUM CARBONATE (CaCO ) 20,000 

10,000 

5,000 

2,000 

1,000 

500 

200 

PER LITER20 

15 

10 

8 

6


5
 100 

(25) (29)	 (25) (29) 

1,600 10,000 

p = 0.6811 

Very hard 

Soft 

Hard 

Moderately hard 

5,000 p = 0.0002

2,000 

1,000 

500 

200 

100 

50 

20 

10 

5 

2 

1,400 

1,200 

1,000 

800 

600 

400 

200 

0 1 

QUATERNARY LOWER TERTIARY QUATERNARY LOWER TERTIARY 

AQUIFERS AQUIFERS AQUIFERS AQUIFERS 

EXPLANATION 

(29)	 Number of ground-water samples 1 

Highest minimum reporting level and p = 0.0001 The two-sided probability (p-value) Data values outside the 10th and 90th percentiles number of censored samples from the rank-sum statistical test.

90th percentile SMCL Probabilities (p-values) less than

75th percentile	 Secondary Maximum Contaminant 0.05 are assumed to be

 Level (U.S. Environmental Protection statistically significant. 

Median (50th percentile)	 Agency, 2002) 

25th percentile MCL


10th percentile Maximum contaminant level


 (U.S. Environmental Protection

 Agency, 2002) 

Figure 10.—Continued 
48 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

sulfate in ground water is the oxidation of pyrite or other sulfides common in igneous and sedimentary rocks or the dissolution of evaporite deposits such as gypsum (calcium sulfate) 

(Hem, 1985). The MCL for fluoride (4 mg/L) was exceeded in 

only one sample from Quaternary aquifers and two samples 

from lower Tertiary aquifers; however, the SMCL for fluoride 

(2 mg/L) was exceeded more frequently (samples from 2 wells 

in the Quaternary aquifers and samples from 10 wells in the 

lower Tertiary aquifers). Frequent detection of fluoride at concentrations greater than the SMCL in lower Tertiary aquifers 

was expected; fluoride concentrations greater than the SMCL in 

ground water from lower Tertiary aquifers in the Bighorn Basin 

in Wyoming have been reported by previous investigators 

(Lowry and Lines, 1972; Lowry and others, 1993; Plafcan and 

others, 1993; Susong and others, 1993) and in similar or equivalent aquifers in Wyoming (Larson, 1984; Mora and others, 

1988). Fluoride in ground water is usually from dissolution of 

minerals such as fluorite, fluoroapatite, amphiboles, micas, and 

feldspars in sedimentary rocks (Hem, 1985). 

 The dissolved-solids concentration is a measure of the 

total amount of material dissolved in water. The total concentration of dissolved solids is reported as measured residue on 

evaporation at 180 degrees Celsius and as a calculated sum in 

appendixes 5-1 and 5-2. The dissolved-solids concentration 

measured from residue on evaporation is used in tables and figures in the text, and the concentration calculated from major 

ions is presented only in the appendixes. Differences between 

the two values may be from high concentrations of dissolved 

organic compounds not included in the calculated dissolvedsolids concentration that only included inorganic constituents. 

Dissolved-solids concentrations in samples from both 

aquifers generally were large—18 of 25 samples from Quaternary aquifers and 27 of 29 samples from lower Tertiary aquifers 

were larger than the SMCL of 500 mg/L (appendixes 5-1 and 5­

2). Median dissolved-solids concentrations in lower Tertiary 

aquifers generally were higher in young waters than in old 

waters, but were not significantly different. Concentrations of 

dissolved solids larger than the SMCL are common in waters 

from both aquifers in the Bighorn Basin in Wyoming (Lowry 

and others, 1993; Plafcan and others, 1993; Susong and others, 

1993) and in other similar aquifers in Wyoming (Larson, 1984; 

Mora and others, 1986). 

Dissolved-solids concentrations were compared to the 

USGS salinity classification (Heath, 1983, p. 65, table 2). Samples from many wells in both aquifers were not classified as 

fresh (table 13). Rural residents in the Bighorn Basin commonly use waters with large dissolved-solids concentrations for 

domestic purposes. Because of the prevalence of high mineralization, many of these residents use some form of treatment to 

improve the quality of water provided by private domestic 

wells. In addition, some residents in the Bighorn Basin purchase drinking water or obtain drinking water from another 

source instead of using their well water; these residents often 

will use the water obtained from their wells for domestic purposes other than drinking. 

Hardness is calculated from calcium and magnesium concentrations in water and is a qualitative indicator of how readily 

water forms insoluble residues with soaps and scale deposits in 

pipes and boilers and on plumbing fixtures. Hardness is typically expressed in mg/L as calcium carbonate (CaCO3) (Hem, 

1985). Hardness values calculated for samples from the Quaternary aquifers (table 11; fig. 10) were generally higher than 

those calculated for samples from lower Tertiary aquifers (table 

12; fig. 10), and median concentrations were significantly different (rank-sum test, p-value=0.0002). Hardness values for 

both types of aquifers were summarized using boxplots and 

compared to the hardness scale of Durfor and Becker (1964) 

(fig. 10). Based on the four hardness classes in this scale, 

almost all water from Quaternary aquifers was very hard 

(greater than 180 mg/L). In contrast, hardness varied considerably in water from lower Tertiary aquifers and ranged from soft 

(less than 60 mg/L) to very hard (greater than 180 mg/L). 

Although both calcium and magnesium contribute to hardness, 

magnesium concentrations in samples from both aquifers generally were much smaller than calcium concentrations. 

Trilinear diagrams were used to classify waters from both 

aquifers based on ionic composition. The cations calcium and 

sodium and the anions sulfate and bicarbonate were the dominant ions in both aquifers, although the relative proportions varied considerably in both types of aquifers. 

Table 13. Dissolved-solids concentrations in waters from Quaternary and lower Tertiary aquifers compared to U.S. Geological 

Survey salinity classification 

Number of samples from Number of samples from 

Dissolved-solids range, in U.S. Geological Survey Quaternary aquifers in lower Tertiary aquifers in 

milligrams per liter salinity classification range range 

0-1,000 Fresh 13 12 

1,000-3,000 Slightly saline 9 13 

3,000-10,000 Moderately saline 2 4 

10,000-35,000 Very saline 1 0 

More than 35,000 Briny 0 0 
Ground-Water Quality 49 

The predominant anion in Quaternary aquifers changes 

from bicarbonate to sulfate with increasing dissolved-solids 

concentrations. Ground water from Quaternary aquifers with 

fresh waters (dissolved-solids concentrations less than 

1,000 mg/L) generally were calcium-bicarbonate, calciumsodium-bicarbonate, and calcium-sodium-sulfate-bicarbonate 

type waters, whereas water with larger dissolved-solids concentrations generally was calcium-sodium-sulfate, calcium-sulfate, 

or sodium-sulfate type waters (fig. 11). 

The areal distribution of water composition and dissolved 

solids is shown with Stiff diagrams (Stiff, 1951) (fig. 12). The 

anion bicarbonate was predominant in samples from wells in 

the western part of the study area (fig. 12; wells 1, 2, 3, 4, 5, 9, 

and 11), whereas sulfate was predominant in the south (wells 12 

and 22) and the east (wells 17, 24, 27, 28, 29, and 30). 

Ground water from the lower Tertiary aquifers with fresh 

waters (dissolved-solids concentrations less than 1,000 mg/L) 

generally were sodium-bicarbonate or sodium-bicarbonatesulfate type waters, whereas waters with larger concentrations 

were sodium-sulfate or calcium-sodium-sulfate types (fig. 13). 

Water from two wells had very different ionic composition than 

water from most other wells; water from well 3 was a calciumbicarbonate type and water from well 22 was a calcium-sulfate 

type. The same relation between dissolved solids and anionic 

composition in waters from Quaternary aquifers was observed 

in waters from lower Tertiary aquifers—sulfate was the predominant anion in waters with dissolved-solids concentrations 

larger than 1,000 mg/L and bicarbonate was predominant in 

waters with smaller concentrations. Most waters with low 

dissolved-solids concentrations and sodium and bicarbonate as 

the predominant ions were old waters with low DO concentrations. The areal distribution of water type and dissolved-solids 

concentrations are shown with Stiff diagrams and no clear spatial pattern in either was observed (fig. 14). 

Waters from lower Tertiary aquifers classified as sodiumbicarbonate type likely evolved to this ionic composition 

through cation exchange and bacterially mediated sulfate reduction, although other processes are likely to have had some 

effect. Cation exchange is a reaction in which calcium and 

magnesium in water are exchanged for sodium adsorbed to 

aquifer sediments such as clay minerals, resulting in higher 

sodium concentrations and softer water (decreased calcium and 

magnesium concentrations). Calcium, magnesium, and hardness significantly decreased (p-values less than 0.05; Kendall’s 

tau=-0.39, -0.43, and -0.42, respectively) with increasing depth 

to the first open well interval. Waters from greater depths are 

likely to have had longer flow paths and therefore, more contact 

with aquifer materials (longer residence time), and more time to 

exchange calcium and magnesium for sodium. Deeper waters 

are more likely to be anoxic, increasing the likelihood of reducing conditions favorable to sulfate reduction. Sulfate reduction 

is a process where bacteria obtain energy for metabolism from 

oxidation of relatively simple organic compounds. That oxidation is coupled to sulfate reduction. This process generally 

occurs only when no free oxygen is available (anoxic or reducing conditions). Both geochemical processes occur in the same 

or equivalent aquifers in other structural basins in Wyoming 

and Montana and often affect ground-water chemistry (Renick, 

1924; Riffenburg, 1925; Dockins and others, 1980; Lee, 1981; 

Slagle and others, 1985; Martin and others, 1988; Chafin and 

Kimball, 1992). Because geologic, hydrogeologic, and waterquality characteristics of these aquifers in other structural 

basins are very similar to lower Tertiary aquifers in the Bighorn 

Basin, it is likely that the same geochemical processes control 

the water chemistry of lower Tertiary aquifers in the Bighorn 

Basin. 

Trace Elements 

Trace elements are a diverse group of constituents that 

generally occur naturally at small concentrations (less than 

1 mg/L) in ground water. Some trace elements (for example, 

barium, iron, and manganese) can be present at concentrations 

greater than the other trace elements, and are sometimes 

included in discussions of the major ions. Trace elements often 

are collectively referred to as metals even though some trace 

elements such as antimony, arsenic, and selenium are semimetallic elements. Geochemical conditions often control measured concentrations of trace elements in ground water rather 

than the element’s abundance in the rocks and minerals comprising the aquifer (Hem, 1985). Health-based regulatory standards (MCLs) have been established by the USEPA for many 

trace elements because of toxicity to the human body. In addition, some trace elements such as iron and manganese can stain 

plumbing and laundry, so the USEPA has established secondary 

standards (SMCLs) for some trace elements for these and other 

aesthetic reasons. 

Samples collected from 22 of 25 wells in Quaternary aquifers were analyzed for 18 trace elements (appendix 6-1). Samples collected from the remaining three wells and from all 

29 wells in lower Tertiary aquifers were analyzed for 23 trace 

elements (appendixes 6-1 and 6-2). 

The reader should note that the opened or screened intervals in several wells completed in the lower Tertiary aquifers 

were constructed of steel or unknown materials (table 3). Wells 

constructed of steel and other metals can affect concentrations 

of some trace elements (Lapham and others, 1997). The potential effect of well construction on trace elements measured in 

water samples collected from these wells was not evaluated, and 

the reader should note that analytical results from these wells 

were included in statistical calculations for descriptive purposes. 

Trace elements analyzed in ground water from both Quaternary and lower Tertiary aquifers are summarized and compared to USEPA standards in tables 11 and 12 and in boxplots 

(fig. 15). Reporting limits varied, so boxplots were constructed 

without censoring and are shown with both the lowest and highest laboratory reporting levels; the boxplot was truncated at the 

lowest reporting level. Six trace elements analyzed for, but not 

detected or detected infrequently in one of both aquifers, are 

listed in tables 11 and 12 but are not shown in boxplots. 
50 

100 

100 

Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

80 

100 

60 

20 

0 

Bicarbonate (HCO ) + Carbonate (CO ) 

3 

3 

Sulfate (SO ) 4 

20 

0 

40 

60 

80 

100 100

80 

60 

20 

0 

Sodium (Na) + Potassium (K) 

100 

80

60 

40 

20 

0 

20

0 

40 

60 

80 

100 

20 

0 

40 

60 

80 

Magnesium (Mg) 

20 

0 0

40 

60 

80 

100 

40 

20 

40 

60 

80 

100 

40 

Calcium (Ca) + Magnesium (Mg)

20 

0 

0

40 

60 

80 

Sulfate (SO ) + Chloride (Cl) 

4 

20 

40 

60 

80 

1 

2 

11 5 

4 

9 

3 

6 

7 

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19 16 

25 

28 

27 24

12 29 

13 

17 

22 

30 

10 

18 

14 

Calcium (Ca) Chloride (Cl), Fluoride (F), and 

CATIONS Nitrite+Nitrate (NO2+NO3) 

ANIONS 

PERCENTAGE OF TOTAL MILLIEQUIVALENTS PER LITER 

EXPLANATION 

1 Subunit survey (SUS1) well number 

Dissolved-solids concentration, 

in milligrams per liter 

Less than 500 

500 to 999 

1,000 to 1,999 

2,000 and greater 

Figure 11. Trilinear diagram showing major-ion composition and dissolved-solids concentrations for ground-water samples collected from Quaternary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2000. 
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Figure 12. Stiff diagrams showing areal distribution of major-ion composition and dissolved-solids concentrations for ground-water samples collected from Quaternary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2000.
52 

100 

100 

Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Bicarbonate (HCO ) + Carbonate (CO ) 

3 

3 

Sulfate (SO ) 4 

Sodium (Na) + Potassium (K)

Magnesium (Mg) 

Calcium (Ca) + Magnesium (Mg)

Sulfate (SO ) + Chloride (Cl) 

4 

1 

30 

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14 

16 

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3 

7 

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19 

4 

25 

23 

28 

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27 

2 

29 

13 

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17 15 

26 

20 

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10 

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20 

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100 

60 

20 

0 

20 

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40 

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100 100

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100 

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40 

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40 

60 

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0 0

40 

80 

100 

40 

20 

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60 

80 

100 

40 

20 

0 

0

40 

60 

80 

20 

40 

60 

80 

100 

Calcium (Ca) Chloride (Cl), Fluoride (F), and 

CATIONS Nitrite+Nitrate (NO2+NO3) 

ANIONS 

PERCENTAGE OF TOTAL MILLIEQUIVALENTS PER LITER 

EXPLANATION 

1 Subunit survey (SUS2) well number 

Dissolved-solids concentration, 

in milligrams per liter 

Less than 500 

500 to 999 

1,000 to 1,999 

2,000 and greater 

Figure 13. Trilinear diagram showing major-ion composition and dissolved-solids concentrations for ground-water 

samples collected from lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 2000-2001. 
Ground-Water Quality 53

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Figure 14. Stiff diagrams showing areal distribution of major-ion composition and dissolved-solids concentrations for ground-water samples collected from lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 2000-2001.
54 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

(25) (29) (25) (29) 

30
 8


20


BROMIDE, DISSOLVED, IN MILLIGRAMS BARIUM, DISSOLVED, IN MICROGRAMS ALUMINUM, DISSOLVED, IN MICROGRAMS

PER LITER PER LITER PER LITER

MCL 

15 

9 

8 13

CHROMIUM, DISSOLVED, IN MICROGRAMS BORON, DISSOLVED, IN MICROGRAMS ARSENIC, DISSOLVED, IN MICROGRAMS


PER LITER PER LITER PER LITER


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1 

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p = 0.3650 

10


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0.2 

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8 19 

21 

0 

QUATERNARY LOWER TERTIARY QUATERNARY LOWER TERTIARY 

AQUIFERS AQUIFERS AQUIFERS AQUIFERS 

Figure 15. Trace-element concentrations in ground-water samples collected from Quaternary and lower Tertiary aquifers, 

Bighorn Basin, Wyoming and Montana, 1999-2001. 
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Ground-Water Quality 55

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Figure 15. Continued.
56 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Concentrations of most trace elements in both aquifers 

generally were small, and many were smaller than selected 

USEPA standards (tables 11 and 12; fig. 15). Six trace elements 

(antimony, beryllium, cadmium, lead, silver, and thallium) 

were not detected in any samples from Quaternary aquifers, one 

of which (silver), also was not detected in any samples from 

lower Tertiary aquifers. Concentrations of most trace elements 

in both types of aquifers varied considerably and median concentrations of most were significantly different between aquifers (fig. 15). Iron and manganese were the only trace elements 

measured in some samples from Quaternary aquifers at concentrations larger than USEPA standards (SMCLs). High iron concentrations in ground water can result in staining of laundry and 

plumbing fixtures with red oxyhydroxide precipitates; similarly, high manganese concentrations can discolor water, affect 

the taste of water, and stain laundry and plumbing fixtures with 

black manganese oxides (Hem, 1985). Six trace elements 

(boron, cadmium, iron, manganese, molybdenum, and selenium) were measured in some samples from lower Tertiary 

aquifers at concentrations larger than applicable USEPA standards or draft standards (table 12, fig. 15). In most cases, the 

USEPA standards for these trace elements were exceeded in 

only one or two samples from lower Tertiary aquifers (fig. 15). 

However, iron and manganese were exceptions to this generalization, and both were measured in samples from both types of 

aquifers at concentrations that frequently exceeded USEPA 

standards—at least 10 percent of the samples collected from 

each aquifer exceeded the respective SMCLs. In fact, the 

SMCL for manganese was the most frequently exceeded standard, and 17 of 25 (68 percent) samples from Quaternary aquifers and 9 of 29 (31 percent) samples from lower Tertiary aquifers exceeded the standard. 

Concentrations of iron and manganese dissolved in ground 

water (solubility) often are related to the redox potential and pH 

of ground water, although manganese less so than iron (Hem, 

1985). Both trace elements are more soluble in reducing 

(anoxic) conditions. Iron concentrations in waters from Quaternary and lower Tertiary aquifers were not significantly correlated with measured pH or DO concentrations. In contrast, 

manganese concentrations in Quaternary aquifers were negatively correlated with DO concentrations (p-value=0.0221 and 

Spearman’s rho=-0.4667), and concentrations in lower Tertiary 

aquifers were negatively correlated with measured pH 

(p-value=0.0036 and Spearman’s rho=-0.5503). Therefore, 

manganese concentrations may be controlled by DO in Quaternary aquifers and by pH in lower Tertiary aquifers. 

Nutrients and Dissolved Organic Carbon 

Ground-water samples from both types of aquifers were 

analyzed for different species of nitrogen and phosphorus. 

Small concentrations of both nutrients occur naturally in ground 

water, but elevated concentrations commonly are associated 

with human activities. The most common human sources of 

nitrogen and phosphorus in shallow ground water are from 

leaching of fertilizers from agricultural lands, animal manure, 

or septic system effluent. 

Nitrate (an oxidized species of nitrogen in water) and 

phosphorus in water are of environmental and health concern. 

Nitrate and phosphorus discharged to surface waters can contribute to eutrophication. Large concentrations of nitrate in 

drinking water have been associated with several potential 

adverse health effects including low levels of oxygen in the 

blood of infants (“blue baby” syndrome, also known as methemoglobinemia) (Fan and Steinberg, 1996), miscarriage (Centers for Disease Control and Prevention, 1996), and increased 

risk of non-Hodgkins lymphoma (Ward and others, 1996). 

As noted by Hem (1985, p. 124), “nitrogen occurs in water 

as nitrite or nitrate anions, in cationic form as ammonium, and 

at intermediate oxidation states as a part of organic solutes.” 

Consequently, ground-water samples were analyzed for several 

species of nitrogen, including both oxidized and reduced forms. 

Biogeochemical processes often control the species of nitrogen 

measured in ground water (Hem, 1985). The reader should note 

that all nitrogen species concentrations discussed in this report 

are reported as equivalent concentrations of nitrogen. Groundwater samples were analyzed for total ammonia as nitrogen 

(referred to as “ammonia” in this report) that included ammonium ion and un-ionized ammonia. At the pHs measured in 

ground-water samples collected from both types of aquifers, unionized ammonia was likely a small component of total ammonia (Hem, 1985). 

Nutrient concentrations in Quaternary and lower Tertiary 

aquifers are summarized in tables 11 and 12. Boxplots (fig. 16) 

were constructed to show the differences in nutrient concentrations between aquifers; the results of statistical comparisons 

using the Wilcoxon rank-sum test also are presented on the boxplots. Results of individual analyses are presented in appendixes 7-1 and 7-2. 

Nitrite as nitrogen (nitrite) was detected infrequently and 

at very small concentrations in both types of aquifers (tables 11 

and 12; fig. 16). All nitrite concentrations in both aquifers were 

much smaller than the MCL of 1 mg/L. Nitrite does not commonly occur at large concentrations in ground water because it 

is generally an unstable intermediate product of nitrification 

that oxidizes rapidly in most oxic waters (Hem, 1985). 

Nitrate is the most common form of nitrogen in oxic 

ground water and is stable over a wide range of geochemical 

conditions (Hem, 1985). Nitrate typically is reported as the sum 

of nitrite plus nitrate as nitrogen. Because nitrite was detected 

infrequently at very small concentrations and composed very 

little of the nitrite plus nitrate concentrations (fig. 16), nitrite 

plus nitrate as nitrogen are referred to as “nitrate” in this report. 

Nitrate was detected at about the same frequency in both types 

of aquifers, although generally at higher concentrations in samples from Quaternary aquifers than in samples from lower Tertiary aquifers (tables 11 and 12); however, median concentrations were not significantly different (p-value greater than 0.05) 

(fig. 16). Nitrate concentrations in 2 of 25 samples from Quaternary aquifers and 1 of 29 samples from lower Tertiary aquifers were larger than the MCL of 10 mg/L. In general, nitrate 
concentrations are small in uncontaminated ground water. Concentrations of nitrate in ground water greater than 3 mg/L (Madison and Brunett, 1985), 2 mg/L (Mueller and Helsel, 1996), or 

about 1 mg/L (Nolan and Hitt, 2003) have been suggested to be 

the result of human activities. Compared to the lowest estimate 

(1 mg/L), 9 of 25 samples from the Quaternary aquifers and 8 

of 29 samples from lower Tertiary aquifers had nitrate concentrations in the range of what would be expected when influenced by human activities. 

Ammonia as nitrogen (ammonia) was detected less frequently in samples from Quaternary aquifers than in samples 

from lower Tertiary aquifers, and median concentrations were 

significantly different (p-value less than 0.0001) (tables 11 and 

12, fig. 16). Ammonia plus organic nitrogen as nitrogen was 

detected in most wells in both aquifers, and median concentrations were significantly different (p-value=0.0012). Concentrations of ammonia plus organic nitrogen tend to be small in 

ground water because they tend to adsorb to organic matter and 

clay particles (Hem, 1985). A comparison of the ranges of concentrations for ammonia with ammonia plus organic nitrogen 

(appendixes 7-1 and 7-2; fig. 16) indicates that organic nitrogen 

was present in Quaternary aquifers and composed most of the 

ammonia plus organic nitrogen. In contrast, little organic nitrogen was likely present in the lower Tertiary aquifers based on 

the similarity in ranges of concentrations for ammonia and 

ammonia plus organic nitrogen (fig. 16). The redox state of the 

ground water may control ammonia concentrations in the lower 

Tertiary aquifers, as indicated by a weak negative correlation 

between DO concentrations and ammonia concentrations (pvalue=0.0594, Spearman’s rho=-0.3767). 

Phosphorus (total) and orthophosphate (as phosphorus) 

concentrations generally were small in both types of aquifers 

(tables 11 and 12; fig. 16). Median phosphorus and orthophosphate concentrations were not significantly different between 

aquifers. Orthophosphate typically constitutes the majority of 

total phosphorus and is the form most readily used by algae and 

aquatic plants. Phosphorus concentrations in both aquifers 

were very similar to orthophosphate concentrations, indicating 

that orthophosphate likely was the primary form of phosphorus 

in waters from both aquifers. Phosphorus concentrations in 

ground water usually are small because of low solubility and 

tendency to adsorb to organic matter or metallic oxides in the 

subsurface (Hem, 1985). 

Dissolved organic carbon (DOC) occurs naturally in 

ground water, but elevated concentrations can indicate contamination from human sources. Most natural DOC in ground 

water is from humic and fulvic acids generated by biogeochemical degradation of organic material in the soil profile above the 

aquifer or by degradation of organic matter in the deposits. Percolating waters (ground-water recharge) transport DOC in the 

soil zone to the water table. DOC concentrations in ground 

water can affect trace element solubility (through formation of 

complexes) and the redox state of ground water (DOC is a common electron donor) (Hem, 1985). 

Concentrations of DOC ranged from 0.61 to 38 mg/L in 

samples from Quaternary aquifers and from 0.32 to 8.2 mg/L in 

Ground-Water Quality 57 

samples from lower Tertiary aquifers (fig. 16). Median DOC 

concentrations in Quaternary aquifers (3.1 mg/L) and lower 

Tertiary aquifers (1.6 mg/L) were higher than the median DOC 

concentration (0.7 mg/L) reported for wells with potable waters 

throughout the United States (Leenheer and others, 1974) and 

the average DOC concentration (0.5 mg/L) in ground water 

reported by Thurman (1985). Leenheer and others (1974) also 

noted that most ground waters not affected by contamination 

have DOC concentrations less than 2 mg/L. Drever (1997, 

fig. 6-1, p. 108) reported a typical range of 0 to about 3 mg/L of 

DOC for natural ground waters. Nielson (1991, p. 545) 

reported a typical range of 0 to 10 mg/L of total organic carbon 

in ground water, but this reported range includes both suspended and dissolved organic carbon. The overall higher 

median concentration in samples from Quaternary aquifers 

compared to natural ground water may be attributable to the 

influence of surface water—many of the wells are completed in 

aquifers that are recharged through infiltration of diverted surface water used for irrigation, and some wells are completed in 

aquifers that are in direct hydraulic connection with surface 

water at least some time during the year. Surface waters generally have higher DOC concentrations than ground waters, typically in the range of 1 to 11 mg/L (Drever, 1997, fig. 6-1, 

p. 108). Some DOC concentrations were relatively high in 

lower Tertiary aquifers. Coal and organic shales are present in 

the Willwood and Fort Union Formations composing the lower 

Tertiary aquifers. Ground water associated with these types of 

sedimentary deposits may have naturally elevated DOC concentrations (Drever, 1997). 

Very large DOC concentrations were measured in samples 

from two wells completed in the Quaternary aquifers. An 

anomalously large DOC concentration (38 mg/L) was measured 

in well SUS1-10 (fig. 16), a monitoring well completed in the 

Quaternary alluvium along the Greybull River. Water sampled 

from this well had a very distinctive yellowish color, a common 

characteristic of waters with high humic or fulvic acid content. 

Septic-system effluent can contain very large DOC concentrations, but there were no septic systems located in the vicinity of 

the well that were likely upgradient from the well. Well 

SUS1-10 was located very close to the Greybull River in a 

marshy/wetland riparian area likely in hydraulic connection 

with the river. The concentration of DOC from this well is 

within the range reported for swamps and wetlands (Thurman, 

1985) and marshes and bogs (Drever, 1997, fig. 6-1, p. 108). 

Drever (1997) also noted that ground water associated with 

swamps might have elevated DOC concentrations. Well 

SUS1-13 (fig. 16) also had a very large DOC concentration 

(27 mg/L). There were no obvious sources of contamination 

near this well, and the source of the elevated DOC concentration is unknown. This well, like well SUS1-10, was completed 

in alluvium in hydraulic connection with surface water (Gooseberry Creek), but it is unknown if the water in the creek was the 

source of the high DOC concentration. 

Concentrations of the various nitrogen species in both 

aquifers were examined statistically in relation to measured DO 

and DOC concentrations. As noted earlier, the redox state of 
58 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

(25) (29) (25) (29) 

1 50 

0.5 

0.2 

0.1 

0.05 

0.02 

0.01 

0.005 

0.002 

0.001 

0.0005 

0.0002 

0.0001 

0.00005 

0.00002 

0.00001 

20 21 

AMMONIA PLUS ORGANIC NITROGEN,

DISSOLVED, IN MILLIGRAMS PER LITER NITRITE PLUS NITRATE, DISSOLVED, IN MILLIGRAMS PER LITER AS NITROGEN AS NITROGEN 

20 

10 

5 

2 

1 

0.5 

0.2 

0.1 

0.05 

0.02 

0.01 

0.005 

13 12 

MCL 

p = 0.9301 

AMMONIA, DISSOLVED, IN MILLIGRAMS NITRITE, DISSOLVED, IN MILLIGRAMS

PER LITER AS NITROGEN PER LITERAS NITROGEN 

(25) (29) (25) (29) 

12 

4 

p < 0.0001 

10 10

2 1 

5 p = 0.0012

5 

2 

1 

0.5 2 

0.2 

1 

0.1 

0.05 

0.5 

0.02 

0.01 

0.005 

0.002 

0.2 

0.1 

0.001 

0.0005 0.05 

QUATERNARY LOWER TERTIARY QUATERNARY LOWER TERTIARY 

AQUIFERS AQUIFERS AQUIFERS AQUIFERS 

Figure 16. Nutrient and dissolved organic carbon (DOC) concentrations in ground-water samples collected from Quaternary 

and lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2001. 
Ground-Water Quality 59 

(25) (29)	 (25) (29) 

0.12 0.12 ORTHOPHOSPHATE, DISSOLVED, IN MILLIGRAMS PER LITER AS PHOSPHORUS 

1 5 

p = 0.9298 

9 

9 

p = 0.5971 

PHOSPHORUS, DISSOLVED, DISSOLVED ORGANIC CARBON, IN IN MILLIGRAMS PER LITER MILLIGRAMS PER LITER AS CARBON (C) 

0.10 

EXPLANATION 

50 (29) Number of ground-water samples 

Data values outside the 10th and 90th percentiles 

0.10 

0.08 0.08 

0.06 0.06 

0.04 0.04 

0.02 0.02 

0.00 0.0 

QUATERNARY	 LOWER TERTIARY 

AQUIFERS AQUIFERS (25)	 (29) 

100 

p = 0.0004 

20 

10 

5 

2 1 

1 

MCL 

0.5 

0.2 p = 0.0004 

0.1 

QUATERNARY	 LOWER TERTIARY 

AQUIFERS AQUIFERS 

90th percentile 

75th percentile 

Median (50th percentile) 

25th percentile 

10th percentile 

Highest minimum reporting level and number of censored

 samples 

Maximum Contaminant Level (U.S. Environmental Protection

 Agency, 2002) 

The two-sided probability (p-value) from the rank-sum

 statistical test. Probabilities (p-values) less than 0.05 are

 assumed to be statistically significant. P-values were not

 calculated if greater than 50 percent of values were

 censored. 

Figure 16.--Continued 
60 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

ground water can be related to the amount of DO. The redox 

state and related microbial processes can determine the predominant or stable nitrogen species in ground water. The amount of 

DO in ground water can be affected by the amount of DOC. 

Bacterially mediated decomposition of DOC consumes DO 

(microbial respiration). If large amounts of DOC are available 

to be oxidized, DO concentrations in ground water tend to be 

small, and the ground water will tend to be anaerobic because the 

DO is consumed during respiration. In oxic or aerobic ground 

water, nitrate is the persistent nitrogen species and it is relatively 

mobile. In anoxic or anaerobic ground waters, reduced species 

such as nitrite or ammonium are the persistent nitrogen species, 

although nitrite typically is converted to ammonium or nitrogen 

gas in anaerobic water. Ammonium is soluble in ground water 

but is relatively immobile because it tends to adsorb to clay particles. A weak negative correlation (p-value=0.0749; Spearman’s rho=-0.3632) was noted between DO and DOC concentrations in samples from Quaternary aquifers, whereas no correlation was noted in lower Tertiary aquifers. 

For samples collected from Quaternary aquifers, DO concentrations were not correlated with any of the nitrogen species. 

DOC concentrations were positively correlated with ammonia 

plus organic nitrogen concentrations (p-value=0.0004; Spearmans’s rho=0.7181) and nitrite concentrations (p-value=0.0497; 

Spearman’s rho=0.4009). DOC concentrations were not correlated with ammonia and nitrate concentrations. Overall, the lack 

of correlation indicates that nitrogen speciation and concentrations in the Quaternary aquifers do not appear to be controlled by 

DO or DOC. 

Concentrations of various nitrogen species in ground-water 

samples from lower Tertiary aquifers were compared statistically to DO and DOC concentrations. For this comparison, various nitrogen species were grouped into “old” or “modern” 

ground-water age categories for comparison. Median concentrations of ammonia and ammonia plus organic nitrogen were significantly different between samples with old and modern waters 

(p-values of 0.0055 and 0.0342, respectively). Median nitrate 

concentrations between samples with old and modern waters 

were significantly different (p-value=0.0418), but no significant 

difference was noted in median nitrite concentrations. 

Because median concentrations of many nitrogen species 

were significantly different, nitrogen species were compared statistically with DO and DOC concentrations using the old and 

modern categories. DO concentrations in old waters were not 

correlated with any nitrogen species. In contrast, DO concentrations in modern waters were negatively correlated with 

ammonia (p-value=0.0135; Kendall’s tau=-0.5000) and weakly 

negatively correlated with ammonia plus organic nitrogen 

(p-value=0.0853; Kendall’s tau=-0.3590); DO concentrations 

were positively correlated with nitrate (p-value=0.0178; Kendall’s tau=0.4872). These correlations were expected because 

DO is an indicator of oxidizing conditions, which favor the 

occurrence of nitrate rather than ammonia. DOC concentrations 

in old waters were not correlated with nitrate or nitrite but were 

positively correlated with ammonia (p-value=0.0059; Kendall’s 

tau=0.5495) and ammonia plus organic nitrogen (p-value= 

0.0082; Kendall’s tau=0.5275). DOC concentrations in modern 

waters were not correlated with ammonia or ammonia plus 

organic nitrogen but were positively correlated with nitrate 

(p-value=0.0130; Kendall’s tau=0.4667). 

Nutrient and DOC concentrations in both types of aquifers 

were compared statistically to depth to the top of the open well 

intervals. Concentrations of some nutrients (primarily nitrate) in 

ground water will typically be large at the water table and 

decrease with depth and downgradient direction (Hallberg and 

Keeney, 1993, and references therein). Concentrations of many 

nutrients did not correlate with depth to the top of the open well 

intervals. However, ammonia concentrations in samples from 

lower Tertiary aquifers significantly increased with increasing 

depth to the first open well interval (p-value=0.0242; Spearman’s rho=0.4341). Nitrate concentrations in lower Tertiary 

aquifers were weakly negatively correlated with depth to the first 

open well interval (p-value=0.0752; Kendall’s tau=-0.3421). 

DOC concentrations in lower Tertiary aquifers were negatively 

correlated with depth to the first open well interval (p-value= 

0.0395; Kendall’s tau=-0.3960). 

The concentration and distribution of nutrient species were 

compared statistically with mapped land use in a 1,650-ft 

(500-m) radius surrounding wells to evaluate relations between 

nutrients and land use. Nitrite concentrations in both aquifers 

were not statistically compared with land use because of the 

large number of concentrations less than the MRL (greater than 

50 percent). Ammonia concentrations in samples from both 

types of aquifers were not correlated to the percentage of cropland, rangeland, riparian, or urban land within 500 m of the sampled wells. However, ammonia concentrations in samples from 

Quaternary aquifers were negatively correlated with the percentage of “other agricultural” land (p-value=0.0050, Spearman’s 

rho=-0.5715) and positively correlated with the percentage of 

“other” land mapped around wells (p-value=0.0354, Spearman’s 

rho=0.4298). Organic nitrogen plus ammonia concentrations 

were not correlated with any land use (all p-values greater than 

0.05). Nitrate concentrations in Quaternary aquifers were positively correlated with the percentage of cropland (p-value= 

0.0041; Spearman’s rho=0.5865) and other agricultural land 

(p-value=0.0448; Spearman’s rho=0.4099) and negatively correlated with rangeland (p-value=0.0140; Spearman’s 

rho=-0.5015) and riparian land (p-value=0.0479; Spearman’s 

rho=-0.4034). In samples from lower Tertiary aquifers, nitrate 

concentrations were positively correlated with the percentage of 

cropland (p-value=0.0219; Spearman’s rho=0.4334) and weakly 

negatively correlated with rangeland (p-value=0.0575; Spearman’s rho=-0.3587). The positive correlations between nitrate 

concentrations and cropland in both aquifers may be attributable 

to fertilizer use. Leaching of fertilizers from cropland can result 

in elevated nitrogen concentrations in shallow ground water 

(Alley, 1993). Correlation of nitrate with other agricultural land 

for the Quaternary aquifers could be due to animal waste in pastures or livestock holding areas, as well as effluent from rural 

domestic septic systems. The negative correlation between 

riparian land use and nitrate concentrations could be the result of 

nitrogen uptake by vegetation in the riparian zone. The negative 
correlation between nitrate and rangeland in both aquifers may 

be due to absence of nitrogen sources. Phosphorus and orthophosphate concentrations in Quaternary aquifers were not correlated with any land use. Orthophosphate concentrations in lower 

Tertiary aquifers were positively correlated to the percentage of 

riparian land (p-value =0.0320; Spearman’s rho=0.4056) and 

urban land (p-value=0.0248; Spearman’s rho=0.4245). Phosphorus was positively correlated to urban land use (p-value= 

0.0274; Spearmans’s rho=0.4171). Phosphorus, like nitrogen, is 

commonly found in animal and human waste and is a common 

component of fertilizers. The correlation between both phosphorus and orthophosphate and urban land may be attributable to 

fertilizer use or effluent from residential domestic septic systems. 

Radionuclides 

Radionuclides are chemical elements that undergo radioactive decay. In ground water, radionuclides are from natural 

sources such as rocks or minerals, or from human activities such 

as nuclear weapons testing, mining, or industrial/medical processes. The presence of radionuclides in ground water is controlled by many factors, including the distribution and concentration of radionuclides in rock comprising the aquifer, the 

chemical form of the radionuclides, geochemical conditions (pH 

and redox potential), presence of complexing and sorptive materials, microbial activity, and half-life (Hem, 1985). The half-life 

is particularly important because it determines the length of time 

the radionuclide can reside in ground water. 

This report presents the results of sampling for gross-alpha 

activity (alpha activity from all sources) as thorium-230 (

230Th); 

gross-beta activity (beta activity from all sources) as cesium-137 

(137Cs); radium isotopes radium-224 (224Ra), radium-226 

(

226Ra), and radium-228 (228Ra); radon-222 (222Rn); and total 

uranium (U). Concentrations of radionuclides typically are 

expressed in picocuries per liter (pCi/L), where one curie (Ci) is 

equal to 3.7 x 1010 atomic disintegrations per second, and 

1 pCi/L is equal to 2.2 disintegrations per minute per liter of 

water. The results of sampling are summarized in boxplots 

(fig. 17), and the individual results are presented with analytical 

(counting) uncertainties in appendixes 8-1 and 8-2. For descriptive purposes, boxplots were constructed and hypothesis tests 

were calculated using raw unrounded activities—the reader is 

referred to appendixes 8-1and 8-2 to interpret individual radionuclide activities in the context of the sample-specific analytical 

uncertainty and minimum detectable concentration (MDC). 

Gross-alpha activity is a measure of all alpha radiation 

(positively charged helium nuclei) emitted from a ground-water 

sample and originates from the decay of two uranium isotopes 

(uranium-238 and uranium-235) and thorium-232, which generally occur naturally. Gross-beta activity is a measure of all beta 

radiation (electrons or positrons) emitted from a ground-water 

sample and originates from potassium-40 and radium-228, 

which are naturally occurring; strontium-90 and cesium-137, 

which generally are from human activities; and tritium, which 

Ground-Water Quality 61 

occurs naturally and from human activities. The range of grossalpha and gross-beta activities in both aquifers is shown on boxplots in fig. 17. Gross-alpha and gross-beta activities generally 

were higher in Quaternary aquifers than in lower Tertiary aquifers, but median activities were not significantly different 

(p-values greater than 0.05). Gross-alpha activities in 9 of 

24 samples from the Quaternary aquifers and 6 of 26 samples 

from the lower Tertiary aquifers were larger than the USEPA 

MCL (15 pCi/L). NAWQA analyses of gross alpha and gross 

beta activity include the man-made radionuclides as well as natural radionuclides (such as isotopes of U, Th, and Ra). 

Ground-water samples were analyzed for three of the four 

natural radium isotopes (radium-224, radium-226, and 

radium-228). Radium-224 and radium-228 are naturally occurring products of the thorium-232 decay series, whereas radium226 is a naturally occurring product of the uranium-238 decay 

series. Activities of all three measured radium isotopes generally were small in samples from both aquifers and most activities 

were less than 1 pCi/L (fig. 17). The USEPA has established an 

MCL for total dissolved radium, which is defined as the sum of 

the activities of radium-226 and radium-228 (5 pCi/L), but no 

MCL has been established for radium-224. No summed radium226 and radium-228 activities from samples in either aquifer 

exceeded the MCL. 

Radon-222 (radon) is a naturally occurring radioactive gas 

that is the decay product of radium-226. The source of radon gas 

in ground water is naturally occurring uranium in rock and sediments. Ingestion of high concentrations of radon in drinking 

water can cause stomach cancer, but ingestion is not the primary 

health risk. The primary health risk is inhalation. Radon also 

can enter homes by the use of water from wells—radon can 

degas from water into household air during activities such as taking a shower. Radon is second only to cigarette smoking in causing lung cancer in the United States and is estimated to cause 

between 5,000 and 20,000 lung-cancer fatalities annually (Cothern and Smith, 1987). Because of health concerns, the USEPA 

has proposed two drinking-water standards (U.S. Environmental 

Protection Agency, 1999)—an MCL of 300 pCi/L and an alternative MCL (AMCL) of 4,000 pCi/L for communities with 

indoor air multimedia mitigation programs. Radon activities in 

samples from both Quaternary and lower Tertiary aquifers are 

summarized in boxplots (fig. 17). Activities in samples from 

both aquifers were relatively similar and median activities were 

not significantly different (p-value = 0.8351, fig. 17). Activities 

in all samples from Quaternary aquifers and in all but two samples from the lower Tertiary aquifers were greater than the proposed MCL of 300 pCi/L. No samples from the Quaternary 

aquifers had radon activities larger than the 4,000-pCi/L AMCL, 

but the activity in one sample from the lower Tertiary aquifers 

was larger. 

Naturally occurring uranium is composed of three isotopes 

(uranium-238, uranium-235, and uranium-234). Ground-water 

samples were analyzed for total uranium (uranium), which 

includes all three isotopes. In this report, and in contrast with 

reporting of other radionuclide measurements herein, uranium 

concentrations are reported in μg/L. 
62 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

(24) (26)	 (24) (28) 

200 80 

8 11 

p = 0.2944 

MCL1 

RADIUM-226, DISSOLVED, IN PICOCURIES GROSS-BETA ACTIVITY AS

PER LITER CESIUM-137, DISSOLVED, IN PICOCURIES

9 13 

p = 0.2953 

100 

50 

20 

10 

5 

2 

1 

0.5 

50 

20 

RADIUM-224, WATER, DISSOLVED, GROSS-ALPHA ACTIVITY AS

IN PICOCURIES PER LITER THORIUM-230, DISSOLVED, IN PICOCURIES PER LITER

PER LITER 10 

5 

2 

1 

(20) (26)	 (21) (28) 

20 

10 

5 

2 

1 

0.5 

0.2 

0.1 

0.05 

0.02 

2 

1 

0.5 

0.2 

0.1 

0.05 

0.02 

0.01 

0.005 

p = 0.2547 p = 0.0028

0.01 

QUATERNARY LOWER QUATERNARY LOWER 

AQUIFERS TERTIARY AQUIFERS TERTIARY 

AQUIFERS AQUIFERS 

EXPLANATION 

(29)	 Number of ground-water samples


Data values outside the 10th and 90th percentiles


90th percentile


75th percentile


Median (50th percentile)


25th percentile


10th percentile 

2 Highest minimum reporting level and number of censored samples


MCL
 Maximum Contaminant Level (U.S. Environmental Protection Agency, 2002) 

MCL1	 Maximum Contaminant Level excludes uranium and radon 

AMCL Proposed alternate Maximum Contaminant Level (U.S. Environmental Protection Agency, 1999)


PMCL


Proposed Maximum Contaminant Level (U.S. Environmental Protection Agency, 1999) 

p = 0.2944 The two-sided probability (p-value) from the rank-sum statistical test.


 Probabilities (p-values) less than 0.05 are assumed to be statistically significant


Figure 17. Radionuclide concentrations in ground-water samples collected from Quaternary and lower Tertiary aquifers, 

Bighorn Basin, Wyoming and Montana, 1999-2001. 
63 

2.2 

Ground-Water Quality 

(25)	 (29) (25) (29) 

6,000 

5,000 

2.0 

TRITIUM, TOTAL, IN PICOCURIES RADIUM-228, DISSOLVED, IN PICOCURIES PER LITER	 PER LITER 

p = 0.2743 

p = 0.8351 

AMCL 

PMCL 

URANIUM, NATURAL, DISSOLVED, RADON-222, TOTAL, IN PICOCURIES PER LITER IN MICROGRAMS PER LITER 

4,000 

3,000 

2,000 

1,500 

1,000 

800


600


500


400


300


200


150


1.8 

1.6 

1.4 

1.2 

1.0 

0.8 

0.6 

0.4 

0.2 

0.0 100


(25)	 (29) (25) (29) 

200
 500


4 

p < 0.0001 

MCL 

2 9 

p < 0.0001 100


50


20


10


5


2


1


0.5 

200


100


50


20


10


5


2


1


0.5 

0.2 

0.1 

0.05 

0.2 0.02 

0.1 0.01 QUATERNARY LOWER 

QUATERNARY LOWER 

AQUIFERS	 TERTIARY AQUIFERS TERTIARY 

AQUIFERS 

AQUIFERS 

Figure 17.—Continued 
64 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Uranium concentrations were larger in samples from Quaternary aquifers than in lower Tertiary aquifers, and median 

concentrations were significantly different (p-value <0.0001, 

fig. 17). The solubility of uranium in ground water is strongly 

affected by redox conditions (and pH), and uranium is more soluble in oxidizing conditions. DO concentrations in the lower 

Tertiary aquifers were positively correlated with uranium concentrations (p-value = 0.0044; Spearman’s rho=0.4697). Uranium concentrations in two samples from the Quaternary aquifers (appendix 8-1) exceeded the uranium MCL (30 μg/L). 

Pesticide Compounds 

Nineteen pesticide compounds were detected in 15 of 

25 well samples in the Quaternary aquifers (table 14; fig. 18; 

appendix 9-1). About sixty-five percent of the total 56 pesticide 

detections were herbicides, 32 percent were herbicide breakdown products, and 2 percent were insecticides. Nine of the 

nineteen pesticide compounds detected were not found in more 

than one well sample (table 14). Pesticide compound concentrations generally were very small—93 percent of all pesticide 

compounds were at concentrations less than 0.1 μg/L. All concentrations of detected pesticides were smaller than USEPA 

standards (table 14). Two or more pesticides or breakdown 

products were found in 12 of the 15 well samples with at least 

one pesticide detection (fig. 18). More than one pesticide compound is commonly found in ground-water samples containing 

pesticides (Gilliom, 2001). The health effects of water containing several pesticides are unknown (Gilliom, 2001). In ground 

water, pesticides also are found frequently in samples containing other contaminants such as nitrate and VOCs (Squillace and 

others, 2002). 

The most frequently detected pesticide (as a parent compound) in samples from the Quaternary aquifers was the herbicide atrazine (7 of 25 samples). Atrazine is a selective herbicide 

used primarily on corn. The breakdown products of atrazine 

also were detected frequently—deethylatrazine (8 of 25 samples), deethyl deisopropylatrazine (7 of 25 samples), deisopropylatrazine (2 of 25 samples), and hydroxyatrazine (1 sample) 

(table 14). Combined, atrazine and its related breakdown products accounted for 25 of 56 (about 45 percent) detections of pesticide compounds. Breakdown products of atrazine and some 

other pesticides are commonly found as frequently and at higher 

frequencies than the parent compounds in ground water in the 

United States (Gilliom, 2001). 

Most of the pesticide compounds detected in samples from 

Quaternary aquifers are primarily used for agricultural purposes, but two of the more frequently detected pesticides 

(prometon and tebuthiuron) have other uses. Prometon was 

detected in 6 of 24 samples from Quaternary aquifers and is 

commonly used as an herbicide in urban areas in the United 

States (Barbash and Resek, 1996). Tebuthiuron was detected 

in 6 of 25 samples and is commonly used as an herbicide in both 

agricultural and nonagricultural areas. The largest concentration of any pesticide compound was tebuthiuron in one sample 

at a concentration of 1.36 μg/L; however, this concentration 

was still much smaller than the USEPA drinking-water standard 

of 500 μg/L (table 14). 

Pesticide compounds were detected much less frequently 

in samples from lower Tertiary aquifers than in samples from 

Quaternary aquifers. Detections coincided with agricultural 

areas (fig. 19). Six pesticide compounds were detected in samples from 4 of 29 wells in lower Tertiary aquifers (table 15; fig. 

19; appendix 9-2). Sixty-two percent of the total eight detections were herbicides and 37 percent were herbicide breakdown 

products. One well sample (SUS2-27, fig. 19) accounted for 4 

of the total 8 detections. The sample from well SUS2-27 also 

had an elevated nitrate concentration, another indicator of contamination by human activities. Atrazine and related breakdown products accounted for 4 of the total 8 pesticide detections 

in lower Tertiary aquifers. All concentrations were smaller than 

USEPA standards (table 14). Two or more pesticide compounds were found in only two well samples (fig. 19). 

Pesticide compounds were detected more often in Quaternary aquifers than in lower Tertiary aquifers in the Bighorn 

Basin. Cropland overlies about 22 percent of Quaternary aquifers in the Bighorn Basin (fig. 18). Most cropland was irrigated, 

so transport of water soluble pesticides through soils to shallow 

aquifers was possible during infiltration of irrigation water. 

Much of the development in the Bighorn Basin overlies Quaternary aquifers (fig. 18), and there were likely many potential 

sources for the nonagricultural pesticides detected. Quaternary 

aquifers in the Bighorn Basin are unconfined, often very permeable, and the water table is close to land surface, making these 

aquifers vulnerable to surficial contaminants. Lower Tertiary 

aquifers are less vulnerable to contamination than the Quaternary aquifers because less area is overlain by irrigated cropland 

(about 10 percent) and because of hydrogeologic characteristics. The water table generally is deeper than in Quaternary 

aquifers, and the lower Tertiary aquifers consist of consolidated 

rocks that inhibit or reduce the flow of water and dissolved pesticides to these aquifers. Barbash and Resek (1996) reported 

that well depth was the factor most commonly correlated with 

pesticide detections in ground water. They also noted that pesticides were detected more frequently in unconsolidated aquifers compared to consolidated (bedrock) aquifers. 

The frequency of pesticide detection in samples from both 

Quaternary and lower Tertiary aquifers was compared with estimates of the area to which the 20 most commonly used pesticides in the Bighorn Basin in Wyoming and Montana were 

applied (Montana Agricultural Statistics Service, 1994; Ferrel 

and others, 1996; Burger, 1997) (fig. 20). Fifteen of the 20 most 

commonly used pesticides were included in the NAWQA analytical methods used to analyze samples collected from both 

aquifers. Estimates of pesticide use in Montana were limited to 

agricultural application (Montana Agricultural Statistics Service, 1994), whereas the Wyoming estimates included both 

agricultural and nonagricultural application (Ferrel and others, 

1996; Burger, 1997). Ferrel and others (1996) estimated pesticides used on different types of crops in Wyoming for 1994, and 

the percentage of crop acreage treated with specific pesticides. 
Ground-Water Quality 65 

Table 14. Summary of pesticides detected in ground-water samples collected from Quaternary aquifers 

[Concentrations of pesticides shown in italics are considered minimums because holding times were exceeded and the compound may have degraded prior to 

analysis. USGS, U.S. Geological Survey; LRL, laboratory reporting level; USEPA, U.S. Environmental Protection Agency; NC, not calculated; M, compound 

detected but not quantified; E, estimated concentration; --, not applicable] 

USGS Median Maximum 

laboratory concentration concentration USEPA 

parameter Number of Number of Primary LRL of detections detected standard 

Pesticide code detections analyses (μg/L) (μg/L) (μg/L) (μg/L) 

Atrazine 39632 7 25 0.001 0.01 0.065 13 

Benfluralin 82673 1 24 .002 NC E.001 --

Bentazon 38711 2 25 .02 NC M 2200 

Bromacil 04029 1 25 .08 NC M 290 

Cyanazine 04041 1 24 .004 NC E.066 21 

DCPA 82682 3 24 .002 E.002 E.002 270 

Deethylatrazine 04040 8 25 .002 E.008 E.015 --

Deethyl deisopropylatrazine 04039 7 25 .06 NC M --

Deisopropylatrazine 04038 2 25 .07 NC M --

Dieldrin 39381 1 24 .001 NC E.003 3

.002 

Dinoseb 49301 2 25 .04 NC M 17 

Diuron 49300 1 25 .08 NC M 210 

Hydroxyatrazine 50355 1 25 .2 NC M --

Metolachlor 39415 1 24 .002 NC .009 2100 

Picloram 49291 1 25 .07 NC M 1500 

Prometon 04037 6 24 .02 .04 .33 2100 

Simazine 04035 4 24 .005 E.005 .011 14 

Tebuthiuron 82670 6 25 .01 .06 1.36 2500 

Trifluralin 82661 1 24 .002 NC E.001 2

5 

1

U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) (U.S. Environmental Protection Agency, 2002)
 2U.S. Environmental Protection Agency Lifetime Health Advisory (HAL) (U.S. Environmental Protection Agency, 2002)
 3

U.S. Environmental Protection Agency Risk-Specific Dose at 10-5 Cancer Risk (RSD5) (U.S. Environmental Protection Agency, 2003a, 2003b)

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66 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana ��������������������������������������������������� ������������������������������������� ������������������ ������������� ������ �� ��� ��������� ����������� ������ �������������� �������� ������������������������������������������� ��������� ������������������ ������������������������������������������������������� ���������������������������������������������������������� ��������������������������������������������������������������� ���������������� ���������������������������������������� �������������������������������������������� ����� ���� ���� � ������ ��� � �

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Figure 18. Pesticide detections in ground-water samples collected from Quaternary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2000.
Ground-Water Quality 67 

Table 15. Summary of pesticides detected in ground-water samples collected from lower Tertiary aquifers 

[USGS, U.S. Geological Survey; LRL, laboratory reporting level; μg/L, micrograms per liter; USEPA, U.S. Environmental Protection Agency; NC, not calculated; E, estimated concentration; --, not applicable] 

Pesticide 

Atrazine 

USGS 

laboratory 

parameter 

code 

P39632 

Number of 

detections 

1 

Number of 

analyses 

29 

Primary LRL 

(μg/L) 

0.001 

Median 

concentration 

of detections 

(μg/L) 

NC 

Maximum 

concentration 

detected 

(μg/L) 

E0.003 

USEPA 

standard 

(μg/L) 

13 

Bentazon P38711 2 29 .02 E0.2 E.32 2200 

Clopyralid P49305 1 29 .04 NC .02 --

Deethylatrazine P04040 1 29 .002 NC E.003 --

Deisopropylatrazine P04038 2 29 .07 E.06 E.07 --

Prometon P04037 1 29 .018 NC .257 2

100 

1

U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) (U.S. Environmental Protection Agency, 2002) 2

U.S. Environmental Protection Agency Lifetime Health Advisory (HAL) (U.S. Environmental Protection Agency, 2002) 

All crops were treated with more than one pesticide, and many 

pesticides were applied to several crops. The total acres treated 

with each pesticide shown on figure 20 was estimated by multiplying the acres of a particular crop grown in the basin during 

1994 (Montana Agricultural Statistics Service, 1994; Burger, 

1997) by the percentage of the crop acreage that was treated 

with that pesticide in 1994 (Ferrel and others, 1996). Then, all 

uses of the pesticide were summed to determine the total acres 

treated with each pesticide in the Bighorn Basin. Although 

Ferrel and others (1996) estimates are for only Wyoming, pesticide use was assumed to extend into Montana. This assumption 

is believed to be valid because crops and crop management are 

similar throughout the Bighorn Basin study area. 

With few exceptions, pesticides detected in ground-water 

samples from both aquifers generally were not the most frequently used pesticides in the Bighorn Basin (fig. 20). Only 3 

of the 20 most commonly used pesticides were detected— 

clopyralid in 1 sample from the lower Tertiary aquifers, picloram in 1 sample from the Quaternary aquifers, and tebuthiuron 

in 6 samples from the Quaternary aquifers. Many different factors affect the occurrence and behavior of pesticides in ground 

water (Barbash and Resek, 1996). However, the lack of detection of many of the most frequently used pesticides in the Bighorn Basin indicates that many pesticides used are not being 

transported to aquifers. 

Considering the rate of atrazine use in the Bighorn Basin, 

the frequent detection of atrazine and related breakdown products in both aquifers is conceivable. As noted earlier, atrazine 

is used primarily on corn, and a minor amount of corn is grown 

in the Bighorn Basin (about 4 percent of acreage, fig. 21). Atrazine and its breakdown product deethylatrazine are the two 

most frequently detected pesticide compounds in shallow 

ground water in the United States, including areas where use is 

relatively small compared to other pesticides (U.S. Geological 

Survey, 1998; Squillace and others, 2002). The frequent detection of atrazine and related breakdown products in shallow 

ground water is likely because of their high mobility and longlived nature (U.S. Geological Survey, 1998). 

In three Wyoming counties within the Bighorn Basin (Bighorn, Park, and Washakie Counties, fig. 19), shallow ground 

water considered vulnerable to pesticide contamination was 

recently sampled in three cooperative studies between the 

USGS and Wyoming Department of Agriculture (Eddy-Miller, 

1998a; 1998b; Eddy-Miller and Norris, 2001). Shallow ground 

water in these counties was ranked as some of the most vulnerable to pesticide contamination in Wyoming, on the basis of 

hydrogeologic characteristics, amount of agricultural and urban 

land use, and pesticide use (Wyoming Ground-Water and Pesticides Strategy Committee, 1999). Most of the ground-water 

samples in these studies were collected from Quaternary aquifers in the Bighorn Basin study area. In general, results of these 

three studies were similar to the major results of this study: 

(1) pesticides were detected but generally at trace-level concentrations much lower than USEPA standards; (2) the detection 

frequency of a particular pesticide compound in ground water 

did not necessarily match frequency of use (fig. 20); (3) most 

pesticides detected were herbicides; (4) atrazine and related 

breakdown products were detected frequently; and (5) some of 

the more frequently detected pesticides are not exclusively used 

for agricultural purposes (prometon and tebuthiuron). 
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68 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana ����� ������ ��� �

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Figure 19. Pesticide detections in ground-water samples collected from lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 2000-2001. 
Ground-Water Quality 69 

100,000 10 

9

BIGHORN BASIN STUDY AREA PESTICIDE APPLICATION (ACRES)

40,000 4 

3 

20,000 2 

1 

0 

Pesticides in NAWQA analytical methods 

Pesticides not part of NAWQA analytical methods 

Number of detections in Quaternary aquifers subunit survey

 (25 ground-water samples) 

Number of detections in lower Tertiary

 aquifers subunit survey ground-

 water samples 

(29 

) 

Number of detections in U.S. Geological

 (107 ground-water samples 

 Survey/Wyoming Department of

 Agriculture cooperative studies

)

 (Eddy-Miller, 1998a, 1998b;

 Eddy-Miller and Norris, 2001) 

0 

80,000 8 

7 

6 

5 

NUMBER OF DETECTIONS OF PESTICIDES IN A

QUIFER STUDIES 

60,000 

Aldicarb (18)

Carbofuran (8)

Chlorsulfuron (7)

Clopyralid (5)

Cycloate (18)

2,4-D (1)

Desmedipham (10)

Dicamba (9)

EPTC (20)

Ethalfluralin (16)

Ethofumesate (12)

Malathion (14)

MCPA (13)

Metsulfuron (3)

Phenmedipham (10)

Picloram (2)

Sethoxydim (15)Tebuthiuron (17)

Terbufos (6)

Triallate (4) 

Figure 20. Twenty most commonly used pesticides in the Bighorn Basin, Wyoming and Montana, 1994, and comparison 

with frequency of detection in ground-water samples collected from Quaternary and lower Tertiary aquifers, 1999-2001 

(values calculated using Ferrel and others, 1996, Burger, 1997, and Montana Agricultural Statistics Service, 1994). 

Number in parentheses after pesticide name is rank of use. 

Volatile Organic Compounds 

Volatile organic compounds (VOCs) are generally manmade chemicals in many commonly used products such as plastics, paints, refrigerants, gasoline, fuel oils, lubricants, solvents, 

fumigants, pesticides, personal hygiene products, and disinfection byproducts. Many VOCs are highly soluble, mobile, and 

persistent in ground water. In addition, many VOCs are suspected carcinogens or have some type of health risk associated 

with exposure. Therefore, USEPA regulatory standards have 

been established for many VOCs in drinking water. 

Ground-water samples collected from Quaternary and 

lower Tertiary aquifers were analyzed for 85 VOCs using 

GC/MS (appendixes 10-1 and 10-2). Measured VOC concentrations are shown in relation to laboratory reporting levels (LRLs). 

LRLs may be increased for certain samples due to sample matrix 

interference, small sample volume, or if warranted by results 

from laboratory QC samples. Most detected VOC concentrations were very small, and many of the detections were smaller 

than the LRL and the lowest laboratory calibration standard. 

These concentrations are reported as estimated concentrations in 

tables and the appendixes and are qualified with an “E” code preceding the reported laboratory concentration. 

At least one VOC was detected in 21 of 25 well samples 

(about 85 percent) from Quaternary aquifers (appendix 10-1; 

table 16; fig. 22). Nine different VOCs were detected, six of 

which commonly are associated with gasoline. The VOC 1,2,4­

trimethylbenzene (VOC in gasoline or occurs naturally in coal 

tar and petroleum crude oil (U.S. Environmental Protection 

Agency, 1995)) was detected most frequently (18 of 25 samples) 

and at the highest concentrations. However, the detections and 

reported concentrations of 1,2,4-trimethylbenzene should be 

used with caution because of QC problems with the VOC noted 

previously in the report. Other gasoline-associated hydrocarbons detected were benzene (9 samples), 1-methylethylbenzene 

(2 samples), 2-ethyltoluene (1 sample), 1-isopropyl-4-methyl­
70 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

4 percent 4 percent 4 percent (19,800 acres) (18,200 acres) 

3 percent 

(14,400 

acres) 

10 percent 

(52,000 14 percent 

9 percent acres) 1 percent (59,000

acres) 

15 percent 

(78,700 acres) (15,500 

(7,500 

acres) 

4 percent 

5 percent 

(19,900 acres) 

38 percent 

(207,000 acres) 38 percent 

(163,000 acres) 

17 percent 

(93,400 acres) 

22 percent 

(20,000 acres) 

(44,710 

acres) 

(90,900 acres) 

(48,860 

acres) 11 percent 

acres) 

1994 ACREAGE 

(534,160 acres) 

EXPLANATION 

Hay and alfalfa Small grains 

Hay (non-alfalfa) Barley 

Alfalfa Oats 

Wheat 

2000 ACREAGE 

(418,710 acres) 

Row crops 

Sugarbeets


Dry Beans


Corn 

Figure 21. Crop types and percentage of total crop production for the years 1994 and 2000 in the Bighorn Basin, Wyoming and 

Montana. Compiled from Burger (1997, 2002) and Montana Agricultural Statistics Service (1994, 2000). 

benzene (1 sample) and n-propylbenzene (1 sample). The other 

VOCs detected were solvents: carbon disulfide (4 samples), tetrahydrofuran (1 sample), and tetrachloroethene (1 sample). 

One or more VOCs were detected in 14 of 29 well samples 

(48 percent) from lower Tertiary aquifers (appendix 10-2; 

table 17; fig. 23). Seven different VOCs were detected in at 

least one well sample. VOCs detected in the lower Tertiary 

aquifers were different from those detected in Quaternary aquifers—only two detections (benzene) were of gasoline compounds. Other VOCs detected were solvents (carbon disulfide, 

4 samples; tetrachloroethene, 1 sample; tetrahydrofuran, 4 samples) or trihalomethanes (chloromethane, 8 samples; trichloromethane, 3 samples; and bromodichloromethane, 1 sample). 

Concentrations of VOCs in both types of aquifers generally were very small, always less than established USEPA 

drinking-water standards. In fact, most concentrations were 

less than 0.05 μg/L and were estimated concentrations. 

The detection of the VOC carbon disulfide in 8 groundwater samples collected from Quaternary aquifers (4 samples) 

and lower Tertiary aquifers (4 samples) was unexpected. Carbon disulfide is used in the manufacture of a wide variety of 

products (Verschueren, 1983) and there are no known sources 

in the Bighorn Basin. However, measured concentrations were 

low (tables 16 and 17), and there are natural sources of carbon 

disulfide in the environment. Carbon disulfide is naturally 

emitted from many soils, particularly soils with much organic 

material, and through bacterial interactions with sulfide minerals such as pyrite (Verschueren, 1983; Newhook and others, 

2002). Other natural sources of carbon disulfide in the environment are forest and grass fires and volcanoes (Newhook and 

others, 2002). 

About one-half of the VOC detections (12 of 23 detections) in the lower Tertiary aquifers were trihalomethanes. 

Although trihalomethanes have some natural sources (Moran 

and others, 2002, and references therein), trihalomethanes in 

water commonly are the byproducts of chlorine disinfection. 

Chlorine disinfection (also known as shock chlorination) is a 

process whereby a solution of bleach (typically sodium 

hypochlorite) and water is added to a well to kill bacteria. The 

addition of this solution to the well adds free chlorine that can 

react with naturally occurring organic matter in the water to create trihalomethanes (Trussell and Umphres, 1978; Alawi and 

others, 1994). Moran and others (2002, p. 42) also noted that 

some trihalomethanes “might form through the same reactions 

during the use of household bleach in washing machines” and 

speculated that “wastewater discharged from the washing 

machine to a septic system may enter shallow ground water near 

the domestic well.” 
Ground-Water Quality 71 

Table 16. Summary of volatile organic compounds (VOCs) detected in ground-water samples collected from Quaternary aquifers 

[USGS, U.S. Geological Survey; LRL, laboratory reporting level; μg/L, micrograms per liter; USEPA, U.S. Environmental Protection Agency; MCL, U.S. 

Environmental Protection Agency Maximum Contaminant Level; ND, not detected above minimum reporting level; E, estimated concentration; M, compound detected but not quantified; --, not applicable] 

Volatile organic compound 

(VOC) 

Benzene 

Common name 

Benzene 

USGS 

laboratory 

parameter 

code 

34030 

Number of 

detections 

9 

Number of 

analyses 

25 

Primary 

LRL 

(μg/L) 

0.04 

Concentration 

range 

(μg/L) 

ND - E0.07 

USEPA 

MCL 

(μg/L) 

5 

Carbon disulfide Carbon disulfide 77041 4 25 .07 ND - E.16 --

2-Ethyltoluene ortho-Ethyltoluene 77220 1 25 .06 ND - E.01 --

1-Isopropyl-4-methylbenzene para-Cymene 77356 1 25 .07 ND - E.01 --

(1-Methylethyl)benzene Cumene 77223 2 25 .03 ND - E.01 --

n-Propylbenzene Isocumene 77224 1 25 .04 ND - E.01 --

Tetrachloroethene Perchloroethene (PCE) 34475 1 25 .1 ND - M 5 

Tetrahydrofuran Diethylene oxide 81607 1 25 2 ND - M --

1,2,4-Trimethylbenzene Pseudocumene 77222 18 25 .06 ND - .7 --

Tetrahydrofuran was detected in samples from four wells 

completed in lower Tertiary aquifers and one well completed in 

Quaternary aquifers. This VOC frequently is used in cements 

and primers used to join polyvinyl chloride (PVC) plastic piping (National Institutes of Health, 2004). PVC often is used in 

wells or home plumbing to join pieces of well casing or pipe. 

Primers and adhesives used to join well casing have been shown 

to leach several VOCs, including tetrahydrofuran, in laboratory 

and environmental samples (Lapham and others, 1995, and references therein). All samples from wells in the lower Tertiary 

aquifers with detections of tetrahydrofuran were constructed of 

PVC (table 3). However, the well owners did not have information to determine if PVC primers and adhesives were used in the 

construction of the sampled wells. Although tetrahydrofuran 

was detected in one sample from a well completed in Quaternary aquifers, PVC primers or adhesives were not the likely 

source of the VOC because all monitoring wells installed for the 

study were constructed with threaded, rather than glued wellcasing joints. 

The detection of VOCs in well samples in the study area 

may at first appear to be unexpected because very little of the 

land use is commercial and industrial—both land uses that are 

commonly associated with VOC contamination in ground 

water. However, as noted in Moran and others (2002), VOCs 

have been detected frequently in rural domestic wells throughout the United States, although generally at very small concentrations much lower than regulatory standards. It is very difficult to determine the sources of VOCs detected in ground-water 

samples because VOCs can be from natural sources, well construction and maintenance, leaks or spills at the land surface, or 

septic system effluent. In addition, most VOCs have multiple 

uses because they are used in many different products. Potential sources of VOCs near rural domestic wells are leaks from 

underground and aboveground storage tanks that hold gasoline, 

diesel fuel, or heating oil; shock chorination for well disinfection; pesticide application; and septic systems (Moran and others, 2002, and references therein). Many of the same VOCs 

detected in both the Quaternary and lower Tertiary aquifers 

samples also were found in samples from rural domestic wells 

inventoried by Moran and others (2002). Although there are 

many potential sources of these VOCs, many are common 

ingredients in household products and may be disposed in septic 

systems; some of these VOC ingredients have been found in the 

fluid in septic tanks (also known as septage), in the effluent of 

septic systems (effluent), or in shallow ground water in areas 

with high septic-system density (Moran and others, 2002, and 

references therein). 
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72 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Figure 22. Volatile organic compounds (VOCs) detected in ground-water samples collected from Quaternary aquifers, Bighorn Basin, Wyoming and Montana, 1999-2000.
Ground-Water Quality 73 

Table 17. Summary of volatile organic compounds (VOCs) detected in ground-water samples collected from lower Tertiary aquifers 

[USGS, U.S. Geological Survey; LRL, laboratory reporting level; μg/L, micrograms per liter; USEPA, U.S. Environmental Protection Agency; ND, not detected above minimum reporting level; E, estimated concentration; --, not applicable] 

Volatile organic compound 

(VOC) 

Benzene 

Common name 

Benzene 

USGS 

laboratory 

parameter 

code 

34030 

Number of 

detections 

2 

Number of 

analyses 

29 

Primary 

LRL 

(μg/L) 

0.04 

Concentration 

range 

(μg/L) 

ND - 0.15 

USEPA 

standard 

(μg/L) 

1

5 

Bromodichloromethane Dichlorobromomethane 32101 1 29 .05 ND - .32 1,280 

Carbon disulfide Carbon disulfide 77041 4 29 .07 ND - E.05 --

Chloromethane Methyl chloride 34418 8 29 .5 ND - E.1 3

3 

Tetrachloroethene Perchloroethene (PCE) 34475 1 29 .1 ND - M 15 

Tetrahydrofuran Diethylene oxide 81607 4 29 2 ND - 26 --

Trichloromethane Chloroform 32106 3 29 .05 ND - .65 1,280 

1U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) (U.S. Environmental Protection Agency, 2002, 2003b).
 2

Total for all trihalomethanes combined cannot exceed 80 μg/L.
 3U.S. Environmental Protection Agency Lifetime Health Advisory (HAL) (U.S. Environmental Protection Agency, 2003a, 2003b).


Because of the generally rural nature of much of the study 

area, sources of potential VOC contamination to wells were 

somewhat limited. Although some wells were in areas that 

could be considered “urban,” the land use around most wells, as 

noted previously in the land use and land cover section of this 

report, generally was rural, consisting primarily of agricultural 

land, “other agricultural land,” and rangeland. The “other agricultural land” land-use category commonly included homes and 

agricultural infrastructure surrounded by cropland. During 

mapping of land use and land cover within 500 m of sampled 

wells, potential sources of contamination were noted and inventoried. Based on this inventory, the most likely potential point 

sources of VOC contamination to wells in predominantly rural, 

non-urban areas, appeared to be above-ground storage tanks 

(ASTs) used to store gasoline and diesel fuel (for domestic and 

agricultural purposes), domestic septic systems, and pesticide 

application. Many ASTs used to store gasoline and diesel fuel 

were inventoried by the authors. As noted earlier, many of the 

VOCs detected in both aquifers (but primarily Quaternary aquifers) are components of gasoline. Spills or leaks near ASTs are 

potential sources of VOC contamination to domestic wells 

(U.S. Environmental Protection Agency, 2000). Although 

VOCs have been found frequently in septage and effluent, their 

presence does not prove that the source of shallow groundwater contamination is the septic system. However, some 

investigators have noted that many VOCs detected in shallow 

ground water also are known to be components in household 

products such as cleansers and personal hygiene products 

(Moran and others, 2002, and references therein). Many of 

these products may be disposed into septic systems. Septic systems that are improperly designed, maintained, or operated can 

contaminate shallow ground water near the system, primarily 

due to effluent from the leachfield reaching shallow ground 

water prior to complete degradation of organic material (U.S. 

Environmental Protection Agency, 2000). 

It is difficult to determine if some of these trace-level VOC 

detections (less than 0.05 μg/L) in samples from both types of 

aquifers are actually in water from the aquifers (environmental 

detections) or if they are due to sample contamination during 

sampling or laboratory analysis. To learn as much as possible 

about VOCs in ground water, the USGS NWQL developed 

methods to detect VOCs at very small concentrations (as low as 

about 5 nanograms per liter). Although these very sensitive 

analytical methods can increase the chances of detecting VOCs 

in ground water, they also increase the chances of detecting 

VOCs from other sources such as contamination from sampling 

and laboratory processes. The use of quality-assurance processes and quality-control data, along with other ancillary data, 

was very important in the interpretation of the VOC sample 

results. However, despite the use of stringent QA/QC processes 

and procedures, some VOC detections may be the result of random sample contamination (John Zogorski, U.S. Geological 

Survey, oral commun., 2003). 
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74 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana ���������� ��� ��� ���� ������ ��������������� ������ ������������������������������������������������� ��������������������������������������������������� ������ �� ��� ��������� ����������������������������������������������������������� ������������������������������������������������������������ �������������������������������������������������������� ����������������������������������������� ����� ������ ������ ���

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Figure 23. Volatile organic compounds (VOCs) detected in ground-water samples collected from lower Tertiary aquifers, Bighorn Basin, Wyoming and Montana, 2000-01. 
SUMMARY 

From 1999 to 2001, 54 wells were sampled in the Bighorn 

Basin of Wyoming and Montana as part of the Yellowstone 

River Basin National Water-Quality Assessment study. Of the 

54 wells, 25 were completed in Quaternary unconsolidateddeposit aquifers and 29 were completed in lower Tertiary aquifers. All but one well in the Quaternary aquifers were monitoring wells installed specifically for the study, whereas all the 

wells in the lower Tertiary aquifers were existing wells. Samples from all wells were analyzed for physical characteristics, 

major ions, trace elements, nutrients, dissolved organic carbon 

(DOC), radionuclides, pesticide compounds, and volatile 

organic compounds (VOCs) to provide a thorough description of 

current (1999-2001) water-quality conditions in both types of 

aquifers. 

Several major anions were detected at concentrations 

greater than U.S. Environmental Protection Agency (USEPA) 

Secondary Maximum Contaminant Levels (SMCLs). The chloride SMCL of 250 milligrams per liter (mg/L) was exceeded in 

only one sample from Quaternary aquifers. In more than onehalf of samples from both aquifers, the concentration of sulfate 

was greater than the SMCL of 250 mg/L. The fluoride Maximum Contaminant Level (MCL) of 4 mg/L was exceeded in 

only one sample from Quaternary aquifers and two samples 

from lower Tertiary aquifers. However, the SMCL (2 mg/L) for 

fluoride was exceeded more frequently in both types of aquifers 

and almost one-third (10 of 29 samples) of the samples from 

lower Tertiary aquifers exceeded the standard. 

Waters from both types of aquifers generally were high in 

dissolved solids and were variable in water type. Because of the 

generally high mineralization, waters from 12 of 25 samples 

from Quaternary aquifers and 17 of 29 samples from lower Tertiary aquifers were not classified as fresh (dissolved-solids concentrations were not less than 1,000 mg/L). The USEPA SMCL 

for dissolved solids (500 mg/L) was frequently exceeded in samples from both aquifers—18 of 25 samples from Quaternary 

aquifers and 27 of 29 samples from lower Tertiary aquifers 

exceeded the standard. 

In both types of aquifers, the predominant anion changes 

from bicarbonate to sulfate with increasing dissolved-solids concentrations. Samples from Quaternary aquifers with fresh waters 

(dissolved-solids concentrations less than 1,000 mg/L) generally 

were calcium-bicarbonate, calcium-sodium-bicarbonate, and 

calcium-sodium-sulfate-bicarbonate type waters, whereas samples with larger dissolved-solids concentrations generally were 

calcium-sodium-sulfate, calcium-sulfate, or sodium-sulfate type 

waters. In the lower Tertiary aquifers, samples with fresh waters 

(dissolved-solids concentrations less than 1,000 mg/L) generally 

were sodium-bicarbonate or sodium-bicarbonate-sulfate type 

waters, whereas samples with larger concentrations were 

sodium-sulfate or calcium-sodium-sulfate types. 

Hardness values were calculated for all ground-water samples, and median concentrations were significantly different 

between aquifers. Based on four hardness classes, most waters 

SUMMARY 75 

from Quaternary aquifers were classified as very hard (hardness 

greater than 180 mg/L). In contrast, hardness varied much more 

in waters from lower Tertiary aquifers and ranged from soft (less 

than 60 mg/L) to very hard (greater than 180 mg/L). 

Concentrations of most trace elements in both types of 

aquifers generally were small and most were smaller than applicable USEPA regulatory limits. Six trace elements were not 

detected in water from any of the wells sampled. Concentrations 

of most trace elements in both types of aquifers varied considerably, and median concentrations of most were significantly different between aquifers. Iron and manganese were the only trace 

elements measured in samples from the Quaternary aquifers at 

concentrations greater than USEPA standards (SMCLs). Six 

trace elements (boron, cadmium, iron, manganese, molybdenum, and selenium) were measured in some samples from lower 

Tertiary aquifers at concentrations larger than applicable 

USEPA regulatory standards. In most cases, the USEPA standards for these trace elements were exceeded in only one or two 

samples from lower Tertiary aquifers. However, at least 10 percent of the samples collected from each aquifer exceeded their 

respective SMCLs for iron and manganese. In fact, the manganese SMCL was the most frequently exceeded standard, and 

68 percent of the samples from the Quaternary aquifers and 

31 percent of the samples from the lower Tertiary aquifers 

exceeded the standard. 

Like most trace elements, the concentrations of iron and 

manganese in ground water are often controlled by geochemical 

conditions rather than abundance in the rocks and minerals comprising the aquifers. Although iron concentrations in waters 

from the Quaternary and lower Tertiary aquifers were not significantly correlated with measured pH or dissolved oxygen concentrations, manganese concentrations in the Quaternary aquifers were negatively correlated with dissolved oxygen concentrations (p-value=0.0221 and Spearman’s rho=-0.4667); 

concentrations in lower Tertiary aquifers were negatively correlated with measured pH (p-value=0.0036 and Spearman’s 

rho=-0.5503). 

With the exception of nitrate (nitrite plus nitrate), nutrient 

concentrations in samples from both types of aquifers were less 

than applicable USEPA standards. Nitrate was detected more 

frequently and generally at higher concentrations in samples 

from Quaternary aquifers than in samples from lower Tertiary 

aquifers, but median concentrations were not significantly different (p-value greater than 0.05). Nitrate concentrations in 2 of 

25 samples from the Quaternary aquifers and 1 of 29 samples 

from lower Tertiary aquifers were larger than the MCL of 

10 mg/L. 

Some DOC concentrations in samples from both types of 

aquifers were higher than reported for other ground waters in the 

United States. Concentrations of DOC ranged from 0.61 to 

38 mg/L in samples from the Quaternary aquifers and from 0.32 

to 8.2 mg/L in samples from lower Tertiary aquifers. The high 

concentrations in Quaternary aquifers may be due to the influence of surface water, and the concentrations in lower Tertiary 

aquifers may be due to coal and organic shales associated with 

the geologic formations comprising the aquifers. 
76 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

Dissolved oxygen (DO) and DOC concentrations were 

related to the species of nitrogen in ground water. A weak negative correlation (p-value=0.0749; Spearman’s rho=-0.3632) 

was noted between DO and DOC concentrations in samples 

from Quaternary aquifers, whereas no correlation was noted in 

samples from lower Tertiary aquifers. In Quaternary aquifers, 

DO was not correlated with any of the nitrogen species. DOC 

concentrations in Quaternary aquifers were positively correlated with ammonia plus organic nitrogen concentrations 

(p-value=0.0004; Spearman’s rho=0.7181) and nitrite concentrations (p-value=0.0497; Spearman’s rho=0.4009). No correlations were noted between DO and ammonia, nitrate, or nitrite 

concentrations in Quaternary aquifers. DOC concentrations 

were not correlated with ammonia and nitrate concentrations. 

For comparative purposes, nitrogen species in samples from 

lower Tertiary aquifers were grouped into “old” (waters older 

than 50 years) or “modern” (waters younger than 50 years) 

ground-water age categories based on tritium concentrations. 

DO concentrations in old waters of the lower Tertiary aquifers 

were not correlated with any of the nitrogen species. In contrast, DO concentrations in modern waters were negatively correlated with ammonia (p-value=0.0135; Kendall’s tau=-0.5000) 

and weakly negatively correlated with ammonia plus organic 

nitrogen (p-value=0.0853; Kendall’s tau=-0.3590); DO 

concentrations were positively correlated with nitrate 

(p-value=0.0178; Kendall’s tau=0.4872). DOC concentrations 

in old waters of the lower Tertiary aquifers were not correlated 

with nitrate or nitrite but were positively correlated with ammonia (p-value=0.0059; Kendall’s tau=0.5495) and ammonia plus 

organic nitrogen (p-value=0.0082; Kendall’s tau=0.5275). 

DOC concentrations in modern waters were not correlated with 

ammonia or ammonia plus organic nitrogen but were positively 

correlated with nitrate (p-value=0.0130; Kendall’s tau=0.4667). 

Concentrations of some nutrients were, in part, related to 

the percentage of different land uses within 500 meters of the 

wells. Ammonia concentrations in samples from Quaternary 

aquifers were negatively correlated with the percentage of 

“other agricultural” land (non-cropland) (p-value=0.0050, 

Spearman’s rho=-0.5715) and positively correlated with the 

percentage of “other” land mapped around the wells 

(p-value = 0.0354, Spearman’s rho=0.4298). Nitrate concentrations in Quaternary aquifers were positively correlated with the 

percentage of cropland (p-value=0.0041; Spearman’s 

rho=0.5865) and other agricultural land (p-value=0.0448; 

Spearman’s rho=0.4099) and negatively correlated with rangeland (p-value=0.0140; Spearman’s rho=-0.5015) and riparian 

land (p-value=0.0479; Spearman’s rho=-0.4034). In samples 

from lower Tertiary aquifers, nitrate concentrations were positively correlated with percentage of cropland (p-value=0.0219; 

Spearman’s rho=0.4334) and weakly negatively correlated with 

rangeland (p-value=0.0575; Spearman’s rho=-0.3587). Orthophosphate concentrations in lower Tertiary aquifers were 

positively correlated to the percentage of riparian land 

(p-value=0.0320; Spearman’s rho=0.4056) and urban land 

(p-value=0.0248; Spearman’s rho=0.4245). Phosphorus was 

positively correlated to the percentage of urban land 

(p-value=0.0274; Spearman’s rho=0.4171). 

Some radionuclide concentrations in water from wells in 

both aquifers exceeded applicable USEPA standards. Grossalpha activities in 9 of 24 samples from Quaternary aquifers and 

6 of 26 samples from lower Tertiary aquifers were larger than 

the USEPA MCL of 15 picocuries per liter (pCi/L). Uranium 

concentrations were greater than the MCL of 30 micrograms 

per liter (μg/L) in 2 of 25 samples from Quaternary aquifers. 

No summed radium-226 and radium-228 activities from samples in either aquifer exceeded the combined MCL of 5 pCi/L. 

Radon concentrations generally were large in samples from 

both aquifers—all samples from Quaternary aquifers and all but 

two samples from lower Tertiary aquifers had concentrations 

greater than the proposed MCL of 300 pCi/L. No samples from 

Quaternary aquifers had radon activities larger than the proposed alternative MCL of 4,000 pCi/L, but the activity in one 

sample from the lower Tertiary aquifers was larger. 

Organic compounds (pesticide compounds and VOCs), 

which generally are indicators of manmade contamination to 

ground water, were detected in both types of aquifers. At least 

one pesticide compound was detected in 15 of 25 well samples 

in Quaternary aquifers. In contrast, six pesticides or pesticide 

breakdown products were detected in only 4 of 29 wells in 

lower Tertiary aquifers. Most detections in both types of aquifers were herbicides or herbicide breakdown products—only 

one insecticide was detected. All pesticide concentrations were 

smaller than applicable USEPA standards and most measured 

concentrations were at trace levels (less than 0.1 μg/L). Most 

of the pesticides detected in ground water in both types of aquifers are commonly associated with agriculture. However, the 

detection frequency of a particular pesticide compound in 

ground water did not necessarily correspond to use in the Bighorn Basin, and some of the most frequently detected pesticides 

are not used exclusively for agricultural purposes (prometon 

and tebuthiuron). 

VOCs were detected in both types of aquifers but more frequently in Quaternary aquifers. At least one VOC was detected 

in 21 of 25 well samples from Quaternary aquifers and in 14 of 

29 well samples from lower Tertiary aquifers. Nine different 

VOCs were detected in samples from Quaternary aquifers, six of 

which commonly are associated with gasoline. Seven different 

VOCs were detected in samples from lower Tertiary aquifers. 

The VOCs detected in lower Tertiary aquifers were different 

from those detected in Quaternary aquifers as only two detections were of gasoline compounds. Concentrations of VOCs in 

both aquifers were low, always smaller than USEPA MCLs. 

Very sensitive analytical methods with very low reporting levels 

were used. These methods can detect VOCs at very low concentrations in ground water, but they also can increase the chances 

of detecting VOCs from other sources such as contamination 

from sampling and laboratory analytical processes. 

Overall, water from wells sampled in Quaternary and 

lower Tertiary aquifers in the Bighorn Basin are suitable for 

most uses. Some concentrations of major ions and trace elements were greater than USEPA standards and could limit the 
potential uses of some waters, but these exceedances are more 

likely the result of natural factors such as geology and geochemical conditions rather than human activities. However, the presence of nitrate at concentrations above probable natural levels, 

along with the detection of pesticides and VOCs, indicated 

some effects of human activities on ground-water quality. 

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Report 95-352 p. 92. 

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U.S. Environmental Protection Agency, 1980, Prescribed procedures for measurement of radioactivity in drinking water: 

U.S. Environmental Protection Agency, Environmental 

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U.S. Environmental Protection Agency, 1999, 40 CFR Parts 

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U.S. Environmental Protection Agency, 2000, National water 

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wy.gif 
82 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana 

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Wyoming Ground-Water and Pesticides Strategy Committee, 

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Wyoming Department of Agriculture, 103 p. 

Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg, 

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Yellowstone River Basin, Montana, North Dakota, and 

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Investigations Report 98-4269, 112 p. 
84 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Appendix 1-1. Land use and land cover mapped within 500-meter

Well 

number

USGS siteidentification 

number

Date of landuse 

assessment 

(month/day/

year)

Cropland

(percent)

Other Agricultural Land

Rangeland

(percent)

Riparian

Agricultural 

infrastructure 

(percent)

Livestock 

pasture 

(percent)

Miscellaneous 

agricultural 

land

(percent)

Water

(percent)

Wetland/

riparian 

vegetation

(percent)

Quaternary 

SUS1-1 440629109092401 10/19/99 12.4 6.6 -- -- 55.4 -- 25.6

SUS1-2 442618109130202 12/14/99 32.7 -- -- 8.2 14.9 23.5 20.7

SUS1-3 444500109013101 01/21/00 89.2 9.8 -- 1.0 -- -- --

SUS1-4 445613109081401 01/21/00 27.1 12.1 -- -- 38.7 -- 22.0

SUS1-5 451411109134301 03/30/00 11.5 7.8 26.4 -- 8.4 -- 44.5

SUS1-6 453101108512801 11/01/99 28.0 6.6 16.3 -- -- -- 26.9

SUS1-7 451033108575401 11/02/99 77.8 10.5 -- 5.4 -- -- --

SUS1-8 444639108452601 12/13/99 81.0 18.7 -- 0.3 -- -- --

SUS1-9 444126108513401 12/13/99 63.8 13.4 -- 0.7 20.7 -- --

SUS1-10 441556108473201 12/15/99 -- 7.8 10.7 1.5 49.5 -- 30.5

SUS1-11 440213108583501 10/18/99 -- -- 30.6 2.6 40.0 -- 25.0

SUS1-12 434334108351101 12/15/99 -- -- -- 2.8 61.7 -- 35.5

SUS1-13 440027108264501 11/18/99 -- -- -- 2.3 50.5 -- 22.9

SUS1-14 442354108255801 11/17/99 10.6 -- 26.0 2.7 21.8 -- 38.9

SUS1-16 444424108354001 01/21/00 39.1 10.4 -- 0.8 33.1 -- 16.6

SUS1-17 445014108224301 11/03/99 43.5 10.4 2.3 -- -- -- --

SUS1-18 443023108233201 10/20/99 81.6 10.7 -- 1.8 -- -- --

SUS1-19 442258108141201 11/17/99 -- -- -- 0.3 23.0 -- 76.7

SUS1-22 433519108125201 10/05/99 10.4 -- 6.6 5.1 44.6 10.5 11.9

SUS1-24 435010107214701 11/18/99 18.4 -- -- -- 50.0 -- 28.2

SUS1-25 440054107581401 10/14/99 -- -- -- 4.1 -- -- 19.7

SUS1-27 440952107405101 11/18/99 -- -- -- 6.6 66.9 -- 26.5

SUS1-28 441554107560001 10/07/99 30.5 4.6 -- -- 12.6 -- 25.2

SUS1-29 441821108014701 10/21/99 12.0 -- -- 2.0 22.9 -- 62.2

SUS1-30 444719108050501 11/04/99 -- -- -- -- 84.8 -- 12.6
Appendix 1 85

radius of sampled wells, Quaternary aquifers, 1999-2000

Urban Other

Commercial

(percent)

Residential/

commercial 

(percent)

Residential 

(percent)

Miscellaneous 

urban 

(percent)

Other 

urban 

(percent)

Barren 

(percent)

Grass/

forest 

(percent)

Active 

mining 

(percent)

Inactive 

mining 

(percent)

Miscellaneous 

(percent)

Total 

(percent)

aquifers

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- 1.4 -- -- -- -- -- -- 100.0

7.7 -- -- 10.1 -- -- -- -- -- 4.4 100.0

-- -- -- -- -- -- -- -- -- 6.4 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- 1.5 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- 1.9 -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- 24.3 -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

12.1 -- 7.4 4.5 14.1 -- -- 3.0 -- 2.7 100.0

-- -- -- 5.9 -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- 3.5 -- -- 7.5 -- -- -- 100.0

-- -- -- -- -- -- -- -- -- 3.5 100.0

-- 16.7 7.8 5.5 45.5 -- -- -- -- 0.7 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- 27.1 -- -- -- -- 100.0

-- -- -- -- -- -- -- 0.8 -- 100.0

-- -- -- 2.6 -- -- -- -- -- -- 100.0
86 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Appendix 1-2. Land use and land cover mapped within 500-meter 

Well 

number

USGS siteidentification 

number

Date of landuse 

assessment 

(month/day/

year)

Cropland

(percent)

Other Agricultural Land

Rangeland 

(percent)

Riparian

Agricultural 

infrastructure 

(percent)

Livestock 

pasture 

(percent)

Miscellaneous 

agricultural 

land 

(percent)

Water 

(percent)

Wetland/

riparian 

vegetation 

(percent)

Lower Tertiary 

SUS2-1 451608109223001 02/26/01 -- -- 45.7 -- 44.4 -- --

SUS2-2 452239109191101 10/26/00 -- -- 60.9 2.5 18.2 -- 18.5

SUS2-3 452326109065301 10/26/00 47.9 -- -- 10.9 38.2 -- --

SUS2-4 451407109133901 08/09/00 17.2 7.1 29.1 -- 15.4 -- 29.9

SUS2-5 450210109030601 02/28/01 8.2 -- -- -- 88.1 -- --

SUS2-6 450658109010401 02/27/01 -- -- -- -- 95.3 -- --

SUS2-7 445246109084101 10/25/00 -- -- -- -- 80.5 -- 18.2

SUS2-8 444509109010901 10/24/00 82.0 16.9 -- 1.1 -- -- --

SUS2-9 444911108444501 10/24/00 -- 18.0 13.7 5.2 63.1 -- --

SUS2-10 444107108550201 10/24/00 30.9 -- 19.9 -- 23.1 -- 9.5

SUS2-11 444326108424501 10/24/00 85.4 8.0 -- -- -- -- --

SUS2-12 444417108381001 03/01/01 20.1 -- -- 8.0 45.9 -- 26.0

SUS2-13 443426108593501 10/24/00 25.9 -- -- -- 61.5 -- --

SUS2-14 442639108220201 04/18/01 53.6 12.7 20.3 -- 13.3 -- --

SUS2-15 442933108211201 09/18/00 58.3 12.2 -- -- 29.5 -- --

SUS2-16 442239108362001 09/20/00 7.8 -- 5.2 -- 60.2 -- 26.6

SUS2-17 442258108260301 10/24/00 5.8 -- -- -- 82.4 -- --

SUS2-18 442348108082301 10/24/00 34.1 6.4 -- -- 55.4 -- --

SUS2-19 441220108513301 09/20/00 22.2 -- -- 15.4 33.4 -- 26.3

SUS2-20 441639108195501 10/24/00 -- -- -- -- 100.0 -- --

SUS2-22 440943108455001 10/25/00 -- -- -- 0.3 99.7 -- --

SUS2-23 440306108160601 10/23/00 -- -- -- 0.5 99.5 -- --

SUS2-24 441046107562201 10/24/00 79.0 11.2 9.8 -- -- -- --

SUS2-25 440008108272601 10/26/00 40.2 -- -- 3.1 37.0 -- 19.7

SUS2-26 435735108074101 09/21/00 -- -- -- 3.7 76.7 -- 19.6

SUS2-27 440207107553001 09/19/00 11.4 10.5 28.8 -- -- -- 14.6

SUS2-28 435143108090501 10/23/00 7.9 8.7 34.7 -- 30.3 -- 10.8

SUS2-29 435556107580701 10/23/00 34.5 20.0 16.9 -- 28.3 -- --

SUS2-30 435115107454801 10/23/00 -- -- -- -- 100.0 -- --
Appendix 1 87

radius of sampled wells, lower Tertiary aquifers, 2000-2001

Urban Other

Commercial 

(percent)

Residential/

commercial 

(percent)

Residential 

(percent)

Miscellaneous 

urban 

(percent)

Other 

urban 

(percent)

Barren 

(percent)

Grass/

forest 

(percent)

Active 

mining 

(percent)

 Inactive 

Mining 

(percent)

Miscellaneous 

(percent)

Total 

(percent)

aquifers

-- -- -- -- -- -- -- -- -- 9.8 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- 3.0 100.0

-- -- -- 1.3 -- -- -- -- -- -- 100.0

-- -- -- 3.7 -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- 4.8 100.0

-- -- -- 1.3 -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- 8.2 -- 8.5 -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- 6.6 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- 12.6 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- 0.2 -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- 11.8 100.0

-- -- -- 4.1 -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- 2.7 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0

-- -- 33.3 1.4 -- -- -- -- -- -- 100.0

-- -- -- 7.7 -- -- -- -- -- -- 100.0

-- -- -- 0.5 -- -- -- -- -- -- 100.0

-- -- -- -- -- -- -- -- -- -- 100.0
88 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Appendix 2-1. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from 

Quaternary aquifers

Well number Constituent Environmental 

sample

Replicate 

sample

Calculated 

relative-percent 

difference

Major ions, in milligrams per liter

SUS1-7 Calcium 75.5 76.1 <1

SUS1-14 Calcium 68.4 68.4 0

SUS1-18 Calcium 67.1 70.8 5.4

SUS1-25 Calcium 93.6 94.3 <1

SUS1-7 Magnesium 30.2 30.4 <1

SUS1-14 Magnesium 25 25 0

SUS1-18 Magnesium 25.8 27.7 7.1

SUS1-25 Magnesium 24.1 24.3 <1

SUS1-7 Sodium 122 123 <1

SUS1-14 Sodium 47.9 47.9 0

SUS1-18 Sodium 83.2 90.5 8.4

SUS1-25 Sodium 202 200 1.0

SUS1-7 Potassium 5.62 5.3 5.9

SUS1-14 Potassium 2.27 2.27 0

SUS1-18 Potassium 1.58 1.57 <1

SUS1-25 Potassium 5.31 5.37 1.1

SUS1-7 Chloride 18.5 17.8 3.9

SUS1-14 Chloride 3.7 3.7 0

SUS1-18 Chloride 6.3 6.2 1.6

SUS1-25 Chloride 29.5 28.8 2.4

SUS1-7 Sulfate 204 204 0

SUS1-14 Sulfate 165 165 0

SUS1-18 Sulfate 129 129 0

SUS1-25 Sulfate 429 428 <1

SUS1-7 Fluoride 0.4 0.4 0

SUS1-14 Fluoride 0.1 0.1 0

SUS1-18 Fluoride 2.6 2.6 0

SUS1-25 Fluoride 0.7 0.7 0

SUS1-7 Silica 13.3 13.4 <1

SUS1-14 Silica 15.2 15.2 0

SUS1-18 Silica 37.5 40 6.5

SUS1-25 Silica 17.7 17.8 <1

Trace elements, in micrograms per liter unless noted otherwise

SUS1-7 Aluminum 2 2 0

SUS1-18 Aluminum <1 <1 NC

SUS1-25 Aluminum 1 1 0

SUS1-7 Arsenic <2 <2 NC

SUS1-18 Arsenic 4.8 5.1 6.1

Appendix 2-1. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from 

Quaternary aquifers

[<, less than; NC, not calculated; E, estimated concentration; mg/L, milligrams per liter; M, constituent detected but not quantified; C, carbon]
Appendix 2 89

Trace elements, in micrograms per liter unless noted otherwise--Continued

SUS1-25 Arsenic E1.6 2 22.2

SUS1-7 Barium 44 43.6 <1

SUS1-18 Barium 26 26.5 1.9

SUS1-25 Barium 19.7 20 1.5

SUS1-7 Bromide (mg/L) 0.12 0.12 0

SUS1-14 Bromide (mg/L) 0.01 0.01 0

SUS1-18 Bromide (mg/L) 0.04 0.04 0

SUS1-25 Bromide (mg/L) 0.1 0.11 9.5

SUS1-7 Chromium 1 0.9 10.5

SUS1-18 Chromium 1.1 1 9.5

SUS1-25 Chromium <0.8 <0.8 NC

SUS1-7 Cobalt 4.64 4.73 1.9

SUS1-18 Cobalt 4.83 4.94 2.3

SUS1-25 Cobalt 1.11 1.1 <1

SUS1-7 Copper 1.8 1.7 5.7

SUS1-18 Copper 4.2 4.3 2.4

SUS1-25 Copper 1.7 1.8 5.7

SUS1-7 Iron M M NC

SUS1-14 Iron 20 20 0

SUS1-18 Iron <10 <10 NC

SUS1-25 Iron 1,210 1,220 <1

SUS1-7 Manganese 147 145 1.4

SUS1-14 Manganese 723 723 0

SUS1-18 Manganese <1 <1 NC

SUS1-25 Manganese 1,350 1,350 0

SUS1-7 Molybdenum 6.5 6.3 3.1

SUS1-18 Molybdenum 6 6 0

SUS1-25 Molybdenum 2.5 2.5 0

SUS1-7 Nickel 5.79 5.69 1.7

SUS1-18 Nickel 1.62 1.58 2.5

SUS1-25 Nickel 1.72 2 15.1

SUS1-7 Selenium 2.7 2.9 7.1

SUS1-18 Selenium 5.6 6.2 10.2

SUS1-25 Selenium <2.4 <2.4 NC

SUS1-7 Zinc 1 <1 NC

SUS1-18 Zinc <1 <1 NC

SUS1-25 Zinc 1 1 0

Appendix 2-1. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from 

Quaternary aquifers—Continued

Well number Constituent Environmental 

sample

Replicate 

sample

Calculated 

relative-percent 

difference
90 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Nutrients, in milligrams per liter, and dissolved organic carbon

SUS1-7 Nitrite, as nitrogen 0.01 <0.01 NC

SUS1-14 Nitrite, as nitrogen <0.01 <0.01 NC

SUS1-18 Nitrite, as nitrogen <0.01 <0.01 NC

SUS1-25 Nitrite, as nitrogen <0.01 <0.01 NC

SUS1-7 Nitrite + nitrate, as nitrogen 2.92 2.98 2.0

SUS1-14 Nitrite + nitrate, as nitrogen <0.05 <0.05 0

SUS1-18 Nitrite + nitrate, as nitrogen 7.78 7.81 <1

SUS1-25 Nitrite + nitrate, as nitrogen <0.05 <0.05 NC

SUS1-7 Ammonia, as nitrogen 0.069 0.065 6.0

SUS1-14 Ammonia, as nitrogen 0.02 0.022 9.5

SUS1-18 Ammonia, as nitrogen <0.02 <0.02 NC

SUS1-25 Ammonia, as nitrogen 0.25 0.244 2.4

SUS1-7 Ammonia + organic nitrogen, as nitrogen 0.17 0.15 12.5

SUS1-14 Ammonia + organic nitrogen, as nitrogen 0.17 0.14 19.4

SUS1-18 Ammonia + organic nitrogen, as nitrogen 0.32 0.24 28.6

SUS1-25 Ammonia + organic nitrogen, as nitrogen 0.36 0.43 17.7

SUS1-7 Phosphorus, as phosphorus E0.005 <0.006 NC

SUS1-14 Phosphorus, as phosphorus 0.025 0.025 0

SUS1-18 Phosphorus, as phosphorus 0.029 0.028 3.5

SUS1-25 Phosphorus, as phosphorus E0.004 E0.003 28.6

SUS1-7 Orthophosphate, as phosphorus <0.01 <0.01 NC

SUS1-14 Orthophosphate, as phosphorus 0.022 0.025 12.8

SUS1-18 Orthophosphate, as phosphorus 0.027 0.025 7.7

SUS1-25 Orthophosphate, as phosphorus 0.011 0.012 8.7

SUS1-7 Dissolved organic carbon, mg/L as C 2.1 2 4.9

SUS1-14 Dissolved organic carbon, mg/L as C 2 2.2 9.5

SUS1-18 Dissolved organic carbon, mg/L as C 4.2 4.3 2.4

SUS1-25 Dissolved organic carbon, mg/L as C 3.7 3.7 0

Appendix 2-1. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from 

Quaternary aquifers—Continued

Well number Constituent Environmental 

sample

Replicate 

sample

Calculated 

relative-percent 

difference
Appendix 2 91

Appendix 2-2. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from lower 

Tertiary aquifers

Well number Constituent

Environmental 

sample

Replicate 

sample

Calculated 

relative-percent 

difference

Major ions, in milligrams per liter

SUS2-1 Calcium 1.18 1.2 1.7

SUS2-9 Calcium 34.1 34.1 0

SUS2-17 Calcium 2.57 2.57 0

SUS2-19 Calcium 30.5 29.6 3.0

SUS2-1 Magnesium 0.326 0.33 1.2

SUS2-9 Magnesium 16.6 16.2 2.4

SUS2-17 Magnesium 0.688 0.708 2.9

SUS2-19 Magnesium 13.7 13.3 3.0

SUS2-1 Sodium 276 278 0.7

SUS2-9 Sodium 736 751 2

SUS2-17 Sodium 243 246 1.2

SUS2-19 Sodium 135 135 0

SUS2-1 Potassium 0.91 0.91 0

SUS2-9 Potassium 5.35 4.98 7.2

SUS2-17 Potassium 1 1.06 5.8

SUS2-19 Potassium 3.27 2.92 11.3

SUS2-1 Bicarbonate 761 748 1.7

SUS2-9 Bicarbonate 451 444 1.6

SUS2-17 Bicarbonate 397 406 2.2

SUS2-19 Bicarbonate 346 371 7

SUS2-1 Chloride 1.3 1.3 0

SUS2-9 Chloride 25.7 26.7 3.8

SUS2-17 Chloride 15.9 15.3 3.8

SUS2-19 Chloride 4 4 0

SUS2-1 Sulfate 0.8 0.6 28.6

SUS2-9 Sulfate 1,300 1,300 0

SUS2-17 Sulfate 155 150 3.3

SUS2-19 Sulfate 91.8 91 0.9

SUS2-1 Fluoride 7 6.1 13.7

SUS2-9 Fluoride 0.8 0.8 0

SUS2-17 Fluoride 3.5 3.5 0

SUS2-19 Fluoride 0.4 0.5 22.2

SUS2-1 Silica 6.1 6.1 0

SUS2-9 Silica 6.6 6.6 0

SUS2-17 Silica 6.6 7 5.9

SUS2-19 Silica 9.9 9.8 1.0

Appendix 2-2. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from lower 

Tertiary aquifers

[<, less than; E, estimated concentration; NC, not calculated]
92 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Trace elements, in micrograms per liter unless noted otherwise

SUS2-1 Aluminum <1 1 NC

SUS2-9 Aluminum 1 4 120.0

SUS2-17 Aluminum 1 <1 NC

SUS2-19 Aluminum <1 <1 NC

SUS2-1 Arsenic <0.2 <0.2 NC

SUS2-9 Arsenic <1.8 1.3 NC

SUS2-17 Arsenic 2.2 2.2 0

SUS2-19 Arsenic E0.9 1.1 20

SUS2-1 Barium 56.8 56.9 <1

SUS2-9 Barium 3.9 3.4 13.7

SUS2-17 Barium 13.9 17.8 24.6

SUS2-19 Barium 45.8 44.7 2.4

SUS2-1 Boron 150 155 3.3

SUS2-9 Boron 265 233 12.9

SUS2-17 Boron 116 135 15.1

SUS2-19 Boron 153 165 7.5

SUS2-1 Bromide 0.03 0.03 0

SUS2-9 Bromide 0.15 0.15 0

SUS2-17 Bromide 0.11 0.09 20

SUS2-19 Bromide 0.05 0.04 22.2

SUS2-1 Chromium <0.8 <0.8 NC

SUS2-9 Chromium <1 <0.8 NC

SUS2-17 Chromium <0.8 <0.8 NC

SUS2-19 Chromium E0.6 E0.5 18.2

SUS2-1 Cobalt E0.01 0.01 0

SUS2-9 Cobalt <2 <1 NC

SUS2-17 Cobalt <1 <1 NC

SUS2-19 Cobalt <1 <1 NC

SUS2-1 Copper E0.1 E0.2 66.7

SUS2-9 Copper 4.8 9.9 69.4

SUS2-17 Copper <1 <1 NC

SUS2-19 Copper 3.2 3.3 3.1

SUS2-1 Iron 10 10 0

SUS2-9 Iron E20 E20 0

SUS2-17 Iron <10 <10 NC

SUS2-19 Iron <10 M NC

SUS2-1 Lithium 11.3 11.6 2.6

SUS2-9 Lithium 23.5 23.4 <1

SUS2-17 Lithium 27.1 30.6 12.1

SUS2-19 Lithium 5.6 6.2 10.2

Appendix 2-2. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from lower 

Tertiary aquifers—Continued

Well number Constituent

Environmental 

sample

Replicate 

sample

Calculated 

relative-percent 

difference
Appendix 2 93

Trace elements, in micrograms per liter unless noted otherwise--Continued

SUS2-1 Manganese 1.7 1.6 6.1

SUS2-9 Manganese 29.3 29.9 2

SUS2-17 Manganese <1 <1 NC

SUS2-19 Manganese 14.6 14.9 2.0

SUS2-1 Molybdenum 1.3 1.3 0

SUS2-9 Molybdenum 2.7 3 10.5

SUS2-17 Molybdenum 6.3 6.8 7.6

SUS2-19 Molybdenum 3.4 1.8 61.5

SUS2-1 Nickel <0.06 0.07 NC

SUS2-9 Nickel <2 <1 NC

SUS2-17 Nickel <1 <1 NC

SUS2-19 Nickel 1.62 2.1 25.8

SUS2-1 Selenium 0.9 1.1 20.0

SUS2-9 Selenium 4.9 7.4 40.7

SUS2-17 Selenium E0.7 E0.5 33.3

SUS2-19 Selenium 1.3 1.5 14.3

SUS2-1 Strontium 86.3 86.9 <1

SUS2-9 Strontium 1,120 1,120 0

SUS2-17 Strontium 48.7 44.4 9.2

SUS2-19 Strontium 414 408 1.5

SUS2-1 Vanadium 7.4 8.1 9

SUS2-9 Vanadium <2 <1 NC

SUS2-17 Vanadium <1 <1 NC

SUS2-19 Vanadium 1.1 2.5 77.8

SUS2-1 Zinc <1 <1 NC

SUS2-9 Zinc 14 14 0

SUS2-17 Zinc 1 3 100.0

SUS2-19 Zinc 42 40 4.9

Nutrients, in milligrams per liter, and dissolved organic carbon

SUS2-1 Nitrite, as nitrogen <0.006 <0.006 NC

SUS2-9 Nitrite, as nitrogen <0.01 <0.01 NC

SUS2-17 Nitrite, as nitrogen 0.013 0.012 8.0

SUS2-19 Nitrite, as nitrogen 0.041 0.042 2.4

SUS2-1 Nitrite + nitrate, as nitrogen <0.047 <0.047 NC

SUS2-9 Nitrite + nitrate, as nitrogen 2.69 2.62 2.6

SUS2-17 Nitrite + nitrate, as nitrogen <0.05 <0.05 NC

SUS2-19 Nitrite + nitrate, as nitrogen 0.408 0.395 3.2

SUS2-1 Ammonia, as nitrogen 0.429 0.419 2.4

SUS2-9 Ammonia, as nitrogen 0.635 0.69 8.3

Appendix 2-2. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from lower 

Tertiary aquifers—Continued

Well number Constituent

Environmental 

sample

Replicate 

sample

Calculated 

relative-percent 

difference
94 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Nutrients, in milligrams per liter, and dissolved organic carbon--Continued

SUS2-17 Ammonia, as nitrogen 0.425 0.426 <1

SUS2-19 Ammonia, as nitrogen 0.334 0.342 2.4

SUS2-1 Ammonia + organic nitrogen, as nitrogen 0.48 0.5 4.1

SUS2-9 Ammonia + organic nitrogen, as nitrogen 0.84 0.88 4.7

SUS2-17 Ammonia + organic nitrogen, as nitrogen 0.43 0.46 6.7

SUS2-19 Ammonia + organic nitrogen, as nitrogen 0.43 0.42 2.4

SUS2-1 Phosphorus, as phosphorus 0.068 0.068 0

SUS2-9 Phosphorus, as phosphorus E0.003 E0.003 0

SUS2-17 Phosphorus, as phosphorus 0.02 <0.05 NC

SUS2-19 Phosphorus, as phosphorus 0.034 0.036 5.7

SUS2-1 Orthophosphate, as phosphorus 0.072 0.069 4.3

SUS2-9 Orthophosphate, as phosphorus <0.01 <0.01 NC

SUS2-17 Orthophosphate, as phosphorus 0.016 0.013 20.7

SUS2-19 Orthophosphate, as phosphorus 0.033 0.036 8.7

SUS2-1 Dissolved organic carbon, as carbon 2.4 2.4 0

SUS2-9 Dissolved organic carbon, as carbon 2.5 2.5 0

SUS2-17 Dissolved organic carbon, as carbon‘o 0.5 0.52 3.9

SUS2-19 Dissolved organic carbon, as carbon 2 2 0

Appendix 2-2. Replicate data for major ions, trace elements, nutrients, and dissolved organic carbon, samples from lower 

Tertiary aquifers—Continued

Well number Constituent

Environmental 

sample

Replicate 

sample

Calculated 

relative-percent 

difference
Appendix 2-3. Concentrations and calculated relative-percent differences of pesticides detected in replicate samples from the Quaternary aquifers[Values in italics are from a method still in research phase. USGS, U.S. Geological Survey; μg/L, micrograms per liter; <, less than; E, estimated concentration; NC, not calculatticide compound detected in only one sample, so relative-percent difference could not be calculated. Only pesticides with detections in wells with replicate samples are included lighted in table 5 in the text that does not appear in this table was not detected in replicate samples from the Quaternary aquifers]

Well 

number

USGS siteidentification 

number Date

Atrazine 

(μg/L)

Bentazon 

(μg/L)

Deethylatrazine 

(μg/L)

Deethyl, 

deisopropylatrazine 

(μg/L)

Dinoseb 

(μg/L)

Hydroxyatrazine 

(μg/L)

Picloram 

(μg/L)

Prometon 

(μg/L)

Simazin

(μg/L)

SUS1-7 451033108575401 11-02-99 <0.001 E0.0036 <0.002 <0.0599 <0.0429 <0.1927 <0.0712 <0.018 <0.005 

451033108575401 11-02-99 <.001 E.0065 <.002 <.0599 <.0429 <.1927 <.0712 <.018 <.005 

Relative-percent difference NC 57.43 NC NC NC NC NC NC NC 

SUS1-14 442354108255801 01-11-00 E.00265 <.0193 E.00362 <.0599 E.0012 <.1927 <.0712 <.018 <.005 

442354108255801 01-11-00 E.0028 <.0193 E.0038 <.0599 E.0014 <.1927 <.0712 <.018 <.005 

Relative-percent difference 5.5 NC 4.9 NC 15.4 NC NC NC NC 

SUS1-18 443023108233201 10-20-99 .0051 E.004 E.00344 E.0041 E.0016 E.0091 <.0712 .0301 <.005 

443023108233201 10-20-99 .00528 <.0193 E.00356 <.0599 <.0429 <.1927 <.0712 .0298 <.005 

Relative-percent difference 3.5 DD 3.4 DD DD DD NC 1.0% NC 

SUS1-25 440054107581401 10-06-99 <.005 <.0193 E.00421 <.0599 <.0429 <.1927 E.0457 .0509 .005

440054107581401 10-06-99 <.005 <.0193 E.0041 <.0599 <.0429 <.1927 <.0712 .0517 .005

Relative-percent difference NC NC 2.7 NC NC NC DD 1.6 .56 
96 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Appendix 2-4. Concentrations and calculated relative-percent differences of volatile organic compounds (VOCs) detected in 

replicate samples using unrounded data, Quaternary aquifers

[USGS, U.S. Geological Survey; μg/L, micrograms per liter; <, less than; NC, not calculated; DD, detection difference, pesticide compound detected in only 

one sample, so relative-percent difference could not be calculated; E, estimated concentration. Only compounds with detections in wells with replicate samples are included in table]

Well 

number

USGS siteidentification 

number Date

Benzene 

(μg/L)

Carbon 

disulfide 

(μg/L)

1,2-Dimethylbenzene 

(μg/L)

1,3- & 1,4-

Dimethylbenzene 

(μg/L)

Ethenylbenzene 

(μg/L)

Ethylbenzene 

(μg/L)

SUS1-25 440054107581401 10-06-99 <0.035 <0.07 <0.038 <0.06 <0.042 <0.03

440054107581401 10-06-99 <.035 <.07 <.038 <.06 <.042 <.03

Relative-percent difference NC NC NC NC NC NC

SUS1-14 442354108255801 01-11-00 <.035 <.07 <.038 <.06 <.042 <.03

442354108255801 01-11-00 <.035 <.07 <.038 <.06 <.042 <.03

Relative-percent difference NC NC NC NC NC NC

SUS1-18 443023108233201 10-20-99 <.035 <.07 <.038 <.06 <.042 <.03

443023108233201 10-20-99 <.035 <.07 <.038 <.06 <.042 <.03

Relative-percent difference NC NC NC NC NC NC

SUS1-7 451033108575401 11-02-99 E.07473 E.03294 E.02078 E.02692 <.042 E.03959

451033108575401 11-02-99 E.07249 E.03245 E.02325 E.02594 E.002972 E.0394

Relative-percent difference 3.0 1.5 11.2 3.7 DD .5 

Appendix 2-4. Concentrations and calculated relative-percent differences of volatile organic compounds (VOCs) detected in 

replicate samples using unrounded data, Quaternary aquifers--Continued

Well 

number

USGS siteidentification 

number

2-Ethyltoluene 

(μg/L)

Methylbenzene 

(μg/L)

(1-Methylethyl) 

benzene 

(μg/L)

n-Propylbenzene 

(μg/L)

Tetrachloroethene 

(μg/L)

Trichloromethane 

(μg/L)

1,2,4-Trimethylbenzene 

(μg/L)

SUS1-25 440054107581401 <0.06 <0.05 <0.032 <0.042 <0.1 <0.052 0.5381

440054107581401 <.06 <.05 <.032 <.042 <.1 <.052 E.08474 

Relative-percent difference NC NC NC NC NC NC 145.6 

SUS1-14 442354108255801 <.06 <.05 <.032 <.042 <.1 <.052 <.056

442354108255801 <.06 <.05 <.032 <.042 <.1 <.052 <.056

Relative-percent difference NC NC NC NC NC NC NC

SUS1-18 443023108233201 <.06 <.05 <.032 <.042 E.005666 E.01348 .1952

443023108233201 <.06 <.05 <.032 <.042 E.005035 E.01549 <.056

Relative-percent difference NC NC NC NC 11.8 13.9 DD

SUS1-7 451033108575401 E.006433 E.08112 E.004672 E.008902 <.1 <.052 .1407

451033108575401 E.006692 E.08538 E.005302 E.008204 <.1 <.052 E.01601 

Relative-percent difference 4.0 5.1 12.6 8.2 NC NC 159.1 
Appendix 2 97

Appendix 2-5. Concentrations and calculated relative-percent differences of volatile organic compounds (VOCs) detected 

in replicate samples from the lower Tertiary aquifers 

[USGS, U.S. Geological Survey; μg/L, micrograms per liter; <, less than; NC, not calculated; DD, detection difference, pesticide compound detected in only one sample, so relative-percent difference could not be calculated; E, estimated concentration. Only compounds with detections in 

wells with replicate samples are included in table.]

Well number

USGS 

site-identification 

number

Sample 

month/day/

year Sample time

Carbon 

disulfide 

(μg/L)

Chloromethane 

(μg/L)

1,2,4-Trimethylbenzene 

(μg/L)

SUS2-19 441220108513301 09/20/00 1100 E0.01168 E0.03662 E0.07423 

441220108513301 09/20/00 1101 E.01046 E.036 E.2734 

Relative-percent difference 11.02 1.71 114.59 

SUS2-17 442258108260301 07/10/00 1100 <.07 <.5 <.056

442258108260301 07/10/00 1101 <.07 <.5 <.056

Relative-percent difference NC NC NC

SUS2-9 444911108444501 08/02/00 1100 <.07 <.5 .1227

444911108444501 08/02/00 1101 <.07 <.5 E.03416 

Relative-percent difference NC NC 112.89 

SUS2-1 451608109223001 02/26/01 1300 <.07 <.25 E.04415 

451608109223001 02/26/01 1301 <.07 <.25 <.056

Relative-percent difference NC NC DD
Appendix 3-1. Pesticide field-matrix spike recoveries, samples from Quaternary aquifers. All samples analyzed using C-18 solid-phase 

capillary-column gas spectrometry (Zaugg and others, 1995).

Acetochlor

Alachlor

Atrazine

Azinphos-methyl

Benfluralin

Butylate

Carbaryl

Carbofuran

Chlorpyrifos

Cyanazine

DCPA

p,p'-DDE

Deethylatrazine

Diazinon

2,6-Diethylaniline

Disulfoton

EPTC

Ethalfluralin

Ethoprop

Fonofos

Alpha-HCH

Gamma-HCH (Lindane)

Linuron

Malathion

Methyl parathion

Metolachlor

Metribuzin (Sencor)

Molinate

Napropamide

Parathion

Pebulate

Pendimethalin

cis-Permethrin

Phorate

Prometon

Pronamide

Propachlor

Propanil

Propargite

Simazine

Tebuthiuron

Terbacil

Dieldrin

0

20406080

100120140160180200

SPIKE RECOVERY, IN PERCENT

PESTICIDE COMPOUND

EXPLANATION

Field-matrix spike recovery

Field-matrix spike recovery (estimated concentration)

Median recovery determined during method 

 development (Zaugg and others, 1995)

Median recovery estimated using median

concentrations determined during method 

 development (Zaugg and others, 1995)
Appendix 3-2. Pesticide field-matrix spike recoveries, samples from Quaternary aquifers. All samples analyzed using graphitized casolid-phase extraction and high-performance liquid chromatography/mass spectrometry (Furlong and others, 2001).

Acifluorfen

Aldicarb

Aldicarb sulfone

Aldicarb sulfoxide

Bendiocarb

Benomyl

Bensulfuron, methyl

Bentazon

Bromacil

Bromoxynil

Carbaryl

Carbofuran

Chloramben, methyl ester

Chlorimuron

Clopyralid

Cycloate

2,4-D

2,4-DB

2,4-D methyl ester

Dacthal, mono acid

Deethyldeisopropylatrazine

Deisopropylatrazine

Dicamba

Dichloroprop

Dinoseb

Diphenamid

Diuron

Fenuron

Flumetsulam

Fluometuron

Hydroxyatrazine

3-Hydroxycarbofuran

Imazaquin

Imazethapyr

Imidacloprid

3-Ketocarbofuran

Linuron

MCPA

MCPB

Metalaxyl

Methiocarb

Methomyl

Methomyloxime

Metsulfuron

Neburon

Nicosulfuron

Norflurazon

Oryzalin

Oxamyl

Oxamyloxime

Picloram

Propham

Propiconazole

Propoxur

Siduron

Sulfometruronmethyl

Chlorothalonil

0

50

100150200250300

SPIKE RECOVERY, IN PERCENT

PESTICIDE COMPOUND

EXPLANATION

(2)

(2)

Field-matrix spike recovery

Field-matrix spike recovery (estimated concentration).

Median recovery of laboratory samples spiked

 during 1999

Median recovery of laboratory samples spiked

 during 1999 (estimated concentration)

Number in parentheses next to symbol is number of

 samples
Appendix 3-3. Pesticide field-matrix spike recoveries, samples from lower Tertiary aquifers. All samples analyzed using C-18 solid-phase extraction and capillary-column gas chromatography/mass spectrometry (Zaugg and others, 1995).

Acetochlor

Alachlor

Atrazine

Azinphos-methyl

Benfluralin

Butylate

Carbaryl

Carbofuran

Chlorpyrifos

Cyanazine

DCPA

p,p' -DDE

Deethylatrazine

Diazinon

2,6-Diethylaniline

Disulfoton

EPTC

Ethalfluralin

Ethoprop

Fonofos

Alpha BHC

Gamma-HCH (Lindane)

Linuron

Malathion

Methyl parathion

Metolachlor

Metribuzin (Sencor)

Molinate

Napropamide

Parathion

Pebulate

Pendimethalin

cis-Permethrin

Phorate

Prometon

Pronamide

Propachlor

Propanil

Propargite

Simazine

Tebuthiuron

Terbacil

Terbufos

Terbuthylazine

Thiobencarb

Dieldrin

0

50

100150200250

SPIKE RECOVERY, IN PERCENT

PESTICIDE COMPOUND

EXPLANATION

Field-matrix spike recovery

Field-matrix spike recovery (estimated concentration

Median recovery determined during method

 development (Zaugg and others, 1995)

Median recovery using estimated median concen-

 tration determined during method development

 (Zaugg and others, 1995)
Appendix 3-4. Pesticide field-matrix spike recoveries, samples from lower Tertiary aquifers. All samples analyzed using graphitized cbased solid-phase extraction and high-performance liquid chromatography/mass spectrometry (Furlong and others, 2001). 

0

50

100150200250

SPIKE RECOVERY, IN PERCENT

Acifluorfen

Aldicarb

Aldicarb sulfone

Aldicarb sulfoxide

Bendiocarb

Benomyl

Bensulfuron, methyl

Bentazon

Bromacil

Bromoxynil

Carbaryl

Carbofuran

Chloramben, methyl ester

Chlorimuron

Clopyralid

Cycloate

2,4-D

2,4-DB

2,4-D methyl ester

Dacthal, mono acid

Deethyldeisopropylatrazine

Deisopropylatrazine

Dicamba

Dichloroprop

Dinoseb

Diphenamid

Diuron

Fenuron

Flumetsulam

Fluometuron

Hydroxyatrazine

3-Hydroxycarbofuran

Imazaquin

Imazethapyr

Imidacloprid

3-Ketocarbofuran

Linuron

MCPA

MCPB

Metalaxyl

Methiocarb

Methomyl

Methomyloxime

Metsulfuron

Neburon

Nicosulfuron

Norflurazon

Oryzalin

Oxamyl

Oxamyloxime

Picloram

Propham

Propiconazole

Propoxur

Siduron

Chlorothalonil

PESTICIDE COMPOUND

EXPLANATION

Field-matrix spike recovery

Field-matrix spike recovery (estimated concentration)

Median recovery of laboratory samples spiked

 during 1999

Median recovery of laboratory samples spiked

 during 1999 (estimated concentration)
Appendix 3-5. Volatile organic compound (VOC) field-matrix spike recoveries, samples from Quaternary aquifers.

1-Chloro-2-methylbenzene

1-Chloro-4-methylbenzene

Acetone

(2)

Benzene

Bromobenzene

Bromochloromethane

Bromodichloromethane

Bromoethene

Bromomethane

(2)

2-Butanone

n-Butylbenzene

Carbon disulfide

Chlorobenzene

Chloroethane

(2)

Chloroethene

Chloromethane

3-Chloro-1-propene

Dibromochloromethane 1,2-Dibromo-3-chloropropane

1,2-Dibromoethane

Dibromomethane

1,2-Dichlorobenzene

1,3-Dichlorobenzene

1,4-Dichlorobenzene

trans-1,4-Dichloro-2-butene

Dichlorodifluoromethane 1,1-Dichloroethane

1,2-Dichloroethane

Dichloromethane 1,2-Dichloropropane

1,3-Dichloropropane

2,2-Dichloropropane

1,1-Dichloropropene

cis-1,3-Dichloropropene trans-1,3-Dichloropropene

Diethyl ether

Diisopropyl ether

1,2-Dimethylbenzene

1,3- & 1,4-Dimethylbenzene

(1,1-Dimethylethyl)benzene

Ethenylbenzene

Ethylbenzene

Ethyl methacrylate

Ethyl tert-butyl ether

2-Ethyltoluene

1,1,2,3,4,4-Hexachloro-1,3-butadiene

1,1,1,2,2,2-Hexachloroethane

2-Hexanone

Iodomethane

1-Isopropyl-4-methylbenzene

Methyl acrylonitrile

Methylbenzene

Methyl methacrylate

4-Methyl-2-pentanone

Methyl-2-propenoate

(1-Methylpropyl)benzene

Methyl tert-butyl ether

Naphthalene

2-Propenenitrile

n-Propylbenzene

1,1,1,2-Tetrachloroethane

1,1,2,2-Tetrachloroethane

Tetrachloromethane Tetrahydrofuran

1,2,3,4-Tetramethylbenzene

1,2,3,5-Tetramethylbenzene

Tribromomethane 1,2,3-Trichlorobenzene

1,2,4-Trichlorobenzene

1,1,1-Trichloromethane

1,1,2-Trichloromethane

tert-Amyl methyl ether

1,1-Dichloroethene

cis-1,2-Dichloroethene

trans-1,2-Dichloroethene

(1-Methylethyl)benzene

Tetrachloroethene

0

20406080

100120140160180

SPIKE RECOVERY, IN PERCENT

EXPLANATION

Field-matrix spike recovery

Field-matrix spike recovery (estimated concentration)

Median laboratory recovery for sample set

Number in parentheses next to symbol is number of

 samples

VOLATILE ORGANIC COMPOUND (VOC)

(2)
Appendix 3-6. Volatile organic compound (VOC) field-matrix spike recoveries, samples from lower Tertiary aquifers.

3-Chloro-1-propene

Acetone tert-Amyl methyl ether

Benzene

Bromoethene

Bromodichloromethane

Bromochloromethane

Bromobenzene

Bromomethane

2-Butanone

n-Butylbenzene

Chloroethane

Chlorobenzene

Carbon disulfide

Chloroethene

Chloromethane

1-Chloro-2-methylbenzene

1-Chloro-4-methylbenzene

1,2-Dibromo-3-chloropropane Dibromochloromethane

1,2-Dibromoethane

Dibromomethane 1,2-Dichlorobenzene

1,3-Dichlorobenzene

1,4-Dichlorobenzene

trans-1,4-Dichloro-2-butene

Dichlorodifluoromethane 1,1-Dichloroethane

1,2-Dichloroethane

1,1-Dichloroethene

cis-1,2-Dichloroethene

trans-1,2-Dichloroethene

Dichloromethane 1,2-Dichloropropane

1,3-Dichloropropane

2,2-Dichloropropane

1,1-Dichloropropene

cis-1,3-Dichloropropene

trans-1,3-Dichloropropene

Diisopropyl ether

Diethyl ether

1,2-Dimethylbenzene

1,3- & 1,4-Dimethylbenzene

(1,1-Dimethyl)benzene

Ethenylbenzene

Ethylbenzene

Ethyl methacrylate

Ethyl -butyl ether tert

2-Ethyltoluene

1,1,2,3,4,4-Hexachloro-1,3-butadiene

1,1,1,2,2,2-Hexachloroethane

2-Hexanone

Iodomethane

1-Isopropyl-4-methylbenzene

Methyl acrylonitrile

Methylbenzene

(1-Methylethyl)benzene

Methyl methacrylate

4-Methyl-2-pentanone

Methyl-2-propenoate

(1-Methylpropyl)benzene

Methyl tert-butyl ether

Naphthalene

2-Propenenitrile n-Propylbenzene

1,1,1,2-Tetrachloroethane

1,1,2,2-Tetrachloroethane

Tetrachloroethene

Tetrachloromethane Tetrahydrofuran

1,2,3,4-Tetramethylbenzene

(2)

1,2,3,5-Tetramethylbenzene

Tribromomethane 1,2,3-Trichlorobenzene

1,2,4-Trichlorobenzene

1,1,1-Trichloroethane

112Tihlth

0

20406080

100120140160

SPIKE RECOVERY, IN PERCENT

EXPLANATION

Field-matrix spike recovery

Field-matrix spike recovery (estimated co

Median laboratory recovery for sample se

Number in parentheses next to symbol is 

 samples

VOLATILE ORGANIC COMPOUND (VOC)

(2)
104 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Appendix 4-1. Analyses for physical characteristics, samples from Quaternary aquifers

[USGS, U.S. Geological Survey; NTU, nephelometric turbidity units; mg/L, milligrams per liter; number below the compound is the data parameter code, 

which is a 5-digit number used in the USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent 

or property]

Well number

USGS siteidentification number

Sample date 

(month/day/

year)

Sample time 

(24 hour)

Water 

temperature 

degrees 

(Celsius) 

(00010)

pH, 

laboratory 

(standard 

units )

(00403)

pH, field 

(standard 

units) 

(00400)

Turbidity 

(NTU) 

(61028)

Dissolved 

oxygen 

(mg/L) 

(00300)

SUS1-1 440629109092401 10/19/99 1100 10 7.2 7.1 <0.1 0.4

SUS1-2 442618109130202 03/29/00 1100 13.5 7.6 7.4 710 3.9

SUS1-3 444500109013101 10/13/99 1100 12.5 7.6 7.6 1 6.9

SUS1-4 445613109081401 10/13/99 1700 15.5 7.5 7.3 .4 2.7

SUS1-5 451411109134301 03/30/00 1000 9 7.3 7.1 3 5.5

SUS1-6 453101108512801 11/01/99 1200 11 7.3 7.1 2.7 .7

SUS1-7 451033108575401 11/02/99 1300 11.5 7.6 7.1 1.1 5.3

SUS1-8 444639108452601 12/13/99 1300 9.5 7.6 7.6 .2 .9

SUS1-9 444126108513401 10/12/99 1500 11.5 7.4 7.3 .9 5.4

SUS1-10 441556108473201 12/15/99 1100 9 7.5 7.4 2.9 .5

SUS1-11 440213108583501 10/18/99 1100 9.5 7.1 7 1.8 .7

SUS1-12 434334108351101 12/16/99 1000 8.5 7.4 7.1 3.1 .6

SUS1-13 440027108264501 03/28/00 1100 12.5 7.6 7.6 4 6.7

SUS1-14 442354108255801 01/11/00 1100 8 7.6 7.7 .7 .7

SUS1-16 444424108354001 10/14/99 1200 15 7.7 7.5 .6 .8

SUS1-17 445014108224301 11/03/99 1100 13.5 7.2 7.1 .9 .4

SUS1-18 443023108233201 10/20/99 1100 12 7.6 7.3 .1 4

SUS1-19 442258108141201 01/12/00 1100 8.2 7.4 7.2 2.2 .7

SUS1-22 433519108125201 10/05/99 1000 17 6.9 6.9 1.2 .6

SUS1-24 435010107214701 01/10/00 1100 8.8 7.3 7.4 1.3 .5

SUS1-25 440054107581401 10/06/99 1000 12.5 7.5 7.3 1.2 .3

SUS1-27 440952107405101 01/13/00 1100 8.5 7.6 7.4 1.8 1.6

SUS1-28 441554107560001 10/07/99 1000 13 7.2 7.1 2.4 .5

SUS1-29 441821108014701 10/21/99 1000 10 7.1 7 .8 .5

SUS1-30 444719108050501 11/04/99 1100 14 7.6 7.2 30 4.7
Appendix 4 105

Appendix 4-2. Analyses for physical characteristics, samples from lower Tertiary aquifers

[USGS, U.S. Geological Survey; NTU, nephelometric turbidity units; mg/L, milligrams per liter; number below the compound is the data parameter code, 

which is a 5-digit number used in the USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent 

or property; NR, value not reported because of water cascading down well casing]

Well number

USGS siteidentification number

Sample date 

(month/day/

year)

Sample time 

(24 hour)

Water 

temperature 

degrees 

(Celsius) 

(00100)

pH, 

laboratory 

(standard 

units)

(00403)

pH, field 

(standard 

units)

(00400)

Turbidity 

(NTU) 

(61028)

Dissolved 

oxygen 

(mg/L)

(00300)

SUS2-1 451608109223001 02/26/01 1300 8 8.8 9 0.3 0.1

SUS2-2 452239109191101 08/08/00 1100 11 7.4 7.3 .7 .2

SUS2-3 452326109065301 08/07/00 1200 12 7.6 7.4 .2 8

SUS2-4 451407109133901 08/09/00 1100 13 8.9 8.9 .3 .1

SUS2-5 450210109030601 02/28/01 1700 11.5 8.1 8.1 30 .3

SUS2-6 450658109010401 02/27/01 1600 12.5 7.7 7.5 45 NR

SUS2-7 445246109084101 07/31/00 1300 14 9.1 9.3 .3 .1

SUS2-8 444509109010901 08/01/00 1100 11.3 7.8 8.1 .2 2.1

SUS2-9 444911108444501 08/02/00 1100 13 7.8 7.7 .5 .4

SUS2-10 444107108550201 08/03/00 1000 13 8.5 8.6 .1 .2

SUS2-11 444326108424501 05/15/01 1600 11 7.3 7.3 1 2.5

SUS2-12 444417108381001 03/01/01 1300 11 7.3 7.2 1.5 1.7

SUS2-13 443426108593501 06/06/01 1200 11 7.5 7.4 .9 NR

SUS2-14 442639108220201 10/19/00 1300 11.2 8.2 8.2 .3 .2

SUS2-15 442933108211201 09/18/00 1100 14.5 8.3 8.3 2.9 6.2

SUS2-16 442239108362001 09/20/00 1600 12 8.2 8.2 1.5 .3

SUS2-17 442258108260301 07/10/00 1100 13.1 8.6 8.7 .3 .1

SUS2-18 442348108082301 07/11/00 1100 12.6 6.8 6.7 .8 NR

SUS2-19 441220108513301 09/20/00 1100 9 7.6 7.3 2.6 1.3

SUS2-20 441639108195501 10/24/00 1600 11 8.4 9 160 .1

SUS2-22 440943108455001 10/25/00 1200 11.5 7 7.1 .6 1.7

SUS2-23 440306108160601 10/18/00 1100 13 8.3 8.3 .6 .3

SUS2-24 441046107562201 07/12/00 1100 12.7 7.7 8 .7 .1

SUS2-25 440008108272601 10/26/00 1000 10 8.1 8.4 .4 .2

SUS2-26 435735108074101 09/21/00 1100 11 8.5 8.6 3.5 1.9

SUS2-27 440207107553001 09/19/00 1300 13 7.5 7.4 .6 5.4

SUS2-28 435143108090501 06/06/00 1000 13 8.4 8.5 .2 .1

SUS2-29 435556107580701 07/13/00 1100 14.2 7.7 8.1 .5 .1

SUS2-30 435115107454801 10/2300 1300 12 8 8.2 3.8 1.9
Appendix 5-1. Analyses for major ions and related water-quality characteristics, samples from Quaternary aquifers [USGS, U.S. Geological Survey; mg/L, milligrams per liter; HCO3, bicarbonate; CaCO3, calcium carbonate; μS/cm, microsiemens per centimeter; number below the compo

which is a 5-digit number used in the USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; N

lem with measurement; E, estimated concentration] Well number USGS site- identification number Sample date (month/day/ year) Sample time (24 hour) Calcium, dissolved (mg/L) (00915) Magnesium, dissolved (mg/L) (00925) Sodium, dissolved (mg/L) (00930) Sodium, (percent) (00932) Sodium- adsorption ratio (SAR) (00931) Potassium, dissolved (mg/L) (00935) Bicarbonate, dissolved (mg/L as HCO3) (00453) 

SUS1-1 440629109092401 10/19/99 1100 52.1 16.8 49.5 35 2 1.38 271 SUS1-2 442618109130202 03/29/00 1100 69.3 15.8 43.9 28 1 3.38 325 SUS1-3 444500109013101 10/13/99 1100 57.5 42.6 76.1 34 2 3.2 417 SUS1-4 445613109081401 10/13/99 1700 67.4 19.3 14.4 11 .4 1.7 298 SUS1-5 451411109134301 03/30/00 1000 28.8 9.47 4.9 9 .2 1.78 143 SUS1-6 453101108512801 11/01/99 1200 125 58.4 90.9 26 2 3.87 447 SUS1-7 451033108575401 11/02/99 1300 75.5 30.2 122 45 3 5.62 392 SUS1-8 444639108452601 12/13/99 1300 48.1 21.7 212 68 6 2.8 386 SUS1-9 444126108513401 10/12/99 1500 70.2 16.3 50.1 31 1 2.01 319 SUS1-10 441556108473201 12/15/99 1100 256 176 2,430 79 29 9.23 1,670 SUS1-11 440213108583501 10/18/99 1100 35.7 13.4 21.2 24 .8 1.56 191 SUS1-12 434334108351101 12/16/99 1000 221 92.9 242 36 3 4.27 499 SUS1-13 440027108264501 03/28/00 1100 353 1,440 4,530 59 24 12.1 922 SUS1-14 442354108255801 01/11/00 1100 68.4 25 47.9 27 1 2.27 253 SUS1-16 444424108354001 10/14/99 1200 82.2 21.2 201 59 5 4.44 404 SUS1-17 445014108224301 11/03/99 1100 292 101 271 34 3 6.42 473 SUS1-18 443023108233201 10/20/99 1100 67.1 25.8 83.2 40 2 1.58 380 SUS1-19 442258108141201 01/12/00 1100 118 40.7 265 55 5 3.85 627 SUS1-22 433519108125201 10/05/99 1000 525 60.9 56.1 7 .6 9.64 440 SUS1-24 435010107214701 01/10/00 1100 198 71.8 229 39 4 4.3 319 SUS1-25 440054107581401 10/06/99 1000 93.6 24.1 202 56 5 5.31 415 SUS1-27 440952107405101 01/13/00 1100 219 77.8 231 37 3 6.45 366 SUS1-28 441554107560001 10/07/99 1000 288 166 816 56 9 4.76 781 SUS1-29 441821108014701 10/21/99 1000 245 61.6 269 40 4 6.61 488 SUS1-30 444719108050501 11/04/99 1100 113 49.7 221 49 4 3.96 319 
Appendix 5-1. Analyses for major ions and related water-quality characteristics, samples from Quaternary aquifers--Continued

Well 

number

USGS siteidentification 

number

Fluoride, 

dissolved 

(mg/L) 

(00950)

Silica, 

dissolved 

(mg/L) 

(00955)

Dissolved 

solids, residue 

on evaporation 

at 180 degrees 

Celsius 

(mg/L)

(70300)

Dissolved 

solids, 

calculated 

(mg/L) 

(70301)

Alkalinity, 

dissolved, fixed 

endpoint method 

(laboratory 

analysis) 

(mg/L as CaCO3)

(29801)

Alkalinity, 

dissolved, 

incremental 

titration method 

(field analysis) 

(mg/L as CaCO3)

(39086)

Hardness 

(mg/L as 

CaCO3)

(00900)

Spe

conduc

labor

measu

(μS/cm 

deg

Cels

(900

SUS1-1 440629109092401 0.4 34 320 337 231 222 200 5SUS1-2 442618109130202 .2 22.6 393 386 277 266 240 6SUS1-3 444500109013101 .5 12.7 572 570 341 342 320 8SUS1-4 445613109081401 <.1 13.6 306 305 252 244 250 5SUS1-5 451411109134301 .1 11.7 128 135 120 117 110 2SUS1-6 453101108512801 .2 15.1 898 875 NR 367 550 1,2SUS1-7 451033108575401 .4 13.3 682 675 360 321 310 1,0SUS1-8 444639108452601 1.1 22.4 816 832 328 316 210 1,2SUS1-9 444126108513401 .4 25.5 438 424 262 262 240 6SUS1-10 441556108473201 4.7 19.2 9,340 9,120 1,440 1,370 1,400 11,1SUS1-11 440213108583501 .3 22.3 214 219 161 157 140 3SUS1-12 434334108351101 .3 26.4 2,000 1,830 440 409 930 2,4SUS1-13 440027108264501 .7 E18.3 24,300 21,800 780 756 6,800 20,5SUS1-14 442354108255801 .1 15.2 479 453 220 207 270 7SUS1-16 444424108354001 .4 14.6 956 945 342 331 290 1,4SUS1-17 445014108224301 .6 26.8 2,450 2,320 389 388 1,100 2,8SUS1-18 443023108233201 2.6 37.5 597 575 324 312 270 9SUS1-19 442258108141201 .5 20 1,350 1,300 543 514 460 1,8SUS1-22 433519108125201 1.3 20.2 2,300 2,190 363 361 1,600 2,5SUS1-24 435010107214701 .4 14.5 1,870 1,720 279 262 790 2,2SUS1-25 440054107581401 .7 17.7 1,030 1,010 344 340 330 1,5SUS1-27 440952107405101 .4 15.3 1,920 1,810 312 300 870 2,3SUS1-28 441554107560001 .3 21.8 4,260 4,100 648 640 1,400 4,9SUS1-29 441821108014701 1.1 15.9 1,900 1,890 414 400 860 2,4SUS1-30 444719108050501 .3 11.2 1,360 1,280 264 261 490 5
Appendix 5-2. Analyses for major ions and related water-quality characteristics, samples from lower Tertiary aquifers [USGS, U.S. Geological Survey; mg/L, milligrams per liter; HCO3, bicarbonate; CaCO3, calcium carbonate; μS/cm, microsiemens per centimeter; number below the compo

which is a 5-digit number used in the USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; 

Well number USGS site- identification number Sample date (month/day/ year) Sample time (24 hour) Calcium, dissolved (mg/L) (00915) Magnesium, dissolved (mg/L) (00925) Sodium, dissolved (mg/L) (00930) Sodium (percent) (00932) Sodium- adsorption ratio (SAR) (00931) Potassium, dissolved (mg/L) (00935) Bicarbonate, dissolved (mg/L as HCO3) (00453) 

SUS2-1 451608109223001 02/26/01 1300 1.18 0.326 276 99 58 0.91 761 SUS2-2 452239109191101 08/08/00 1100 70 27.6 267 67 7 .87 630 SUS2-3 452326109065301 08/07/00 1200 87.3 32.4 12.1 7 .3 1.56 386 SUS2-4 451407109133901 08/09/00 1100 1.14 .486 198 99 39 1.16 463 SUS2-5 450210109030601 02/28/01 1700 22.4 10.6 1190 96 52 6.04 1,070 SUS2-6 450658109010401 02/27/01 1600 35.6 36.6 1490 93 42 7.22 1,060 SUS2-7 445246109084101 07/31/00 1300 .96 .144 136 99 34 .51 257 SUS2-8 444509109010901 08/01/00 1100 29.6 20.8 108 59 4 1.98 258 SUS2-9 444911108444501 08/02/00 1100 34.1 16.6 736 91 26 5.35 451 SUS2-10 444107108550201 08/03/00 1000 7.36 1.19 444 97 40 1.34 261 SUS2-11 444326108424501 05/15/01 1600 218 79.8 1,440 78 21 7.54 585 SUS2-12 444417108381001 03/01/01 1300 109 51.5 197 47 4 5.06 511 SUS2-13 443426108593501 06/06/01 1200 100 42 255 56 5 6.08 236 SUS2-14 442639108220201 10/19/00 1300 14.4 3.9 455 95 27 2.15 262 SUS2-15 442933108211201 09/18/00 1100 6.5 2.74 261 95 22 2.24 463 SUS2-16 442239108362001 09/20/00 1600 8.5 2.28 525 97 41 2.61 505 SUS2-17 442258108260301 07/10/00 1100 2.57 .688 243 98 35 1 397 SUS2-18 442348108082301 07/11/00 1100 407 214 528 37 5 13.6 300 SUS2-19 441220108513301 09/20/00 1100 30.5 13.7 135 68 5 3.27 346 SUS2-20 441639108195501 10/24/00 1600 2.22 .6 231 98 35 1.01 489 SUS2-22 440943108455001 10/25/00 1200 166 57.6 11.4 4 .2 4.43 288 SUS2-23 440306108160601 10/18/00 1100 4.36 .857 340 98 39 1.44 488 SUS2-24 441046107562201 07/12/00 1100 104 24.9 670 80 15 6.69 186 SUS2-25 440008108272601 10/26/00 1000 7.19 1.68 544 98 47 2.47 557 SUS2-26 435735108074101 09/21/00 1100 3.55 .779 268 98 34 1.58 483 SUS2-27 440207107553001 09/19/00 1300 168 58.2 193 38 3 10.2 295 SUS2-28 435143108090501 06/06/00 1000 7.98 4.21 572 97 41 2.97 562 SUS2-29 435556107580701 07/13/00 1100 39.1 7.84 817 93 31 4.07 258 SUS2-30 435115107454801 10/23/00 1300 35.1 11.4 663 91 25 4.81 266 
Appendix 5-2. Analyses for major ions and related water-quality characteristics, samples from lower Tertiary aquifers--Continued

Well 

number

USGS siteidentification 

number

Fluoride, 

dissolved 

(mg/L) 

(00950)

Silica, 

dissolved 

(mg/L) 

(00955)

Dissolved 

solids, residue 

on evaporation 

at 180 degrees 

Celsius 

(mg/L)

(70300)

Dissolved 

solids, 

calculated 

(mg/L) 

(70301)

Alkalinity, 

dissolved, fixed 

endpoint method 

(laboratory 

analysis) 

(mg/L as CaCO3)

(29801)

Alkalinity, 

dissolved, 

incremental 

titration method 

(field analysis) 

(mg/L as CaCO3)

(39086)

Hardness 

(mg/L as 

CaCO3)

(00900)

Spe

conduc

labor

measu

(μS/cm 

deg

Cels

(900

SUS2-1 451608109223001 7 6.1 687 686 615 653 4 1,1SUS2-2 452239109191101 .5 8.8 1,080 1,010 576 518 290 1,6SUS2-3 452326109065301 .6 19.7 394 364 361 317 350 6SUS2-4 451407109133901 2.2 7.7 518 485 NM 380 5 8SUS2-5 450210109030601 1.6 7 3,650 3,710 678 874 100 5,2SUS2-6 450658109010401 1 6.5 4,820 4,850 793 870 240 6,5SUS2-7 445246109084101 2.4 7.9 352 337 256 239 3 6SUS2-8 444509109010901 .6 7.9 555 512 239 214 160 8SUS2-9 444911108444501 .8 6.6 2,400 2,360 426 370 150 3,0SUS2-10 444107108550201 1.7 7.8 1,340 1,290 251 222 24 2,0SUS2-11 444326108424501 .4 7.7 5,800 5,390 493 482 880 6,8SUS2-12 444417108381001 .6 10 1,200 1,190 353 419 490 1,6SUS2-13 443426108593501 .6 11.6 1,300 1,210 297 288 420 1,8SUS2-14 442639108220201 2.5 6.8 1,390 1,350 246 219 52 2,2SUS2-15 442933108211201 2 8.4 748 695 440 386 28 1,1SUS2-16 442239108362001 2.4 7 1,570 1,510 484 414 31 2,3SUS2-17 442258108260301 3.5 6.6 678 631 388 338 9 1,1SUS2-18 442348108082301 .4 7.4 4,580 4,140 265 246 1,900 4,6SUS2-19 441220108513301 .4 9.9 506 462 346 284 130 8SUS2-20 441639108195501 6.4 6.6 572 543 484 431 8 9SUS2-22 440943108455001 1.2 8.2 876 811 282 236 650 1,2SUS2-23 440306108160601 3.2 7.1 994 934 457 400 15 1,5SUS2-24 441046107562201 .9 6.6 2,370 2,500 128 186 360 3,4SUS2-25 440008108272601 .8 6.6 1,530 1,510 512 467 25 2,3SUS2-26 435735108074101 3.6 7 722 685 439 396 12 1,1SUS2-27 440207107553001 .9 24.1 1,510 1,370 277 242 660 2,0SUS2-28 435143108090501 2.1 6.9 1,620 1,590 513 474 38 2,5SUS2-29 435556107580701 1 6.8 2,650 2,640 167 214 130 3,7SUS2-30 435115107454801 1 6.2 2,200 2,160 255 222 140 3,0
Appendix 6-1. Analyses for trace elements, samples from Quaternary aquifers [USGS, U.S. Geological Survey; μg/L, micrograms per liter; mg/L, milligrams per liter; number below the compound is the data parameter code, which is a 5-digit number used 

system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than; E, estimated concentration; --, not analyzed; M, const

Well number USGS site- identification number Sample date (month/ day/year) Sample time (24 hour) Aluminum, dissolved (μg/L) (01106) Antimony, dissolved (μg/L) (01095) Arsenic, dissolved (μg/L) (01000) Barium, dissolved (μg/L) (01005) Beryllium, dissolved (μg/L) (01010) Boron, dissolved (μg/L) (01020) Bromide, dissolved (mg/L) (71870) Cadmium, dissolved (μg/L) (01025) Chrom

dissol

(μg/

(0103

SUS1-1 440629109092401 10/19/99 1100 2 <1 2.9 69.8 <1 -- 0.03 <1 <0.SUS1-2 442618109130202 03/29/00 1100 1 <1 3.7 92.2 <1 119 .01 <1 <1 SUS1-3 444500109013101 10/13/99 1100 <1 <1 <2 41.4 <1 -- .04 <1 E.SUS1-4 445613109081401 10/13/99 1700 2 <1 <2 210 <1 -- .02 <1 9.SUS1-5 451411109134301 03/30/00 1000 1 <1 <.9 82.3 <1 E8 <.01 <1 <1 SUS1-6 453101108512801 11/01/99 1200 2 <1 <2 47.7 <1 -- .02 <1 <.SUS1-7 451033108575401 11/02/99 1300 2 <1 <2 44 <1 -- .12 <1 1 SUS1-8 444639108452601 12/13/99 1300 2 <1 <2 6.9 <1 -- .05 <1 E.SUS1-9 444126108513401 10/12/99 1500 <1 <1 2.5 18.7 <1 -- .02 <1 E.SUS1-10 441556108473201 12/15/99 1100 <5 <5 2 64.1 <5 -- .61 <5 <4 SUS1-11 440213108583501 10/18/99 1100 2 <1 <2 44.1 <1 -- <.01 <1 <.SUS1-12 434334108351101 12/16/99 1000 <1 <1 <2 26.7 <1 -- .06 <1 <.SUS1-13 440027108264501 03/28/00 1100 2 <1 2.8 13.3 <1 235 .99 <1 3.SUS1-14 442354108255801 01/11/00 1100 <1 <1 E1.2 62.1 <1 -- .01 <1 <.SUS1-16 444424108354001 10/14/99 1200 2 <1 <2 23.3 <1 -- .08 <1 <.SUS1-17 445014108224301 11/03/99 1100 3 <1 <2 30.1 <1 -- .1 <1 <1 SUS1-18 443023108233201 10/20/99 1100 <1 <1 4.8 26 <1 -- .04 <1 1.SUS1-19 442258108141201 01/12/00 1100 2 <1 E1.1 26 <1 -- .05 <1 E.SUS1-22 433519108125201 10/05/99 1000 2 <1 <2 15.8 <1 -- .25 <1 <1 SUS1-24 435010107214701 01/10/00 1100 <1 <1 <2 17.5 <1 -- .09 <1 1.SUS1-25 440054107581401 10/06/99 1000 1 <1 E1.6 19.7 <1 -- .1 <1 <.SUS1-27 440952107405101 01/13/00 1100 <1 <1 <2 21 <1 -- .1 <1 1.SUS1-28 441554107560001 10/07/99 1000 2 <1 3.8 11.4 <1 -- .09 <1 <.SUS1-29 441821108014701 10/21/99 1000 1 <1 <2 15.3 <1 -- .12 <1 1.SUS1-30 444719108050501 11/04/99 1100 <1 <1 <2 21.1 <1 -- .05 <1 <1 
Appendix 6-1. Analyses for trace elements, samples from Quaternary aquifers--Continued

Well 

number

USGS siteidentification 

number

Iron, 

dissolved 

(μg/L)

(01046)

Lead, 

dissolved 

(μg/L) 

(01049)

Lithium, 

dissolved 

(μg/L)

(01130)

Manganese, 

dissolved 

(μg/L)

(01056)

Molybdenum, 

dissolved 

(μg/L)

(01060)

Nickel, 

dissolved 

(μg/L)

(01065)

Selenium, 

dissolved 

(μg/L)

(01145)

Silver, 

dissolved 

(μg/L)

(01075)

Strontium, 

dissolved

(μg/L)

(01080)

Thallium

dissolved 

(μg/L)

(01057)

SUS1-1 440629109092401 100 <1 -- 98.2 4.2 2.48 <2.4 <1 -- -- SUS1-2 442618109130202 <10 <1 14.8 42.5 9 5.86 2 <1 584 <.9 SUS1-3 444500109013101 <10 <1 -- <1 <1 2.06 E17 <1 -- -- SUS1-4 445613109081401 <10 <1 -- <1 <1 1.66 <2.4 <1 -- -- SUS1-5 451411109134301 <10 <1 3.7 65.7 1.4 2.04 <.7 <1 149 <.9 SUS1-6 453101108512801 590 <1 -- 1,890 3.5 2.42 <2.4 <1 -- -- SUS1-7 451033108575401 M <1 -- 147 6.5 5.79 2.7 <1 -- -- SUS1-8 444639108452601 <10 <1 -- 12.4 4.1 1.41 4.2 <1 -- -- SUS1-9 444126108513401 <10 <1 -- <1 2.5 1.46 E1.2 <1 -- -- SUS1-10 441556108473201 20 <5 -- 226 8.2 22.1 20.2 <5 -- -- SUS1-11 440213108583501 <10 <1 -- 116 2.3 2.68 <2.4 <1 -- -- SUS1-12 434334108351101 320 <1 -- 392 3.6 4.97 <2.4 <1 -- -- SUS1-13 440027108264501 40 <1 471 203 8.8 11 29.5 <1 11,700 <.9 SUS1-14 442354108255801 20 <1 -- 723 1.5 6.17 <2.4 <1 -- -- SUS1-16 444424108354001 100 <1 -- 142 3.6 2.37 <2.4 <1 -- -- SUS1-17 445014108224301 <10 <1 -- 7.6 2.5 3.43 10.8 <1 -- -- SUS1-18 443023108233201 <10 <1 -- <1 6 1.62 5.6 <1 -- -- SUS1-19 442258108141201 20 <1 -- 234 2.3 3.19 <2.4 <1 -- -- SUS1-22 433519108125201 <10 <1 -- 40.8 8.7 5.26 <2.4 <1 -- -- SUS1-24 435010107214701 <10 <1 -- 2,800 4.2 18.1 <2.4 <1 -- -- SUS1-25 440054107581401 1,210 <1 -- 1,350 2.5 1.72 <2.4 <1 -- -- SUS1-27 440952107405101 450 <1 -- 324 2.2 6.34 <2.4 <1 -- -- SUS1-28 441554107560001 6,710 <1 -- 3,800 1.3 6.01 <2.4 <1 -- -- SUS1-29 441821108014701 <30 <1 -- 904 2 4.79 4.3 <1 -- -- SUS1-30 444719108050501 140 <1 -- 656 2.8 3.62 <2.4 <1 -- -- 
Appendix 6-2. Analyses for trace elements, samples from lower Tertiary aquifers USGS, U.S. Geological Survey; μg/L, micrograms per liter; mg/L, milligrams per liter; number below the compound is the data parameter code, which is a 5-digit number used 

system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than; E, estimated concentration; M, constituent detected bu

Well number USGS site- identification number Sample date (month/ day/year) Sample time (24 hour) Aluminum, dissolved (μg/L) (01106) Antimony, dissolved (μg/L) (01095) Arsenic, dissolved (μg/L) (01000) Barium, dissolved (μg/L) (01005) Beryllium, dissolved (μg/L) (01010) Boron, dissolved (μg/L) (01020) Bromide, dissolved (mg/L) (71870) Cadmium, dissolved (μg/L) (01025) Chrom

disso

(μg/

(010

SUS2-1 451608109223001 02/26/01 1300 <1 <0.05 <0.2 56.8 <0.06 150 0.03 <0.04 <0SUS2-2 452239109191101 08/08/00 1100 <1 <1 <.9 33.5 <1 184 .06 <1 ESUS2-3 452326109065301 08/07/00 1200 5 <1 .9 113 <1 26 .02 <1 <SUS2-4 451407109133901 08/09/00 1100 7 <1 <.9 44 <1 273 .02 <1 <SUS2-5 450210109030601 02/28/01 1700 5 E.14 .7 13.6 <.06 429 1.21 <.11 1SUS2-6 450658109010401 02/27/01 1600 2 .76 1.1 9.4 <.06 332 .09 <.04 <SUS2-7 445246109084101 07/31/00 1300 4 <1 <.9 17 <1 216 .07 <1 <SUS2-8 444509109010901 08/01/00 1100 <1 <1 <.9 20.7 <1 88 .1 <1 <SUS2-9 444911108444501 08/02/00 1100 1 <2 <1.8 3.9 <2 265 .15 <2 <1 SUS2-10 444107108550201 08/03/00 1000 1 <1 <.9 9 <1 635 .11 <1 <SUS2-11 444326108424501 05/15/01 1600 <1 <.05 .7 5.1 <.06 198 .23 E.02 <SUS2-12 444417108381001 03/01/01 1300 <1 .12 .3 6.1 <.06 212 .06 E.03 <SUS2-13 443426108593501 06/06/01 1200 <1 <.05 3.1 9.6 <.06 403 .17 <.04 <SUS2-14 442639108220201 10/19/00 1300 <1 <.05 1.9 6.4 <.06 117 .64 .08 <SUS2-15 442933108211201 09/18/00 1100 <1 <1 3.4 6.8 <1 156 .06 <1 ESUS2-16 442239108362001 09/20/00 1600 1 <1 E.5 5.9 <1 278 .09 <1 <SUS2-17 442258108260301 07/10/00 1100 1 <1 2.2 13.9 <1 116 .11 <1 <SUS2-18 442348108082301 07/11/00 1100 22 <5 2.7 6.2 <5 122 .07 <5 <SUS2-19 441220108513301 09/20/00 1100 <1 <1 E.9 45.8 <1 153 .05 <1 ESUS2-20 441639108195501 10/24/00 1600 <1 <.05 E.1 87.6 <.06 141 .14 <.04 <SUS2-22 440943108455001 10/25/00 1200 <1 <.05 .8 8 E.04 40 .09 <.04 ESUS2-23 440306108160601 10/18/00 1100 <1 <.05 1 11.8 <.06 304 .2 <.04 ESUS2-24 441046107562201 07/12/00 1100 1 <1 1.4 13.2 <1 160 .37 <1 <SUS2-25 440008108272601 10/26/00 1000 1 <.05 .8 6.8 <.06 183 .17 .04 <SUS2-26 435735108074101 09/21/00 1100 1 <1 <.9 85.4 <1 122 .17 <1 ESUS2-27 440207107553001 09/19/00 1300 <1 6.3 7.4 21.9 <1 214 .11 9.36 1SUS2-28 435143108090501 06/06/00 1000 <3 <1 <.9 7.3 <1 292 .11 <1 <SUS2-29 435556107580701 07/13/00 1100 5 <1 1 8 <1 82 .43 <1 <1 SUS2-30 435115107454801 10/23/00 1300 <2 .1 .4 4.2 E.52 264 .2 <.07 <
Appendix 6-2. Analyses for trace elements, samples from lower Tertiary aquifers--Continued

Well 

number

USGS siteidentification 

number

Iron, 

dissolved(

(μg/L)

(01046)

Lead, 

dissolved 

(μg/L)

(01049)

Lithium, 

dissolved 

(μg/L)

(01130) 

Manganese, 

dissolved

(μg/L)

(01056)

Molybdenum, 

dissolved 

(μg/L)

(01060)

Nickel, 

dissolved 

(μg/L)

(01065)

Selenium, 

dissolved 

(μg/L)

(01145)

Silver, 

dissolved 

(μg/L)

(01075)

Strontium, 

dissolved 

(μg/L)

(01080)

Thallium

dissolve

(μg/L)

(01057)

SUS2-1 451608109223001 10 <0.08 11.3 1.7 1.3 <0.06 0.9 <1 86.3 0.05 SUS2-2 452239109191101 1,540 <1 20.2 177 1.6 <1 <.7 <1 639 <.9 SUS2-3 452326109065301 <10 <1 19.2 <1 <1 1.32 <.7 <1 826 <.9 SUS2-4 451407109133901 10 <1 23.6 1.9 <1 <1 <.7 <1 44.9 <.9 SUS2-5 450210109030601 E40 E.14 130 51.2 1.2 .95 6.2 <3 1,860 E.13 SUS2-6 450658109010401 110 .14 111 69.2 .9 2.5 3.2 <1 4,470 <.04 SUS2-7 445246109084101 <10 <1 6.5 <1 3.5 <1 <.7 <1 24.9 <.9 SUS2-8 444509109010901 <10 <1 20.1 <1 2.9 <1 1.3 <1 693 <.9 SUS2-9 444911108444501 E20 <2 23.5 29.3 2.7 <2 4.9 <2 1,120 <1.8 SUS2-10 444107108550201 <30 <1 20.8 6.5 5.6 <1 E.6 <1 234 <.9 SUS2-11 444326108424501 <50 .36 53.5 207 1.9 .12 3 <1 6,450 .04 SUS2-12 444417108381001 M .23 8.6 .5 1.9 <.06 3.4 <1 1,250 E.03 SUS2-13 443426108593501 450 .1 56.3 109 2.4 <.06 .5 <1 1,180 E.03 SUS2-14 442639108220201 <30 E.07 70.4 5.1 39.5 .25 7.8 <1 293 <.04 SUS2-15 442933108211201 <10 <1 54.7 <1 14.7 <1 47.2 <1 124 <.9 SUS2-16 442239108362001 E30 <1 56.9 15.3 1.8 <1 E.4 <1 193 <.9 SUS2-17 442258108260301 <10 <1 27.1 <1 6.3 <1 E.7 <1 48.7 <.9 SUS2-18 442348108082301 E20 <5 265 197 <5 24 47.6 <5 2,350 <5 SUS2-19 441220108513301 <10 <1 5.6 14.6 3.4 1.62 1.3 <1 414 <.9 SUS2-20 441639108195501 40 <.08 31.7 2.1 4.4 .1 <.3 <1 47 <.04 SUS2-22 440943108455001 1,040 <.08 24.7 230 .8 <.06 E.2 <1 369 <.04 SUS2-23 440306108160601 140 <.08 58.9 4.8 4.8 E.04 <.3 <1 96.7 <.04 SUS2-24 441046107562201 <30 <1 102 161 48.8 5.57 13.6 <1 1,290 <.9 SUS2-25 440008108272601 E20 .08 50.9 13.3 .6 .16 .4 <1 225 <.04 SUS2-26 435735108074101 <10 <1 37.6 3.8 6.1 <1 <.7 <1 65.6 <.9 SUS2-27 440207107553001 <30 <1 62.1 2 4,730 3.19 92.5 <1 1,870 <.9 SUS2-28 435143108090501 E20 <1 24.7 2.6 1.4 <1 E.6 <1 221 <.9 SUS2-29 435556107580701 <30 <1 66.3 62.1 9.5 2.28 2.4 <1 625 <.9 SUS2-30 435115107454801 110 <.08 11.3 42.5 .6 .4 1 <2 557 .72 
Appendix 7-1. Analyses for nutrients and dissolved organic carbon, samples from Quaternary aquifers [USGS, U.S. Geological Survey; mg/L, milligrams per liter; N, nitrogen; P, phosphorus; C, carbon; number below the compound is the data parameter code, whi

USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than; E, estimated 

Well number USGS site- identification number Sample date (month/day/ year) Sample time (24 hour) Nitrite, dissolved (mg/L as N) (00613) Nitrate plus nitrite, dissolved (mg/L as N) (00631) Ammonia, dissolved (mg/L as N) (00608) Ammonia plus organic nitrogen, dissolved (mg/L as N) (00623) Phosphorus, dissolved (mg/L as P) (00666) Ortho- phosphate, dissolved (mg/L as P) (00671) 

SUS1-1 440629109092401 10/19/99 1100 <0.01 <0.05 0.035 0.28 0.039 0.04 SUS1-2 442618109130202 03/29/00 1100 <.01 .743 <.02 .11 .07 .058 SUS1-3 444500109013101 10/13/99 1100 <.01 4.62 <.02 .23 .013 .012 SUS1-4 445613109081401 10/13/99 1700 <.01 2.14 <.02 E.08 E.003 <.01 SUS1-5 451411109134301 03/30/00 1000 <.01 .463 <.02 <.1 .009 <.01 SUS1-6 453101108512801 11/01/99 1200 <.01 <.05 .032 .23 .006 .019 SUS1-7 451033108575401 11/02/99 1300 .01 2.92 .069 .17 E.005 <.01 SUS1-8 444639108452601 12/13/99 1300 .032 12.6 <.02 .46 .012 <.01 SUS1-9 444126108513401 10/12/99 1500 <.01 1.18 <.02 .16 .042 .031 SUS1-10 441556108473201 12/15/99 1100 .115 11.3 <.02 2.2 .034 .029 SUS1-11 440213108583501 10/18/99 1100 <.01 <.05 <.02 .14 .011 <.01 SUS1-12 434334108351101 12/16/99 1000 <.01 <.05 <.02 .3 .018 .015 SUS1-13 440027108264501 03/28/00 1100 <.01 <.05 .089 1.1 .013 .012 SUS1-14 442354108255801 01/11/00 1100 <.01 <.05 .02 .17 .025 .022 SUS1-16 444424108354001 10/14/99 1200 <.01 <.05 .047 .11 .022 .022 SUS1-17 445014108224301 11/03/99 1100 .011 4.65 <.02 .46 .032 .022 SUS1-18 443023108233201 10/20/99 1100 <.01 7.78 <.02 .32 .029 .027 SUS1-19 442258108141201 01/12/00 1100 <.01 <.05 .02 .34 .012 <.01 SUS1-22 433519108125201 10/05/99 1000 <.01 .077 <.02 E.09 E.003 <.01 SUS1-24 435010107214701 01/10/00 1100 <.01 <.05 .427 .52 E.003 <.01 SUS1-25 440054107581401 10/06/99 1000 <.01 <.05 .25 .36 E.004 .011 SUS1-27 440952107405101 01/13/00 1100 <.01 <.05 .02 <.1 E.005 <.01 

SUS1-28 441554107560001 10/07/99 1000 .015 <.05 .279 .69 E.004 .043 

SUS1-29 441821108014701 10/21/99 1000 <.01 2.05 .034 .17 .011 .015 SUS1-30 444719108050501 11/04/99 1100 <.01 <.05 .295 .31 <.006 .013 
Appendix 7-2. Analyses for nutrients and dissolved organic carbon, samples from lower Tertiary aquifers[USGS, U.S. Geological Survey; mg/L, milligrams per liter; N, nitrogen; P, phosphorus; C, carbon; number below the compound is the data parameter code, whi

USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than; E, estimated 

Well 

number

USGS siteidentification number

Sample date 

(month/day/

year)

Sample 

time 

(24 hour)

Nitrite, 

dissolved 

(mg/L as N) 

(00613)

Nitrate plus 

nitrite, 

dissolved 

(mg/L as N) 

(00631)

Ammonia, 

dissolved 

(mg/L as N) 

(00608)

Ammonia 

plus organic 

nitrogen, 

dissolved 

(mg/L as N) 

(00623)

Phosphorus, 

dissolved 

(mg/L as P) 

(00666)

Orthophosphate

dissolved 

(mg/L as P) 

(00671)

SUS2-1 451608109223001 02/26/01 1300 <0.006 <0.047 0.429 0.48 0.068 0.072 SUS2-2 452239109191101 08/08/00 1100 <.01 <.05 .053 .26 <.006 <.01 SUS2-3 452326109065301 08/07/00 1200 <.01 1.85 <.02 .15 .033 .025 SUS2-4 451407109133901 08/09/00 1100 <.01 <.05 .937 1.1 .113 .102 SUS2-5 450210109030601 02/28/01 1700 <.006 <.047 3.43 3.7 .033 .028 SUS2-6 450658109010401 02/27/01 1600 .396 1.56 4.31 1 .01 <.018 SUS2-7 445246109084101 07/31/00 1300 <.01 <.05 .267 .31 .016 .02 SUS2-8 444509109010901 08/01/00 1100 <.01 .656 .023 <.1 <.006 <.01 SUS2-9 444911108444501 08/02/00 1100 <.01 2.69 .635 .84 E.003 <.01 

SUS2-10 444107108550201 08/03/00 1000 <.01 <.05 .445 .55 .015 .024 SUS2-11 444326108424501 05/15/01 1600 E.004 4.35 1.37 1.6 E.003 <.018 SUS2-12 444417108381001 03/01/01 1300 <.006 2.82 <.041 .13 <.006 <.018 SUS2-13 443426108593501 06/06/01 1200 <.006 E.036 .494 .58 .016 .028 SUS2-14 442639108220201 10/19/00 1300 .007 1.98 .693 .81 E.005 E.011 SUS2-15 442933108211201 09/18/00 1100 <.01 .688 <.02 .12 .006 .011 SUS2-16 442239108362001 09/20/00 1600 <.01 .062 .487 .55 .011 .012 SUS2-17 442258108260301 07/10/00 1100 .013 <.05 .425 .43 .02 .016 SUS2-18 442348108082301 07/11/00 1100 <.01 4.35 .124 .27 .007 .012 SUS2-19 441220108513301 09/20/00 1100 .041 .408 .334 .43 .034 .033 SUS2-20 441639108195501 10/24/00 1600 <.006 <.047 .484 .53 .014 E.017 SUS2-22 440943108455001 10/25/00 1200 E.003 <.047 .1 .16 <.006 <.018 SUS2-23 440306108160601 10/18/00 1100 <.006 <.047 .871 .98 .01 E.015 SUS2-24 441046107562201 07/12/00 1100 <.01 .155 1.25 1.3 E.003 <.01 SUS2-25 440008108272601 10/26/00 1000 <.006 <.047 1.58 1.7 .009 .02 SUS2-26 435735108074101 09/21/00 1100 .062 .144 .554 .63 .015 .018 SUS2-27 440207107553001 09/19/00 1300 <.01 17.7 <.02 1.1 .034 .03 SUS2-28 435143108090501 06/06/00 1000 <.01 <.05 1.04 1.2 .042 .039 SUS2-29 435556107580701 07/13/00 1100 <.01 .225 2.46 2.7 <.006 <.01 SUS2-30 435115107454801 10/23/00 1300 E.004 .083 2.73 3 .006 E.012 
116 Water-Quality Characteristics of the Bighorn Basin, Wyoming and Montana

Appendix 8-1. Analyses for radionuclides,

[USGS, U.S. Geological Survey; pCi/L, picocuries per liter; number below the compound is the data parameter code,

 to uniquely identify a specific constituent or property; SSMDC, sample-specific minimum detectable concentration; 

Well 

number

USGS siteidentification 

number

Sample 

date 

(month/

day/year

Sample 

time 

(24 hour)

Gross-alpha 

activity, 

dissolved, as 

thorium-230 

(pCi/L) 

(04126)

Gross-alpha 

activity 

precision 

estimate, as 

thorium-230 

(pCi/L) 

(75987)

Gross-beta 

activity, 

dissolved, as 

cesium-137 

(pCi/L) 

(03515)

Radium224, 

dissolved 

(pCi/L) 

(50833)

Radium224 

precision 

estimate 

(pCi/L) 

(50834)

Radium224, 

SSMDC 

(pCi/L) 

(99324)

Radium226, 

dissolved 

(pCi/L) 

(09503)

SUS1-1 440629109092401 10/19/99 1100 <3 3.6 5.54 0.12 0.27 0.44 0.2

SUS1-2 442618109130202 03/29/00 1100 5.45 3.9 <4 0 0 .288 .11

SUS1-3 444500109013101 10/13/99 1100 <3 3.1 <4 .19 .21 .335 .07

SUS1-4 445613109081401 10/13/99 1700 5.75 4.1 <4 .27 .12 .089 .09

SUS1-5 451411109134301 03/03/00 1000 <3 3 <4 .28 .33 .331 .08

SUS1-6 453101108512801 11/01/99 1200 23.3 9.9 11.3 .51 .42 .5 .16

SUS1-7 451033108575401 11/0/299 1300 15.8 7.5 10 .49 .31 .34 .14

SUS1-8 444639108452601 12/13/99 1300 29.1 10 4.94 M .01 .203 -.02

SUS1-9 444126108513401 10/12/99 1500 <3 3 <4 .1 .16 .268 .01

SUS1-10 441556108473201 12/15/99 1100 92.4 30 38 1.83 .89 .716 .12

SUS1-11 440213108583501 10/18/99 1100 <3 2.8 <4 -.1 .28 .747 .03

SUS1-12 434334108351101 12/16/99 1000 <3 3.4 4.78 1.12 .86 .925 .14

SUS1-13 440027108264501 03/28/00 1100 121 100 17.4 10.6 3.1 1.46 .2

SUS1-14 442354108255801 01/11/00 1100 17.5 7.8 18.7 M .06 .515 M

SUS1-16 444424108354001 10/14/99 1200 <3 1.7 <4 1.1 .68 .821 .26

SUS1-17 445014108224301 11/03/99 1100 8.43 2.3 31.8 .59 .56 .761 M

SUS1-18 443023108233201 10/20/99 1100 12 4.4 <4 -.12 .26 .61 -.03

SUS1-19 442258108141201 01/12/00 1100 6.41 5 7.57 .77 .33 .229 .03

SUS1-22 433519108125201 10/05/99 1000 <3 8.1 16.6 2.14 1.2 1.4 .03

SUS1-24 435010107214701 01/10/00 1100 25.5 6.9 48.8 .56 .39 .374 .06

SUS1-25 440054107581401 10/06/99 1000 21.1 13 13.6 .82 .28 .258 .2

SUS1-27 440952107405101 01/13/00 1100 5.68 3.8 6.85 1.57 .61 .43 .21

SUS1-28 441554107560001 10/07/99 1000 -- -- -- .25 .38 .632 .21

SUS1-29 441821108014701 10/21/99 1000 34 16 8.8 2.12 1.1 1.29 .1

SUS1-30 444719108050501 11/04/99 1100 8.96 7.4 <4 .48 .34 .429 .11
Appendix 8 117

samples from Quaternary aquifers

which is a 5-digit number used in the USGS computerized data system, National Water Information System (NWIS), 

μg/L, micrograms per liter; <, less than; M, constituent detected but not quantified; --, not analyzed or reported]

Radium-226 

precision 

estimate 

(pCi/L) 

(76001)

Radium-226, 

SSMDC 

(pCi/L) 

(99325)

Radium228, 

dissolved 

(pCi/L) 

(81366)

Radium-228 

precision 

estimate 

(pCi/L) 

(76000)

Radium228, 

SSMDC 

(pCi/L) 

(99326)

Radon-222 

(pCi/L) 

(82303)

Radon-222 

precision 

estimate 

(pCi/L) 

(76002)

Radon-222, 

SSMDC 

(pCi/L) 

(99327)

Tritium 

(pCi/L) 

(07000)

Tritium 

precision 

estimate 

(pCi/L) 

(75985)

Uranium, 

natural, 

dissolved, 

(μg/L) 

(22704)

0.16 0.14 0.33 0.46 0.914 427 24 93.8 93.8 5.1 3.75

.13 .124 .37 .29 .51 419 24 45.8 45.8 3.2 5.52

.06 .075 .41 .44 .87 676 29 41.6 41.6 2.6 5.46

.04 .025 1.04 .52 .81 1,350 37 47 47 3.2 6.87

.11 .139 .69 .44 .759 1,010 30 47.4 47.4 3.2 <1

.17 .205 1.26 .57 .83 496 23 51.5 51.5 3.2 12.8

.12 .154 .46 .46 .874 802 30 39 39 2.6 8.25

.01 .163 .52 .42 .756 401 23 44.5 44.5 2.6 16.4

.03 .054 2.11 .77 .751 325 23 42.6 42.6 2.6 4.15

.16 .248 .54 .4 .721 742 29 55 55 3.2 123

.09 .207 .59 .52 .972 797 31 62.4 62.4 3.8 <1

.23 .393 .51 .4 .733 478 22 101 101 5.8 6.35

.13 .112 .78 .37 .484 634 28 73.3 73.3 4.5 163

.06 .163 .43 .4 .757 682 29 67.8 67.8 3.8 3.71

.16 .163 1.05 .57 .948 986 30 48.6 48.6 1.6 2.88

.09 .228 .48 .42 .803 432 25 49 49 3.2 29.9

.02 .127 .37 .38 .733 680 29 53.4 53.4 3.2 16.8

.04 .579 .54 .45 .835 556 27 61.8 61.8 3.8 5.21

.12 .226 .73 .46 .777 854 29 20.2 20.2 1.6 5.36

.09 .141 .39 .39 .745 1,360 37 57 57 3.2 3.49

.07 .058 1.25 .59 .892 1,110 32 41.9 41.9 2.6 7.08

.14 .144 .53 .34 .545 934 30 61.4 61.4 3.8 7.25

.15 .163 1.67 .61 .725 435 22 51.2 51.2 3.2 9.49

.22 .382 .68 .47 .809 1,350 34 51.5 51.5 3.2 23.2

.1 .132 .6 .47 .869 869 28 63.7 63.7 3.8 2.17
Appendix 8-2. Analyses for radionuclides, samples from lower Tertiary aquifers [USGS, U.S. Geological Survey; pCi/L, picocuries per liter; number below the compound is the data parameter code, which is a 5-digit number used in the USGS computerInformation System (NWIS), to uniquely identify a specific constituent or property; SSMDC, sample-specific minimum detectable concentration; μg/L, micrograms per litecentration; --, not analyzed or reported] Well number USGS site- identification number Sample date (month/ day/year) Sample time (24 hour) Gross-alpha activity, dissolved, as thorium-230 (pCi/L) (04126) Gross-alpha activity precision estimate, as thorium-230 (pCi/L) (75987) Gross-alpha activity, SSMDC (pCi/L) (99337) Gross-beta activity, dissolved, as cesium-137 (pCi/L) (03515) Gross-beta activity precision estimate, as cesium-137 (pCi/L) (75989) Gross-beta activity, SSMDC (pCi/L) (99323) Ra

d

SUS2-1 451608109223001 02/26/01 1300 -- 2.1 4.98 3.12 5.8 8.16 SUS2-2 452239109191101 08/08/00 1100 13.1 6.2 -- <4 8.2 -- SUS2-3 452326109065301 08/07/00 1200 <3 2.2 -- <4 4.5 -- SUS2-4 451407109133901 08/09/00 1100 <3 2.7 -- <4 4.8 -- SUS2-5 450210109030601 02/28/01 1700 -- 13 27.3 5.93 28 39.7 SUS2-6 450658109010401 02/27/01 1600 40.5 32 50.7 18.1 41 70.5 SUS2-7 445246109084101 07/31/00 1300 8.76 3.8 -- 6.9 4.6 -- SUS2-8 444509109010901 08/01/00 1100 <3 3.4 -- 5.69 4.8 -- SUS2-9 444911108444501 08/02/00 1100 <3 6.1 -- <4 15 -- 

SUS2-10 444107108550201 08/03/00 1000 <3 3 -- <4 8.2 -- SUS2-11 444326108424501 05/15/01 1600 30.3 20 43.8 -- -- -- SUS2-12 444417108381001 03/01/01 1300 14.9 8.1 10.9 19.9 12 15.9 SUS2-13 443426108593501 06/06/01 1200 5.59 6.5 10.7 7.76 5.1 9.09 SUS2-14 442639108220201 10/19/00 1300 5.16 4.5 -- 4.86 9.6 -- SUS2-15 442933108211201 09/18/00 1100 25.3 4.6 -- 12.7 5.5 -- SUS2-16 442239108362001 09/20/00 1600 -- 6.2 -- <4 13 -- SUS2-17 442258108260301 07/10/00 1100 <3 2.3 -- <4 4.7 -- SUS2-18 442348108082301 07/11/00 1100 13.1 30 -- <4 42 -- SUS2-19 441220108513301 09/20/00 1100 E5.02 3.4 -- <4 4.7 -- SUS2-20 441639108195501 10/24/00 1600 <3 2.6 -- <4 4.7 -- SUS2-22 440943108455001 10/25/00 1200 <3 1.3 -- 10.3 5.4 -- SUS2-23 440306108160601 10/18/00 1100 E4.19 5.2 -- <4 8.9 -- SUS2-24 441046107562201 07/12/00 1100 <3 5.9 -- <4 16 -- SUS2-25 440008108272601 10/26/00 1000 22.3 6.4 -- 36.5 11 -- SUS2-26 435735108074101 09/21/00 1100 3.3 2.5 -- 5.58 5.1 -- SUS2-27 440207107553001 09/19/00 1300 E22.4 9 -- 14.3 6.4 -- SUS2-28 435143108090501 06/06/00 1000 <3 4.7 -- 9.78 12 -- SUS2-29 435556107580701 07/13/00 1100 <3 5.6 -- <4 16 -- SUS2-30 435115107454801 10/23/00 1300 E22.3 13 -- 11.1 18 -- 
Appendix 8-2. Analyses for radionuclides, samples from lower Tertiary aquifers--Continued

Well 

number

Radium224, 

SSMDC 

(pCi/L)

(99324)

Radium226, 

dissolved 

(pCi/L)

(09503)

Radium226 

precision 

estimate 

(pCi/L)

(76001)

Radium226, 

SSMDC

(pCi/L)

(99325)

Radium228, 

dissolved 

(pCi/L)

(81366)

Radium228 

precision 

estimate 

(pCi/L)

(76000)

Radium228, 

SSMDC 

(pCi/L)

(99326)

Radon-222 

(pCi/L)

(82303)

Radon222, 

precision 

estimate 

(pCi/L)

(76002)

Radon222, 

SSMDC 

(pCi/L)

(99327)

Tritium 

(pCi/L)

(07000)

T

p

e

SUS2-1 0.092 0.12 0.07 0.052 0.83 0.5 0.848 429 24 25 1.9 SUS2-2 .083 .04 .02 .023 .35 .33 .596 798 32 -- 66.2 SUS2-3 .025 .07 .04 .024 .67 .41 .677 1,670 42 -- 44.2 SUS2-4 .041 .03 .02 .023 .34 .29 .533 273 20 -- 23.7 SUS2-5 .23 .26 .1 .025 1.31 .55 .76 343 22 25 .3 SUS2-6 .54 .56 .26 .26 .86 .47 .785 449 24 24 .3 SUS2-7 .029 .01 .02 .022 .47 .42 .79 781 34 -- <1 SUS2-8 .115 .13 .05 .043 .49 .46 .886 979 35 -- 69.1 SUS2-9 .307 .09 .07 .087 .86 .49 .818 4,420 65 -- 63 

SUS2-10 .204 .04 .05 .082 .43 .5 .968 2,090 41 -- 21.8 SUS2-11 .38 .54 .28 .17 .89 .47 .754 1,100 33 24 25 SUS2-12 .56 .23 .15 .14 .26 .43 .88 658 25 21 45.1 SUS2-13 .33 .54 .32 .23 .67 .42 .736 392 21 22 40.3 SUS2-14 .195 1.15 .37 .178 .87 .5 .843 2,150 41 -- 1.3 SUS2-15 .436 .11 .09 .086 .53 .41 .759 2,240 48 -- 57 SUS2-16 .218 .16 .07 .031 .74 .41 .671 529 28 -- <1 SUS2-17 .141 .21 .08 .075 .32 .29 .522 604 33 -- <1 SUS2-18 .875 .43 .2 .12 1 .53 .867 876 33 -- 61.4 SUS2-19 .052 .17 .07 .029 1.36 .54 .734 991 35 -- 23 SUS2-20 .196 .22 .19 .151 .59 .42 .757 1,400 37 -- -.3 SUS2-22 .669 .76 .32 .207 1 .54 .872 451 52 -- 19.2 SUS2-23 .351 .16 .11 .095 .86 .45 .735 596 27 -- .3 SUS2-24 .323 .38 .13 .058 1.15 .51 .73 1,430 39 -- 5.1 SUS2-25 .278 .29 .18 .122 .75 .52 .931 654 50 -- -.3 SUS2-26 .162 .14 .06 .045 1.05 .48 .72 598 26 -- 1 SUS2-27 -- -- -- -- .95 .45 .69 771 30 -- 23.7 SUS2-28 .093 .23 .09 .073 .63 .47 .861 460 25 -- <1 SUS2-29 .595 .64 .26 .128 1.13 .55 .869 320 20 -- 1 SUS2-30 .235 .52 .32 .259 .89 .49 .823 246 21 -- -.3 
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers [Detections in bold and underlined. USGS, U.S. Geological Survey; μg/L, micrograms per liter; number below the compound is the data parameter code, which is a 

computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than, indicates chemical was n

ing the less than is the laboratory reporting level; --, not analyzed; E, estimated concentration; M, chemical was detected but not quantified; U, chemical was analyze

italics were obtained using a research method and holding times were exceeded] Well number USGS site- identification number Date (month/ day/year) Time (24 hour) Acetochlor (μg/L) (49260) Acifluorfen (μg/L) (49315) Alachlor (μg/L) (46342) Aldicarb (μg/L) (49312) Aldicarb sulfone (μg/L) (49313) Aldicarb sulfoxide (μg/L) (49314) Atraz

(μg/

(3963

SUS1-1 440629109092401 10/19/99 1100 <0.002 <0.06 <0.002 <0.08 <0.16 <0.03 <0.0SUS1-2 442618109130202 03/29/00 1100 -- <.06 -- <.08 <.16 <.03 <.0SUS1-3 444500109013101 10/13/99 1100 <.002 <.06 <.002 <.08 <.16 <.03 .0SUS1-4 445613109081401 10/13/99 1700 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-5 451411109134301 03/30/00 1000 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-6 453101108512801 11/01/99 1200 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-7 451033108575401 11/02/99 1300 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-8 444639108452601 12/13/99 1300 <.002 <.06 <.002 <.08 <.16 <.03 .0SUS1-9 444126108513401 10/12/99 1500 <.002 <.06 <.002 <.08 <.16 <.03 <.0

SUS1-10 441556108473201 12/15/99 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-11 440213108583501 10/18/99 1100 <.002 <.06 <.002 <.08 <.16 <.03 .0SUS1-12 434334108351101 12/16/99 1000 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-13 440027108264501 03/28/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-14 442354108255801 01/11/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 E.0SUS1-16 444424108354001 10/14/99 1200 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-17 445014108224301 11/03/99 1100 <.002 <.06 <.002 <.08 <.16 <.03 .0SUS1-18 443023108233201 10/20/99 1100 <.002 <.06 <.002 <.08 <.16 <.03 .0SUS1-19 442258108141201 01/12/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-22 433519108125201 10/05/99 1000 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-24 435010107214701 01/10/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-25 440054107581401 10/06/99 1000 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-27 440952107405101 01/13/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-28 441554107560001 10/07/99 1000 <.002 <.06 <.002 <.08 <.16 <.03 <.0SUS1-29 441821108014701 10/21/99 1000 <.002 <.06 <.002 <.08 <.16 <.03 .0SUS1-30 444719108050501 11/04/99 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.0
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued

Well 

number

Bendiocarb

(μg/L)

(50299)

Benfluralin 

(μg/L) 

(82673

Benomyl 

(μg/L) 

(50300)

Bensulfuron, 

methyl 

(μg/L) 

(61693)

Bentazon 

(μg/L) 

(38711)

Bromacil 

(μg/L) 

(04029)

Bromoxynil 

(μg/L) 

(49311)

Butylate 

(μg/L) 

(04028)

Caffeine1

(μg/L) 

(50305)

Carbaryl 

(μg/L) 

(49310)

Car

(μ

(82

SUS1-1 <0.061 <0.002 <0.022 <0.0482 <0.02 <0.08 <0.06 <0.002 <0.081 <0.06 <0SUS1-2 <.061 -- <.022 <.0482 <.02 <.08 <.06 -- E.021 <.06 -- SUS1-3 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-4 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-5 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-6 <.061 E.001 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-7 <.061 <.002 <.022 <.0482 M <.08 <.06 <.002 <.081 <.06 <SUS1-8 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-9 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <

SUS1-10 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-11 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-12 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-13 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-14 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-16 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-17 <.061 <.002 <.022 <.0482 <.02 M <.06 <.002 <.081 <.06 <SUS1-18 <.061 <.002 <.022 <.0482 M <.08 <.06 <.002 <.081 <.06 <SUS1-19 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-22 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-24 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-25 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-27 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-28 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-29 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS1-30 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued Well number Carbofuran (μg/L) (82674) Chloramben, methyl ester (μg/L) (61188) Chlorimuron (μg/L) (50306) Chloro- thalonil (μg/L) (49306) Chlor- pyrifos (μg/L) (38933) Clopyralid (μg/L) (49305) Cyanazine (μg/L) (04041) Cycloate (μg/L) (04031) 2,4-D (μg/L) (39732) 2,4-

(μg

(387

SUS1-1 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.08 <0.SUS1-2 -- <.11 <.037 <.05 -- <.04 -- <.05 <.08 <.SUS1-3 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-4 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-5 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-6 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-7 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-8 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-9 <.003 <.11 <.037 <.05 <.004 <.04 .066 <.05 <.08 <.

SUS1-10 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-11 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-12 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-13 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-14 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-16 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-17 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-18 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-19 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-22 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-24 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-25 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-27 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-28 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-29 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.SUS1-30 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued

Well 

number

Dacthal 

monoacid 

(μg/L) 

(49304)

DCPA 

(μg/L) 

(82682)

p,p’-DDE 

(μg/L) 

(34653)

Deethylatrazine 

(μg/L) 

(04040)

Deethyl, 

deisopropylatrazine 

(μg/L) 

(04039)

Deisopropylatrazine 

(μg/L) 

(04038)

Diazinon

(μg/L) 

(39572)

Dicamba 

(μg/L) 

(38442)

Dichloroprop 

(μg/L) 

(49302)

Dieldri

(μg/L

(39381

SUS1-1 <0.07 <0.002 <0.006 <0.002 <0.06 <0.07 <0.002 <0.10 <0.05 <0.00SUS1-2 <.07 -- -- <.087 <.06 <.07 -- <.10 <.05 -- SUS1-3 <.07 <.002 <.006 E.007 <.06 <.07 <.002 <.10 <.05 <.00SUS1-4 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-5 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-6 <.07 E.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 E.003 SUS1-7 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-8 <.07 E.002 <.006 E.011 M M <.002 <.10 <.05 <.00SUS1-9 <.07 <.002 <.006 <.002 M M <.002 <.10 <.05 <.00

SUS1-10 <.07 <.002 <.006 <.002 M <.07 <.002 <.10 <.05 <.00SUS1-11 <.07 <.002 <.006 E.014 M <.07 <.002 <.10 <.05 <.00SUS1-12 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-13 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-14 <.07 <.002 <.006 E.004 <.06 <.07 <.002 <.10 <.05 <.00SUS1-16 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-17 <.07 <.002 <.006 E.015 M <.07 <.002 <.10 <.05 <.00SUS1-18 <.07 <.002 <.006 E.003 M <.07 <.002 <.10 <.05 <.00SUS1-19 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-22 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-24 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-25 <.07 <.002 <.006 E.004 <.06 <.07 <.002 <.10 <.05 <.00SUS1-27 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-28 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00SUS1-29 <.07 E.002 <.006 E.008 M <.07 <.002 <.10 <.05 <.00SUS1-30 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.00
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued Well number Dinoseb (μg/L) (49301) Diphen- amid (μg/L) (04033) Disulfoton (μg/L) (82677) Diuron (μg/L) (49300) EPTC (μg/L) (82668) Ethal- fluralin (μg/L) (82663) Ethoprop (μg/L) (82672) Fenuron (μg/L) (49297) Flumet- sulam (μg/L) (61694) Fluo- meturo

(μg/L) (38811) 

SUS1-1 <0.04 <0.06 <0.017 <0.08 <0.002 <0.004 <0.003 <0.07 <0.0866 <0.06 SUS1-2 <.04 <.06 -- <.08 -- -- -- <.07 <.0866 <.06 SUS1-3 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-4 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-5 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-6 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-7 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-8 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-9 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 

SUS1-10 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-11 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-12 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-13 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-14 M <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-16 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-17 <.04 <.06 <.017 M <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-18 M <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-19 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-22 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-24 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-25 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-27 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-28 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-29 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 SUS1-30 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.06 
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued

Well 

number

AlphaHCH

(μg/L) 

(34253)

GammaHCH

 (μg/L) 

(39341)

Hydroxyatrazine 

(μg/L) 

(50355)

3-Hydroxycarbofuran 

(μg/L) 

(49308)

Imazaquin 

(μg/L) 

(50356)

Imazethapyr 

(μg/L)

(50407)

Imidacloprid 

(μg/L) 

(61695)

3-keto 

Carbofuran 

(μg/L) 

(50295)

Linuron 

(μg/L) 

(38478)

Linuro

(μg/L

(82666

SUS1-1 <0.002 <0.004 <0.193 <0.06 <0.103 <0.088 <0.1060 <0.072 <0.07 <0.00SUS1-2 -- -- <.193 <.06 -- -- <.1060 <.072 <.07 -- SUS1-3 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-4 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-5 <.002 <.004 <.193 <.06 -- -- <.1060 <.072 <.07 <.00SUS1-6 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-7 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-8 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-9 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00

SUS1-10 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-11 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-12 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-13 <.002 <.004 <.193 <.06 <.103 -- <.1060 <.072 <.07 <.00SUS1-14 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-16 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-17 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-18 <.002 <.004 M <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-19 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-22 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-24 <.002 <.004 <.193 <.06 <.103 -- <.1060 <.072 <.07 <.00SUS1-25 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-27 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-28 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-29 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00SUS1-30 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.00
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued Well number MCPA (μg/L) (38482) MCPB (μg/L) (38487) Metalaxyl (μg/L) (50359) Methiocarb (μg/L) (38501) Methomyl (μg/L) (49296) Methomyl- oxime (μg/L) (61696) Methyl parathion (μg/L) (82667) Metolachlor (μg/L) (39415) Metribuzin (μg/L) (82630) Metsulfu

(μg/L) (61697

SUS1-1 <0.06 <0.06 <0.057 <0.08 <0.08 <0.0102 <0.006 <0.002 <0.004 <0.1138 SUS1-2 <.06 <.06 <.057 <.08 <.08 <.0102 -- -- -- <.1138 SUS1-3 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 .009 <.004 <.1138 SUS1-4 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-5 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-6 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-7 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-8 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-9 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 

SUS1-10 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-11 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-12 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-13 <.06 <.06 <.057 <.08 <.08 <.2000 <.006 <.002 <.004 <.1138 SUS1-14 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-16 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-17 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-18 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-19 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-22 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-24 <.06 <.06 <.057 <.08 <.08 <.2000 <.006 <.002 <.004 <.1138 SUS1-25 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-27 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-28 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-29 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 SUS1-30 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1138 
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued

Well 

number

Napropamide 

(μg/L) 

(82684)

Neburon 

(μg/L) 

(49294)

Nicosulfuron

(μg/L) 

(50364)

Norflurazon 

(μg/L) 

(49293)

Oryzalin 

(μg/L) 

(49292)

Oxamyl 

(μg/L) 

(38866)

Oxamyloxime 

(μg/L) 

(50410)

Parathion 

(μg/L) 

(39542)

Pebulate 

(μg/L) 

(82669)

Pendimethalin 

(μg/L) 

(82683)

cis

Perme

(μg/

(826

SUS1-1 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.064 <0.004 <0.004 <0.004 <0.0SUS1-2 -- <.07 <.065 <.08 <.07 <.02 <.064 -- -- -- -- SUS1-3 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-4 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-5 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-6 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-7 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-8 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-9 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0

SUS1-10 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-11 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-12 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-13 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-14 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-16 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-17 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-18 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-19 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-22 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-24 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-25 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-27 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-28 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-29 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0SUS1-30 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.0
Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued Well number Picloram (μg/L) (49291) Prometon (μg/L) (04037) Pronamide (μg/L) (82676) Propachlor (μg/L) (04024) Propanil (μg/L) (82679) Propargite (μg/L) (82685) Propham (μg/L) (49236) Pro- piconazole (μg/L) (50471) Propoxur (μg/L) (38538) Siduron (μg/L) (38548) Simaz

(μg/

(0403

SUS1-1 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.064 <0.06 <0.093 <0.0SUS1-2 <.07 -- -- -- -- -- <.07 <.064 <.06 <.093 -- SUS1-3 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-4 <.07 .030 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-5 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-6 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-7 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-8 <.07 E.004 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 E.0SUS1-9 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0

SUS1-10 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-11 <.07 .056 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-12 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-13 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-14 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-16 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-17 <.07 .326 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 .0SUS1-18 <.07 .030 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-19 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-22 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 E.0SUS1-24 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-25 M .051 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 .0SUS1-27 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-28 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-29 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS1-30 <.07 <.018 <.003 <.007 <.004 -- <.07 <.064 <.06 <.093 <.0
1Although caffeine is not a pesticide, it is included in the analytical method for pesticides for this study.

Appendix 9-1. Analyses for pesticides, samples from Quaternary aquifers--Continued

Well 

number

Tebuthiuron 

(μg/L) 

(82670)

Terbacil 

(μg/L) 

(04032)

Terbacil 

(μg/L) 

(82665)

Terbufos 

(μg/L) 

(82675)

Terbuthylazine 

(μg/L) 

(04022)

Thiobencarb 

(μg/L) 

(82681)

Triallate 

(μg/L) 

(82678)

Tribenuron 

methyl

(μg/L) 

(61159)

Triclopyr 

(μg/L) 

(49235)

Trifluralin 

(μg/L) 

(82661)

SUS1-1 <0.010 <0.10 <0.007 <0.013 U <0.002 <0.001 <0.07 <0.10 <0.002 SUS1-2 <.077 <.10 -- -- -- -- -- <.07 <.10 -- SUS1-3 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-4 1.36 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-5 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-6 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-7 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-8 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-9 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-10 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-11 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-12 E.004 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-13 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-14 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-16 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-17 .214 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-18 E.009 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 E.001 SUS1-19 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-22 E.004 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-24 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-25 .111 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-27 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-28 <.010 <.10 <.007 <.013 -- <.002 <.001 <.07 <.10 <.002 SUS1-29 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS1-30 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers [Detections in bold and underlined. USGS, U.S. Geological Survey; μg/L, micrograms per liter; number below the compound is the data parameter code, which is a 5-

computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than, indicates chemical was not the less than is the laboratory reporting level; E, estimated concentration; --, not analyzed; U, chemical was analyzed for, but not detected] Well number USGS site- identification number Date (month/ day/year) Time (24 hour) Acetochlor (μg/L) (49260) Acifluorfen (μg/L) (49315) Alachlor (μg/L) (46342) Aldicarb (μg/L) (49312) Aldicarb sulfone (μg/L) (49313) Aldicarb sulfoxide (μg/L) (49314) Atra

(μ

(39

SUS2-1 451608109223001 02/26/01 1300 <0.004 <0.06 <0.002 <0.08 <0.16 <0.03 <0.SUS2-2 452239109191101 08/08/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-3 452326109065301 08/07/00 1200 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-4 451407109133901 08/09/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-5 450210109030601 02/28/01 1700 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-6 450658109010401 02/27/01 1600 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-7 445246109084101 07/31/00 1300 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-8 444509109010901 08/01/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-9 444911108444501 08/02/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.

SUS2-10 444107108550201 08/03/00 1000 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-11 444326108424501 05/15/01 1600 <.004 <.01 <.002 <.04 <.02 <.01 <.SUS2-12 444417108381001 03/01/01 1300 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-13 443426108593501 06/06/01 1200 <.004 <.01 <.002 <.04 <.02 <.01 <.SUS2-14 442639108220201 10/19/00 1300 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-15 442933108211201 09/18/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-16 442239108362001 09/20/00 1600 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-17 442258108260301 07/10/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-18 442348108082301 07/11/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-19 441220108513301 09/20/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-20 441639108195501 10/24/00 1600 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-22 440943108455001 10/25/00 1200 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-23 440306108160601 10/18/00 1100 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-24 441046107562201 07/12/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-25 440008108272601 10/26/00 1000 <.004 <.06 <.002 <.08 <.16 <.03 <.SUS2-26 435735108074101 09/21/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-27 440207107553001 09/19/00 1300 <.002 <.06 <.002 <.08 <.16 <.03 E.SUS2-28 435143108090501 06/06/00 1000 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-29 435556107580701 07/13/00 1100 <.002 <.06 <.002 <.08 <.16 <.03 <.SUS2-30 435115107454801 10/23/00 1300 <.004 <.06 <.002 <.08 <.16 <.03 <.
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued

Well 

number

Bendiocarb

(μg/L)

(50299)

Benfluralin 

(μg/L) 

(82673

Benomyl 

(μg/L) 

(50300)

Bensulfuron, 

methyl 

(μg/L) 

(61693)

Bentazon 

(μg/L) 

(38711)

Bromacil 

(μg/L) 

(04029)

Bromoxynil 

(μg/L) 

(49311)

Butylate 

(μg/L) 

(04028)

Caffeine1

(μg/L) 

(50305)

Carbaryl 

(μg/L) 

(49310)

Ca

(μ

(8

SUS2-1 <0.061 <0.010 <0.022 <0.0482 <0.02 <0.08 <0.06 <0.002 <0.081 <0.06 <0SUS2-2 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-3 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-4 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-5 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-6 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-7 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-8 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 E.005 <.06 <SUS2-9 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <

SUS2-10 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-11 <.025 <.010 <.004 <.0158 E.32 <.03 <.02 <.002 <.010 <.03 <SUS2-12 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-13 <.025 <.010 <.004 <.0158 <.01 <.03 <.02 <.002 <.010 <.03 <SUS2-14 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-15 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-16 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-17 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-18 <.061 <.002 <.022 <.0482 E.01 <.08 <.06 <.002 <.081 <.06 <SUS2-19 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-20 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-22 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-23 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-24 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-25 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-26 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-27 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-28 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-29 <.061 <.002 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <SUS2-30 <.061 <.010 <.022 <.0482 <.02 <.08 <.06 <.002 <.081 <.06 <
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued Well number Carbofuran (μg/L) (82674) Chloramben, methyl ester (μg/L) (61188) Chlorimuron (μg/L) (50306) Chloro- thalonil (μg/L) (49306) Chlor-pyrifos (μg/L) (38933) Clopyralid (μg/L) (49305) Cyanazine (μg/L) (04041) Cycloate (μg/L) (04031) 2,4-D (μg/L) (39732) 2,4-D

(μg/

(3874

SUS2-1 <0.020 <0.11 <0.037 <0.05 <0.005 <0.04 <0.018 <0.05 <0.08 <0.0SUS2-2 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-3 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-4 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-5 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-6 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-7 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-8 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-9 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0

SUS2-10 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-11 <.020 <.02 <.010 <.04 <.005 .02 <.018 <.01 <.02 <.0SUS2-12 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-13 <.020 <.02 <.010 <.04 <.005 <.01 <.018 <.01 <.02 <.0SUS2-14 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-15 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-16 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-17 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-18 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-19 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-20 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-22 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-23 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-24 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-25 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0SUS2-26 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-27 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-28 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-29 <.003 <.11 <.037 <.05 <.004 <.04 <.004 <.05 <.08 <.0SUS2-30 <.020 <.11 <.037 <.05 <.005 <.04 <.018 <.05 <.08 <.0
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued

Well 

number

Dacthal 

mono-acid 

(μg/L) 

(49304)

DCPA 

(μg/L) 

(82682)

p,p’-DDE 

(μg/L) 

(34653)

Deethylatrazine 

(μg/L) 

(04040)

Deethyl, 

deisopropylatrazine 

(μg/L) 

(04039)

Deisopropylatrazine 

(μg/L) 

(04038)

Diazinon

(μg/L) 

(39572)

Dicamba 

(μg/L) 

(38442)

Dichloroprop 

(μg/L) 

(49302)

Dield

(μg

(393

SUS2-1 <0.07 <0.003 <0.003 <0.006 <0.06 <0.07 <0.005 <0.10 <0.05 <0.0SUS2-2 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-3 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-4 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-5 <.07 <.003 <.003 <.006 <.06 <.07 <.005 <.10 <.05 <.0SUS2-6 <.07 <.003 <.003 <.006 <.06 <.07 <.005 <.10 <.05 <.0SUS2-7 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-8 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-9 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0

SUS2-10 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-11 <.01 <.003 <.003 <.006 <.01 <.04 <.005 <.01 <.01 <.0SUS2-12 <.07 <.003 <.003 <.006 <.06 E.07 <.005 <.10 <.05 <.0SUS2-13 <.01 <.003 <.003 <.006 <.01 <.04 <.005 <.01 <.01 <.0SUS2-14 <.07 <.003 <.003 <.006 <.06 <.07 <.005 <.10 <.05 <.0SUS2-15 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-16 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-17 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-18 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-19 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-20 <.07 <.003 <.003 <.006 <.06 <.07 <.005 <.10 <.05 <.0SUS2-22 <.07 <.003 <.003 <.006 <.06 <.07 <.005 <.10 <.05 <.0SUS2-23 <.07 <.003 <.003 <.006 <.06 <.07 <.005 <.10 <.05 <.0SUS2-24 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-25 <.07 <.003 <.003 <.006 <.06 <.07 <.005 <.10 <.05 <.0SUS2-26 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-27 <.07 <.002 <.006 E.003 <.06 E.04 <.002 <.10 <.05 <.0SUS2-28 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-29 <.07 <.002 <.006 <.002 <.06 <.07 <.002 <.10 <.05 <.0SUS2-30 <.07 <.003 <.006 <.006 <.06 <.07 <.005 <.10 <.05 <.0
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued Well number Dinoseb (μg/L) (49301) Diphen- amid (μg/L) (04033) Disulfoton (μg/L) (82677) Diuron (μg/L) (49300) EPTC (μg/L) (82668) Ethal- fluralin (μg/L) (82663) Ethoprop (μg/L) (82672) Fenuron (μg/L) (49297) Flumet- sulam (μg/L) (61694) Flu

met

(μg

(38

SUS2-1 <0.04 <0.06 <0.021 <0.08 <0.002 <0.009 <0.005 <0.07 <0.0866 <0.SUS2-2 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-3 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-4 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-5 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.SUS2-6 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.SUS2-7 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-8 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-9 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.

SUS2-10 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-11 <.01 <.03 <.021 <.01 <.002 <.009 <.005 <.03 <.0110 <.SUS2-12 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.SUS2-13 <.01 <.03 <.021 <.01 <.002 <.009 <.005 <.03 <.0110 <.SUS2-14 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.SUS2-15 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-16 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-17 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-18 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-19 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-20 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.SUS2-22 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.SUS2-23 <.04 <.06 <.021 <.08 <.007 <.009 <.005 <.07 <.0866 <.SUS2-24 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-25 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.SUS2-26 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-27 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-28 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-29 <.04 <.06 <.017 <.08 <.002 <.004 <.003 <.07 <.0866 <.SUS2-30 <.04 <.06 <.021 <.08 <.002 <.009 <.005 <.07 <.0866 <.
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued

Well 

number

AlphaHCH

(μg/L)

 (34253)

GammaHCH

 (μg/L) 

(39341)

Hydroxyatrazine 

(μg/L) 

(50355)

3-Hydroxycarbofuran 

(μg/L) 

(49308)

Imazaquin 

(μg/L) 

(50356)

Imazethapyr 

(μg/L) 

(50407)

Imidacloprid 

(μg/L) 

(61695)

3-keto 

Carbofuran 

(μg/L) 

(50295)

Linuron 

(μg/L) 

(38478)

Linu

(μg

(82

SUS2-1 <0.005 <0.004 <0.193 <0.06 <0.103 <0.088 <0.1060 <0.072 <0.07 <0.0SUS2-2 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-3 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-4 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-5 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-6 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-7 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-8 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-9 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0

SUS2-10 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-11 <.005 <.004 <.008 <.01 <.016 <.017 <.0068 <1.50 <.01 <.0SUS2-12 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-13 <.005 <.004 <.008 <.01 <.016 <.017 <.0068 <1.50 <.01 <.0SUS2-14 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-15 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-16 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-17 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-18 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-19 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-20 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-22 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-23 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-24 <.002 <.004 <.193 <.06 <.103 -- <.1060 <.072 <.07 <.0SUS2-25 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-26 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-27 <.002 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0SUS2-28 <.002 <.004 <.193 <.06 <.103 -- <.1060 <.072 <.07 <.0SUS2-29 <.002 <.004 <.193 <.06 <.103 -- <.1060 <.072 <.07 <.0SUS2-30 <.005 <.004 <.193 <.06 <.103 <.088 <.1060 <.072 <.07 <.0
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued Well number MCPA (μg/L) (38482) MCPB (μg/L) (38487) Metalaxyl (μg/L) (50359) Methiocarb (μg/L) (38501) Methomyl (μg/L) (49296) Methomyl- oxime (μg/L) (61696) Methyl parathion (μg/L) (82667) Metholachlor (μg/L) (39415) Metribuzin (μg/L) (82630) M

sulf

(μg

 (61

SUS2-1 <0.06 <0.06 <0.057 <0.08 <0.08 <0.0102 <0.006 <0.013 <0.006 <0.1SUS2-2 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-3 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-4 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-5 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-6 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-7 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-8 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-9 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1

SUS2-10 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-11 <.02 <.01 <.020 <.01 <.0044 <.0110 <.006 <.013 <.006 <.02SUS2-12 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-13 <.02 <.01 <.020 <.01 <.0044 <.0110 <.006 <.013 <.006 <.02SUS2-14 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-15 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-16 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-17 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-18 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-19 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-20 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-22 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-23 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-24 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-25 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1SUS2-26 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-27 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-28 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-29 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.002 <.004 <.1SUS2-30 <.06 <.06 <.057 <.08 <.08 <.0102 <.006 <.013 <.006 <.1
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued

Well 

number

Napropamide 

(μg/L) 

(82684)

Neburon 

(μg/L) 

(49294)

Nicosulfuron

(μg/L) 

(50364)

Norflurazon 

(μg/L) 

(49293)

Oryzalin 

(μg/L) 

(49292)

Oxamyl 

(μg/L) 

(38866)

Oxamyloxime 

(μg/L) 

(50410)

Parathion 

(μg/L) 

(39542)

Pebulate 

(μg/L) 

(82669)

Pendimethalin 

(μg/L) 

(82683)

c

Perm

(μ

(82

SUS2-1 <0.007 <0.07 <0.065 <0.08 <0.07 <0.02 <0.064 <0.007 <0.002 <0.010 <0.SUS2-2 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-3 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-4 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-5 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-6 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-7 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-8 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-9 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.

SUS2-10 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-11 <.007 <.01 <.013 <.02 <.02 <.01 <.013 <.007 <.002 <.010 <.SUS2-12 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-13 <.007 <.01 <.013 <.02 <.02 <.01 <.013 <.007 <.002 <.010 <.SUS2-14 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-15 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-16 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-17 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-18 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-19 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-20 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-22 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-23 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-24 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-25 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.SUS2-26 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-27 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-28 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-29 <.003 <.07 <.065 <.08 <.07 <.02 <.064 <.004 <.004 <.004 <.SUS2-30 <.007 <.07 <.065 <.08 <.07 <.02 <.064 <.007 <.002 <.010 <.
Appendix 9-2. Analyses for pesticides, samples from lower Tertiary aquifers--Continued Well number Picloram (μg/L) (49291) Prometon (μg/L) (04037) Pronamide (μg/L) (82676) Propachlor (μg/L) (04024) Propanil (μg/L) (82679) Propargite (μg/L) (82685) Propham (μg/L) (49236) Pro- iconazole (μg/L) (50471) Propoxur (μg/L) (38538) Siduron (μg/L) (38548) Sima

(μg

(040

SUS2-1 <0.07 <0.015 <0.004 <0.010 <0.011 <0.023 <0.07 <0.064 <0.06 <0.093 <0.0SUS2-2 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-3 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-4 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-5 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-6 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-7 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-8 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-9 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0

SUS2-10 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-11 <.02 <.015 <.004 <.010 <.011 <.023 <.01 <.021 <.01 <.017 <.0SUS2-12 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-13 <.02 <.015 <.004 <.010 <.011 <.023 <.01 <.021 <.01 <.017 <.0SUS2-14 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-15 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-16 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-17 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-18 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-19 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-20 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-22 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-23 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-24 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-25 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0SUS2-26 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-27 <.07 .257 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-28 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-29 <.07 <.018 <.003 <.007 <.004 <.013 <.07 <.064 <.06 <.093 <.0SUS2-30 <.07 <.015 <.004 <.010 <.011 <.023 <.07 <.064 <.06 <.093 <.0
1Although caffeine is not a pesticide, it is included in the analytical method for pesticides for this study.

Appendix 9-2. Analyses for pesticides, samples form lower Tertiary aquifers--Continued

Well 

number

Tebuthiuron 

(μg/L) 

(82670)

Terbacil 

(μg/L) 

(04032)

Terbacil 

(μg/L) 

(82665)

Terbufos 

(μg/L) 

(82675)

Terbuthylazine 

(μg/L) 

(04022)

Thiobencarb 

(μg/L) 

(82681)

Triallate 

(μg/L) 

(82678)

Tribenuron 

methyl

(μg/L) 

(61159)

Triclopyr 

(μg/L) 

(49235)

Trifluralin 

(μg/L) 

(82661)

SUS2-1 <0.016 <0.10 <0.034 <0.017 U <0.005 <0.002 <0.07 <0.10 <0.009 SUS2-2 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-3 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-4 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-5 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-6 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-7 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-8 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-9 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 

SUS2-10 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-11 <.016 <.01 <.034 <.017 -- <.005 <.002 <.01 <.02 <.009 SUS2-12 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-13 <.016 <.01 <.034 <.017 U <.005 <.002 <.01 <.02 <.009 SUS2-14 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-15 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-16 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-17 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-18 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-19 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-20 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-22 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-23 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-24 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-25 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 SUS2-26 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-27 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-28 <.010 <.10 <.007 <.013 U <.002 <.001 -- <.10 <.002 SUS2-29 <.010 <.10 <.007 <.013 U <.002 <.001 <.07 <.10 <.002 SUS2-30 <.016 <.10 <.034 <.017 U <.005 <.002 <.07 <.10 <.009 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers [Detections in bold and underlined. USGS, U.S. Geological Survey; μg/L, micrograms per liter; number below the compound is the data parameter code, which 

USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than, indicates che

value following the less than is the laboratory reporting level; E, estimated concentration; U, chemical was analyzed for, but not detected; M, chemical was detec

Well number USGS site- identification number Sample date (month/ day/year) Sample time (24 hour) Acetone (μg/L) (81552) tert-Amyl methyl ether (μg/L) (50005) Benzene (μg/L) (34030) Bromo- benzene (μg/L) (81555) Bromo- chloro- methane (μg/L) (77297) Bromo- dichloro- methane (μg/L) (32101) Bromo- ethene (μg/L) (50002) 

SUS1-1 440629109092401 10/19/99 1100 <7 <0.1 <0.04 <0.04 <0.04 <0.05 <0.1 SUS1-2 442618109130202 03/29/00 1100 <7 <.1 E.01 <.04 <.04 <.05 <.1 SUS1-3 444500109013101 10/13/99 1100 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-4 445613109081401 10/13/99 1700 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-5 451411109134301 03/30/00 1000 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-6 453101108512801 11/01/99 1200 <7 <.1 E.02 <.04 <.04 <.05 <.1 SUS1-7 451033108575401 11/02/99 1300 <7 <.1 E.07 <.04 <.04 <.05 <.1 SUS1-8 444639108452601 12/13/99 1300 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-9 444126108513401 10/12/99 1500 <7 <.1 <.04 <.04 <.04 <.05 <.1 

SUS1-10 441556108473201 12/15/99 1100 <7 <.1 E.01 <.04 <.04 <.05 <.1 SUS1-11 440213108583501 10/18/99 1100 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-12 434334108351101 12/16/99 1000 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-13 440027108264501 03/28/00 1100 <7 <.1 E.01 <.04 <.04 <.05 <.1 SUS1-14 442354108255801 01/11/00 1100 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-16 444424108354001 10/14/99 1200 <7 <.1 E.02 <.04 <.04 <.05 <.1 SUS1-17 445014108224301 11/03/99 1100 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-18 443023108233201 10/20/99 1100 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-19 442258108141201 01/12/00 1100 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-22 433519108125201 10/05/99 1000 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-24 435010107214701 01/10/00 1100 <7 <.1 E.04 <.04 <.04 <.05 <.1 SUS1-25 440054107581401 10/06/99 1000 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-27 440952107405101 01/13/00 1100 <7 <.1 E.01 <.04 <.04 <.05 <.1 SUS1-28 441554107560001 10/07/99 1000 <35 <.6 <.17 <.18 <.22 <.24 <.5 SUS1-29 441821108014701 10/21/99 1000 <7 <.1 <.04 <.04 <.04 <.05 <.1 SUS1-30 444719108050501 11/04/99 1100 <7 <.1 E.04 <.04 <.04 <.05 <.1 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers--Continued

Well 

number

2-Butanone

(μg/L) 

(81595)

n-Butylbenzene 

(μg/L) 

(77342)

Carbon 

disulfide 

(μg/L) 

(77041)

Chlorobenzene 

(μg/L) 

(34301)

Chloroethane 

(μg/L) 

(34311)

Chloroethene 

(μg/L) 

(39175)

Chloromethane 

(μg/L) 

(34418)

1-Chloro2-methylbenzene

(μg/L) 

(77275)

1-Chloro4-methylbenzene

(μg/L) 

(77277)

3-Chloro1-propene

(μg/L) 

(78109)

SUS1-1 <2 <0.2 <0.07 <0.03 <0.1 <0.1 <0.5 <0.04 <0.06 <0.2 SUS1-2 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-3 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-4 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-5 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-6 <2 <.2 .16 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-7 <2 <.2 E.03 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-8 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-9 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 

SUS1-10 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-11 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-12 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-13 <2 <.2 E.10 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-14 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-16 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-17 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-18 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-19 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-22 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-24 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-25 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-27 <2 <.2 E.04 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-28 <8 <.9 <.35 <.14 <.6 <.6 <2.5 <.21 <.30 <1.0 SUS1-29 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 SUS1-30 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <.2 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers--Continued Well number 1,2- Dibromo- 3-chloro- propane (μg/L) (82625) 1,2- Dibromo- ethane (μg/L) (77651) Dibromo- methane (μg/L) (30217) 1,2- Dichloro- benzene (μg/L) (34536) 1,3- Dichloro- benzene (μg/L) (34566) 1,4- Dichloro- benzene (μg/L) (34571) trans-1,4- Dichloro- 2-butene (μg/L) (73547) Dichloro- difluoro- methane (μg/L) (34668) 1,1- Dichloro- ethane (μg/L) (34496) 1,2- Dichloro- ethane (μg/L) (32103) 

SUS1-1 <0.2 <0.04 <0.05 <0.05 <0.05 <0.05 <0.7 <0.3 <0.07 <0.1 SUS1-2 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-3 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-4 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-5 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-6 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-7 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-8 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-9 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 

SUS1-10 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-11 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-12 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-13 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-14 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-16 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-17 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-18 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-19 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-22 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-24 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-25 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-27 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-28 <1.1 <.18 <.25 <.24 <.27 <.25 <3.5 <1.4 <.33 <.7 SUS1-29 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 SUS1-30 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <.1 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers--Continued

Well 

number

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

trans-1,2-

Dichloroethene 

(μg/L) 

(34546)

Dichloromethane

(μg/L) 

(34423)

1,2-

Dichloropropane 

(μg/L) 

(34541)

1,3-

Dichloropropane 

(μg/L) 

(77173)

2,2-

Dichloropropane 

(μg/L) 

(77170)

1,1-

Dichloropropene, 

(μg/L) 

(77168)

cis-1,3-

Dichloropropene 

(μg/L) 

(34704)

trans-1,3-

Dichloropropene 

(μg/L) 

(34699)

Diethyl 

ether 

(μg/L) 

(81576)

SUS1-1 <0.04 <0.03 <0.4 <0.07 <0.1 <0.05 <0.03 <0.09 <0.09 <0.2 SUS1-2 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-3 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-4 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-5 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-6 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-7 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-8 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-9 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 

SUS1-10 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-11 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-12 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-13 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-14 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-16 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-17 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-18 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-19 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-22 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-24 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-25 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-27 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-28 <.19 <.16 <1.9 <.34 <.6 <.25 <.13 <.45 <.45 <.8 SUS1-29 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 SUS1-30 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <.2 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers--Continued Well number 1,2- Dimethyl- benzene (μg/L) (77135) 1,3 & 1,4- Dimethyl- benzene (μg/L) (85795) (1,1- Dimethyl- ethyl) benzene (μg/L) (77353) Ethenyl- benzene (μg/L) (77128) Ethyl- benzene (μg/L) (34371) Ethyl meth- acrylate (μg/L) (73570) Ethyl tert-butyl ether (μg/L) (50004) 2-Ethyl- toluene (μg/L) (77220) 1,1,2,3,4,4- Hexa- chloro-1,3- butadiene (μg/L) (39702) 1,1,1,2,2,2- Hex- chloro- ethane (μg/L) (34396) 

SUS1-1 <0.04 <0.06 <0.06 <0.04 <0.03 <0.2 <0.05 <0.06 <0.1 <0.2 SUS1-2 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-3 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-4 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-5 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-6 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-7 U U <.06 <.04 U <.2 <.05 E.01 <.1 <.2 SUS1-8 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-9 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 

SUS1-10 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-11 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-12 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-13 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-14 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-16 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-17 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-18 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-19 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-22 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-24 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-25 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-27 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-28 <.19 <.30 <.30 <.21 <.15 <.9 <.27 <.30 <.7 <.9 SUS1-29 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 SUS1-30 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <.2 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers--Continued

Well 

number

Iodomethane 

(μg/L) 

(77424)

1-Isopropyl4-methylbenzene 

(μg/L) 

(77356)

Methyl 

acrylonitrile 

(μg/L) 

(81593)

Methylbenzene 

(μg/L) 

(34010)

(1-Methylethyl) 

benzene 

(μg/L) 

(77223)

Methyl 

methacrylate 

(μg/L) 

(81597)

4-Methyl2-pentanone

(μg/L) 

(78133)

Methyl-2-

propenoate 

(μg/L) 

(49991)

(1-Methylpropyl) 

benzene 

(μg/L) 

(77350)

Methyl 

tert-butyl 

ether 

(MTBE) 

(μg/L) 

(78032)

SUS1-1 <0.1 <0.07 <0.6 <0.05 <0.03 <0.3 <0.4 <1 <0.03 <0.2 SUS1-2 <.1 <.07 <.6 U E.01 <.3 <.4 <1 <.03 <.2 SUS1-3 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-4 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <.2 SUS1-5 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-6 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <.2 SUS1-7 <.1 <.07 <.6 U M <.3 <.4 <1 <.03 <.2 SUS1-8 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <.2 SUS1-9 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 

SUS1-10 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <.2 SUS1-11 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-12 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-13 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-14 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-16 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <.2 SUS1-17 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-18 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-19 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-22 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-24 <.1 E.01 <.6 U <.03 <.3 <.4 <1 <.03 <.2 SUS1-25 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-27 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <.2 SUS1-28 <.6 <.35 <3.0 <.25 <.16 <1.8 <1.9 <7 <.16 <.8 SUS1-29 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <.2 SUS1-30 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <.2 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers--Continued Well number 2-Pro- pene- nitrile (μg/L) (34215) n-Propyl- benzene (μg/L) (77224) 1,1,1,2- Tetra- chloro- ethane (μg/L) (77562) 1,1,2,2- Tetra- chloro- ethane (μg/L) (34516) Tetra- chloro- ethene (μg/L) (34475) Tetra- chloro- methane (μg/L) (32102) Tetra- hydro- furan (μg/L) (81607) 1,2,3,4- Tetra- methyl- benzene (μg/L) (49999 1,2,3,5- Tetra- methyl- benzene (μg/L) (50000) Tribromo- methane (μg/L) (32104) 

SUS1-1 <1 <0.04 <0.03 <0.09 <0.1 <0.06 <2 <0.2 <0.2 <0.06 SUS1-2 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-3 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-4 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-5 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-6 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-7 <1 E.01 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-8 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-9 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 

SUS1-10 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-11 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-12 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-13 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-14 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-16 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-17 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-18 <1 <.04 <.03 <.09 M <.06 <2 <.2 <.2 <.06 SUS1-19 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-22 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-24 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-25 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-27 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-28 <6 <.21 <.15 <.45 <.5 <.30 <11 <1.1 <1.0 <.30 SUS1-29 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <.06 SUS1-30 <1 <.04 <.03 <.09 <.1 <.06 M <.2 <.2 <.06 
Appendix 10-1. Analyses for volatile organic compounds (VOCs), samples from Quaternary aquifers--Continued

Well 

number

1,2,4-

Trichlorobenzene 

(μg/L) 

(34551)

1,1,1-

Trichloroethane 

(μg/L) 

(34506)

1,1,2-

Trichloroethane 

(μg/L) 

(34511)

Trichloroethene 

(μg/L) 

(39180)

Trichlorofluoromethane 

(μg/L) 

(34488)

Trichloromethane 

(μg/L) 

(32106)

1,2,3-

Trichloropropane 

(μg/L) 

(77443)

1,1,2-

Trichloro1,2,2-trifluoroethane 

(μg/L) 

(77652)

1,2,3-

Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-

Trimethylbenzene 

(μg/L) 

(77222)

SUS1-1 <0.2 <0.03 <0.06 <0.04 <0.09 <0.05 <0.2 <0.06 <0.1 0.34 SUS1-2 <.2 <.03 <.06 <.04 <.09 U <.2 <.06 <.1 E.03 SUS1-3 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .17 SUS1-4 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .23 SUS1-5 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS1-6 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .21 SUS1-7 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .14 SUS1-8 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS1-9 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .17 

SUS1-10 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS1-11 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .70 SUS1-12 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS1-13 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 E.01 SUS1-14 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS1-16 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS1-17 <.2 <.03 <.06 <.04 <.09 U <.2 <.06 <.1 .18 SUS1-18 <.2 <.03 <.06 <.04 <.09 U <.2 <.06 <.1 .20 SUS1-19 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 E.08 SUS1-22 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .15 SUS1-24 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 E.08 SUS1-25 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .54 SUS1-27 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS1-28 <.9 <.16 <.30 <.19 <.45 <.26 <.8 <.06 <.6 E.10 SUS1-29 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.30 <.1 .23 SUS1-30 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 .22 
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers [Detections in bold and underlined. USGS, U.S. Geological Survey; μg/L, micrograms per liter; number below the compound is the data parameter code, which is a 5-d

computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property; <, less than, indicates chemical was not detless than is the laboratory reporting level; E, estimated concentration; M, chemical was detected but not quantified] Well number USGS site- identification number Sample date (month/ day/year) Sample time (24 hour) Acetone (μg/L) (81552) tert-Amyl methyl ether (μg/L) (50005) Benzene (μg/L) (34030) Bromo- benzene (μg/L) (81555) Bromo- chloro- methane (μg/L) (77297) Bromo- dichloro- methane (μg/L) (32101) B

e

(

(5

SUS2-1 451608109223001 03/26/01 1300 <7 <0.1 <0.04 <0.04 <0.04 <0.05 <SUS2-2 452239109191101 08/08/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-3 452326109065301 08/07/00 1200 <7 <.1 <.04 <.04 <.04 <.05 SUS2-4 451407109133901 08/09/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-5 450210109030601 02/28/01 1700 <7 <.1 .15 <.04 <.04 <.05 SUS2-6 450658109010401 02/27/01 1600 <7 <.1 E.02 <.04 <.04 <.05 SUS2-7 445246109084101 07/31/00 1300 <7 <.1 <.04 <.04 <.04 <.05 SUS2-8 444509109010901 08/01/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-9 444911108444501 08/02/00 1100 <7 <.1 <.04 <.04 <.04 <.05 

SUS2-10 444107108550201 08/03/00 1000 <7 <.1 <.04 <.04 <.04 <.05 SUS2-11 444326108424501 05/15/01 1600 <7 <.1 <.04 <.04 <.04 <.05 SUS2-12 444417108381001 03/01/01 1300 <7 <.1 <.04 <.04 <.04 <.05 SUS2-13 443426108593501 06/06/01 1200 <7 <.1 <.04 <.04 <.04 <.05 SUS2-14 442639108220201 10/19/00 1300 <7 <.1 <.04 <.04 <.04 <.05 SUS2-15 442933108211201 09/18/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-16 442239108362001 09/20/00 1600 <7 <.1 <.04 <.04 <.04 <.05 SUS2-17 442258108260301 07/10/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-18 442348108082301 07/11/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-19 441220108513301 09/20/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-20 441639108195501 10/24/00 1600 <7 <.1 <.04 <.04 <.04 <.05 SUS2-22 440943108455001 10/25/00 1200 <7 <.1 <.04 <.04 <.04 <.05 SUS2-23 440306108160601 10/18/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-24 441046107562201 07/12/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-25 440008108272601 10/26/00 1000 <7 <.1 <.04 <.04 <.04 <.05 SUS2-26 435735108074101 09/21/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-27 440207107553001 09/19/00 1300 <7 <.1 <.04 <.04 <.04 0.32 SUS2-28 435143108090501 06/06/00 1000 <7 <.1 <.04 <.04 <.04 <.05 SUS2-29 435556107580701 07/13/00 1100 <7 <.1 <.04 <.04 <.04 <.05 SUS2-30 435115107454801 10/23/00 1300 <7 <.1 <.04 <.04 <.04 <.05 
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers--Continued

Well 

number

2-Butanone

(μg/L) 

(81595)

n-Butylbenzene 

(μg/L) 

(77342)

Carbon 

disulfide 

(μg/L) 

(77041)

Chlorobenzene 

(μg/L) 

(34301)

Chloroethane 

(μg/L) 

(34311)

Chloroethene 

(μg/L) 

(39175)

Chloromethane 

(μg/L) 

(34418)

1-Chloro2-methylbenzene

(μg/L)

(77275)

1-Chloro4-methylbenzene

(μg/L) 

(77277)

3-Ch

1-pro

(μg

(78

SUS2-1 <2 <0.2 <0.07 <0.03 <0.1 <0.1 <0.2 <0.03 <0.06 <0SUS2-2 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-3 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-4 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-5 <2 <.2 E.04 <.03 <.1 <.1 <.2 <.03 <.06 <SUS2-6 <2 <.2 <.07 <.03 <.1 <.1 <.2 <.03 <.06 <SUS2-7 <2 <.2 E.05 <.03 <.1 <.1 <.5 <.03 <.06 <SUS2-8 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-9 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <

SUS2-10 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-11 <2 <.2 <.07 <.03 <.1 <.1 <.2 <.03 <.06 <SUS2-12 <2 <.2 <.07 <.03 <.1 <.1 <.2 <.03 <.06 <SUS2-13 <2 <.2 <.07 <.03 <.1 <.1 <.2 <.03 <.06 <SUS2-14 <2 <.2 E.03 <.03 <.1 <.1 E.1 <.04 <.06 <SUS2-15 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-16 <2 <.2 <.07 <.03 <.1 <.1 E.1 <.04 <.06 <SUS2-17 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.03 <.06 <SUS2-18 <2 <.2 <.07 <.03 <.1 <.1 M <.03 <.06 <SUS2-19 <2 <.2 E.01 <.03 <.1 <.1 M <.03 <.06 <SUS2-20 <2 <.2 <.07 <.03 <.1 <.1 E.1 <.04 <.06 <SUS2-22 <2 <.2 <.07 <.03 <.1 <.1 <.2 <.04 <.06 <SUS2-23 <2 <.2 <.07 <.03 <.1 <.1 M <.04 <.06 <SUS2-24 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.03 <.06 <SUS2-25 <2 <.2 <.07 <.03 <.1 <.1 <.2 <.03 <.06 <SUS2-26 <2 <.2 <.07 <.03 <.1 <.1 M <.03 <.06 <SUS2-27 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-28 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-29 <2 <.2 <.07 <.03 <.1 <.1 <.5 <.04 <.06 <SUS2-30 <2 <.2 <.07 <.03 <.1 <.1 M <.03 <.06 <
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers--Continued Well number 1,2-Dibromo- 3-chloro- propane (μg/L) (82625) 1,2-Dibromo- ethane (μg/L) (77651) Dibromo- methane (μg/L) (30217) 1,2-Dichloro- benzene (μg/L) (34536) 1,3-Dichloro- benzene (μg/L) (34566) 1,4-Dichloro- benzene (μg/L) (34571) trans-1,4- Dichloro- 2-butene (μg/L) (73547) Dichloro- difluoro- methane (μg/L) (34668) 1,1-Dichloro- ethane (μg/L) (34496) 1,2-Dic

eth

(μg

(32

SUS2-1 <0.2 <0.04 <0.05 <0.03 <0.03 <0.05 <0.7 <0.3 <0.04 <0SUS2-2 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-3 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-4 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-5 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-6 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-7 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-8 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-9 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <

SUS2-10 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-11 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-12 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-13 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-14 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-15 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-16 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-17 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-18 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-19 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-20 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-22 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-23 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-24 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-25 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <SUS2-26 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-27 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-28 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-29 <.2 <.04 <.05 <.05 <.05 <.05 <.7 <.3 <.07 <SUS2-30 <.2 <.04 <.05 <.03 <.03 <.05 <.7 <.3 <.04 <
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers--Continued

Well 

number

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

trans-1,2-

Dichloroethene 

(μg/L) 

(34546)

Dichloromethane

(μg/L) 

(34423)

1,2-Dichloropropane 

(μg/L) 

(34541)

1,3-Dichloropropane 

(μg/L) 

(77173)

2,2-Dichloropropane 

(μg/L) 

(77170)

1,1-Dichloropropene, 

(μg/L)

(77168)

cis-1,3-

Dichloropropene 

(μg/L) 

(34704)

trans-1,3-

Dichloropropene 

(μg/L) 

(34699)

Die

eth

(μg

(81

SUS2-1 <0.04 <0.03 <0.2 <0.03 <0.1 <0.05 <0.03 <0.09 <0.09 <0SUS2-2 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-3 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-4 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-5 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-6 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-7 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-8 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-9 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <

SUS2-10 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-11 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-12 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-13 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-14 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-15 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-16 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-17 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-18 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-19 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-20 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-22 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-23 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-24 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-25 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <SUS2-26 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-27 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-28 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-29 <.04 <.03 <.4 <.07 <.1 <.05 <.03 <.09 <.09 <SUS2-30 <.04 <.03 <.2 <.03 <.1 <.05 <.03 <.09 <.09 <
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers--Continued Well number 1,2-Dimethyl- benzene (μg/L) (77135) 1,3 & 1,4-Dimethyl- benzene (μg/L) (85795) (1,1- Dimethyl- ethyl) benzene (μg/L) (77353) Ethenyl- benzene (μg/L) (77128) Ethyl- benzene (μg/L) (34371) Ethyl meth- acrylate (μg/L) (73570) Ethyl tert-butyl ether (μg/L) (50004) 2-Ethyl- toluene (μg/L) (77220) 1,1,2,3,4,4- Hexa- chloro-1,3- butadiene (μg/L) (39702) 1,1,1,

He

chl

eth

(μg

(343

SUS2-1 <0.04 <0.06 <0.06 <0.04 <0.03 <0.2 <0.05 <0.06 <0.1 <0SUS2-2 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-3 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-4 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-5 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-6 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-7 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-8 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-9 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <

SUS2-10 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-11 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-12 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-13 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-14 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-15 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-16 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-17 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-18 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-19 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-20 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-22 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-23 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-24 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-25 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-26 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-27 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-28 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-29 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <SUS2-30 <.04 <.06 <.06 <.04 <.03 <.2 <.05 <.06 <.1 <
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers--Continued

Well 

number

Iodomethane 

(μg/L) 

(77424)

1-Isopropyl4-methylbenzene 

(μg/L) 

(77356)

Methyl 

acrylonitrile 

(μg/L) 

(81593)

Methylbenzene 

(μg/L) 

(34010)

(1-Methylethyl) 

benzene 

(μg/L) 

(77223)

Methyl 

methacrylate 

(μg/L) 

(81597)

4-Methyl2-pentanone

(μg/L) 

(78133)

Methyl2-propenoate 

(μg/L) 

(49991)

(1-Methylpropyl) 

benzene 

(μg/L) 

(77350)

Me

tert-

ether (

(μg

(780

SUS2-1 <0.1 <0.07 <0.6 <0.05 <0.03 <0.3 <0.4 <1 <0.03 <0SUS2-2 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-3 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-4 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-5 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-6 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-7 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-8 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-9 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <

SUS2-10 <.1 <.07 <.6 U <.03 <.3 <.4 <1 <.03 <SUS2-11 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-12 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-13 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-14 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-15 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-16 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-17 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-18 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-19 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-20 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-22 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-23 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-24 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-25 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-26 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-27 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-28 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-29 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <SUS2-30 <.1 <.07 <.6 <.05 <.03 <.3 <.4 <1 <.03 <
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers--Continued Well number 2-Propene- nitrile (μg/L) (34215) n-Propyl- benzene (μg/L) (77224) 1,1,1,2-Tetra- chloro- ethane (μg/L) (77562) 1,1,2,2-Tetra- chloro- ethane (μg/L) (34516) Tetra- chloro- ethene (μg/L) (34475) Tetra- chloro- methane (μg/L) (32102) Tetra- hydro- furan (μg/L) (81607) 1,2,3,4-Tetra- methyl- benzene (μg/L) (49999 1,2,3,5-Tetra- methyl- benzene (μg/L) (50000) Tribr

met

(μg

(32

SUS2-1 <1 <0.04 <0.03 <0.09 <0.1 <0.06 <2 <0.2 <0.2 <0SUS2-2 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-3 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-4 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-5 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-6 <1 <.04 <.03 <.09 <.1 <.06 26 <.2 <.2 <SUS2-7 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-8 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-9 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <

SUS2-10 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-11 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-12 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-13 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-14 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-15 <1 <.04 <.03 <.09 M <.06 <2 <.2 <.2 <SUS2-16 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-17 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-18 <1 <.04 <.03 <.09 <.1 <.06 E1 <.2 <.2 <SUS2-19 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-20 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-22 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-23 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-24 <1 <.04 <.03 <.09 <.1 <.06 E2 <.2 <.2 <SUS2-25 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-26 <1 <.04 <.03 <.09 <.1 <.06 E1 <.2 <.2 <SUS2-27 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-28 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-29 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <SUS2-30 <1 <.04 <.03 <.09 <.1 <.06 <2 <.2 <.2 <
Appendix 10-2. Analyses for volatile organic compounds (VOCs), samples from lower Tertiary aquifers--Continued

Well 

number

1,2,4-

Trichlorobenzene 

(μg/L) 

(34551)

1,1,1-

Trichloroethane 

(μg/L) 

(34506)

1,1,2-

Trichloroethane 

(μg/L) 

(34511)

Trichloroethene 

(μg/L) 

(39180)

Trichlorofluoromethane 

(μg/L) 

(34488)

Trichloromethane 

(μg/L) 

(32106)

1,2,3-

Trichloropropane 

(μg/L) 

(77443)

1,1,2-

Trichloro1,2,2-

trifluoroethane 

(μg/L) 

(77652)

1,2,3-

Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-

Trimethylbenzene 

(μg/L) 

(77222)

Tri

be

(

(7

SUS2-1 <0.2 <0.03 <0.06 <0.04 <0.09 <0.02 <0.2 <0.06 <0.1 U SUS2-2 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-3 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-4 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-5 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 U SUS2-6 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-7 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-8 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-9 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U 

SUS2-10 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-11 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-12 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 U SUS2-13 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-14 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-15 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS2-16 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-17 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS2-18 <.2 <.03 <.06 <.04 <.09 E.03 <.2 <.06 <.1 <.06 SUS2-19 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-20 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-22 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-23 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-24 <.2 <.03 <.06 <.04 <.09 E.05 <.2 <.06 <.1 <.06 SUS2-25 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06 SUS2-26 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 U SUS2-27 <.2 <.03 <.06 <.04 <.09 .65 <.2 <.06 <.1 U SUS2-28 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS2-29 <.2 <.03 <.06 <.04 <.09 <.05 <.2 <.06 <.1 <.06 SUS2-30 <.2 <.03 <.06 <.04 <.09 <.02 <.2 <.06 <.1 <.06