Regional Background Information and Assessment Methodology

Adapted From: “Hydrogeologic Assessment of the Principal Aquifers in the Upper Musselshell River Basin, Montana in Support of Source Water Assessment and Delineation Reports for Public Water Systems”

by Lisa O’Connell, Montana Bureau of Mines and Geology and Bill O’Connell, Montana Rural Water Systems, Inc.

June 2003.

Table of Contents 1. Background...... 5 1.1 Purpose...... 5 1.2 Geographic Description ...... 6 1.3 Land Use ...... 6 2. Geology of Major Aquifers...... 7 2.1 Alluvium ...... 7 2.2 Terrace Gravels...... 7 2.3 Bearpaw Shale ...... 9 2.4 Judith River...... 9 2.5 Claggett...... 9 2.6 Eagle ...... 9 2.7 Colorado Shale...... 10 2.8 Kootenai...... 10 2.9 Belt...... 10 3. Geologic Structures...... 10 3.1 Woman’s Pocket Anticline ...... 11 3.2 Shawmut Anticline...... 11 3.3 Wheatland Syncline ...... 11 3.4 Big Snowy Mountains...... 11 3.5 Little Belt Mountains ...... 11 3.6 Crazy Mountains...... 12 3.7 Castle Mountains ...... 12 3.8 Big Elk Dome ...... 12 3.9 Lake Basin Fault Zone...... 12 3.10 Little Elk Dome...... 12 3.11 Haymaker Anticline/Dome ...... 13 3.12 Daisy Dean Anticline/Dome...... 13 3.13 Gordon Butte...... 13 4. Methods...... 13 4.1 Well Inventories...... 13 4.2 Picking Geologic Formations For Wells...... 14 4.3 Ground Water Flow Direction and Hydraulic Gradient ...... 14 4.4 Delineating Inventory Regions ...... 14 4.5 Surface Water Delineations ...... 16 4.6 Inventory Method...... 16 4.7 Control Zone Delineation ...... 18 5. Principal Aquifers and Ground Water Flow For Water Sources Used For Public Water Supplies...... 18 5.1 Alluvium ...... 18 5.2 Judith River Formation ...... 19 5.3 Claggett Shale ...... 19 5.4 Eagle Formation...... 19 5.6 Belt...... 20 5.7 Other ...... 20

6. Surface Water...... 21 6.1 USGS Gaging Stations...... 21 6.1.1 USGS Harlowton ...... 21 6.1.2 USGS near Shawmut ...... 21 6.1.3 USGS near Lavina ...... 21 6.2 Surface Water Chemistry...... 21 6.2.1 USGS Harlowton ...... 21 6.2.2 USGS Near Shawmut ...... 22 6.2.3 USGS Near Lavina ...... 22 7. Other Water Resources in the Watershed ...... 22 8. Tritium Results...... 23 9. Conclusions...... 24 References...... 25 Glossary ...... 26 List of Appendices ...... 28

1. Background The Upper Musselshell is an area with very limited geological and hydrogeological information and water quality data. The impact of land use on ground water and surface water and the level of connection between them also needed to be investigated. Due to these unknowns, the Upper Musselshell watershed was chosen as the focus of this project.

Fifteen public water supplies were identified in the watershed (See Appendix I.PWS Location Map). The 15 public water supplies initially identified in the Upper Musselshell watershed were sampled and inventoried.

In 1996, Congress amended the Safe Drinking Water Act requiring the delineation of the recharge area and assessing potential contaminant sources for all public water sources (PWS). Since there are over 2000 public water sources in Montana, the delineated recharge areas will be extensive. Additionally, publicly identifying a landowner as a potential polluter of a public water system can have unintended consequences. This project is a collaborative effort between the Bureau of Mines and Geology and Montana Rural Water Systems Inc.

1.1 Purpose The purpose of the project was to educate the public about the watershed, provide water chemistry information about the principal aquifers in the area, provide PWS’s information specific to their wells, and to collect enough hydrogeologic information in the area to identify recharge areas and capture zones (a capture zone is a two dimensional delineated area based on time of travel calculation for a hypothetical water molecule) for each of the identified PWS. The PWS identified are as follows:

1. Lavina School District 2. Cozy Corner Bar (Lavina) 3. Lavina Crossing Café 4. Town of Ryegate 5. Golden Valley Hutterite Colony 6. Checkerboard Bar, Motel, and Trailer Court 7. Martinsdale WUA 8. Wade’s Drive-In (Harlowton) 9. Sportsman Bar and Steakhouse (Harlowton) 10. Duncan Ranch Hutterite Colony 11. City of Harlowton 12. Ray’s Sport and Western Wear 13. Martinsdale Hutterite Colony 14. Two Dot Water Users Co. (Two Dot) 15. Springwater Hutterite Colony.

The report will combine the required source water protection reports for the public water systems with the watershed evaluation with focus on the watershed’s relationship to the public water systems.

5

1.2 Geographic Description The Upper Musselshell watershed is located in central Montana (Figure 1. Upper Musselshell Watershed Locator Map) and is bounded to the north and west by the Little Belt Mountains, to the north by the Big Snowy Mountains, to the south and east by the Lake Basin Fault Zone and to the southwest by the Crazy Mountains. The largest town in the watershed is Harlowton, Montana, which is located in the central part of the watershed. The area of the watershed is 4023.2 square miles (2,574,848 acres). The Climate is continental type and is semi-arid in the Musselshell Basin. The average annual precipitation is 10 to 14 inches. The temperature is marked by extremes above 1000 F and below –400 F.

The watershed is bisected by two major transportation routes; both of which run through Harlowton, Montana. They are: US Route 12, which runs east to west along the Musselshell River from Checkerboard to Roundup, and US Route 191, which runs north to south from Judith Gap to Big Timber.

Figure 1. Upper Musselshell Watershed Locator Map

1.3 Land Use Land use in the area is primarily agriculture and rangeland (See Figure 2. Land use map). The watershed is surrounded by evergreen forest except to the south and northeast where there is a continuation of rangeland (See Appendix XXIV. Musselshell Landsat Photo).

6 Dryland farming of small grain crops occurs throughout the study area. In the west irrigated fields use irrigation canals and ditches, the largest of which is the Two Dot Canal. Extensive rangeland is used to feed cattle and sheep (livestock) where isolated windmills pump water to troughs.

Figure 2. Land Use Map (nris.state.mt.us)

2. Geology of Major Aquifers A generalized description of geologic stratigraphy of geologic units containing the aquifers encountered during this study is presented in Table I.

2.1 Alluvium The alluvium in the area was observed to consist primarily of fine to large grained sands with silt and clay, grading into rounded gravels and boulders.

2.2 Terrace Gravels Terrace gravels in the area primarily consist of well-rounded rocks ranging in size from sand to pebbles and range in thickness from a few feet up to tens of feet. The gravels thicken towards to the Little Belt and Big Snowy Mountains (Bowen, 1918). Outcrops of underlying formations are limited to small areas northwest of Harlowton and structures are very difficult to distinguish due to the thick gravels.

7 Table 1. General description of the geologic units in the Upper Musselshell watershed

8 2.3 Bearpaw Shale The Bearpaw shale is composed of dark-gray to black shale that contains numerous calcareous concretions. Sandy zones are present on the top and bottom of the formation and transition into overlying and underlying formations (Bowen, 1918). In T9N R14E S29 DDC (46o30.300N and 109o58.824W) poorly consolidated brown sandstone was observed in the lower unit of the Bearpaw Shale that contained several large calcareous rust-colored nodules overlain by a light gray to tan sandstone that weathered into gently rounded slabs. This unit graded upward into salt and pepper sandstone.

2.4 Judith River The Judith River formation has a thickness ranging from 400-800 feet, with the beds thickening and becoming more andesitic to the west (Stone, 1907). Upper beds consist of alternating beds of sandstone and shale with some thin coal beds. In the top bed, which is up to 15 feet thick, is a brown coarse-grained sandstone unit containing abundant oyster shells. This bed was observed northwest of Harlowton at T9N R14E S29DDC (46o30.258 N and 109o59.494 W) (See Figure 4. Site numbering system) during fieldwork for this project in September 2002 and confirmed by Stone (1907). This bed also was found to contain fossil bones and wood fragments near Gordon Butte during fieldwork for this project and was also later confirmed by Stone (1907). Overlying this bed was a very poorly consolidated, coarse-grained tan sandstone unit, which was in turn overlain by a poorly cemented conglomerate consisting of white chert and quartzite nodules. This is the only area where the conglomerate was observed during this project. The middle beds are medium to fine-grained brown to buff sandstone. The lower unit consists of alternating beds of gray to tan sandstone and shale. This lower unit has also been mapped as the top of the Claggett formation (Bowen, 1918). Where the formation is dipping, it forms a low ridge and appears to be dark gray.

2.5 Claggett The Claggett formation has a thickness ranging from 400-800 feet (Stone, 1907). The Claggett is a marine and brackish-water deposit and consists of alternating beds of white to gray, medium to very fine-grained sandstone and dark shale. The Claggett is mostly dark shale in the eastern portion of the watershed with the sand content increasing as you move west in the watershed. Due to the increase of sand content, the top of the Claggett closely resembles the Judith River formation and the base of the Claggett closely resembles the Eagle formation west of Harlowton. The best distinction between the formations in this area is the difference in water quality. The Claggett produces large quantities of sodium-sulfate type water with high amounts of dissolved solids.

2.6 Eagle The Eagle sandstone has a thickness ranging from 200-400 feet. The Eagle sandstone is a marine deposit and consists of three members. The upper members consist of interbedded medium to fine-grained gray sandstone and shale. The top member consists of interbedded gray sandstone and shale (Stone, 1907) and is similar to the Claggett and is difficult to distinguish from the base of Claggett from lithologies alone but water quality was found to be a good indicator as water in the Eagle is sodium-bicarbonate type water and water from the Claggett is sodium-sulfate type water. Water that is sodium bicarbonate-sulfate probably indicates a mixture of the two types of ground water. The lower member is the Virgelle, which consists of white sandstone to the east and has either 9 pinched out to the west or changes in composition to thinly bedded medium-grained gray sandstone that weathers to a dark brown. The sandstone layers are massive to the east and thin to the west. The sandstones are resistant to erosion and weather into ledges near Martinsdale. There is a thin coal bed found in the Eagle in this watershed with outcrops between Martinsdale and Lennup, on the east side of Big Elk Dome, and north of Fish Creek and Mud Creek (Stone, 1907). The base of the Eagle was mapped by Bowen (1918) (See Appendix XXIX. Map of the Base of the Eagle Sandstone).

2.7 Colorado Shale The Colorado shale is approximately 2,200 feet thick and consists primarily of dark shale. At approximately 1,200 feet below the top of the formation, lies the Big Elk Sandstone. The Big Elk sandstone, which is named from its outcrops on Big Elk Dome, is at the approximate location of the Frontier in the eastern part of the state. The sandstone contains a thin conglomerate layer on the top containing fish teeth and bone fragments (Bowen, 1918) and contains quartzite sandstones and shales that overlie a coarse-grained, massive sandstone bed. The base of the formation contains shales with some thin beds of sandstone.

2.8 Kootenai The top of the Kootenai formation consists of thinly bedded, fine-grained sandstone that is rusty in appearance. Below this is greenish-gray shale and alternating beds of maroon and white shale interbedded with thin sandstone beds. The lowest member consists of coarse gray sandstone (Bowen, 1918).

2.9 Belt Belt supergroup undifferentiated. The members of the Belt defined by C.D. Walcott (Weed, 1898) are from top to bottom: Marsh Creek shale, Helena limestone, Empire shale, Spokane shale, Greyson shale, Newland limestone, Chamberlain shale, Neihart quartzite.

3. Geologic Structures The geologic structures in the area are important in the study of groundwater flow because they determine where groundwater is being recharged, the direction of groundwater flow, and if the aquifer will be pressurized and to what degree. Deformation of strata during the formation of structures results in strata being uplifted or dropped, or fractured, thus changing the direction of ground water flow. Structures such as dikes, sills, or faults that intrude strata can act as a barrier to ground water flow and can change the direction of flow or channel flow through fractures. The difference in elevation from the recharge area to the aquifer at the well site determines the amount of pressure in a confined aquifer.

The Musselshell River Basin is a geologically complex area (See Figure 3. Location of Geologic Structures). The Little Belt Mountains to the north and west of the watershed were formed by thrust faulting during the Larimide Orogeny, a mountain building event that occurred 70 million years ago when the North American Crustal Plate collided with the Pacific Crustal Plate. This event probably also created the syncline and anticline structures that bisect the region. 10

50 million years ago major igneous activity throughout central Montana created many of the structures visible today. The Crazy and Castle Mountains on the west and southwest boundaries of the region, have large igneous cores that lifted the overlying sedimentary formations high above the original land surface. On a smaller scale, magma in the form of dikes, sills, laccoliths, and vents rising from deep in the earth created the domes and buttes that dot the region. Erosion has exposed some of the igneous cores of these structures.

Figure 3. Location of Geologic Structures (From Map of Central and Eastern Montana showing Major Geologic Structures: Montana State Bureau of Mines 1921)

3.1 Woman’s Pocket Anticline The Woman’s Pocket anticline extends from north of Ryegate to north of Lavina and is 18 miles long and over 3.5 miles wide and trends from northeast to southwest. The dip of the southwest limbs range from 18 to 60 degrees and the northeast limbs range from 3 to 5 degrees. The Colorado shale outcrops on the top of the anticline and the Eagle sandstone outlines the anticline (Bowen, 1918).

3.2 Shawmut Anticline The Shawmut anticline extends from west to east and slightly northeast. The anticline is 30 miles long and over 8 miles wide. It contains local features such as Deadman’s Basin to the east and West Dome, Middle Dome, and East Domes to the west. These local features give the axis of the anticline a wavy appearance. The dip of the north limbs range from 2 to 8 degrees and the south limbs dip from 16 to 46 degrees. The Kootenai formation outcrops on the top of West and Middle Domes and all of the domes are surrounded by the Big Elk formation of the Colorado Shale.

3.3 Wheatland Syncline The Wheatland Syncline is a large downward fold in the earth’s crust that trends northeast from between Two Dot and Harlowton to southwest of Judith Gap, where it bends and then trends east between the Woman’s Pocket anticline and the Big Snowy Mountains (Groff, 1962). The tectonic forces that formed the Little Belt Mountains by folding the sedimentary formations to the point of breaking and then thrusting the broken folds up over each other, also formed the Wheatland Syncline.

3.4 Big Snowy Mountains The Big Snowy Mountains are a dome-shaped structure. The Madison Limestone (deposited about 300 million years ago) is exposed at the center of the mountains.

3.5 Little Belt Mountains The Little Belt Mountains form the northwestern boundary of the watershed. The Mountains formed as a result of a faulted crustal arch, which brought older Paleozoic formations to the surface. The Belt rocks form the center of the range to the west. In the center of the Mountains the Madison limestone formations appear white and have deep gorges, caves, and abandoned stream tunnels carved through them from dissolution of the 11 limestone by rainwater moving through fractures (Weed, 1898). The Madison is a major aquifer for central Montana and is recharged in these mountains. The highest peaks in the mountains are formed from igneous intrusions (laccoliths) that have deformed the strata locally. Igneous intrusions also form dikes and stocks in the Little Belt Mountains.

3.6 Crazy Mountains The Crazy Mountains form the southwest boundary of the watershed. They are composed of alkalic (base instead of acid) igneous rocks that are rich in sodium and potassium. The peaks are igneous rocks and hard, altered rock from the contact zone where the sedimentary rock was altered from the igneous intrusion. In the northern part of the Crazy Mountains, sheet intrusions are the most common, though the rocks are uplifted and tightly folded. Sheets of igneous rock occur most commonly along shale layers.

There are visible glacial features on the mountains, which give them a unique appearance in this area (Weed, 1898). It is unusual that there are no volcanic rocks and that the intrusions did not form a syenite cap. The Crazy Mountains contain dike swarms that extend radially from the mountains, much like the spokes of a wagon wheel, intruding the younger sedimentary rocks (Alt, 1986).

3.7 Castle Mountains The Castle Mountains form the western border of the watershed. The mountains formed when a volcanic vent formed in folded, faulted, and eroded sedimentary rocks. Further eruptions and subsequent erosion occurred later. Part of the magma that made up the core of the Castle Mountains erupted to form lava flows and volcanic ash, which remains present in the mountains. They have a granitic core that crystallized at a shallow depth and is approximately 50 million years old. The granite weathers into rounded blocks. The Castle Mountains define the eastern limit of the Rocky Mountains (Weed, 1898).

3.8 Big Elk Dome The Big Elk dome is located south of Two Dot and is roughly 36 square miles in area. The dip of the beds on the south side of the Big Elk Dome range from 15 to 30 degrees, and range from 6 to 10 degrees on all of the other sides of the dome. The Big Elk sandstone is on the surface at the center of the dome and is thus named. On the western edge of the dome is an igneous mass known as East Coffin Butte. While it is unknown if the Big Elk Dome was formed by a laccolith, a petroleum well drilled in 1972 at T7N R13E S28 DA (See Appendix xx. Location Numbering System) was drilled to a depth of 5028 feet, with the bottom strata logged as Jefferson dolomite underlain by Cambrian rock and the log shows no indication of igneous rock at this depth.

3.9 Lake Basin Fault Zone The Lake Basin Fault Zone forms the southern boundary of the watershed and is a southeast trending fault zone composed primarily of a series of normal and reverse faults with some oblique faulting. The Lake Basin Fault Zone acts as a divide between the Yellowstone and Musselshell basins.

3.10 Little Elk Dome The Little Elk dome is located between Little Elk and Fawn Creeks. The dome extends from east to west for approximately 8 miles and north to south for approximately 4 miles. 12 The beds dip from 8 to 15 degrees to the north, 10 to 25 degrees to the south, and 25 to 45 degrees to the west. The top of the dome is composed of the sandstones of the bottom of the Colorado that are cut by dikes and igneous rock masses.

3.11 Haymaker Anticline/Dome This structure has been mapped as an anticline by Bowen (1918) and as a dome on the Montana State Bureau of Mines Map of Central and Eastern Montana(1921). Due to the thickness of the terrace gravels in the area and the lack of outcrops, the writer has been unable to determine which is correct. Cross sections drawn using geologic information from petroleum well logs supported the presence of either an anticline or a dome but there was not enough information available to determine which structure was present. The Haymaker anticline/dome is located north of Two Dot and is connected by a small neck of Little Elk dome to the southwest and to the Little Belt Mountains to the north. The dips are steepest on the east limb and range from 12 to 24 degrees, on the north limb, the dip is gentler and is reported to be 2 degrees (Bowen, 1918).

3.12 Daisy Dean Anticline/Dome This structure has been mapped as an anticline by Bowen(1918) and as a dome on the Montana State Bureau of Mines Map of Central and Eastern Montana(1921). Due to the thickness of the terrace gravels in the area and the lack of outcrops, the writer has been unable to determine which is correct. The anticline/dome is located northeast of Martinsdale and opens to the north to the Little Belt Mountains and is approximately 4 miles in diameter (Bowen, 1918).

3.13 Gordon Butte Gordon Butte, located just southwest of Martinsdale, is a circular-shaped intrusion that is approximately 1 mile in diameter and 365 feet thick at the top of the Butte and a lower sheet approximately 150 feet thick at the base in the sedimentary rocks (Weed, 1898). Gordon Butte is a laccolith that intruded the Fort Union formation. The intrusion that forms Gordon Butte is composed of the same sodium rich magma (Fenite) that formed the Crazy Mountains and is referred to as the northern most member of the Crazy Mountains. The sodium-rich intrusion called shonkinite is unique to this area (Alt, David et al., 1986).

4. Methods

4.1 Well Inventories During the course of this project, 83 wells, 6 springs, and 3 USGS stream gauging sites were inventoried (See Appendix III. All Musselshell Well and Water Quality Data). Inventories included measuring the static water level in the well, location of the well, the depth of the well, the size of the casing, the pumping rate, the pumping water level, the pH, specific conductance, the temperature of the water, and observations regarding the condition and location of the well and water. Some measurements in the inventory were not obtained due to the poor condition of the well, no pump, or no vertical access due to the piping configuration of the well, or because the landowner was reluctant to have anyone open the well. Every effort was made to accommodate the wishes of the landowner and to explain what we were measuring and what the measurements would tell

13 us. Static water levels could not be obtained in some areas due to no vertical access to the well or because the well had been recently pumped.

Township, range, section, and tract site numbering system shown in figure 4 was used to identify well locations..

Figure 4. Site numbering system (From Kate Miller, MBMG)

4.2 Picking Geologic Formations For Wells The wells were classified by the geologic formations in which they were completed by interpreting the lithology listed on the well logs, geologic maps, and water quality results. Where lithologic information was limited, water quality characteristics were used for geologic interpretation. The aquifer name and the geologic formation containing the aquifer are the same.

4.3 Ground Water Flow Direction and Hydraulic Gradient The ground water flow direction and hydraulic gradient were determined for each aquifer by plotting the position of the well and contouring the static water level on 100-foot contours. The contours were drawn using the three-point method (See Figure 5. Three Point Method). Three adjacent wells were used with the wells of the highest and lowest joined by a line and then they were both joined by lines to the third well forming a triangle and scaled based on where on each of the lines each 100 foot contour fell. The 100-foot contours are then joined at lines of equal potentiometric elevation. Ground water flow direction is from lines of higher elevation to lines of lower elevation and is perpendicular to contours. The slope of the contours is the hydraulic gradient.

Figure 5. Three Point Method (Arrow indicates flow direction.)

Water level information contained in the Ground water Information Center database (GWIC) was used to supplement water level field data. 119 Well logs from wells found in the GWIC database were used to fill in information on static water levels in the Upper Musselshell watershed. The criteria used for selecting the wells were:

1. The well must have been drilled since 1998, 2. There must be lithologies described,

4.4 Delineating Inventory Regions The Uniform Flow Equations were used to determine the extent of the capture zone for a well. The Equations are an analytical solution to ground water flow using measured and calculated aquifer characteristics.

The Equations use the following simplifying assumptions: 14 1. The aquifer is homogeneous and infinite in extent. This condition is not found in nature but because of the moderate production rates of the wells and the volume of water in the aquifer, this condition is met to the accuracy the delineations require. 2. The ground water flow is uniform in all directions. Ground water flows along the path of least resistance and at the local level is rarely uniform. However, due to the size of the aquifer in relation to the well and the low ground water flow velocities, this assumption is met to the accuracy the delineation requires.

The Uniform Flow Equations are used to calculate the down-gradient and lateral extent of the capture zone under steady state conditions (equilibrium). The Capture Zone is the calculated area from which ground water could be drawn into the well. The Capture Zone is calculated using the well pumping rate and the aquifer characteristics.

The up-gradient extent of the capture zone uses a time-of-travel equation based on well production and aquifer characteristics including the hydraulic gradient(i), aquifer porosity(0), hydraulic conductivity(K).

Aquifer Characteristics:

Hydraulic gradient (i)=(change in hydraulic head)/(distance between head measurements)(dh/dl)

Transmissivity (T)=2000*Q/s Where: Q-flow from the well in gallons per minute s-drawdown of the well in feet

Hydraulic conductivity(K)=T/b Where: b-saturated thickness of the aquifer in feet

Uniform Flow Equations:

Down Gradient in feet (-XL)=((1440/7.48)*Q)/(2ΒTi)

Lateral Limits in feet (YL)= -XL*Β

Time of Travel Calculation (For PWS time of travel calculations See Appendix XXIII. Time of Travel Calculations):

Upgradient Extent (X)=Kit/0 Where: t-time in days: t=5 years for an unconfined aquifer, t=10 years for a confined aquifer 0-% porosity

15 A 1000-foot radius circle that is centered on the well is the default delineation boundary for inventory regions (See Appendix XX. Glossary) with delineated areas less than 1000- feet. This is the minimum area allowed for a public water supply’s inventory region. This can also be used if aquifer characteristics and additional wells in the area are not available.

4.5 Surface Water Delineations While there are no public water systems in the watershed that use surface water as their water source, there is one PWS (Ryegate) that uses an infiltration gallery. An infiltration gallery is a shallow horizontal well near a lake or river. This water source may be determined to be ground water under the direct influence of surface water (GWUDISW). In these cases, the inventory region delineation is either ½ mile on either side of the stream for an upgradient distance of 10 miles or a ½ mile buffer zone around the lake or reservoir.

4.6 Inventory Method DEQ Databases located at nris.state.mt.us were searched to identify businesses and land uses that are potential sources of regulated contaminants in the inventory region as well as on-site investigations. The following steps were followed:

Step 1: Major road and rail transportation routes were identified throughout the inventory region.

Step 2. All land uses and facilities that generate, store, or use large quantities of hazardous materials were identified within the recharge region and identified on the base map.

Potential contaminant sources are designated as significant if they fall into one of the following categories:

1. Large quantity hazardous waste generators 2. Landfills 3. Hazardous waste contaminated sites 4. Underground storage tanks 5. Major roads or rail transportation routes 6. Cultivated cropland 7. Animal feeding operations 8. Wastewater treatment or spray irrigation 9. Septic systems 10. Storm sewer outflows

An explanation of the rating system to evaluate hazard levels of potential contaminant sources is outlined in Table 2.

16 Table 2. Hazard of Potential Contaminant Sources

High Hazard Moderate Hazard Low Hazard

Point Sources of All Contaminants Within one-year TOT One to three years TOT Over three years TOT

More than Less than Septic Systems 300 per sq. mi. 50 – 300 per sq. mi. 50 per sq. mi.

Municipal Sanitary Sewer More than 50 percent of 20 to 50 percent Less than 20 percent of (Percent land use) region of region region

Cropped Agricultural Land More than 50 percent of 20 to 50 percent Less than 20 percent of (Percent land use) region of region region

17 4.7 Control Zone Delineation The control zone is the 100-foot radius circle centered on the well. The control zone is (required under DEQ1, “Construction Standards for Water and Wastewater Facilities for Public Water Systems”) regulated at the state level by specific standards. The purpose of the control zone is for the PWS to have control over land use activities, which could potentially contaminant or impact the well. Certain land use activities are prohibited in the control zone and the PWS must have control over this area through ownership or easements.

5. Principal Aquifers and Ground Water Flow For Water Sources Used For Public Water Supplies

5.1 Alluvium Wells completed in alluvium produce water ranging from 5 gpm in the western part of the watershed near Checkerboard to a reported 150 gpm in the eastern part of the watershed near Lavina (See Appendix III. All Musselshell Well and Water Quality Data). Ground water flow is to the east and toward the river from the north and south, indicating that the river is receiving recharge from the alluvial aquifers throughout the watershed from Checkerboard to Lavina (See Appendix IV. Ground Water Level Map of Wells Completed in the Alluvium). This flow direction can change when the water levels in the alluvial aquifer are decreased due to drought or lack of recharge to the alluvial aquifer.

The water quality of wells sampled in T10N R11E S34 BADA indicates that the water is a calcium bicarbonate type with Total Dissolved Solids (TDS) of 435 mg/L (See Appendix V. Water Quality Characteristics of Wells Completed in the Alluvium and From the Musselshell River). The water quality of the alluvial aquifer near Two Dot also indicates the water is calcium bicarbonate type water with TDS increasing to 721 mg/L. There is no more down gradient information regarding water quality in the alluvium until Ryegate, where the water quality of the alluvial well sampled there indicates the water has changed to sodium-calcium-magnesium sulfate type water with TDS increasing to 1213 mg/L. This change in ground water chemistry is probably due to dissolution of salts as the water moves through the flow path. Public Water Supplies, which draw water from the alluvial aquifer, are:

1. Ryegate PWS 2. Lavina Crossing Café 3. Lavina School 4. Lavina Post Office

The sulfate and the sodium in the ground water increases to the east towards Lavina with a significant increase between Ryegate and Shawmut (See Appendix XXV. Constituent Contours in mg/L). In this area the Claggett, a formation containing high levels of sulfate and sodium, outcrops and is being eroded and deposited as the alluvium (See Appendix XXVI. Ryegate Geologic Map). The sulfate and sodium are being dissolved into the ground water and surface water.

18 5.2 Judith River Formation There were no PWS in the watershed that used the Cretaceous-age Judith River formation for their primary drinking water source. Flow in wells completed in the Judith River ranged from 6 gpm at T8N R19E S18 BDA to 30 gpm at T07N R14 S6 BC. The direction of ground water flow (See Appendix VI. Ground Water Level Map of Wells Completed in the Judith River Formation) in the west of the watershed is easterly until just west of Harlowton. At this point, flow lines converge on a spot just north of Harlowton where there are flow components from the north, west, and south. To the east the ground water flow resumes flowing to the east. The ground water flow direction can be refined as more information becomes available.

Five samples were collected for inorganic chemical analysis from wells completed in the Judith River formation. At T10N R16E S31 A and T5N R18E S12 AADC (See Appendix VII. Water Quality Characteristics of Wells Completed in the Judith River Formation), ground water quality from wells for which the lithologies indicate were completed in the base of the Judith River formation have high total dissolved solids and sodium sulfate type water that is difficult to distinguish by water quality from the Claggett. Water chemistry results indicate that both samples, which contain sodium-sulfate type water, had TDS being 2844 mg/L and 2734 mg/L respectively. Wells completed in the upper part of the Judith River have lower TDS of 1289, 1457, and 1089 mg/L respectively and have sodium-bicarbonate type water.

5.3 Claggett Shale Water production from wells completed in the Claggett formation ranges from 4 gpm at T8N R22E S17 ACC to 130 gpm at T8NR14E S19 BABC. The Claggett formation has stronger flow near Harlowton, as this is an area where the ground water flow lines converge (See Appendix VIII. Ground Water Level Map of Wells Completed in the Claggett Shale). The direction of ground water flow in the Claggett, based on the static water in wells completed in the Claggett flows to the east and north in the western part of the watershed. Water chemistry in the Claggett formation indicates sodium sulfate type water with TDS increasing from 1616 mg/L in the west (north of Martinsdale) to 2839 mg/L farther east (near Lavina) (See Appendix IX. Water Quality Characteristics of Wells Completed in the Claggett Shale). This may be explained by the increased shale content to the east (Bowen, 1918). The TDS are well above the secondary drinking water recommendations. The sulfate content increases gradually toward the east, which is reasonable as the Claggett has greater shale content to the east (See Appendix XXV. Constituent Contours in mg/L).

Public water supplies that are completed in the Claggett Formation, are: 1. Martinsdale Colony 2. Duncan Ranch Colony 3. Wade’s Drive In 4. Cozy Corner Bar

5.4 Eagle Formation Water production rates from the Eagle range from 1gpm at T9N R12E S6 A to 650 gpm at T8N R15E S21 DBBD. The Eagle has stronger flow near Harlowton (400 gpm at Harlowton to 35 gpm at Spring Water Colony just east of Harlowton to an average of 12 19 gpm east of Springwater Colony), as this is an area where, ground water flow converges (See Appendix X. Ground Water Level Map of Wells Completed in the Eagle Formation).

The ground water chemistry in the Eagle indicates sodium bicarbonate type water with sodium bicarbonate-sulfate type water where there is a mixture, as a result of the well receiving water from multiple aquifers. The TDS ranges from 576 mg/L south of Judith Gap to 2842 mg/L at Lavina (See Appendix XI. Water Quality Characteristics of Wells Completed in the Eagle Formation).

Public water supplies, which are completed in the Eagle formation, are:

1. Harlowton-West Municipal 2. Harlowton-Thompson 3. Harlowton-South Well 4. Sportsman Bar and Steakhouse 5. Ray’s Sports and Western Wear 6. Springwater Colony 7. Golden Valley Colony

5.6 Belt Belt is bedrock composed of Precambrian Belt formations. The formations are composed of highly altered sedimentary units. Due to the very low effective permeability of the rocks, recharge is from fracture flow (secondary porosity) in the formation, due to this flow regime, a static water level map was not plotted for the Belt. Thus, infiltrating surface water is channeled through fractures at greater flow rates than through the rock. The water quality from the wells tested indicates the water is calcium-magnesium sulfate (See Appendix XXII. Water Quality Characteristics of Wells Completed in the Belt Formation).

Public water supplies, which are completed in the Eagle formation, are:

1. Checkerboard Bar, Motel, and Trailer Court

5.7 Other Martinsdale’s water source is water infiltrating into the igneous rocks, which compose the exposed portion of Gordon Butte. The Butte is composed of two sheets of igneous rock with a sandstone unit between. The upper layer is approximately 365 feet thick and is separated from the lower unit by an approximately 200-foot thick sandstone unit of the Fort Union Formation (Weed, 1898). The lower unit is approximately 150 feet thick. The water flows through fractures due to the low permeability of the rocks on the Butte eventually exiting in the form of the upper springs. The lower springs are formed from fracture flow from the upper igneous layer and infiltration through the sandstone unit. The springs form when the water reaches the low permeability lower igneous layer and exit along the contact.

20 6. Surface Water On September 28-29, 2002, three USGS Stream Gauging Sites were sampled on the Musselshell River. All three of the sites were located in the study area. The three sites were located at Harlowton, Near Shawmut, and Near Lavina. Water quality results are shown graphically in Appendix V. Alluvial and River Stiff Diagrams. All of the samples were depth integrated to reflect the overall water quality of the site.

6.1 USGS Gaging Stations

6.1.1 USGS Harlowton The USGS stream gage at Harlowton (USGS Site # 06120500) is located on the Musselshell River at T08N R15E S27 (46.4300, -109.8400). It is the most western stream-gaging site on the Musselshell River. The site records real time data and has recorded daily stream flow data dating from 1907. It has 94 recorded peak stream flow data points, 34,334 daily stream flow data points, and 154 water quality samples (of the 154 samples-7 were tested for constituents beyond parameters). The datum of the gage is 4,171.46 feet above sea level.

6.1.2 USGS near Shawmut The USGS near Shawmut (USGS Site # 06123030) is located on the Musselshell River at T07N R18E S34 Tract DDA (46.31860,-109.45970). The site records real time data, and has been collecting data since 1998. It has 5 recorded peak streamflow data points, 975 recorded daily streamflow data points, and 25 water quality samples (temperature of water and air, Specific conductance). The datum of the gage is 3,790 feet above sea level.

6.1.3 USGS near Lavina The USGS near Lavina (USGS Site # 06126050) is located on the Musselshell River at T06N R23E S06 Tract BDD (46.29280,-108.89190). The site records real time data and has been collecting data since 1992. There are 11 data points for peak streamflow, 2385 data points for daily streamflow, and 65 water quality samples (temperature of water and air, specific conductance). The datum of the gage is 3400 feet above sea level.

6.2 Surface Water Chemistry

6.2.1 USGS Harlowton USGS Site # 06120500, which is located on the south side of Harlowton, was sampled on 9/28/2002 (See Appendix III. All Musselshell Well and Water Quality Data). The sample was depth-integrated; the sample was a mixture of water collected at several different depths. The water was calcium-magnesium-sulfate type water. The total dissolved solids in the sample were 746.48 mg/L, the temperature of the water was 8.3oC, and the pH was 7.92. The water quality at the site was compared using data points from 1988 to 2002 (See Figure 21. USGS Harlowton: Water Quality 1988 to 2002) and no trends were found. The maximum sample for magnesium, sodium, potassium, chloride, and sulfate was the sample taken on 7/26/1988, while the 6/20/1991 sample was the minimum for all of the constituents except it was the maximum for silica.

21

USGS Harlowton: Water Quality 1988 to 2002

1000

100 6/30/1988 12:00 7/26/1988 11:30 10 6/29/1989 8:25 Log mg/L 7/27/1989 9:30 1 8/8/1990 12:30 6/20/1991 8:00

Silica 7/25/1991 9:50 Sulfate Sulfate Sodium Sodium Calcium Chloride Chloride 9/28/2002 Potassium Magnesium Magnesium Constituent

Figure 21. USGS Harlowton: Water Quality 1988 to 2002

6.2.2 USGS Near Shawmut USGS Site # 06123030 is located on a dirt farm road near Shawmut along the Musselshell River. A depth-integrated sample was obtained from the site on 9/28/2002. The water was sodium-calcium-magnesium-sulfate type water. The total dissolved solids in the sample were 910.52 mg/L, the temperature of the water was 9.1oC, and the pH was 7.79.

6.2.3 USGS Near Lavina USGS Site # 06126050 is located on a dirt road east of Lavina, along the Musselshell River. A depth-integrated sample was obtained from the site on 9/27/2002. The water was sodium-magnesium-sulfate type water. The total dissolved solids in the sample were 2138.15 mg/L, the temperature of the water was 10.2oC, and the pH was 10.2.

7. Other Water Resources in the Watershed The Upper Musselshell Watershed PWS use a variety of aquifers, most of which provide drinking water with marginal water quality. At the same time as this project was being completed, an effort was being made to locate a regional water source. During this project, several potential water sources were identified. These sources stand out due to either exceptional water quality or quantity.

22

A series of springs that forms Crooked Creek was tested and was found to be of very high quality water. The TDS were 229.4 mg/L and the water was calcium-bicarbonate type water. The flow was calculated using Haestads Methods software v.6 and was found to yield >900 gpm. Manning’s equation was used for a trapezoidal channel and a natural weedy streambed. The springs are located on the west side of an igneous dike trending S47oE that cuts the light gray sandstone from which the springs flow. The dike is acting as a barrier to flow through the sandstone. Groundcover was too thick to determine the dip of the sandstone beds at the springs. Above the springs, the offset of the sandstone beds, provides evidence of a fault.

A series of springs that forms Bear Creek was tested and found to be of very high quality water. The TDS were 211.8 mg/L and the water was calcium-bicarbonate type water. Flow was not determined. The springs are located in a marshy area surrounded by willows and several springs connect to form the creek.

A petroleum well drilled on the Haymaker Ranch several miles north of Two Dot, was reported to have a sustained yield of >3000 gpm. The well was not tested and was found to have been capped and the surface casing pulled. Another petroleum well on the Haymaker Ranch, which was completed in 1946 into the Big Elk Formation was tested. The well flows over the top of the casing, which is 7.9 feet above the ground surface. The TDS were 1165 mg/L and the water was sodium-bicarbonate type water.

A 1660-ft deep petroleum well located at T6N R19E S28 BDDD that was reported to have been completed in the Big Elk formation was tested. The well flows but has a slight gas smell. The TDS were 2053.9 mg/L and the water was a sodium-bicarbonate type water. The flow was too fast to measure with a bucket.

The high yields in the Eagle aquifer at Harlowton are due to a mapped convergence of ground water flow in the Harlowton area. A similar convergence has also been noted northwest of Ryegate. Ground water testing of the Eagle aquifer south of Ryegate indicated the water has an SC of 642.5 mg/L and was a sodium-bicarbonate type water.

8. Tritium Results Tritium sampling was performed on several sites to refine time of travel calculations and to characterize the aquifers. Sites were chosen that were completed over one geologic unit to ensure water was coming from one aquifer. Tritium analysis can determine if the ground water is older than 1959, less than 10 years old, and between 10 and 44 years old. Further attempts to refine the age of the water are being made based on precipitation in the area, infiltration based on soil type, natural decay of tritium, and atmospheric levels of tritium. Tritium-Helium tests, which are more exact regarding the date of the water, were not done due to time limitations and being out of the scope of this project.

23 The sites sampled as well as the results are listed in Table 16.

Table 16. Tritium Results M: Site Id Tritium Units Aquifer Approximate Age 1630 <0.8 +/- 0.2 Big Elk Recharged prior to 1959 188476 8.3 +/- 0.7 Claggett Recharged since 1959 197824 6.2 +/- 0.5 Claggett Recharged since 1959 197744 18.0 +/- 1.3 Unknown Recharged since 1959 188460 <0.8 +/- 0.2 Kootenai Recharged prior to 1959 1638 16.9 +/- 1.3 Eagle Recharged since 1959

9. Conclusions

The hydrogeological watershed assessment significantly increased the confidence in estimating ground water flow direction and hydraulic gradient when performing time of travel and uniform flow calculations. The increased confidence will allow for more effective management planning when dealing with potential contaminants in the inventory region.

The watershed investigation brought together two groups who have not previously worked together. The groups are: the landowners within the conservation district and the operators and managers of public water supplies. Both parties were aware of the goals and objectives of the project. The resulting cooperation in developing management strategies exceeded the expectations of the project.

The hydrogeological evaluation provided by the watershed assessment gives the conservation district baseline information that will be useful in completing other required land use evaluations, such as TMDL plans.

The success in fostering cooperation between different land-user groups in the watershed makes this approach recommended for areas that may already have extensive Wellhead Protection/Source Water Protection programs.

Some wells and springs that were tested for water quality could not be classified due to lack of geologic information in the area, information about the well, or unique water chemistry. Stiff diagrams for these wells were plotted and are found in Appendix XXI. Water Quality Characteristics of Wells of Unknown Completions). Furthermore some wells were completed in aquifers for which few other water chemistry analysis exist and are found in Appendix XXII. Water Quality Characteristics of Wells Completed in Assorted Aquifers). Finally, this study increased the body of knowledge of geology and hydrogeology of the region.

24 References

Alt, David, and Hyndman, Donald W., Roadside Geology of Montana, 427 pages

Bowen, C.F., 1918, Anticlines in a Part of the Musselshell Valley, Musselshell, Meagher, and Sweetgrass Counties, Montana: USGS Bulletin 691, p185-209

Groff, S.L., Reconnaissance Ground-Water Studies, Wheatland, Eastern Meagher, and Northern Sweet Grass Counties, Montana: Montana Bureau of Mines and Geology, Special Publication 24, Ground water Report I, March, 1962, 17 pages

Hem, John D., Study and Interpretation of the Chemical Characteristics of Natural Water: USGS Water-Supply Paper 2254, 1992

Stone, R.W., 1907, Coal Near the Crazy Mountains, Montana: USGS Bulletin 341, p78- 91

Weed, Walter Harvey, Little Belt Mountains Folio, Mt: USGS 1898

Wilde, Edith, M., and Porter, Karen, W., 2001, Geologic Map of the Harlowton 30’ x 60’ Quadrangle, Central Montana

Wilde, Edith, M., and Porter, Karen, W., 2000, Geologic Map of the Roundup 30’ x 60’ Quadrangle, Central Montana

25 Glossary

Acute Health Effect. An adverse health effect in which symptoms develop rapidly.

Alkalinity. The capacity of water to neutralize acids.

Aquifer. A water-bearing layer of rock or sediment that will yield water in usable quantity to a well or spring.

Best Management Practices (BMPs). Methods that have been determined to be the most effective, practical means of preventing or reducing pollution from nonpoint sources.

Coliform Bacteria. Bacteria found in the intestinal tracts of animals. Their presence in water is an indicator of pollution and possible contamination by pathogens.

Confined Aquifer. A fully saturated aquifer overlain by a confining unit such as a clay layer. The static water level in a well in a confined aquifer is at an elevation that is equal to or higher than the base of the overlying confining unit.

Confining Unit. A geologic formation that inhibits the flow of water.

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Enacted in 1980. CERCLA provides a Federal "Superfund" to clean up uncontrolled or abandoned hazardous-waste sites as well as accidents, spills, and other emergency releases of pollutants and contaminants into the environment. Through the Act, EPA was given power to seek out those parties responsible for any release and assure their cooperation in the cleanup.

Delineation. A process of mapping source water management areas.

Hardness. Characteristic of water caused by presence of various salts. Hard water may interfere with some industrial processes and prevent soap from lathering.

Hazard. A measure of the potential of a contaminant leaked from a facility to reach a public water supply source. Proximity or density of significant potential contaminant sources determines hazard.

Hydraulic Conductivity. A coefficient of proportionality describing the rate at which water can move through an aquifer.

Inventory Region. A source water management area that encompasses the area expected to contribute water to a public water supply within a fixed distance or a specified ground water travel time.

Maximum Contaminant Level (MCL). Maximum concentration of a substance in water that is permitted to be delivered to the users of a public water supply. Set by EPA under authority of the Safe Drinking Water Act.

Nitrate. An important plant nutrient and type of inorganic fertilizer. In water the major sources of nitrates are septic tanks, feed lots and fertilizers.

Nonpoint-Source Pollution. Pollution sources that are diffuse and do not have a single point of origin or are not introduced into a receiving stream from a specific outlet.

Pathogens. A bacterial organism typically found in the intestinal tracts of mammals, capable of producing disease.

Point-Source. A stationary location or fixed facility from which pollutants are discharged.

26 Public Water System. A system that provides piped water for human consumption to at least 15 service connections or regularly serves 25 individuals.

Pumping Water Level. Water level elevation in a well when the pump is operating.

Recharge Region. A source water management region that is generally the entire area that could contribute water to an aquifer used by a public water supply. Includes areas that could contribute water over long time periods or under different water usage patterns.

Resource Conservation and Recovery Act (RCRA). Enacted by Congress in 1976. RCRA's primary goals are to protect human health and the environment from the potential hazards of waste disposal, to conserve energy and natural resources, to reduce the amount of waste generated, and to ensure that wastes are managed in an environmentally sound manner.

Section Seven Tracking System (SSTS). SSTS is an automated system EPA uses to track pesticide producing establishments and the amount of pesticides they produce.

Source Water Protection Area. For surface water sources, the land and surface drainage network that contributes water to a stream or reservoir used by a public water supply.

Static Water Level (SWL). Water level elevation in a well when the pump is not operating.

Susceptibility (of a PWS). The potential for a PWS to draw water contaminated at concentrations that would pose concern. Susceptibility is evaluated at the point immediately preceding treatment or, if no treatment is provided, at the entry point to the distribution system.

Synthetic Organic Compounds (SOC). Man made organic chemical compounds (e.g. herbicides and pesticides).

Total Dissolved Solids (TDS). The dissolved solids collected after a sample of a known volume of water is passed through a very fine mesh filter.

Transmissivity. The ability of an aquifer to transmit water.

Unconfined Aquifer. An aquifer containing water that is not under pressure. The water table is the top surface of an unconfined aquifer.

Underground Storage Tanks (UST). A tank located at least partially underground and designed to hold gasoline or other petroleum products or chemicals.

Volatile Organic Compounds (VOC). Any organic compound which evaporates readily to the atmosphere.

* Definitions taken from EPA’s Glossary of Selected Terms and Abbreviations (http://www.epa.gov/ceisweb1/ceishome/ceisdocs/glossary/glossary.html)

27 List of Appendices

Appendix I. PWS Location Map Appendix II. Map of Base of Eagle Sandstone (Stone, 1907) Appendix III. All Musselshell Well and Water Quality Data Appendix IV. Ground Water Level Map of Wells Completed in the Alluvium Appendix V. Water Quality Characteristics of Wells Completed in the Alluvium and From the Musselshell River Appendix VI. Ground Water Level Map of Wells Completed in the Judith River Formation Appendix VII. Water Quality Characteristics of Wells Completed in the Judith River Formation Appendix VIII. Ground Water Level Map of Wells Completed in the Claggett Shale Appendix IX. Water Quality Characteristics of Wells Completed in the Claggett Shale Appendix X. Ground Water Level Map of Wells Completed in the Eagle Formation Appendix XI. Water Quality Characteristics of Wells Completed in the Eagle Formation Appendix XII. Ryegate: Source Water Protection Plan Appendix XIII. Martinsdale Colony: Source Water Protection Plan Appendix XIV. Duncan Ranch Colony: Source Water Protection Plan Appendix XV. Harlowton: Source Water Protection Plan Appendix XVI. Springwater Colony: Source Water Protection Plan Appendix XVII. Golden Valley Colony: Source Water Protection Plan Appendix XVIII. Two Dot: Source Water Protection Plan Appendix XIX. Checkerboard: Source Water Protection Plan Appendix XX. Martinsdale WUA: Source Water Protection Plan Appendix XXI. Water Quality Characteristics from Wells with Unknown Completions

28 Appendices (continued)

Appendix XXII. Water Quality Characteristics of Wells Completed in the Belt Formation Water Quality Characteristics of Wells Completed in Assorted Formations Appendix XXIII. Time of Travel Calculations Appendix XXIV Musselshell Landsat Photo Appendix XXV Constituent Contours in mg/L Appendix XXVI. Ryegate Geologic Map Appendix XXVII. Harlowton Geologic Map Appendix XXVIII. Lavina Geologic Map

29