Montana Bureau of Mines and Geology Montana Ground-Water Assessment Atlas 3, Part B, Map 5 A Department of Montana Tech of The University of Montana Open-File Version 2006

Characterization of the Judith River Aquifer A A' in Treasure and Yellowstone Counties, 4,200 4,200 Middle Yellowstone River Area, Montana 4,000 4,000

3,800 By John L. Olson and Rye E. Svingen Kl Kjr 3,800 Qa 3,600 Kb 3,600 Kjr brown sandstone (Lopez, 2000). The Judith River Kcl Atlas organization 3,400 3,400 Formation is underlain by the Claggett Shale, which Location map The Montana Ground-Water Assessment Atlas for the The Middle Yellowstone River Area consists of Geologic cross sections Kjr Middle Yellowstone River Area (Atlas 3) consists of a consists of 100–300 ft of sandy shale. The Claggett Treasure and Yellowstone Counties exclusive Shale forms the base of the aquifer. Where the Judith Three geologic cross sections were constructed through 3,200 3,200 descriptive overview (Part A) and 7 hydrogeologic of the Crow Indian Reservation. Map areas of Kcl the Judith River aquifer along lines A–A', B–B', and C–C'. River Yellowstone River Formation dips into the subsurface, it is overlain maps (Part B). This map is intended to be a stand-alone the Judith River aquifer were selected to include The locations of the cross-section lines are displayed on Ke by the dark gray marine Bearpaw Shale, which can be the areas where the aquifer is present and is less 3,000 Kcl 3,000 document that describes a single hydrogeologic unit Hysham the Drilling depths map. The cross sections are based on up to 800-ft-thick. Area than 2,000 ft below the ground surface. (the Judith River aquifer) within the area (see Location interpretations of water well logs, oil well logs, and geologic above sea level) altitude (ft map, right). To obtain a more integrated understanding Yellowstone mapping (Lopez, 2000). The cross sections show 2,800 Ke 2,800 Two primary structural features influence the occurrence County Treasure stratigraphic position and thicknesses of relevant formations. Ktc of the area’s hydrogeology, see Part A and related Part County B maps. and depth of the Judith River aquifer in the Middle Billings Area Yellowstone River area: the Bull Mountains Basin and 2,600 Ktc Kc 2,600 Ke the Lake Basin fault zone. The Bull Mountains Basin Cross-section explanation Kc Introduction is a broad regional feature centered just north of 2,400 2,400 The Judith River aquifer is a source of domestic and Geologic units 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 31 36 37 38 39 40 41 42 43 44 45 46 47 48 Yellowstone County (Dobbin and Erdmann, 1955). Hysham stock water (see Well use) in west-central Yellowstone Bedrock formations dip gently (at 2°–4°) towards the Qa Alluvial deposits (Quaternary) Scale in miles # County and northern and central Treasure County and # basin center. As a result, the Judith River aquifer is # Kl Lance Formation (Upper Cretaceous) # # provides water to about 580 wells. Most of these wells # # encountered at depths of greater than 1,000 ft in the # # # Kb ## Bearpaw Shale (Upper Cretaceous) 2% # have been completed where the Judith River Formation northern portion of Yellowstone County (see Drilling # 4% Yellowstone Kjr Judith River Formation (Upper Cretaceous) crops out north and east of Billings (see Distribution depths map). The dip of the formation into the subsurface Treasure # County # of wells). # County is shown in Cross section B–B'. Minor domal structures # Kcl 7% Domestic ## Claggett Shale (Upper Cretaceous) # ## # # # # # ## cause the Judith River to be exposed in small areas near # # # # # # # # # # # # ## # ## # # # Ke # # # # Eagle Sandstone (Upper Cretaceous) # # # BB' Stockwater # # # # ## # Broadview (Broadview dome) and in northeastern # # ## # Geologic setting # # # # # Ktc Telegraph Creek Formation (Upper Cretaceous) The Judith River aquifer is composed of water-saturated Treasure County (Ingomar dome). The dip of the aquifer 22% Irrigation 3,400 3,400 Judith River Qal off the domal feature in Treasure County is shown in 65% Billings Kc Colorado Group (Upper Cretaceous) sandstone layers in the Judith River Formation. This Unused Formation CC' formation is part of an approximately 4,000-ft-thick Cross section C–C'. outcrop Fault 3,200 3,200 2,800 2,800 Other sequence of Cretaceous marine sedimentary rocks. The Laurel relative positions and thicknesses of the Cretaceous The Lake Basin fault zone consists of a roughly 6-mile- Horizontal Scale: 1:250,000 formations in the Middle Yellowstone River Area are wide band of northeast–southwest-trending, high-angle Vertical Scale: 1:6,250 3,000 3,000 2,600 2,600 shown below (see Cretaceous Stratigraphy). faults. Individual faults are generally oriented Vertical Exaggeration: 40X Qal

Well use Distribution of wells River Yellowstone perpendicular to the regional fold axes. Displacements 2,800 Kb 2,800 Most of 580 recorded wells in the Judith River Most wells completed in the Judith River 2,400 Kb 2,400 of as much as 250 ft have been reported (Hancock, The Judith River Formation crops out along a 2–6- aquifer provide domestic water to individual aquifer are located in the Judith River Kjr mile-wide east–west-trending band generally north of 1919). The faults are a significant feature of the aquifer 2,600 2,600 residences; others are used for stockwater; a Formation outcrop area, north of Billings. 2,200 2,200 Billings. South of these outcrops the formation has been because they offset the sandstone beds, and in some few are used for irrigation and other purposes. Kjr Kcl

removed by erosion. The Judith River Formation is places truncate the entire aquifer. Displacements and above sea level) altitude (ft 2,400 2,400 2,000 2,000 250–350-ft-thick and consists of interbedded brownish- aquifer truncation are shown in Cross section A–A'. Ktc Kcl altitude (ft above sea level) altitude (ft Ke gray sandy shale and light brown to pale yellowish Ke 2,200 Kc 2,200 1,800 Kc 1,800

012345678910111213 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Scale in miles Scale in miles

Cretaceous stratigraphy R23E Explanation for the Judith River The Cretaceous Period occurred 135–65 million years ago. During much of this time, the area of what is now Formation maps Yellowstone and Treasure Counties was in or near a large 3 , 8 inland sea. The rocks deposited during the Cretaceous are 0 0 3 a record of multiple cycles of the rise and fall of this sea. ,9 Roads 0 Broadview 0 Shale and claystone rocks were deposited in deeper water Streams environments during sea level high stands. Sandstone was T4N 4,012 Judith River Formation and potentiometric surface map of the Billings area Judith River Formation and potentiometric surface Faults # 4 deposited in shore or nearshore environments during sea 108° 45' ,0 R24E 0 + level low stands. The total sequence of Cretaceous rocks Township boundaries 0 map of the Hysham area 4 ,1 30' in the area is about 4,000-ft-thick. The Judith River Section lines 0 # ° 0 3,950 R25E R26E R27E 108 Formation occurs in about the upper third of this sequence 3,884 + and consists of 100–400 ft of sandstone interlayered with # Ground-water altitude measurement points and # some shale. These sandstone layers constitute the Judith 3,950 posted data (ft above mean sea level 3 36 31 , 7 36 31 36 31 36 31 [AMSL]) 3 0 River aquifer. The Judith River Formation is underlain by 0 16 , 8 R36E 3,90 16 16 16 0 107°15' 108° 15' R28E R29E R30E R34E R35E

the Claggett Shale and overlain by the Bearpaw Shale. The 0 3,867 Bull Mountains + + 0 #

Ground-water altitude contours # 0

0 162

2,810 9

16 , ,9 Claggett Shale and Bearpaw Shale are generally non-water- 2 basin 0 3,300 Contour values (ft AMSL, interval = 100 ft) 0 bearing. # 3,810 Ground-water flow direction # 3,789 Ingomar dome Potentiometric surface Judith River Formation outcrop Broadview 3 3 T3N , , 7 1 3,000

0 0 This map shows the altitude to which ground water in a dome 0 Judith River Formation present in subsurface 0 well will rise. Ground-water flow is perpendicular to the 46° 00' + 3,200 2,752 ## # T8N potentiometric contours and flows from the highest to the 3, 3,864, 3,733 300 # er lowest potentiometric altitude (see flow arrows on map). 0 v 0 # i 0 R , # # The potentiometric surface map was constructed from static 4 3,753 3 2,992 e , 2,868 3, 4 n 80 0 o water-level altitudes measured in 90 inventoried wells. 0 3,772 0 t # 3 s , 3,762 5 #3,099 w 0 o Reported water levels in non-inventoried wells were also 0 # ll 36 31 36 31 e 36 31 used to qualitatively assist in contouring ground-water 36 31 Y 16 36 31 36 31 36 31 # 16 R37E 3,023 16 0 3 3 16 0 , , 16 8 altitudes. 16 7 16 6 , 36 0 0 2 0 0 36 31 # 3,815 36 31 16 Cretaceous stratigraphy for the Billings area # 16 3,773 3,628 16 3,8143 The ground-water altitude data demonstrate two types of ,8 # 0 0 3793 ## 3,465 3 3 flow systems in the aquifer, local systems and a regional 3,805 # ,4 ,400 # # 00 3,047 system. Local flow-systems occur under Judith River Lance Formation 3,80 0 3,80 0 # 3, # 3,126 outcrops, and the flow directions are primarily influenced 9 3,856 3 3 0 ,8 , # 0 00 6 Bearpaw Shale 4 # 0 3 # ,0 3,827 0 3, ,2 by topography and surface drainage. Recharge is from 00 40 0 # 0 3 0 # , # 3,000 4 # 3,068 100 infiltration of local precipitation and ground-water flow is Judith River T2N # 0 3 3,066 3, T7N Judith River Formation 3,416 0 , 3,907 ,000 30 3 # 4 3,589 0 ,30 2,768 directed towards the nearest drainage. The ground-water aquifer 3 ,400 0 , 3 3,395 Claggett Shale 8 # # 0 0 3,438 # 0 0 0 3,528 0 0 gradient in the local flow systems typically ranges from 0 # # 3,002 0 ,7 4 # , ,1 2 , 4 4 3 3,200 2,679 Eagle Sandstone 10 ,0 0 4018 0 0 3,528 3,343 0 # 3,050 # 1–10 percent. The Lake Basin fault zone is shown to have 0 0 0 # 8 , 4 2,790 Telegraph Creek Formation , 200 3 3, 3,109 0 # 4,130 3 3,300 20 a significant influence on ground-water flow in outcrop Lake Basin fault zone # # 3, ## 3,145 0 Niobrara Shale # 3,014 30 and in the subsurface. Ground-water altitudes are observed 0 3, 00 # 00 0 ,10 0 ,1 4,053 4,1 ,20 3 3,30 36 4 # 4,131 0 # 3 36 31 00 to change significantly across faults. In some locations, 00 3 36 31 36 31 # 2,6 , 36 31 ,3 1 Aquifer Carlile Shale 36 31 4 36 31 0 # 0 16 0 1 6 16 0 2,750 36 the aquifer can become thin or absent due to fault 4 16 1 6 16 00 , 36 31 Greenhorn Formation 3,385 1 3 Non-aquifer 000 3, 00 36 31 16 displacement. The fault displacements form discontinuities 4, 3,4 16 and gaps in the aquifer and likely act as barriers to ground- Belle Fourche Shale 3,358 3,187 16 4 #0# 2,615 Mowry Shale #4,075 ,10 0 0 4,152 0 3,50 ,500 # water flow. Consequently, ground-water flow in the fault # 3,20 3,468 3 1,000 ##3,956 # 0 3 00 Colorado Group 3,473 0 6 zone typically runs parallel to the faults. Thermopolis Shale and 0 ,600 # 3, # # 3 0 , 4 # 2,711 3 , Fall River Sandstone #3 3,648 Hysham Scale (ft) # #4,115 3,108 2,712 Where the Judith River aquifer is deeply buried and far Kootenai Formation 3,700 3,700 from recharge sources, ground-water flow adopts a regional 0 Pryor Conglomerate T1N pattern. The ground-water flow becomes more sluggish 3,800 Member # 3,783 T6N and the gradients flatten to about 0.1–1 percent. North of 500 # 3, 3,607 + 45° 15' Billings the flow is directed eastward. East of Billings and Average formation thicknesses from Lopez (2000). 3,90 # 3,611 # 0 # 3,824 45° 15' + 3,718 near Hysham the ground-water flow is generally directed # 2,700 0 3,733 towards the Yellowstone River valley. A similar ground- 0 ,60 0 3

7 Billings , 3 36 water flow pattern towards the river valley is evident in 36 31 36 31 # 36 31 36 31 + 36 31 36 31 6 Miles 2,705 regional flow in the overlying Eagle aquifer (Olson and + 36 31 + 36 31 Reiten, 2003). + 16 16

# 107° 15' 3,880 T1S 2 1 02 4 6 108° 15' 108° 30' 108° 45' T5N Scale: 1:175,000 45° 45' + + 45° 45' Projection: Montana State Plane 1983

R23E

Broadview T4N Estimated drilling depths in the Billings area Estimated drilling depths in the Hysham area R24E Estimated drilling depths 108° 45' + The purpose of this map is to indicate the likely depth to Explanation for the estimated

which a well must be drilled to be completed in the Judith drilling depths maps R25E108° 30' R26E R27E River aquifer. The depths presented on the map include + depth to the aquifer and adequate penetration into the Probable 36 31 36 31 15'

36 31 15' aquifer. This map was based on reported well depths and 36 31 ° 16 ° well depth 16 16 16 R36E 107 reported lithologic and well construction data from water 108 R28E R29E R30E R34E R35E C (in ft) Map features + + well logs and oil well logs. > 1,000 Bull Mountains 16 Basin 16 >1000 Roads Broadview < 100 In general, wells located in stream valleys and draws within 700–1000 the outcrop area can be completed at depths of less than Streams A dome 700–1,000 100 ft. On ridges and uplands in the outcrop area wells 500–700 Faults T3N B' Ingomar dome must be completed at depths of 100–300 ft. Drilling depths 300–500 Township boundaries 100–200 can also be significantly influenced by fault displacement. 200–300 Section lines 46° 00'+ North of the outcrops, the aquifer dips into the subsurface, 500–700 T8N 100–200 Line of geologic 700–1,000 and within 1 or 2 miles drilling depths can be greater than ver 300–500 500 ft. <100 cross section Ri ne 300–500 to 200–300 ws 200–300 o 36 31 36 31 ll 36 31 36 31 16 36 31 36 31 e 36 31 16 Y 16 R37E Well statistics 16 16 16 16 36 36 31 100–200 36 31 16 Well statistics were obtained by evaluating information 300–500 16 from driller’s logs for 302 wells. The percentile indicates 16 500–700 the percentage of sample data that is less than the given < 100 200–300 value. Half of the wells will have values between the 75th Specific Reported Total and 25th percentile, and 90% of the data population will capacity yield depth 500–700 have values between the 5th and 95th percentile. The 50th percentile is the population median. (gpm/ft) (gpm) (ft) T2N < 100 T7N The specific capacity of a well is the yield per foot of 95% 1.6 30 350 700–1,000 water-level drawdown and is calculated by dividing the 75% 0.4 15 190 Lake Basin fault zone drawdown by the pumping rate. Specific capacity is a measure of the productivity of a well and is influenced by 36 31 36 both well construction and aquifer properties. The larger 36 31 36 31 36 31 1 36 31 36 31 16 16 the specific capacity value the more productive the well 16 36 50% 0.2 10 150 16 1 6 16 > 1,000 36 31 100–200 36 31 16 is. The specific capacity of most Judith River aquifer wells 16 is relatively low. Consequently, large drawdowns may be 16 required to obtain a sufficient yield. B 25% 0.06 5 108 Hysham About 50 percent of reported yields for the aquifer were between 5–15 gallons per minute (gpm), which is adequate Population percentile 5% 0.01 1 63 for most domestic and stockwater use, but insufficient for T1N irrigation, industrial, or municipal uses. T6N

+45° 15' 45° 15' + Billings

36 36 31 36 31 36 31 36 31 A' 36 31 + 36 31 6 Miles + 36 31 + 36 31 + C' 16 T1S 16 2 1 02 4 6 107° 15' 108° 15' 108° 30’ 108° 45' T5N

45° 45’ Scale: 1:175,000 45° 45’ + + Projection: Montana State Plane 1983

R23E Distribution of dissolved Type 3 Still further from recharge areas, the ground water evolves constituents to a type 3, NaCl water (green diagrams). Dissolved- The map shows dissolved-constituent concentrations that constituent concentrations range from 2,000 to more than will likely be encountered in the Judith River aquifer. The 4,000 mg/L. The primary change from a type 2 to a type Broadview map displays the distribution of the sum of dissolved 3 water occurs through the removal of sulfate and the + constituents (Ca + Mg + Na + K + HCO + SO , + Cl; accumulation of chloride. Sulfate is removed through T4N Concentrations of dissolved constituents in ground water in the Billings area 3, 4 + colored areas) and the relative concentrations in microbial activity in which organic carbon in the aquifer + 108° 45' R24E Concentrations of dissolved constituents milliequivalents per liter (meq/L) of individual constituents (probably from carbonaceous shale) is oxidized to bicarbonate and sulfate is reduced to hydrogen sulfide. In + in ground water in the Hysham area (colored diagrams). This map was developed from all 108° 30' R25E + R26E R27E available water-quality data collected from the Judith River the presence of dissolved metals, metal sulfides form and + aquifer in the Middle Yellowstone River area. precipitate (Drever, 1982). The most common metal sulfide

is pyrite (iron sulfide). If the pH is less than 7, hydrogen 36 31 36 31 36 31 36 31

16 107° 15' Typically, water does not become too salty to drink until sulfide gas can form, giving the water a rotten-egg smell. 16 16 16 + R36E

108° 15' R28E R29E R30E R34E R35E the sum of dissolved constituents exceeds about 2,000 + Bull Mountains + + 16 milligrams per liter (mg/L), and is unsuitable for most uses Type 3 water is encountered where the aquifer is deeply Broadview>4,000 Basin 16 above concentrations of 3,000 mg/L. The ranges and medians buried and ground-water flow becomes sluggish. Because dome+ of individual dissolved constituents are compared to very little flushing occurs, residual highly soluble salts + appropriate health-based concentration limits in the Summary (such as sodium chloride) are still present in the marine Ingomar dome of water-quality parameters table. deposits. As ground water moves through the deep aquifer, T3N chloride accumulates and becomes the dominant anion. 46° 00' + 2,000–3,000 Ground-water geochemical evolution + + T8N + r Dissolved constituents in ground water are a result of the + ive initial chemistry of the recharge water and subsequent + e R on interactions of that water with soils and aquifer materials. + st Explanation for the dissolved 3,000–4,000 + w As the water migrates from the recharge area to the deeper llo 36 31 36 31 e 36 31 constituents maps 36 31 16 aquifer, its chemistry evolves. Three water-quality types 36 31 36 31 + Y + 36 31 16 16 >4,000 R37E 16 16 have been identified in the aquifer based on composition, 16 16 36 >4,000 36 31 Dissolved + 36 31 16 sum of dissolved constituents, and the ground-water setting. Map features + 2,000–3,000 16 16 constituents (mg/L) + Roads ++ + + Type 1 less than 2,000 Streams + Type 1 water (blue diagrams) contains relatively low + + 2,000–3,000 + concentrations of dissolved constituents (500–2,000 mg/L). Faults + + + + + The water type ranges from Ca-Mg-Na-HCO -SO to Na- 3,000–4,000 Townships + + 3 4 T2N + <2,000 + T7N Ca-Mg-SO4-HCO3 . This water is found in the outcrop area more than 4,000 Section lines and the chemistry is derived primarily from water-soil- + + + + + + 3,000–4,000 3,000–4,000 mineral reactions as precipitation infiltrates the aquifer. + + + Stiff diagrams showing abundance + + + of common ions ++ Lake Basin fault zone + Type 2 + + 36 31 36 + 36 31 As distance and depth from the recharge area increase, the 36 31 36 31 1 Sample location 36 31 36 31 + 16 16 16 36 water becomes more mineralized with increased proportions Sodium 16 1 6 16 36 31 Chloride + 36 31 16 of sodium and sulfate, and becomes type 2, Na-SO water Calcium <2,000 16 4 # Bicarbonate 16 (red diagrams). Type 2 waters are characterized by very Magnesium Sulfate + ++ + high concentrations (more than 3,000 mg/L) of dissolved 100 75 50 25 0 25 50 75 100 ++ + + constituents, and are typically found where the Judith River Cations (meq/L) Anions (meq/L) + + + + + Hysham Formation dips beneath the Bearpaw Shale. The increase + meq/L: milliequivalents per liter + in the percentage of sodium in the water occurs through mg/L: milligrams per liter cation exchange, in which dissolved calcium and magnesium T1N <2,000 <2,000 are exchanged with sodium from clay minerals. Sulfate is + 2,000–3,000 T6N + likely derived from the weathering of sulfide minerals in + Type 1 water + + + 45° 15' the relatively pyritic marine Cretaceous formations (Dean + 45°15' + and Arthur, 1989). Weathering of gypsum and anhydrite + Type 2 water + can also contribute sulfate concentrations. + Type 3 water Billings 36 Miles 36 31 36 31 + 36 31 36 31 36 31 + 36 31 6 + 36 31 + 36 31 + 16 2 1 02 4 6 16 + T1S 107° 15' 108°15' 108° 30' 108° 45' Scale: 1:175,000 T5N Projection: Montana State Plane 1983 45°45' + + 45°45'

Summary of water-quality parameters in the Judith River aquifer

Number Population Percentile MCL SMCL Number Population Percentile MCL SMCL Common ions of samples 5% 50% 95% Trace elements of samples 5% 50% 95% 80 80 (mg/L) (µg/L) %Ca+Mg Bicarbonate (HCO3) 52 286 603 1,115 - - Aluminum (Al) 28 <20 <20 124 - - 60 60 Calcium (Ca) 52 2.9 16.4 197 - - Antimony (Sb) 28 <2 <2 10 6 - +Cl 4 Carbonate (CO3) 52 <1 <151 - - - Arsenic (As) 28 <1 3 5 50 - Chloride (Cl) 53 12 48 948 - 250 Barium (Ba) 30 6 26 222 2,000 - 40 40 Fluoride (F) 21 0.3 1.5 5.0 4 - Beryllium (Be) 28 <1 <1 10 4 - %SO Iron (Fe) 51 0.002 0.03 2.7 - 0.3 Boron (B) 30 188 797 3,120 - - Potassium (K) 39 1.3 2.6 5.2 - - Bromide (Br) 28 105 250 1,250 - - 20 20 Magnesium (Mg) 52 0.8 9.7 115 - - Cadmium (Cd) 28 <2 <2 8 5 - Conclusions Data sources References Manganese (Mn) 39 <0.002 0.01 0.09 - 0.05 Cobalt (Co) 28 <2 <2 10 - 1,300 Dean, W.E., and Arthur, M.A., 1989, Iron-sulfur-carbon Nitrate+Nitrite as N 50 <0.01 0.3 9.8 10 - Chromium (Cr) 28 2 5 22 - - Explanation The Judith River aquifer is a source of domestic water in east- Geographic: relationships in organic-carbon-rich sequences Orthophosphate as (PO4) 28 0.025 0.3 2.0 1 - Copper (Cu) 28 <5 7 18 1,300 - Ground-water geochemistry I: Cretaceous western interior seaway: American Journal Sodium (Na) 52 89 677 1,674 - 250 Lead (Pb) 28 <2 <2 10 15 - central Yellowstone County and north-central Treasure County. It Digital coverages of streams and public land-survey grids were Silica (SiO ) 49 7.6 10.3 19.5 - - Lithium (Li) 39 <25 130 213 - - 20 20 3 Type 1 is relatively accessible (less than 300-ft-deep) in areas near the obtained from the Montana Natural Resource Information System of Science, v. 289, p. 708–743. 2 Type 2 Sulfate (SO4) 53 0.4 411 2,583 - 200 Molybdenum (Mo) 28 <10 <10 57 - - outcrop. However, the aquifer plunges to depths greater than 1,000 (NRIS). Geologic coverages were obtained through the Montana Dobbin, C.E., and Erdmann, C.E., 1955, Structure contour map %Na+K +CO Type 3 Nickel (Ni) 29 <2 5 10 - - 40 40 3 ft north of the Lake Basin fault zone. Bureau of Mines and Geology’s Statemap program which was of the Montana Plains: U.S. Geological Survey Oil Other Constituents Selenium (Se) 35 <2 2.9 56 50 - 5,000 Scale of radii proportional supported by partial funding from the U.S. Geological Survey. and Gas Investigations Map OM 178A, scale 1:500,000. Field pH 23 7.2 8.1 9.5 - 6.5–8.5 Silver (Ag) 28 <1 1 5 - 100 to dissolved constituent Water quality in most of the aquifer is marginal for many uses and 60 60 Drever, J.I., 1982, The geochemistry of natural waters: Prentice- Lab pH 42 7.3 8.1 8.8 - 6.5–8.5 Strontium (Sr) 30 232 1,310 3,533 - - %HCO concentration (mg/L) may require treatment. In areas where the aquifer is overlain by Point Data: Field SC (µmhos/cm) 23 748 3,630 4,865 - - Thallium (Tl) 12 <5 13 25 - - 10,000 the Bearpaw Shale, the aquifer contains highly mineralized water Well-location and water-level altitude data were obtained by Ground- Hall, Inc., Englewood Cliffs, NJ, 388 p. Lab SC (µmhos/cm) 40 845 2,800 6,080 - - Titanium (Ti) 28 <10 <10 <100 - - 80 80 that is not suitable for most uses. Well yields in the Judith River Water Characterization Program staff. Measuring-point altitudes Hancock, E.T., 1919, Geology and oil and gas prospects of the Water temp (°C) 23 11 13.2 19.5 - - Vanadium (V) 28 <5 <50 <50 - - aquifer are generally acceptable for single-dwelling domestic use were obtained from 1:24,000-scale topographic maps. All point Lake Basin field, Montana: U.S. Geological Survey Bulletin DC (mg/L) 21 401 1779 6,728 - - Zinc (Zn) 28 <2 5 25 - 5,000 691-D, p. 101–147, scale 1:125,000. TDS (mg/L) 21 57 579 2,760 - 500 Zirconium (Zr) 28 <2 <25 <25 - - or stock wells, but insufficient for most irrigation, industrial, or data presented on this map are available through the Ground-Water Uranium (U) 11 <5 <5 <5 - - municipal uses. Information Center (GWIC) at http:\\ mbmggwic.mtech.edu. Lopez, D.A., 2000, Geologic map of the Billings 30' x 60' quadrangle, DC= sum of dissolved constituents Proportions of common ions TDS= total dissolved solids Montana: Montana Bureau of Mines and Geology Geologic The plot above shows the relative proportion of common ion constituents in terms Acknowledgments Map 59, scale 1:100,000. Water-quality constituent ranges of milliequivalents per liter. The size of the dot is proportional to the sum of Olson, J.L., and Reiten J.C., 2003, Characterization of the Eagle Ranges of dissolved constituent concentrations are provided in the table Summary of water-quality parameters in the Judith River aquifer. The concentrations dissolved-constituents concentration and the color represents the water-quality type Well owners who allowed collection of the data necessary for this aquifer, middle Yellowstone River area, Montana: Montana are compared to EPA maximum contaminant levels (MCLs) and secondary maximum contaminant levels (SMCLs). Water whose dissolved constituents exceed (blue is type 1, red is type 2, green is type 3). Descriptions of the water-quality types map and the people who collected the data are gratefully Bureau of Mines and Geology Montana Ground-Water Atlas an MCL may need treatment to prevent adverse human health effects. Parameters that exceed an SMCL may cause aesthetic or other problems but generally are provided in Distribution of dissolved constituents above. The arrows show the acknowledged. Reviews by Tom Patton and Larry Smith are also 3, Map 6, scale 1:150,000. appreciated. are not a threat to human health. general chemical evolution along a ground-water flow path.