104o 45' 103o30' EXPLANATION Horse Indian OUTCROP OF MADISON 44o45' Cr Belle Fourche T. 9 N. LIMESTONE Reservoir Owl Newell BELL Creek Creek MADISON LIMESTONE ABSENT E Nisland F SATURATED THICKNESS OF O BELLE FOURCHE U MADISON AQUIFER, IN RC RIVER T. 8 N. HE FEET (from Clawges, 2000a) Hay Creek R Less than 200 E BUTTE CO Vale I V 200 to 400 ER R CE CO MEADE CO REDWAT LAWREN 400 to 600 Cox T. 7 N. Saint Creek 600 to 800 Lake Crow Onge Fully saturated Creek eek Cr 30' Gulch Spearfish Bear T. 6 N. x Butte Gulch Whitewood

Bottom d Creek e ls Bear a Creek F Whitewoo Butte Higgins Creek Cr STURGIS Squ T. 5 N. Spearfish a Central Tinton w i Cr kal r Iron CityCr Al ood DEADWOOD o Cr w 103 ad 15' Beave Cr e D Cr Lead Bear h nnie s A Cr rry i trawbe f S r Cr Creek Tilford T. 4 N. a

e Whitetail p

S Cheyenne Elk Crossing it Creek L tle Roubaix Elk eek Creek N r Elk 15' Little C . Boxelder ish F rf o a r Piedmont T. 3 N. e k Ellsworth p R

S S. Fork Rapid a Air Force p Base i Nemo d C Blackhawk Creek Cold Sp Cr r rin Cr g ee s k Box Elder T. 2 N. k For Rochford s adN o . Fo h rk C Rapid RAPID CITY R astl B Castle e C ea r ve r Rapid C k Pactola Creek r C e e e C r T. 1 N. e r Reservoir k e Creek ek Castle V

Deerfield ictoria Creek r Reservoir 44o S. Fork C e Sheridan Castl Lake T. 1 S. Rockerville Creek Hill City Mt. Rushmore National Keystone Memorial yon an Harney Iron Hayward LIMESTONE PLATEAU C Peak

n Spring Mountain T. 2 S.

o n x

y O x o PENNINGTON C n Battle

a y Cr Sylvan pok Hermosa n S C CO a a CUSTER Lake Iron ne C Cree Creek s k le o Calamity Grace Bear B T. 3 S. French Peak Gulch Creek CUSTER x Redbird e Gillette idg Creek Cool 45' CUSTER Jewel Cave National STATE Monument Beaver French Fairburn T. 4 S.

PARK

Canyon Creek ighl H an Lame Canyon d C Creek o Wind Cave tt o T. 5 S. Pringle National Park n Creek w o

o

WYOMING d

Wind Johnn Creek

Cave SOUTH DAKOTA SOUTH Onyx Beaver y Dewey Cave Red T. 6 S.

k Creek

o RIVER Hell o Buffalo Gap 30' r B d Creek l

o CO C FALL RIVER H on ot ny T. 7 S. Brook Ca HOT SPRINGS Minnekahta Fall Oral R R. 8 E. R. 9 E. CHEYENNE Cascade Springs T. 8 S.

Edgemont Horsehead

Angostura T. 9 S. Creek o Creek Reservoir 43 15' d oo w n o tt o Creek R. 5 E. R. 6 E. R. 7 E. C Igloo 01020MILES Provo T. 10 S.

Hat 01020KILOMETERS

R. 1 E. R. 2 E. R. 3 E. R. 4 E. Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13

Figure 24. Saturated thickness of the Madison aquifer.

Availability of Ground-Water Resources 25 104o 45' 103o30' EXPLANATION Indian Horse o OUTCROP OF MINNELUSA 44 45' Belle Fourche Cr T. 9 N. Reservoir FORMATION Owl Newell BELL Creek Creek MINNELUSA FORMATION ABSENT E Nisland SATURATED THICKNESS OF F BELLE FOURCHE O MINNELUSA AQUIFER, IN UR T. 8 N. CHE RIVER FEET (from Clawges, 2000b) Hay Creek R Less than 200

E BUTTE CO Vale V 200 to 400 R R I O ATE LAWRENCE CO MEADE C REDW 400 to 600 Cox T. 7 N. Saint Creek 600 to 800 Lake Crow Onge 800 to 1,000

Creek reek 1,000 to 1,200 Gulch Spearfish C 30' Fully saturated Bear T. 6 N. Whitewood x Butte Gulch No data

Bottom Creek e ls Bear a Creek F Whitewood Butte Higgins Creek Cr Sq STURGIS T. 5 N. Spearfish u a Central i Tinton Cr w lkal r Iron CityCr A ood DEADWOOD o Cr w 15' 103 ad Beave Cr e D Cr Lead Bear h nnie s A Cr rry i trawbe f S r Cr Creek Tilford T. 4 N. a

e Whitetail p

S Cheyenne Elk Crossing it Creek L tle Roubaix Elk eek Creek N r Elk 15' Little C . Boxelder ish F rf o a r Piedmont T. 3 N. e k Ellsworth p R

S S. Fork Rapid a Air Force p Base i Nemo d

C Blackhawk Creek Cold Sp Cr r rin Cr g ee s k Box Elder T. 2 N. k For Rochford s adN o . Fo h rk C Rapid R astl RAPID CITY B Castle e C ea r ve r Rapid C k Pactola Creek r C e e e C r T. 1 N. e r Reservoir k e Creek ek Castle V

Deerfield ictoria Creek r Reservoir 44o S. Fork C e Sheridan Castl Lake T. 1 S. Rockerville Creek Hill City Mt. Rushmore National Keystone Memorial yon an Harney Iron Hayward LIMESTONE PLATEAU C Peak

n Spring Mountain T. 2 S.

o n x

y O x o PENNINGTON C n Battle

a y Cr Sylvan pok Hermosa n S C CO a a CUSTER Lake Iron ne C Cree Creek s k le o Calamity Grace Bear B T. 3 S. French Peak Gulch Creek CUSTER x Redbird e Gillette idg Creek Cool 45' CUSTER Jewel Cave National STATE Monument Beaver French Fairburn T. 4 S.

PARK

Canyon Creek ighl H an Lame Canyon d C Creek o Wind Cave tt o T. 5 S. Pringle National Park n Creek w o

o

WYOMING d

Wind Johnn Creek

Cave SOUTH DAKOTA SOUTH Onyx Beaver y Dewey Cave Red T. 6 S.

k Creek

o RIVER Hell o Buffalo Gap 30' r B d Creek l

o CO C FALL RIVER H on o ny T. 7 S. t Brook Ca HOT SPRINGS Minnekahta Fall Oral R R. 8 E. R. 9 E. CHEYENNE Cascade Springs T. 8 S.

Edgemont Horsehead Angostura T. 9 S. Creek o Creek Reservoir 43 15' d oo w n o tt o Creek R. 5 E. R. 6 E. R. 7 E. C Igloo 01020MILES Provo T. 10 S.

Hat 01020KILOMETERS

R. 1 E. R. 2 E. R. 3 E. R. 4 E. Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13

Figure 25. Saturated thickness of the Minnelusa aquifer.

26 Ground-Water Resources in the Black Hills Area, South Dakota 3,480 health-based standards that are related to the A Whitewood Madison (site 1) aesthetics of water use (U.S. Environmental 3,460 Whitewood Minnelusa (site 2) Protection Agency, 1994). 104o 45' 103o30' o 44 45' 3,440

3 BUTTE CO LAWRENCE CO MEADE CO 3,420 30' General Characteristics for Major 1, 2 3,400 15' 103o Aquifers 3,380 15' 1984 1986 1988 1990 1992 1994 1996 1998 A brief summary of water-quality char-

RAPID 3,540 acteristics from Williamson and Carter CITY 44o 4 B Redwater Minnelusa (site 3) (2001) for the major aquifers in the study area 3,520

LIMESTONE PLATEAU (Deadwood, Madison, Minnelusa, Minne- PENNINGTON CO CUSTER CO kahta, and Inyan Kara aquifers) is presented 45' 3,500 in this section of the report. Characteristics

MING for the Precambrian aquifer also are included WYO

SOUTH DAKOTA SOUTH 3,480 30' in this section of the report because numerous FALL RIVER CO wells are completed in this aquifer in the 3,460 1960 1965 1970 1975 1980 1985 1990 1995 1999 crystalline core of the Black Hills. 43o15' 3,600 Water temperature affects the useful- C Reptile Gardens Madison (site 4) ness of water for many purposes. For example, hot water needs to be cooled prior to EXPLANATION 3,550 consumption; however, hot water is desirable OUTCROP OF MADISON for geothermal heating purposes. The tem- LIMESTONE perature of water from wells completed in the OUTCROP OF MINNELUSA 3,500 FORMATION Madison aquifer is shown in figure 27. Water temperatures generally increase with well 3,450 depth. Temperatures measured in the Mad- 1984 1986 1988 1990 1992 1994 1996 1998 ison aquifer generally are the warmest of the CALENDAR YEAR major aquifers in the study area because it generally is the deepest aquifer used at dis- Figure 26. Selected hydrographs illustrating trends in ground-water levels. tance from the outcrop. The Madison aquifer is the primary source of water for warm artesian springs in the southern Black Hills; factors other than aquifer depth may affect water temperatures in this area (Whalen, Chemical constituents in ground water WATER QUALITY OF GROUND-WATER 1994). RESOURCES also can result from human sources, such as industrial, domestic, and agricultural chemi- The total of all dissolved mineral con- cals, that have the potential to contaminate stituents is measured as the dissolved solids This section of the report includes a concentration. Specific conductance is a mea- summary of water-quality characteristics for the water. The potential for ground-water sure of the ability of water to conduct an elec- both major aquifers and selected minor aqui- contamination in the Black Hills area can be trical current. It is highly dependent on the fers in the Black Hills area. A summary of large because many of the outcrops, which amount of dissolved solids (such as salt) in water quality relative to water use also is pre- are important aquifer recharge areas, could the water. Pure water, such as distilled water, sented. More detailed descriptions of ground- be subject to various forms of land develop- has a very low specific conductance. Specific water quality were presented by Williamson ment. Rapid ground-water velocities also are conductance is an important water-quality and Carter (2001). possible in many aquifers because of high measurement because it can be used to esti- Water quality is a measure of the suit- secondary permeability. Contamination by mate dissolved solids concentrations, which ability of water for a particular use based on septic tanks has been documented for some may affect the taste of water and suitability selected physical, chemical, and biological wells in the Blackhawk, Piedmont, and for various uses. When comparing samples, a characteristics. The quality of ground water is Sturgis areas (Bartlett and West Engineers, higher specific conductance indicates a an important consideration because aquifers Inc., 1998). higher dissolved solids concentration. Dis- provide water for a variety of purposes solved constituents tend to increase with res- including drinking water, livestock watering, Standards and guidelines have been idence time as indicated by the increase in irrigation, and industrial use. The quality of established to protect water for various desig- specific conductance in the Madison and water can change as it flows over the land sur- nated uses. The U.S. Environmental Protec- Minnelusa aquifers with distance from the face in streams and lakes and as it flows tion Agency (USEPA) and the States are Madison Limestone and Minnelusa Forma- underground. Because ground-water and sur- responsible for establishing the standards for tion outcrops (figs. 28 and 29). face-water resources in the Black Hills area constituents in water that have been shown to can be highly interconnected, the quality of pose a risk to human health. Although Specific conductance generally is lower surface water can affect the quality of ground drinking-water standards apply only to public in water from the Precambrian, Deadwood, water, and vice versa. water supplies, individuals using water from and Minnekahta aquifers than in water from Ground water can contain numerous private wells should be aware of potential the other major aquifers. Generally, water from the Inyan Kara aquifer is high in spe- substances (constituents) from natural and health risks associated with drinking water cific conductance even in some outcrop areas human sources that typically are measured that exceeds these standards. Maximum Con- using laboratory analyses. Some constituents of the Inyan Kara Group (fig. 30) and is taminant Levels (MCLs) are established for higher in specific conductance than the other potentially can cause serious health effects. constituents that, if present in drinking water, As ground water comes in contact with soil major aquifers due to greater amounts of may cause adverse human health effects; and rock materials, some of the chemicals, shale within the Inyan Kara Group. Water minerals, and nutrients dissolve and become MCLs are enforceable health-based stan- obtained from shales may contain rather high part of the water chemistry. Two fundamental dards (U.S. Environmental Protection concentrations of dissolved solids (Hem, factors influencing water chemistry are the Agency, 1994). Secondary Maximum Con- 1985) and, hence, high specific conductance. type of geologic materials that are present taminant Levels (SMCLs) are established for Because depths to aquifers increase with dis- and the length of time that water is in contact constituents that can adversely affect the tance from outcrop in most locations, concen- with those materials (Winter and others, taste, odor, or appearance of water and may trations of dissolved solids generally increase 1998), which typically increases constituent result in discontinuation of use of the water; with well depth, as shown by the example concentrations from natural sources. SMCLs are nonenforceable, generally non- relation in figure 31.

Water Quality of Ground-Water Resources 27 o o 104o 45' 103 30' EXPLANATION 104o 45' 103 30' EXPLANATION

OUTCROP OF MADISON Horse Horse o o Indian 44 Belle Fourche Indian OUTCROP OF MADISON 44 Belle Fourche Cr Reservoir Cr LIMESTONE Reservoir 45' Owl 45' Owl LIMESTONE Newell Creek Newell BELLE Creek MADISON LIMESTONE BELLE Creek Creek MADISON LIMESTONE Nisland ABSENT Nisland F F O ABSENT BELLE FOURCHE O BELLE FOURCHE U UR WATER TEMPERATURE, RC RIVER CHE RIVER HE SPECIFIC CONDUCTANCE Creek Hay Creek

Hay IN DEGREES CELSIUS R R

E BUTTE CO Vale OF SAMPLE, IN MICRO- E BUTTE CO Vale V R I V Less than 20 R R I MEADE CO TER LAWRENCE CO MEADE CO ATE LAWRENCE CO SIEMENS PER CENTI- REDWA 20 to 30 REDW Cox METER AT 25 DEGREES Cox Saint Creek Saint Creek 30 to 40 Lake Lake Crow Onge Crow Onge CELSIUS

Creek Creek 40 to 50 ek reek re Less than 500 Gulch Spearfish C Greater than 50 30' Gulch Spearfish C 30' Bear Bear 500 to 1,000 x Butte Whitewood x Butte Whitewood Gulch Gulch WELL COMPLETED IN MADISON Bottom Bottom 1,000 to 1,500 Creek Creek e se AQUIFER FOR WHICH THERE ls l Bear a Creek Bear a Creek F F IS A WATER TEMPERATURE Whitewood Butte Greater than 1,500 Whitewood Butte Higgins Higgins Cr Creek Cr Creek STURGIS Sq STURGIS Squ u Spearfish a Central Spearfish a Central w Tinton w MEASUREMENT Tinton Cr i Cr City li Iron CityCr al Iron Cr ka od DEADWOOD lk o od DEADWOOD l o Cr o A Cr wo A dw 15' 103 d 15' 103 a a Beaver Cr e Beaver Cr e D D Cr Bear Cr Lead Bear nie Lead h nnie Cr h n Cr s A berry s A berry i Straw i Straw f f r Cr Creek Tilford r Cr Creek Tilford a hitetail a hitetail e W e W p p Cheyenne Elk Cheye Elk S S nne Crossing Crossing Littl Little Creek Roubaix e Creek Roubaix Creek ek Creek ek N Elk re N Elk re Elk Elk Little . C Little . C 15' F Boxelder 15' F Boxelder sh o sh o fi fi r r r r k Piedmont k Piedmont a a e e R Ellsworth R Ellsworth p p a a S Air Force S Air Force S. Fork Rapid Cr p S. Fork Rapid Cr p i i d Nemo Base d Nemo Base

C C Creek Creek r r Blackhawk Blackhawk Cold Cold Sp Spr ri in C ng Cre g ree s ek s k Box Elder k ork Box Elder For Rochford F Rochford s ds adN a N. F o . Fo o ork Rapid h rk C Rapid h Ca R a ITY R stl stle RAPID C Castle e C RAPID CITY Castle Cr Bea r Beav ve e r Rapid r Rapid k Creek ek Pactola Creek C ee Pactola C C e r C C r r C r e e r Reservoir r Reservoir e e e e e Creek e Creek k k k k Castle Castle V V Deerfield ic Creek Deerfield ict Creek toria oria rin Reservoir Spring Reservoir Sp g o r o S. Fork r S. Fork 44 C 44 C e l e Castl Cast Rockerville Rockerville Sheridan Creek Sheridan Creek Creek Creek Lake Lake Hill City Hill City Mt. Rushmore Mt. Rushmore National Keystone National Keystone Memorial Memorial yo yo n n Spring Harney n n Spring Harney a Iron Hayward LIMESTONE PLATEAU LIMESTONE PLATEAU a Iron Hayward C Peak C Peak n n Mountain

Mountain o

o

n x

y x n x O y x PENNINGTON C

PENNINGTON CO n o Battle n o Battle a

y Cr a y Cr Sylvan Spo Hermosa p Hermosa n k Sylvan S o C a n k C a O a CUSTER C Lake Iron n a CUSTER CO Lake Iron ne e C Creek Creek C Creek Creek s s e le l o Calamity Grace Bear o Calamity Grace Bear B Peak B Peak French Creek French Gulch Creek CUSTER x Gulch CUSTER x Redbird Redbird e ge Gillette idg Gillette olid Creek Cool Creek Co Jewel Cave CUSTER 45' Jewel Cave CUSTER 45' National National Monument

Beaver Monument Beaver STATE TA STATE French Fairburn French Fairburn

PARK PARK Canyon Canyon Creek Creek gh gh Hi la Lame Hi la Lame n n Canyon d C Canyon d C o o Creek t Creek t t t o o Wind Cave n Wind Cave n Pringle Pringle National Park w National Park w Creek o Creek o

o WYOMING

o

WYOMING d d Wind Wind Johnny Johnny Cave

Cave DAKOTA SOUTH SOUTH DAKO SOUTH Onyx Creek Onyx Beaver Creek Dewey Beaver Dewey Cave Red Cave Red

k Creek k

Creek o RIVER o RIVER Hell o Buffalo Gap o Buffalo Gap Hell r r 30' 30' B B d Creek d Creek l l o o

C C FALL RIVER CO H n FALL RIVER CO H on o yo ot roo ny t Brook an B k Ca HOT SPRINGS C HOT SPRINGS Minnekahta Fall Minnekahta Fall Oral Oral R R

CHEYENNE CHEYENNE

Cascade Springs Cascade Springs Edgemont Horsehe Edgemont Horsehead o Angostura ad o Angostura 43 Creek 43 Creek Reservoir Creek Reservoir Creek d od oo o w 15' w 15' n n o o tt tt o Igloo Creek o Igloo Creek C C 01020MILES Provo 01020MILES Provo 01020KILOMETERS 01020KILOMETERS Hat Hat Base modified from U.S. Geological Survey digital data, Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996 Rapid City, Office of City Engineer map, 1:18,000, 1996 Universal Transverse Mercator projection, zone 13 Universal Transverse Mercator projection, zone 13

Figure 27. Water temperature in the Madison aquifer (modified from Williamson Figure 28. Specific conductance in the Madison aquifer (modified from and Carter, 2001). Williamson and Carter, 2001).

Hardness is related to soap-consuming Water in the Inyan Kara aquifer generally is the major aquifers increase with distance characteristics of water. Hard water can hard to very hard in or near outcrop areas; from the outcrop. shorten the life of fabrics and may cause however, hardness decreases with increasing Sulfate affects the taste of water and has equipment damage. Hardness is determined distance from the outcrop (fig. 33). Similar to an SMCL of 250 mg/L. Sulfate concentra- primarily by the amount of dissolved calcium the other major bedrock aquifers, concentra- tions in the Minnelusa aquifer are dependent and magnesium in water. Water that has a tions of dissolved solids in the Inyan Kara on the amount of anhydrite present in the Minnelusa Formation. Near the outcrop, hardness less than 61 mg/L (milligrams per aquifer increase with increasing distance liter) is considered soft; 61-120 mg/L, mod- sulfate concentrations generally are low (less from the outcrop because calcium and bicar- than 250 mg/L) because anhydrite has been erately hard; 121-180 mg/L, hard; and more bonate are replaced by sodium and sulfate as than 180 mg/L, very hard (Heath, 1983). removed by dissolution. An abrupt increase water moves downgradient. in sulfate concentrations occurs downgra- Geologic units that contain few carbonate dient, where a transition zone occurs around rocks, such as the Precambrian-age rocks, In the Black Hills area, water from the the core of the Black Hills. This transition generally contain water with lower hardness major aquifers generally is fresh and low in dissolved solids in and near outcrop areas zone is an area within which the sulfate con- than geologic units that contain mostly car- centrations range from 250 to 1,000 mg/L except for parts of the Inyan Kara aquifer. bonate rocks, which are composed primarily (fig. 34) and marks an area of active removal The Madison, Minnelusa, and Inyan Kara of calcium- and magnesium-bearing min- of anhydrite by dissolution. Downgradient erals. Water in the Madison, Minnelusa, and aquifers may yield slightly saline water (dis- from the transition zone, sulfate concentra- Minnekahta aquifers generally is hard to very solved solids concentrations between 1,000 tions are greater than 1,000 mg/L, which hard (fig. 32) because the formations consist and 3,000 mg/L) at distance from the out- delineates a zone in which thick anhydrite primarily of carbonate rocks. Water in the crops, especially in the southern Black Hills. beds remain in the formation. The transition Deadwood aquifer also is hard to very hard The water in these aquifers is highly mineral- zone probably is moving downgradient over because this unit consists primarily of sand- ized outside of the study area. In general, con- geologic time as the anhydrite in the forma- stone with a calcium carbonate cement. centrations of sodium, chloride, and sulfate in tion is dissolved (Kyllonen and Peter, 1987).

28 Ground-Water Resources in the Black Hills Area, South Dakota o o o o 103 30' 104 45' 103 30' EXPLANATION 104 45' EXPLANATION Horse o Horse o 44 Belle Fourche Indian OUTCROP OF MINNELUSA 44 Indian OUTCROP OF INYAN KARA Reservoir Cr Belle Fourche Cr Reservoir wl 45' Owl Newell FORMATION 45' O Newell GROUP BELLE Creek BELLE Creek Creek MINNELUSA FORMATION INYAN KARA GROUP Nisland Nisland Creek F F O ABSENT BELLE FOURCHE O ABSENT BELLE FOURCHE U UR RC RIVER CHE RIVER SPECIFIC CONDUCTANCE HE SPECIFIC CONDUCTANCE Hay Creek Hay

Creek R R

E BUTTE CO Vale E BUTTE CO Vale OF SAMPLE, IN MICRO- OF SAMPLE, IN MICRO- V I V R I ER R MEADE CO TER LAWRENCE CO MEADE CO REDWAT LAWRENCE CO SIEMENS PER CENTI- REDWA SIEMENS PER CENTI- Cox Cox METER AT 25 DEGREES Creek Saint Creek METER AT 25 DEGREES Saint Lake Lake Crow Onge CELSIUS Crow Onge CELCIUS Creek Creek ek reek Less than 500 re Less than 500 Gulch Spearfish C Gulch Spearfish C 30' Bear 30' Bear 500 to 1,000 Butte 500 to 1,000 Whitewood x Butte Whitewood x Gulch Gulch Bottom 1,000 to 1,500 Bottom 1,000 to 1,500 Creek Creek e e ls s Bear a Creek Bear l Creek a F F Greater than 1,500 Whitewood Whitewood Butte Greater than 1,500 Higgins Higgins Cr Butte Creek Cr Creek Sq STURGIS Squ STURGIS ua a Central Central Spearfish w Spearfish w Tinton Tinton Cr i Cr City li Iron CityCr al Iron Cr ka o od DEADWOOD lk o ood DEADWOOD l Cr wo A 103 Cr w A 15' 103 d 15' ad a Cr e Beaver Cr e Beaver D D Cr Lead Bear Cr Lead Bear nie h nnie Cr h An Cr s A erry s berry i trawb i traw f S f S r Cr r Cr Creek Creek Tilford a hitetail a hitetail e W e W p p Cheyenne Elk Cheyenne Elk S S Tilford Crossing Crossing Littl Little Creek Roubaix e Creek Roubaix Creek k Creek ek N Elk ee N Elk re Elk r Elk Little C Little . C . 15' F 15' F Boxelder Boxelder h o sh o is i f r f r r r Piedmont k Piedmont a k a e e R R Ellsworth Ellsworth p p a a S S Air Force p Air Force S. Fork Rapid Cr p S. Fork Rapid C i i d Base d Nemo Base Nemo

C C Creek Creek r r Blackhawk Cold Blackhawk Cold S Spr r pri in ng Cre g Cree s k Box Elder ek s rk Box Elder k For Rochford Fo Rochford s s d adN a N. o . F o Fo Rapid h ork Rapid h rk C Ca R as RAPID CITY R stl RAPID CITY tle Castle e C Castle Cr Bea r Bea ve ve r r Rapid k Creek ek Pactola Creek C e Pactola C C re r C C re Rapid r C e r Reservoir e re Reservoir e ee Creek e e Creek k k k k Castle V Castle V Deerfield i Creek Deerfield ict Creek ctoria oria Reservoir Spring

Reservoir r o S. Fork r S o S. Fork p 44 C 44 C ri ng l e tl e Cast Rockerville Cas Rockerville Sheridan Sheridan Creek Creek Lake Creek Lake Hill City Hill City Mt. Rushmore Creek Mt. Rushmore National Keystone National Keystone Memorial Memorial o nyon Harney ny n Spring Harney a Spring Hayward Hayward LIMESTONE PLATEAU Iron LIMESTONE PLATEAU a Iron C Peak C Peak n n Mountain Mountain o

o x x y n x

y x n PENNINGTON CO PENNINGTON CO n Battle

n Battle o

o a Cr a Cr y Sylvan p Hermosa y Sylvan po Hermosa S ok S C k n C a n a CUSTER CO Lake n CUSTER CO Lake n a Iron e a Iron e C Creek Creek C Creek Creek s s e e l l Calamity Bear o Calamity Grace Bear o Grace B B Peak French Peak Creek French x Gulch Creek CUSTER x Gulch CUSTER Redbird Redbird e ge Gillette dg Gillette olid Jewel Cave Creek Cooli Creek Co 45' National CUSTER 45' Jewel Cave CUSTER Monument National

Monument Beaver Beaver

TA STATE TA STATE French Fairburn French Fairburn

PARK PARK Canyon Canyon Creek Creek ighl Highla H an Lame n Canyon d C Canyon d C o Creek o Creek t tt t o o Wind Cave Wind Cave n Pringle n Pringle Lame w National Park w National Park Creek o Creek o

o

o WYOMING

WYOMING

d d Wind Wind Johnny Johnny

Cave Cave

SOUTH DAKO SOUTH SOUTH DAKO SOUTH Onyx Beaver Creek Dewey Onyx Beaver Creek Dewey Cave

Red Cave Red k

k Creek Creek o

o RIVER Buffalo Gap RIVER Hell o o Buffalo Gap Hell r r 30' B 30' B d Creek d Creek l l o o

C C FALL RIVER CO H n FALL RIVER CO H on o yo HOT ot roo ny t Brook an B k Ca HOT SPRINGS C SPRINGS Minnekahta Minnekahta Fall Fall Oral Oral R R

CHEYENNE CHEYENNE Cascade Springs Cascade Springs Edgemont Edgemont Horsehead Horsehe

o Angostura o Angostura ad 43 Creek 43 Creek Reservoir Creek Reservoir Creek d od oo o w 15' w 15' n n o to tt t o Igloo o Igloo Creek Creek C C 01020MILES 01020MILES Provo Provo 01020KILOMETERS 01020KILOMETERS Hat Hat

Base modified from U.S. Geological Survey digital data, Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996 Rapid City, Office of City Engineer map, 1:18,000, 1996 Universal Transverse Mercator projection, zone 13 Universal Transverse Mercator projection, zone 13

Figure 29. Specific conductance in the Minnelusa aquifer (modified from Figure 30. Specific conductance in the Inyan Kara aquifer (modified from Williamson and Carter, 2001). Williamson and Carter, 2001).

Radionuclides are unstable isotopes Radium locates primarily in bone in Kara Group in the southern Black Hills. Ura- that exist throughout the environment and humans; however, inhalation or ingestion of nium may be introduced into the Inyan Kara have a certain probability of decay. Because radium may result in lung cancer. Inhaled Group by the artesian recharge of water from several radionuclides are known to cause radon is known to cause lung cancer, and the Minnelusa aquifer (Gott, 1974). Some various types of cancer, drinking-water stan- ingested radon is believed to cause cancer. In water in the Inyan Kara aquifer, especially in dards exist for these radionuclides. Most nat- the Deadwood aquifer, more than 30 percent the southern Black Hills, contains relatively urally occurring radionuclides in water are of the samples analyzed for radium-226 or high concentrations of radionuclides. Almost radium-226 and radium-228 exceeded the the result of radioactive decay of uranium and 20 percent of the samples collected from the MCL of 5 pCi/L (picocuries per liter) for the thorium. Radioactivity is the release of Inyan Kara aquifer exceed the MCL for the combined radium-226 and radium-228 stan- energy and energetic particles by changes dard. Almost 90 percent of the samples from combined radium-226 and radium-228 stan- occurring within atomic or nuclear structures the Deadwood aquifer exceed the proposed dard; all but one of the samples exceeding (Hem, 1985). Alpha, beta, and gamma radia- MCL of 300 pCi/L for radon in States this standard were from wells in the southern tion are types of radiation that commonly are without an active indoor air program (U.S. Black Hills. About 4 percent of the samples measured in ground water. Radionuclide Environmental Protection Agency, 1999); from the Inyan Kara aquifer exceed the MCL analyses can be expressed in terms of disinte- three of these samples also exceed the pro- of 30 µg/L (micrograms per liter) for ura- grations per unit time (typically in units of posed MCL of 4,000 pCi/L for radon in nium; all the samples exceeding the uranium picocuries per liter) or in mass units (typi- States with an active indoor air program (U.S. MCL were from wells located in the southern cally in units of micrograms per liter). Some Environmental Protection Agency, 1999) Black Hills. In general, gross alpha-particle of the radionuclide names include numbers, (fig. 35). activity, gross-beta activity, and radium-226 such as radium-226 and radium-228; these Uranium is a chemical and radiological are higher in the Deadwood and Inyan Kara numbers represent chemical variations of the hazard and carcinogen. Uranium deposits aquifers than in the Madison, Minnelusa, and element. have been discovered and mined in the Inyan Minnekahta aquifers.

Water Quality of Ground-Water Resources 29 10,000 9,000 General Characteristics for Minor

8,000 2 7,000 R = 0.4812 Aquifers 6,000 5,000 A brief summary of water-quality char- 4,000 acteristics from Williamson and Carter 3,000 (2001) for minor aquifers in the study area is 2,500 presented in this section of the report. The 2,000 minor aquifers in the study area include the

1,500 Newcastle aquifer, alluvial aquifers, and local aquifers that exist in various semiconfining 1,000 and confining units. These local aquifers 900 800 include the Spearfish, Sundance, Morrison, 700 Graneros, and Pierre aquifers. 600 500 Water in many of the minor aquifers can IN MILLIGRAMS PER LITER 400 be very hard (fig. 32) and high in dissolved

300 solids concentrations. Most samples from the 250 Sundance aquifer indicate slightly saline DISSOLVED SOLIDS, SUM OF CONSTITUENTS, 200 water. Sulfate concentrations also can be high in the minor aquifers, such as the Spearfish 150 aquifer where high sulfate concentrations can result from dissolution of gypsum. Both dis- 100 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 solved solids and sulfate concentrations are WELL DEPTH, IN FEET low in the Newcastle aquifer. In general, the dominance of sodium and sulfate increases Figure 31. Relation between dissolved solids and well depth for Madison aquifer. with increasing amounts of shale present in the geologic units. The dominance of cal- cium, magnesium, and bicarbonate increases with increasing amounts of sandstone and carbonate rocks present in the geologic units. Concentrations of dissolved solids in alluvial aquifers generally increase with increasing distance from the core of the Black Hills, which is largely due to contact with underlying geologic units and alluvial mate- rials derived from underlying units. Wells completed in alluvial deposits that do not overlie Cretaceous-age shales generally yield fresh water. Wells that are completed in allu- vial deposits that overlie the Cretaceous-age 112 37 127 249 28 176 13 14 15 28 10 8 116 3,000 shales generally yield slightly saline water in which sodium and/or sulfate is dominant. 2,500 Samples from alluvial aquifers may be high in uranium concentrations, especially in the 2,000 southern Black Hills.

1,500 Ground-Water Quality Relative to 1,000 Water Use

500 Concentrations exceeding SMCLs and MCLs affect the use of water in some areas HARDNESS, IN MILLIGRAMS PER LITER 0 for many aquifers within the study area. Most Precambrian Madison Minnekahta Spearfish Morrison Graneros Alluvial Deadwood Minnelusa Inyan Kara Sundance Pierre Newcastle concentrations exceeding standards are for AQUIFER various SMCLs and generally affect the water only aesthetically. Radionuclide concentra- EXPLANATION 15 Number of samples tions can be high in some of the major aqui- Outlier data value more than 3 times the interquartile range fers, especially in the Deadwood and Inyan outside the quartile Kara aquifers, and may preclude the use of Outlier data value less than or equal to 3 and more than 1.5 water in some areas. Hard water may require times the interquartile range outside the quartile special treatment for certain uses. Other fac- Data value less than or equal to 1.5 times the interquartile range outside the quartile tors, such as high concentrations of sodium 75th percentile and dissolved solids, may affect irrigation

Median use. Water from all aquifers, with the excep- tions of the Pierre and Sundance aquifers, 25th percentile generally is suitable for irrigation in most locations. Figure 32. Boxplots showing hardness for selected aquifers (from Williamson and Carter, 2001). High concentrations of iron and manga- nese, which can stain, occasionally can hamper the use of water from the Precam- brian aquifer. None of the reported samples from the Precambrian aquifer exceeded drinking-water standards for radionuclides.

30 Ground-Water Resources in the Black Hills Area, South Dakota o o 104o 45' 103 30' EXPLANATION 104o 45' 103 30' EXPLANATION

o Horse o Horse 44 Indian OUTCROP OF INYAN KARA 44 Belle Fourche Indian OUTCROP OF MINNELUSA Belle Fourche Cr Reservoir Cr GROUP wl FORMATION 45' Reservoir Owl Newell 45' O Newell BELLE Creek BELLE Creek Creek INYAN KARA GROUP ABSENT Creek MINNELUSA FORMATION Nisland Nisland F F ABSENT O O BELLE FOURCHE U WATER HARDNESS, IN MILLI- BELLE FOURCHE U R RIVER R RIVER CHE GRAMS PER LITER CHE SULFATE CONCENTRATION,

Hay Creek Hay Creek

R R E BUTTE CO Vale Very hard, greater than 180 E BUTTE CO Vale IN MILLIGRAMS PER R I V R I V TER LAWRENCE CO MEADE CO TER LAWRENCE CO MEADE CO LITER REDWA Hard, 121 to 180 REDWA Cox Cox Less than 250 Saint Creek Moderately hard, 61 to 121 Saint Creek Lake Crow Onge Lake Crow Onge 250 to 1,000 Creek Soft, less than 61 Creek reek reek Greater than 1,000 Gulch Spearfish C Gulch Spearfish C 30' Bear 30' Bear Whitewood x Butte WELL COMPLETED IN INYAN Whitewood x Butte WELL COMPLETED IN Gulch Gulch

Bottom KARA AQUIFER FOR Bottom Creek e Creek e MINNELUSA AQUIFER ls ls Bear a Creek Bear a Creek F WHICH THERE IS A HARD- F FOR WHICH THERE IS Whitewood Butte Whitewood Butte Higgins Higgins Cr STURGIS Creek Cr STURGIS Creek Squ NESS ANALYSIS Squ A SULFATE ANALYSIS Spearfish a Central Spearfish a Central Tinton w Tinton w Cr City li Cr City li Iron Cr ka o Iron Cr ka o ood DEADWOOD l ood DEADWOOD l Cr w A 15' 103 Cr w A 15' 103 ad ad Beaver Cr e Beaver Cr e D Cr Lead Bear D Cr Lead Bear h nnie Cr h nnie Cr s A erry s A erry i trawb i trawb f S f S r Cr Creek Tilford r Cr Creek Tilford a hitetail a hitetail e W e W p Cheyenne Elk p Cheyenne Elk S S Crossing Crossing Little Little Creek Roubaix ek Creek Creek Roubaix ek Creek N Elk re Elk N Elk re Elk

Little . C Little . C 15' h F Boxelder 15' h F Boxelder fis o fis o r r Piedmont r r Piedmont a k a k e e R R Ellsworth p p a a S Ellsworth S Air Force S. Fork Rapid Cr p S. Fork Rapid Cr p i Air Force i d d Base Nemo Base Nemo C C Creek Creek r Blackhawk r Blackhawk Cold S Cold Sp pri rin Cr ng Cre g ee s k Box Elder ek s k Box Elder k For Rochford For Rochford s s adN adN o . Fo o . Fo h rk C Rapid h rk C Rapid R astl RAPID CITY R astl RAPID CITY Castle e C Castle e C Be r Bea r av ve e r Rapid r k Pactola Creek k Pactola Creek C C ree Rapid C C ree r C r C e r Reservoir e r Reservoir e e e e e Creek e Creek k

k k k Castle V Castle V Deerfield ictoria Creek Deerfield ictoria Creek

Reservoir Spring Reservoir Spring r o S. Fork r o S. Fork 44 C 44 C l e l e Cast Rockerville Cast Rockerville Sheridan Creek Sheridan Creek Creek Lake Creek Lake Hill City Hill City Mt. Rushmore Mt. Rushmore National Keystone National Keystone Memorial Memorial o o ny n Spring Harney ny n Spring Harney a Hayward LIMESTONE PLATEAU a Hayward

LIMESTONE PLATEAU Iron Iron C Peak C Peak

n Mountain n Mountain

o o x n x y y

n PENNINGTON CO x PENNINGTON CO x

n Battle n o Battle o

a Cr a y Cr y Sylvan Spo Hermosa Sylvan Spo Hermosa k n k C C n a CO a CUSTER CO Lake n a CUSTER Lake n a Iron e Iron e C C Creek Creek Creek Creek s s le le o Calamity Grace Bear o Calamity Grace Bear B French Peak B French Peak Creek x Gulch Creek x Gulch CUSTER Redbird CUSTER Redbird e e Gillette lidg Gillette lidg Creek Coo Jewel Cave Creek Coo 45' Jewel Cave CUSTER 45' National CUSTER National Monument

Monument Beaver Beaver TA TA STATE French Fairburn STATE French Fairburn

PARK PARK

Canyon Canyon Creek Creek ighl ighl H an Lame H an Lame Canyon d C Canyon d C Creek o Creek o tt tt Wind Cave o Wind Cave o Pringle n Pringle n National Park w National Park w Creek o Creek o

o o

WYOMING WYOMING

d d

Wind Johnny Wind Johnny

Cave Cave

SOUTH DAKO SOUTH SOUTH DAKO SOUTH Dewey Onyx Beaver Creek Dewey Onyx Beaver Creek

Red Cave Red Cave k

k Creek Creek o o RIVER Buffalo Gap RIVER Hell o Buffalo Gap Hell o r r 30' B 30' B d Creek d Creek l l

o o

C C FALL RIVER CO H on FALL RIVER CO H on ot roo y ot roo ny B k Can HOT SPRINGS B k Ca HOT SPRINGS Minnekahta Fall Minnekahta Fall Oral Oral R R

CHEYENNE CHEYENNE Cascade Springs Cascade Springs

Edgemont Horsehead Edgemont Horsehe o Angostura o Angostura ad 43 Creek Reservoir Creek 43 Creek Reservoir Creek d d oo oo w w 15' n 15' n o o tt tt o Igloo Creek o Igloo Creek C 01020MILES C Provo Provo 01020MILES 01020KILOMETERS 01020KILOMETERS Hat Hat

Base modified from U.S. Geological Survey digital data, Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 1:100,000, 1977, 1979, 1981, 1983, 1985 Rapid City, Office of City Engineer map, 1:18,000, 1996 Rapid City, Office of City Engineer map, 1:18,000, 1996 Universal Transverse Mercator projection, zone 13 Universal Transverse Mercator projection, zone 13

Figure 33. Hardness in the Inyan Kara aquifer (modified from Williamson and Figure 34. Sulfate concentrations in the Minnelusa aquifer (modified from Carter, 2001). Naus and others, 2001).

The principal deterrents to use of water dissolved solids and sulfate. Hot water from aquifers. Concentrations of selenium, which from the Deadwood aquifer are high concen- deep wells may not be desirable for some may be harmful or potentially toxic if trations of radionuclides, including radium- uses. Arsenic concentrations in the Min- ingested in moderate excess for a long time 226 and radon. In addition, concentrations of nelusa aquifer exceed the MCL of 10 µg/L in (Callahan and others, 1979), are an additional iron and manganese can be high. some locations. Only a few samples exceed deterrent to use of water from the Sundance Water from the Madison aquifer can the MCLs for various radionuclides. aquifer in some places. Water from the Pierre contain high concentrations of iron and man- The use of water from the Inyan Kara and Sundance aquifers generally is not suit- ganese that may hamper its use. Water from aquifer may be hampered by high concentra- able for irrigation because dissolved solids the Madison aquifer is hard to very hard and tions of dissolved solids, iron, sulfate, and concentrations generally are high. Water may require special treatment for certain manganese. In the southern Black Hills, from the other minor aquifers generally is uses. In downgradient wells (generally radium-226 and uranium concentrations in suitable for irrigation, but may not be in spe- deeper than 2,000 feet), concentrations of water from this aquifer also may preclude its cific locations if concentrations of either dissolved solids and sulfate also may deter use. Hard water from wells located on or near dissolved solids or sodium are high. use from this aquifer. Hot water, from deep the outcrop of the Inyan Kara Group may wells and in the Hot Springs area, may not be require special treatment. Suitability for irri- Water from alluvial aquifers generally desirable for some uses. Radionuclide con- gation may be affected by high dissolved is very hard and may require special treat- centrations in the Madison aquifer generally solids and sodium concentrations. ment for certain uses. High concentrations of are acceptable. The use of water from the minor aqui- dissolved solids, sulfate, iron, and manganese In water from the Minnelusa aquifer, fers may be hampered by hardness and con- may limit the use of water from alluvial aqui- hardness and high concentrations of iron and centrations of dissolved solids and sulfate. fers that overlie the Cretaceous-age shales. In manganese may hamper use. Generally, Concentrations of radionuclides, with the the southern Black Hills, uranium concentra- downgradient wells (generally deeper than exception of uranium, generally are at accept- tions in alluvial aquifers can be high in many 1,000 feet) also have high concentrations of able levels in samples from these minor locations.

Water Quality of Ground-Water Resources 31 o 45' 103o30' Limestone, Minnelusa Formation, Minne- 104 EXPLANATION Indian Horse kahta Limestone, and Inyan Kara Group— o 44 45' Belle Fourche Cr OUTCROP OF DEADWOOD Reservoir Owl Newell contain major aquifers that are able to store BELLE Creek FORMATION Creek Nisland and transmit large quantities of water and are F DEADWOOD FORMATION BELLE FOURCHE O UR CHE RIVER ABSENT used extensively as water supplies within and

Hay Creek R E BUTTE CO Vale RADON CONCENTRATION I V beyond the study area. Alluvial deposits ER R MEADE CO REDWAT LAWRENCE CO OF SAMPLE—Number is Cox along streams also commonly are used as Saint Creek radon concentration in Lake Crow Onge picocuries per liter Creek local aquifers. reek Gulch Spearfish C 30' Bear Less than 300 Whitewood x Butte 80 Various information and maps are pre- Gulch

Bottom Creek e 300 to 3,000 ls Bear a Creek sented in this report to help characterize F 500 Whitewood Butte Higgins 1,6001,600 Cr Creek Squ STURGIS a water availability and quality in locations Spearfish Central Tinton w Cr i Greater than 3,000 Iron CityCr al od DEADWOOD lk o Cr o A dw 15' 103 a throughout the Black Hills. However, there is Beaver Cr e 5,300 800800 D 920920 Cr Lead 5,3005,300 Bear h nnie Cr s A erry i trawb f S r Cr Creek Tilford no guarantee of obtaining usable water at any a 6,6006,600 e Whitetail p Cheye Elk S nne Crossing location due to the extreme potential vari- Little Creek Roubaix ek Creek N Elk re Elk

Little . C 15' h F Boxelder ability in conditions that can affect the avail- fis o r r Piedmont a k e R Ellsworth p a S Air Force ability and quality of ground water in the S. Fork p i d Nemo Base

Rapid Cr C Creek r Blackhawk Cold S area. Maps presented in this report include pri ng 560560 Cre s ek k Box Elder For Rochford s the distribution of hydrogeologic units; depth adN o . For Rapid h k Ca 8080 R stle Castle Cr RAPID CITY to the top of the five formations that contain Beav e Rapid r k Creek C C ee Pactola r C r e re Reservoir 5,8005,800 major aquifers; thickness of the five forma- e e 900900 Creek k k Castle 1,3001V ,300 Deerfield ictoria Creek 1,5001,500 Reservoir Spring tions that contain major aquifers; potentio-

r 690690 o S. Fork 220220 44 C e Castl 1,4001,400 1,100 metric maps for the five major aquifers; Sheridan Rockerville Creek Creek Lake Hill City Mt. Rushmore saturated thickness of the Madison and National Keystone Memorial nyon Harney Minnelusa aquifers; water temperature in the Spring rd LIMESTONE PLATEAU a Iron Haywa C Peak n Mountain

o 2,7002,700 n x

y PENNINGTON CO x n o Battle

a y Sylvan Cr Spo Hermosa Madison aquifer; specific conductance in the n k C a a CUSTER CO Lake Iron ne C Creek Creek s e Madison, Minnelusa, and Inyan Kara aqui- l o Calamity Grace Bear B French Peak Creek CUSTER x Gulch Redbird e fers; hardness in the Inyan Kara aquifer; sul- Gillette idg Creek Cool 45' Jewel Cave CUSTER National fate concentrations in the Minnelusa aquifer; t Monumen Beaver STATE French Fairburn and radon concentrations in the Deadwood PARK

Canyon Creek aquifer. ighl H an Lame Canyon d C Creek o tt Wind Cave o Pringle n National Park w The total volume of recoverable water Creek o

o

WYOMING d

Wind Johnny stored in the major aquifers (including the

Cave SOUTH DAKOTA SOUTH Dewey Onyx Beaver Creek Cave Red Precambrian aquifer) within the study area is

k Creek

o RIVER Hell o Buffalo Gap r 30' B estimated as 256 million acre-feet. Although d Creek l

o

C FALL RIVER CO H on ot roo ny B k Ca HOT SPRINGS the volume of stored water is very large, Minnekahta Fall Oral water quality may not be suitable for all uses R CHEYENNE in some parts of the study area. Cascade Springs Water-level records are presented for Edgemont Horsehead selected observation wells to illustrate poten- Angostura o Creek Reservoir Creek 43 15' d oo tial fluctuations in water levels that can occur w n o tt o Igloo Creek C in the bedrock aquifers. In general, there is Provo very little indication of long-term water-level Hat 01020MILES declines from ground-water withdrawals in Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985 any of the bedrock aquifers in the Black Hills Rapid City, Office of City Engineer map, 1:18,000, 1996 01020KILOMETERS Universal Transverse Mercator projection, zone 13 area. However, dry wells or reduced pumping capacity could result during periods of Figure 35. Radon concentrations in the Deadwood aquifer (modified from Williamson and Carter, 2001). declining water levels. Most limitations for the use of ground water are related to aesthetic qualities associ- ated with hardness and high concentrations of chloride, sulfate, sodium, manganese, and iron. Water from the major bedrock aquifers generally is fresh and low in dissolved solids SUMMARY lower confining unit for a series of sedimen- concentrations in and near outcrop areas but tary aquifers. However, localized aquifers becomes progressively more saline with dis- The availability of ground-water occur in the igneous and metamorphic rocks tance from the outcrops. In the Minnelusa resources in the Black Hills area is influenced that make up the central crystalline core of aquifer, concentrations of dissolved sulfate by many factors including location, local the Black Hills and are referred to collec- vary markedly over short distances, influ- recharge and ground-water flow conditions, tively as the Precambrian aquifer. Water-table enced by a zone of active anhydrite dissolu- and structural features. Thus, the availability (unconfined) conditions generally occur in tion. Water from most minor aquifers of water is variable throughout the Black the Precambrian aquifer, and topography can generally has higher concentrations of dis- Hills area, and even when water is available, strongly control ground-water flow direc- solved sulfate than major aquifers because of it may not be suitable for various uses tions. The aquifer is considered to be con- larger influence from shale layers. depending on the water quality. tained in the area where the Precambrian-age Water from all aquifers, with the excep- rocks are exposed in the central core of the The major bedrock aquifers in the tions of the Pierre and Sundance aquifers, Black Hills. Black Hills area are the Deadwood, Madison, generally is suitable for irrigation in most Minnelusa, Minnekahta, and Inyan Kara Surrounding the central crystalline core locations. Very few health-related limitations aquifers. Minor bedrock aquifers occur in is a layered series of sedimentary rocks exist for ground water; most of these limita- other hydrogeologic units, including con- including limestones, sandstones, and shales tions are for radionuclides, such as radon and fining units, due to fracturing and inter- that are exposed in roughly concentric rings uranium, especially in the Deadwood and bedded permeable layers. around the uplifted flanks of the Black Hills. Inyan Kara aquifers. In addition, high con- The Precambrian-age basement rocks The more permeable of these sedimentary centrations of arsenic have been detected in a generally have low permeability and form the rocks—the Deadwood Formation, Madison few samples from the Minnelusa aquifer.

32 Ground-Water Resources in the Black Hills Area, South Dakota REFERENCES Driscoll, D.G., Hamade, G.R., and Kenner, S.J., Kyllonen, D.P., and Peter, K.D., 1987, Geohy- 2000, Summary of precipitation data for the drology and water quality of the Inyan Kara, Bartlett and West Engineers, Inc., 1998, Piedmont Black Hills area of South Dakota, water Minnelusa, and Madison aquifers of the Valley water quality assessment study— years 1931-98: U.S. Geological Survey northern Black Hills, South Dakota and Final report: Bismarck, N. Dak., Bartlett Open-File Report 00-329, 151 p. Wyoming, and Bear Lodge Mountains, and West Engineers, Inc. [variously paged]. Epstein, J.B., 2000, Gypsum karst and hydrologic Wyoming: U.S. Geological Survey Water- Callahan, M.A., Slimak, M.W., Gabel, N.W., evolution in the northern Black Hills, South Resources Investigations Report 86-4158, May, I.P., Fowler, C.F., Freed, J.R., Jennings, Dakota, in Strobel, M.L., and others, eds., 61 p. 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Dak., environmental fate of 129 priority pollutants, Dakota School of Mines and Technology South Dakota School of Mines and Technol- Volume I—Introduction and technical back- Bulletin No. 20, p. 73-79. ogy, unpublished Ph.D. dissertation, 59 p. ground, metals and inorganics, pesticides Galloway, JM., 2000, Digital map of generalized Long, A.J., and Putnam, L.D., 2002, Flow-system and PCBs: U.S. Environmental Protection thickness of the Madison Limestone and analysis of the Madison and Minnelusa aqui- Agency, Office of Water Planning and Stan- Englewood Formation, Black Hills, South fers in the Rapid City area, South Dakota— dards, Office of Water and Waste Manage- Dakota: U.S. Geological Survey data avail- Conceptual model: U.S. Geological Survey ment, EPA-440/4-79-029a [variously paged]. able on the World Wide Web, accessed Water-Resources Investigations Report 02- Carter, J.M., Driscoll, D.G., Williamson, J.E., and July 2, 2001, at URL http://water.usgs.gov/ 4185, 100 p. 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References 33 U.S. Environmental Protection Agency, 1994, U.S. Geological Survey, 1994, The hydrologic Williamson, J.E., and Carter, J.M., 2001, Water- Summary of EPA finalized National primary cycle: U.S. Geological Survey General Inter- quality characteristics in the Black Hills area, drinking water regulations: U.S. Environ- est Publication [pamphlet]. South Dakota: U.S. Geological Survey

mental Protection Agency Region VIII, Whalen, P.J., 1994, Source aquifers for Cascade Water-Resources Investigations Report 01- 7 p. Springs, Hot Springs, and Beaver Creek 4194, 196 p. ———1999, Proposed radon in drinking water Springs in the southern Black Hills of South Winter, T.C., Harvey, J.W., Franke, O.L., and rule: U.S. Environmental Protection Dakota: Rapid City, S. Dak., South Dakota Alley, W.M., 1998, Ground water and sur- Agency, Office of Water, EPA 815-F-99-006, School of Mines and Technology, unpub- face water—A single resource: U.S. Geolog- 6 p. lished M.S. thesis, 299 p. ical Survey Circular 1139, 79 p.

34 Ground-Water Resources in the Black Hills Area, South Dakota GLOSSARY Formation The fundamental unit in the local classification of rocks into geologic units based on similar characteristics in lithology, which is the Alluvium A general term for unconsolidated sedimentary accumulations description of rocks on the basis of such characteristics as color, mineralogic deposited by rivers or streams. It includes sediment deposited in river beds composition, and grain size. Formations may represent rocks deposited dur- and flood plains. ing short or long time intervals, may be composed of materials from several sources, and may include breaks in deposition. Formations typically are Anhydrite A calcium sulfate mineral (CaSO ) that alters readily to gypsum. 4 named after geographic localities where they were first studied or described. Anticline A fold in which the strata dip away from the axis. After erosion, Fracture A crack in a rock. Also includes joints and faults. the oldest rocks are exposed in the central core of the fold. Fresh water Water that has a dissolved solids concentrations of less than Aquifer An underground body of porous materials, such as sand, gravel, or 1,000 milligrams per liter. fractured rock, filled with water and capable of supplying useful quantities of water to a well or spring. Geologic time scale An arbitrary chronologic arrangement of geologic events, commonly presented in a chart form with the oldest event and time Artesian aquifer An aquifer that contains water that would rise above the unit at the bottom and the youngest at the top. top of the aquifer in a penetrating well; also confined aquifer. Ground water Water beneath the land surface in the saturated zone. Artesian well A well in which the water will rise above the top of the aquifer. When the water level is above land surface, water will flow from the Ground-water level The level of the water table in an unconfined aquifer well. or of the potentiometric surface in a confined aquifer. Axial plane With reference to folds, such as anticlines and synclines, an Group A geologic classification consisting of two or more formations. imaginary plane that intersects the crest or trough of a fold. ² Gypsum The mineral form of hydrated calcium sulfate, CaSO4 2H2O. Basal Located at the bottom of a geologic unit. Hogback A steep, elongate ridge; commonly protected from erosion by a Bedrock aquifer An aquifer composed of consolidated material such as steeply dipping resistant stratum. limestone, dolomite, sandstone, siltstone, shale, or fractured crystalline rock. Hydraulic connection Exists when changes in hydraulic head in adjacent Carbonate rocks Rocks consisting mainly of carbonate minerals, which aquifers or surface-water bodies influence each other. -2 contain the carbonate radical (CO3 ) combined with other elements. Exam- ples are limestone and dolomite. Hydraulic gradient The rate of change in total head per unit of distance of flow in a given direction. Water will flow from higher hydraulic head to Cenozoic The most recent of the four eras into which geologic time is lower hydraulic head. divided. It extends from the end of the Mesozoic Era to the present. Hydraulic head In an aquifer, the altitude to which water will rise in a prop- Clay An earthy, extremely fine-grained sediment or soft rock composed erly constructed well. This is the altitude of the water table in an unconfined primarily of clay-sized or colloidal particles, having high plasticity and a aquifer or of the potentiometric surface in a confined aquifer. considerable content of clay minerals. Hydrogeology Factors that deal with geologic influences on water. Colluvium A general term applied to unconsolidated material deposited by rainwash or slow continuous downslope creep, usually collecting at the base Hydrograph A graph showing flow rates or water levels with respect to of hillsides. time. A stream hydrograph commonly shows rate of flow; a well hydrograph commonly shows water level. Concentration The amount of a constituent present in a given volume of sample. Usually expressed as milligrams per liter or micrograms per liter for Igneous rocks Rocks that solidified from molten or partly molten material, a water sample. such as magma. Granite is an example of an igneous rock. Confined Said of ground water that is under pressure greater than that of the Infiltration Movement of water from the land surface into the soil or porous atmosphere. When an aquifer is completely filled with water (fully saturated) rock. and is overlain by a confining unit, the water can be confined under pressure. Intrusion The process of emplacement of magma in pre-existing rock. Confined aquifer An aquifer that contains water that would rise above the Isotope One of two or more species of the same chemical element that dif- top of the aquifer in a penetrating well; also artesian aquifer. See figure 1B. fer from one another by having a different number of neutrons in the nucleus. Confining unit A relatively low permeability geologic unit that impedes the The isotopes of an element have slightly different physical and chemical vertical movement of water. properties due to their mass difference. Conglomerate A coarse-grained sedimentary rock composed of rounded Karst A type of topography that is formed over limestone, dolomite, or fragments of pebbles, cobbles, or boulders cemented into a solid mass. gypsum by dissolution. It is characterized by sinkholes, caves, and under- ground drainage. Constituent A chemical substance in water that can be measured by analyt- ical methods. Laminated Said of a rock containing very thin layers; platy. Cross section A diagram or drawing that shows features transected by a Limestone A sedimentary rock consisting mostly of calcium carbonate, given vertical plane. See figure 6. CaCO3, primarily in the form of the mineral calcite. Crystalline rock Igneous or metamorphic rock. Massive Said of rocks that occur in very thick beds that are uniform in structure and composition throughout. Dip The slope of a tilted layer of rock. Maximum Contaminant Level (MCL) Maximum permissible level of a con- Dissolution Process by which minerals and rock materials are dissolved by taminant in water that is delivered to any user of a public water system. a fluid. MCL’s are enforceable standards established by the U.S. Environmental Protection Agency. Dissolved solids The total of all dissolved mineral constituents, usually expressed in milligrams per liter (mg/L). The dissolved solids concentration Mean The arithmetic average of a series of values. commonly is called the water’s salinity and is classified as follows: fresh, 0-1,000 mg/L; slightly saline, 1,000-3,000 mg/L; moderately saline, 3,000- Median The value of the middle number in a set of data arranged in rank 10,000 mg/L; very saline, 10,000-35,000 mg/L; and briny, more than 35,000 order. The 50th percentile. mg/L. Mesozoic The era of geologic time from the end of the Paleozoic Era to the Dolomite A sedimentary rock composed primarily of calcium-magnesium beginning of the Cenozoic Era. carbonate, CaMg(CO3)2. Metamorphic rock Derived from pre-existing rocks in response to changes Dome An uplift that is circular or elliptical in map view, with beds dipping to temperature, pressure, or stress that result in changes in the mineralogy, away in all directions from a central area. chemistry, or structure of the rock. Examples of metamorphic rocks are slate and schist. Effective porosity The porosity consisting of interconnected voids. Monocline A step-like bend or fold in otherwise horizontal or gently Fault A surface along which a rock body has broken and been displaced. dipping beds. Fold A bend or flexure in a rock. Nutrients Nitrogen and phosphorus, which are essential to plant growth.

Glossary 35 Observation well A well constructed for collection of hydrologic data, Secondary Maximum Contaminant Level (SMCL) Maximum level estab- such as water levels and water quality. lished by the U.S. Environmental Protection Agency for contaminants that can adversely affect the odor or appearance of water and may result in dis- Outcrop That part of a geologic formation that is exposed at the land continuation of use of the water. SMCL’s are nonenforceable, generally non- surface. health-based standards that are related to the aesthetics of water use. Paleozoic The era of geologic time from the end of the Precambrian Era to Secondary permeability The permeability developed in a rock after its the beginning of the Mesozoic Era. deposition, through such processes as weathering and fracturing. Perched ground water Unconfined ground water separated from an under- Secondary porosity The porosity developed in a rock after its deposition, lying main body of ground water by an unsaturated zone. through such processes as dissolution or fracturing. Permeability The capacity of a porous rock, sediment, or soil for transmit- Sedimentary rock Rocks resulting from the consolidation of loose sedi- ting a fluid. ment that has accumulated in layers. Examples of sedimentary rocks are sandstone, siltstone, limestone, and shale. Porosity The percentage of the soil or rock volume that is occupied by pore space, void of material; defined by the ratio of voids to the total volume of a Semiconfining unit Unit that may transmit some water to and from adja- specimen. cent aquifers. Potentiometric surface A surface representing the hydraulic head of Shale A fine-grained sedimentary rock, formed by the consolidation of ground water; represented by the water-table altitude in an unconfined aqui- clay, silt, or mud. fer or by the altitude to which water will rise in a properly constructed well Sill A tabular igneous intrusion that parallels the bedding of the surround- in a confined aquifer. ing sedimentary or metamorphic rock. Precambrian The oldest geologic time period, which occurred before the Solution opening An opening in a rock material resulting from the disso- beginning of the Paleozoic Era. The Precambrian Era constitutes about lution of calcium carbonate in limestone or chalk. 90 percent of all geologic time. Spring Any natural discharge of water from rock or soil onto the land Public water supply Water supply provided to the public; defined in South surface or into a surface-water body. Dakota as having at least 15 service connections or regularly serving at least Stratigraphic column The vertical (or chronological) sequence of rock 25 individuals daily for at least 60 days out of the year. units portrayed in a column from oldest (bottom) to youngest (top). See Radioactive decay Spontaneous emission of particles (alpha or beta) and figure 4. gamma rays from the nucleus of an unstable nuclide. The resulting product Structural feature A feature produced by deformation or displacement of nucleus may be stable or unstable, in which case decay continues until a the rocks, such as a fold or fault. stable nuclide is formed. Surface water Water on the Earth’s surface. Radioactivity The emission of energetic particles and/or radiation during radioactive decay. Syncline A fold in which the strata dip toward the axis. After erosion, the youngest beds are exposed in the central core of the fold. Radionuclide A radioactive nuclide. (A nuclide is a species of atoms char- acterized by the number of neutrons and protons in its nucleus.) Unconfined Said of ground water that has a water table; the water is not confined under pressure. Recharge The process involved whereby infiltration reaches the saturated Unconfined aquifer An aquifer in which the water table is exposed to the zone. Also the amount of water added. atmosphere through openings in the overlying materials. Residence time In ground water, the length of time water remains under- Unconsolidated aquifer An aquifer composed of material that is loosely ground before it is extracted or discharged. arranged or whose particles are not cemented together, such as sands and Saline water Salty water. Classified by the dissolved solids concentration gravels. in water. Unsaturated The condition in which the pores of a material contain at least Sandstone A sedimentary rock composed of abundant rounded or angular some air. fragments of sand set in a fine-grained matrix (silt or clay) and more or less Water table The top of the water surface in the saturated zone of an uncon- firmly united by a cementing material. fined aquifer. Saturated The condition in which the pores of a material are filled with Water year The 12-month period, October 1 through September 30, that is water. designated by the calendar year in which it ends.

36 Ground-Water Resources in the Black Hills Area, South Dakota