U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008–5232

Prepared in cooperation with the West Dakota Water Development District and the 

South Dakota Department of Environment and Natural Resources

Water-Quality Effects and Characterization of Indicators of 

Onsite Wastewater Disposal Systems in the East-Central 

Black Hills Area, South Dakota, 2006–08
Cover photograph. Water samples being collected from monitoring well completed in the Spearfish Formation located downgradient 

from onsite wastewater disposal systems (photograph by Larry D. Putnam, U.S. Geological Survey).
Water-Quality Effects and Characterization 

of Indicators of Onsite Wastewater 

Disposal Systems in the East-Central Black 

Hills Area, South Dakota, 2006–08

By Larry D. Putnam, Galen K. Hoogestraat, and J. Foster Sawyer

Prepared in cooperation with the West Dakota Water Development District and the 

South Dakota Department of Environment and Natural Resources

Scientific Investigations Report 2008–5232

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

This and other USGS information products are available at http://store.usgs.gov/

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Box 25286, Denver Federal Center

Denver, CO 80225

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1-888-ASK-USGS

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Putnam, L.D., Hoogestraat, G.K., and Sawyer, J.F., 2008, Water-quality effects and characterization of indicators of 

onsite wastewater disposal systems in the east-central Black Hills area, South Dakota, 2006–08: U.S. Geological 

Survey Scientific Investigations Report 2008–5232, 115 p. 
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Description of Study Areas .................................................................................................................3

Physiography and Hydrologic Conditions................................................................................3

Hydrogeologic Setting ................................................................................................................3

Previous Investigations........................................................................................................................7

Acknowledgements..............................................................................................................................7

Methods of Study...........................................................................................................................................7

Indicators of Onsite Wastewater Disposal System Influence ......................................................7

Sampling Sites, Onsite Wastewater Disposal Systems, and Stratigraphic Units....................12

Collection, Processing, and Analysis of Water Samples .............................................................20

Quality Assurance/Quality Control...................................................................................................20

Physical Properties, Major Ions, Nutrients, and Selected Trace Elements ....................22

Nitrogen and Oxygen Isotope Ratios in Nitrate....................................................................22

Microbiological Indicators.......................................................................................................22

Organic Wastewater Compounds...........................................................................................23

Water-Quality Effects, Indicators, and Isotopes of Nitrate...................................................................24

Physical Properties, Major Ions, Nutrients, and Selected Trace Elements..............................24

Alluvial Setting............................................................................................................................24

Spearfish Setting .......................................................................................................................24

Minnekahta Setting ...................................................................................................................27

Precambrian Setting .................................................................................................................27

Ground Water....................................................................................................................27

Surface Water...................................................................................................................27

Nitrogen and Oxygen Isotope Ratios in Nitrate.............................................................................31

Microbiological Indicators................................................................................................................31

Ground Water.............................................................................................................................32

Surface Water............................................................................................................................32

Organic Wastewater Compounds....................................................................................................33

Ground Water.............................................................................................................................33

Surface Water............................................................................................................................33

Characterization of Indicators of Onsite Wastewater Disposal Systems ..........................................35

Alluvial Setting.....................................................................................................................................35

Spearfish Setting.................................................................................................................................43

Minnekahta Setting ............................................................................................................................44

Precambrian Setting ..........................................................................................................................46

Ground Water.............................................................................................................................46

Surface Water............................................................................................................................50

Relation Between Onsite Wastewater Disposal System Density and Nitrate

Concentrations ......................................................................................................................51
iv

Evaluation of Onsite Wastewater Disposal System Indicators...................................................52

Summary........................................................................................................................................................55

References....................................................................................................................................................58

Supplemental Information..........................................................................................................................63

Figures

1–7. Maps showing—

1. Locations of study areas and sampling sites, and generalized geology....................4

2. Locations of sampling sites, onsite wastewater disposal systems and

stratigraphic units for study area 1 in the alluvial setting...........................................12

3. Locations of sampling sites, onsite wastewater disposal systems and

stratigraphic units for study area 2 in the Spearfish and Minnekahta 

setting ..................................................................................................................................16

4. Locations of sampling sites, onsite wastewater disposal systems and

stratigraphic units for study area 3 in the Minnekahta and Precambrian 

settings ................................................................................................................................17

5. Locations of sampling sites, onsite wastewater disposal systems and

stratigraphic units for study area 4 in Precambrian setting.......................................18

6. Locations of sampling sites, onsite wastewater disposal systems and

stratigraphic units for study area 5 in Precambrian setting.......................................19

7. Locations of sampling sites, onsite wastewater disposal systems and

stratigraphic units for study area 6 in the Precambrian setting................................21

8–10. Graphs showing—

8. Nitrogen and oxygen isotope ratios for nitrate in ground-water samples in 

relation to the isotopic composition of nitrate sources ..............................................31

9. Nitrogen and oxygen isotope ratios for nitrate in surface-water samples in 

relation to the isotopic composition of nitrate sources ..............................................32

10. Summary of microbiological indicator detections in ground water for 

downgradient samples grouped by hydrogeologic setting........................................33

11–15. Boxplots showing—

11. Dissolved nitrite plus nitrate concentrations in ground-water samples 

collected from downgradient wells grouped by hydrogeologic setting...................38

12. Dissolved chloride concentrations in ground-water samples collected 

from downgradient wells grouped by hydrogeologic setting ....................................39

13. Dissolved bromide concentrations in ground-water samples collected 

from downgradient wells grouped by hydrogeologic setting ....................................40

14. Dissolved chloride/bromide ratios in ground-water samples collected 

from downgradient wells grouped by hydrogeologic setting ....................................41

15. Dissolved boron concentrations in ground-water samples collected 

from downgradient wells grouped by hydrogeologic setting ....................................42

16. Graph showing time-series concentrations of dissolved chloride, sodium, sulfate, 

and nitrite plus nitrate at sites 17, 21, and 22 .........................................................................45
v

17–18. Maps showing–

17. Distribution of dissolved nitrite plus nitrate concentrations in study area 5, 

June–July 2007...................................................................................................................48

18. Distribution of dissolved chloride concentrations in study area 5, 

June–July 2007...................................................................................................................49

19. Graph showing relation between median dissolved nitrite plus nitrate concentration 

and density of onsite wastewater disposal systems in dry hydrologic conditions .........53

Tables

1. Annual precipitation at Rapid City Regional Airport from 2000 through 2007.....................3

2. Monthly precipitation at Rapid City Regional Airport from April 2006 through 

December 2007..............................................................................................................................3

3. Stratigraphic and hydrogeologic units in the study area. .....................................................5

4. Significance of wastewater indicators and water-quality criteria, standards, or 

recommended limits.....................................................................................................................8

5. Sampling sites in study area in four settings.........................................................................13

6. Summary of physical properties and concentrations of major ions, nutrients, and

selected trace elements for ground water in the alluvial setting.......................................25

7. Summary of physical properties and concentrations of major ions, nutrients, and 

selected trace elements for ground water in the Spearfish setting..................................26

8. Summary of physical properties and concentrations of major ions, nutrients, and 

selected trace elements for ground water in the Minnekahta setting..............................28

9. Summary of physical properties and concentrations of major ions, nutrients, and 

selected trace elements for ground water in the Precambrian setting............................29

10. Summary of physical properties and concentrations of major ions, nutrients, and 

selected trace elements for surface water in the Precambrian setting...........................30

11. Summary of microbiological indicator results for ground water .......................................34

12. Summary of microbiological indicator results for surface water ......................................35

13. Summary of organic wastewater compound detections in ground water.......................36

14. Summary of organic wastewater compound detections in surface water......................37

15. Spearman’s rank correlations for dissolved nitrite plus nitrate, chloride, chloride/

bromide ratio, and boron for 11 downgradient samples in the alluvial setting................43

16. Spearman’s rank correlations for dissolved nitrite plus nitrate, chloride, chloride/

bromide ratio, and boron for 17 downgradient samples in the Spearfish setting............43

17. Spearman’s rank correlations for dissolved nitrite plus nitrate, chloride, chloride/

bromide ratio, and boron for 33 downgradient samples in the Minnekahta setting .......44

18. Spearman’s rank correlations for dissolved nitrite plus nitrate, chloride, chloride/

bromide ratio, and boron for 39 downgradient samples in the Precambrian setting......46

19. Density of onsite wastewater disposal systems and median dissolved 

nitrite plus nitrate concentrations for selected site groupings ..........................................52

20. Field-equipment blank results for selected physical properties, major ions, 

nutrients, and selected trace elements ..................................................................................64
vi

 21. Relative percent difference between field replicate and environmental samples 
vii

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

cubic foot (ft3

) 0.02832 cubic meter (m3) 

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

foot per year (ft/yr) 0.3048 meter per year (m/yr)

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

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

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

Hydraulic conductivity

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

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

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

 °F=(1.8×°C)+32

Vertical coordinate information is referenced to the North Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).
viii

Abbreviations and Acronyms

AIR atmospheric nitrogen

Cl:Br ratio of dissolved chloride concentration to dissolved bromide concentration

C. perfringens Clostridium perfringens

col/100 mL colonies per 100 milliliters

E. coli Escherichia coli

GIS geographical information system

HHCB hexahydrohexamethylcyclopentabenzofuran

MCL Maximum Contaminant Level

MDL method detection limit

mpn most probable number

MRL minimum reporting level

N nitrogen

N2 nitrogen gas

NH3 ammonia

NH4 ammonium

NO2+NO3 nitrite plus nitrate expressed as milligrams per liter as nitrogen

NOAA National Oceanic and Atmospheric Administration

NWQL National Water Quality Laboratory

OWC organic wastewater compound

OWDS onsite wastewater disposal systems

OWML Ohio Water Microbiology Laboratory

QA/QC quality assurance/quality control

RPD relative percent difference

RSD relative standard deviation

RSIL Reston Stable Isotope Laboratory

SD DENR South Dakota Department of Environment and Natural Resources

SMCL Secondary Maximum Contaminant Level

USGS U.S. Geological Survey

VSMOW Vienna Standard Mean Ocean Water

δ15N isotope ratio of 15N to 14N compared to a standard ratio

δ18O isotope ratio of 18O to 16O compared to a standard ratio
Water-Quality Effects and Characterization of Indicators 

of Onsite Wastewater Disposal Systems in the East 

Central Black Hills Area, South Dakota, 2006–08

By Larry D. Putnam1, Galen K. Hoogestraat1, and J. Foster Sawyer2

1

U.S. Geological Survey.

2

South Dakota Department of Environment and Natural Resources.

Abstract

Onsite wastewater disposal systems (OWDS) are used 

extensively in the Black Hills of South Dakota where many 

of the watersheds and aquifers are characterized by fractured 

or solution-enhanced bedrock with thin soil cover. A study 

was conducted during 2006–08 to characterize water-quality 

effects and indicators of OWDS. Water samples were collected 

and analyzed for potential indicators of OWDS, including 

chloride, bromide, boron, nitrite plus nitrate (NO2

+NO3), 

ammonia, major ions, nutrients, selected trace elements, isotopes of nitrate, microbiological indicators, and organic wastewater compounds (OWCs). The microbiological indicators 

were fecal coliforms, Escherichia coli (E. coli), enterococci, 

Clostridium perfringens (C. perfringens), and coliphages. 

Sixty ground-water sampling sites were located either downgradient from areas of dense OWDS or in background areas 

and included 25 monitoring wells, 34 private wells, and 

1 spring. Nine surface-water sampling sites were located on 

selected streams and tributaries either downstream or upstream 

from residential development within the Precambrian setting. 

Sampling results were grouped by their hydrogeologic setting: 

alluvial, Spearfish, Minnekahta, and Precambrian. 

Mean downgradient dissolved NO2

+NO3 concentrations 

in ground water for the alluvial, Spearfish, Minnekahta, and 

Precambrian settings were 0.734, 7.90, 8.62, and 2.25 milligrams per liter (mg/L), respectively. Mean downgradient 

dissolved chloride concentrations in ground water for these 

settings were 324, 89.6, 498, and 33.2 mg/L, respectively. 

Mean downgradient dissolved boron concentrations in ground 

water for these settings were 736, 53, 64, and 43 micrograms 

per liter (μg/L), respectively. Mean dissolved surface-water 

concentrations for NO2

+NO3, chloride, and boron for downstream sites were 0.222 mg/L, 32.1 mg/L, and 28 μg/L, respectively. 

Mean values of δ15N and δ18O (isotope ratios of 14N to 15N 

and 18O to 16O relative to standard ratios) for nitrate in groundwater samples were 10.4 and -2.0 per mil (‰), respectively, 

indicating a relatively small contribution from synthetic fertilizer and probably a substantial contribution from OWDS. The 

surface-water sample with the highest dissolved NO2

+NO3 

concentration of 1.6 mg/L had a δ15N value of 12.36 ‰, which 

indicates warm-blooded animals (including humans) as the 

nitrate source.

Fecal coliforms were detected in downgradient ground 

water most frequently in the Spearfish (19 percent) and 

Minnekahta (9.7 percent) settings. E. coli was detected most 

frequently in the Minnekahta (29 percent) and Spearfish 

(13 percent) settings. Enterococci were detected more frequently than other microbiological indicators in all four settings. Fecal coliforms and E. coli were detected in 73 percent 

and 95 percent of all surface-water samples, respectively. 

Enterococci, coliphages (somatic), and C. perfringens were 

detected in 50, 70, and 50 percent of surface-water samples, 

respectively. 

Of the 62 OWC analytes, 12 were detected only in 

environmental samples, 10 were detected in at least one environmental and one blank sample (not necessarily companion 

pairs), 2 were detected only in blank samples, and 38 were 

not detected in any blank, environmental, or replicate sample 

from either ground or surface water. Eleven different organic 

compounds were detected in ground-water samples at eight 

different sites. The most frequently occurring compound was 

DEET, which was found in 32 percent of the environmental 

samples, followed by tetrachloroethene, which was detected in 

20 percent of the samples. For surface-water samples, 

16 organic compounds were detected in 9 of the 10 total samples. The compound with the highest occurrence in surfacewater samples was camphor, which was detected in 

50 percent of samples. 

The alluvial setting was characterized by relatively low 

dissolved NO2

+NO3 concentrations, detection of ammonia 

nitrogen, and relatively high concentrations of major ions, 

particularly sulfate and sodium, compared to other settings. 

Nitrogen and oxygen isotope results indicated that denitrification was occurring in water from a few wells. Chloride 

concentrations at downgradient sites were substantially higher 

than background concentrations. 
2 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

The Spearfish setting was characterized by consistently 

high dissolved NO2

+NO3 concentrations—75 percent of samples had concentrations higher than 5 mg/L—and relatively 

frequent detections of microbiological indicators and OWCs. 

Nitrogen isotope results indicated that the source of nitrogen 

from two of the five sites probably included some nitrogen 

from synthetic sources mixed with nitrogen from warmblooded animals. Although concentrations of chloride, boron, 

and bromide generally were higher than background concentrations, the variability in the concentrations in proximal areas 

complicated interpretations from these OWDS indicators. 

In the Minnekahta setting, most indicator concentrations 

in downgradient samples were higher than background concentrations, and correlations between indicators in the same 

sample were strong. Mean, median, and maximum dissolved 

NO2

+NO3 concentrations were 8.62, 7.42, and 24.3 mg/L, 

respectively, for the Minnekahta setting—the highest of the 

four hydrogeologic settings. Nitrogen isotope results indicated 

that the probable source was warm-blooded animals (predominantly from OWDS effluents) in 17 of 23 samples. OWCs 

were detected in more than one-half of the samples, and 

E. coli and coliphages were detected more frequently in the 

Minnekahta setting than in any other hydrogeologic setting.

Effects of OWDS varied among the different Precambrian 

study areas, but water-quality evidence indicated that water 

samples from the Precambrian wells generally were not as 

affected by anthropogenic influences as water samples from 

other hydrogeologic settings. However, the direct comparison 

of OWDS indicator results to other settings is questionable, 

as all of the wells in the Precambrian setting were previously 

established private drinking-water sources in contrast to the 

strategically placed monitoring wells used in the other three 

settings. Maximum dissolved NO2

+NO3 concentrations for 

three sites in study area 4 that ranged from 5.06 to 8.11 mg/L 

probably included OWDS effects in the Precambrian setting. 

Microbiological indicators detected include fecal coliforms 

and E. coli, each detected in 2.6 percent of ground-water 

samples. No OWCs were detected in any of the six samples. 

Differences in chemical indicators of OWDS effects between 

upstream and downstream surface-water sites were not always 

evident; however, statistical tests on dissolved chloride, dissolved boron, fecal coliforms, and E. coli data indicated that 

results for upstream sites were significantly different than 

those for downstream sites. 

Densities of OWDS were calculated for nine estimated 

contributing areas to the ground water near selected sites in 

the Spearfish, Minnekahta, and Precambrian settings. A positive correlation between downgradient dissolved NO2

+NO3

concentration and OWDS density was observed. The analysis 

indicated a 90-percent chance that dissolved NO2

+NO3 concentrations would be between 3 and 8 mg/L in an area with an 

OWDS density of 150 per square mile. 

On the basis of background concentrations, dissolved 

NO2

+NO3 concentrations higher than 2 mg/L were assumed to 

potentially indicate anthropogenic influence. Concentrations 

were higher than 2 mg/L in 75 percent of the ground-water 

samples, higher than 5 mg/L in 50 percent, and higher than 

10 mg/L in 18 percent. Dissolved chloride concentrations, 

when compared to a mean background concentration of 

14.6 mg/L, were excellent indicators of anthropogenic influence. Surface-water indicator results may give more insight 

into the effects of residential activities in general, as direct 

runoff probably contributes a greater proportion of the indicator load than do OWDS effluents. 

Introduction

Onsite wastewater disposal systems (OWDS) are used 

extensively in the Black Hills of South Dakota where many 

of the watersheds and aquifers are characterized by fractured 

or solution-enhanced bedrock with thin soil cover. Population 

growth in the Black Hills area has been rapid and has occurred 

in unincorporated areas where OWDS commonly are used for 

wastewater treatment. Many of these developing areas are in 

recharge areas for important Black Hills aquifers or within 

high-value watersheds. A better understanding of the potential effects of OWDS on ground- and surface-water quality in 

the Black Hills area is needed to assess land use in relation to 

water resources. Typically, OWDS include a septic tank and a 

drain field that commonly are referred to collectively as a septic system. OWDS can include other components and designs.

A cooperative study between the U.S. Geological Survey 

(USGS), the West Dakota Water Development District, and 

the South Dakota Department of Environment and Natural 

Resources (SD DENR) was begun in 2006 to characterize 

water-quality effects and indicators of OWDS. The general approach for this study was to select study areas in the 

east-central Black Hills underlain by fractured or carbonate 

bedrock. Shallow unconsolidated deposits overlying bedrock 

also were included in the study. The study focused on areas 

that included substantial numbers of OWDS. 

The first phase of the study included identification of 

appropriate sampling sites where substantial numbers of 

OWDS existed, installation of monitoring wells (SD DENR 

Geological Survey Program), and collection and analysis of 

water samples for screening constituents that were relatively 

inexpensive indicators of potential OWDS influence. On the 

basis of these results, additional samples were collected and 

analyzed for a more detailed set of indicators and waterquality constituents. Samples were collected and analyzed in 

2006, 2007, and early 2008.

Purpose and Scope

The purpose of this report is to present water-quality 

effects and characterization of indicators of OWDS for both 

ground water and surface water in six small study areas that 

represent a range of hydrogeologic settings in the Black Hills 

area. Samples were collected during 2006–08 from 60 groundwater sites and 9 surface-water sites. Information presented 
Introduction 3

includes physical properties, major ions, nutrients, selected 

trace elements, isotopes of nitrate (nitrogen and oxygen), 

microbiological indicators, and organic wastewater compounds. The scope of sampling emphasized fractured and 

carbonate bedrock sites. Study areas were limited to settings 

where installation of monitoring wells was feasible or existing 

wells were available.

Description of Study Areas

Six study areas, in the east-central part of the Black Hills, 

included Rapid City and surrounding communities through 

Piedmont on the north, Silver City on the west, Hill City on 

the southwest, and Green Valley on the east (fig. 1). Sampling 

sites were located in the Elk, Boxelder, Rapid, and Spring 

Creek watersheds.

Physiography and Hydrologic Conditions

The Black Hills uplift formed as an elongated dome that 

trends north-northwest and is about 120 miles (mi) long and 

60 mi wide (Dewitt and others, 1986). Land-surface altitudes 

range from approximately 4,000 to 5,500 feet (ft) in study 

areas 4, 5, and 6 on the west to about 3,000 ft in study area 1 

on the east. The highest altitude in the Black Hills (7,242 ft) is 

Harney Peak, which is about 2 mi west of study area 6. Study 

area 1 is characterized by rolling prairies and bottom lands 

along Rapid Creek. Study areas 2 and 3 are characterized by 

pine covered ridges on the west side and open areas with less 

relief on the east. Study areas 4, 5, and 6 are characterized by 

high relief and predominantly pine and spruce forests.

Average annual precipitation (1931–98) ranges from 

about 21 inches in study area 5 to about 16 inches in study 

area 3 (Driscoll and others, 2000). Below-normal precipitation 

has prevailed in the study areas since 2000. Annual precipitation at National 

Oceanic and Atmospheric Administration (NOAA) station 

396937 at Rapid 

City Regional Airport (table 1), which 

is about 3 mi east of 

study area 1 (fig. 1), 

has been below normal (1970–2000) 

for the last 8 years. 

Monthly precipitation during the 

study sampling 

period generally 

was near normal 

or below normal 

except for August 

2007 (table 2).

Table 1. Annual precipitation at Rapid 

City Regional Airport from 2000 through 

2007.

[National Oceanic and Atmospheric Administration, 2000–2007]

Year

Annual 

precipitation 

Departure from 

normal 

(1970–2000)

(inches)

2000 15.03 -1.61

2001 14.29 -2.35

2002 10.27 -6.37

2003 10.97 -5.67

2004 13.16 -3.48

2005 14.41 -2.23

2006 11.72 -4.92

2007 12.61 -4.03

Table 2. Monthly precipitation at Rapid City Regional 

Airport from April 2006 through December 2007.

[National Oceanic and Atmospheric Administration, 2006–07]

Month

Monthly 

precipitation

Departure 

from normal 

(1970–2000)

(inches)

April 2006 2.09 0.23

May 2006 1.82 -1.14

June 2006 .93 -1.90

July 2006 .76 -1.27

August 2006 1.76 .15

September 2006 2.00 .90

October 2006 .34 -1.03

November 2006 .47 -.14

December 2006 .01 -.40

January 2007 .12 -.25

February 2007 .79 .33

March 2007 .49 -.54

April 2007 1.32 -.54

May 2007 2.93 -.03

June 2007 .96 -1.87

July 2007 1.20 -.83

August 2007 2.82 1.21

September 2007 .83 -.27

October 2007 .61 -.76

November 2007 .03 -.58

December 2007 .51 .10

Hydrogeologic Setting

Uplift at the end of the Cretaceous period followed by 

erosion created the dome-like structure and geomorphology 

of the Black Hills. Stratigraphic units (table 3) exposed in the 

Black Hills (Strobel and others, 1999) grouped by geologic 

age (Erathem; fig. 1) illustrate the general hydrogeologic setting. Metamorphic and igneous rocks of Early Proterozoic and 

Late Archean age are exposed in the central core of the Black 

Hills; stratigraphic layers of Paleozoic, Mesozoic, and Cenozoic age are exposed on its flanks. The outcrops of Paleozoic 

and Mesozoic rocks form concentric rings surrounding the 

Precambrian core and dip radially outward. Unconsolidated 

Tertiary deposits of Cenozoic age overlie these units and are 

sparser in the central core of the Black Hills because of erosion. The geologic framework and aquifer characteristics of 

the Black Hills are described in detail in Driscoll and others 

(2002). Selected stratigraphic units are discussed with more 

detail for each study area in the section of this report titled 

“Sampling Sites, Onsite Wastewater Disposal Systems, and 

Stratigraphic Units.”

The Paleozoic interval includes the Minnekahta, Minnelusa, Madison, and Deadwood aquifers, which are 4 of the 

5 major aquifers in the Black Hills (Driscoll and others, 2002). 
4 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Study area 6 

(see figure 7)

Study area 4 

(see figure 5)

Study area 5 

(see figure 6)

Study area 2 

(see figure 3)

Study area 3 

(see figure 4)

103°40’ 103°30’ 103°20’ 103°10’

44°10’

44°00’

43°50’

EXPLANATION

Age of geologic formations (modified 

 from Strobel and others, 1999)

Cenozoic

Mesozoic

Paleozoic

Early Proterozoic and Late Archean

Study area

Surface-water sampling site

Ground-water sampling site

T. 3 N.

T. 1 N.

T. 2 N.

T. 1 S.

T. 2 S.

R. 4 E. R. 5 E. R. 6 E. R. 7 E. R. 8 E.

90

79

44

16

385

40 16A

244

87

Boxelder

Prairie

Elk

Rapid

Creek

Spring

Creek

Battle

Creek

Creek

Reno Gulch

Pactola

Reservoir

Sheridan

 Lake

Rapid

 City

Palmer

Black Hawk

Piedmont

Hill

City

44

385

Base from U.S. Geological Survey digital data, 1977, 1:100,000

Rapid City, Office of City Engineer map, 2005, 1:18,000 

Universal Transverse Mercator projection

Zone 13

Creek

Rapid

City

Regional

Airport

Study area 1

(see figure 2)

0 42 8 MILES

0 42 8 KILOMETERS

Figure 1. Locations of study areas and sampling sites, and generalized geology.

Creek

Creek

Green

Valley

Silver

City

SOUTH DAKOTA

Area shown

Black Hills

Figure 1. Locations of study areas and sampling sites, and generalized geology.
Introduction 5

Table 3. Stratigraphic and hydrogeologic units in the study area.

[From Strobel and others, 1999; thickness of units in study area were modified from Long and Putnam, 2002]

Erathem System Hydrogeologic 

unit

Stratigraphic 

unit Description of units

Cenozoic

Quaternary

Unconsolidated

units

Qa ALLUVIUM—Moderately to well-sorted clay, silt, sand, and gravel deposited by 

streams. Thickness ranges from 0 to 50 feet. A local aquifer where saturated.

Qc

COLLUVIUM—Poorly to well-sorted, massive to stratified, clast-free to boulder 

rubble and talus produced by mass wasting. Thickness ranges from 0 to 50 feet. 

The hydrogeologic character of colluvial material varies considerably depending on 

the degree of sorting and primary type of material. Generally not an aquifer even if 

saturated.

Qg

GRAVEL DEPOSITS—Moderately sorted, heterogeneous, generally stratified, clay, 

silt, sand, and well-rounded gravel of paleochannels, pediments, and stream terraces 

along former flood plains. Thickness ranges from 0 to 50 feet. A local aquifer where 

saturated.

Tertiary

Tg

GRAVEL DEPOSITS—Heterogeneous gravel deposits derived primarily from igneous- and metamorphic-rock sources of the central Black Hills. Clast size predominantly pebble or cobble, but ranges from clay to boulder. Thicknesses range from 

0 to 30 feet. A local aquifer where saturated.

White River aquifer Tw

WHITE RIVER GROUP—Consists of the Brule and Chadron Formations. Sandstone, 

claystone, and siltstone with channel fillings and limestone lenses. Thickness ranges 

from 0 to 300 feet. A minor aquifer where saturated.

Mesozoic

Cretaceous

Cretaceous sequence

 confining unit Kps

PIERRE SHALE TO SKULL CREEK SHALE, UNDIFFERENTIATED—Confining 

unit of shale, limestone, and sandstone containing the following formations listed 

with their thickness in feet: Pierre Shale, 1,200–2,700; Niobrara Formation, 80–300; 

Carlile Shale, 350–750; Greenhorn Formation, 225–380; Belle Fourche Shale, 

150–850; Mowry Shale, 125–230; Newcastle Sandstone, 0–150; and Skull Creek 

Shale, 150–270 (modified from DeWitt and others, 1986). Where present, the Newcastle Sandstone is an aquifer if saturated.

Inyan Kara aquifer Kik

INYAN KARA GROUP—Sandstone and other clastic rocks of the Fall River Formation and Lakota Formation. The Fall River Formation is 100–200 feet thick 

consisting of brown to reddish-brown fine-grained sandstone, thin–bedded at the top 

and massive at the bottom. The Lakota Formation is 35–700 feet thick consisting 

of yellow, brown, and reddish-brown massive to thin-bedded, sandstone, pebble 

conglomerate, siltstone, and claystone with local limestone, coal, and fossiliferous 

layers. A major regional aquifer.

Jurassic

Jurassic 

sequence

 semiconfining unit

Ju

MORRISON FORMATION TO GYPSUM SPRING FORMATION, UNDIFFERENTIATED—Semiconfining unit consisting of interbedded shale, sandstone, and 

gypsum of the following formations listed with their thickness in feet: Morrison 

Formation, 0–220; Unkpapa Sandstone, 0–225; Sundance Formation, 250–450; and 

Gypsum Spring Formation, 0–45. Sandstones of the Sundance Formation contain 

locally productive aquifers where saturated.

Triassic Spearfish 

confining unit TrPs

SPEARFISH FORMATION—Red silty shale interbedded with friable, red sandstone 

and siltstone, and sparse limestone layers. Lower portion contains massive gypsum. 

Thickness ranges from 375 to 800 feet.

Paleozoic

Permian

Minnekahta aquifer Pmk

MINNEKAHTA LIMESTONE—Fine-grained, purple to gray laminated limestone. 

Thickness ranges from 25 to 65 feet (modified from DeWitt and others, 1989). Unit 

is locally fractured and brecciated owing to solution collapse (Gries and Martin, 

1985). A major aquifer in the study area.

Opeche 

confining unit Po OPECHE SHALE—Red siltstone and sandy shale, with local gypsum and anhydrite 

near the top. Thickness ranges from 25 to 150 feet.

Minnelusa 

aquifer

PPm

MINNELUSA FORMATION—Variably colored but generally yellow to red crossstratified sandstone, limestone, dolomite, and shale of the Minnelusa Formation. 

Thickness ranges from 375 to 1,175 feet, most commonly between 400 and 

750 feet. Anhydrite is common at depth, generally within the upper 200 feet of the 

formation. Where anhydrite has dissolved, collapse-formed secondary permeability 

creates the most productive aquifer. Interbedded limestone and shale in the lower 

part of the formation forms a confining zone. A major regional aquifer.

Pennsylvanian
6 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Table 3. Stratigraphic and hydrogeologic units in the study area—Continued.

[From Strobel and others, 1999; thickness of units in study area were modified from Long and Putnam, 2002]

Erathem System Hydrogeologic 

unit

Stratigraphic 

unit Description of units

MADISON (PAHASAPA) LIMESTONE AND ENGLEWOOD FORMATION—Gray 

to buff and lavender limestone that is locally dolomitic. The Madison Limestone is 

250 to 1,000 feet thick, and the Englewood Formation is 30 to 60 feet thick (modified 

Mississippian

and Devonian Madison aquifer MDme from DeWitt and others, 1989). Generally massive, upper third is karstic with caves, 

solution collapse, and enlarged conduits resulting in extensive secondary permeability and creating the potentially most productive aquifer in the Black Hills (Kyllonen 

and Peter, 1987). The lower portion of the Madison Limestone and the Englewood 

Paleozoic

Formation form a lower confining zone (Greene, 1993). A major regional aquifer.

Ordovician and

Cambrian

Ordovician

sequence 

semiconfining

unit

Ou

WHITEWOOD FORMATION AND WINNIPEG FORMATION—Undifferentiated 

semiconfining unit consists of limestone and dolomite of the Whitewood Formation, 

thickness ranges from 0 to 235 feet, and of shale with interbedded siltstone of the 

Winnipeg Formation, thickness ranges from 0 to 150 feet (modified from DeWitt and 

others, 1986). The units are found in the northern and western part of the study area.

Deadwood

aquifer OCd

DEADWOOD FORMATION—Brown to light-gray glauconitic sandstone, shale, limestone, and local basal conglomerate. Thickness ranges from 0 to 500 feet. A major 

aquifer in the study area.

HARNEY PEAK GRANITE—Pink and tan coarse-grained pegmatitic muscovite granXh ite. Characterized geochemically from other granites in the area by high concentrations of boron, beryllium, lithium, and uranium.

UNDIFFERENTIATED METAMORPHOSED PHYLLITE AND SCHIST—Locally 

ean

Xush carbonaceous and tuffaceous. Geochemical and geophysical signatures vary with the 

tuffaceous zones having an anomalously high copper concentration and a magnetic 

Late Arch

Precambrian

nature.

ic and 

Precambrian igneous and

metamorphic

XWui UNDIFFERENTIATED IGNEOUS ROCKS—Geochemical signature and geophysical 

nature vary depending on protolith.

Early Proterozo

units

XWgw METAMORPHOSED GRAYWACKE—Primarily a medium to dark gray siliceous 

mica schist and impure quartzite.

UNDIFFERENTIATED METAMORPHOSED SEDIMENTARY DEPOSITS—

Includes conglomerate, quartz sandstone, siltstone, and dolomite protoliths. Parts are 

XWus characterized geochemically by anomalous uranium, chromium, and gold concentrations and other parts by anomalous gold, silver, and arsenic concentrations. The latter 

zones are magnetic in nature.
Methods of Study 7

The Mesozoic interval includes the Inyan Kara aquifer, the 

other major aquifer. The upper part of the Madison aquifer is 

contained in karstic limestone with caves, solution collapse, 

and enlarged conduits resulting in the potentially most productive aquifer in the Black Hills. The Minnekahta aquifer also is 

contained in fractured and brecciated limestone; however, the 

average thickness of the Minnekahta aquifer in the study area 

is about 40 ft, whereas the thickness of Madison aquifer is 

about 400 ft. The Minnelusa aquifer is contained in fractured 

sandstone with intervening layers of shale and limestone. The 

Inyan Kara and Deadwood aquifers are contained in predominantly sandstone with some secondary permeability from 

fracturing. 

Previous Investigations

An overview of the issues related to OWDS in the Black 

Hills area and previous work is presented in Sawyer (2006). 

In this water-quality investigation, three residential OWDS, 

a municipal wastewater treatment facility, and sources of 

recharge and discharge for the Madison aquifer were examined 

for downgradient effects relative to upgradient background 

sites. A nitrate mass-balance model also was applied to estimate critical minimum gross acreage per developed lot using 

site-specific aquifer parameters. Two other investigations (Bad 

Moccasin, 1986; Mott and others, 2004) documented water 

quality in the Green Valley housing developments (study 

area 1). Substantial water-quality data, including values of 

nitrite plus nitrate (NO2

+NO3), chloride, Escherichia coli

(E. coli), total coliform bacteria, and major ions, as well as 

a detailed characterization of the ground-water levels and 

flow direction, are documented in these reports. Analyses of 

nutrients and fecal coliforms in Spring Creek below Sheridan 

Lake (study area 6) are summarized in Schwickerath (2004) 

and Swanson (2004). 

Acknowledgements

In addition to monitoring-well construction, SD DENR 

Geological Survey Program employees provided substantial support for this study in selecting sites, obtaining access 

to sites for well construction, and developing the sampling 

plan. The Rapid Creek Preservation Association provided 

assistance in identifying potential sampling sites in the Rapid 

Creek watershed. Residents in the Precambrian hydrogeologic 

settings were very helpful in providing access to wells for 

collecting samples. The Rapid City Onsite Inspection Program 

provided assistance with locations of OWDS.

Methods of Study

Water samples were collected from each sampling site at 

least once during the study period, 2006–08. For the first site 

visit, samples were analyzed for screening wastewater indicators, which included the chemical water-quality constituents 

chloride, bromide, boron, NO2

+NO3, and ammonia, as well as 

the microbiological indicators E. coli and fecal coliforms. For 

sites that had sample values higher than background values for 

these screening wastewater indicators, a more detailed suite 

of chemical and microbiological analyses was performed on 

subsequent sampling visits. The detailed suite included major 

ions and trace elements, isotopes of nitrate, organic wastewater 

compounds (OWCs), and additional microbiological indicators 

(enterococci, Clostridium perfringens, and coliphages). The 

60 ground-water sampling sites included monitoring and 

private wells and 1 spring. Nine surface-water sampling sites 

were located on selected streams and tributaries within the 

study area.

Indicators of Onsite Wastewater Disposal 

System Influence

Selection of the wastewater indicators was based on the 

potential use of the constituent to characterize OWDS effects. 

Table 4 summarizes the significance of indicators and waterquality criteria relevant to this study. Thomas (2000) reported 

the concentration of chloride in septic system effluent to be in 

the range of 37–101 milligrams per liter (mg/L). A study to 

evaluate the effects of water softeners on septic tanks (Kinsley 

and others, 2005) compared chloride and sodium concentrations in samples of septic tank effluent for systems not receiving water-softener backwash (11 samples) to concentrations 

for systems receiving water-softener backwash (110 samples). 

The median chloride concentrations for septic systems not 

receiving water-softener backwash was 125 mg/L, whereas the 

median chloride concentrations for septic systems receiving 

water-softener backwash was 1,537 mg/L. The median sodium 

concentrations for septic systems not receiving water-softener 

backwash was 160 mg/L, and the median sodium concentration for septic systems receiving water-softener backwash was 

644 mg/L. In areas where halite is not naturally occurring, 

natural waters have lower chloride to bromide ratios (Cl:Br) 

than do waters affected by anthropogenic sources such as road 

salt, domestic sewage, and water-softener backwash (Francy 

and others, 2004). Thomas (2000) reported Cl:Br ratios in the 

range of 30–600 for sewage. Vengosh and Pankratov (1998)

reported slightly larger Cl:Br ratios (410–873, mean of 732) 

for domestic wastewater in Israel. 

Boron is present in household products (such as detergents and cleaning powders), and ground-water concentrations 

higher than background values may be the result of OWDS. 

Boron concentrations in treated sewage were 500 micrograms 

per liter (μg/L), and concentrations in the center of a subsurface plume were as high as 410 μg/L in a sand and gravel aquifer with background values of about 50 μg/L (LeBlanc, 1984). 

Medians of the maximum plume concentrations of chloride 

and boron from seven septic tank plumes were 107 mg/L and 

267 μg/L, respectively (Minnesota Pollution Control Agency, 
Table 4. Significance of wastewater indicators and water-quality criteria, standards, or recommended limits. [Modified from Hamilton and Howells, 1996; All standards and recommended limits are from U.S. Environmental Protection Agency (2008) unless otherwise noted; --, not avaimum Contaminant Level; CaCO3, calcium carbonate; mg/L, milligrams per liter; MCL, Maximum Contaminant Level; μg/L, micrograms per liter, OWDS, onsite wastewater dis

coliform] Constituent or property Significance as wastewater indicator Significance in drinking-water supplies 

Specific conductance Water with anthropogenic influences (septic effluent, road salts, water-softener backwash) has an ionic strength that usually is far greater than that of the natural environment; therefore, the presence of these contaminants in a water body increases the overall specific conductance of the water (Chen, 1988). A measure of the ability of water to conduct an electrical current; 

perature. Magnitude depends on concentration, kind, and degreof dissolved constituents; can be used to determine the approxition of dissolved solids. Values are reported in microsiemens pe25 degrees Celsius. 

pH -- A measure of the hydrogen ion concentration; pH of 7.0 indicates 

tion, pH values smaller than 7.0 indicate acidity, pH values largindicate alkalinity. Water generally becomes more corrosive wipH; however, excessively alkaline water also may be corrosive. 

Temperature -- Affects the usefulness of water for many purposes. Generally, user

uniformly low temperature. Temperature of ground water tends increasing depth to the aquifer. 

Dissolved oxygen Used to indicate oxic state in relation to transformation processes such as nitrifica- tion. The degradation of organic sewage material by microorganisms consumes oxygen and can result in decreased dissolved–oxygen concentrations (Hyer, 2006). Required by higher forms of aquatic life for survival. Measuremen

oxygen are used widely in evaluations of the biochemistry of stOxygen is supplied to ground water through recharge and by mthrough unsaturated material above the water table (Hem, 1985

Acid neutralizing capacity (alkalinity1) -- A measure of the capacity of unfiltered water to neutralize acid. In 

ral waters, alkalinity is produced by the dissolved carbon dioxid

bonate and carbonate. Typically expressed in milligrams per lit

Calcium plus magnesium -- Causes most of the hardness and scale-forming properties of wate

soap-consuming characteristics of water; results in formation osoap is added. May cause deposition of scale in boilers, water hpipes. Water that has a hardness less than 61 mg/L is consideremg/L, moderately hard; 121–180 mg/L, hard; and more than 18hard (Heath, 1983). 

Sodium plus potassium Abnormally large concentrations may indicate natural brines, industrial brines, or sewage. Median sodium concentrations for septic systems not receiving water- softener backwash was 160 mg/L compared to median sodium concentrations for septic systems receiving water-softener backwash of 644 mg/L (Kinsley and others, 2005). Large concentrations may limit use of water for irrigation and indu

in combination with chloride, give water a salty taste. 

Sulfate Natural waters have highly variable sulfate concentrations; may be a product of the denitrification process in reducing environments (Clark and Fritz, 1997). Sulfates of calcium and magnesium form hard scale. Large concen

fate have a laxative effect on some people and, in combination give water a bitter taste. 

Chloride High concentrations used as wastewater indicator owing to low background levels in natural non-halite environments. Sewage and septic effluent have typical chloride concentrations in the range of 37–101 mg/L (Thomas, 2000; Hyer, 2006) Water- softener backwash can dramatically increase chloride concentrations in OWDS effluents to more than 1,500 mg/L (Kinsley and others, 2005). Large concentrations increase the corrosiveness of water and, in c

sodium, give water a salty taste. 
Table 4. Significance of wastewater indicators and water-quality criteria, standards, or recommended limits.—Continued[Modified from Hamilton and Howells, 1996; All standards are from U.S. Environmental Protection Agency (2008) unless otherwise noted; --, not available; SMCL, Secondary CaCO3, calcium carbonate; mg/L, milligrams per liter; MCL, Maximum Contaminant Level; μg/L, micrograms per liter, OWDS, onsite wastewater disposal system; E. coli, Esc

Constituent

or property Significance as wastewater indicator Significance in drinking-water supplies 

Fluoride -- Reduces incidence of tooth decay when optimum fluoride concentra

present in water consumed by children during the period of tooth Potential health effects of long-term exposure to elevated fluoride tions include dental and skeletal fluorosis (U.S. Environmental PrAgency, 1994).

Bromide Bromide data frequently are coupled with chloride data because the ratio of the 

chloride concentration to the bromide concentration (Cl:Br) is a good indicator of sewage. Bromide concentrations in sewage are not elevated relative to those in the natural environment, so sewage that enters a water body should cause an increase in the Cl:Br (Hyer, 2006). Typical Cl:Br of sewage is 30–600 (Thomas, 2000). 

Not known to be essential in human or animal diet. Not known to ha

ecologic significance when it occurs in small concentrations typicfresh waters of the United States.

Silica (as SiO2) -- Forms scale in pipes and boilers and may form deposits on blades o

bines. Inhibits deterioration of zeolite-type water softeners. 

Nitrite (mg/L as N) Nitrite typically occurs in water from fertilizers and is found in sewage and wastes 

from humans and farm animals. Commonly formed as an intermediate product in bacterially mediated nitrification and denitrification of ammonia and other organic nitrogen compounds.

An acute health concern at certain levels of exposure. Concentration

1.0 mg/L, as nitrogen, may be injurious when used in feeding infEnvironmental Protection Agency, 2008).

Nitrite plus nitrate 

(mg/L as N)

Concentrations greater than local background levels may indicate pollution by feedlot runoff, sewage, or fertilizers. Nitrogen from OWDS effluent is usually oxidized from ammonia to nitrite and nitrate in an oxic environment such as a drain 

field (Sawyer, 2006). OWDS effluent concentrations can be variable; reported in range of 24–150 mg/L as nitrogen (Waller and others, 1987). Morgan and others (2007) used an average nitrogen concentration in OWDS effluent of 61 mg/L. 

Concentrations greater than 10 mg/L, as nitrogen, may be injurious 

feeding infants (U.S. Environmental Protection Agency, 2008).

Ammonia Sources include decomposition of animal and plant proteins, agricultural and urban 

runoff, and effluent from wastewater treatment plants. Inorganic nitrogen in OWDS effluent is predominantly in the ammonia form (Sawyer, 2006). 

Plant nutrient that can cause unwanted algal blooms and excessive p

when present at elevated levels in water bodies. 

Phosphorus, orthophosphate Sources are human and animal wastes, fertilizers, and domestic detergents. Dense algal blooms or rapid plant growth can occur in waters rich in 

A limiting nutrient for eutrophication because it is typically in sh

Boron Boron can be an effective tracer of sewage sources because natural water concentrations are relatively low. Boron is used primarily in cleaning powders, which 

eventually are flushed into OWDS. Water samples with elevated concentrations of boron generally indicate contributions of sewage (Neal and others, 1998).

Essential to plant growth, but may be toxic to crops when present in 

concentrations in irrigation water. Sensitive plants show damage tion water contains more than 670 μg/L and even tolerant plants maged when boron exceeds 2,000 μg/L. The recommended limit is long-term irrigation on sensitive crops (U.S. Environmental Prote1986).

Iron Potential electron source for denitrification process (Clark and Fritz, 1997). Forms rust-colored sediment; stains laundry, utensils, and fixtures re

Objectionable for food and beverage processing. Can promote gr

tain kinds of bacteria that clog pipes and well openings.

Manganese Potential electron source for denitrification process (Clark and Fritz, 1997). Causes gray or black stains on porcelain, enamel, and fabrics. Can p

growth of certain kinds of bacteria that clog pipes and wells.
Table 4. Significance of wastewater indicators and water-quality criteria, standards, or recommended limits.—Continued [Modified from Hamilton and Howells, 1996; All standards are from U.S. Environmental Protection Agency (2008) unless otherwise noted; --, not available; SMCL, Secondary CaCO , calcium carbonate; mg/L, milligrams per liter; MCL, Maximum Contaminant Level; μg/L, micrograms per liter, OWDS, onsite wastewater disposal system; E. coli, Esc

3 Constituent or property Significance as wastewater indicator Significance in drinking-water supplies 

δ15N and δ18O Fecal coliform, E. coli Enterococci Clostridium perfringens Coliphage (somatic or F-specific) Organic wastewater compounds Used to track probable source of nitrogen in nitrate. Differences can be observed in the isotopic composition of synthetic fertilizers, mineralized fertilizers, natural organic matter, and septic system effluent. As nitrogen is consumed and broken down by increasing trophic levels, 15N becomes more enriched relative to the atmospheric isotopic composition (Clark and Fritz, 1997). Detection is indicative of human or animal fecal waste. Normally inhabit the bowels of animals and humans, but also are found in soil, vegetation, and surface water. Enterococci are more persistent in water than coli- forms. They provide a different assessment of the transport of fecal contamina- tion in ground water than coliforms because of their different shape and survival rate (U.S. Geological Survey, 2005). A spore-forming bacterium that is present in human and animal feces and may be useful as a surrogate for stress-resistant organisms. Clostridium perfringens is mainly an indicator of contamination from point sources, as well as a conserva- tive tracer of past fecal contamination (U.S. Geological Survey, 2005). Viral indicators that infect and replicate in coliform bacteria, primarily E. coli. Coliphage are found in high numbers in sewage and may be better than bacterial indicators to represent the survival and transport of viruses in the environment. Two main groups of coliphage are detected in separate tests: (1) Somatic coliphage infect the outer cell wall of its host and requires a laboratory strain, like E. coli CN-13, for detection, and (2) F-specific (also called male-specific) coliphage infect the F-pili (produced at temperatures above 25 degrees Celsius) of its host and requires a labora- tory strain, like E. coli F-amp, for detection (U.S. Geological Survey, 2005). Detection is indicative of human and animal wastes; sources include pharmaceutical products, human and veterinary antibiotic compounds, agricultural herbicides, household and industrial compounds, hydrocarbons, and sterol compounds2. -- Not necessarily a health threat in itself; it is used to indicate whether 

tially harmful bacteria may be present. Fecal coliform and E. coli whose presence indicates that the water may be contaminated witanimal wastes. Disease-causing microbes (pathogens) in these wadiarrhea, cramps, nausea, headaches, or other symptoms. These ppose a special health risk for infants, young children, and people compromised immune systems (U.S. Environmental Protection A

Linked to health problems including urinary tract infections, bactere

endocarditis, diverticulitis, and meningitis. Of the 23 distinct speclis is one of the leading causes of nosocomial (hospital-acquired) such as bacteremia, endocarditis, and urinary tract infections (We

Similar health risks as those described in fecal coliform and E. coli s

--(3) 

1In natural waters, acid neutralizing capacity (ANC) and alkalinity are synonymous (Stumm and Morgan, 1996). 2See table 32 in “Supplemental Information” section for detailed information regarding primary uses of organic wastewater compounds. 3See U.S. Environmental Protection Agency (2008) for list of organic wastewater compound MCLs and potential health effects for specific compounds. 
Methods of Study 11

1999). Hyer (2006) reported median chloride and boron concentrations of 72 mg/L and 236 μg/L, respectively, from six 

raw sewage and septic system samples. 

Nitrite and nitrate originate from a variety of anthropogenic sources, including OWDS, synthetic fertilizers, animal 

wastes, explosives, and decomposing organic matter (Clark 

and Fritz, 1997). Several microbiologically mediated processes control the nitrogen cycle in the subsurface environment, cycling the initial form of nitrogen from organic matter 

or fertilizers to ammonia (NH3

) and ammonium (NH4

+

), then 

to nitrite (NO2

-

) and nitrate (NO3

-

), and finally either back 

to organic matter by plant consumption or transformed to 

nitrogen gas (N2

) through the denitrification process (Sawyer, 

2006). Nitrogen concentration in OWDS effluent is highly 

varied. Waller and others (1987) reported concentrations that 

ranged from 24 to 150 mg/L as total inorganic nitrogen (N) 

for a time-series data set of two OWDS effluents in Florida. 

Extensive studies that document nitrate transport in a sand and 

gravel aquifer in La Pine, Oregon, are available at 

http://or.water.usgs.gov/projs_dir/or186/ (accessed July 17, 

2008). These investigators used an average nitrogen concentration in OWDS effluent of 61 mg/L to calculate nitrogen loading near La Pine, Oregon (Morgan and others, 2007). 

Ratios of the stable isotopes of nitrogen (15N and 14N) 

and oxygen (18O and 16O) in nitrate can provide insight on the 

sources and fate of nitrate in ground water. The additional neutrons in 15N and 18O result in atomic weights for these isotopes 

that are different from those of the more predominant isotopes 

14N and 16O. Molecules with different atomic weights have 

different reaction rates, which leads to isotope partitioning 

or fractionation (Clark and Fritz, 1997). Stable isotope ratios 

are expressed in “delta notation,” which compares the ratio 

between the heavy and light isotopes of a sample to that of a 

reference standard. Delta values are expressed as a difference, 

in parts per thousand, or per mil (‰), from the value reference 

standard. The nitrogen isotope ratio of a sample written in 

delta notation is:

 

δ N = (1)

N

N - N

N

N

N

×1,000 15

sample

15

14

sample

15

14

standard

15

14

standard

‰ AIR

The oxygen isotope ratio of a sample written in delta notation 

is expressed by replacing 15N and 14N with 18O and 16O, respectively, and AIR with VSMOW in equation 1.

A sample with a δ15N value of 10 ‰ is enriched by 

10 parts per thousand (1 percent) in the heavier isotope of 

nitrogen relative to the standard. Similarly, a sample with 

a δ18O value of -5 ‰ is depleted by 5 parts per thousand 

(0.5 percent) in the heavier isotope of oxygen relative to the 

oxygen isotope ratio standard. Values for nitrogen are reported 

in per mil relative to atmospheric nitrogen (AIR), and values 

for oxygen are reported in per mil relative to Vienna Standard 

Mean Ocean Water (VSMOW).

The manufacture of fertilizer results in very little fractionation; therefore, δ15N of synthetic mineralized fertilizer is 

about 0 ‰ (Clark and Fritz, 1997). Organic nitrogen fixation 

of soil organic matter has a minor fractionation effect on 15N, 

resulting in enrichment of about 3–7 ‰. The complex fractionation of 15N through the food web results in enriched δ15N 

values in the waste from animals of about 10–20 ‰ (Clark and 

Fritz,1997). 

Biologically formed nitrate generally is depleted in 18O 

because only one oxygen atom comes from atmospheric 

oxygen with the remaining two molecules coming from water 

(Hollocher, 1984), which is considerably more depleted in 18O. 

The oxygen in synthetic fertilizer primarily is from atmospheric oxygen. δ18O values for nitrate vary according to the 

δ18O of local ground waters. In the study area, δ18O values in 

ground water range from about -12 ‰ in the south and east to 

about -14 ‰ in the north (Naus and others, 2001).

Comparison of δ15N and δ18O also can be a useful tool to 

indicate denitrification. Denitrification results in increases in 

δ15N and δ18O in the remaining nitrate (Bottcher and others, 

1990). The process of denitrification requires a reduced substrate to provide the energy needed by nitrate reducing bacteria 

(Clark and Fritz, 1997). Dissolved organic carbon supplied 

by septic system plumes can be a potential source of energy. 

Other viable substrates include sulfide minerals in the aquifer 

itself. 

The screening microbiological indicators E. coli and fecal 

coliforms are bacteria that are found only in human and animal 

wastes (U.S. Environmental Protection Agency, 2008). Microbiological indicators are not very mobile in the ground water 

flowing through porous material, because they are removed 

by straining, die-off, and adsorption. The migration of these 

bacteria is greatly reduced relative to the velocity of the flowing water. Thus, in medium-grained sand or finer materials, 

coliform organisms generally do not penetrate more than a few 

meters through the material. However, in fractured or solutionenhanced rocks, local water velocities can be high, allowing 

for transport distances on the order of kilometers (Freeze and 

Cherry, 1979). Enterococci bacteria are more persistent in 

ground water than coliforms and provide a different assessment of fecal contamination because of their different shape 

and survival rate (U.S. Geological Survey, 2005). 

Clostridium perfringens (C. perfringens) is a sporeforming bacterium that is present in human and animal wastes, 

but in lower concentrations than standard bacterial indicators. 

Because C. perfringens spores are resistant to environmental 

stress, they may be useful surrogates for other stress-resistant 

pathogens (U.S. Geological Survey, 2005). 

Coliphages are viruses that infect the bacterium E. coli

and are indicators of transport of viruses in ground water. 

Coliphages have been shown to be relatively immobile in 

granular geologic materials (Freeze and Cherry, 1979). Viruses 

are not a normal part of the fecal flora. They occur in infected 

persons, and they appear in septic tank effluent intermittently, 

in varying numbers, reflecting the combined infection and 

carrier status of OWDS users (Berg, 1973). Viruses are less 

affected by filtration than bacteria (Bechdol and others, 1994). 

Viruses can be both retained and inactivated in soil; however, 
12 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

they also can be retained but not inactivated. If not inactivated, 

viruses can accumulate in soil and subsequently be released 

as a result of changing conditions, such as prolonged peak 

OWDS flows or heavy rains. The result could be contamination of ground water. Soil factors that decrease virus survival 

include warm temperatures, low moisture content, and high 

organic content. Soil factors that increase retention include 

small particle size, high moisture content, low organic content, 

and low pH (U.S. Environmental Protection Agency, 2002a). 

The U.S. Environmental Protection Agency’s ground-water 

rule gives States the discretion to specify use of E. coli, enterococci, or one of the coliphage types (somatic or F-specific, 

table 4) to monitor for potential presence of fecal contamination in ground water sources (U.S. Environmental Protection 

Agency, 2006).

Many organic compounds used in or produced by household, industrial, and agricultural activities 

are soluble and resistant to conventional 

wastewater treatment processes, and 

have been shown to occur in wastewater 

discharges to natural waters (Sando and 

others, 2006). The presence of specific 

human-related OWCs such as fecal indicators, caffeine, detergent metabolites, 

cholesterol, and pharmaceuticals might 

indicate ground-water contamination from 

OWDS. The transport distance of OWCs 

is greatly retarded as the effluent travels 

through granular materials, but is less 

inhibited when the effluents move through 

large fractures with less filtration. A 

percentage of OWCs can be consumed or 

degraded to other compounds by bacteria 

that exist in the drain field from which 

the chemical originated (Miller and Ortiz, 

2007). For this study, the presence (detection) of microbiological indicators or 

OWCs was considered indicative of possible OWDS effluents. No greater importance was placed on one particular OWC 

or microbiological indicator over another, 

unless deemed necessary by qualityassurance/quality-control results.

Sampling Sites, Onsite 

Wastewater Disposal Systems, 

and Stratigraphic Units

Presentation of sampling sites is 

organized by six study areas (figs. 2–7 and 

table 5). Presentation of sampling results 

is grouped by four hydrogeologic settings. 

The alluvial setting included seven monitoring wells completed in the alluvium 

along Rapid Creek. The Spearfish setting 

included five wells completed in the Spearfish Formation and 

one well completed in upgradient alluvium. The Minnekahta 

setting included 11 wells completed in the Minnekahta Limestone. The Precambrian setting included 30 private wells completed in Precambrian rocks, 5 wells completed in alluvium 

or gravel deposits overlying Precambrian rocks, and 1 spring. 

Nine surface-water sites were all in the Precambrian setting. 

Study area 1 represented the alluvial setting. Study area 2 

represented sampling sites for the Spearfish setting and part of 

the Minnekahta setting. Study area 3 included the remaining 

sampling sites for the Minnekahta setting and one site that was 

grouped in the Precambrian setting. Study areas 4, 5, and 6 

represented the Precambrian setting. 

Locations of potential OWDS were from two geographic 

information data sets. The city of Rapid City mapped locations of OWDS as part of their septic system inspection efforts 

Qa

Kps

Qg

Qa

Qg

Kps

Kps

23 22 24

26

15 14

27 25

13

1

3

4

5

2

6

7

103°08’ 103°07’ 103°06’

44°02’

44°01’

T. 1 N.

44

Rapid Creek

EXPLANATION

Stratigraphic units (modified from Strobel and others, 1999)

Alluvium

Gravel deposits

Pierre Shale to Skull Creek Shale, undifferentiated

Ground-water sampling site (number is site number in table 5)

Approximate location of OWDS (Rapid City Onsite Inspection Program,

 written commun., 2008)

R. 8 E. Base from U.S. Geological Survey 

digital data, 1977, 1:100,000 

Universal Transverse Mercator projection

Zone 13

0 0.5 1 MILE

0 0.5 1 KILOMETER

Figure 2. Locations of sampling sites, onsite wastewater disposal systems (OWDS), 

and stratigraphic units for study area 1 in the alluvial setting (see figure 1).

Kps

Qg

Qa

Figure 2. Locations of sampling sites, onsite wastewater disposal systems (OWDS), 

and stratigraphic units for study area 1 in the alluvial setting (see figure 1).
Methods of Study 13

Table 5. Sampling sites in study area in four settings.

[NGVD 29, National Geodetic Vertical Datum of 1929; Site type: MON, monitoring well; PRV, private well; STR, stream. Sample types collected: SC, screening 

constituents, MT, major ions and selected trace metals; IN, isotopes of nitrate; OWC, organic wastewater compounds; BI, additional biological indicators; --, no data. 

Shading denotes background sites]

Site 

number

(figs. 

2–7)

Station 

identification

number

Station name Other 

identifier

Site

type

Land 

surface 

altitude

 (feet 

above 

NGVD 29)

Well 

depth 

(feet)

Average 

water 

level 

below 

land 

surface 

(feet)

Number 

of 

sample 

sets 

collected

Sample

types

collected

Well 

completion 

stratigraphic 

unit (see 

table 3)

Setting

Study area 1 (alluvial setting)

1 440214103072601 1N 8E23BABD GV1 MON 3,045 19.5 5.1 1 SC Qa Alluvial.

2 440144103075301 1N 8E23CBCB GV6 MON 3,052 27.0 11.5 2 SC, MT, IN, BI Qa Alluvial.

3 440204103064101 1N 8E23ADAA GV7 MON 3,032 15.0 5.5 1 SC Qa Alluvial.

4 440150103064001 1N 8E24CBBB GV3 MON 3,027 18.0 7.6 3 SC, MT,IN, BI Qa Alluvial.

5 440147103064901 1N 8E23DABD GV2 MON 3,032 22.8 11.5 3 SC, MT, IN, OWC, BI Qa Alluvial.

6 440141103064001 1N 8E23DADD GV4 MON 3,020 14.9 5.4 3 SC, MT, IN, OWC, BI Qa Alluvial.

7 440131103070401 1N 8E23DCDB GV5 MON 3,030 20.0 13.7 1 SC Qa Alluvial.

Study area 2 (Spearfish and Minnekahta setting)

8 441400103235801 3N 6E 9DBAC MS-W MON 3,578 51.0 45.7 1 SC, MT, BI Pmk Minnekahta.

9 441401103235101 3N 6E 9DABC1 MS-E MON 3,555 79.0 42.9 4 SC, MT, IN, OWC, BI Pmk Minnekahta.

10 441353103232001 3N 6E10CBDD PM3 MON 3,490 40.0 23.5 3 SC, MT,IN, BI TrPs Spearfish.

11 441352103232601 3N 6E10CCBA PM1 MON 3,507 40.0 27.9 4 SC, MT, IN, OWC, BI TrPs Spearfish.

12 441349103232301 3N 6E10CCAC PM2 MON 3,505 40.0 26.0 4 SC, MT, IN, OWC, BI TrPs Spearfish.

13 441303103220601 3N 6E14CBDD1 SS1 MON 3,496 45.0 38.6 3 SC, MT,IN, BI TrPs Spearfish.

14 441302103220602 3N 6E14CBDD2 SS2 MON 3,496 50.0 36.9 3 SC, MT, IN, OWC, BI TrPs Spearfish.

15 441302103220501 3N 6E14CBDD3 SS4 MON 3,496 325.0 5.6 2 SC, MT,IN, BI Pmk Minnekahta.

16 441222103221201 3N 6E23BCDC SC MON 3,572 28.0 18.8 2 SC, MT,IN, BI Qa Spearfish.

17 441215103213301 3N 6E23DBAC SES MON 3,537 155.0 48.3 6 SC, MT, IN, OWC, BI Pmk Minnekahta.

Study area 3 (Minnekahta and Precambrian setting)

18 440709103174101 2N 7E20ADCD1 QRY MON 3,500 55.5 49.7 3 SC, MT,IN, BI Pmk Minnekahta.

19 440644103182901 2N 7E20CCDA HV-N MON 3,598 51.8 49.3 3 SC, MT,IN, BI Pmk Minnekahta.

20 440642103182901 2N 7E20CCDD HV-S MON 3,597 59.8 57.7 2 SC, MT,IN, BI Pmk Minnekahta.

21 440451103180201 1N 7E 5ABBD BP-N MON 3,470 68.6 58.7 6 SC, MT, IN, OWC, BI Pmk Minnekahta.

22 440446103175701 1N 7E 5ABDB BP-S MON 3,480 67 62.0 5 SC, MT, IN, OWC, BI Pmk Minnekahta.

23 440143103163001 1N 7E21DACA WW-N MON 3,555 67.2 63.4 3 SC, MT, IN, OWC, BI Pmk Minnekahta.

24 435823103160901 1S 7E10CDAA NY MON 3,578 136.0 117.7 1 SC Pmk Minnekahta.

25 435938103220501 1S 6E 2ABBD VG MON 4,228 14.0 10.6 1 SC Qa Precambrian.

Study area 4 (Precambrian setting)

26 440510103261701 2N 6E31DCAA -- PRV 4,385 -- -- 2 SC, MT, IN, OWC, BI PCMB1 Precambrian.

27 440504103262201 2N 6E31DCAB -- PRV 4,180 10 -- 2 SC, MT, IN, OWC, BI Qa Precambrian.

28 440459103265001 2N 6E31CCAD -- PRV 4,330 60 -- 1 SC PCMB1 Precambrian.

29 440454103262301 1N 6E 6ABAB -- PRV 4,300 20 -- 1 SC, MT,IN, BI Qa Precambrian.

30 440452103262201 1N 6E 6ABAB2 -- PRV 4,300 -- -- 1 SC, MT,IN, BI PCMB1 Precambrian.

31 440452103255101 1N 6E 5BBBA -- PRV 4,262 20 -- 1 SC Qa Precambrian.

32 440447103254901 1N 6E 5BBCA -- PRV 4,265 -- -- 1 SC Qa Precambrian.

33 440442103260201 1N 6E 6AADC -- PRV 4,255 -- -- 1 SC PCMB1 Precambrian.

34 440416103253401 1N 6E 5CACD -- PRV 4,220 -- -- 1 SC PCMB1 Precambrian.

35 440324103250501 1N 6E 8DCAA -- PRV 4,100 35 -- 1 SC PCMB1 Precambrian.

36 440318103233901 1N 6E 9DDBD -- SPR 4,150 -- -- 2 SC, MT, IN, OWC, BI PCMB1 Precambrian.

37 06411900 Rapid Creek above 

Johnson Siding 

below Pactola 

Dam, SD

RC1 STR 4,305 -- -- 2 SC, MT, IN, OWC, BI -- Precambrian.

38 06412000 Rapid Creek at Big 

Bend at Rapid 

City, SD

RC3 STR 4,110 -- -- 2 SC, MT, IN, OWC, BI -- Precambrian.

39 440245103301501 1N 5E15 -- PRV 5,010 165 -- 1 SC, MT PCMB1 Precambrian.

40 440218103302101 1N 5E22BAAA -- PRV 5,040 -- -- 1 SC PCMB1 Precambrian.

41 440205103300501 1N 5E22AC -- PRV -- -- -- 1 SC PCMB1 Precambrian.
14 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Table 5. Sampling sites in study area in four settings.—Continued

[NGVD 29, National Geodetic Vertical Datum of 1929; Site type: MON, monitoring well; PRV, private well; STR, stream. Sample types collected: SC, screening 

constituents, MT, major ions and selected trace metals; IN, isotopes of nitrate; OWC, organic wastewater compounds; BI, additional biological indicators; --, no data. 

Shading denotes background sites]

Site 

number

(figs. 

2–7)

Station 

identification

number

Station name Other 

identifier

Site

type

Land 

surface 

altitude

 (feet 

above 

NGVD 29)

Well 

depth 

(feet)

Average 

water 

level 

below 

land 

surface 

(feet)

Number 

of 

sample 

sets collected

Sample

types

collected

Well 

completion 

stratigraphic 

unit (see 

table 3)

Setting

Study area 5 (Precambrian setting)

42

43

44

45

46

47

48

49

50

51

52

53

54

440505103335401

440505103335402

440505103335001

440505103334801

440504103335701

440503103335501

440502103334701

440501103335201

440501103335101

440459103334801

440458103334802

440458103334801

440457103334101

2N 5E31CDAD

2N 5E31CDAD2

2N 5E31DCBD

2N 5E31DCBB

2N 5E31CDAD3

2N 5E31CDAA

2N 5E31DCCA3

2N 5E31DCCB

2N 5E31DCBC

2N 5E31DCCD

2N 5E31DCCA

2N 5E31DCCA2

2N 5E31DCDB

--

--

--

--

--

--

--

--

--

--

--

--

--

PRV

PRV

PRV

PRV

PRV

PRV

PRV

PRV

PRV

PRV

PRV

PRV

PRV

4,620

4,615

4,615

4,605

4,645

4,635

4,635

4,675

4,655

4,675

4,650

4,690

4,638

-- --

50 --

-- --

83 --

92 --

103 --

90 --

-- --

80 --

-- --

205 --

-- --

105 --

1

1

3

1

1

1

2

1

1

1

1

1

1

SC

SC

SC, MT, IN, OWC, BI

SC

SC

SC

SC, MT, IN, OWC, BI

SC

SC

SC

SC

SC

SC

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Study area 6 (Precambrian setting)

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

435753103320401

435707103320101

435703103314101

435654103312101

435645103310601

435637103321201

435630103311901

435619103331101

435720103273401

06406960

06406760

435436103352201

06406700

435628103324600

06406920

1S 5E21ADB

1S 5E21B2

1S 5E21ACAB

1S 5E21ADCD

1S 5E21DADD

1S 5E21CCB (2)

1S 5E21DDC

1S 5E29BBDA

Unnamed South 

Tributary above 

Sheridan Lake 

near Hill City, 

SD

Sheridan Lake 

Tributary near 

Calumet Ridge 

near Keystone, 

SD

Reno Gulch near 

Hill City, SD

Reno Gulch at 

Highway 385 

near Hill City, 

SD

Spring Creek at 

Oreville near 

Hill City, SD

Spring Creek above 

Mitchell Lake 

near Hill City, 

SD

Spring Creek above 

Sheridan Lake 

near Keystone, 

SD

--

--

--

--

--

--

--

--

CALUMET2

CALUMET1

RENO2

RENO1

SPCR1

SPCR2

SPCR3

PRV

PRV

PRV

PRV

PRV

PRV

PRV

PRV

STR

STR

STR

STR

STR

STR

STR

4,880

4,960

4,930

4,840

4,800

4,800

4,880

4,900

4,750

4,600

5,350

5,070

5,355

4,875

4,650

410 --

360 --

-- --

230 --

-- --

62 --

105 --

90 --

-- --

-- --

-- --

-- --

-- --

-- --

-- --

1

1

1

1

1

1

1

1

3

3

3

3

2

2

2

SC

SC

SC

SC

SC

SC

SC

SC

SC

SC

SC

SC

SC, MT, IN, OWC, BI

SC, MT, IN, OWC, BI

SC, MT, IN, OWC, BI

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

PCMB1

--

--

--

--

--

--

--

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

Precambrian.

1

Wells completed in units within the Precambrian system (table 3) are listed as PCMB. 
Methods of Study 15

(Rapid City On-Site Inspection Program, written commun., 

2008). SD DENR inventoried OWDS locations in 2002 that 

were upgradient from the Paleozoic outcrops (SD DENR 

Source Water Assessment and Protection Program, written commun., 2008). OWDS upgradient from sites in the 

Spearfish setting were mapped from aerial photographs as part 

of this study.

Monitoring wells in study area 1 (sites 1–7) were 

completed in the alluvium (Qa) along Rapid Creek (fig. 2) 

and range in depth from about 15 to 27 ft (table 5). Screened 

intervals at the bottom of the wells ranged in length from 

10 to 20 ft. Average water levels ranged from 5.1 to 13.7 ft 

below land surface. The underlying and adjacent bedrock is 

the Pierre Shale (Kps). Cattermole (1972) indicated that adjacent stratigraphic units are the Pierre Shale and the Niobrara 

Formation. Ground-water flow directions in the study area 

are towards Rapid Creek, with an easterly direction in the 

western part of the study area (Mott and others, 2004). Sites 1 

and 2 are upgradient from most OWDS and were considered 

background wells for the alluvial setting. Sites 3–7 are located 

downgradient from OWDS. Previous reports on the hydrogeology of the area include Coker (1981), Hafi (1983), and Musa 

(1984). Land use in the study area is a suburban development 

of about 240 households in an area of approximately 

0.5 square mile (mi2

; Mott and others, 2004). The surrounding area consists primarily of ranchland and sparser suburban 

development. 

The monitoring well at site 16 (fig. 3), completed in the 

alluvium overlying the Minnelusa Formation (PPm) in Stagebarn Canyon, is 28 ft deep (table 5). The average water level 

was 18.8 ft below land surface. Very few OWDS are upgradient from site 16, which was considered a background well for 

the Spearfish setting.

Five monitoring wells in study area 2 (sites 10–14, 

fig. 3) were completed in the Spearfish Formation (TrPs) and 

range in depth from 40 to 50 ft (table 5; Spearfish setting). 

Average water levels ranged from 23.5 to 38.6 ft below land 

surface. The screened interval at the bottom of the well ranged 

in length from 10 to 20 ft and penetrated the weathered upper 

part of the Spearfish Formation. Gravel deposits overlying the 

screened interval were about 20 to 30 ft thick.

Land use near sites 10–14 in study area 2 includes dense 

suburban development with OWDS that are on the gravel 

deposits (Qg) upgradient from the wells. Sites 10–12 are in 

the town of Piedmont, which does not have a central sewer 

system. Some small grazing areas and domestic animals are 

present in the area. Sites 13 and 14 are downgradient from 

dense residential housing with OWDS. The Spearfish setting 

includes a few small commercial establishments.

Four monitoring wells in study area 2 (sites 8, 9, 15, 

and 17, fig. 3) were completed in the Minnekahta Limestone 

(Pmk; Minnekahta setting) and range in depth from 51 to 

325 ft (table 5). Average water levels ranged from 5.6 to 48.3 ft 

below land surface. The screened interval ranged in length 

from 33 to 40 ft and fully penetrated the Minnekahta Limestone. Sites 8, 9, and 17 are downgradient from numerous 

OWDS that are on the outcrop of the Minnekahta Limestone. 

Site 15 is a Minnekahta monitoring well downgradient from 

an area with very few OWDS on the outcrop and was considered a background site. 

Land use in the Minnekahta setting in study area 2 is 

residential housing with OWDS. The outcrop of the Minnekahta Limestone forms a ponderosa-pine covered ridge on the 

flank of the Black Hills that stands in contrast to the overlying Spearfish Formation, which is more erodible and has less 

relief and fewer trees. Soil cover overlying the fractured Minnekahta Limestone generally is thin. Areas adjacent to housing 

developments are undeveloped forest land.

Seven monitoring wells in study area 3 (sites 18–24, 

fig. 4) were completed in the Minnekahta Limestone (Pmk) 

and range in depth from about 52 to 136 ft (table 5; Minnekahta setting). Average water levels ranged from 49.3 to 117.7 ft 

below land surface. The screened interval, which ranged in 

length from 27 to 42 ft, fully penetrated the Minnekahta Limestone. Sites 18–23 are downgradient from areas with numerous 

OWDS on the outcrop of the Minnekahta Limestone. Site 24 is 

downgradient from the outcrop of the Minnekahta Limestone 

where no OWDS are present and was considered a background 

well for the Minnekahta setting. Land use is similar to that 

described for the Minnekahta setting for study area 2.

The monitoring well at site 25 (fig. 4), completed in the 

alluvium along Victoria Gulch overlying Precambrian rocks, 

is 14 ft deep and was grouped with the Precambrian setting. 

The average water level was 10.6 ft below land surface. Some 

OWDS are upgradient from this site.

Six private wells in study area 4 adjacent to Rapid Creek 

(sites 26, 28, 30, and 33–35, fig. 5) are completed in Precambrian rocks, and known well depths are 60 feet or less 

(table 5). The area has considerable topographic relief, and 

general ground-water flow directions were assumed to follow the topography towards Rapid Creek. Numerous OWDS 

are in the areas adjacent to Rapid Creek where metamorphic 

rocks are exposed, and some of the OWDS are on shallow 

gravel deposits overlying the metamorphic rocks. Four private 

wells in study area 4 (sites 27, 29, 31, and 32) are completed 

in alluvium adjacent to Rapid Creek and generally less than 

20 ft deep. Ground-water flow directions were assumed to be 

towards Rapid Creek. 

Site 36 is a spring that discharges within the Precambrian setting (fig. 5 and table 5). Springflow was steady at 

about 12 gallons per minute (gal/min) during the study. The 

spring is about 100 to 150 ft lower in altitude than the group of 

upgradient OWDS north of the spring. Most of these OWDS 

are on gravel deposits overlying the metamorphic rocks. Sites 

37 and 38 are streamflow sampling sites on Rapid Creek near 

the upper and lower ends of the stream reach where numerous 

OWDS are located.

Land use in study area 4 primarily is residential development but includes small commercial establishments along the 

major roads. Small areas primarily upgradient from site 36 

where the topography is subdued are used for grazing animals. 

In many of the locations, ground-water flow is complex and not 
16 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

90

Elk

Base from U.S. Geological Survey 

digital data, 1977, 1:100,000

Universal Transverse Mercator projection

Zone 13

0 0.5 1 MILE

EXPLANATION 0 0.5 1 KILOMETER

Stratigraphic units (modified from Strobel 

 and others, 1999)

Alluvium

Gravel deposits

Inyan Kara Group

Spearfish Formation

Minnekahta Limestone

Madison (Pahasapa) Limestone and 

 Englewood Formation 

Whitewood Formation and Winnepeg Formation

Opeche Shale

Minnelusa Formation 

Morrison Formation to Gypsum Spring 

 Formation, undifferentiated

Qa

Qg

Kik

Ju

Pmk

Po

MDme

Ou

Outline of estimated contributing area 

 to selected sites

T. 3 N.

R. 6 E.

9 8

11

23

17

14 16

10

22 21

15

20

5 4 3 2

27 26 29 28

7

19

18

30

12

6 1

13

24

25

MDme

Pmk

Qa

Qa

Po Kik

Kik

Ju

Qa

Qg

Kik

Creek

103°26’ 103°24’ 103°22’

44°14’

44°12’

Piedmont

10

Ground-water sampling site (number is 

 site number in table 5)

Approximate location of OWDS 

 (Sawyer, 2006)

8 9

11

12

13, 14, 15

16

17

Ou

Oa Po

Po

PPm

PPm

PPm

TrPs

TrPs

Figure 3. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study area 2 in the 

Spearfish and Minnekahta settings (see figure 1).

Figure 3. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study 

area 2 in the Spearfish and Minnekahta setting (see figure 1).
Methods of Study 17

Boxelder

90

44

16

5 4

3

6

8

1

8 9

9

2

7

7

1 2 3

5 6 4

12

11

11

14

27

28

23

20 22

26

17

29 28

15

19

30

33 31

31

10

32

29

30

23

24

36

13

10

18

35

25

21

12

34

16

34

19

27

20

21

32 33 35

26

36

24

22

25

15 13 16 17 14 18

14 13 18 17

16

15

3

2

11

34

27

22

2

14

15

10

34

27

23 22

26

14

35

11

15

26

35

PPm

PPm

TrPs

MDme

PPm

Ju

XWgw

Qa

Tg

Qa

Tw

Ju

Tg

TrPs

TrPs

Tg

Ju

Pmk

Qg

Qa

Qg

Kik

OCd

OCd

Tw

Po

Tw

Tg XWus

103°21’ 103°18’ 103°15’

44°05’

44°00’

Alluvium

Gravel deposits

Gravel deposits

White River Group

Inyan Kara Group

Morrison Formation to Gypsum Spring 

 Formation, undifferentiated

Spearfish Formation

Minnekahta Limestone

Opeche Shale

Minnelusa Formation

Madison (Pahasapa) Limestone and 

 Englewood Formation

Deadwood Formation

Metamorphosed graywacke

Undifferentiated metamorphosed 

 sedimentary deposits

Outline of estimated contributing area to 

 selected sites

Ground-water sampling site (number is site 

 number in table 5)

Approximate location of OWDS (Rapid City

 Onsite Inspection Program, written 

 commun., 2008)

R. 7 E.

Rapid City

Base from U.S. Geological Survey digital data,

1977, 1:100,000

Rapid City, Office of City Engineer map, 2005, 1:18,000

Universal Transverse Mercator projection

Zone 13

T. 2 N.

Rapid

T. 1 N.

R. 6 E.

T. 1 S.

Spring

EXPLANATION

Stratigraphic units (modified from Strobel and 

 others, 1999)

Qa

Qg

Tg

Tw

Kik

Ju

Pmk

Po

MDme

XWgw

XWus

0 10.5 2 MILES

0 10.5 2 KILOMETERS

18

19

20

21

22

23

25

24

Creek

Creek

Figure 4. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study area 3 in the 

Minnekahta and Precambrian settings (see figure 1).

Creek

Victoria Gulch

Figure 4. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study area 3 in the 

Minnekahta and Precambrian settings (see figure 1).
18 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

103°30’ 103°28’ 103°26’ 103°24’

44°04’

44°02’

Surface-water sampling site (number is site number in table 5)

Ground-water sampling site (number is site number in table 5)

Approximate location of OWDS (Sawyer, 2006)

T. 2 N.

R. 6 E.

T. 1 N.

R. 5 E.

44

Creek

Pactola

Reservoir

Prairie

385

OCd

PmP

Base from U.S. Geological Survey digital data,1977, 1:100,000

Universal Transverse Mercator projection

Zone 13

0 0.5 1 2 MILES

0 10.5 2 KILOMETERS

Rapid

Creek

39

26

28 27

29

30

31

32

33

34

35

36

40

41

38

37

Xush

XWui

MDme

XWgw

XWgw

Tg

Qc

XWus

XWgw

Xush

Colluvium

Gravel deposits

Gravel deposits

Undifferentiated metamorphosed phyllite and schist

Undifferentiated igneous rocks

Metamorphosed graywacke

Minnelusa Formation

Madison (Pahasapa) Limestone and Englewood Formation

Deadwood Formation

Undifferentiated metamorphosed sedimentary deposits

Outline of estimated contributing area to selected sites

EXPLANATION

Stratigraphic units (modified from Strobel and others, 1999)

Qc

Qg

Tg

Xwui

Xush

XWgw

MDme

XWus

Figure 5. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study area 4 in the 

Precambrian setting (see figure 1).

OCd

PmP

Figure 5. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study area 4 in 

Precambrian setting (see figure 1).
Methods of Study 19

well understood. Interaction of water in Precambrian rocks and 

gravel deposits complicates description of ground-water flow.

Three private wells in study area 4 adjacent to Prairie 

Creek (sites 39–41, fig. 5) are completed in Precambrian 

rocks and probably are less than 200 ft deep (table 5). Several 

OWDS are upgradient from the wells. Some of the housing 

units associated with the OWDS were used less during the 

winter season than during the rest of the year.

Thirteen private wells sampled in study area 5 (sites 

42–54, fig. 6) were completed in Precambrian rocks and most 

of these wells are less than 200 ft deep (table 5). Ground-water 

flow directions were assumed to follow the topography, which 

slopes towards Rapid Creek. OWDS are on metamorphosed 

phyllite and schist with thin soil cover. Sites 53 and 54 were 

considered background wells for the Precambrian setting 

because they are not downgradient from housing units.

Land use in study area 5 includes residential development 

of about 35 housing units in an area of approximately onethird mi2

. Some housing units were used year-round and others 

were used mostly during the summer. A few had holding tanks 

that were pumped rather than OWDS. The surrounding area is 

steep forest land with dense ponderosa pine.

31

6

36

32

1 5

42, 43

44

45

46

47 48 49 50 51

52 53 54

103°34’30” 103°34’ 103°33’30”

44°05’30”

44°05’

T. 2 N.

R. 4 E.

Base from U.S. Geological Survey digital data, 1977, 1:100,000 

Universal Transverse Mercator projection

Zone 13

T. 1 N.

R. 5 E.

Rapid

Pactola

Reservoir

Silver City

Ground-water sampling site (number is site number in table 5)

Approximate location of OWDS (Sawyer, 2006)

0 0.25 0.5 MILES

0 0.25 0.5 KILOMETERS

Undifferentiated metamorphosed phyllite and schist

Metamorphosed graywacke

EXPLANATION

Stratigraphic units (modified from Strobel and others, 1999)

Xush

XWgw

Figure 6. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study 

area 5 in the Precambrian setting (see figure 1).

Creek

Xush

XWgw

Figure 6. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for 

study area 5 in Precambrian setting (see figure 1).
20 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Eight private wells sampled in study area 6 (sites 55–62, 

fig. 7) were completed in Precambrian rocks, and the depth 

of the wells ranged from about 60 to several hundred feet 

(table 5). Ground-water flow directions were assumed to 

approximately follow the topography, which slopes towards 

Spring Creek. Site 55 is not located near any other development and was considered a background well for the Precambrian setting. 

Seven stream sites (sites 63–69, fig. 7) are located in 

study area 6. Sites 63 and 64 are on a small tributary on the 

south side of Sheridan Lake. Several OWDS are present 

between sites 63 and 64 on the metamorphic rocks adjacent 

to the stream. Because of generally dry conditions in the 

Spring Creek Basin, streamflow in the tributary was usually 

less than 1 cubic foot per second (ft3

/s). Sites 65 and 66 are on 

Reno Gulch, and areas on metamorphic rocks adjacent to the 

stream include OWDS. Sites 67–69 are on Spring Creek with 

site 67 upstream from most development and sites 68 and 69 

downstream from Hill City but upstream from Sheridan Lake. 

Numerous OWDS are along Spring Creek downstream from 

Hill City. 

Land use in study area 6 is a mix of residential development, small commercial establishments along major roads, 

grazing, and forest. Hill City has a central sewer system. 

Ground-water flow is complex, and interaction of water in Precambrian rocks with gravel deposits complicates description 

of flow directions.

Collection, Processing, and Analysis of Water 

Samples

Water samples were collected following established 

protocols for analysis of physical properties, major ions, nutrients, selected trace elements, and microbiological indicators 

described in the USGS National Field Manual (U.S. Geological Survey, 1997–2004). Special requirements for collection of 

OWCs were followed, including avoiding use of insect repellents, sunscreen, tobacco, caffeine, and pharmaceutical drugs 

by the sampling team (U.S. Geological Survey, 1997–2004). 

Samples for analysis of stable isotopes of nitrogen and oxygen 

were filtered and frozen prior to shipping according to laboratory instructions (U.S. Geological Survey, Reston Stable Isotope 

Laboratory, 2008). All containers and sampling equipment were 

constructed of plastic, Teflon, baked amber glass, or stainless 

steel and were rigorously cleaned according to standard USGS 

procedures. Ultra-clean two-person sampling procedures were 

used and included personnel wearing powderless nitrile gloves. 

Sites with open-hole monitoring wells were sampled by using 

pre-cleaned plastic bailers or stainless steel submersible pumps 

and Teflon tubing. OWC samples were collected with precleaned Teflon bailers when a submersible pump was not used. 

Sites with a private domestic or production well were sampled 

by using the installed pumping system, with the stainless-steel 

sampling port connected at the closest location to the well and 

prior to any filtration or treatment system. 

Samples were analyzed for major ions, nutrients, and 

trace elements at the USGS National Water Quality Laboratory (NWQL, in Lakewood, Colorado) using standard methods (Fishman, 1993; American Public Health Association, 

1998). OWC analyses also were conducted at the NWQL 

using methods described in Zaugg and others (2002). Isotopic 

composition of nitrate and oxygen were determined at the 

Reston Stable Isotope Laboratory (RSIL, in Reston, Virginia) 

by using mass spectrometry to analyze the conversion of 

nitrate to nitrous oxide (Révész and Casciotti, 2007). Samples 

were analyzed for the microbiological indicators E. coli, fecal 

coliforms, and enterococci at Energy Laboratories (Rapid 

City, South Dakota) using standard methods (American Public 

Health Association, 1998). Detailed analysis of microbiological indicators (coliphages and C. perfringens) was done at the 

Ohio Water Microbiology Laboratory (OWML, in Columbus, 

Ohio) according to approved methods (Bisson and Cabelli, 

1979; Armon and Payment, 1988; U.S. Environmental Protection Agency, 2001a and 2001b). 

Quality Assurance/Quality Control

A specific quality assurance/quality control (QA/QC) 

approach was developed to identify possible cases of random 

or systemic errors in the field sampling, shipping, and laboratory analyses. Field-equipment blank and sequential replicate 

samples were used to determine the potential for sample 

contamination. Field-equipment blank samples were collected 

at sites used for collection of environmental samples by passing analyte-free water through the collection and processing 

equipment used for the environmental samples and by using 

procedures identical to those used to collect and process the 

environmental samples. Constituent concentrations less than 

the minimum reporting level (MRL) in field-equipment blank 

samples indicate that the overall process of sample collection, 

processing, and laboratory analysis was free of significant 

contamination. The MRL is the lowest measured concentration 

of a constituent that may be reliably reported from the use of a 

given analytical method (Timme, 1995). Sporadic, infrequent 

detections at concentrations near the MRL probably represent random contamination or instrument calibration error 

that is not likely to cause bias in the study results. Consistent 

detections in the field-equipment blank samples at concentrations substantially less than concentrations in environmental 

samples commonly indicate routine contamination that did not 

substantially affect the evaluation of the environmental data. 

Field replicate samples were considered essentially identical in composition to the associated environmental sample. 

Precision of analytical results for field replicate samples may 

be affected by numerous sources of potential variability in 

field and laboratory processes, including sample collection, 

sample processing and handling, and laboratory preparation 

and analysis. Analyses of field replicate samples, therefore, 

can indicate the reproducibility of environmental data and 

provide information on the adequacy of procedures to pro-
Methods of Study 21

9

1 4 2 5 3 2

8

9

1

8 7

6

7

3

7

6

11 7

11 11

11

14

25

16

36

15 14 13 Xush

23

13

21

33

12

28

35

14

23

26 26

10

32

24

29

13

12

16

13 17

34

14

35

12

25

20

17

10

18

27

22 24

15

36

30

31

18

12

19

15

18

19

10

30

24

34

23

27

22

22

31

15

18

20 21

10

22 23 24 19 19

Spring

103°35’ 103°30’

43°57’30”

43°55’

43°52’30”

Ground-water sampling site (number is site number in table 5)

Surface-water sampling site (number is site number in table 5)

Approximate location of OWDS (Sawyer, 2006)

T. 1 S.

R. 4 E.

Base from U.S. Geological Survey digital data, 1977, 1:100,000

Universal Transverse Mercator projection

Zone 13

T. 2 S.

R. 5 E. R. 6 E.

Creek

Creek

Hill City

Sheridan 

Lake

Xh

XWgw

Xush

Qa

XWgw

Xush

XWus

XWgw

Xush

Xush

Xush

XWus

XWus

XWui

Qa

Xush

XWus

XWgw

XWgw

Xush

Qc

Xush

XWgw Xush

XWgw

55

56 57 58

59 60

61

62

64

69

65

67

63

68

66

Mitchell 

Lake

Xush

Alluvium

Colluvium

Gravel deposits

Metamorphosed graywacke

Undifferentiated metamorphosed sedimentary deposits

Harney Peak Granite

Undifferentiated metamorphosed phyllite and schist

Undifferentiated igneous rocks

EXPLANATION

Stratigraphic units (modified from Strobel and others, 1999)

Qa

Qc

Qg

XWgw

XWus

Xh

Xwui

0 10.5 2 MILES

0 10.5 2 KILOMETERS

Figure 7. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for study 

area 6 in the Precambrian setting (see figure 1).

Reno Gulch

Battle

Qa

Qg

Figure 7. Locations of sampling sites, onsite wastewater disposal systems (OWDS), and stratigraphic units for 

study area 6 in the Precambrian setting (see figure 1).
22 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

duce consistent results. Precision of analytical results for field 

replicate samples was determined by calculating the relative 

percent difference (RPD) for each environmental/replicate 

sample pair as indicated in the following equation (Sando and 

others, 2006):

RPD = (d/x)*100, (2)

where

d = difference in concentration between the 

primary environmental sample and the 

field replicate sample for a given primary/

replicate sample pair, and 

x = mean concentration of the primary 

environmental sample and the field 

replicate sample for a given primary/

replicate sample pair.

RPD values were calculated only for selected physical properties, major ions, nutrients, and selected trace elements. OWC 

detections in environmental/replicate sample pairs were rare, 

and concentrations did not exceed the MRLs; thus, RPD values were not calculated for these data.

Generally, an RPD of 20 percent or less represents an 

acceptable level of precision, although for very low concentrations near the limit of analytical detectability, the percent 

differences can be substantially larger and still be considered 

reasonable owing to the limits of resolution (Taylor, 1987). 

Physical Properties, Major Ions, Nutrients, and 

Selected Trace Elements 

Field-equipment blank results for selected physical properties, major ions, nutrients, and selected trace elements are 

shown in table 20 in the “Supplemental Information” section 

of this report. Nine field blanks were analyzed for screening 

wastewater indicators, and four blank samples were analyzed 

for other constituents. All concentrations in blank samples 

were equal to or less than MRLs except for the concentration 

of chloride in one sample, which was 0.24 mg/L compared to 

the MRL of 0.12 mg/L.

RPD values for environmental and replicate sample pairs 

are presented in table 21 in the “Supplemental Information” 

section. Eleven replicates were analyzed for screening wastewater indicators, and six replicates were analyzed for other 

constituents. RPD values for 90 percent of the 11 replicate 

samples for screening indicators were less than 5 percent. 

Only one RPD value of the screening indicators was higher 

than 20 percent. It was for an ammonia analysis in which 

the environmental sample concentration was 0.069 and the 

replicate sample concentration was 0.199 mg/L. RPD values 

for 88 percent of the 6 replicate samples for other constituents were less than 5 percent. One sample analyzed for acid 

neutralizing capacity had an RPD value of 24.2 percent. Two 

phosphorous replicate samples had RPD values of 22.2 and 

28.6 percent; however, concentrations for these samples were 

near the MRL for phosphorus (<0.006 mg/L).

Nitrogen and Oxygen Isotope Ratios in Nitrate

RPD values for δ15N and δ18O in nitrate for five samples 

are shown in table 22 in the “Supplemental Information” 

section. RPD values for all replicate samples were less than 

20 percent except for a δ18O sample at site 9. The δ18O value 

was -1.24 ‰ in the environmental sample and -2.10 ‰ in the 

replicate sample. RPD values for all δ15N analyses were less 

than 5 percent.

Microbiological Indicators

Blank samples collected with 4 of the 108 ground-water 

environmental samples were analyzed for fecal coliforms and 

E. coli, and blank samples collected with 1 of the 51 groundwater environmental samples were analyzed for enterococci. 

Blank samples collected with 2 of the 22 surface-water 

environmental samples were analyzed for fecal coliforms and 

E. coli, and blank samples collected with 1 of the 10 surfacewater environmental samples were analyzed for enterococci. 

For ground-water and surface-water samples, none of the 

blank samples had detections of fecal coliforms, E. coli, or 

enterococci.

Replicate samples collected with five of the groundwater environmental samples were analyzed for fecal coliforms and E. coli, and replicate samples collected with two 

of the ground-water environmental samples were analyzed 

for enterococci. Replicate samples collected with four of 

the surface-water environmental samples were analyzed for 

fecal coliforms and E. coli, and replicate samples with one of 

the surface-water environmental samples were analyzed for 

enterococci. 

Of the 12 ground-water environmental/replicate sample 

pairs (table 23 in “Supplemental Information” section), 

2 microbiological indicators (E. coli and enterococci) were 

detected in the environmental sample at site 22 on September 

19, 2007, and the companion replicate sample confirmed the 

presence of both indicators. No other indicators were detected 

in the other ground-water environmental samples with replicate pairs. No replicate samples had detections when the 

companion environmental sample did not have a detection.

Of the nine surface-water environmental/replicate pairs 

(table 23 in “Supplemental Information” section), microbiological indicators were detected in eight of the environmental 

samples. Microbiological indicators were detected in seven of 

the corresponding replicate samples. The microbiological indicator fecal coliform was detected in one environmental sample 

when the indicator was not detected in the companion replicate sample. Although microbiological indicator replicates 

were not used quantitatively, they do provide a qualitative 

indication of reproducibility. No blank or replicate samples 
Methods of Study 23

were collected with environmental samples for C. perfringens

or coliphages.

Organic Wastewater Compounds

Analysis of OWCs presented in this report requires a 

greater interpretive effort not usually needed for other waterquality constituents that have higher concentrations. The 

capability for quantification of low-level (part-per-billion and 

lower) concentrations varied, as demonstrated by the varied 

MRLs for some compounds during the course of the study 

(table 33 in “Supplemental Information Section”). Correct 

interpretation of these reporting levels is important because 

the vast majority of compounds (greater than 99 percent) were 

detected at concentrations equal to or less than the MRL. 

Laboratory results were classified into four categories: 

(1) numerical quantification of the concentration, (2) estimated 

quantification of the concentration, (3) confirmed presence 

of compound but no quantification of concentration, 

and (4) compound not detected in sample. Only compounds 

with laboratory analytical result concentrations higher than 

the MRL could be classified into category 1. Compounds with 

concentrations higher than the method detection limit (MDL) 

but less than the MRL were classified into category 2. The 

MDL is the minimum concentration of a substance that can 

be measured and reported with 99 percent confidence that the 

analyte concentration is greater than zero (U.S. Environmental 

Protection Agency, 2002b). Concentrations equal to or less 

than the MDL were classified into category 3. 

The reporting of analytical results in a manner that 

lessens the effect of precision/accuracy variability by focusing 

on the presence/absence instead of quantification was selected 

for OWC data analysis because of the lack of quantifiable 

OWC data. This approach, which truncates the data set, probably represents a more conservative presentation of the OWC 

analytical results than an approach that uses semi-quantitative 

methods (Sando and others, 2006). The data set was truncated 

such that all OWC results that were classified in categories 

1, 2, and 3 were considered “detections.” No greater weight 

was placed on any of these first three categories. In addition to using a presence/absence approach to the OWC data, 

companion field blank data were used to adjust the detection 

frequencies when a compound was detected in both the blank 

and environmental samples (Grady, 2003). This adjustment 

methodology subtracts any environmental detection from 

the total number of detections when the concentration in the 

environmental sample is less than five times the corresponding 

concentration in the blank sample. In this study, this method 

was applied by censoring any environmental sample result that 

had detection in the corresponding blank sample. 

Field equipment blank samples for OWC analysis were 

collected with 22 of the 25 environmental ground-water 

samples (88 percent) and with all 10 of the environmental 

surface-water samples. For ground-water samples, seven different compounds were detected in blank samples, and detection frequencies ranged from 4.5 to 59 percent of samples. 

Six corresponding environmental samples contained the same 

compound (DEET) detected in the blanks, and DEET concentrations in these environmental samples were censored (sites 

11, 17, 21, and 22). Although a certain compound detected in 

an environmental sample may have no detection in the corresponding blank sample, the data must be used cautiously if 

the compound was detected in a large percentage of the other 

blank samples. For example, with the exclusion of 6 censored 

sample pairs, DEET was detected in 32 percent of the 

19 remaining environmental ground-water samples and in 

44 percent of the 16 remaining blank samples (including blank 

samples used for censoring, DEET was detected in 59 percent 

of 22 ground-water blank samples). For surface-water blank 

samples, 7 compounds were detected, each found in no more 

than 2 of the 10 samples. Four surface-water environmental 

sample detections were omitted from the data set owing to 

detections of camphor and DEET in the companion blank 

samples at sites 67, 68, and 69 (table 33). 

Sequential replicate samples were collected with 4 of the 

25 environmental ground-water samples (16 percent) and with 

1 of the 10 environmental surface-water samples (10 percent). Environmental samples with replicate pairs had a total of four OWC 

detections in ground- and surface-water samples. The detections were confirmed by the presence of the same compound 

in the replicate sample for all four occurrences. One replicate 

ground-water sample had a detection of tris-(dichloroisopropyl) 

phosphate that was not matched by a detection in the corresponding environmental sample. No other OWCs were detected 

in the other environmental/replicate pairs. 

In addition to the field QA/QC method described previously, laboratory QA/QC procedures included processing and 

analyzing method-blank and reagent-spike samples, and adding surrogate compounds to all laboratory QA/QC samples, 

field QA/QC samples, and environmental samples. Surrogate 

compounds are similar in physical and chemical properties to 

one or more of the method analytes, and are added in known 

quantities to all QA/QC and environmental water samples 

prior to analysis. Surrogate compounds are used to assess the 

effects of specific environmental matrixes on the performance 

of a given analytical method and in some cases to assess the 

potential for errors during the processing of a specific environmental sample. Analytical method performance was considered to be satisfactory when the median percent recoveries 

for laboratory surrogates were between 50 and 120 percent, 

and when the relative standard deviations (RSDs) of percent 

recovery were less than 40 percent (Sando and others, 2006). 

The RSD, in percent, was calculated by using the following 

equation:

RSD = (S / X ) * 100, (3)

where

S = standard deviation of percent recoveries of 

surrogate samples, and

X = mean of percent recoveries of surrogate 

samples.
24 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Mean surrogate recoveries ranged from 58 to 89 percent 

in ground-water samples and from 56 to 85 percent in surfacewater samples. RSDs of percent recovery ranged from 11 to 

16 percent in ground-water samples and from 4.3 to 5.0 percent in surface-water samples. All surrogate QA/QC values 

were within the acceptable ranges. 

Water-Quality Effects, Indicators, and 

Isotopes of Nitrate

Results for water-quality effects, indicators, and isotopes 

of nitrate are presented in four groups: (1) physical properties, 

major ions, nutrients, and selected trace elements; (2) nitrogen 

and oxygen isotope ratios of nitrate; (3) microbiological indicators; and (4) OWCs. Each group is subdivided by the alluvial, Spearfish, Minnekahta, and Precambrian hydrogeologic 

settings. The Precambrian hydrogeologic setting is further 

divided by ground- and surface-water sample results. 

Physical Properties, Major Ions, Nutrients, and 

Selected Trace Elements

Measurements of physical properties in ground water 

listed by sample are presented in table 24 (“Supplemental 

Information” section). Measurements of physical properties in 

surface water listed by sample are presented in table 25 (“Supplemental Information” section). Concentrations of major ions, 

nutrients, and selected trace elements in ground water listed by 

sample are presented in table 26 (“Supplemental Information” 

section). Concentrations of major ions, nutrients, and selected 

trace elements in surface water listed by sample are presented 

in table 27 (“Supplemental Information” section). 

In this report, concentration units of NO2

+NO3 are milligrams per liter as N, but are labeled simply as “mg/L.” For 

constituent values for censored data (data that were expressed 

as a value preceded by a less-than symbol), a number equal 

to one-half of the “value” was substituted for calculation of 

summary statistics. If only a single sample was available, the 

censored value was listed as the mean in the table.

Alluvial Setting

Ground-water sites included in the alluvial setting 

are sites 3–7 for downgradient wells and sites 1 and 2 for 

background wells. A statistical summary of physical properties and concentrations of major ions, nutrients, and selected 

trace elements for ground-water samples from the alluvial 

setting (table 6) shows that mean specific conductance was 

3,680 microsiemens per centimeter at 25°C (μS/cm) for 

downgradient samples and 1,220 μS/cm for background 

samples. The mean dissolved chloride concentration was 

324 mg/L for downgradient samples and 31.6 mg/L for background samples. Dissolved chloride concentrations in 6 of 

11 downgradient samples exceeded the Secondary Maximum 

Contaminant Level (SMCL) of 250 mg/L (table 26, sites 5 

and 6). The mean dissolved concentration of NO2

+NO3 was 

0.734 mg/L for downgradient samples and 0.168 mg/L for 

background samples. Dissolved concentrations of ammonia 

nitrogen had a mean of 0.142 mg/L for downgradient samples 

and 0.014 mg/L for background samples. Mean dissolved 

boron concentrations were 736 μg/L for downgradient samples 

and 335 μg/L for background samples.

The mean dissolved sodium concentration for downgradient samples was 428 mg/L, whereas the concentration 

in a single background sample was 34.6 mg/L. The mean 

dissolved sulfate concentration was 1,730 mg/L for downgradient samples and 280 mg/L in a single background sample. 

Dissolved sulfate concentrations in alluvial downgradient 

and background samples exceeded the SMCL of 250 mg/L 

(table 26, sites 2, 4–6). The mean dissolved orthophosphate 

concentration was 0.017 mg/L for downgradient samples 

and 0.008 mg/L in a single background sample. The mean 

dissolved iron concentration was 3,740 μg/L for downgradient 

samples and <6 μg/L in a single background sample. Dissolved iron concentrations for 2 of the 5 downgradient samples 

exceeded the SMCL of 300 μg/L (table 26, site 6). The mean 

dissolved manganese concentration was 912 μg/L for downgradient samples and 31 μg/L in a single background sample. 

Dissolved manganese concentrations in all five downgradient 

samples exceeded the SMCL of 50 μg/L (table 26, sites 4–6).

Spearfish Setting 

Ground-water sites included in the Spearfish setting 

are sites 10–14 for downgradient wells and site 16 for a 

background well. A statistical summary of physical properties and concentrations of major ions, nutrients, and selected 

trace elements for ground-water samples from the Spearfish 

setting (table 7) shows that the mean specific conductance 

of 1,130 μS/cm for downgradient samples was higher than 

the mean of 520 μS/cm for background samples. The mean 

dissolved chloride concentration was 89.6 mg/L for downgradient samples and 2.18 mg/L for background samples. The 

mean dissolved NO2

+NO3 concentration of 7.90 mg/L for 

downgradient samples was higher than the mean concentration 

of 0.250 mg/L for background samples. Dissolved NO2

+NO3 

concentrations in 7 of 17 downgradient samples exceeded the 

Maximum Contaminant Level (MCL) of 10 mg/L (table 26, 

sites 11, 13, and 14). The mean dissolved ammonia nitrogen 

concentration was 0.021 mg/L for downgradient samples and 

0.027 mg/L for background samples. Downgradient samples 

had a higher mean dissolved boron concentration (53 μg/L) 

than background samples (14 μg/L).

The mean dissolved sodium concentration was 16.1 mg/L 

in downgradient samples and 1.70 mg/L in a single background sample. The mean dissolved sulfate concentration 

was 80.6 mg/L for downgradient samples and 3.90 mg/L in 

a single background sample. The mean dissolved orthophosphate concentration was 0.020 mg/L for downgradient samples 
Table 6. Summary of physical properties and concentrations of major ions, nutrients, and selected trace elements for ground water in the alluvial se[USGS, U.S. Geological Survey; μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, no data or not applicable; mg/L, milligrams per liter; <, less tmicrograms per liter]

Constituent (USGS parameter code) Unit of measurement

Downgradient wells1 Backgrou

Number

of 

samples

Number

of 

censored 

samples

Mean Median Minimum Maximum

Number 

of 

samples

Number 

of 

censored 

samples

Mean 

Specific conductance, water whole, field (00095)Specific conductance, water whole, laboratory 

(90095)

pH, water whole, field (00400)pH, water whole, laboratory (00403)Dissolved oxygen (00300)Acid neutralizing capacity, laboratory (90410)Calcium, dissolved (00915)Magnesium, dissolved (00925)Sodium, dissolved (00930)Potassium, dissolved (00935)Sulfate, dissolved (00945)Chloride, dissolved (00940)Fluoride, dissolved (00950)Bromide, dissolved (71870)Chloride/bromide ratioSilica, dissolved (00955)Nitrogen, nitrite, dissolved (00613)Nitrogen, NO +NO , dissolved (00631) 2 3Nitrogen, ammonia, dissolved (00608)Phosphorous, dissolved (00666)Orthophosphate, dissolved (00671)Boron, dissolved (01020)Iron, dissolved (01046)Manganese, dissolved (01056)

μS/cmμS/cmstandard unitsstandard unitsmg/Lmg/L as 

CaCO3

mg/L as Camg/L as Mgmg/L as Namg/L as Kmg/L as SO4mg/L as Clmg/L as Fmg/L as Br

--

mg/L as Simg/L as Nmg/L as Nmg/L as Nmg/L as Pmg/L as Pμg/L as Bμg/L as Feμg/L as Mn

11

5

11

5

11

555555

11

5

1111

55

1111

55

11

55

000000000000000004400030

3,6804,650

6.87.06.4

619388239428

9.07

1,730

324

.60.18

3,880

13.4

.010.734.142.014.017

736

3,740

912

4,0704,420

6.77.05.5

513348254349

8.94

1,730

324

.62.17

1,050

13.4

.010.047.030.008.010

819

15

1,330

1,3002,940

6.66.93.3

421273154202

7.76

1,010

54.1

.50.03

492

10.7

.002

E.015

<.020

E.005

.009

121

<18

90.9

6,0606,110

7.07.0

15.6

1,130

500274629

10.6

2,120

824

.73.34

27,500

15.6

.020

2.61

.525.042.043

1,060

12,400

1,590

313131111113133113311311

000000000000000010100010

1,2201,140

7.07.35.4

705111

65.834.6

3.85

280

31.6

.57.07

451

12.3

<.00

.16.01

E.00

.00

335

<6

31

1Summary includes sites 3–7.2Summary includes sites 1 and 2.
Table 7. Summary of physical properties and concentrations of major ions, nutrients, and selected trace elements for ground water in the Spearfish [USGS, U.S. Geological Survey; μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, no data or not applicable; mg/L, milligrams per liter; E, estimmicrograms per liter] Constituent (USGS parameter code) Unit of measurement Downgradient wells1 Back

Number of samples Number of censored samples Mean Median Minimum Maximum Number of samples Number of 

censored samples 

Specific conductance, water whole, field (00095) Specific conductance, water whole, laboratory (90095) pH, water whole, field (00400) pH, water whole, laboratory (00403) Dissolved oxygen (00300) Acid neutralizing capacity, laboratory (90410) Calcium, dissolved (00915) Magnesium, dissolved (00925) Sodium, dissolved (00930) Potassium, dissolved (00935) Sulfate, dissolved (00945) Chloride, dissolved (00940) Fluoride, dissolved (00950) Bromide, dissolved (71870) Chloride/bromide ratio Silica, dissolved (00955) Nitrogen, nitrite, dissolved (00613) Nitrogen, NO +NO , dissolved (00631) 2 3 Nitrogen, ammonia, dissolved (00608) Phosphorous, dissolved (00666) Orthophosphate, dissolved (00671) Boron, dissolved (01020) Iron, dissolved (01046) Manganese, dissolved (01056) μS/cm μS/cm standard units standard units mg/L mg/L as CaCO3 mg/L as Ca mg/L as Mg mg/L as Na mg/L as K mg/L as SO4 mg/L as Cl mg/L as F mg/L as Br -- mg/L as Si mg/L as N mg/L as N mg/L as N mg/L as P mg/L as P μg/L as B μg/L as Fe μg/L as Mn 17111711168111111111117111717111117171111171111 0000000000000000901300050 1,130 1,1306.8 7.2 9.6 406 14551.2 16.1 2.31 80.6 89.6.22 .37 43612.2.001 7.90 .021 .024 .020 5353.3 1,140 1,1706.8 7.3 10.6 343 15349.0 15.6 2.31 57.2 35.0.21 .07 46312.1.001 6.77 .010 .009 .013 554.7 717 7456.4 7.0 1.6 316 10232.2 5.38 1.69 44.7 14.3.17 .03 18910.5 <.002 .100 E.012 E.004 .008 18E4E.2 1,760 1,7107.2 7.4 16.7 631 20378.2 33.1 3.79 142 304.30 1.5 1,24013.8 E.002 14.9.156 .077 .058 1321328.2 212120111112122112211211 000000000000020010100010 

1Summary includes sites 10–14. 2Summary includes site 16.
Water-Quality Effects, Indicators, and Isotopes of Nitrate 27

and 0.007 μg/L in a single background sample. The mean 

dissolved iron concentration was 5 μg/L for downgradient 

samples and <8 μg/L in a single background sample. The 

mean dissolved manganese concentration was 3.3 μg/L for 

downgradient samples and 4.9 μg/L in a single background 

sample. 

Minnekahta Setting

Ground-water sites included in the Minnekahta setting 

are sites 8, 9, and 17–23 for downgradient wells and sites 15 

and 24 for background wells. A statistical summary of physical properties and concentrations of major ions, nutrients, 

and selected trace elements for ground-water samples from 

the Minnekahta setting (table 8) shows that the mean specific 

conductance for downgradient samples of 1,980 μS/cm was 

higher than the mean of 776 μS/cm for background samples. 

The mean dissolved chloride concentration was 498 mg/L for 

downgradient samples and 18.2 mg/L for background samples. 

Dissolved chloride concentrations for 15 of 33 downgradient 

samples exceeded the SMCL of 250 mg/L (table 26, sites 8 

and 19–23). The mean dissolved NO2

+NO3 concentration of 

8.62 mg/L for downgradient samples was higher than the mean 

for background samples of 1.37 mg/L. Dissolved NO2

+NO3 

concentrations for 8 of 33 downgradient samples exceeded the 

MCL of 10 mg/L (table 26, sites 19, 20, and 22). The mean 

dissolved ammonia nitrogen was 0.014 mg/L for downgradient samples and 0.013 mg/L for the three background samples. 

The mean dissolved boron concentrations was 64 μg/L for 

downgradient samples and 23 μg/L for background samples.

The mean dissolved sodium concentration was 150 mg/L 

for downgradient samples and 7.3 mg/L in a single background sample. The mean dissolved sulfate concentration was 

187 mg/L for downgradient samples and 175 mg/L in a single 

background sample. Dissolved sulfate concentrations for 8 of 

23 downgradient samples exceeded the SMCL of 250 mg/L 

(table 26, sites 17, 21, and 22). The mean dissolved orthophosphate concentration was 0.041 mg/L for downgradient samples 

and 0.008 μg/L in a single background sample. The mean 

dissolved iron concentration was 10 μg/L for downgradient 

samples and <8 μg/L in a single background sample. The 

mean dissolved manganese concentration was 2.5 μg/L for 

downgradient samples and <0.4 μg/L in a single background 

sample.

Precambrian Setting

The analytical results of OWDS indicator samples in the 

Precambrian setting are grouped by ground- and surface-water 

results. Including both downgradient and background groundwater sites, there are 14 sites in study area 4, 13 sites in study 

area 5, and 8 sites in study area 6. Including both upstream 

and downstream sites, 2 surface-water sites are in study area 4 

and 7 surface-water sites are in study area 6.

Ground Water

Ground-water sites included in the Precambrian setting 

are sites 25–36, 39–52, and 56–62 for downgradient wells and 

sites 53–55 for background wells. A statistical summary of 

physical properties and concentrations of major ions, nutrients, 

and selected trace elements for ground-water samples from 

the Precambrian setting (table 9) shows that the mean specific 

conductance for downgradient samples of 632 μS/cm was 

higher than the mean for background samples of 417 μS/cm. 

The mean dissolved chloride concentration was 33.2 mg/L for 

downgradient samples and 2.14 mg/L for background samples. 

The mean dissolved NO2

+NO3 concentration was 2.25 mg/L 

for downgradient samples and 0.087 mg/L for background 

samples. The mean dissolved ammonia nitrogen concentration 

was 0.017 mg/L for downgradient samples and 0.048 mg/L for 

background samples. The mean dissolved boron concentration 

of 43 μg/L for downgradient samples was lower than the mean 

of 61 μg/L for background samples.

Dissolved sodium concentrations for downgradient 

samples had a mean of 17.6 mg/L. Dissolved sulfate concentrations for downgradient samples had a mean of 60.7 mg/L. 

Dissolved orthophosphate concentrations for downgradient 

samples had a mean of 0.014 mg/L. Dissolved iron concentrations for downgradient samples had a mean of 101 μg/L. Dissolved iron concentrations for 1 of 10 downgradient samples 

exceeded the SMCL of 300 μg/L (table 26, site 41). Dissolved 

manganese concentrations for downgradient samples had a 

mean of 281 μg/L. Dissolved manganese concentrations for 6 

of the 10 downgradient samples exceeded the SMCL of 

50 μg/L (table 26, sites 39, 41, 44, 45, and 48).

Surface Water

Surface-water sites in study areas 4 and 6 were grouped 

into sites upstream and downstream from areas of high OWDS 

density. Upstream sites (background) are 37, 63, 65, and 67, 

and downstream sites are 38, 64, 66, 68, and 69. Each waterquality sample collected from downstream sites also had a 

corresponding sample from the upstream site on the same date, 

allowing for direct comparison of upstream and downstream 

water quality.

A statistical summary of physical properties and concentrations of major ions, nutrients, and selected trace elements 

for surface-water samples from the Precambrian setting (table 

10) shows that the mean specific conductance was 501 μS/cm for 

downstream samples and 403 μS/cm in background samples. 

The mean dissolved chloride concentration was 32.1 mg/L for 

downstream samples and 13.6 mg/L for background samples. 

The mean dissolved NO2

+NO3 concentration was 0.222 mg/L 

for downstream samples and 0.192 mg/L for background 

samples. The mean dissolved ammonia nitrogen concentration 

was 0.014 mg/L for downstream samples and 0.008 mg/L for 

background samples. The mean dissolved boron concentration 

was 28 μg/L for downstream samples and 16 μg/L for background samples.
Table 8. Summary of physical properties and concentrations of major ions, nutrients, and selected trace elements for ground water in the Minnekah[USGS, U.S. Geological Survey; μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, no data or not applicable; mg/L, milligrams per liter; E, estimmicrograms per liter] Constituent (USGS parameter code) Unit of measurement Downgradient wells1 Back

Number of samples Number of censored samples Mean Median Minimum Maximum Number of samples Number of 

censored samples 

Specific conductance, water whole, field (00095) Specific conductance, water whole, laboratory (90095) pH, water whole, field (00400) pH, water whole, laboratory (00403) Dissolved oxygen (00300) Acid neutralizing capacity, laboratory (90410) Calcium, dissolved (00915) Magnesium, dissolved (00925) Sodium, dissolved (00930) Potassium, dissolved (00935) Sulfate, dissolved (00945) Chloride, dissolved (00940) Fluoride, dissolved (00950) Bromide, dissolved (71870) Chloride/bromide ratio Silica, dissolved (00955) Nitrogen, nitrite, dissolved (00613) Nitrogen, NO +NO , dissolved (00631) 2 3 Nitrogen, ammonia, dissolved (00608) Phosphorous, dissolved (00666) Orthophosphate, dissolved (00671) Boron, dissolved (01020) Iron, dissolved (01046) Manganese, dissolved (01056) μS/cm μS/cm standard units standard units mg/L mg/L as CaCO3 mg/L as Ca mg/L as Mg mg/L as Na mg/L as K mg/L as SO4 mg/L as Cl mg/L as F mg/L as Br -- mg/L as Si mg/L as N mg/L as N mg/L as N mg/L as P mg/L as P μg/L as B μg/L as Fe μg/L as Mn 342334233322232323232333233333232333332323332323 00000000000000001002700090 1,980 2,2206.7 7.1 9.9 340 23248.3 1505.98 187 498.40 .44 3,65010.7.002 8.62 .014 .063 .041 64102.5 1,540 1,6006.7 7.1 9.6 334 22645.3 46.4 3.40 181 175.41 .06 3,00010.3.001 7.42 .010 .031 .015 4292.2 513 7575.6 6.8 5.4 195 11620.2 4.32 1.73 25.8 8.16 .14 E.01 699.20 E.001 1.95 <.010 .007 .004 16E4E.2 9,050 9,2107.2 7.5 17.5 761 527 103 1,16019.4 402 3,080.68 3.72 30,20015.1.006 24.3.062 .260 .284 221265.6 313131111113133113311311 000000000000003010300011 7

842115

<

1Summary includes sites 8, 9, 17–23. 2Summary includes sites 15 and 24.
Table 9. Summary of physical properties and concentrations of major ions, nutrients, and selected trace elements for ground water in the Precambr[USGS, U.S. Geological Survey; μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, no data or not applicable; mg/L, milligrams per liter; E, estimmicrograms per liter]

Constituent (USGS parameter code) Unit of measurement

Downgradient wells1 Backgrou

Number

of 

samples

Number

of 

censored 

samples

Mean Median Minimum Maximum Number of samples

Number 

of M

censored 

samples

Specific conductance, water whole, field (00095)Specific conductance, water whole, laboratory (90095)

pH, water whole, field (00400)pH, water whole, laboratory (00403)Dissolved oxygen (00300)Acid neutralizing capacity, laboratory (90410)Calcium, dissolved (00915)Magnesium, dissolved (00925)Sodium, dissolved (00930)Potassium, dissolved (00935)Sulfate, dissolved (00945)Chloride, dissolved (00940)Fluoride, dissolved (00950)Bromide, dissolved (71870)Chloride/Bromide ratioSilica, dissolved (00955)Nitrogen, nitrite, dissolved (00613)Nitrogen, NO +NO , dissolved (00631) 2 3Nitrogen, ammonia, dissolved (00608)Phosphorous, dissolved (00666)Orthophosphate, dissolved (00671)Boron, dissolved (01020)Iron, dissolved (01046)Manganese, dissolved (01056)

μS/cmμS/cmstandard unitsstandard unitsmg/Lmg/L as CaCO3mg/L as Camg/L as Mgmg/L as Namg/L as Kmg/L as SO4mg/L as Clmg/L as Fmg/L as Br

--

mg/L as Simg/L as Nmg/L as Nmg/L as Nmg/L as Pmg/L as Pμg/L as Bμg/L as Feμg/L as Mn

391038103710101010101039103939101039391010391010

000000000000000069

30

31031

632738

6.57.17.5

247

79.534.317.6

2.78

60.733.2

.42.057

582

17.3

.006

2.25

.017.007.014

43

101281

626763

6.67.27.8

233

73.827.818.6

2.22

58.326.8

.37.050

545

16.2

.001

1.13

.010.006.012

31

6

217

231460

5.26.63.6

155

54.921.5

4.761.88

28.3

1.37

.27.020

4611.6

E.001E.009E.010E.004

<.006

13

E5

<.2

1,0401,060

7.27.5

13.7

400118

53.135.7

5.28

88.287.2

.97.160

1,260

24.5

.029

8.53

.157.017.038

217898

1,120

303030000003033003300300

0

--

0

--

0

------------

0

--

00

----

21

----

0

----

417

662

76

1Summary includes sites 25–36, 39–52, and 56–62.2Summary includes sites 53–55.
Table 10. Summary of physical properties and concentrations of major ions, nutrients, and selected trace elements for surface water in the Precam[USGS, U.S. Geological Survey; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; E, estimated; <, less than; μg/L, micr

Constituent (USGS parameter code) Unit of measurement Downstream sites1 Upstream (bac

Number of samples Number of censored samples Mean Median Minimum Maximum Number of samples Number of Mean 

censored samples 

Specific conductance, water whole, field (00095) Specific conductance, water whole, laboratory (90095) pH, water whole, field (00400) pH, water whole, laboratory (00403) Dissolved oxygen (00300) Acid neutralizing capacity, laboratory (90410) Calcium, dissolved (00915) Magnesium, dissolved (00925) Sodium, dissolved (00930) Potassium, dissolved (00935) Sulfate, dissolved (00945) Chloride, dissolved (00940) Fluoride, dissolved (00950) Bromide, dissolved (71870) Silica, dissolved (00955) Nitrogen, nitrite, dissolved (00613) Nitrogen, NO +NO , dissolved (00631) 2 3 Nitrogen, ammonia, dissolved (00608) Phosphorous, dissolved (00666) Orthophosphate, dissolved (00671) Boron, dissolved (01020) Iron, dissolved (01046) Manganese, dissolved (01056) μS/cm μS/cm standard units standard units mg/L mg/L as CaCO3 mg/L as Ca mg/L as Mg mg/L as Na mg/L as K mg/L as SO4 mg/L as Cl mg/L as F mg/L as Br mg/L as Si mg/L as N mg/L as N mg/L as N mg/L as P mg/L as P μg/L as B μg/L as Fe μg/L as Mn 127106966666612612671212771266 00000000000000014612000 501 4997.6 8.4 9.6 16447.1 19.6 17.6 5.94 31.9 32.1.32 .08 10.2.020 .222 .014 .009 .011 28 10142.8 498 4777.9 8.4 10.2 16346.6 20.0 19.7 6.83 23.9 33.2.30 .06 9.6.001 .032 .010 .011 .012 249030.0 414 4096.0 8.1 5.0 14040.6 15.2 3.23 2.53 21.9 2.83 .22 E.02 8.46 E.001 <.016 E.005 E.003 E.003 10E46.2 621 6258.5 8.5 13.3 19557.5 23.6 36.0 9.32 49.9 73.4.53 .23 12.6.075 1.60 .046 .018 .022 70 226 133 1048484444441049451010551044 00000000000000032700000 403 4167.4 8.2 9.8 17345.1 22.1 4.50 4.16 40.2 13.6.25 .04 10.8.001 .192 .008 .007 .007 166223.7 

1Summary includes sites 38, 64, 66, 68, and 69. 2Summary includes sites 37, 63, 65, and 67.
Water-Quality Effects, Indicators, and Isotopes of Nitrate 31

The mean dissolved sulfate concentration was 31.9 mg/L 

for downstream samples and 40.2 mg/L for background 

samples. The mean dissolved orthophosphate concentration 

was 0.011 mg/L for downstream samples and 0.007 mg/L for 

background samples. The mean dissolved iron concentration 

was 101 μg/L for downstream samples and 62 μg/L for background samples. The mean dissolved manganese concentration was 42.8 μg/L for downstream samples and 23.7 μg/L for 

background samples.

Nitrogen and Oxygen Isotope Ratios in Nitrate

Values of δ15N and δ18O in ground water are listed by 

sample in table 28 in the “Supplemental Information” section. 

Values of δ15N and δ18O in surface water are listed by sample 

in table 29 in the “Supplemental Information” section.

A plot of δ15N and δ18O values for nitrate in 48 groundwater samples collected (fig. 8 and table 28) in the study 

area in relation to the isotopic composition of various nitrate 

sources modified from Clark and Fritz (1997) assumes an 

average value of -13 ‰ for δ18O for local ground water. The 

mean δ15N and δ18O values for nitrate in water samples were 

10.4 and -2.0 ‰, respectively, indicating a relatively small 

contribution from synthetic fertilizer and probably a substantial contribution of nitrate from OWDS. Three samples 

from the sites in the alluvial setting plotted along the line that 

indicated denitrification (fig. 8; Clark and Fritz, 1997). Sitespecific values of δ15N and δ18O are described in more detail 

in the “Characterization of Indicators of Onsite Wastewater 

Disposal Systems” section. 

Four surface-water samples were analyzed for nitrogen 

and oxygen isotope ratios for nitrate (table 29 and fig. 9). The 

sample with the highest dissolved NO2+NO3 concentration of 

1.6 mg/L (table 27, site 68) had a δ15N value of 12.36 ‰. The 

other three surface-water samples that were analyzed had dissolved NO2

+NO3 concentrations less than 1 mg/L.

Microbiological Indicators

The presence of certain microbiological organisms such 

as E. coli, fecal coliforms, enterococci, C. perfringens, and 

coliphages usually are indicative of the presence of other more 

harmful biological organisms (U.S. Environmental Protection 

Agency, 2008). Of the 108 ground-water environmental samples (combined downgradient and background wells) analyzed 

for fecal coliforms and E. coli, 9 and 14 samples (8.3 and 

13 percent), respectively, had detections. Of the 51 ground-water samples analyzed for enterococci, 21 samples (41 percent) 

had detections. Coliphages (somatic) were detected in 3 of 

the 23 ground-water samples (13 percent), and no detections 

were found in the 23 ground-water samples analyzed for 

C. perfringens. Microbiological indicators were detected more 

0

5

10

15

−5 0 5 10 15 20 25

δ18O, IN PER MIL (‰)

Hydrogeologic setting

Alluvial

Spearfish

Minnekahta

Precambrian

Mineralized

fertilizer

Soil 

organic 

matter 

Manure, 

septic system 

effluent 

Dentrification

δ15N, IN PER MIL (‰) 

−10

−5

Figure 8. Nitrogen and oxygen isotope ratios for nitrate in ground-water samples in relation to the isotopic 

composition of nitrate sources (modified from Clark and Fritz, 1997).
32 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

frequently in surface water than in ground water. Complete 

results for microbiological indicators in ground water are 

presented in table 30 in the “Supplemental Information” section. Complete results for microbiological indicators in surface 

water are presented in table 31 in the “Supplemental Information” section. 

Ground Water

Summaries of the microbiological indicators in groundwater samples for the alluvial, Spearfish, Minnekahta, and 

Precambrian settings are shown in figure 10 and presented 

in table 11. Fecal coliforms were detected most frequently 

in the Spearfish setting (19 percent), followed by the Minnekahta (9.7 percent), alluvial (9.1 percent), and Precambrian 

(2.6 percent) settings. E. coli detections were most frequent in 

the Minnekahta setting (29 percent), followed by the Spearfish 

(13 percent), alluvial (9.1 percent), and Precambrian 

(2.6 percent) settings. Enterococci were detected more 

often than fecal coliforms or E. coli in all four settings, with 

the highest detection frequency occurring in the alluvial setting (60 percent), followed by the Spearfish (45 percent), Minnekahta (35 percent), and Precambrian (33 percent) settings. 

The number of downgradient enterococci samples (48) was 

just less than one-half the number of fecal coliform and E. coli

samples (97). Coliphages were detected in one sample in the 

Precambrian setting and two samples in the Minnekahta setting. No microbiological indicators were detected in samples 

from the background wells in the Minnekahta and Precambrian settings. Background samples for the alluvial setting 

had detections of E. coli in 1 of 3 samples and enterococci in 

the 1 sample analyzed. Background samples for the Spearfish 

setting had detections of fecal coliforms in 1 of 2 samples and 

enterococci in the one sample. Because few samples (no more 

than three) were collected from background wells, background 

data for microbiological indicators might not reflect the true 

background conditions.

Surface Water

Detections of microbiological indicators in surface-water 

samples were more frequent than detections in ground-water 

samples. Summaries of the microbiological indicators in 

surface-water samples for the Precambrian setting are shown in 

table 12. Fecal coliforms were detected in 16 of 22 samples 

(73 percent), E. coli was detected in 21 of 22 samples 

(96 percent), and enterococci were detected in 5 of 10 samples 

(50 percent). C. perfringens was detected in 5 of 10 samples 

(50 percent), coliphages (somatic) were detected in 

7 of 10 samples, and coliphages (F-specific) were detected in 

1 of 10 samples.

Mineralized

fertilizer

Soil 

organic 

matter 

Manure, 

septic system 

effluent 

Dentrification

10

15

−5 0 5 10 15 20 25

δ18O, IN PER MIL (‰)

δ15N, IN PER MIL (‰) 

−10

−5

Hydrogeologic setting

Precambrian

Figure 9. Nitrogen and oxygen isotope ratios for nitrate in surface-water samples in relation to the isotopic 

composition of nitrate sources (modified from Clark and Fritz, 1997).
Water-Quality Effects, Indicators, and Isotopes of Nitrate 33

Organic Wastewater Compounds

Water samples analyzed for OWCs were collected at 

15 ground-water sites (25 samples) and 5 surface-water sites 

(10 samples) between April and November 2007. Table 32 

in the “Supplemental Information” section lists the OWC 

analytes, MRLs, frequencies of detection, and typical uses. 

Complete results for OWCs in ground water are presented in 

table 33 in the “Supplemental Information” section, and complete results for OWCs in surface water are presented in 

table 34 in the “Supplemental Information” section. 

Only one environmental sample contained an OWC—

tris-(dichloroisopropyl)phosphate—at a concentration higher 

than the laboratory MRL (table 33, site number 14 collected 

November 19, 2007). All other detections of compounds 

either resulted in an estimated quantification or could not be 

quantified. Of the 62 OWC analytes in each sample, 12 were 

detected only in environmental samples, 10 were detected in at 

least one environmental and one blank sample (not necessarily 

companion pairs), 2 were detected only in blank samples, and 

38 were not detected in any blank, environmental, or replicate 

sample in either ground or surface water. 

Ground Water

A summary of the OWC detections in ground-water 

samples is presented in table 13. Eleven different organic 

compounds were detected in ground-water samples at eight 

different sites. The largest number of compounds detected in 

any one sample was four, in a sample collected at site 23 on 

October 3, 2007. The most frequently occurring compound 

was DEET (an insect repellent), which was detected in 32 

percent of the environmental samples (excluding 6 samples 

with censored values). However, this compound also was 

present in 44 percent of the field blank samples (excluding 

6 blank samples used to censor environmental samples). The 

second most frequently occurring OWC was tetrachloroethene 

(a solvent), which was detected in 20 percent of environmental 

samples and in 4.5 percent of the blank samples. The third 

most frequently occurring compound was prometon (an herbicide), which was detected in 12 percent of the environmental 

samples and not detected in any blank samples. The only other 

compound detected more than once was triphenyl phosphate (a 

plasticizer), which was detected in 8.0 percent of the environmental samples and in 27 percent of the blank samples.

Surface Water

A summary of the OWC detections in surface-water 

samples is presented in table 14. A total of 16 organic compounds were detected in 9 of the 10 total samples. The compound with the highest occurrence in surface-water samples 

was camphor (a fumigant and flavorant), which was detected 

in five samples (50 percent; excluding two censored values). 

(11)

(16)

(31)

(39)

(11)

(16)

(31)

(39)

(5)

(11)

(23)

(9)

(6)

0

10

20

30

40

50

60

70

Alluvium Spearfish Minnekahta Precambrian

PERCENTAGE OF SAMPLES WITH DETECTIONS, (NUMBER OF SAMPLES)

HYDROGEOLOGIC SETTING

Microbiological indicator

Fecal coliform

Escherichia coli

Enterococci

Coliphage

(2) (4)

(11)

Figure 10. Summary of microbiological indicator detections in ground water for downgradient wells grouped by hydrogeologic 

setting.

Figure 10. Summary of microbiological indicator detections in ground water for downgradient samples grouped by hydrogeologic 

setting.
Table 11. Summary of microbiological indicator results for ground water. [col/100 mL, c greater than; M Setting olonies per 100 milliliters; U , presence verified but not qu Microbiological indicator Fecal coliform 1, analyzed for but antified] Units col/100 mL not detec Number of samples 11 ted; mpn/1 Mean 0.73 00 mL, most probable number p Downstream sites Median Minimum Maximum U U 8 er 100 millili Percent detection 9.1 ters; --, no Number of samples 3 data or not Mean 0 applicable; plaq/100 m Background sites Median Minimum U U L, p

Ma

Escherichia coli mpn/100 mL 11 5.1 U U 56 9.1 3 .67 U U 

Alluvial Enterococci Clostridium perfringens mpn/100 mL col/100 mL 52 4.9-- 1<1 U<1 18<1 600 10 6.4-- ---- ---- 

Coliphage (somatic)2 plaq/100 mL 2 -- U U U 0 0 -- -- -- 

Coliphage (F-specific)2 Fecal coliform plaq/100 mL col/100 mL 216 -- 4.6 <1U <1U <168 019 02 -- 3.4 -- 3.4 --U 

Escherichia coli mpn/100 mL 16 7.0 U U 99 13 2 0 U U 

Spearfish Enterococci Clostridium perfringens mpn/100 mL col/100 mL 114 20.0-- U<1 U<1 >200.5 <1 450 10 48-- ---- ---- 4

Coliphage (somatic)2 plaq/100 mL 4 -- U U U 0 0 -- -- -- 

Coliphage (F-specific)2 Fecal coliform plaq/100 mL col/100 mL 431 -- 1.2 <1U <1U <120 09.7 03 -- 0 --U --U 

Escherichia coli mpn/100 mL 31 4.3 U U 101 29 3 0 U U 

Minnekahta Enterococci Clostridium perfringens mpn/100 mL col/100 mL 2311 1.5-- U<1 U<1 21<1 350 10 0-- U-- U-- 

Coliphage (somatic)2,3 plaq/100 mL 11 -- U U M 18 0 -- -- -- 

Coliphage (F-specific)2 Fecal coliform plaq/100 mL col/100 mL 1139 --.26 <1U <1U <110 02.6 03 -- 0 --U --U 

Escherichia coli mpn/100 mL 39 .15 U U 6 2.6 3 0 U U 

Precambrian Enterococci Clostridium perfringens mpn/100 mL col/100 mL 96 .56 -- U<1 U<1 2<1 330 00 ---- ---- ---- 

Coliphage (somatic)2 plaq/100 mL 6 .17 U U 1 17 0 -- -- -- 

Coliphage (F-specific)2 plaq/100 mL 6 1U values were assumed to be zero for calculation of statistics. -- <1 <1 <1 0 0 -- -- -- 

2Summary includes results from two methods of coliphage analysis: presence or absence and quantitative. 3Presence or absence tests contained two positive samples for coliphage (somatic), but quantitative tests could not enumerate these organisms.
Characterization of Indicators of Onsite Wastewater Disposal Systems 35

Cholesterol (a plant or animal biochemical) and DEET were 

each detected in four samples (40 percent; excluding two 

censored DEET values). Tris-(2-chloroethyl) phosphate (a fire 

retardant) was detected in three samples. Compounds detected 

in two samples were isophorone (a solvent), methyl salicylate 

(a flavoring agent), phenol (a resin and a compound used in 

pharmaceutical manufacturing), and tris-(2-butoxyethyl) phosphate (a fire retardant). 

Characterization of Indicators of Onsite 

Wastewater Disposal Systems

Primary indicators used to characterize OWDS effects 

were NO2

+NO3, chloride, Cl:Br, boron, fecal coliforms, and 

E. coli. Boxplots of dissolved NO2

+NO3, chloride, bromide, 

Cl:Br, and boron for ground-water samples collected from 

downgradient wells show the range of values for these indicators in the four hydrogeologic settings (figs. 11–15). Dissolved 

NO2

+NO3 concentrations (fig. 11) were highest for sites 

downgradient from OWDS in the Spearfish and Minnekahta 

settings. Dissolved chloride concentrations (fig. 12) and Cl:Br 

(fig. 14) were highest for sites downgradient from OWDS in 

the alluvial and Minnekahta settings. Dissolved boron concentrations were highest for sites downgradient from OWDS in 

the alluvial setting (fig. 15). Results for surface-water samples 

that were collected in the Precambrian setting are described 

separately in the “Precambrian setting” section.

Nitrate nitrogen is the most substantial documented threat 

to ground water from OWDS (U.S. Environmental Protection 

Agency, 2002a); therefore, characterization of these OWDS 

indicators begins with nitrate concentrations followed by 

correlations between nitrate and co-indicators chloride, Cl:Br, 

and boron. Mean, median, and maximum concentrations of 

dissolved NO2

+NO3 in 12 background samples were 0.489, 

0.215, and 1.76 mg/L; therefore, concentrations greater than 

2.0 mg/L were assumed to potentially indicate anthropogenic 

influence. In all samples with detectable levels of dissolved 

NO2

+NO3, dissolved nitrate was the dominant form of nitrogen, and most commonly the only species of inorganic nitrogen present. For the remainder of the report, sample results 

based on dissolved NO2

+NO3 concentrations will be referred 

to simply as “nitrate” results. Dissolved ammonia as nitrogen 

was the dominant form of nitrogen at some sites in the alluvial 

setting, and these sample results will continue to be referred 

to as “ammonia” results. Site-specific descriptions of these 

indicators along with other nutrients, selected ions, isotopes of 

nitrate, microbiological indicators, and OWCs provide a more 

detailed characterization of OWDS effects.

Alluvial Setting

Dissolved nitrate concentrations in 5 of 11 downgradient samples in the alluvial setting were higher than 0.4 mg/L; 

highest concentrations were 2.61 mg/L at site 4 and 1.64 mg/L 

at site 5 (table 26). The mean dissolved nitrate in three background samples from the alluvial setting averaged 0.168 mg/L. 

The median nitrate concentration for 70 samples from alluvial 

aquifers in the Black Hills area was 0.4 mg/L (Williamson and 

Carter, 2001). 

Spearman’s rank correlation (R) is a statistical technique 

to test the direction and strength of the relation between two 

variables (Helsel and Hirsch, 1992). An R value of 1 indicates 

Table 12. Summary of microbiological indicator results for surface water.

[col/100 mL, colonies per 100 milliliters; U1, analyzed for but not detected; mpn/100 mL, most probable number per 100 milliliters; --, not 

available; plaq/100 mL, plaques per 100 milliliters; <, less than; E, estimated]

Relative site location Microbiological 

indicator Units Number of samples Mean Median Minimum Maximum Percent detection

Fecal coliform col/100 mL 12 25 14 U 98 83

Escherichia coli mpn/100 mL 12 40 25 1 105 100

Downstream

Enterococci

Clostridium perfringens

mpn/100 mL

col/100 mL

6

6

32

3.2

4.1

3.0

U

<1

162

E7

67

83

Coliphage (somatic) plaq/100 mL 6 122 23.5 <1 660 83

Coliphage (F-specific) plaq/100 mL 6 -- -- <1 1 17

Fecal coliform col/100 mL 10 11 3 U 54 60

Escherichia coli mpn/100 mL 10 18 9.5 U 76 90

Upstream (background)

Enterococci

Clostridium perfringens

mpn/100 mL

col/100 mL

4

4

.8

--

U

--

U

<1

3.1

<1

25

0

Coliphage (somatic) plaq/100 mL 4 18 10 <1 52 50

Coliphage (F-specific) plaq/100 mL 4 -- -- <1 <1 0

1

U values were assumed to be zero for calculation of statistics.
36 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Table 13. Summary of organic wastewater compound (OWC) detections in ground water.

[--, not applicable]

Setting Site Date Number of 

OWCs detected Compounds detected in environmental sample

Alluvial

5

6

06/26/07

06/26/07

1

0

Prometon.

--

11 10/29/07 1

1 DEET2, tetrachloroethene.

12 04/03/07 0 --

Spearfish 12 08/28/07 3 Benzophenone, DEET, triphenyl phosphate.

12 10/24/07 0 --

14 11/19/07 2 DEET, tris-(2-chloroethyl) phosphate.

9 07/02/07 0 --

9 08/29/07 0 --

9 10/24/07 0 --

17 04/03/07 2 DEET, tetrachloroethene.

17 06/27/07 1

0 DEET2.

17 09/06/07 2 DEET, tetrachloroethene.

Minnekahta 17 11/07/07 1

1 DEET2, tetrachloroethene.

21 04/03/07 2 Camphor, DEET.

21 06/27/07 1

1 DEET2, prometon.

21 09/06/07 0 --

21 11/07/07 1

2 DEET2, tetrachloroethene, triphenyl phosphate.

22 09/24/07 1

2 DEET2, hexahydrohexamethylcyclopentabenzopyran, prometon.

23 10/03/07 4 3-beta-Coprostanol, beta-sitosterol, cholesterol, DEET.

26 07/02/07 0 --

27 07/16/07 0 --

Precambrian 36 07/25/07 0 --

44 07/25/07 0 --

48 07/25/07 0 --

1

Value adjusted for censored result.

2

Censored because of detection in companion blank sample.

a perfect positive correlation, a value between 1 and 0.5 indicates a strong positive correlation, and a value between 0.5 and 

0 indicates a weak positive correlation. Similarly, an R value 

of -1 indicates a perfect negative correlation. The rank correlation between four indicators of OWDS influence—nitrate, 

chloride, Cl:Br, and boron—for the alluvial setting (table 15) 

indicates a strong positive correlation among chloride, Cl:Br, 

and boron. The correlation between nitrate and each of the 

three other indicators was weak or negative. Site-specific 

examination of additional constituents provides some insight 

on the lack of correlation between these constituents and 

nitrate and on the relatively low nitrate concentrations. 

The substantially larger values of δ15N and δ18O in dissolved nitrate for samples from sites 4 and 5 (fig. 8 and 

table 28) indicate that denitrification had occurred along the 

ground-water flow path to these wells. The process of denitrification requires a reduced substrate to provide the energy 

needed by nitrate-reducing bacteria. OWDS is a potential 

source of dissolved organic carbon. Another potential source 

of energy is sulfide minerals resulting in oxidation of sulfide 

to sulfate. Bottcher and others (1992) reported that sulfate concentrations in a sand and gravel aquifer increased from about 

80 to more than 250 mg/L, whereas nitrate concentrations 

remained at about 2 mg/L despite large nitrate inputs from 

intensive agriculture. Dissolved sulfate concentrations at sites 

4 and 5 ranged from 1,010 to 2,120 mg/L (table 26), which are 

considerably higher than the concentration in a background 

sample (table 26, site 2) of 280 mg/L. The potential for localized reducing conditions also was supported by the presence 

of relatively high ammonia concentrations of about 0.5 mg/L 
Characterization of Indicators of Onsite Wastewater Disposal Systems 37

at site 6. Mott and others (2004) reported a large range in sulfate concentrations in background wells in the area; therefore, 

the high dissolved sulfate concentrations also could be the 

result of natural processes in the alluvial sediments derived 

from shale bedrock units.

Dissolved chloride concentrations at downgradient sites 

3–7 ranged from 54.1 to 824 mg/L; concentrations in 6 of the 

11 samples were higher than 300 mg/L. Dissolved chloride 

concentrations for three background samples from sites 1 

and 2 ranged from 22.8 to 41.7 mg/L. A detailed map of 

flow directions and dissolved chloride concentrations based 

on samples from numerous domestic wells in the study area 

(Mott and others, 2004) shows a similar distribution of chloride. The Cl:Br ratio for the 11 samples at sites 3–7 ranged 

from 492 to 27,500, indicating anthropogenic influence. The 

extremely large ratio of 27,500 may be the result of the bromide 

divisor being near the MRL for bromide of 0.02 mg/L. Dissolved 

boron concentrations for 11 downgradient samples ranged 

from 121 to 1,060 μg/L, and for 3 background samples were 

130, 160, and 716 μg/L (table 26). The high dissolved boron 

concentration of 716 μg/L at site 1 indicates that variation in 

background dissolved boron concentrations in this aquifer 

may limit the potential of boron as an OWDS indicator. 

Providing further evidence of OWDS effects is the detection of multiple microbiological indicators at the sites where 

other constituents indicated OWDS effects. All three indicators sampled at site 4 (fecal coliforms, E. coli, and enterococci) were detected on the same sample date as the highest 

dissolved nitrate concentration (tables 26 and 30). Sites 4–6 

each had one detection of enterococci during the same time 

period. Sites 5 and 6 were each sampled for OWCs once; 

prometon was detected in the sample from site 5 (tables 13 

and 33). No microbiological indicators were detected on this 

same sample date, but the dissolved nitrate concentration at 

site 5 of 1.56 mg/L was slightly higher than concentrations at 

other wells in the area. One background site (2) had detections 

of both E. coli and enterococci in 1 of the 2 samples collected. 

Concentrations of other indicators (nitrate = 0.180 mg/L; 

boron = 130 μg/L; sulfate = 280 mg/L; chloride = 41.7 mg/L) 

in this sample were less than concentrations at other downgradient sites in the area. 

Dissolved orthophosphate concentrations were low. The 

highest concentration of 0.043 mg/L was at site 6, and the 

concentration in the background sample was 0.008 mg/L. The 

highest iron concentration of 12,400 mg/L and the highest 

manganese concentration of 1,590 were at site 6. 

The alluvial setting was characterized by relatively low 

dissolved nitrate concentrations, detection of dissolved ammonia nitrogen, and relatively high concentrations of major ions, 

particularly sulfate and sodium. Nitrogen and oxygen isotope 

results indicate that denitrification probably was occurring 

along ground-water flow paths to some wells, and that the cooccurrence of relatively high sulfate and iron concentrations 

could potentially be due to oxidation of sulfide minerals in this 

process. Dissolved chloride concentrations at downgradient 

sites were substantially higher than background concentrations. 

Table 14. Summary of organic wastewater compound (OWC) detections in surface water.

[Shading denotes upstream (background) sites; --, not applicable]

Study 

area

Site Date

Number 

of OWCs 

detected

Compounds detected in environmental sample

37 07/24/2007 1 DEET.

4

37

38

10/17/2007

07/24/2007

2

3

Cholesterol, phenol.

Camphor, DEET, methyl salicylate.

38 10/17/2007 2 Cholesterol, phenol.

67 07/23/2007 5 3-Methyl-1H-indole, camphor, cholesterol, methyl salicylate, tribromomethane.

67 09/05/2007 1

0 Camphor2.

6

68

68

07/23/2007

09/05/2007

7

1

8

Camphor, cholesterol, DEET, fluoranthene, pyrene, tris-(2-butoxyethyl) phosphate, tris-(2-chloroethyl) phosphate.

Benzophenone, camphor, cotinine, DEET2

, isophorone, tributyl phosphate, 

tris-(2-butoxyethyl) phosphate, tris-(2-chloroethyl) phosphate, tris-

(dichloroisopropyl) phosphate.

69 07/23/2007 3 Camphor, DEET, tris-(2-chloroethyl) phosphate.

69 09/05/2007 1

1 Camphor2, DEET2, isophorone.

1

Value adjusted for censored result.

2

Censored because of detection in companion blank sample.
38 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

EXPLANATION 

Data value less than or equal to 

 1.5 times the interquartile 

 range outside the quartile

75th percentile

Median

25th percentile

Interquartile 

range

11 17 33 39

HYDROGEOLOGIC SETTING

Figure 11. Boxplots of dissolved nitrite plus nitrate concentrations in ground-water samples collected from downgradient wells 

grouped by hydrogeologic setting.

39 Number of values 

Outlier data value less than or 

 equal to 3 and more than 

 1.5 times the interquartile 

 range outside the quartile

30

25

20

15

10

5

0

Alluvial Spearfish Minnekahta Precambrian

DISSOLVED NITRITE PLUS NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 11. Boxplots of dissolved nitrite plus nitrate concentrations in ground-water samples collected from downgradient wells 

grouped by hydrogeologic setting.
Characterization of Indicators of Onsite Wastewater Disposal Systems 39

x

x

x

o

o

11 17 33 39

EXPLANATION 

Data value less than or equal to 

 1.5 times the interquartile 

 range outside the quartile

75th percentile

Median

25th percentile

Interquartile 

range

HYDROGEOLOGIC SETTING

39 Number of values 

Outlier data value less than or 

 equal to 3 and more than 

 1.5 times the interquartile 

 range outside the quartile

3,500

3,000

2,500

2,000

1,500

1,000

500

0

Alluvial Spearfish Minnekahta Precambrian

DISSOLVED CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 12. Boxplots of dissolved chloride concentrations in ground-water samples collected from downgradient wells grouped by 

hydrogeologic setting.

Outlier data value greater than 

 3 times the interquartile range 

 outside the quartile

Figure 12. Boxplots of dissolved chloride concentrations in ground-water samples collected from downgradient wells grouped by 

hydrogeologic setting.
40 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

HYDROGEOLOGIC SETTING

5

4

3

2

1

0

Alluvial Spearfish Minnekahta Precambrian

DISSOLVED BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 13. Boxplots of dissolved bromide concentrations in ground-water samples collected from downgradient wells grouped by 

hydrogeologic setting.

11 17 33 39

EXPLANATION 

Data value less than or equal to 

 1.5 times the interquartile 

 range outside the quartile

75th percentile

Median

25th percentile

Interquartile 

range

39 Number of values 

Outlier data value less than or 

 equal to 3 and more than 

 1.5 times the interquartile 

 range outside the quartile

Outlier data value greater than 

 3 times the interquartile range 

 outside the quartile

Figure 13. Boxplots of dissolved bromide concentrations in ground-water samples collected from downgradient wells grouped by 

hydrogeologic setting.
Characterization of Indicators of Onsite Wastewater Disposal Systems 41

EXPLANATION 

Data value less than or equal to 

 1.5 times the interquartile 

 range outside the quartile

75th percentile

Median

25th percentile

Interquartile 

range

39 Number of values 

Outlier data value less than or 

 equal to 3 and more than 

 1.5 times the interquartile 

 range outside the quartile

Outlier data value greater than 

 3 times the interquartile range 

 outside the quartile

HYDROGEOLOGIC SETTING

35,000

30,000

25,000

20,000

15,000

10,000

5,000

0

Alluvial Spearfish Minnekahta Precambrian

CHLORIDE/BROMIDE RATIO

Figure 14. Boxplots of dissolved chloride/bromide ratios in ground-water samples collected from downgradient wells grouped by hydrogeologic 

setting.

11 17 33 39

Figure 14. Boxplots of dissolved chloride/bromide ratios in ground-water samples collected from downgradient wells grouped by 

hydrogeologic setting.
42 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

EXPLANATION 

Data value less than or equal to 

 1.5 times the interquartile 

 range outside the quartile

75th percentile

Median

25th percentile

Interquartile 

range

HYDROGEOLOGIC SETTING

42 Number of values 

Outlier data value less than or 

 equal to 3 and more than 

 1.5 times the interquartile 

 range outside the quartile

1,200

1,000

800

600

400

200

0

Alluvial Spearfish Minnekahta Precambrian

DISSOLVED BORON CONCENTRATION, IN MICROGRAMS PER LITER

Outlier data value greater than 

 3 times the interquartile range 

 outside the quartile

Figure 15. Boxplots of dissolved boron concentrations in ground-water samples collected from downgradient wells grouped by 

hydrogeologic setting.

11 17 33 42

Figure 15. Boxplots of dissolved boron concentrations in ground-water samples collected from downgradient wells grouped by 

hydrogeologic setting.
Characterization of Indicators of Onsite Wastewater Disposal Systems 43

Table 15. Spearman’s rank correlations for dissolved nitrite plus nitrate, 

chloride, chloride/bromide ratio, and boron for 11 downgradient samples 

in the alluvial setting.

[--, not applicable]

Dissolved constituent Nitrite plus 

nitrate Chloride Chloride/ bromide ratio Boron

Nitrite plus nitrate

Chloride

--

0.44

0.44

--

0.31

.95

-0.32

.56

Chloride/bromide ratio

Boron

.31

-.31

.95

.56

--

.59

.59

--

Spearfish Setting

Dissolved nitrate concentrations in 15 of 17 downgradient 

samples from sites 10–14 in the Spearfish setting were higher 

than 4.0 mg/L, and concentrations in 7 of 17 samples were 

higher than 10 mg/L (table 26). Dissolved nitrate concentrations in two background samples from site 16, completed in 

alluvium upgradient from the Spearfish setting, were 0.286 

and 0.215 mg/L. The median dissolved nitrate concentration 

for four samples from the Spearfish aquifer in the Black Hills 

area was 0.8 mg/L (Williamson and Carter, 2001). 

Spearman’s rank correlation for nitrate, chloride, Cl:Br, 

and boron for the Spearfish setting (table 16) shows a weak 

positive correlation between nitrate and Cl:Br and boron. The 

unexpected negative correlations among the four constituents 

are examined in more detail in the following site-specific 

discussion. 

Dissolved nitrate concentrations at sites 13 and 14 ranged 

from 11.2 to 14.9 mg/L (table 26) indicating substantial 

contamination. The δ15N in nitrate for four samples from these 

two sites ranged from 6.80 to 7.02 ‰ (table 28), which indicates that some mixing has occurred with other nitrate sources, 

such as synthetic fertilizer. Dissolved chloride concentrations 

at these two sites ranged from 23.7 to 37.3 mg/L. Dissolved 

chloride concentrations in two samples from background site 16 

were 3.17 and 1.19 mg/L. The median dissolved chloride concentrations for 13 samples from the Spearfish aquifer in the 

Black Hills area was 4.4 mg/L (Williamson and Carter, 2001). 

Table 16. Spearman’s rank correlations for dissolved nitrite plus nitrate, 

chloride, chloride/bromide ratio, and boron for 17 downgradient samples 

in the Spearfish setting.

[--, not applicable]

Dissolved constituent Nitrite plus 

nitrate Chloride Chloride/bromide ratio Boron

Nitrite plus nitrate

Chloride

--

-0.16

-0.16

--

0.33

-.66

0.48

.41

Chloride/bromide ratio

Boron

.33

.48

-.66

.41

--

-.08

-.08

--

Cl:Br for sites 13 and 14 ranged from 189 to 1,240, 

and dissolved boron concentrations ranged from 

55 to 101 μg/L, which are consistent with OWDS 

effects. At site 13, enterococci were detected in 

both samples during this study (table 30). Enterococci were detected at site 14 on August 29, 2007, 

at an organism concentration higher than what 

could be enumerated (>200.5 most probable number per 100 milliliters (mpn/100 mL)). However, 

sample collection at the end of August 2007 in 

study area 2 occurred days after severe flooding in 

the area was suspected to have caused contamination in many drinking-water wells. Floodwaters 

may have flowed directly down surface casings 

into some private drinking-water wells, and a 

dramatic rise in the water table possibly led to septic effluents 

flowing freely into the ground water with little filtration in the 

vadose zone.

Dissolved nitrate concentrations ranged from 2.46 to 

5.63 mg/L at site 10 and from 0.100 to 11.0 mg/L at site 11 

(table 26). The δ15N in nitrate at sites 10 and 11 ranged from 

9.55 to 10.99 ‰ (table 28). Dissolved chloride concentrations at sites 10 and 11 ranged from 103 to 304 mg/L, indicating potential effects from OWDS. Dissolved nitrate concentrations at site 12 ranged from 4.13 to 6.77 mg/L; however, 

chloride concentrations at site 12 ranged from 14.3 to 21.7 mg/L, 

which were substantially less than concentrations at nearby 

sites 10 and 11. The δ15N values for samples from site 12 were 

10.47, 8.11, and 9.09 ‰. Dissolved boron concentrations 

ranged from 52 to 132 μg/L at site 11 and from 18 to 26 μg/L 

at sites 10 and 12. Dissolved bromide concentrations ranged 

from 0.38 to 1.50 mg/L at sites 10 and 11 and from 0.03 to 

0.04 mg/L at site 12. These data indicate that local variations 

in background values for chloride, bromide, and boron in the 

Spearfish setting may complicate correlations between OWDS 

indicators. Although variation in individual indicators existed, 

substantial indications of OWDS influence were present.

Sites 11 and 12 had detections of three microbiological indicators (fecal coliforms, E. coli, and enterococci) on 

August 28, 2007 (table 30). Also at site 12 on the same date, 

three OWCs (benzophenone, DEET, and triphenyl phosphate) 

were detected (tables 13 and 33). Two OWCs—DEET and 

tetrachloroethene—were detected at site 11 on 

October 29, 2007, but the DEET detection was 

censored due to detection in the associated blank 

sample. At the background site (16), one microbiological indicator was detected in each of the two 

samples (table 30). 

The Spearfish setting was characterized by 

consistently high dissolved NO2

+NO3 concentrations—75 percent of samples having concentrations higher than 5 mg/L—and relatively frequent 

detections of microbiological indicators and 

OWCs. Nitrogen isotope results indicated that the 

nitrogen at 2 of 5 sites probably was a mixture of 

nitrogen from synthetic sources and from warm-
44 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

blooded animals (including humans). Although generally 

higher than background concentrations, dissolved concentrations of chloride, boron, and bromide varied for sites in 

proximity to each other and complicated interpretations from 

these OWDS indicators. 

Minnekahta Setting

Dissolved nitrate concentrations in 28 of 33 downgradient 

samples from sites 8, 9, and 17–23 were higher than 4.0 mg/L; 

concentrations in 8 samples were higher than 10 mg/L (table 26). 

Dissolved nitrate concentrations in three background samples 

from sites 15 and 24 in the Minnekahta setting ranged from 

0.967 to 1.76 mg/L. Median dissolved nitrate concentrations 

for 23 samples from the Minnekahta aquifer in the Black Hills 

area was 0.7 mg/L (Williamson and Carter, 2001). 

Spearman’s rank correlation for nitrate, chloride, Cl:Br, 

and boron for the Minnekahta setting (table 17) shows a strong 

positive correlation between nitrate and chloride, Cl:Br, and 

boron. The correlation between nitrate and boron (0.92) was 

especially strong approaching a 1-to-1 rank correlation.

The δ15N in nitrate for 17 of 23 samples was higher than 

9 ‰ (table 28), which indicated that warm-blooded animals 

were the probable source of nitrate (predominantly from 

OWDS effluents). Site 18 was notably different with δ15N values of 6.52 and 6.73 ‰ (table 28), which indicated potential 

mixing with nitrate sources other than warm-blooded animals. 

This site was near quarrying operations that include the use 

explosives, which can be a source of nitrate. The δ15N in 

nitrate related to explosives is about 3 ‰ (McQuillan, 2004). 

The lowest dissolved nitrate concentrations for the Minnekahta setting were in samples from site 9 and ranged from 

1.95 to 3.45 mg/L (table 26). Dissolved chloride and dissolved 

boron concentrations also were the lowest at site 9, ranging from 8.16 to 21.4 mg/L and 16 to 25 μg/L, respectively. 

The well at site 8 was dry except for the period following the 

heavy rains in August 2007 when dissolved concentrations for 

nitrate, chloride, and boron were 3.22 mg/L, 520 mg/L, and 

37 μg/L, respectively. The dissolved bromide concentration 

was also much higher at site 8, resulting in a Cl:Br ratio of 214.

Site 9 had multiple detections of indicator bacteria on 

three different sample dates (table 30). E. coli and enterococci 

Table 17. Spearman’s rank correlations for dissolved nitrite plus nitrate, 

chloride, chloride/bromide ratio, and boron for 33 downgradient samples 

in the Minnekahta setting.

[--, not applicable]

Dissolved constituent Nitrite plus 

nitrate Chloride Chloride/bromide ratio Boron

Nitrite plus nitrate

Chloride

Chloride/bromide ratio

Boron

--

0.71

.66

.92

0.71

--

.35

.74

0.66

.35

--

.59

0.92

.74

.59

--

were detected on July 2, 2007. Four indicators (fecal coliforms, E. coli, enterococci, and coliphages) were detected on 

August 29, 2007, following the heavy rains in late August, and 

E. coli and coliphages were detected on October 27, 2007. 

No OWCs were detected in environmental samples at site 9 

(tables 13 and 33). No microbiological indicators were 

detected at site 8 in August following the heavy rains.

Six time-series samples were collected at site 17 

(fig. 16A). Dissolved nitrate concentrations at site 17 ranged 

from 7.42 to 9.79 mg/L (table 26), whereas the mean concentration for background samples in the Minnekahta setting was 

1.37 mg/L (table 8). Dissolved chloride concentrations at site 

17 ranged from 133 to 175 mg/L, whereas the mean concentration for background samples was 18.2 mg/L. Cl:Br ranged 

from 2,390 to 4,100; background samples had a mean of 509. 

Dissolved boron concentrations at site 17 ranged from 42 to 

46 μg/L; background samples had a mean of 23 μg/L. Dissolved bromide concentrations were uniformly low, ranging 

from 0.04 to 0.07 mg/L. The relatively steady values of indicators with time probably was the result of increased groundwater mixing that likely occurred between the OWDS and the 

140-ft deep Minnekahta Limestone well (site 17), which was 

the farthest downgradient well from OWDS. The trends in 

dissolved sulfate and sodium concentrations did not follow the 

same trend as nitrate and chloride concentrations. No microbiological indicators were detected at site 17 (table 30). DEET 

was detected in all four OWC samples at site 17 (tables 13 

and 33); however, DEET also was detected frequently in field 

blanks and was censored in two of the samples from site 17. 

Tetrachloroethene, a solvent, was detected in 3 of the 4 OWC 

samples at site 17. 

Samples from site 18, as mentioned previously, may have 

included some nitrate from explosives in the dissolved nitrate 

that ranged in concentration from 4.41 to 5.21 mg/L (table 26). 

Chloride concentrations at this site ranged from 69.9 to 115 mg/L. 

The relatively high dissolved bromide concentrations resulted 

in Cl:Br that ranged from 69 to 344. Dissolved boron concentrations ranged from 27 to 35 μg/L. No microbiological indicators were detected at this site (table 30). No OWC samples 

were collected at this site.

Samples from sites 19 and 20 had high dissolved nitrate 

concentrations that ranged from 

9.35 to 20.8 mg/L. Dissolved chloride concentrations in the three samples from site 19 were 

extremely high (mean = 2,500 mg/L); however, 

concentrations were much lower in nearby site 20 

during the same period (mean = 264 mg/L). The 

extremely high dissolved chloride concentrations 

at site 19 could have resulted from water-softener 

backwashing or road salting. Site 20 had the highest mean dissolved boron concentration (169 μg/L) 

in the Minnekahta setting. Fecal coliforms and 

E. coli were both detected in 1 of 2 samples at 

site 20, and neither indicator was detected in 

2 samples at site 19 (table 30). Enterococci were 

detected at both sites in the one sample collected 
Characterization of Indicators of Onsite Wastewater Disposal Systems 45

0

100

200

300

400

0

200

400

600

800

DISSOLVED CHLORIDE, SODIUM, AND SULFATE CONCENTRATIONS, IN MILLIGRAMS PER LITER

DATE

Water-quality 

 constituent

Chloride

Sodium

Sulfate

Nitrite plus nitrate

Figure 16. Time-series concentrations of dissolved chloride, sodium, sulfate, and nitrite plus nitrate at (A) site 17, 

(B) site 21, and (C) site 22. 

0

400

200

800

600

1,600

1,400

1,200

1,000

0

4

8

12

0

4

8

12

16

DISSOLVED NITRITE PLUS NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER

0

8

4

16

12

32

28

24

20

Aug. 2006 Nov. 2006 Feb. 2007 May 2007 Aug. 2007 Nov. 2007 Feb. 2008

EXPLANATION 

A Site 17

B Site 21

C Site 22

Figure 16. Time-series concentrations of dissolved chloride, sodium, sulfate, and nitrite plus nitrate at A, site 17, B, site 21, and 

C, site 22.
46 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

at each site. No OWC samples were collected from sites 19 

and 20 because the wells did not contain sufficient amounts of 

water during field visits.

Time-series samples were collected from sites 21 and 22 

(figs. 16B and 16C). The mean dissolved nitrate concentrations were 15.0 mg/L for site 22 and 6.6 mg/L for site 21. The 

δ15N values for eight samples from sites 21 and 22 ranged 

from 11.12 to 13.21 ‰ indicating that the nitrate source was 

probably warm-blooded animals and the most likely source of 

the high nitrate concentrations was OWDS. Similar trends over 

time among dissolved nitrate, chloride, sodium, and sulfate 

concentrations (figs. 16B and 16C) indicate the origin was from 

a consistent contaminant source. Increases in dissolved sodium 

and chloride in the winter 2008 sample could be due in part to 

road salt and to less recharge diluting the OWDS effluent.

Owing to the strong correlation between boron and nitrate 

concentrations (table 17), the mean dissolved boron concentrations of 37 and 151 μg/L at sites 21 and 22, respectively, were 

consistent with the mean nitrate concentrations of 6.6 mg/L 

and 15.0 mg/L, respectively. Dissolved bromide concentrations were consistently low, ranging from 0.03 to 0.07 mg/L 

in 10 of the 11 samples, and the one sample with a concentration of 0.23 mg/L confirmed that the high dissolved chloride 

concentrations were from anthropogenic sources. Dissolved 

orthophosphate concentrations were low; however, the mean 

concentration was 0.028 mg/L at site 21 and 0.191 mg/L at 

site 22, which also had relatively high dissolved nitrate concentrations.

At least one microbiological indicator was detected in 4 of 

the 6 samples at site 21 (table 30). Two microbiological indicators were detected in 1 of the 5 samples from site 22. Other 

than DEET, which was detected in 4 of the 5 environmental 

samples and in all 4 blank samples at sites 21 and 22, there 

were 5 other OWCs detected at these 2 sites (tables 13 and 33). 

At site 21, camphor was detected on April 3, 2007, prometon 

on June 27, 2007, and tetrachloroethene and triphenyl phosphate on November 7, 2007. Prometon and hexahydrohexamethylcyclopentabenzofuran (HHCB; a fragrance) were detected 

in the sample from site 22 on September 24, 2007.

Dissolved nitrate concentrations at site 23 ranged from 

4.04 to 6.87 mg/L (table 26), which were substantially higher 

than background concentrations. For the samples with nitrate 

concentrations of 5.49 and 6.87 mg/L, values of δ15N 

in nitrate were 9.63 and 7.94 ‰, respectively (table 

28), which indicated that some mixing with other 

nitrate sources such as synthetic fertilizer could have 

occurred. Dissolved chloride concentrations for site 

23 ranged from 312 to 858 mg/L, and higher chloride concentrations corresponded to higher nitrate 

concentrations. Cl:Br for site 23 ranged from 134 

to 1,950; the relatively high dissolved bromide concentration in the first sample resulted in the smaller 

Cl:Br. This high concentration could have resulted 

from the small amount of water in the well and 

slow recovery during sample collection. Dissolved 

boron concentrations ranged from 40 to 42 μg/L. At 

site 23, enterococci were detected in both samples that were 

analyzed for microbiological indicators (table 30). Four OWCs 

(3-beta-coprostanol, beta-sitosterol, cholesterol, and DEET) 

were detected in the October 3, 2007, sample (tables 13 and 33).

In the Minnekahta setting, most indicator concentrations 

were higher in downgradient samples than in background 

samples, and correlations between indicators in the same 

sample were strong. Mean, median, and maximum dissolved 

nitrate concentrations for the Minnekahta setting were 8.62, 

7.42, and 24.3 mg/L, respectively—the highest of the four 

hydrogeologic settings. Nitrogen isotope results indicate that 

the probable nitrate source in 17 of the 23 samples was OWDS 

effluents. OWCs were detected in more than one-half of the 

samples (8 of 13 samples after censoring; table 13), and E. coli

and coliphages were detected more frequently in the Minnekahta setting than in any other hydrogeologic setting. 

Precambrian Setting

The characterization of OWDS indicators in the Precambrian setting is grouped by ground water and surface water. 

Organization of the ground-water section is similar to that of 

the previous sections. The surface-water section focuses on 

comparison of upstream results to downstream results. 

Ground Water

Dissolved nitrate concentrations in 7 of the 39 downgradient samples from sites 25–36 and 39–52 were higher than 

4.0 mg/L; no concentrations were higher than 10 mg/L 

(table 26). Dissolved nitrate concentrations in three background samples from sites 53–55 in the Precambrian setting 

were 0.246 mg/L or less. The median dissolved nitrate concentration for 40 samples from the Precambrian aquifer in the 

Black Hills area was 0.7 mg/L (Williamson and Carter, 2001). 

Spearman’s rank correlations for nitrate to chloride and 

to Cl:Br show a strong correlation (table 18). Dissolved boron 

was weakly correlated to the other indicators for the Precambrian setting. Two of the background samples had boron 

concentrations equal to or higher than 80 μg/L, which indicated that variability in natural boron concentrations may limit 

Table 18. Spearman’s rank correlations for dissolved nitrite plus nitrate, 

chloride, chloride/bromide ratio, and boron for 39 downgradient samples in 

the Precambrian setting.

[--, not applicable]

Dissolved constituent Nitrite plus 

nitrate Chloride Chloride/bromide ratio Boron

Nitrite plus nitrate

Chloride

Chloride/bromide ratio

Boron

--

0.64

.52

.19

0.64

--

.77

.43

0.52

.77

--

.23

0.19

.43

.23

--
Characterization of Indicators of Onsite Wastewater Disposal Systems 47

boron as an indicator of OWDS influence in the Precambrian 

setting.

The mean concentrations of dissolved nitrate for study 

areas 4, 5, and 6 were 3.24, 2.06, and 0.320 mg/L, respectively. Dissolved chloride concentrations showed the same 

trend with mean values of 40.4, 33.1, and 17.0 mg/L for study 

areas 4, 5, and 6, respectively. Cl:Br showed the same trend 

with mean values of 798, 600, and 231 for study areas 4, 5, 

and 6, respectively. The mean dissolved boron concentration 

were 30, 70, and 21 μg/L for study areas 4, 5, and 6, respectively.

In study area 4, sites 26, 27, and 36 had the highest dissolved nitrate concentrations, with means of 5.00, 6.06, and 

8.03 mg/L, respectively. The δ15N value of 11.66 ‰ for site 26 

(table 28) indicated warm-blooded animals as the primary 

nitrate source. Because there were no indications of domestic 

livestock upgradient from site 26, the high dissolved nitrate 

concentration (maximum 5.06 mg/L) represented OWDS 

influence. Dissolved chloride concentrations for site 26 of 

78.2 and 87.2 mg/L were the highest in study area 4. 

Coliphages were detected in the second sample collected from 

site 26 (table 30). 

Dissolved nitrate concentrations in two samples from 

site 27 were 8.53 and 3.59 mg/L (table 26), and the second 

sample had a δ15N value of 6.39 ‰ (table 28), which indicated 

mixing of animal nitrate sources with other nitrate sources 

such as synthetic fertilizer. Dissolved chloride concentrations were 8.23 and 6.63 mg/L, which are some of the lowest 

chloride concentrations in the Precambrian setting and are 

consistent with a nitrate source other than OWDS. The well at 

site 27 was a shallow well near Rapid Creek. Enterococci were 

detected in the second sample collected at site 27 (table 30).

Dissolved nitrate concentrations in two samples from 

site 36 were 8.11 and 7.94 mg/L (table 26), and the second 

sample had a δ15N value of 10.34 ‰ (table 28), which indicated warm-blooded animals as the primary source of the 

nitrate. Dissolved chloride concentrations were 59.9 and 

58.8 mg/L, respectively, which were about double the median 

concentration of 26.8 mg/L for downgradient wells in the 

Precambrian setting (table 9). Site 36 is a spring with a steady 

discharge of about 12 gal/min that is downgradient from small 

livestock pastures. E. coli was detected in the first sample collected from site 36 (table 30).

For the remainder of the sites in the northern part of study 

area 4, the mean dissolved nitrate concentration was 1.94 

mg/L, which indicated possible anthropogenic influence at 

some sites. Two out of the three samples in parts of study area 

4 (near Prairie Creek) had dissolved nitrate concentrations less 

than the MRL (sites 40 and 41), and the third (site 39) had a concentration of 1.34 mg/L. Dissolved boron was not an effective 

indicator of OWDS effects in study area 4, as concentrations 

were relatively low compared to concentrations in Precambrian background samples.

The density and location of sampled wells and OWDS 

in study area 5 were adequate to create nitrate and chloride 

concentration maps (figs. 17 and 18, respectively). For sites 

with more than one sample, the mean nitrate and chloride 

concentrations were used in constructing the maps. The data 

for site 45, near Rapid Creek, were excluded from this analysis 

because the well at this site was 83 ft deep and was assumed 

to be inducing flow from Rapid Creek during pumping. The 

general direction of ground-water flow was assumed to follow 

the topography, which slopes towards Rapid Creek at a gradient of about 1 ft per 10 ft. Dissolved nitrate concentrations 

increased in a downgradient direction from less than the MRL 

for upgradient samples (sites 46–47 and 51–54) to higher than 

6 mg/L at a downgradient site. Dissolved chloride concentrations increased from less than 10 mg/L at most upgradient 

sites to higher than 50 mg/L at some downgradient sites. 

The highest dissolved nitrate concentrations in study 

area 5 were at sites 44 and 48. Three samples from site 44 had 

dissolved nitrate concentrations of 6.22, 6.66, and 7.12 mg/L 

(table 26), and δ15N values of 12.74 and 12.81 ‰ (table 28), 

which indicated warm-blooded animals as the primary nitrate 

source. Dissolved chloride concentrations at site 44 were 63.8, 

65.6, and 64.2 mg/L, whereas concentrations at background 

sites in study area 5 (sites 53 and 54) were less than 4 mg/L. 

Enterococci were detected in the second sample from site 44 

(table 30). Dissolved nitrate concentrations for two samples 

from site 48 were 2.59 and 3.58 mg/L, and the second sample 

had a δ15N value of 10.68 ‰, which indicated warm-blooded 

animals as the primary source of nitrate. Dissolved chloride 

concentrations were 55.7 and 56.1 mg/L at site 48. Enterococci were detected in the second sample from site 48. The 

only detections of microbiological indicators in study area 5 

were at the sites that also had the highest dissolved nitrate 

concentrations. No OWCs were detected in samples from 

sites 44 and 48 (tables 13 and 33). 

Wells sampled in study area 6 showed the least effects 

of anthropogenic influence of any area in the study. The only 

site that could be considered as having concentrations higher 

than background values was site 59, which had the highest 

dissolved concentrations of nitrate (1.56 mg/L), chloride 

(56.2 mg/L), and boron (48 μg/L) in study area 6. All other 

sites in the study area had dissolved nitrate concentrations less 

than 1 mg/L, chloride concentrations less than 27 mg/L, and 

boron concentrations less than 20 μg/L.

No OWCs were detected in any of the five analyzed 

samples from the Precambrian setting (table 13). Microbiological indicators were detected in 6 out of the 39 downgradient samples (each detection at a different site) collected in 

the Precambrian setting. Microbiological indicator detections 

occurred in study area 4 (sites 26, 27, and 36), study area 5 

(sites 44 and 48), and the shallow well at site 25 in study 

area 3. 

Effects of OWDS varied among the different Precambrian study areas, but water-quality evidence indicated that 

water samples from the Precambrian wells generally were 

not as affected by anthropogenic influences as wells in other 

hydrogeologic settings. However, the direct comparison of 

OWDS indicator results to other settings is questionable, as all 

of these wells were previously established private drinking-
48 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

103°33’52” 103°33’45”

44°05’05”

44°05’

Dissolved nitrite plus nitrate concentration, 

 in milligrams per liter

0−0.75

0.75−1.5

1.5−2.5

2.5−3.5

3.5−6.67

Approximate location of onsite wastewater disposal system (Sawyer, 2006)

Sampled well and mean dissolved nitrite plus nitrate concentration in milligrams per liter

Approximate direction of ground-water flow

0 5025 100 METERS

0 125 250 500 FEET

R. 5 E. 

T. 2 N.

Base from U.S. Geological Survey digital data, 1977, 1:100,000 

Universal Transverse Mercator projection

Zone 13

EXPLANATION

Figure 17. Distribution of dissolved nitrite plus nitrate concentrations in study area 5, June-July, 2007.

1.01 6.67

1.11

3.09

0.234

0.225

<0.016 <0.016

<0.016

<0.016 <0.016

<0.016

1.01 6.67

3.09

0.234

<0.016 <0.016

<0.016

<0.016 <0.016

<0.016

Silver City

Rapid Creek

<0.016

0.225

1.11

Figure 17. Distribution of dissolved nitrite plus nitrate concentrations in study area 5, June–July 2007.
Characterization of Indicators of Onsite Wastewater Disposal Systems 49

2

6

1

3

35

43 65

14

56

16 20

14

2

6

1

3

35

43 65

14

56

16 20

14

14

103°33’52” 103°33’45”

44°05’05”

44°05’

Dissolved chloride concentration, 

 in milligrams per liter

0−15

15−25

25−35

35−50

50−65

Approximate location of onsite wastewater disposal system (Sawyer, 2006)

Sampled well and mean dissolved chloride concentration in milligrams per liter

Approximate direction of ground-water flow

0 5025 100 METERS

0 125 250 500 FEET

R. 5 E. 

T. 2 N.

Base from U.S. Geological Survey digital data, 1977, 1:100,000 

Universal Transverse Mercator projection

Zone 13

EXPLANATION

Figure 18. Distribution of dissolved chloride concentrations in study area 5, June-July, 2007.

Silver City

Rapid Creek

Figure 18. Distribution of dissolved chloride concentrations in study area 5, June–July 2007.
50 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

water sources compared to the strategically placed monitoring wells used in the other three settings. Concentrations of 

dissolved nitrate, chloride, and boron in more than one-half 

of the samples from Precambrian wells were not substantially 

higher than concentrations in background samples. Maximum 

dissolved nitrate concentrations for three sites in study area 4 

that ranged from 5.06 to 8.53 mg/L probably resulted from 

OWDS effects. Microbiological indicators detected included 

fecal coliforms and E. coli, and they were detected only in 

2.6 percent of ground-water samples. No OWCs were detected 

in any of the five samples. A pattern of increasing nitrate and 

chloride concentrations in the downgradient direction was 

observed for study area 5, which had 13 closely spaced sampling sites. The use of boron as an indicator of OWDS effects 

in the Precambrian setting may be limited because background 

concentrations of boron were naturally occurring and highly 

varied.

Surface Water

Characterization of OWDS effects in surface water generally is more difficult than characterization of OWDS effects 

in ground water because there are additional potential sources 

of contaminants to surface water, such as wildlife wastes, 

road salts, and recreational uses of the water. For this study, 

surface-water sites were sampled during the summer and early 

fall (when road salts probably were not used); therefore, more 

emphasis is placed on indicators specific to OWDS effluent, 

such as boron, chloride, and OWCs, rather than on nitrate and 

microbiological indicators, which also may originate from 

sources such as fertilizers or wildlife feces. 

Nitrate concentrations ranged from less than MRL to 

1.60 mg/L for downstream sites (38, 64, 66, 68, and 69), and 

from an estimated 0.008 to 0.844 mg/L for upstream sites 

(37, 63, 65, and 67; tables 10 and 27). Fecal coliforms were 

detected in 10 of the 12 downstream samples, and in 6 of the 

10 upstream samples (tables 12 and 31). E. coli was detected 

in all 12 of the downstream samples and 9 of the 10 upstream 

samples. The similarities of nitrate, fecal coliform, and E. coli

results in both upstream and downstream data sets indicate 

that these indicators are not as effective as wastewater tracers 

in surface water as they are in ground water. 

Dissolved boron concentrations ranged from 10 to 70 μg/L 

and had a mean of 28 μg/L for downstream sites; concentrations at upstream sites had mean of 16 μg/L (table 10). Dissolved chloride concentrations ranged from 2.83 to 73.4 mg/L 

and had a mean of 32.1 mg/L for downstream sites; concentrations at upstream sites had a mean of 13.6 mg/L. Concentrations of most other major ions and trace elements were similar 

between upstream and downstream sites. The mean dissolved 

calcium concentrations were 45.1 and 47.1 mg/L for upstream 

and downstream sites, respectively, and the mean dissolved 

magnesium concentrations were 22.1 and 19.6 mg/L, respectively. Concentrations of dissolved orthophosphate and 

sodium at upstream sites were lower than concentrations at 

downstream sites. Orthophosphate concentrations had means 

of 0.007 and 0.011 mg/L for upstream and downstream sites, 

respectively, and sodium concentrations had means of 4.50 and 

17.6 mg/L for upstream and downstream sites, respectively.

Differences in mean indicator concentrations between 

upstream and downstream sites were examined for statistical 

significance using a paired t-test (Montgomery and Runger, 

2007). This parametric test uses paired values (upstream and 

downstream sample results) to assess the probability that the 

difference in sample means is due to random chance. Specifically, this tests the null hypothesis that the two data sets have 

no difference in true population means, whereas the alternative 

hypothesis is that the means are different. A p-value is calculated, which is the probability of rejecting the null hypothesis 

(no difference in means) when it is in fact true (means are different; Miller and Ortiz, 2007). The p-value is approximately 

equal to the probability that the difference in mean values is 

due to random chance rather than to a significant difference in 

data sets; therefore, lower p-values (typically <0.05) indicate a 

potential source of the wastewater indicator between upstream 

and downstream sites. The p-value between upstream and 

downstream sites was 0.001 for dissolved chloride, 0.014 for 

dissolved boron, 0.037 for fecal coliforms, and 0.046 for E. coli. 

These p-values, which are less than 0.05, indicate significant 

differences in these constituents between upstream and downstream sites. The p-value for dissolved nitrate was 0.360, indicating that the difference between upstream and downstream 

sites was not significant. These test results indicated that 

anthropogenic influence in surface water in the Precambrian 

setting may be detected more clearly with chloride and boron, 

followed by the microbiological indicators fecal coliforms and 

E. coli. Because boron is more specifically related to OWDS 

than the other constituents, boron may be a useful indicator 

when background concentrations are low.

No major differences in water quality were apparent 

between upstream sites on Rapid Creek and the downstream 

sites (study area 4, fig. 5). Dissolved nitrate concentrations in 

July and October 2007 (table 27) were estimated at 0.011 and 

0.008 mg/L for the upstream site (37) and were <0.016 and 

0.035 mg/L for the same sample dates at the downstream site 

(38). The δ15N value was 10.08 ‰ for the sample from site 38 

that had a nitrate concentration of 0.035 mg/L (table 29), indicating that a large proportion of the low nitrogen concentration 

was of warm-blooded animal origin. Dissolved chloride and 

boron concentrations also were similar between upstream and 

downstream sites in study area 4. Dissolved chloride concentrations were 2.41 and 2.50 mg/L for two upstream samples 

(site 37) and 2.83 and 4.75 mg/L for the corresponding downstream samples (site 38). Dissolved boron concentrations were 

10 and 11 μg/L for two upstream samples and 10 and 13 μg/L 

for the corresponding downstream samples. Fecal coliform 

results for the two sites were identical: 4 colonies per 100 milliliters (col/100 mL) in July 2007 and undetected in October 

2007 (table 31). E. coli was detected at 2 and 

14 mpn/100 mL for upstream and downstream sites, respectively, in July 2007, and was detected at 1 mpn/100 mL at 

both sites in October 2007. The relatively high flows of Rapid 
Characterization of Indicators of Onsite Wastewater Disposal Systems 51

Creek (compared to other surface-water sites sampled) may 

have diluted concentrations of OWDS indicators that potentially migrate to the stream.

Differences in concentrations of dissolved chloride, dissolved boron, fecal coliform, and E. coli between upstream 

and downstream sites were much larger in study area 6 (fig. 7) than 

in study area 4 (fig. 5), but differences for dissolved nitrate 

concentrations between upstream and downstream sites were 

not significant. From upstream site 63 to downstream site 64, 

mean dissolved chloride concentrations increased from 1.58 to 

7.67 mg/L. At the same sites, mean dissolved boron concentrations increased from 14 to 18 μg/L. Mean fecal coliform 

values increased from 10 to 19 col/100 mL. Mean E. coli

values increased from 28 to 58 mpn/100 mL. With the exception of one fecal coliform and E. coli sample, all indicator 

concentrations increased from upstream to downstream in this 

tributary. Between upstream site 65 and downstream site 66, 

mean dissolved chloride concentrations increased from 35.7 

to 53.6 mg/L, but mean dissolved boron concentrations were 

similar, changing from 23 to 25 μg/L. Mean fecal coliform 

values increased from 2 to 9 col/100 mL, and mean E. coli

values increased from 9 to 15 mpn/100 mL. Chloride was the 

only indicator that showed a consistent trend of increasing 

from upstream to downstream at these sites.

Moving downstream from sites 67 to 68 to 69 on Spring 

Creek, mean dissolved chloride concentrations changed 

from 9.4 to 52.2 to 44.8 mg/L. Site 68 had the highest mean 

dissolved nitrate concentration (1.60 mg/L) of any surfacewater site (table 27). At the same sites, mean dissolved boron 

concentrations changed from 18 to 55 to 38 μg/L. The mean 

fecal coliform value changed from 33 to 45 to 59 col/100 mL, 

and the mean E. coli value changed from 31 to 54 to 

68 mpn/100 mL. Nitrogen isotope results from two samples at 

site 68 had a mean of 11.98 ‰, indicating that the nitrogen in 

nitrate was from warm-blooded animals. At site 69, one δ15N 

sample was 7.40 ‰ (table 29), indicating that the nitrogen in 

nitrate had a substantial proportion of natural organic matter or synthetic fertilizer sources rather than warm-blooded 

animal sources. The nitrate concentration in this sample was 

very low (0.029 mg/L), so the isotope results may not be as 

useful as results from samples with higher concentrations. A 

shallow impoundment of Spring Creek (Mitchell Lake, fig. 7) 

lies between sites 68 and 69, and has been known to act as a 

nutrient sink (Swanson, 2004). This may explain the difference in concentrations and origins of nitrogen between sites 68 

and 69. 

Upstream sites had fewer detections of OWCs than downstream sites. The upstream site in study area 4 (site 37) had 

one compound detected on July 24, 2007, and two compounds 

detected on October 17, 2007 (tables 14 and 34). Three compounds were detected at the downstream site in study area 4 

(site 38) on July 24, 2007, and two compounds were detected 

on October 17, 2007. In study area 6 on July 23, 2007, 5 compounds were detected at the upstream site (67), 7 compounds 

were detected at site 68, and 3 compounds were detected at 

the farthest downstream site (69). On September 5, 2007, no 

compounds were detected at the upstream site, 8 compounds 

were detected at site 68, and 1 compound was detected at the 

farthest downstream site. 

Compounds detected only at downstream sites include 

camphor and methyl salicylate at site 38; isophorone, DEET, 

and tris-2-chlorethyl phosphate (a fire retardant) at sites 68 

and 69; and tris-(2-butoxyethyl) phosphate (a fire retardant), 

fluoranthene, pyrene (pavement and combustion-derived 

compounds), cotinine (a nicotine metabolite), and benzophenone (a photo initiator) at site 68. Cholesterol was detected 

equally at upstream sites and the corresponding downstream 

sites; it was detected at sites 37 and 38 on October 17, 2007, 

and at sites 67 and 68 on July 23, 2007, in study area 6. 

Similar trends were observed for phenol and DEET detections at sites 37 and 38 on the same dates. No conclusions 

can be drawn about suspected OWDS effects on the basis of 

these particular compounds occurring at both upstream and 

downstream sites. 

Differences in chemical indicators of OWDS effects 

between upstream and downstream sites were not always 

evident, except for two sites downstream from Hill City and 

residential development, where dissolved chloride and boron 

concentrations were substantially higher than the upstream 

site. Statistical tests on dissolved chloride, dissolved boron, 

fecal coliforms, and E. coli data for all surface-water sites 

indicated that a statistically significant difference existed 

between upstream and downstream sites. Statistical tests on 

dissolved nitrate data indicated that the difference between 

upstream and downstream sites was not statistically significant. Microbiological indicators and OWCs were frequently 

detected in both upstream and downstream surface-water 

samples in the Precambrian setting, but the concentrations 

of microbiological indicators and number of OWCs detected 

were greater in downstream samples. 

Relation Between Onsite Wastewater Disposal 

System Density and Nitrate Concentrations

Densities of OWDS were calculated for nine estimated 

contributing areas to the ground water near selected sites in the 

Spearfish, Minnekahta, and Precambrian settings. These areas 

were determined by using geographical information system 

(GIS) software to estimate the outcrop areas upgradient from 

sampled wells (figs. 3–5). Topography was used as the basis 

for approximating the contributing area where the outcrop 

boundary was not well defined. The OWDS inside these 

boundaries were counted and the numbers divided by the area 

to determine the OWDS density for each well, group of wells, 

or spring. Well or spring groupings and their site numbers 

are listed in table 19 along with each grouping’s respective 

contributing area, OWDS density, and median concentrations 

of dissolved nitrate. As described previously, nitrate is the primary form of nitrogen in these samples owing to exposure to 

oxygen and the resulting nitrification near OWDS drain fields. 

For this study, nitrate is considered the primary indicator of 
52 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

OWDS effluent given its ability to persist in the same form 

after reaching the aerobic ground water. 

Figure 19 shows a positive correlation between median 

dissolved nitrate concentrations and OWDS density. Using 

OWDS density as the independent variable and median dissolved nitrate concentration as the dependent variable, a 

90 percent confidence interval about the regression line was 

calculated according to Montgomery and Runger (2007). 

Confidence intervals about the linear regression line of the 

data give a range of values for a given OWDS density. For 

example, according to analysis of the data collected in this 

study, 90 percent of downgradient samples collected from 

areas with OWDS density of about 150 per square mile will 

have a dissolved nitrate concentration between 3 and 8 mg/L 

(there is a 10 percent chance the concentration will be outside 

this range). A general range in nitrate concentration can be 

obtained for any given OWDS density. 

Note that the actual observed downgradient nitrate concentrations are highly varied; therefore, accurate estimation of 

concentration for a given OWDS density is difficult. The data 

includes a combination of the Spearfish, Minnekahta, and Precambrian settings (no data from the alluvial setting). Also, the 

data were collected during a period of below normal precipitation and may not represent a complete range of hydrologic 

conditions. Analysis of this data provides a general characterization of the probability of higher nitrogen concentrations as 

OWDS density increases. 

Evaluation of Onsite Wastewater Disposal 

System Indicators

Hydrogeologic setting, land use, and hydrologic conditions are important considerations in the evaluation of OWDS 

indicators in the east-central Black Hills area. Nitrate was 

useful as a primary indicator of OWDS influence in most 

hydrogeologic settings. Traditional OWDS with septic tanks 

and drain fields are designed to break down organic matter in 

an aerobic environment. Ammonia, the predominant nitrogen 

species in anaerobic septic tank effluent, generally is transformed to nitrate before the effluent percolates to the water 

table. All water samples in the Spearfish, Minnekahta, and 

Precambrian settings had very low concentrations of dissolved 

ammonia. Dissolved ammonia concentrations in samples from 

one monitoring well in the alluvial setting were substantially 

higher than background concentrations indicating locally 

anoxic conditions.

Nitrate is relatively stable in aerobic ground water. Most 

sampling sites in the study areas were relatively close to formation outcrops where recharge occurs and aerobic conditions 

prevail. In background samples collected at sites where wild 

animals and decaying plant matter were the probable dissolved 

nitrate source, nitrate concentrations generally were less than 

1 mg/L and concentrations in many samples were less than 

0.1 mg/L. On the basis of background concentrations, dissolved nitrate concentrations higher than 2 mg/L were 

assumed to potentially indicate anthropogenic influence. 

Table 19. Density of onsite wastewater disposal systems (OWDS) and median dissolved nitrite plus 

nitrate concentrations for selected site groupings.

[Shaded row denotes background sites, OWDS, onsite wastewater disposal system; mi2, square miles; mg/L, milligrams 

per liter; N, nitrogren; --, not applicable]

Sites included

Approximate 

contributing 

area (acres) 

Number of 

OWDS

(count)

OWDS density 

(number/mi2

)

Median 

dissolved nitrite 

plus nitrate 

concentration 

(mg/L as N)

Setting

15–16, 24, 53–55

8–9

21–22

26

17

19–20

10–12

36

23

13–14

--

304

251

124

105

72

138

265

109

57

0

32

48

28

26

18

44

88

48

36

0

67

122

144

158

160

204

213

282

404

1

0.7

2.80

9.41

5.00

8.55

14.0

5.33

8.03

5.49

12.4

Background.

Minnekahta.

Minnekahta.

Precambrian.

Minnekahta.

Minnekahta.

Spearfish.

Precambrian.

Minnekahta.

Spearfish.

1

Median values of nitrate for the Spearfish, Minnekahta, and Precambrian aquifers (0.7, 0.7, and 0.8 mg/L, respectively) 

reported in Williamson and Carter (2001) were factored into the median for this grouping. 
Characterization of Indicators of Onsite Wastewater Disposal Systems 53

0

2

4

6

8

10

12

14

16

18

0 50 100 150 200 250 300 350 400 450

NITRITE PLUS NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER

OWDS DENSITY, IN NUMBER PER SQUARE MILE

Background sites

Sites in the Spearfish hydrogeologic setting

Sites in the Minnekahta hydrogeologic setting

Sites in the Precambrian hydrogeologic setting

Linear fit to data

90-percent confidence interval 

 about regression line 

EXPLANATION

Median dissolved nitrite plus nitrate 

 concentration

Maximum Contaminant Level for nitrite 

 plus nitrate (U.S. Environmental 

 Protection Agency, 2008) 

Figure 19. Relation between median dissolved nitrite plus nitrate concentration and density of onsite 

wastewater disposal systems (OWDS) in dry hydrologic conditions. 

y = 0.0327x + 0.7

 R2

 = 0.21

Figure 19. Relation between median dissolved nitrite plus nitrate concentration and density of onsite wastewater 

disposal systems (OWDS) in dry hydrologic conditions. 

Seventy-five percent of ground-water samples had dis- In settings where other potential nitrogen sources existed, 

solved nitrate concentrations higher than 2 mg/L, 50 percent analysis of nitrogen isotopes in nitrate provided clarification 

had concentrations higher than 5 mg/L, and 18 percent had of potential mixing of nitrate from OWDS with nitrate from 

concentrations higher than 10 mg/L. Dilution is the primary other synthetic nitrogen sources such as non-organic fertilizers 

mechanism for attenuation of nitrate in aerobic ground water. or explosives. Synthetic nitrogen sources have δ15N values 

Because of the prevailing dry conditions and limited dilution of about 0 ‰, compared to about 10 to 20 ‰ for sewage or 

from recharge, dissolved nitrate concentrations probably were manure. The δ15N values in 22 percent of the 46 downgradient 

higher than those that would have been observed in normal to samples that were analyzed for nitrogen isotopes in the nitrate 

wet hydrologic conditions. fraction were less than 8 ‰, indicating potential mixing of 
54 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

some synthetic nitrogen sources with predominantly animal 

nitrate sources.

Although denitrification was unlikely in most settings, 

nitrogen and oxygen isotopes in nitrate were useful in identifying nitrate concentrations that were diminished by denitrifying 

bacteria. In the alluvial setting, two downgradient sites had 

distinctly higher δ15N and δ18O values than other sites that 

indicated denitrification had occurred.

When other sources of nitrogen were present, additional indicators were useful in characterizing the influence 

of OWDS. Boron, which is used in laundry detergents and 

cleaning products, was a complementary indicator of OWDS 

influence in some hydrogeologic settings. In the Minnekahta 

setting, where background dissolved boron concentrations 

were low and the predominant nitrate source was OWDS, 

a very strong correlation existed between nitrate and boron 

concentrations. The effectiveness of boron to characterize OWDS in the other hydrogeologic settings, however, is 

uncertain because boron concentrations were highly varied at 

background sites. 

Chloride, which is a stable chemical tracer in ground 

water, was almost always detected at higher concentrations 

downgradient from OWDS. The wide range of chloride 

concentrations that can be present in OWDS effluent limited 

some statistical analysis of the relation between chloride 

and OWDS effects. Chloride concentrations downgradient 

from areas where water softeners were used extensively to 

treat hard water could be an order of magnitude greater than 

concentrations in areas downgradient from households where 

water softeners were not used. However, when compared to 

a mean dissolved background concentration of 14.6 mg/L, 

chloride concentrations were excellent indicators of anthropogenic influence. Road salt is an additional potential source of 

chloride during the winter, especially in areas with steep and 

winding roads. Dissolved chloride concentrations in downgradient water samples ranged from less than 100 mg/L to higher 

than 1,000 mg/L, and had a mean of 228 mg/L.

The ratio of chloride to bromide generally is higher in 

ground water influenced by sewage. However, the wide range 

in chloride concentrations and the predominance of bromide 

concentrations near the MRL resulted in some extremely large 

Cl:Br ratios in all hydrogeologic settings. Subtle variations in 

bromide concentrations resulted in substantial change in Cl:Br, 

which limited the usefulness of site-by-site comparisons. The 

low concentrations of dissolved bromide in relation to dissolved chloride indicated that downgradient increases in chloride concentrations were the result of anthropogenic influence. 

Dissolved phosphate and orthophosphate concentrations 

were slightly higher in downgradient wells than in background wells. However, all values were less than 0.3 mg/L, 

and samples at several sites that had high dissolved nitrate 

concentrations had dissolved phosphate and orthophosphate 

concentrations near the MRL. Variation in sodium and sulfate 

concentrations in natural waters limits the usefulness of these 

constituents as indicators of OWDS effects. However, timeseries concentrations of dissolved sodium and sulfate for two 

sites (21 and 22) in the Minnekahta setting that were close 

to the Minnekahta Limestone outcrop (fig. 4) had trends that 

were similar to those of nitrate and chloride (figs. 16B and 

16C). Time-series concentrations of dissolved sodium and 

sulfate for a deeper well in the Minnekahta setting that was 

located farther from the outcrop (fig. 5, site 17) had trends that 

were different from those of nitrate and chloride (fig. 16A). 

Comparison of time-series concentrations of sodium and sulfate with those of nitrate and chloride could provide insight on 

whether the well was directly connected with OWDS effluent.

The microbiological indicators E. coli and fecal coliforms 

were useful indicators of OWDS effluents in ground water 

because these bacteria originate only from warm-blooded 

animals. The presence of these organisms in the ground water 

is indicative of animal wastes; however, no differentiation 

between animal species (for example, humans, dogs, cats, and 

deer) was made in this study. Fecal coliforms and E. coli in 

ground water likely originated from OWDS effluent and not 

from percolation of other animal wastes on the outcrop areas, 

but the source was not verified through investigation. Because 

fecal coliforms and E. coli are susceptible to filtration as they 

travel through aquifer materials, they may indicate groundwater areas with a direct connection to OWDS effluents. Fecal 

coliforms were detected most frequently in the Spearfish setting (19 percent of downgradient samples; table 11); however, 

40 percent of sites sampled immediately following the severe 

flooding in this area tested positive for both fecal coliforms 

and E. coli, which may have skewed the detection percentages 

for this setting. Following the Spearfish setting, the Minnekahta and alluvial settings had the most frequent detections of 

fecal coliforms (9.7 and 9.1 percent, respectively). E. coli

was detected most frequently in the Minnekahta setting 

(29 percent of downgradient samples; table 11), which is 

characterized by areas with fractures and solution-enhanced 

conduits where ground water is subject to limited filtration. 

Detections of fecal coliforms and E. coli in the Precambrian 

setting were rare (2.6 percent for each indicator), which may 

indicate that aquifer materials in this setting provide better 

filtration of bacteria than aquifer materials in the other three 

settings. The fewer detections in the Precambrian setting also 

could be the result of uncertainty in ground-water flow directions and fewer upgradient OWDS for some sampling sites. 

Enterococci were detected more frequently than other 

microbiological indicators in all four settings. The highest 

frequency of detection occurred in the alluvial setting 

(60 percent) followed by the Spearfish (45 percent), Minnekahta (35 percent) and Precambrian (33 percent) settings 

(table 11). The persistence of enterococci in soils or other 

porous materials may explain the frequent detections of 

enterococci in ground-water samples compared to detections of fecal coliforms and E. coli. When the sampling site 

is farther away from an OWDS, the aquifer material filters 

more of the coliform bacteria compared to sampling sites 

closer to OWDS effluents, particularly when the ground-water 

flow velocities are relatively low (Freeze and Cherry, 1979). 

Enterococci can survive for a longer time in the ground water 
Summary 55

(U.S. Geological Survey, 2005); however, because they can 

persist through the filtering and percolation process, they have 

a greater chance than fecal coliforms and E. coli of reaching 

the water table from surface sources (wildlife or domestic animal waste, surface waters, or vegetation), especially in areas 

with a shallow unsaturated zone. Results of this study agree 

with the persistence of enterococci, as they were detected the 

most frequently of any microbiological indicator in all four 

hydrogeologic settings. The uncertainty is greater when trying 

to identify the origin of enterococci compared to the origin of 

fecal coliforms and E. coli, and inferences about the connection between enterococci and OWDS are limited. 

C. perfringens was not detected in any ground-water 

samples. Detection of this spore-forming bacterium may be 

unlikely in ground water except where there are direct connections to OWDS through large fractures or solution openings. 

Coliphages were detected in three ground-water samples, 

providing evidence that viruses are capable of transport in the 

Minnekahta and Precambrian settings. Of the two categories 

of coliphages analyzed, somatic coliphages and F-specific 

coliphages, all three detections were of somatic coliphages. 

Similar to the presence of microbiological indicators, 

the presence of OWCs in ground water can be indicative of 

OWDS effluents. OWC sources include many residential 

activities, such as lawn care (herbicides) and automobile usage 

(hydrocarbons), so OWDS are not the only source of these 

compounds in the study area. Although present in all OWDS 

effluents, OWCs may not be detected downgradient, because 

adsorption, physical filtration, or microbiological processes 

can remove the compounds or degrade them into other compounds that were not investigated. OWCs were detected in 

50 percent of downgradient samples from the alluvial setting, 

60 percent of downgradient samples in the Spearfish setting, 

and 62 percent of downgradient samples in the Minnekahta 

setting. No OWCs were detected in the six samples from 

the Precambrian setting. Because no more than 4 of the 62 

analyzed OWCs were detected in any one sample, and some 

OWCs could be associated with other residential activities, 

OWCs may not be a strong primary indicator of OWDS effects 

in ground water when sampling sites are beyond a certain distance downgradient. OWCs emanating from OWDS probably 

had sufficient traveltime to degrade or adsorb to aquifer materials, either of which would explain why so few compounds 

were detected. If sampling wells were closer to the OWDS 

(or directly in the drain field), the frequency of detections 

and concentrations of OWCs probably would be higher. The 

proportion of ground-water recharge that can be attributed to 

OWDS must also be considered, as some sites may have a sufficient quantity of natural recharge to dilute the OWC concentrations below reporting levels. 

Surface-water indicator results may give more insight into 

the effects of residential activities in general, as direct runoff 

probably contributes a greater proportion of the indicator load 

than OWDS effluents. Sources of indicators for surface water 

are much different from those for ground water, as animal 

wastes, fertilizers, herbicides, road salts, and other anthropogenic materials are washed directly into streams, whereas they 

can be attenuated when percolating water moves through the 

unsaturated zone towards ground water. In general, differences 

in chemical indicator results between upstream and downstream surface-water sites were not as great as differences in 

results between background and downgradient ground-water 

sites. Detections of microbiological indicators and OWCs were 

more frequent in surface-water samples as the result of little 

filtration between the source and sampling site. Surface-water 

indicator results demonstrate effects of residential development on the water quality of the stream, because the increased 

anthropogenic source load and contaminant mobility can 

increase indicator concentrations in streams. However, some 

indicators, such as bacteria and nutrients originating from 

wildlife in the watershed, can be attributed to sources other 

than residential development. Owing to substantial indicator 

sources other than OWDS, surface-water results may not provide direct evidence of OWDS effects. The presence of higher 

boron concentrations in downstream samples, however, may 

be indicative of OWDS effects because the primary source of 

boron is household products that end up in OWDS effluents. 

The proportion of boron originating from direct runoff (such 

as animal wastes, fertilizers, and herbicides) is less than that of 

other indicators used in this study. 

Summary

Onsite wastewater disposal systems (OWDS, typically 

including a septic tank and a drain field) are used extensively 

in the Black Hills of South Dakota where many of the watersheds and aquifers are characterized by fractured or solutionenhanced bedrock with thin soil cover. Population growth in 

unincorporated areas of the Black Hills is rapid where OWDS 

commonly are used for wastewater treatment. A cooperative study between the U.S. Geological Survey (USGS), the 

West Dakota Water Development District, and the South 

Dakota Department of Environment and Natural Resources 

(SD DENR) was begun in 2006 to characterize water-quality 

effects and indicators of OWDS in order to better understand 

the potential effects of OWDS on ground- and surface-water 

quality in the east-central Black Hills area. The first phase of 

the study included identification of sampling sites in areas 

with substantial densities of OWDS and analysis of initial 

OWDS indicators. Additional samples were collected in 

2007–08 from sites that had concentrations in initial samples 

that were greater than background concentrations and were 

analyzed for a detailed set of indicators and water-quality 

constituents. 

This report presents water-quality effects and characterization of indicators of OWDS for both ground water and 

surface water in four hydrogeologic settings in the east-central 

Black Hills area. Sampling sites were described for six study 

areas, which included Rapid City and the surrounding communities through Piedmont on the north, Silver City on the 
56 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

west, Hill City on the southwest, and Green Valley on the 

east. Study areas were in the Elk, Boxelder, Rapid, and Spring 

Creek watersheds. The data presented represent relatively 

dry hydrologic conditions as below-normal precipitation has 

prevailed in the study areas since 2000. 

Water samples were collected from each study site at 

least once and analyzed for potential wastewater indicators, including chloride, bromide, boron, nitrite plus nitrate 

(NO2

+NO3), ammonia, and the microbiological indicators 

fecal coliforms and Escherichia coli (E. coli). Additional 

constituents included major ions, nutrients, selected trace elements, and isotopes of nitrate; additional microbiological indicators enterococci, Clostridium perfringens (C. perfringens), 

and coliphages; and organic wastewater compounds (OWCs). 

Chloride was used as a wastewater indicator because it 

typically occurs in low concentrations in natural waters. Ratios 

of chloride concentrations to bromide concentrations (Cl:Br) 

also were used as indicators because they are smaller in natural water than in wastewater. Boron concentrations that are 

higher than background concentrations may indicate OWDS 

influence because boron is contained in cleaning products. 

NO2

+NO3 originate from OWDS and other anthropogenic 

sources such as synthetic fertilizers, animal wastes, explosives, 

and decomposing organic matter. Isotopes of nitrate are useful 

in distinguishing animal sources of nitrate from fertilizer and 

in identifying denitrification. The microbiological indicators fecal coliforms, E. coli, and enterococci are bacteria that 

are found in human and animal wastes. C. perfringens is a 

surrogate for spore-forming, stress-resistant organisms, and 

coliphages are viral indicators. Organic compounds used in or 

produced by household, industrial, and agricultural activities 

have been shown to occur in wastewater discharges.

Sixty ground-water sampling sites were located either 

downgradient from areas of dense OWDS or in background 

areas and included 25 monitoring wells, 34 private wells, and 

1 spring. Nine surface-water sampling sites were located on 

selected streams and tributaries either downstream or upstream 

from residential development within the Precambrian hydrogeologic setting. Site locations were described in six study 

areas in relation to hydrogeologic units and locations of 

OWDS. Sampling results were grouped in four hydrogeologic 

settings: alluvial, Spearfish, Minnekahta, and Precambrian. 

The alluvial setting included seven monitoring wells 

completed in the alluvium along Rapid Creek that ranged in 

depth from 15 to 27 feet (ft). The study area included about 

240 households with OWDS in approximately one-half square 

mile (mi2

). The Spearfish setting included five wells completed in the Spearfish Formation that ranged in depth from 

40 to 50 ft. The screened interval penetrated the weathered 

upper part of the Spearfish Formation that was overlain by 

about 20 to 30 ft of gravel deposits. Land use was primarily 

residential developments but included commercial enterprises. 

The Minnekahta setting included 11 wells completed in the 

Minnekahta Limestone that ranged in depth from 51 to 325 ft 

and had screened intervals of 27 to 42 ft that fully penetrated 

the Minnekahta Limestone. Residential developments with 

OWDS were on the Minnekahta Limestone outcrop upgradient 

from the monitoring wells. The Precambrian setting included 

21 private wells, predominantly completed in the Precambrian rocks that generally were less than 200 ft deep. Five 

wells were shallow and completed in alluvium overlying the 

Precambrian rocks. One site was a spring discharging from 

Precambrian rocks. Land use was primarily residential but 

included commercial development along major roadways. 

Mean downgradient dissolved NO2

+NO3 concentrations 

in ground water for the alluvial, Spearfish, Minnekahta, and 

Precambrian settings were 0.734, 7.90, 8.62, and 2.25 mg/L, 

respectively, whereas background concentrations were 0.168, 

0.250, 1.37, and 0.087 mg/L. Mean downgradient dissolved 

chloride concentrations in ground water for the alluvial, 

Spearfish, Minnekahta, and Precambrian settings were 324, 

89.6, 498, and 33.2 mg/L, respectively, whereas background 

concentrations were 31.6, 2.18, 18.2, and 2.14 mg/L. Mean 

downgradient dissolved boron concentrations in ground water 

for the alluvial, Spearfish, Minnekahta, and Precambrian 

settings were 736, 53, 64, and 43 μg/L, respectively, whereas 

background concentrations were 335, 14, 23, and 61 μg/L. 

Dissolved sodium and sulfate concentrations in the alluvial 

setting were higher at downgradient sites than at the background site. Downgradient sites in the alluvial setting had 

means of 428 and 1,730 mg/L, respectively, and concentrations in the one background sample were 34.6 and 280 mg/L. 

Mean dissolved surface-water concentrations of NO2

+NO3, 

chloride, and boron for downstream sites were 0.222 mg/L, 

32.1 mg/L, and 28 μg/L, respectively, compared to 0.192 mg/L, 

13.6 mg/L, and 16 μg/L, for upstream (background) sites. 

Mean δ15N (ratio of 15N to 14N relative to a standard) 

and δ18O (ratio of 18O to 16O relative to a standard) values for 

nitrate in 48 downgradient ground-water samples were 10.4 

and -2.0 per mil (‰), respectively, indicating a relatively small 

nitrate contribution from synthetic fertilizer and probably 

a substantial contribution from OWDS. Four surface-water 

samples were analyzed for δ15N; the surface-water sample with 

the highest dissolved NO2

+NO3 concentration (1.6 mg/L) had 

a δ15N value of 12.36 ‰, indicating warm-blooded animals 

(including humans) as the nitrate source.

Of the 108 ground-water environmental samples (downgradient and background sites) analyzed for fecal coliforms 

and E. coli, 9 and 14 samples (8.3 and 13 percent), respectively, had detections. Of the 51 samples analyzed for enterococci, 21 samples (41 percent) had detections. C. perfringens 

was not detected in the 23 samples analyzed, and coliphages 

(somatic) were detected in 3 of the 23 samples (13 percent). 

Microbiological indicators were detected more frequently 

in surface water than in ground water. Fecal coliforms were 

detected in downgradient ground water the most frequently 

in Spearfish setting (19 percent), followed by the Minnekahta 

(9.7 percent), alluvial (9.1 percent), and Precambrian (2.6 percent) 

settings. E. coli was detected most frequently in the Minnekahta setting (29 percent), followed by the Spearfish (13 percent), alluvial (9.1 percent), and Precambrian (2.6 percent) settings. 

Enterococci were detected more frequently than other micro-
Summary 57

biological indictors in all four settings; the highest frequency 

of detection occurred in the alluvial setting (60 percent) followed by the Spearfish (45 percent), Minnekahta (35 percent), 

and Precambrian (33 percent) settings. No microbiological 

indicators were detected in samples from background wells 

in the Minnekahta and Precambrian settings. Background 

samples for the alluvial setting had detections of E. coli in 1 

of the 3 samples and enterococci in the 1 sample analyzed. 

Background samples for the Spearfish setting had detections 

of fecal coliforms in 1 of the 2 samples and enterococci in 

both samples.

Fecal coliforms were detected in 16 of 22 surface-water 

samples (73 percent), E. coli was detected in 21 of 22 samples 

(96 percent), and enterococci were detected in 5 of 10 samples 

(50 percent). Coliphages (somatic) were detected in 7 of 

10 surface-water samples (70 percent), and C. perfringens was 

detected in 5 of 10 samples (50 percent). 

Twenty-five water samples collected at 15 ground-water 

sites and 10 water samples collected at 5 surface-water sites 

were analyzed for OWCs. Only one environmental sample 

contained an OWC—tris-(dichloroisopropyl)phosphate—at a 

concentration higher than the laboratory minimum reporting 

level. All other detections of OWCs were at concentrations 

that either required estimation or could not be quantified. Of 

the 62 compounds analyzed, 12 were detected only in environmental samples, 10 were detected in at least one environmental and one blank sample (not necessarily companion pairs), 

2 were detected only in blank samples, and 38 were not 

detected in any blank, environmental, or replicate sample in 

either ground or surface water. 

Eleven different organic compounds were detected in 

ground-water samples at eight different sites. The largest 

number of compounds detected in any one sample was four. 

The most frequently occurring compound was DEET, which 

was detected in 32 percent of the environmental samples. The 

second most frequently occurring OWC was tetrachloroethene, 

which was detected in 20 percent of the environmental 

samples. The third most frequently occurring compound was 

prometon, which was detected in 12 percent of the environmental samples. 

A total of 16 organic compounds were detected in 9 out 

of the 10 surface-water samples. The compound with the most 

frequent occurrence in surface-water samples was camphor, 

which was detected in 50 percent of samples. Cholesterol and 

DEET were each detected in 40 percent of samples. 

The alluvial setting was characterized by relatively low 

dissolved NO2

+NO3 concentrations, detection of dissolved 

ammonia nitrogen, and relatively high concentrations of major 

ions, particularly dissolved sulfate and sodium. Nitrogen and 

oxygen isotope results indicated that denitrification probably 

was occurring in a few wells. Dissolved chloride concentrations at downgradient sites were substantially higher than 

background concentrations. 

The Spearfish setting was characterized by consistently 

high dissolved NO2

+NO3 concentrations—75 percent of samples had concentrations higher than 5 mg/L—and relatively 

frequent detections of microbiological indicators and OWCs. 

Nitrogen isotope results indicated that the source of nitrogen 

for 2 of the 5 sites probably was a mixture of nitrogen from 

synthetic sources and nitrogen from warm-blooded animals. 

Although concentrations of chloride, boron, and bromide 

generally were higher than background concentrations, the 

variability in the concentrations in proximal areas complicated 

interpretations from these OWDS indicators. 

In the Minnekahta setting, most indicator concentrations 

in downgradient samples were higher than background concentrations, and correlations between indicators in the same 

sample were strong. Mean, median, and maximum downgradient dissolved NO2

+NO3 concentrations for the Minnekahta setting were 8.62, 7.42, and 24.3 mg/L, respectively—the highest 

of the four hydrogeologic settings. Nitrogen isotope results 

indicated that the probable nitrate source was warm-blooded 

animals and that OWDS was the predominant source of the 

high nitrate concentrations in 17 of the 23 samples. OWCs 

were detected in more than one-half of the samples, and E. coli

and coliphages were detected more frequently in the Minnekahta setting than in any other hydrogeologic setting.

Effects of OWDS varied among the different Precambrian 

study areas, but water-quality evidence indicated that water 

samples from the Precambrian wells generally were not as 

affected by anthropogenic influences as wells in other hydrogeologic settings. However, the direct comparison of OWDS 

indicator results to other settings is questionable, as all of the 

wells in the Precambrian setting were previously established 

private drinking-water sources in contrast to the strategically 

placed monitoring wells used in the other three settings. More 

than one-half of the samples from Precambrian wells did not 

contain dissolved nitrate, chloride, or boron concentrations 

that were substantially higher than concentrations in background samples. Maximum dissolved NO2

+NO3 concentrations for three sites in study area 4 that ranged from 5.06 to 

8.53 mg/L probably reflected OWDS effects. Microbiological 

indicators detected were fecal coliform and E. coli, and they 

were only detected in 2.6 percent of ground-water samples. No 

OWCs were detected in any of the five samples. Nitrate and 

chloride concentrations increased in the downgradient direction in study area 5, which had 13 closely spaced sampling 

sites. The use of boron as an indicator of OWDS effects in 

the Precambrian setting may be limited because background 

concentrations of boron were naturally occurring and highly 

varied.

Differences in chemical indicators of OWDS effects 

between upstream and downstream surface-water sites were 

not always evident; however, statistical tests on dissolved chloride, dissolved boron, fecal coliforms, and E. coli data indicated that data from upstream sites were statistically different 

from data from downstream sites. Statistical tests on dissolved 

NO2

+NO3 data from upstream and downstream sites indicated 

that the difference was not statistically significant. Microbiological indicators and OWCs were frequently detected in 

both upstream and downstream surface-water samples in the 

Precambrian setting, but the concentrations of microbiologi-
58 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

cal indicators and numbers of OWCs detected were higher in 

downstream samples. 

Densities of OWDS were calculated for nine estimated 

contributing areas to the ground water near selected sites in 

the Spearfish, Minnekahta, and Precambrian settings. A positive correlation between downgradient dissolved NO2

+NO3

concentration and OWDS density was observed. Confidence 

intervals about the linear regression line of the data give a 

range of values that could be expected for a given OWDS density. The analysis indicated a 90-percent chance that dissolved 

NO2

+NO3 concentrations would be between 3 and 8 mg/L for 

an OWDS density of 150 per square mile. The interpretation 

of this trend is only a general characterization because the data 

were from several settings and downgradient nitrate concentrations were highly variable. 

On the basis of background concentrations, dissolved 

NO2

+NO3 concentrations higher than 2 mg/L were assumed 

to potentially indicate anthropogenic influence. Seventy-five 

percent of ground-water samples had dissolved NO2

+NO3 concentrations higher than 2 mg/L, 50 percent had concentrations 

higher than 5 mg/L, and 18 percent had concentrations higher 

than 10 mg/L. The δ15N values in 22 percent of the 

46 downgradient ground-water samples that were analyzed for 

nitrogen isotopes in the nitrate fraction were less than 8 ‰, 

indicating potential mixing of some synthetic nitrogen sources 

with predominantly animal sources. In the alluvial setting, two 

downgradient sites had distinctly higher δ15N and δ18O values 

that indicated denitrification.

In the Minnekahta setting, where background dissolved 

boron concentrations were low and the predominant nitrate 

source was OWDS, a very strong correlation existed between 

dissolved NO2

+NO3 and boron concentrations. Dissolved chloride concentrations, when compared to a mean background 

concentration of 14.6 mg/L, were excellent indicators of 

anthropogenic influence. Dissolved chloride concentrations in 

downgradient water samples ranged from less than 100 mg/L 

to higher than 1,000 mg/L, and had a mean of 228 mg/L. Road 

salt is an additional potential source of chloride during the 

winter, especially in areas with steep and winding roads. The 

low concentrations of dissolved bromide in relation to chloride 

indicated that downgradient increases in chloride concentrations were the result of anthropogenic influence. 

The microbiological indicators fecal coliform and E. coli

were useful indicators of OWDS effluents. For ground-water 

samples, fecal coliforms were detected the most frequently in 

the Spearfish setting (16 percent of downgradient samples). 

E. coli was detected most frequently in the Minnekahta setting 

(29 percent of downgradient samples), which is characterized 

by subsurface fractures and solution-enhanced conduits where 

there is little to no filtration of ground water. Enterococci were 

detected the most frequently of any microbiological indicator in all four hydrogeologic settings. C. perfringens was 

not detected in any ground-water samples. Coliphages were 

detected in three ground-water samples, providing evidence 

that viruses are capable of transport in the Minnekahta and 

Precambrian settings.

Surface-water indicator results may give more insight 

into the effects of residential activities in general, as direct 

runoff probably contributes a greater proportion of the indicator load than OWDS effluents. In general, differences in 

chemical indicator results between upstream and downstream 

surface-water sites were not as great as differences in results 

between background and downgradient ground-water samples.

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37 p.
62 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota
Supplemental Information 63

Supplemental Information
Table 20. Field-equipment blank results for selected physical properties, major ions, nutrients, and selected trace elements. [Shading denotes background site. USGS, U.S. Geological Survey; μS/cm, microsiemens per centimeter; --, no data; <, less than; mg/L, milligrams per liter; μg/L, micrograms p

Number Constituent concentration Constituent (USGS parameter code) Units of samples Site 5 10/10/06 Site 9 07/02/07 Site 15 11/19/07 Site 17 Site 21 Site 32 01/10/08 01/10/08 06/21/07 Site 

06/12

Specific conductance, water whole, laboratory (90095) pH, water whole, laboratory (00403) Acid neutralizing capacity, laboratory (90410) Calcium, dissolved (00915) Magnesium, dissolved (00925) Sodium, dissolved (00930) Potassium, dissolved (00935) Sulfate, dissolved (00945) Chloride, dissolved (00940) Fluoride, dissolved (00950) Bromide, dissolved (71870) Silica, dissolved (00955) Nitrogen, ammonia, dissolved (00608) Nitrogen, nitrite, dissolved (00613) Nitrogen, NO +NO , dissolved, (00631) 2 3 Phosphorous, dissolved (00666) Orthophosphate, dissolved (00671) Boron, dissolved (01020 Iron, dissolved (01046) Manganese, dissolved (01056) μS/cm standard units mg/L as CaCO3 mg/L as Ca mg/L as Mg mg/L as Na mg/L as K mg/L as SO4 mg/L as Cl mg/L as F mg/L as Br mg/L as Si mg/L as N mg/L as N mg/L as N mg/L as P mg/L as P μg/L as B μg/L as Fe μg/L as Mn 44444444949494944944 ---------------- 0.24 <.02 <.020 <.016 ---- <1.8---- <38.1 <5<.02 <.014 <.20 <.04 <.18 <.12 <.10 <.02 <.02 <.020 <.002 <.016 <.006 <.006 <1.8 <6<.2 37.3 E3.04 <.020 <.12 <.02 <.18 <.12 <.12 <.02 E.01 <.020 <.002 <.016 <.006 <.006 <1.2 <8<.4 <38.1 <6<.04 <.020 <.12 <.02 <.18 <.12 <.12 <.02 <.02 <.020 <.002 <.016 <.006 <.006 <1.2 <8<.4 <36.1 <6<.04 <.020 <.12 <.02 <.18 <.12 <.12 <.02 <.02 <.020 <.002 <.016 <.006 <.006 <1.2 <8<.4 ---------------- <0.12 <.02 -- <.020 <.016 ---- <1.8---- ---------------- <0.1

<.0

-- <.0

<.0

---- <1.8---- 
Table 21. Relative percent difference between field replicate and environmental samples for selected physical properties, major ions, nutrients, and [Shading denotes background/upstream sites. USGS, U.S. Geological Survey; μS/cm, microsiemens per centimeter--, no data; mg/L, milligrams per liter; μg/L, micrograms per 

Constituent (USGS parameter code) Units

Number

of 

samples

Relative percent difference

Site 5

10/10/06

Site 9

07/02/07

Site 15

11/19/07

Site 17

01/10/08

Site 21 Site 22 Site 32

01/10/08 09/19/07 06/21/07

Site 37

07/24/07

Specific conductance, water whole, laboratory (90095) μS/cmpH, water whole, laboratory (00403) standard units

Acid neutralizing capacity, laboratory (90410) mg/L as CaCO3

Calcium, dissolved (00915) mg/L as CaMagnesium, dissolved (00925) mg/L as MgSodium, dissolved (00930) mg/L as NaPotassium, dissolved (00935) mg/L as KSulfate, dissolved (00945) mg/L as SO4

Chloride, dissolved (00940) mg/L as ClFluoride, dissolved (00950) mg/L as FBromide, dissolved (71870) mg/L as BrSilica, dissolved (00955) mg/L as SiNitrogen, ammonia, dissolved (00608) mg/L as NNitrogen, nitrite, dissolved (00613) mg/L as NNitrogen, NO +NO , dissolved, (00631) 2 3 mg/L as N

Phosphorous, dissolved (00666) mg/L as POrthophosphate, dissolved (00671) mg/L as PBoron, dissolved (01020 μg/L as BIron, dissolved (01046) μg/L as FeManganese, dissolved (01056) μg/L as Mn

66666666

11

6

11

6

11

6

11

66

11

66

----------------

0.0

--.0--.0--

2.5

----.7----

0.01.4

.3.7.0.4.9.1.5

10.5

.0.1.0.0.0

6.93.45.4

.0.0

0.51.3

.0.8

2.61.92.3

.0.6.0.0.9.0.0.0

22.2

.0.0.0.0

0.6

.0.0.4.4

2.0

.6.3.7

5.0

.0.0.0.0.0.0

8.74.5

.0

3.5

0.02.8

.0

1.0

.4.0.8.8.6

10.2

.0.9.0.0.0.0

5.4

.0.0

11.8

2.34.2

24.2

2.72.7

.7

6.01.85.66.6

.0

1.9

.0.0.0

5.64.25.1

.0

9.5

----------------

0.3

--.0--.0--

2.5

----

3.0

----

0.21.2

.6.5.4

2.31.3

.2.4

3.9

.0.2.0.0.0

28.6

.0.0.0

1.2
66 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Table 22. Relative percent difference between field replicate and environmental samples for nitrogen and oxygen 

isotope ratios for nitrate in ground water.

[Shading denotes background site. USGS, U.S. Geological Survey]

Constituent (USGS parameter code) Units

Number

of 

samples

Relative percent difference

Site 9

07/02/07

Site 15 Site 17 Site 21

11/19/07 09/06/07 01/10/08

Site 22

09/19/07

δ15N in nitrate fraction, water (82690) per mil 5 2.9 1.4 1.4 0.6 4.3

δ18O in nitrate fraction, water (63041) per mil 5 51.5 1.5 .0 4.5 14.0

Table 23. Concentrations of microbiological indicators in environmental and companion replicate samples.

[Shading denotes background/upstream sites. col/100 mL, colonies per 100 milliliters; mpn/100 mL, most probable number per 100 milliliters; 

U, analyzed for but not detected, --, no data]

Site

number Date Other

identifier

Fecal coliform,

(col/100 mL)

Escherichia coli,

(mpn/100 mL)

Enterococci,

(mpn/100 mL)

Environmental Replicate sample sampleEnvironmental Replicate 

sample sample

Environmental Replicate 

sample sample

Ground water

5 10/10/06 GV2 U U U U -- --

15 11/19/07 SS4 U U U U U U

22 09/19/07 BP-S U U 4 1 1 1

51 06/12/07 -- U U U U -- --

58 07/17/07 -- U U U U -- --

Surface water

37 07/24/07 RC1 4 U 2 4 U 3.1

66 05/31/06 Reno1 12 16 16 21 -- --

66 09/26/06 Reno1 16 18 27 22 -- --

67 05/31/06 Reno2 2 4 14 8 -- --
Table 24. Measurements of physical properties in ground water.[Shading denotes background sites. Collection method: P, pumped; B, bailed, T, tap near production well or spring. gal/min, gallons per minute; μS/cm, microsiemens per centimmm of Hg, millimeters of mercury; mg/L, milligrams per liter; --, no data]

Site

number

Station

identification

number

Date

Other

identifier

Collection 

method

Flow 

rate

(gal/

min)

(00059)

Specific

conductance, water 

whole, field

(μS/cm)

(00095)

Specific 

conductance, water 

whole,

laboratory

(μS/cm)

(90095)

pH,

water 

whole,

field

(standard 

units)

(00400)

pH,

water 

whole, 

laboratory 

(standard 

units)

(00403)

Air 

temperature

(deg C) 

(00020)

Water 

temperature

(deg C) 

(00010)

Barometric

pressure

(mm of Hg)

(00025)

Dissolved 

oxygen

(mg/L)

(00300)

1223444555666789999

10101011111111

440214103072601440144103075301440144103075301440204103064101440150103064001440150103064001440150103064001440147103064901440147103064901440147103064901440141103064001440141103064001440141103064001440131103070401441400103235801441401103235101441401103235101441401103235101441401103235101441353103232001441353103232001441353103232001441352103232601441352103232601441352103232601441352103232601

09/13/0609/14/0607/26/0709/18/0609/21/0609/21/0607/26/0710/10/0606/26/0707/26/0709/21/0606/26/0707/26/0705/17/0708/29/0709/27/0607/02/0708/29/0710/24/0705/15/0708/28/0710/29/0710/19/0605/15/0708/28/0710/29/07

GV1GV6GV6GV7GV3GV3GV3GV2GV2GV2GV4GV4GV4GV5MS-WMS-EMS-EMS-EMS-EPM3PM3PM3PM1PM1PM1PM1

PP

B

PPPPPP

B

PP

BBB

PPPP

B

PP

BBB

P

0.5

.5----.3.3--.8.7--.3.7----------

8.21.0

.3--.7--.2--.2

1,3901,1501,1203,1201,8401,8202,9104,9806,0605,7204,5104,1904,0701,3002,210

835878738867

1,1201,6701,280

982

1,7601,1201,240

----

1,140

------

2,940

--

6,1105,850

--

4,2004,150

--

2,230

--

901757873

--

1,7101,280

----

1,1601,240

7.16.97.06.96.76.77.06.76.66.86.76.76.97.06.97.06.46.76.66.96.66.66.47.06.86.5

----

7.3

------

7.0

--

6.96.9

--

7.07.0

--

7.1

--

7.17.17.1

--

7.07.1

----

7.27.1

27.829.429.018.015.015.428.0

8.0

21.028.015.223.028.021.024.014.038.026.027.021.017.025.012.019.017.025.0

17.914.011.515.915.115.113.012.310.012.015.311.314.411.513.811.311.110.810.711.110.911.712.611.411.611.2

678

--

685

------

685

--

690685

--

690685675678

--

673678678678674674

--

678679675

2.84.88.55.53.44.75.53.3

10.6

7.23.8

15.6

6.54.1

17.5

9.18.78.8

10.711.210.010.5

2.1

11.8

--

10.7
Table 24. Measurements of physical properties in ground water.––Continued [Shading denotes background sites. Collection method: P, pumped; B, bailed, T, tap near production well or spring. gal/min, gallons per minute; μS/cm, microsiemens per centimmm of Hg, millimeters of mercury; mg/L, milligrams per liter; --, no data] Site number Station identification number Date Other iden- tifier Col- lection meth- od Flow rate (gal/ min) (00059) Specific conduct- ance, water whole, field (μS/cm) (00095) Specific conduct- ance, water whole, laboratory (μS/cm) (90095) pH, water whole, field (standard units) (00400) pH, water whole, laboratory (standard units) (00403) Air temperature (deg C) (00020) Water temperature (deg C) (00010) Barometric pressure (mm of Hg) (00025) Dissolv

oxyge

(mg/L

(00300

1212121213131314141415151616171717171717181818 441349103232301 441349103232301 441349103232301 441349103232301 441303103220601 441303103220601 441303103220601 441302103220602 441302103220602 441302103220602 441302103220501 441302103220501 441222103221201 441222103221201 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 440709103174101 440709103174101 440709103174101 10/12/06 04/03/07 08/28/07 10/24/07 05/16/07 08/28/07 11/19/07 10/19/06 08/29/07 11/19/07 10/16/06 11/19/07 10/19/06 11/05/07 09/28/06 04/03/07 06/27/07 09/06/07 11/07/07 01/10/08 10/12/06 06/20/07 11/03/07 PM2 PM2 PM2 PM2 SS1 SS1 SS1 SS2 SS2 SS2 SS4 SS4 SCSCSES SES SES SES SES SES QRY QRY QRY PPPPBBBBBPPPBBPPPPPPBBB 0.5.1-- 1.0--------.4.8 1.1------.2.2.8.5.5-------- 717 741 772 770 1,170 1,140 1,100 1,220 1,160 1,330 815 850 520 520 1,430 1,480 1,470 1,510 1,590 1,600 778 959 1,000 -- 745 795 765-- 1,170 1,100-- 1,190 1,320-- 849-- 518-- 1,480 1,520 1,560 1,600 1,600-- 979 1,010 7.1 7.0 6.7 6.5 7.1 7.0 6.9 6.8 7.2 6.6 7.1 6.9 6.4 7.3 6.8 6.9 6.8 6.7 6.6 6.8 6.4 7.2 6.8 -- 7.3 7.3 7.3-- 7.3 7.4-- 7.3 7.4-- 7.6-- 7.6-- 7.2 7.2 7.5 7.2 7.1-- 7.3 7.4 10.0 5.5 17.0 26.0 2.0 17.0 13.0 14.0 26.0 14.0 15.0 16.0 9.0 5.0 14.0 6.5 28.0 22.0 22.0 9.5 8.0 28.0 7.0 10.6 10.6 10.4 10.8 11.1 11.1 10.0 9.8 11.8 10.7 11.1 11.0 9.6 9.2 11.7 10.5 11.8 12.7 11.2 9.9 10.2 11.8 9.8 -- 677 679 678 677 679 666-- 678 665-- 666-- 678-- 675 678 665 669 661-- 673 676 3.6 6.6 10.2 11.5 7.9 15.2 16.7 1.6 14.1 10.6 2.4 14.5 3.7 11.2 7.9 6.7 9.2 7.8 7.5 10.3 5.4 10.9 12.3 
Table 24. Measurements of physical properties in ground water.––Continued[Shading denotes background sites. Collection method: P, pumped; B, bailed, T, tap near production well or spring. gal/min, gallons per minute; μS/cm, microsiemens per centimmm of Hg, millimeters of mercury; mg/L, milligrams per liter; --, no data]

Site

number

Station

identification

number

Date

Other

identifier

Collection 

method

Flow 

rate

(gal/

min)

(00059)

Specific

conductance, water 

whole, field

(μS/cm)

(00095)

Specific 

conductance,

water 

whole,

laboratory

(μS/cm)

(90095)

pH,

water 

whole,

field

(standard 

units)

(00400)

pH,

water 

whole, 

laboratory 

(standard 

units)

(00403)

Air 

temperature

(deg C) 

(00020)

Water 

temperature

(deg C) 

(00010)

Barometric

pressure

(mm of Hg)

(00025)

Dissolv

oxyge

(mg/L

(00300

191919202021212121212122222222222223232324252626

440644103182901440644103182901440644103182901440642103182901440642103182901440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440446103175701440446103175701440446103175701440446103175701440446103175701440446103175701440143103163001440143103163001440143103163001435823103160901435938103220501440510103261701440510103261701

10/18/0605/16/0706/18/0705/16/0706/14/0709/12/0604/03/0706/27/0709/06/0711/07/0701/10/0810/05/0605/22/0706/18/0709/19/0709/24/0701/10/0810/05/0606/28/0710/03/0705/22/0705/14/0705/01/0707/02/07

HV-NHV-N

HV-NHV-SHV-SBP-NBP-NBP-NBP-NBP-NBP-NBP-SBP-SBP-SBP-SBP-SBP-SWW-NWW-NWW-NNYVG----

BBBBB

PPPPPP

BBBBBBBBBBB

TT

----------

0.1

.3.3.3--.2--------------------.1

9.0

12.0

513935

9,0501,4201,7201,6501,5001,5601,2802,1102,3003,2902,1102,6002,5802,8005,7601,4502,3102,900

662335874881

----

9,210

--

1,840

--

1,4401,6201,3402,1602,320

----

2,6502,560

--

5,900

--

2,3903,060

------

892

6.37.06.96.76.66.86.76.76.56.76.56.36.86.95.66.76.86.86.86.76.96.16.96.6

----

6.8

--

7.1

--

7.27.07.57.07.1

----

7.07.0

--

6.9

--

7.37.1

------

6.9

6.0

21.228.020.028.026.7

4.5

22.021.021.0

8.0

22.0

--

27.024.016.0

2.0

21.029.030.0

--

20.020.234.0

9.9

12.912.612.912.212.9

9.6

11.911.711.610.211.811.412.612.111.5

8.7

12.511.313.011.918.9

7.87.6

--

675675675667

--

677679668672665

--

663675676673664

--

676668660677

--

655

--

8.3

10.710.211.2

7.56.89.89.18.69.69.6

10.310.411.815.510.4

8.7

11.414.510.8

8.08.47.4
Table 24. Measurements of physical properties in ground water.––Continued [Shading denotes background sites. Collection method: P, pumped; B, bailed, T, tap near production well or spring. gal/min, gallons per minute; μS/cm, microsiemens per centimmm of Hg, millimeters of mercury; mg/L, milligrams per liter; --, no data] Site number Station identification number Date Other iden- tifier Col- lection method Flow rate (gal/ min) (00059) Specific conduct- ance, water whole, field (μS/cm) (00095) Specific conduct- ance, water whole, laboratory (μS/cm) (90095) pH, water whole, field (standard units) (00400) pH, water whole, laboratory (standard units) (00403) Air tem- perature (deg C) (00020) Water tem- perature (deg C) (00010) Barometric pressure (mm of Hg) (00025) Dissolve

oxygen (mg/L) (00300) 

27272829303132333435363639404142434444444546474848 440504103262201 440504103262201 440459103265001 440454103262301 440452103262201 440452103255101 440447103254901 440442103260201 440416103253401 440324103250501 440318103233901 440318103233901 440245103301501 440218103302101 440205103300501 440505103335401 440505103335402 440505103335001 440505103335001 440505103335001 440505103334801 440504103335701 440503103335501 440502103334701 440502103334701 05/17/07 -- 07/16/07 -- 06/20/07 -- 07/02/07 -- 07/02/07 -- 04/26/07 -- 06/21/07 -- 06/21/07 -- 06/25/07 -- 06/19/07 -- 06/20/07 -- 07/25/07 -- 05/02/07 -- 06/19/07 -- 05/02/07 -- 06/11/07 -- 06/14/07 -- 06/11/07 -- 07/16/07 -- 07/25/07 -- 06/12/07 -- 06/11/07 -- 06/12/07 -- 06/19/07 -- 07/25/07 -- TTTTTTTTTTTTTTTTTTTTTTTTT 10.0 8.0 30.0 10.0-------- 20.0-- 12.0---- 6.0-- 6.0 2.0 6.0 10.0-- 15.0 8.0 6.0---- 519 503 560 456 483 634 563 626 534 698 858 878 650 351 596 764 692 859 867 877 551 408 590 1,040 1,040 -- 520-- 460-------------- 888 644-- 590------ 887 882-------- 1,060 6.8 6.6 6.6 6.4 7.0 6.6 6.8 6.9 6.9 6.6 7.0 6.7 7.2 6.7 6.9 6.2 6.3 6.4 6.5 6.8 6.5 6.6 6.6 6.5 6.8 -- 7.1-- 7.3-------------- 7.2 7.5-- 7.3------ 6.6 7.0-------- 7.1 19.0 31.0 30.0 29.0 30.0 20.0 26.0 27.0 32.0 25.0 29.0 33.0 20.5 27.0 21.0-- 26.0-- 32.0 33.0------ 27.0 31.0 7.5 9.8 7.6 8.1 9.9 9.7 9.3 9.6 7.8 9.1 8.6 9.8 10.6 9.6 9.0 10.1 9.5 8.7 8.6 8.5 8.0 8.3 8.2 8.1 7.7 677 654 653 655 654 -- 653 655 651 658 665 650 632 678 635 -- 642 -- 644 643 643 639 -- 646 643 3.6 8.0 10.4 7.5 8.1 10.5 9.1 8.9 8.5 8.0 8.3 12.4 7.1 4.9 3.8 7.8 7.0-- 8.2 4.0 5.5 4.0-- 8.0 6.0 
Table 24. Measurements of physical properties in ground water––Continued.[Shading denotes background sites. Collection method: P, pumped; B, bailed, T, tap near production well or spring. gal/min, gallons per minute; μS/cm, microsiemens per centimmm of Hg, millimeters of mercury; mg/L, milligrams per liter; --, no data]

Site

number

Station

identification

number

Date

Other

identifier

Collection 

method

Flow 

rate

(gal/

min)

(00059)

Specific

conductance, water 

whole, field

(μS/cm)

(00095)

Specific 

conductance,

water 

whole,

laboratory

(μS/cm)

(90095)

pH,

water 

whole,

field

(standard 

units)

(00400)

pH,

water 

whole, 

laboratory 

(standard 

units)

(00403)

Air temperature

(deg C) 

(00020)

Water temperature

(deg C) 

(00010)

Barometric

pressure

(mm of Hg)

(00025)

Dissolved 

oxygen

(mg/L)

(00300)

4950515253545556575859606162

440501103335201440501103335101440459103334801440458103334802440458103334801440457103334101435753103320401435707103320101435703103314101435654103312101435645103310601435637103321201435630103311901435619103331101

06/13/07 --06/13/07 --

06/12/07 --06/12/07 --06/13/07 --06/11/07 --07/10/07 --07/10/07 --07/09/07 --07/10/07 --07/09/07 --07/09/07 --07/10/07 --07/09/07 --

TTTTTTTTTTTTTT

6.08.07.0

10.0

--

8.0

10.0

--

8.0

--

6.0

15.0

--

4.0

803872760780491486273231275343740554305316

----------------------

558

----

6.66.46.76.76.36.26.25.95.26.35.56.6

--

6.2

----------------------

7.3

----

22.022.022.0

--

22.0

--

26.025.031.027.030.031.028.030.0

8.38.17.78.37.98.2

10.210.0

9.69.89.69.08.79.1

645645645641645639642641636647640630

--

637

9.27.05.25.45.26.48.0

13.7

9.25.7

10.1

7.05.75.4
Table 25. Measurements of physical properties in surface water. [Shading denotes background sites. ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter; deg C, degrees Celsius; mm of Hg, millimeters of mercury; mg/L, milligr

no data] Specific pH, pH, 

Specific conduct- 

Discharge, water water 

conduct- ance, Air Water Barometric Dissolved 

Station instan- whole, whole, 

Site Other ance, water water temperature temperature pressure oxygen 

identification Date taneous field laboratory, 

number identifier whole, field whole, (deg C) (deg C) (mm of Hg) (mg/L) 

number (ft3/s) (standard (standard 

(μS/cm) laboratory (00020) (00010) (00025) (00300) 

(00059) units) units) 

(00095) (μS/cm) 

(00400) (00403) 

(90095) 37 06411900 07/24/07 RC1 104 421 407 8.3 8.2 30.5 8.2 653 12.1 

37 06411900 10/17/07 RC1 20 414 405 7.6 8.3 7 16.5 637 9.3 38 06412000 07/24/07 RC3 96 427 409 8.5 8.5 38 11.8 656 11.0 38 06412000 10/17/07 RC3 16 423 415 8.0 8.4 16.5 8.3 641 13.3 63 435720103273401 05/10/06 CALUMET2 E.02 330 -- 7.0 -- 6.5 6.6 -- 11.9 63 435720103273401 09/26/06 CALUMET2 E.05 351 -- 5.5 -- -- 8.3 -- 6.8 

63 435720103273401 05/09/07 CALUMET2 -- 362 -- -- -- 28.8 8.8 -- -- 64 06406960 05/10/06 CALUMET1 .08 460 -- 7.0 -- 5 6.5 -- 10.9 

64 06406960 09/26/06 CALUMET1 E.05 499 -- 6.0 -- 22 10.5 -- 5.0 64 06406960 05/09/07 CALUMET1 -- 600 -- -- -- 28.8 10.5 -- -- 65 06406760 05/31/06 RENO2 E.10 441 -- 7.7 -- 68 9.7 636 10.2 

65 06406760 09/26/06 RENO2 E.05 367 -- 7.4 -- 24 9.1 -- 8.9 65 06406760 05/09/07 RENO2 -- 487 -- -- -- 31.6 9.5 -- -- 

66 435436103352201 05/31/06 RENO1 E.20 531 -- 7.4 -- 22.2 10.9 643 9.2 

66 435436103352201 09/26/06 RENO1 E.05 414 -- 6.4 -- 23 8.4 -- 9.4 66 435436103352201 05/09/07 RENO1 -- 621 608 -- -- -- 10.0 -- -- 

67 06406700 07/23/07 SPCR1 .42 423 410 8.0 8.2 33.5 19.0 632 10.5 67 06406700 09/05/07 SPCR1 .38 431 441 7.7 8.2 19 15.7 623 9.1 68 435628103324600 07/23/07 SPRC2 1.7 498 477 8.4 8.4 38 23.3 642 10.2 68 435628103324600 09/05/07 SPRC2 .68 612 625 8.2 8.3 24 19.5 634 10.5 69 06406920 07/23/07 SPCR3 1.10 416 434 8.5 8.4 36 24.5 646 10 69 06406920 09/05/07 SPCR3 .49 512 523 7.8 8.1 26.5 22.6 640 6.6 
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.[Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than]

Site 

number

Station

identification

number

Date

Calcium, 

dissolved

(mg/L as 

Ca) (00915)

Magnesium, 

dissolved

(mg/L as Mg) 

(00925)

Sodium, 

dissolved

(mg/L as Na)

(00930)

Potassium, 

dissolved

(mg/L as K)

(00935)

Sulfate,

dissolved

(mg/L as SO ) 4

(00945)

Chloride, 

dissolved 

(mg/L as Cl)

(00940)

Fluoride, 

dissolved

(mg/L as F)

(00950)

Bromide, 

dissolved 

(mg/L as Br)

(71870

Chloride/

bromide 

ratio

1223444555666789999

10101011111111

440214103072601440144103075301440144103075301440204103064101440150103064001440150103064001440150103064001440147103064901440147103064901440147103064901440141103064001440141103064001440141103064001440131103070401441400103235801441401103235101441401103235101441401103235101441401103235101441353103232001441353103232001441353103232001441352103232601441352103232601441352103232601441352103232601

09/13/0609/14/0607/26/0709/18/0609/21/0609/21/0607/26/0710/10/0606/26/0707/26/0709/21/0606/26/0707/26/0705/17/0708/29/0709/27/0607/02/0708/29/0710/24/0705/15/0708/28/0710/29/0710/19/0605/15/0708/28/0710/29/07

----

111

------

273

--

500472

--

346348

--

231

--

143130143

--

203155

----

149155

----

65.8

------

154

--

274265

--

250254

--

103

--

25.220.224.5

--

74.558.0

----

48.151.8

----

34.6

------

202

--

629617

--

341349

--

14.9

--

11.4

4.328.81

--

11.6

9.21

----

15.616.5

----

3.85

------

7.76

--

10.210.6

--

7.848.94

--

5.29

--

2.231.732.08

--

2.312.16

----

2.362.42

----

280

------

1,010

--

2,1202,080

--

1,7301,700

--

25.9

--

93.328.040.9

--

57.256.6

----

85.583.6

22.830.341.7

174

54.254.1

205426824723385339324

55.5

520

19.421.4

8.16

18.3

135304172144273103132

----

0.57

------.73--.50.50--.63.62--.57--.18.14.16--.17.21----.19.21

0.09

.06.07.17.11.11.20.32.03.29.34.06.31.10

2.43

.07.03

E.01

.04.70

1.50

.77.64

1.25

.38.55

253505596

1,020

493492

1,0201,330

27,470

2,4901,1305,6501,050

555214277713816458193203223225218271240
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued [Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than] Site number Station identification number Date Calcium, dissolved (mg/L as Ca) (00915) Magnesium, dissolved (mg/L as Mg) (00925) Sodium, dissolved (mg/L as Na) (00930) Potassium, dissolved (mg/L as K) (00935) Sulfate, dissolved (mg/L as SO ) 4 (00945) Chloride, dissolved (mg/L as Cl) (00940) Fluoride, dissolved (mg/L as F) (00950) Bromide, dissolved (mg/L as Br) (71870 Chloride/ bromide ratio 

1212121213131314141415151616171717171717181818 441349103232301 441349103232301 441349103232301 441349103232301 441303103220601 441303103220601 441303103220601 441302103220602 441302103220602 441302103220602 441302103220501 441302103220501 441222103221201 441222103221201 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 440709103174101 440709103174101 440709103174101 10/12/06 04/03/07 08/28/07 10/24/07 05/16/07 08/28/07 11/19/07 10/19/06 08/29/07 11/19/07 10/16/06 11/19/07 10/19/06 11/05/07 09/28/06 04/03/07 06/27/07 09/06/07 11/07/07 01/10/08 10/12/06 06/20/07 11/03/07 -- 102 108 106-- 164 153-- 149 154-- 12452.4-- 210 217 226 257 252-- 116 117 -- 32.2 33.9 34.0-- 49.0 48.4-- 55.7 78.2-- 38.6 39.3-- 45.8 44.0 44.7 45.3 45.8-- 23.2 24.2 -- 5.38 6.25 6.28 -- 19.7 25.7-- 28.0 33.1-- 7.30 1.70 -- 23.9 29.1 30.5 32.9 32.3-- 41.0 40.1 --- 1.69 1.73 1.74 -- 2.76 2.37 -- 3.79 2.12 -- 1.57 1.29 -- 3.27 3.12 2.97 2.98 3.00 -- 10.5 19.4 -- 50.6 54.9 57.0-- 137 142-- 11844.7-- 1753.90 -- 245 267 328 402 394-- 108 121 14.3 20.1 20.1 21.7 26.8 32.4 23.7 35.0 28.3 37.3 11.3 17.2 3.17 1.19 167 175 164 151 133 14169.9 110 115 -- 0.22 .20 .21 --.24 .26 --.25 .30 --.31 --.19 --.41 .46 .38 .41 .41 --.52 .62 0.03 .03 .03 .04 .05 .07 .05 .06 .15 .03 .03 E.02 E.02 E.01 .07 .07 .04 .05 .05 .04 1.02 .32 .59 477 670 670 543 536 463 474 583 189 1,240 377 860 159 119 2,390 2,500 4,100 3,020 2,660 3,52069 344 195 
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued [Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than]

Site 

number

Station

identification

number

Date

Calcium, 

dissolved

(mg/L as 

Ca) (00915)

Magnesium, 

dissolved

(mg/L as Mg) 

(00925)

Sodium, dissolved(mg/L as Na)

(00930)

Potassium, 

dissolved

(mg/L as K)

(00935)

Sulfate,

dissolved

(mg/L as SO ) 4

(00945)

Chloride, 

dissolved 

(mg/L as Cl)

(00940)

Fluoride, 

dissolved

(mg/L as F)

(00950)

Bromide, 

dissolved 

(mg/L as Br)

(71870

Chloride

bromide 

ratio

1919192020212121212121222222222223232324252626

440644103182901440644103182901440644103182901440642103182901440642103182901440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440446103175701440446103175701440446103175701440446103175701440446103175701440143103163001440143103163001440143103163001435823103160901435938103220501440510103261701440510103261701

10/18/0605/16/0706/18/0705/16/0706/14/0709/12/0604/03/0706/27/0709/06/0711/07/0701/10/0810/05/0605/22/0706/18/0709/19/0701/10/0810/05/0606/28/0710/03/0705/22/0705/14/0705/01/0707/02/07

----

527

--

240

--

204238206299307

----

213227386

--

210232

------

118

----

94.7

--

31.9

--

32.037.125.945.548.1

----

49.052.186.0

--

80.082.0

------

26.7

----

1,160

--

70.2

--

56.365.246.496.9

128

----

257239666

--

166226

------

22.4

----

14.9

--

4.23

--

3.003.222.563.643.40

----

7.267.18

10.9

--

11.4

9.18

------

1.88

----

79.2

--

25.8

--

219286214369362

----

181169266

--

35.835.0

------

36.7

1,5703,0802,850

211316150138155105270344740353516553

1,510

312593858

26.226.278.287.2

----

0.59

--.31--.33.33.25.34.28----.47.44.44--.68.58------.30

3.721.05

.86.06.09.05.04.04.03.05.05.23.07.06.06.05

2.32

.56.44.09.04.12.16

422

2,9303,3103,5203,5103,0003,4503,8803,5005,4006,8803,2205,0408,6009,220

30,200

134

1,0601,950

291655652545
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued [Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than] Site number Station identification number Date Calcium, dissolved (mg/L as Ca) (00915) Magnesium, dissolved (mg/L as Mg) (00925) Sodium, dissolved (mg/L as Na) (00930) Potassium, dissolved (mg/L as K) (00935) Sulfate, dissolved (mg/L as SO ) 4 (00945) Chloride, dissolved (mg/L as Cl) (00940) Fluoride, dissolved (mg/L as F) (00950) Bromide, dissolved (mg/L as Br) (71870 Chloride

bromide ratio 

27272829303132333435363639404142434444444546474848 440504103262201 440504103262201 440459103265001 440454103262301 440452103262201 440452103255101 440447103254901 440442103260201 440416103253401 440324103250501 440318103233901 440318103233901 440245103301501 440218103302101 440205103300501 440505103335401 440505103335402 440505103335001 440505103335001 440505103335001 440505103334801 440504103335701 440503103335501 440502103334701 440502103334701 05/17/07 07/16/07 06/20/07 07/02/07 07/02/07 04/26/07 06/21/07 06/21/07 06/25/07 06/19/07 06/20/07 07/25/07 05/02/07 06/19/07 05/02/07 06/11/07 06/14/07 06/11/07 07/16/07 07/25/07 06/12/07 06/11/07 06/12/07 06/19/07 07/25/07 -- 66.8 -- 54.9 -------------- 79.2 68.3 -- 61.9 ------ 96.8 89.2 -------- 99.7 -- 23.0 -- 21.8 -------------- 52.7 28.9 -- 24.4 ------ 47.0 43.7 -------- 53.1 -- 4.76 -- 4.81 -------------- 17.8 19.3-- 14.3------ 20.1 19.7-------- 35.7 -- 1.98 -- 2.29 -------------- 2.74 4.34 -- 3.00 ------ 2.16 2.02 -------- 2.05 -- 52.3-- 49.0-------------- 28.3 80.5-- 63.3------ 79.4 75.5-------- 88.2 8.23 6.63 48.4 7.13 17.9 49.6 39.1 48.1 25.1 49.5 59.9 58.8 41.6 9.31 51.3 42.7 35.4 63.8 65.6 64.2 8.55 2.25 13.6 55.7 56.1 -- 0.27 -- .27-------------- .41 .34-- .35------ .40 .39-------- .52 0.06 .04 .04 .02 .03 .04 .04 .05 .02 .04 .06 .06 .10 .04 .05 .06 .06 .07 .08 .08 .03 .03 .04 .06 .06 137 166 1,210 357 597 1,240 978 962 1,260 1,240 998 980 416 233 1,030 712 590 911 820 803 28575 340 928 935 
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued[Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than]

Site 

number

Station

identification

number

Date

Calcium, 

dissolved

(mg/L as Ca) 

(00915)

Magnesium, 

dissolved

(mg/L as Mg) 

(00925)

Sodium, dissolved(mg/L as Na)

(00930)

Potassium, 

dissolved

(mg/L as K)

(00935)

Sulfate,

dissolved

(mg/L as SO ) 4

(00945)

Chloride, 

dissolved 

(mg/L as Cl)

(00940)

Fluoride, 

dissolved

(mg/L as F)

(00950)

Bromide, 

dissolved 

(mg/L as Br)

(71870

Chloride

bromide 

ratio

4950515253545556575859606162

440501103335201440501103335101440459103334801440458103334802440458103334801440457103334101435753103320401435707103320101435703103314101435654103312101435645103310601435637103321201435630103311901435619103331101

06/13/0706/13/0706/12/0706/12/0706/13/0706/11/0707/10/0707/10/0707/09/0707/10/0707/09/0707/09/0707/10/0707/09/07

----------------------

59.7

----

----------------------

21.5

----

----------------------

16.7

----

----------------------

5.28

----

----------------------

53.3

----

16.419.8

5.94

13.5

1.493.181.751.371.55

11.056.226.8

5.81

16.3

----------------------

0.97

----

0.05

.06.05.04.03.03.03.03.03.04.15.08.05.05

328330119338

50

106

584652

275375335116326
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued [Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than] Site number Station identification number Date Nitrogen, nitrite, dis- solved (mg/L as N) (00613) Nitrogen, NO +NO , 2 3 dissolved (mg/L as N) (00631) Nitrogen, ammonia, dissolved (mg/L as N) (00608) Phosphorous, dissolved (mg/L as P) (00666) Ortho- phosphate, dissolved (mg/L as P) (00671) Boron, dissolved (μg/L as B) (01020) Iron, dissolved (μg/L as Fe) (01046) Man

diss

(μg/L 

(0

122344455566678999910101011111111 440214103072601 440144103075301 440144103075301 440204103064101 440150103064001 440150103064001 440150103064001 440147103064901 440147103064901 440147103064901 440141103064001 440141103064001 440141103064001 440131103070401 441400103235801 441401103235101 441401103235101 441401103235101 441401103235101 441353103232001 441353103232001 441353103232001 441352103232601 441352103232601 441352103232601 441352103232601 09/13/06 09/14/06 07/26/07 09/18/06 09/21/06 09/21/06 07/26/07 10/10/06 06/26/07 07/26/07 09/21/06 06/26/07 07/26/07 05/17/07 08/29/07 09/27/06 07/02/07 08/29/07 10/24/07 05/15/07 08/28/07 10/29/07 10/19/06 05/15/07 08/28/07 10/29/07 ---- <0.002 ------.010 --.013 .020 --.003 .002 -- <.002 -- <.002 <.002 <.002 -- <.002 <.002 ---- <.002 <.002 0.148 .175 .180 .047 <.016 <.016 2.61 1.64 1.56 1.64 <.016 <.016 E.015 .532 3.22 3.45 2.66 1.95 2.80 2.46 4.34 5.63 .100 6.92 6.71 11.0 0.024 E.007 <.020 .026 .025 .022 <.020 <.080 <.060 <.060 .525 .422 .411 E.019 <.020 <.010 <.020 <.020 <.020 E.014 <.020 <.020 .156 <.020 <.020 <.020 ---- E0.006 ------.007 --.007 E.005 --.042 .009 --.007 --.028 .029 .039 -- E.004 .007 ----.059 .060 ---- 0.008 ------.009 --.012 .010 --.043 .010 -- E.004 --.029 .034 .041 --.011 .008 ----.054 .058 716 160 130 819 593 576 559 882 866 812 1,060 898 904 1213725181617222625 132635282 ----<6 ------ <18 -- <30 <18 -- 12,400 6,270 -- <18 --E5<6E4 --<6E4 ----<6E5 

1,1,1,
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued[Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than]

Site 

number

Station

identification

number

Date

Nitrogen, 

nitrite, 

dissolved

(mg/L as N) 

(00613)

Nitrogen, 

NO +NO3, 2

dissolved

 (mg/L as N)

(00631)

Nitrogen,

ammonia, 

dissolved

(mg/L as N)

(00608)

Phosphorous, 

dissolved

(mg/L as P) 

(00666)

Orthophosphate, 

dissolved

(mg/L as P) 

(00671)

Boron,

dissolved

(μg/L as B)

(01020)

Iron,

dissolved

(μg/L as Fe) 

(01046)

Man

diss

(μg/L 

(0

1212121213131314141415151616171717171717181818

441349103232301441349103232301441349103232301441349103232301441303103220601441303103220601441303103220601441302103220602441302103220602441302103220602441302103220501441302103220501441222103221201441222103221201441215103213301441215103213301441215103213301441215103213301441215103213301441215103213301440709103174101440709103174101440709103174101

10/12/0604/03/0708/28/0710/24/0705/16/0708/28/0711/19/0710/19/0608/29/0711/19/0710/16/0611/19/0710/19/0611/05/0709/28/0604/03/0706/27/0709/06/0711/07/0701/10/0810/12/0606/20/0711/03/07

--

<0.002

E.002

<.002

--

<.002

E.002

--

<.002<.002

--

<.002

--

<.002

--.003.004.003.004.005--

<.002

E.001

4.136.775.265.33

12.512.712.711.611.214.9

.967

1.39

.286.215

9.799.778.898.217.497.424.644.415.21

<.040<.020<.020<.020

E.012

<.020

.028

<.040<.020<.020<.040<.020

.044

<.020

E.009

<.020<.020<.020<.020<.020<.040<.020<.020

--

0.010

.008.009--.009.007--.077.009--

E.004

--.006--.008.009.049.154.009--.026.052

--

0.010

.013.010--.014.008--.018.014--.008--.007--.009.010.012.011.012--.008

E.006

201823225556647761

101

22211514454346424345273435

--

13

8

E6

--

<6<8

--

<6

E6

--

<8

--

<8

--

13

87

E4E5

--

<6<8

0

E

2

28

<

454222
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued [Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than] Site number Station identification number Date Nitrogen, nitrite, dissolved (mg/L as N) (00613) Nitrogen, NO +NO3, 2 dissolved (mg/L as N) (00631) Nitrogen, ammonia, dissolved (mg/L as N) (00608) Phosphorous, dissolved (mg/L as P) (00666) Ortho- phosphate, dissolved (mg/L as P) (00671) Boron, dissolved (μg/L as B) (01020) Iron, dissolved (μg/L as Fe) (01046) Man

diss

(μg/L 

(0

1919192020212121212121222222222223232324252626 440644103182901 440644103182901 440644103182901 440642103182901 440642103182901 440451103180201 440451103180201 440451103180201 440451103180201 440451103180201 440451103180201 440446103175701 440446103175701 440446103175701 440446103175701 440446103175701 440143103163001 440143103163001 440143103163001 435823103160901 435938103220501 440510103261701 440510103261701 10/18/06 05/16/07 06/18/07 05/16/07 06/14/07 09/12/06 04/03/07 06/27/07 09/06/07 11/07/07 01/10/08 10/05/06 05/22/07 06/18/07 09/19/07 01/10/08 10/05/06 06/28/07 10/03/07 05/22/07 05/14/07 05/01/07 07/02/07 ---- 0.003 -- E.002 --.006 <.002 <.002 <.002 <.002 ---- E.001 <.002 .004 --.004 .006 ------ <.002 9.35 16.4 12.7 14.0 20.8 5.87 5.48 6.57 4.25 8.23 9.41 17.6 9.96 12.3 11.0 24.3 4.04 5.49 6.87 1.76 1.67 4.93 5.06 <0.040 .047 <.020 <.020 <.020 .018 <.020 <.020 <.020 <.020 <.020 E.025 <.020 <.020 <.020 <.020 .062 E.015 <.020 <.020 <.020 <.020 <.020 ---- 0.125 --.007 --.023 .033 .031 .019 .018 ----.140 .148 .260 --.118 .111 ------.017 ---- 0.009 --.012 --.015 .036 .049 .024 .018 ----.143 .146 .284 --.012 .016 ------.021 586766 180 158393241353838 155 106 152 121 22140424126254350 ---- E17 --<6 --112611 E22 E16 ---- E15 <18 <24 -- <18 <24 ------E5 

5444335
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued[Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than]

Site 

number

Station

identification

 number

Date

Nitrogen, 

nitrite, 

dissolved

(mg/L as N) 

(00613)

Nitrogen, 

NO +NO3, 2

dissolved

 (mg/L as N)

(00631)

Nitrogen,

ammonia, 

dissolved

(mg/L as N)

(00608)

Phosphorous, 

dissolved

(mg/L as P) 

(00666)

Orthophosphate, 

dissolved

(mg/L as P) 

(00671)

Boron,

dissolved

(μg/L as B)

(01020)

Iron,

dissolved

(μg/L as Fe) 

(01046)

Man

diss

(μg/L 

(0

27272829303132333435363639404142434444444546474848

440504103262201440504103262201440459103265001440454103262301440452103262201440452103255101440447103254901440442103260201440416103253401440324103250501440318103233901440318103233901440245103301501440218103302101440205103300501440505103335401440505103335402440505103335001440505103335001440505103335001440505103334801440504103335701440503103335501440502103334701440502103334701

05/17/0707/16/0706/20/0707/02/0707/02/0704/26/0706/21/0706/21/0706/25/0706/19/0706/20/0707/25/0705/02/0706/19/0705/02/0706/11/0706/14/0706/11/0707/16/0707/25/0706/12/0706/11/0706/12/0706/19/0707/25/07

--

<0.002

--

<.002

--------------

<.002

.003--

<.002

--------.021.029------

E.001

8.533.591.27

.865.468

3.522.332.851.133.118.117.941.34

<.016<.016

.234

1.016.226.667.12

<.016

.225

1.112.593.58

<0.020

<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020<.020

E.012

<.020

.021

<.020

E.010

--

<0.006

--

<.006

--------------.007

E.005

--

<.006

--------.007.008------.017

--

0.006

--.038--------------.009.007--

<.006

--------.014.013------.020

1917212146382430222735374413143133393636292544

108104

--

26

--

<6

--------------

<6<6

--

898

--------

E5E6

------

34

4532

1,1
Table 26. Concentrations of major ions, nutrients, and selected trace elements in ground water.––Continued [Shading denotes background sites. mg/L, milligrams per liter; --, no data; E, estimated; μg/L, micrograms per liter; <, less than] Site number Station identification number Date Nitrogen, nitrite, dissolved (mg/L as N) (00613) Nitrogen, NO +NO3, 2 dissolved (mg/L as N) (00631) Nitrogen, ammonia, dissolved (mg/L as N) (00608) Phosphorous, dissolved (mg/L as P) (00666) Ortho- phosphate, dissolved (mg/L as P) (00671) Boron, dissolved (μg/L as B) (01020) Iron, dissolved (μg/L as Fe) (01046) Ma

di

(μg/

(

4950515253545556575859606162 440501103335201 440501103335101 440459103334801 440458103334802 440458103334801 440457103334101 435753103320401 435707103320101 435703103314101 435654103312101 435645103310601 435637103321201 435630103311901 435619103331101 06/13/07 06/13/07 06/12/07 06/12/07 06/13/07 06/11/07 07/10/07 07/10/07 07/09/07 07/10/07 07/09/07 07/09/07 07/10/07 07/09/07 ---------------------- <0.002 ---- <0.016 <.016 <.016 <.016 <.016 <.016 .246 E.009 <.016 .132 1.56 .08 .445 <.016 0.026 .047 .069 .157 .068 .065 <.020 <.020 <.020 <.020 <.020 <.020 <.020 E.010 ---------------------- E0.004 ---- ---------------------- 0.010 ---- 5151 180 21780911314181748181618 ---------------------- 26---- 
Table 27. Concentrations of major ions, nutrients, and selected trace elements in surface water.[Shading denotes upstream (background) sites. mg/L, milligrams per liter; E, estimated; <, less than --, no data; μg/L, micrograms per liter]

Site 

number

Station

identification

number

Date

Calcium, 

 dissolved

(mg/L as Ca) 

(00915)

Magnesium, 

dissolved

(mg/L as Mg) 

(00925)

Sodium, 

dissolved

(mg/L as Na)

(00930)

Potassium, 

dissolved

(mg/L as K)

(00935)

Sulfate,

dissolved

(mg/L as SO ) 4

(00945)

Chloride, 

dissolved 

(mg/L as Cl)

(00940)

Fluoride, 

dissolved

(mg/L as F)

(00950)

Bromide, 

dissolved 

(mg/L as Br)

(71870)

37373838636363646464656565666666676768686969

0641190006411900064120000641200043572010327340143572010327340143572010327340106406960064069600640696006406760064067600640676043543610335220143543610335220143543610335220106406700064067004356281033246004356281033246000640692006406920

07/24/0710/17/0707/24/0710/17/0705/10/0609/26/0605/09/0705/10/0609/26/0605/09/0705/31/0609/26/0605/09/0705/31/0609/26/0605/09/0707/23/0709/05/0707/23/0709/05/0707/23/0709/05/07

42.544.742.546.8

------------------------

44.848.346.357.540.648.8

23.423.223.423.6

------------------------

20.721.215.820.115.219.8

3.113.333.234.06

------------------------

4.746.84

21.736.017.723.2

2.612.722.532.82

------------------------

5.625.696.839.326.827.32

49.950.749.849.9

------------------------

31.428.624.421.922.023.4

2.412.502.834.751.671.531.556.647.708.68

36.323.147.758.329.073.4

4.76

14.039.964.537.552.1

0.26

.23.25.22------------------------.24.27.33.53.27.33

0.02

E.01E.02E.02E.02

.03--.04.07.05.05.09.07.05.06.06

E.02

.03.11.23.08.13
Table 27. Concentrations of major ions, nutrients, and selected trace elements in surface water.—Continued [Shading denotes upstream (background) sites. mg/L, milligrams per liter; E, estimated; <, less than --, no data; μg/L, micrograms per liter] Site number Station identification number Date Nitrogen, nitrite, dissolved (mg/L as N) (00613) Nitrogen, NO +NO3, 2 dissolved (mg/L as N) (00631) Nitrogen, ammonia, dissolved (mg/L as N) (00608) Phosphorous, dissolved (mg/L as P) (00666) Ortho- phosphate, dissolved (mg/L as P) (00671) Boron, dissolved (μg/L as B) (01020) Iron, dissolved (μg/L as Fe) (01046) Ma

di

(μg

(

37373838636363646464656565666666676768686969 06411900 06411900 06412000 06412000 435720103273401 435720103273401 435720103273401 06406960 06406960 06406960 06406760 06406760 06406760 435436103352201 435436103352201 435436103352201 06406700 06406700 435628103324600 435628103324600 06406920 06406920 07/24/07 10/17/07 07/24/07 10/17/07 05/10/06 09/26/06 05/09/07 05/10/06 09/26/06 05/09/07 05/31/06 09/26/06 05/09/07 05/31/06 09/26/06 05/09/07 07/23/07 09/05/07 07/23/07 09/05/07 07/23/07 09/05/07 <0.002 E.001 <.002 E.001 ------------ E.001 ---- E.001 ---- <.002 <.002 .059 .075 E.001 .002 E0.011 E.008 <.016 .035 .041 .844 .213 <.016 .025 <.016 .147 .211 .429 .067 .068 .277 <.016 <.016 .525 1.60 <.016 .029 <0.020 <.020 <.020 <.020 <.010 E.005 <.020 E.005 .046 <.020 E.009 <.010 <.020 E.006 <.010 E.012 E.010 <.020 .028 <.020 E.011 <.020 E0.005 E.004 E.004 E.003 E.003 ---- <.006 ----------------.013 .011 .018 .011 .011 .012 E0.004 E.004 <.006 E.003 E.003 ---- <.004 --------------.015 .011 .022 .012 .018 .017 10111013121514142119232322252326181740703441 E6<8E417------------------------ 14793 22691 17888 

34

13

523
Supplemental Information 85

Table 28. Nitrogen and oxygen isotope ratios for nitrate in ground water.

[Shading denotes background sites. mg/L, milligrams per liter; per mil, difference in parts per thousand from value reference standard; 

--, not applicable]

Site 

number

Station

identification

number

Date Other 

identifier

Nitrogen, NO +NO3, 2

dissolved (mg/L as N)

(00631)

δ15N in nitrate fraction,

water (per mil)

(82690)

δ18O in nitrate fraction,

water (per mil)

(63041)

4

5

5

8

9

9

9

10

10

11

11

12

12

12

13

13

14

14

15

16

17

17

17

17

17

18

18

19

20

21

21

21

21

21

22

22

22

23

23

26

27

29

30

36

44

44

48

60

440150103064001

440147103064901

440147103064901

441400103235801

441401103235101

441401103235101

441401103235101

441353103232001

441353103232001

441352103232601

441352103232601

441349103232301

441349103232301

441349103232301

441303103220601

441303103220601

441302103220602

441302103220602

441302103220501

441222103221201

441215103213301

441215103213301

441215103213301

441215103213301

441215103213301

440709103174101

440709103174101

440644103182901

440642103182901

440451103180201

440451103180201

440451103180201

440451103180201

440451103180201

440446103175701

440446103175701

440446103175701

440133103162101

440143103163001

440510103261701

440504103262201

440454103262301

440452103262201

440318103233901

440505103335001

440505103335001

440502103334701

435637103321201

07/26/07

06/26/07

07/26/07

08/29/07

07/02/07

08/29/07

10/24/07

08/28/07

10/24/07

08/28/07

10/29/07

04/03/07

08/28/07

10/24/07

08/28/07

11/19/07

08/29/07

11/19/07

11/19/07

11/05/07

04/03/07

06/27/07

09/06/07

11/07/07

01/10/08

06/20/07

11/05/07

06/18/07

06/14/07

04/03/07

06/27/07

09/06/07

11/07/07

01/10/08

06/18/07

09/19/07

01/10/08

06/28/07

10/03/07

07/02/07

07/16/07

07/02/07

07/02/07

07/25/07

07/16/07

07/25/07

07/25/07

07/09/07

GV3

GV2

GV2

MS-W

MS-E

MS-E

MS-E

PM3

PM3

PM1

PM1

PM2

PM2

PM2

SS1

SS1

SS2

SS2

SS4

SC

SES

SES

SES

SES

SES

QRY

QRY

HV-N

HV-S

BP-N

BP-N

BP-N

BP-N

BP-N

BP-S

BP-S

BP-S

WW-N

WW-N

--

--

--

--

--

--

--

--

--

2.61

1.56

1.64

3.22

2.66

1.95

2.80

4.34

5.63

6.71

11.0

6.77

5.26

5.33

12.7

12.7

11.2

14.9

1.39

.215

9.77

8.89

8.21

7.49

7.42

4.41

5.21

12.7

20.8

5.48

6.57

4.25

8.23

9.41

12.3

11.0

24.3

5.49

6.87

5.06

3.59

.865

.468

7.94

6.66

7.12

3.58

.08

25.46

21.30

22.91

7.86

8.93

8.16

9.28

9.55

10.00

10.99

10.33

10.47

8.11

9.09

6.80

6.82

6.96

7.02

8.38

6.27

9.16

9.20

9.10

9.03

9.10

6.73

6.52

10.40

9.59

11.15

12.20

11.12

11.53

11.61

12.00

11.79

13.21

9.63

7.94

11.66

6.39

7.68

8.52

10.34

12.74

12.81

10.68

15.47

9.46

4.60

5.90

-1.14

-1.24

-.22

-.94

-2.26

-2.67

-3.87

-3.12

-3.47

-2.33

-3.14

-4.89

-2.74

-3.29

-2.84

-4.15

-2.83

-4.34

-4.12

-4.37

-4.08

-3.97

-.28

-.01

-.81

-.01

-2.41

-2.16

-1.66

-2.83

-2.83

-4.52

-3.44

-4.74

-1.85

-2.08

-.94

-4.71

-5.22

-4.54

-2.20

.60

.42

-2.63

1.13
86 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Table 29. Nitrogen and oxygen isotope ratios for nitrate in surface water.

[mg/L, milligrams per liter; per mil, difference in parts per thousand from value reference standard]

Site 

number

Station

identification

number

Other 

identifier Date

Nitrogen, 

NO +NO , 2 3

dissolved 

(mg/L as N)

(00631)

δ15N in

nitrate fraction,

water

(per mil)

(82690)

δ18O in

nitrate fraction,

water

(per mil)

(63041)

38 06412000 RC3 10/17/07 0.035 10.08 -0.82

68 435628103324600 SPCR2 07/23/07 .525 11.59 -8.08

68 435628103324600 SPCR2 09/05/07 1.60 12.36 -4.98

69 06406920 SPCR3 09/05/07 .029 7.40 -7.80
Table 30. Concentrations of microbiological indicators in ground water.[Shading denotes background sites. col/100 mL, colonies per 100 milliliters; mpn/100 mL, most probable number per 100 milliliters; pres or abs/L, presence or absence per litermilliliters. Collection method: P, pumped; B, bailed; T, tap near production well or spring. U, analyzed for but not detected; --, no data; <, less than; M, presence verified but no

Site

number

Station

identification

number

Date Other identifier Collection method Fecal coliform (col/100 mL) Escherichia coli (mpn/100mL) Enterococci (mpn/100mL) Clostridium perfringens (col/100 mL) Coliphage, somatic (pres or abs/L) Coliphage, somatic (plaq/100 mL) 

1223444555666789999

101010111111

440214103072601440144103075301440144103075301440204103064101440150103064001440150103064001440150103064001440147103064901440147103064901440147103064901440141103064001440141103064001440141103064001440131103070401441400103235801441401103235101441401103235101441401103235101441401103235101441353103232001441353103232001441353103232001441352103232601441352103232601441352103232601

09/13/0609/14/0607/26/0709/18/0609/21/0609/21/0607/26/0710/10/0606/26/0707/26/0709/21/0606/26/0707/26/0705/17/0708/29/0709/27/0607/02/0708/29/0710/24/0705/15/0708/28/0710/29/0705/15/0708/28/0710/29/07

GV1GV6GV6GV7GV3GV3GV3GV2GV2GV2GV4GV4GV4GV5MS-WMS-EMS-EMS-EMS-EPM3PM3PM3PM1PM1PM1

PP

B

PPPPPP

B

PP

BBB

PPPP

B

PP

BB

P

UUUUUU

8

UUUUUUUUUU

4

UUUUU

4

U

UU

2

UUU

56

UUUUUUUUU

1

101

5

UUUU

13

U

----

6.4

------

1

--U

18

--U

5.3

--U--

3.1

21

U--UU--

2

U

----------------

<1

----

<1

--------

<1<1<1

----------

<1

----------------

U

----

U

--------

U

MM

----------

U

----------------

<1

----

<1

--------

<1<1<1

----------

<1
Table 30. Concentrations of microbiological indicators in ground water.—Continued [Shading denotes background sites. col/100 mL, colonies per 100 milliliters; mpn/100 mL, most probable number per 100 milliliters; pres or abs/L, presence or absence per litermilliliters. Collection method: P, pumped; B, bailed; T, tap near production well or spring. U, analyzed for but not detected; --, no data; <, less than; M, presence verified but no

Station Clostridium Coliphage, Coliphage, Coli

Site Other Collection Fecal coliform Escherichia coli Enterococci identification Date perfringens somatic somatic F-sp

number identifier method (col/100 mL) (mpn/100mL) (mpn/100mL) number (col/100 mL) (pres or abs/L) (plaq/100 mL) (pres 

12 441349103232301 10/12/06 PM2 P U U -- -- -- -- 

12 441349103232301 04/03/07 PM2 P U U U <1 U <1 12 441349103232301 08/28/07 PM2 P 68 99 2 <1 U <1 12 441349103232301 10/24/07 PM2 P 2 U U <1 U <1 13 441303103220601 05/16/07 SS1 B U U -- -- -- -- 

13 441303103220601 08/28/07 SS1 B U U 6 -- -- -- 

13 441303103220601 11/19/07 SS1 B U U 9.9 -- -- -- 

14 441302103220602 10/19/06 SS2 B U U -- -- -- -- 

14 441302103220602 08/29/07 SS2 B U U >200.5 -- -- -- 

14 441302103220602 11/19/07 SS2 P U U U -- -- -- 

15 441302103220501 10/16/06 SS4 P U U -- -- -- -- 

15 441302103220501 11/19/07 SS4 P U U U -- -- -- 

16 441222103221201 10/19/06 SC B 6.8 U -- -- -- -- 

16 441222103221201 11/05/07 SC B U U 48 -- -- -- 

17 441215103213301 09/28/06 SES P U U -- -- -- -- 

17 441215103213301 04/03/07 SES P U U U <1 U <1 17 441215103213301 06/27/07 SES P U U U <1 U <1 17 441215103213301 09/06/07 SES P U U U <1 U <1 17 441215103213301 11/07/07 SES P U U U <1 U <1 17 441215103213301 01/10/08 SES P U U U -- -- -- 

18 440709103174101 10/12/06 QRY B U U -- -- -- -- 

18 440709103174101 06/20/07 QRY B U U U -- -- -- 

18 440709103174101 11/03/07 QRY B U U U -- -- -- 
Table 30. Concentrations of microbiological indicators in ground water.—Continued [Shading denotes background sites. col/100 mL, colonies per 100 milliliters; mpn/100 mL, most probable number per 100 milliliters; pres or abs/L, presence or absence per litemilliliters. Collection method: P, pumped; B, bailed; T, tap near production well or spring. U, analyzed for but not detected; --, no data; <, less than; M, presence verified but no

Station Clostridium Coliphage, Coliphage, 

Site Other Collection Fecal coliform Escherichia coli Enterococci identification Date perfringens somatic somatic 

number identifier method (col/100 mL) (mpn/100mL) (mpn/100mL) number (col/100 mL) (pres or abs/L) (plaq/100 mL) (p

19 440644103182901 05/16/07 HV-N B U U -- -- -- -- 

19 440644103182901 06/18/07 HV-N B U U 1 -- -- -- 

20 440642103182901 05/16/07 HV-S B 20 14 -- -- -- -- 

20 440642103182901 06/14/07 HV-S B U U 6.3 -- -- -- 

21 440451103180201 09/12/06 BP-N P U 3 -- -- -- -- 

21 440451103180201 04/03/07 BP-N P U U U <1 U <1 

21 440451103180201 06/27/07 BP-N P U 1 1 <1 U <1 

21 440451103180201 09/06/07 BP-N P 14 4 U <1 U <1 

21 440451103180201 11/07/07 BP-N P U 1 U <1 U <1 

21 440451103180201 01/10/08 BP-N P U U U -- -- -- 

22 440446103175701 10/05/06 BP-S B U U -- -- -- -- 

22 440446103175701 05/22/07 BP-S B U U -- -- -- -- 

22 440446103175701 06/18/07 BP-S B U U U -- -- -- 

22 440446103175701 09/19/07 BP-S B U 4 1 -- -- -- 

22 440446103175701 01/10/08 BP-S B U U U -- -- -- 

23 440143103163001 06/28/07 WW-N B U U 1 -- -- -- 

23 440143103163001 10/03/07 WW-N B U U 1 -- -- -- 

24 435823103160901 05/22/07 NY B U U -- -- -- -- 

25 435938103220501 05/14/07 VG B 10 U -- -- -- -- 

26 440510103261701 05/01/07 -- T U U -- -- -- -- 

26 440510103261701 07/02/07 -- T U U U <1 U 1 
Table 30. Concentrations of microbiological indicators in ground water.—Continued [Shading denotes background sites. col/100 mL, colonies per 100 milliliters; mpn/100 mL, most probable number per 100 milliliters; pres or abs/L, presence or absence per litermilliliters. Collection method: P, pumped; B, bailed; T, tap near production well or spring. U, analyzed for but not detected; --, no data; <, less than; M, presence verified but no

Station Clostridium Coliphage, Coliphage, C

Site Other Collection Fecal coliform Escherichia coli Enterococci identification Date perfringens somatic somatic 

number identifier method (col/100 mL) (mpn/100mL) (mpn/100mL) number (col/100 mL) (pres or abs/L) (plaq/100 mL) (pr

27 440504103262201 05/17/07 -- T U U -- -- -- -- 

27 440504103262201 07/16/07 -- T U U 2 <1 U <1 

28 440459103265001 06/20/07 -- T U U -- -- -- -- 

29 440454103262301 07/02/07 -- T U U U -- -- -- 

30 440452103262201 07/02/07 -- T U U U -- -- -- 

31 440452103255101 04/26/07 -- T U U -- -- -- -- 

32 440447103254901 06/21/07 -- T U U -- -- -- -- 

33 440442103260201 06/21/07 -- T U U -- -- -- -- 

34 440416103253401 06/25/07 -- T U U -- -- -- -- 

35 440324103250501 06/19/07 -- T U U -- -- -- -- 

36 440318103233901 06/20/07 -- T U 6 -- -- -- -- 

36 440318103233901 07/25/07 -- T U U U <1 U <1 

39 440245103301501 05/02/07 -- T U U -- -- -- -- 

40 440218103302101 06/19/07 -- T U U -- -- -- -- 

41 440205103300501 05/02/07 -- T U U -- -- -- -- 

42 440505103335401 06/11/07 -- T U U -- -- -- -- 

43 440505103335402 06/14/07 -- T U U -- -- -- -- 

44 440505103335001 06/11/07 -- T U U -- -- -- -- 

44 440505103335001 07/16/07 -- T U U 2 <1 U <1 

44 440505103335001 07/25/07 -- T U U U <1 -- <1 

45 440505103334801 06/12/07 -- T U U -- -- -- -- 

46 440504103335701 06/11/07 -- T U U -- -- -- -- 

47 440503103335501 06/12/07 -- T U U -- -- -- -- 

48 440502103334701 06/19/07 -- T U U -- -- -- -- 

48 440502103334701 07/25/07 -- T U U 1 <1 U <1 
Table 30. Concentrations of microbiological indicators in ground water.—Continued[Shading denotes background sites. col/100 mL, colonies per 100 milliliters; mpn/100 mL, most probable number per 100 milliliters; pres or abs/L, presence or absence per litemilliliters. Collection method: P, pumped; B, bailed; T, tap near production well or spring. U, analyzed for but not detected; --, no data; <, less than; M, presence verified but no

Site

number

Station

identification

number

Date Other identifier Collection method Fecal coliform (col/100 mL) Escherichia coli (mpn/100mL) Enterococci (mpn/100mL) Clostridium perfringens (col/100 mL) Coliphage, somatic (pres or abs/L) Coliphage, somatic (plaq/100 mL) 

4950515253545556575859606162

440501103335201440501103335101440459103334801440458103334802440458103334801440457103334101435753103320401435707103320101435703103314101435654103312101435645103310601435637103321201435630103311901435619103331101

06/13/07 --06/13/07 --

06/12/07 --06/12/07 --06/13/07 --06/11/07 --07/10/07 --07/10/07 --07/09/07 --07/10/07 --07/09/07 --07/09/07 --07/10/07 --07/09/07 --

TTTTTTTTTTTTTT

UUUUUUUUUUUUUU

UUUUUUUUUUUUUU

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

-- -- -- -- 

U -- -- -- 

-- -- -- -- 

-- -- -- -- 
Table 31. Concentrations of microbiological indicators in surface water. [Shading denotes upstream (background) sites. col/100 mL, colonies per 100 milliliters; mpn/100 mL, most probable number per 100 milliliters; plaq/100 mL, plaques per 100 mU, analyzed for but not detected; <, less than; E, estimated; --, no data] Site number Station identification number Date Other identifier Fecal coliform (col/100 mL) Escherichia coli (mpn/100mL) Enterococci (mpn/100mL) Clostridium per- fringens (col/100 mL) Coliphage, somatic (plaq/100 mL) Col

F-s

(plaq

37373838636363646464656565666666676768686969 06411900 06411900 06412000 06412000 435720103273401 435720103273401 435720103273401 06406960 06406960 06406960 06406760 06406760 06406760 435436103352201 435436103352201 435436103352201 06406700 06406700 435628103324600 435628103324600 06406920 06406920 07/24/07 10/17/07 07/24/07 10/17/07 05/10/06 09/26/06 05/09/07 05/10/06 09/26/06 05/09/07 05/31/06 09/26/06 05/09/07 05/31/06 09/26/06 05/09/07 07/23/07 09/05/07 07/23/07 09/05/07 07/23/07 09/05/07 RC1 RC1 RC3 RC3 CALUMET2 CALUMET2 CALUMET2 CALUMET1 CALUMET1 CALUMET1 RENO2 RENO2 RENO2 RENO1 RENO1 RENO1 SPCR1 SPCR1 SPRC2 SPRC2 SPCR3 SPCR3 4U4UU30U441222U41216U541274169820 21141U768831874141131627246158423 10530 UUUU------------------------ 3.1U3.1 5.1 16219 <1<1E5<1------------------------ <1<1E3E1E7E3 <1<11<1------------------------ 52202225 66025 
Table 32. Summary of organic wastewater compounds analyzed in ground-water and surface-water samples.[Units for concentration are micrograms per liter. CASRN, Chemical Abstracts Service Registry Number; MRL, minimum reporting level] 

Organic wastewater 

compound CASRN1

MRL for 

samples 

collected 

before 

10/1/2007

MRL for 

samples 

collected 

after 

10/1/2007

Number 

of 

environmental samples

Number 

of 

environmental 

detections2

Frequency 

of environmental 

detection 

(percent)

Number 

of blank 

samples

Number of 

blank 

detections2,3

Frequency 

of blank 

detection 

(percent)

1,4-Dichlorobenzene 106–46–7 0.1 0.1 35 0 0 32 0 0 Deodorizer, m

1-Methyl-naphthalene 90–12–0 .1 .1 35 0 0 32 0 0 Gasoline hydr2,6-Dimethyl-naphthalene 581–42–0 .2 .1 35 0 0 32 0 0 Gasoline hydr2-Methyl-naphthalene 91–57–6 .1 .1 35 0 0 32 0 0 Gasoline hydr3-beta-Coprostanol 360–68–9 2 1 35 1 2.9 32 0 0 Fecal sterol.3-Methyl-1H-indole 83–34–1 .08 .08 35 1 2.9 32 0 0 Bacterial meta

perfume ma

3-tert-Butyl-4-hydroxy-anisole 25013–16–5 .6 .6 35 0 0 32 0 0 Antioxidant.4-Cumylphenol 599–64–4 .14 .1 35 0 0 32 0 0 Detergent met4-Nonylphenol 84852–15–3 2 1 35 0 0 32 1 3.1 Detergent met4-Octylphenol 1806–26–4 .16 .16 35 0 0 32 0 0 Detergent met4-tert-Octylphenol 140–66–9 .1 1 35 0 0 32 0 0 Detergent met5-Methyl-1H-benzotriazole 136–85–6 2 .08 35 0 0 32 0 0 Anticorrosive.9,10-Anthraquinone 84–65–1 .2 .2 35 0 0 32 0 0 Organic synthAcetophenone 98–86–2 .1 .1 35 0 0 32 0 0 Fragrance.Acetyl hexamethyl tetrahydronaphthalene (AHTN) 21145–77–7 .5 .5 35 0 0 32 0 0 Fragrance.Anthracene 120–12–7 .1 .1 35 0 0 32 0 0 Pavement- and 

pounds.

Benzo[a]-pyrene 50–32–8 .1 .1 35 0 0 32 0 0 Pavement- and 

pounds.

Benzophenone 119–61–9 .2 .1 35 2 5.7 32 3 9.4 Photo initiatorbeta-Sitosterol 83–46–5 2 3 35 1 2.9 32 0 0 Plant sterol.beta-Stigmastanol 19466–47–8 2 1 35 0 0 32 0 0 Plant sterol.Bisphenol A 80–05–7 .4 .4 5 0 0 32 0 0 Plasticizer.
Table 32. Summary of organic wastewater compounds analyzed in ground-water and surface-water samples.—Continued [Units for concentration are micrograms per liter. CASRN, Chemical Abstracts Service Registry Number; MRL, minimum reporting level] Organic wastewater compound CASRN1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 Number of environ- mental samples Number of environ- mental detections2 Frequency of environ- mental detection (percent) Number of blank samples Number of blank detections2,3 Frequency of blank detection (percent) 

Bromacil Caffeine Camphor Carbaryl Carbazole Chlorpyrifos Cholesterol Cotinine DEET Diazinon Diethoxy-nonylphenol Diethoxy-octylphenol d-Limonene Fluoranthene Hexahydrohexa-methylcyclo- penta-benzopyran (HHCB) Indole Isoborneol Isophorone Isopropylbenzene Isoquinoline Menthol Metalaxyl 314–40–9 58–08–2 76–22–2 63–25–2 86–74–8 2921–88–2 57–88–5 486–56–6 134–62–3 333–41–5 26027–38–2 26636–32–8 5989–27–5 206–44–0 1222–05–5 120–72–9 124–76–5 78–59–1 98–82–8 119–65–3 89–78–1 57837–19–1 0.4.2.1 1.1.2 1.4.2.2 51.1.1.5.1.1.1.1.4.2.2 0.4.1.1 1.1.1 1.4.1.1 51.04 .1.5.1.1.1.1.2.2.1 3535 433353535 3535 42735353535353535353535353535 004600051 4100000110020000 00 418000 142.9 43700002.9 2.9 005.7 0000 32323232323232323232323232323232323232323232 00200000150000000010000 006.3 0000047000000003.1 0000 Herbicides an

Stimulant (noFumigant and 

Insecticides aOrganic synthInsecticides aPlant- or animNicotine metaInsect repelleInsecticides aDetergent meDetergent meSolvent, fragrPavement- an

pounds. Fragrance. Amino-acid minert ingred

Fragrance, flaSolvents. Solvents. Chemical and 

ing. Pharmeceuticvorant. Fungicides.
Table 32. Summary of organic wastewater compounds analyzed in ground-water and surface-water samples.—Continued[Units for concentration are micrograms per liter. CASRN, Chemical Abstracts Service Registry Number; MRL, minimum reporting level] 

Organic wastewater compound CASRN1

MRL for 

samples 

collected 

before 

10/1/2007

MRL for 

samples 

collected 

after 

10/1/2007

Number 

of 

environmental samples

Number 

of 

environmental 

detections2

Frequency 

of environmental 

detection 

(percent)

Number 

of blank 

samples

Number of 

blank detections2,3

Frequency 

of blank 

detection 

(percent)

Methyl salicylateMetolachlorMono-ethoxy-octylphenolNaphthalenep-Cresol

PentachlorophenolPhenanthrenePhenolPrometonPyreneTetrachloroetheneTribromomethaneTributyl phosphateTriclosanTriethyl citrateTriphenyl phosphateTris-(2-butoxyethyl) phosphateTris-(2-chloroethyl) phosphateTris-(dichloroisopropyl) phosphate

119–36–851218–45–226636–32–891–20–3106–44–587–86–585–01–8108–95–21610–18–0129–00–0127–18–475–25–2126–73–83380–34–577–93–0115–86–678–51–3115–96–813674–87–8

0.2

.2

1

.1.18

2

.1.4.4.1.2.1.2.2.4.2.5.2.2

0.1

.1

1

.1.18

2

.1.2.2.1.1.1.2.2.2.1.4.1.1

35

35

353535

5

3535

35

35

35

35

35

353535353535

2

0

000002

3

1

5

11002241

5.70000005.7

8.6

2.9

14

2.92.9005.75.7

11

2.9

3232323232323232

32

32323232323232323232

10010006

0

0101006200

3.1003.1000

19

003.103.100

19

6.300

Flavoring ageHerbicides an

Detergent meGasoline hydAntioxidant, 

tion byprod

Fungicides.Pavement- an

pounds.

Resin and pha

disinfectan

Herbicides anPavement- an

pounds.

Solvents.Disinfection bPlasticizer.AntimicrobiaPlasticizer.Plasticizer.Fire retardantFire retardantFire retardant

1This report contains CAS Registry Numbers®, which is a Registered Trademark of the American Chemical Society. The CAS recommends the verification of the CASRNs t2Detection is defined as concentrations greater than the MRL, estimated values, or when presence is indicated but cannot be quantified.3Blank detections used for censoring environmental values are included.4Value adjusted for detections in companion blank samples.
Table 33. Concentrations of organic wastewater compounds in ground water. [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site no. Station identification number Date Time Sample type 1,4-Dichloro- benzene 1-Methyl- naphthalene 2,6-Dimethyl- naphthalene 2-Methyl- naphthalene 3-beta- Coprostanol 3-Methyl-1H- indole 3-tert- Butyl-4- hydroxy- anisole 

Percent of field blank samples with detections1 Percent of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 00.1.1 00.1.1 00.2.1 00.1.1 04.0 21 00.08 .08 00.6.6 

555669999999111112121212121414141717171717171717 440147103064901 440147103064901 440147103064901 440141103064001 440141103064001 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441352103232601 441352103232601 441349103232301 441349103232301 441349103232301 441349103232301 441349103232301 441302103220602 441302103220602 441302103220602 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 06/26/07 06/26/07 06/26/07 06/26/07 06/26/07 07/02/07 07/02/07 07/02/07 08/29/07 08/29/07 10/24/07 10/24/07 10/29/07 10/29/07 04/03/07 08/28/07 08/28/07 10/24/07 10/24/07 11/19/07 11/19/07 11/19/07 04/03/07 06/27/07 06/27/07 06/27/07 09/06/07 09/06/07 11/07/07 11/07/07 1015 1020 1025 1245 1250 1525 1530 1535 1340 1345 1255 1300 1220 1220 1415 1220 1225 1125 1130 1120 1125 1130 1210 1300 1305 1310 1440 1445 1205 1210 Blank Environmental Replicate Blank Environmental Blank Environmental Replicate Blank Environmental Blank Environmental Blank Environmental Environmental Blank Environmental Blank Environmental Blank Environmental Replicate Environmental Blank Environmental Replicate Blank Environmental Blank Environmental <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued[Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site 

no.

Station identification 

number Date Time Sample type

1,4- 

Dichlorobenzene 1-Methyl- naphthalene 2,6-Dime- thyl-naph- thalene 2-Methyl- naphtha- lene 3-beta- Copros- tanol 3-Methyl- 1H-indole 3-tert- Butyl-4- hydroxy- anisole 4-Cu

phe

Percentage of field blank samples with detections1

Percentage of environmental samples with detections1

MRL for samples collected before 10/1/2007

MRL for samples collected after 10/1/2007

00

.1.1

00

.1.1

00

.2.1

00

.1.1

04.021

00

.08.08

00

.6.6

21 440451103180201 04/03/07 930 Environmental < < < < < < < 

21 440451103180201 06/27/07 935 Blank < < < < < < < 

21 440451103180201 06/27/07 940 Environmental < < < < < < < 

21 440451103180201 09/06/07 1025 Blank < < < < < < < 

21 440451103180201 09/06/07 1030 Environmental < < < < < < < 

21 440451103180201 11/07/07 1420 Blank < < < < < < < 

21 440451103180201 11/07/07 1425 Environmental < < < < < < < 

22 440446103175701 09/24/07 1305 Blank < < < < < < < 

22 440446103175701 09/24/07 1310 Environmental < < < < < < < 

23 440143103163001 10/03/07 1155 Blank < < < < < < < 

23 440143103163001 10/03/07 1200 Environmental < < < < M < < 

26 440510103261701 07/02/07 1225 Blank < < < < < < < 

26 440510103261701 07/02/07 1230 Environmental < < < < < < < 

27 440504103262201 07/16/07 855 Blank < < < < < < < 

27 440504103262201 07/16/07 900 Environmental < < < < < < < 

36 440318103233901 07/25/07 1215 Blank < < < < < < < 

36 440318103233901 07/25/07 1220 Environmental < < < < < < < 

44 440505103335001 07/25/07 1050 Blank < < < < < < < 

44 440505103335001 07/25/07 1055 Environmental < < < < < < < 

48 440502103334701 07/25/07 945 Blank < < < < < < < 

48 440502103334701 07/25/07 950 Environmental < < < < < < < 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, est

Site no. Station identification number Date Time Sample type 4-Nonyl- phenol 4-tert-Octyl- phenol 5-Methyl- 1H-benzo- triazole 9,10-Anthra- quinone Aceto- phenone Acetyl hexamethyl tetrahydro naphthalene (AHTN) Anthracene Be

p

Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 4.5 021 00.1 1 002.08 00.2.2 00.1.1 00.5.5 00.1.1 

5556699999991111121212121214141417171717171717

17

440147103064901440147103064901440147103064901440141103064001440141103064001441401103235101441401103235101441401103235101441401103235101441401103235101441401103235101441401103235101441352103232601441352103232601441349103232301441349103232301441349103232301441349103232301441349103232301441302103220602441302103220602441302103220602441215103213301441215103213301441215103213301441215103213301441215103213301441215103213301441215103213301441215103213301

06/26/0706/26/0706/26/0706/26/0706/26/0707/02/0707/02/0707/02/0708/29/0708/29/0710/24/0710/24/0710/29/0710/29/0704/03/0708/28/0708/28/0710/24/0710/24/0711/19/0711/19/0711/19/0704/03/0706/27/0706/27/0706/27/0709/06/0709/06/0711/07/0711/07/07

101510201025124512501525153015351340134512551300122012201415122012251125113011201125113012101300130513101440144512051210

BlankEnvironmental

ReplicateBlankEnvironmentalBlankEnvironmentalReplicateBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalReplicateEnvironmentalBlankEnvironmentalReplicateBlankEnvironmentalBlankEnvironmental

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, est

Site 

no.

Station identification 

number Date Time Sample type 4-Nonyl- phenol 4-tert-Octyl- phenol 5-Methyl- 1H-benzo- triazole 9,10-Anthra- quinone Aceto- phenone

Acetyl 

hexamethyl 

tetrahydro 

naphthalene 

(AHTN)

Anthracene B

p

Percentage of field blank samples with detections1 4.5 0 0 0 0 0 0 

Percentage of environmental samples with detections1 0 0 0 0 0 0 0 

MRL for samples collected before 10/1/2007 2 .1 2 .2 .1 .5 .1 

MRL for samples collected after 10/1/2007 1 1 .08 .2 .1 .5 .1 

21 440451103180201 04/03/07 930 Environmental < < < < < < < 

21 440451103180201 06/27/07 935 Blank < < < < < < < 

21 440451103180201 06/27/07 940 Environmental < < < < < < < 

21 440451103180201 09/06/07 1025 Blank < < < < < < < 

21 440451103180201 09/06/07 1030 Environmental < < < < < < < 

21 440451103180201 11/07/07 1420 Blank < < < < < < < 

21 440451103180201 11/07/07 1425 Environmental < < < < < < < 

22 440446103175701 09/24/07 1305 Blank < < < < < < < 

22 440446103175701 09/24/07 1310 Environmental < < < < < < < 

23 440143103163001 10/03/07 1155 Blank < < < < < < < 

23 440143103163001 10/03/07 1200 Environmental < < < < < < < 

26 440510103261701 07/02/07 1225 Blank < < < < < < < 

26 440510103261701 07/02/07 1230 Environmental < < < < < < < 

27 440504103262201 07/16/07 855 Blank M < < < < < < 

27 440504103262201 07/16/07 900 Environmental < < < < < < < 

36 440318103233901 07/25/07 1215 Blank < < < < < < < 

36 440318103233901 07/25/07 1220 Environmental < < < < < < < 

44 440505103335001 07/25/07 1050 Blank < < < < < < < 

44 440505103335001 07/25/07 1055 Environmental < < < < < < < 

48 440502103334701 07/25/07 945 Blank < < < < < < < 

48 440502103334701 07/25/07 950 Environmental < < < < < < < 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site no. Station identification number Date Time Sample type beta- Sitosterol beta- Stigma- stanol Bisphenol A Bromacil Caffeine Camphor Carbaryl Carba

Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 04.0 23 0021 00.4.4 00.4.4 00.2.1 04.0.1.1 0011 00

555669999999111112121212121414141717171717171717 440147103064901 440147103064901 440147103064901 440141103064001 440141103064001 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441352103232601 441352103232601 441349103232301 441349103232301 441349103232301 441349103232301 441349103232301 441302103220602 441302103220602 441302103220602 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 06/26/07 06/26/07 06/26/07 06/26/07 06/26/07 07/02/07 07/02/07 07/02/07 08/29/07 08/29/07 10/24/07 10/24/07 10/29/07 10/29/07 04/03/07 08/28/07 08/28/07 10/24/07 10/24/07 11/19/07 11/19/07 11/19/07 04/03/07 06/27/07 06/27/07 06/27/07 09/06/07 09/06/07 11/07/07 11/07/07 1015 1020 1025 1245 1250 1525 1530 1535 1340 1345 1255 1300 1220 1220 1415 1220 1225 1125 1130 1120 1125 1130 1210 1300 1305 1310 1440 1445 1205 1210 Blank Environmental Replicate Blank Environmental Blank Environmental Replicate Blank Environmental Blank Environmental Blank Environmental Environmental Blank Environmental Blank Environmental Blank Environmental Replicate Environmental Blank Environmental Replicate Blank Environmental Blank Environmental <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< --------------------------------------<<<------------<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued[Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site 

no.

Station identification 

number Date Time Sample type beta- Sitosterol beta- Stigma- stanol Bisphenol A Bromacil Caffeine Camphor Carbaryl Carba

Percentage of field blank samples with detections1

Percentage of environmental samples with detections1

MRL for samples collected before 10/1/2007

MRL for samples collected after 10/1/2007

04.023

0021

00

.4.4

00

.4.4

00

.2.1

04.0

.1.1

0011

00

212121212121212222232326262727363644444848

440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440446103175701440446103175701440143103163001440143103163001440510103261701440510103261701440504103262201440504103262201440318103233901440318103233901440505103335001440505103335001440502103334701440502103334701

04/03/0706/27/0706/27/0709/06/0709/06/0711/07/0711/07/0709/24/0709/24/0710/03/0710/03/0707/02/0707/02/0707/16/0707/16/0707/25/0707/25/0707/25/0707/25/0707/25/0707/25/07

930935940

1025103014201425130513101155120012251230

855900

1215122010501055

945950

EnvironmentalBlankEnvironmental

BlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmental

<<<<<<<<<<M<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

----------<<----------------------------

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

M<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site no. Station identification number Date Time Sample type Cholesterol Cotinine DEET Diazinon Diethoxy- nonylphenol Diethoxy- octylphenol d-Limonene Fluo

Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 04.0 11 00.4.4 5932.2.1 00.2.1 0055 0011 00.1.04 

5556699999991111121212121214141417171717171717

17

440147103064901440147103064901440147103064901440141103064001440141103064001441401103235101441401103235101441401103235101441401103235101441401103235101441401103235101441401103235101441352103232601441352103232601441349103232301441349103232301441349103232301441349103232301441349103232301441302103220602441302103220602441302103220602441215103213301441215103213301441215103213301441215103213301441215103213301441215103213301441215103213301441215103213301

06/26/0706/26/0706/26/0706/26/0706/26/0707/02/0707/02/0707/02/0708/29/0708/29/0710/24/0710/24/0710/29/0710/29/0704/03/0708/28/0708/28/0710/24/0710/24/0711/19/0711/19/0711/19/0704/03/0706/27/0706/27/0706/27/0709/06/0709/06/0711/07/0711/07/07

101510201025124512501525153015351340134512551300122012201415122012251125113011201125113012101300130513101440144512051210

BlankEnvironmental

ReplicateBlankEnvironmentalBlankEnvironmentalReplicateBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalReplicateEnvironmentalBlankEnvironmentalReplicateBlankEnvironmentalBlankEnvironmental

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

M<<M<<<<M<M<M

M2

<<MM<<MMMM

M2

M<MM

M2

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued[Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site 

no.

Station identification 

number Date Time Sample type Cholesterol Cotinine DEET Diazinon Diethoxy- nonylphenol Diethoxy- octylphenol d-Limonene Flu

Percentage of field blank samples with detections1 0 0 59 0 0 0 0 

Percentage of environmental samples with detections1 4.0 0 32 0 0 0 0 

MRL for samples collected before 10/1/2007 1 .4 .2 .2 5 1 .1 

MRL for samples collected after 10/1/2007 1 .4 .1 .1 5 1 .04 

21 440451103180201 04/03/07 930 Environmental < < M < < < < 21 440451103180201 06/27/07 935 Blank < < M < < < < 21 440451103180201 06/27/07 940 Environmental < < M2 < < < < 

21 440451103180201 09/06/07 1025 Blank < < M < < < < 21 440451103180201 09/06/07 1030 Environmental < < < < < < < 21 440451103180201 11/07/07 1420 Blank < < M < < < < 

21 440451103180201 11/07/07 1425 Environmental < < M2 < < < < 

22 440446103175701 09/24/07 1305 Blank < < M < < < < 22 440446103175701 09/24/07 1310 Environmental < < 2E.1 < < < < 

23 440143103163001 10/03/07 1155 Blank < < < < < < < 

23 440143103163001 10/03/07 1200 Environmental M < E.1 < < < < 

26 440510103261701 07/02/07 1225 Blank < < < < < < < 

26 440510103261701 07/02/07 1230 Environmental < < < < < < < 

27 440504103262201 07/16/07 855 Blank < < M < < < < 

27 440504103262201 07/16/07 900 Environmental < < < < < < < 

36 440318103233901 07/25/07 1215 Blank < < < < < < < 

36 440318103233901 07/25/07 1220 Environmental < < < < < < < 44 440505103335001 07/25/07 1050 Blank < < < < < < < 44 440505103335001 07/25/07 1055 Environmental < < < < < < < 48 440502103334701 07/25/07 945 Blank < < < < < < < 48 440502103334701 07/25/07 950 Environmental < < < < < < < 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site no. Station identification number Date Time Sample type Indole Isoborneol Isophorone Isopropyl- benzene Isoquinoline Menthol Metalaxyl 

Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 00.1.1 00.1.1 00.1.1 00.1.1 00.4.2 00.2.2 00.2.1 

555669999999111112121212121414141717171717171717 440147103064901 440147103064901 440147103064901 440141103064001 440141103064001 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441352103232601 441352103232601 441349103232301 441349103232301 441349103232301 441349103232301 441349103232301 441302103220602 441302103220602 441302103220602 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 06/26/07 06/26/07 06/26/07 06/26/07 06/26/07 07/02/07 07/02/07 07/02/07 08/29/07 08/29/07 10/24/07 10/24/07 10/29/07 10/29/07 04/03/07 08/28/07 08/28/07 10/24/07 10/24/07 11/19/07 11/19/07 11/19/07 04/03/07 06/27/07 06/27/07 06/27/07 09/06/07 09/06/07 11/07/07 11/07/07 1015 1020 1025 1245 1250 1525 1530 1535 1340 1345 1255 1300 1220 1220 1415 1220 1225 1125 1130 1120 1125 1130 1210 1300 1305 1310 1440 1445 1205 1210 Blank Environmental Replicate Blank Environmental Blank Environmental Replicate Blank Environmental Blank Environmental Blank Environmental Environmental Blank Environmental Blank Environmental Blank Environmental Replicate Environmental Blank Environmental Replicate Blank Environmental Blank Environmental <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued[Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site 

no.

Station identification 

number Date Time Sample type Indole Isoborneol Isophorone Isopropyl- benzene Isoquinoline Menthol Metalaxyl 

Percentage of field blank samples with detections1

Percentage of environmental samples with detections1

MRL for samples collected before 10/1/2007

MRL for samples collected after 10/1/2007

00

.1.1

00

.1.1

00

.1.1

00

.1.1

00

.4.2

00

.2.2

00

.2.1

212121212121212222232326262727363644444848

440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440446103175701440446103175701440143103163001440143103163001440510103261701440510103261701440504103262201440504103262201440318103233901440318103233901440505103335001440505103335001440502103334701440502103334701

04/03/0706/27/0706/27/0709/06/0709/06/0711/07/0711/07/0709/24/0709/24/0710/03/0710/03/0707/02/0707/02/0707/16/0707/16/0707/25/0707/25/0707/25/0707/25/0707/25/0707/25/07

930935940

1025103014201425130513101155120012251230

855900

1215122010501055

945950

EnvironmentalBlankEnvironmental

BlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmental

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site no. Station identification number Date Time Sample type Mono- ethoxy- octylphenol Naphthalene p-Cresol Penta- chloro- phenol Phenanthrene Phenol Prometon 

Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 0011 00.1.1 00.18 .18 0022 00.1.1 270.4.2 012.4.2 

555669999999111112121212121414141717171717171717 440147103064901 440147103064901 440147103064901 440141103064001 440141103064001 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441352103232601 441352103232601 441349103232301 441349103232301 441349103232301 441349103232301 441349103232301 441302103220602 441302103220602 441302103220602 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 06/26/07 06/26/07 06/26/07 06/26/07 06/26/07 07/02/07 07/02/07 07/02/07 08/29/07 08/29/07 10/24/07 10/24/07 10/29/07 10/29/07 04/03/07 08/28/07 08/28/07 10/24/07 10/24/07 11/19/07 11/19/07 11/19/07 04/03/07 06/27/07 06/27/07 06/27/07 09/06/07 09/06/07 11/07/07 11/07/07 1015 1020 1025 1245 1250 1525 1530 1535 1340 1345 1255 1300 1220 1220 1415 1220 1225 1125 1130 1120 1125 1130 1210 1300 1305 1310 1440 1445 1205 1210 Blank Environmental Replicate Blank Environmental Blank Environmental Replicate Blank Environmental Blank Environmental Blank Environmental Environmental Blank Environmental Blank Environmental Blank Environmental Replicate Environmental Blank Environmental Replicate Blank Environmental Blank Environmental <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< --------------------------------------<<<------------<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<E.2<<<<<<E.2<<<<<<<<<<<<E.1<<<<<< <MM<<<<<<<<<<<<<<<<<<<<<<<<<<< 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued[Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site 

no.

Station identification 

number Date Time Sample type

Monoethoxyoctylphenol Naphthalene p-Cresol Penta- chloro- phenol Phenanthrene Phenol Prometon 

Percentage of field blank samples with detections1

Percentage of environmental samples with detections1

MRL for samples collected before 10/1/2007

MRL for samples collected after 10/1/2007

0011

00

.1.1

00

.18.18

0022

00

.1.1

27

0

.4.2

0

12

.4.2

212121212121212222232326262727363644444848

440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440446103175701440446103175701440143103163001440143103163001440510103261701440510103261701440504103262201440504103262201440318103233901440318103233901440505103335001440505103335001440502103334701440502103334701

04/03/0706/27/0706/27/0709/06/0709/06/0711/07/0711/07/0709/24/0709/24/0710/03/0710/03/0707/02/0707/02/0707/16/0707/16/0707/25/0707/25/0707/25/0707/25/0707/25/0707/25/07

930935940

1025103014201425130513101155120012251230

855900

1215122010501055

945950

EnvironmentalBlankEnvironmental

BlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmental

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

----------<<----------------------------

<<<<<<<<<<<<<<<<<<<<<

<

E.1

<<<<<<<

E.3

<

E.1

<<<<<<<<<

<<M<<<<<M<<<<<<<<<<<<
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued [Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, esti

Site no. Station identification number Date Time Sample type Tribromo- methane Tributyl phosphate Triclosan Triethyl citrate Triphenyl phosphate Tris- (2-butoxyethyl) phosphate Tris- (2-chloroeth

phosphate 

Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 00.1.1 00.2.2 00.2.2 00.4.2 278.0.2.1 9.1 0.5.4 04.0.2.1 

555669999999111112121212121414141717171717171717 440147103064901 440147103064901 440147103064901 440141103064001 440141103064001 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441401103235101 441352103232601 441352103232601 441349103232301 441349103232301 441349103232301 441349103232301 441349103232301 441302103220602 441302103220602 441302103220602 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 441215103213301 06/26/07 06/26/07 06/26/07 06/26/07 06/26/07 07/02/07 07/02/07 07/02/07 08/29/07 08/29/07 10/24/07 10/24/07 10/29/07 10/29/07 04/03/07 08/28/07 08/28/07 10/24/07 10/24/07 11/19/07 11/19/07 11/19/07 04/03/07 06/27/07 06/27/07 06/27/07 09/06/07 09/06/07 11/07/07 11/07/07 1015 1020 1025 1245 1250 1525 1530 1535 1340 1345 1255 1300 1220 1220 1415 1220 1225 1125 1130 1120 1125 1130 1210 1300 1305 1310 1440 1445 1205 1210 Blank Environmental Replicate Blank Environmental Blank Environmental Replicate Blank Environmental Blank Environmental Blank Environmental Environmental Blank Environmental Blank Environmental Blank Environmental Replicate Environmental Blank Environmental Replicate Blank Environmental Blank Environmental <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<<<<<<<<<<< <<<<<<<<M<M<M<<<M<<<<<<M<<<<M< <<<<<<<<<<<<E.1<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<.2.2<<<<<<<< 
Table 33. Concentrations of organic wastewater compounds in ground water.—Continued

[Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated but cannot be quantified; --, not analyzed; E, est

Site no. Station identification number Date Time Sample type Tribromo- methane Tributyl phosphate Triclosan Triethyl citrate Triphenyl phosphate Tris- (2-butoxyethyl) phosphate Tris- (2-chloroet

yl) phospha

Percentage of field blank samples with detections1

Percentage of environmental samples with detections1

MRL for samples collected before 10/1/2007

MRL for samples collected after 10/1/2007

00

.1.1

00

.2.2

00

.2.2

00

.4.2

27

8.0

.2.1

9.10

.5.4

04.0

.2.1

212121212121212222232326262727363644444848

440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440451103180201440446103175701440446103175701440143103163001440143103163001440510103261701440510103261701440504103262201440504103262201440318103233901440318103233901440505103335001440505103335001440502103334701440502103334701

04/03/0706/27/0706/27/0709/06/0709/06/0711/07/0711/07/0709/24/0709/24/0710/03/0710/03/0707/02/0707/02/0707/16/0707/16/0707/25/0707/25/0707/25/0707/25/0707/25/0707/25/07

930935940

1025103014201425130513101155120012251230

855900

1215122010501055

945950

EnvironmentalBlankEnvironmental

BlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmental

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<M<<M<<<<<<<<<<<<<<

<<<<<<<<<<<<<

E.9

<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

1Detection is defined as concentrations greater than the MRL, estimated values, or when presence is indicated but cannot be quantified.2Value censored owing to detection in companion blank sample.
Table 34. Concentrations of organic wastewater compounds in surface water. [Shading denotes upstream (background) sites. Units are micrograms per liter. MR mated; --, not analyzed] Site Station identification Date Time Sample type number number Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 37 06411900 07/24/2007 905 Blank L, minimum 1,4- Dichloro- benzene 00.1.1< reporting leve 1-Methyl- naphthalene 00.1.1< l; <, less than m 2,6-Dimethyl- naphthalene 00.2.1< inimum reporti 2-Methyl- naphthalene 00.1.1< ng level; M, pre 3-beta- Coprostanol 0021< sence is indica 3-Methyl- 1H-indole 010.08 .08 < ted bu

3-t

Buty

hydr

anis

00

37 06411900 07/24/2007 910 Environmental < < < < < < 

3737 06411900 06411900 07/24/2007 10/17/2007 915 955 Replicate Blank << << << << << << 

37 06411900 10/17/2007 1000 Environmental < < < < < < 

38 06412000 07/24/2007 1135 Blank < < < < < < 

38 06412000 07/24/2007 1140 Environmental < < < < < < 

3838 06412000 06412000 10/17/2007 10/17/2007 1150 1155 Blank Environmental << << << << << << 

67 06406700 07/23/2007 1025 Blank < < < < < < 

67 06406700 07/23/2007 1030 Environmental < < < < < M 

67 06406700 09/05/2007 1055 Blank < < < < < < 

6768 06406700 435628103324600 09/05/2007 07/23/2007 1100 1215 Environmental Blank << << << << << << 

68 435628103324600 07/23/2007 1220 Environmental < < < < < < 

68 435628103324600 09/05/2007 1210 Blank < < < < < < 

68 435628103324600 09/05/2007 1215 Environmental < < < < < < 

6969 06406920 06406920 07/23/2007 07/23/2007 1325 1330 Blank Environmental << << << << << << 

69 06406920 09/05/2007 1310 Blank < < < < < < 

69 06406920 09/05/2007 1315 Environmental < < < < < < 
Table 34. Concentrations of organic wastewater compounds in surface water.—Continued[Shading denotes upstream (background) sites. Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated bumated; --, not analyzed]

Site 

number

Station identification 

number Date Time Sample type 4-Nonyl- phenol 4-tert-Octyl- phenol 5-Methyl-1H- benzo-triazole 9,10-Anthra- quinone Aceto- phenone

Acetyl 

hexamethyl 

tetrahydro 

naphthalene 

(AHTN)

Anthracene Ben

py

Percentage of field blank samples with detections1 0 0 0 0 0 0 0 0 

Percentage of environmental samples with detections1 0 0 0 0 0 0 0 0 

MRL for samples collected before 10/1/2007 2 .1 2 .2 .1 .5 .1 

MRL for samples collected after 10/1/2007 1 1 .08 .2 .1 .5 .1 

37 06411900 07/24/2007 905 Blank < < < < < < < 

37 06411900 07/24/2007 910 Environmental < < < < < < < 

37 06411900 07/24/2007 915 Replicate < < < < < < < 

37 06411900 10/17/2007 955 Blank < < < < < < < 

37 06411900 10/17/2007 1000 Environmental < < < < < < < 

38 06412000 07/24/2007 1135 Blank < < < < < < < 

38 06412000 07/24/2007 1140 Environmental < < < < < < < 

38 06412000 10/17/2007 1150 Blank < < < < < < < 

38 06412000 10/17/2007 1155 Environmental < < < < < < < 

67 06406700 07/23/2007 1025 Blank < < < < < < < 

67 06406700 07/23/2007 1030 Environmental < < < < < < < 

67 06406700 09/05/2007 1055 Blank < < < < < < < 

67 06406700 09/05/2007 1100 Environmental < < < < < < < 

68 435628103324600 07/23/2007 1215 Blank < < < < < < < 

68 435628103324600 07/23/2007 1220 Environmental < < < < < < < 

68 435628103324600 09/05/2007 1210 Blank < < < < < < < 

68 435628103324600 09/05/2007 1215 Environmental < < < < < < < 

69 06406920 07/23/2007 1325 Blank < < < < < < < 

69 06406920 07/23/2007 1330 Environmental < < < < < < < 

69 06406920 09/05/2007 1310 Blank < < < < < < < 

69 06406920 09/05/2007 1315 Environmental < < < < < < < 
Table 34. Concentrations of organic wastewater compounds in surface water.—Continued [Shading denotes upstream (background) sites. Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated bestimated; --, not analyzed] Site number Station identification number Date Time Sample type beta- Stigma- stanol Bromacil Caffeine Camphor Carbaryl Carbazole Chlorpyrifos Cholesterol 

Percentage of field blank samples with detections1 Percentage of environmental samples with detections1 MRL for samples collected before 10/1/2007 MRL for samples collected after 10/1/2007 0021 00.4.4 00.2.1 2063.1.1 0011 00.1.1 00.2.1 04011 

373737373738383838676767676868686869696969 06411900 06411900 06411900 06411900 06411900 06412000 06412000 06412000 06412000 06406700 06406700 06406700 06406700 435628103324600 435628103324600 435628103324600 435628103324600 06406920 06406920 06406920 06406920 07/24/2007 07/24/2007 07/24/2007 10/17/2007 10/17/2007 07/24/2007 07/24/2007 10/17/2007 10/17/2007 07/23/2007 07/23/2007 09/05/2007 09/05/2007 07/23/2007 07/23/2007 09/05/2007 09/05/2007 07/23/2007 07/23/2007 09/05/2007 09/05/2007 905 910 915 955 1000 1135 1140 1150 1155 1025 1030 1055 1100 1215 1220 1210 1215 1325 1330 1310 1315 Blank Environmental Replicate Blank Environmental Blank Environmental Blank Environmental Blank Environmental Blank Environmental Blank Environmental Blank Environmental Blank Environmental Blank Environmental <<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<< <<<<<<M<<<MMM2 <M<M<MMM2 <<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<< <<<<<<<<<<<<<<<<<<<<< <<<<M<<<M<M<<< E1<<<<<< 
Table 34. Concentrations of organic wastewater compounds in surface water.—Continued [Shading denotes upstream (background) sites. Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated bestimated; --, not analyzed]

Site 

number

Station identification 

number Date Time Sample type

Diethoxynonylphenol Diethoxy- octyl- phenol d- Limonene Fluor- anthene

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB)

Indole Iso- borneol Iso- phorone Iso- propyl- benzene 

Percentage of field blank samples with detections1 0 0 0 0 0 0 0 10 0 

Percentage of environmental samples with detections1 0 0 0 10 0 0 0 20 0 

MRL for samples collected before 10/1/2007 5 1 .1 .1 .5 .1 .1 .1 .1 

MRL for samples collected after 10/1/2007 5 1 .04 .1 .5 .1 .1 .1 .1 

37 06411900 07/24/2007 905 Blank < < < < < < < < < 

37 06411900 07/24/2007 910 Environmental < < < < < < < < < 

37 06411900 07/24/2007 915 Replicate < < < < < < < < < 

37 06411900 10/17/2007 955 Blank < < < < < < < < < 

37 06411900 10/17/2007 1000 Environmental < < < < < < < < < 

38 06412000 07/24/2007 1135 Blank < < < < < < < < < 

38 06412000 07/24/2007 1140 Environmental < < < < < < < < < 

38 06412000 10/17/2007 1150 Blank < < < < < < < < < 

38 06412000 10/17/2007 1155 Environmental < < < < < < < < < 

67 06406700 07/23/2007 1025 Blank < < < < < < < < < 

67 06406700 07/23/2007 1030 Environmental < < < < < < < < < 

67 06406700 09/05/2007 1055 Blank < < < < < < < M < 

67 06406700 09/05/2007 1100 Environmental < < < < < < < < < 

68 435628103324600 07/23/2007 1215 Blank < < < < < < < < < 

68 435628103324600 07/23/2007 1220 Environmental < < < M < < < < < 

68 435628103324600 09/05/2007 1210 Blank < < < < < < < < < 

68 435628103324600 09/05/2007 1215 Environmental < < < < < < < M < 

69 06406920 07/23/2007 1325 Blank < < < < < < < < < 

69 06406920 07/23/2007 1330 Environmental < < < < < < < < < 

69 06406920 09/05/2007 1310 Blank < < < < < < < < < 

69 06406920 09/05/2007 1315 Environmental < < < < < < < M < 
Table 34. Concentrations of organic wastewater compounds in surface water.—Continued [Shading denotes upstream (background) sites. Units are micrograms pe estimated; --, not analyzed] Site Station identification Date Time Sample type number number Percentage of field blank samples with detections1 r liter. MRL, Metalaxyl 0 minimum re Methyl salicylate 10 porting level; Metolachlor 0 <, less than Mono- ethoxy- octyl- phenol 0 minimum repor Naphthalene 10 ting level; M p-Cresol 0 , presence i Penta- chloro- phenol -- s indicated b

Phen- anthrene 0 

Percentage of environmental samples with detections1 0 20 0 0 0 0 -- 0 

MRL for samples collected before 10/1/2007 .2 .2 .2 1 .1 .18 2 .1 

37 MRL for samples 06411900 collected after 07/24/2007 10/1/2007 905 Blank .1< .1< .1< 1< .1< .18 2 < -- .1< 

37 06411900 07/24/2007 910 Environmental < < < < < < -- < 

37 06411900 07/24/2007 915 Replicate < < < < < < -- < 

37 06411900 10/17/2007 955 Blank < < < < < < -- < 

37 06411900 10/17/2007 1000 Environmental < < < < < < -- < 

38 06412000 07/24/2007 1135 Blank < < < < < < -- < 

38 06412000 07/24/2007 1140 Environmental < M < < < < -- < 

38 06412000 10/17/2007 1150 Blank < < < < < < -- < 

38 06412000 10/17/2007 1155 Environmental < < < < < < -- < 

67 06406700 07/23/2007 1025 Blank < < < < < < -- < 

67 06406700 07/23/2007 1030 Environmental < M < < < < -- < 

67 06406700 09/05/2007 1055 Blank < M < < < < -- < 

67 06406700 09/05/2007 1100 Environmental < < < < < < -- < 

68 435628103324600 07/23/2007 1215 Blank < < < < < < -- < 

68 435628103324600 07/23/2007 1220 Environmental < < < < < < -- < 

68 435628103324600 09/05/2007 1210 Blank < < < < < < -- < 

68 435628103324600 09/05/2007 1215 Environmental < < < < < < -- < 

69 06406920 07/23/2007 1325 Blank < < < < < < -- < 

69 06406920 07/23/2007 1330 Environmental < < < < < < -- < 

69 06406920 09/05/2007 1310 Blank < < < < M < -- < 

69 06406920 09/05/2007 1315 Environmental < < < < < < -- < 
Table 34. Concentrations of organic wastewater compounds in surface water.—Continued [Shading denotes upstream (background) sites. Units are micrograms per liter. MRL, minimum reporting level; <, less than minimum reporting level; M, presence is indicated bestimated; --, not analyzed]

Site 

number

Station identification 

number Date Time Sample type Pyrene

Tetrachloroethene Tribromo- methane Tributyl phosphate Triclosan Triethyl citrate Triphenyl phosphate Tris- (2-butoxyeth- yl) phosphate 

(2

yl

Percentage of field blank samples with detections1

Percentage of environmental samples with detections1

MRL for samples collected before 10/1/2007

MRL for samples collected after 10/1/2007

0

10

.1.1

00

.2.1

0

10

.1.1

1010

.2.2

00

.2.2

00

.4.2

00

.2.1

0

20

.5.4

373737373738383838676767676868686869696969

0641190006411900064119000641190006411900064120000641200006412000064120000640670006406700064067000640670043562810332460043562810332460043562810332460043562810332460006406920064069200640692006406920

07/24/200707/24/200707/24/200710/17/200710/17/200707/24/200707/24/200710/17/200710/17/200707/23/200707/23/200709/05/200709/05/200707/23/200707/23/200709/05/200709/05/200707/23/200707/23/200709/05/200709/05/2007

905910915955

10001135114011501155102510301055110012151220121012151325133013101315

BlankEnvironmental

ReplicateBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmentalBlankEnvironmental

<<<<<<<<<<<<<<M<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<M<<<<<<<<<<

<<<<<<<<<<<M<<<<M<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<<<<<<<<

<<<<<<<<<<<<<<

E.2

<

E.5

<<<<

1Detection is defined as concentrations greater than the MRL, estimated values, or when presence is indicated but cannot be quantified.2Value censored owing to detection in companion blank sample.
116 Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota

Publishing support provided by: 

Helena and Rolla Publishing Service Centers 

For more information concerning this publication, contact:

Director, USGS South Dakota Water Science Center

1608 Mt. View Road

Rapid City, SD 57702

(605) 394–3200

Or visit the South Dakota Water Science Center Web site at:

http://sd.water.usgs.gov
Supplemental Information 117
Putnam and others—Water-Quality Effects and Indicators of Onsite Wastewater Disposal Systems, East-Central Black Hills Area, South Dakota—SIR 2008–5232

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