Summary of the Groundwater System of the Flathead Lake Basin

Summary of the Groundwater System of the Flathead Lake Basin September 30, 2011

Public Review Draft

U.S. Environmental Protection Agency Montana Operations Office 10 West 15th Street, Suite 3200 Helena, MT 59601

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Revision History Document Name Revision Release Date Revisions

Summary of the Groundwater System of the Flathead Lake Basin

1.0 July 20, 2011 Draft was sent to public entities that contributed data and information to the report.

Summary of the Groundwater System of the Flathead Lake Basin

2.0 September 2, 2011

addressed MBMG comments

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Table of Contents 1 INTRODUCTION ............................................................................................................................................ 1

2 OVERVIEW .................................................................................................................................................... 1

2.1 POPULATION AND GROUNDWATER USE .................................................................................................................... 1 2.2 GEOLOGY............................................................................................................................................................ 2 2.3 AQUIFERS ........................................................................................................................................................... 4 2.4 GROUNDWATER FLOW PATTERNS............................................................................................................................ 5 2.5 WATER LEVELS .................................................................................................................................................... 6 2.6 WATER QUALITY .................................................................................................................................................. 7

3 SPATIAL CHARACTERISTICS ........................................................................................................................... 7

3.1 KALISPELL ......................................................................................................................................................... 10 3.1.1 Evergreen Aquifer ................................................................................................................................ 10 3.1.2 East-Side Aquifers ................................................................................................................................ 10 3.1.3 Delta Aquifer ........................................................................................................................................ 10 3.1.4 Lost Creek Fan ...................................................................................................................................... 10

3.2 MISSION ........................................................................................................................................................... 13 3.3 FLATHEAD LAKE PERIMETER ................................................................................................................................. 13 3.4 SMITH .............................................................................................................................................................. 13 3.5 JOCKO .............................................................................................................................................................. 14 3.6 CORAM ............................................................................................................................................................ 14 3.7 LITTLE BITTERROOT ............................................................................................................................................. 14 3.8 SWAN .............................................................................................................................................................. 14 3.9 NORTH FORK ..................................................................................................................................................... 15 3.10 CAMAS PRAIRIE ............................................................................................................................................. 15 3.11 IRVINE FLATS ................................................................................................................................................ 15 3.12 SUMMARY.................................................................................................................................................... 16

4 GROUNDWATER QUALITY DATA ................................................................................................................. 17

4.1 LAFAVE 2004 STUDY .......................................................................................................................................... 17 4.2 OTHER STUDIES ................................................................................................................................................. 19 4.3 GROUNDWATER QUALITY DATABASE ..................................................................................................................... 19

5 REFERENCES ............................................................................................................................................... 21

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Tables Table 1. Summary of 11 groundwater subareas within the Flathead River Basin ................................ 16 Table 2. Summary of groundwater TP and nitrate data currently available in the project database ..... 20 Table 3. Summary of groundwater nitrate (mg/L) data by subbasin (LaFave et al. 2004) ................... 17 Table 4. Summary of select groundwater data in the Flathead Lake Basin (LaFave et al. 2004) ......... 18 Figures Figure 1. Groundwater use within the Flathead Basin (LaFave et al. 2004) ............................................ 2 Figure 2. Geologic map of the Flathead Lake Basin (reproduced from LaFave et al. 2004). .................. 3 Figure 3. Schematic diagram showing vertical relationships between aquifers and non-aquifers in the

Flathead Basin (reproduced from LaFave et al. 2004). ........................................................... 6 Figure 4. The 11 hydrogeologic subareas in the Flathead Lake groundwater study area (LaFave et al.

2004) ........................................................................................................................................ 8 Figure 5. Generalized geology in the Flathead Lake Basin (reproduced from LaFave et al. 2004). ........ 9 Figure 6. Potentiometric map of the Lost Creek Fan in Kalispell .......................................................... 12

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FOREWORD A series of brief technical reports have been prepared by the U.S. Environmental Protection Agency (EPA) in support of an effort by the Montana Department of Environmental Quality (DEQ) and EPA to establish Total Maximum Daily Loads (TMDLs) for nutrients and set up a water quality simulation model for the Flathead Basin. The series includes separate reports covering a broad range of topics including:

• Groundwater • Urban Stormwater Sources • Point Source Discharges • Agriculture/Irrigation • Timber Harvest • Forest Fires • Roads • Septic Systems • Lakes and Reservoirs • Existing and historic water quality in nutrient impaired waters

When combined, these technical reports are intended to define a preliminary conceptual understanding of the current water quality conditions relative to nutrients, sources of nutrients, and the ways in which water and nutrients are transported within the Basin. The information presented in this series of technical reports will be used to inform the modeling and TMDL processes. However, specific details on model setup are not discussed in the technical reports – that information will be included in the forthcoming Modeling Quality Assurance Project Plan (QAPP). It should be noted that the data and information presented in these reports reflects what was available at the time that the reports were published. It is acknowledged that in some cases, not all data could be compiled by the publication date. Additional information will be incorporated into the modeling and TMDL processes as it becomes available.

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1 INTRODUCTION

This is one of a series of brief technical reports prepared in support of an effort by the Montana Department of Environmental Quality (DEQ) and U.S. Environmental Protection Agency (EPA) to establish Total Maximum Daily Loads (TMDLs) for nutrients, sediment, and temperature and set up a water quality simulation model for the Flathead Basin. The primary purpose of this technical memorandum is to summarize the known groundwater characteristics within the Flathead Lake Basin, with a focus on how those characteristics affect surface water flows and water quality (especially nutrients). Groundwater is an important consideration in watershed modeling because surface water quality during low flow conditions is largely a function of shallow aquifer groundwater quality. Additionally, surface water hydrology is significantly impacted by groundwater characteristics. This memorandum therefore provides a general background of groundwater conditions within the Flathead Lake Basin to inform the modeling process. In addition, it serves as an inventory of the available previous studies and data that can be further studied, if necessary, during the model calibration process. Two general sources of information were relied upon in preparing this memorandum. First, previous groundwater studies of the Basin were compiled and reviewed. Much of the information in the memorandum is based on the LaFave et al. (2004) report because it provided an extensive summary of previous studies in the basin. Secondly, raw groundwater samples were obtained from the Montana Bureau of Mines and Geology Ground Water Information Center database (GWIC) and Glacier National Park and compiled into a master database. These data are briefly summarized within the memorandum and will be further processed and utilized during the modeling effort.

2 OVERVIEW

This section of the report provides an overview of the population, groundwater use, geology, general groundwater flow patterns, and water levels within the Flathead Basin.

2.1 Population and Groundwater Use

Between 1990 and 2009 the population of Flathead County increased by more than 50 percent, from 59,218 to 89,624 (U.S. Census 2009). Most of the growth has occurred in the Kalispell Valley and in the direct vicinity of Flathead Lake, neither of which is served by public water or sewer systems. The increased population has therefore led to an increased demand on private wells for drinking water and the use of septic systems for wastewater. As shown in Figure 1, groundwater in the Basin is used primarily for irrigation, industrial operations, and domestic purposes.

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Commercial, 3% Domestic,

18%

Industrial, 29%

Irrigation, 40%

Livestock, 3%

Public Water Supply, 7%

Source: LaFave et al. (2004).

Figure 1. Groundwater use within the Flathead Basin

2.2 Geology

The Flathead Lake basin is characterized by north-trending mountain ranges that are separated by down-dropped intermontane valleys. Metasedimentary rocks of the Belt Supergroup form the mountains and underlie the valleys. The Belt rocks are generally fine- grained clastic rocks (sandstone, siltstone, and mudstone) and carbonate rocks (limestone and dolomite) that have been subjected to low-grade metamorphism. The Belt rocks are well consolidated, and where exposed, they are commonly fractured. The intermontane valleys are filled with thick sequences of Tertiary sediments, unconsolidated glacial or glacial-lake deposits, and post-glacial alluvial sediments. There are few surface exposures of Tertiary sedimentary rocks in Flathead basin. Notable outcrops occur along the North Fork of the Flathead River valley and near Coram. Other Tertiary deposits are exposed locally and buried at depth in the Jocko, Mission, Irvine Flats, Little Bitterroot, and the Camas Prairie areas. The advance and retreat of glaciers deposited materials that cover most Tertiary deposits, and some Belt Supergroup rocks. The Polson moraine, a prominent east-west ridge between Kerr Dam and the Mission Range, marks the terminus of the last glacial advance. South of Polson, the valleys were flooded by Glacial Lake Missoula, a temporary lake formed by an ice dam near the present Montana/Idaho border. The occupation of the areas north of the Polson moraine by glacial ice and areas to the south by Glacial Lake Missoula led to generally different glacial sedimentary sequences north and south of the Polson moraine. Since the retreat of glacial ice, modern streams have deposited alluvium along their channels and floodplains. Most stream valleys in the area are lined with alluvial materials that range from 10 to several 10's of feet in thickness. A general geologic map of the basin is shown in Figure 2.

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Reproduced from LaFave et al. (2004).

Figure 2. Geologic map of the Flathead Lake Basin.

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2.3 Aquifers

All of the major communities (except for Whitefish) rely on groundwater from local aquifers as their municipal water supply, most rural residences also rely on groundwater, and groundwater is frequently used for irrigation (Patton et al. 2003). An in-depth discussion of regional groundwater is presented in LaFave et al (2004) and a synopsis is presented in Patton et al. (2003). There are five aquifer types whose hydrogeologic settings vary greatly from one another:

Shallow alluvial aquifers are present in all major valleys. They are important sources of water locally but are generally limited in their areal extent to surficial deposits associated with modern rivers or streams and to glacial outwash. Because they are shallow and areally limited, these aquifers are often susceptible to surface sources of contamination and drought. Within the study area, about 3,400 wells have been completed in shallow aquifers; however, the rate of new development in shallow aquifers in some subareas has declined in favor of the more deeply buried aquifers.

Intermediate alluvial aquifers, defined as distinct water-bearing sand and gravel deposits separated above and below by confining units, occur in all the subareas, generally between 50 and 100 feet below the land surface. These aquifers are local features of variable thickness and are discontinuous across large distances. In some places, intermediate aquifers interfinger with or are hydraulically connected to other intermediate aquifers or to deep alluvial aquifers. About 3,800 wells have been completed in intermediate aquifers, mostly within the Kalispell and Mission subareas.

Deep alluvial aquifers occur as areally extensive, thick deposits of sand and gravel that are generally found beneath confining units and are between 75 and 300 feet below the land surface. Deep alluvial aquifers (together with intermediate aquifers) are the most utilized aquifers in the Flathead Lake area and form the major ground-water flow system in many subareas. In the Kalispell and Mission subareas the deep alluvial aquifers are the most productive sources of ground water; most of the high-capacity irrigation and water-supply wells are among the more than 5,000 wells completed in these aquifers. In many areas the deep alluvial aquifers appear to be well protected from surficial contamination sources by nearly continuous confining units of till and glacial-lake deposits. However in localized areas, such as near the Lost Creek fan northwest of Kalispell, where the protective cover may be missing, deep alluvial aquifers may be susceptible to contamination.

Tertiary aquifers (tertiary sediment or sedimentary rock) are rare and occur in the North Fork Flathead River and Coram areas. Tertiary sediments occur at great depths, but the aquifers (in the North Fork Flathead River and Coram areas) are relatively close to the surface. One percent of the wells in the Flathead area lie in Tertiary aquifers. The yields are less than half the average yields for wells in the other aquifers.

Fractured bedrock aquifers occur along valley margins and the Flathead Lake perimeter. The fractures vary widely in number, size and orientation over short distances which results in a large variation of water yield from one location to the next (LaFave et al. 2004).

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The most widely used aquifers in the watershed are intermediate or deep alluvial aquifers lying in unconsolidated Quaternary deposits (LaFave et al. 2004). However, from a watershed modeling perspective, the shallow aquifers have the greatest impact on surface water quality and are thus of most interest for this memorandum.

2.4 Groundwater Flow Patterns

Groundwater flow tends to follow surface topography. However, groundwater flow in the Evergreen aquifers underlying the Flathead Valley trends north to south (Craft and Ellis 2004). The aquifers in the Flathead Lake Basin form both a shallow groundwater flow system and a deep groundwater flow system (Makepeace and Mladenich 1996). The shallow groundwater flow system is limited to single shallow aquifers. Flow systems in the shallow aquifers tend to be local with water moving from topographic highs (i.e., recharge areas) to nearby lakes and streams (i.e., discharge areas). Groundwater flows from high altitudes (near Kalispell and Mission Mountains) in the mountain bedrock aquifers along the topographic high points towards discharge areas in the deep and intermediate aquifers to form the deep groundwater flow system. In general, the shallow and deep flow systems are separated by low permeability confining units, but the separation is not present in all areas and the shallow and deep systems can be hydraulically connected (LaFave et al. 2004). Recharge of groundwater occurs through direct infiltration of precipitation, leakage from irrigation ditches, and from stream losses (LaFave et al. 2004). Shallow aquifers can serve as sources of recharge to the deeper aquifers where they are hydraulically connected. Potentiometric-surface mapping shows that groundwater in the bedrock along valleys is hydraulically connected to intermediate and deep aquifers within the valleys. The hydraulic connections between the bedrock aquifers via fracture systems to the deeply buried valley deposits are an important source of groundwater recharge to the valleys (LaFave et al. 2004a). A schematic diagram showing vertical relationships between aquifers and non-aquifers in the Flathead Basin is shown in Figure 3.

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Figure 3. Schematic diagram showing vertical relationships between aquifers and non-aquifers in the Flathead Basin.

According to LaFave et al. (2004) approximately half of the annual precipitation in the watershed (18 inches) is lost to evapotranspiration. Evapotranspiration includes crop uptake of water, vegetative uptake, and evaporation from surface water bodies including Flathead Lake. Discharge of water from shallow aquifers occurs through springs and seeps along valley bottoms, transfer to perennial streams, transpiration by plants, and pumping from wells (LaFave et al. 2004).

2.5 Water Levels

Water level fluctuations in wells in the Flathead Lake area reflect changes in groundwater storage and are primarily controlled by spring runoff, seasonal stream flow, pumping, and recharge from irrigation practices. Wells affected by runoff have high levels in the spring which decline during summer and fall and reach their lowest levels in winter. Many wells in shallow aquifers through the Flathead Lake basin display this runoff response. Wells in deep confined, to semi-confined aquifers affected by irrigation pumping display a sharp drop in levels in the summer and recover during the fall and winter months. This response is observed in the deep alluvial aquifers in the Kalispell, Mission, and Little Bitterroot subareas. Wells that respond to irrigation recharge display water levels that generally rise in the spring, remain elevated throughout the summer and into autumn, and fall once the irrigation ditches are "turned off" or are no longer used, water levels will decline until the next spring when the irrigation seasons starts over; these wells are primarily located in the shallow aquifers near irrigation canals in the Mission and Jocko subareas.

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2.6 Water Quality

Flathead Lake area groundwater is high quality and is generally suitable for domestic consumption, crop irrigation, and most other uses. Except for a slightly different type of water in the Lonepine aquifer of the Little Bitterroot subarea, little difference can be found between the chemical make-up of groundwater from the shallow alluvial, intermediate alluvial, deep alluvial, and bedrock aquifers. The predominant ions in water from all the aquifers (with the exception of the Lonepine) are calcium and bicarbonate. The ground water is characterized by dissolved constituents of less than 500 milligrams per liter (mg/L). Section 4 provides a summary of available water quality data for groundwater within the Basin.

3 SPATIAL CHARACTERISTICS

The Flathead Lake Basin covers an area of approximately 8600 square miles. Although the general geological framework of the valleys is the Basin is similar, the nature and distribution of the aquifers vary. LaFave et al. 2004 divided the basin into 11 subareas and this report follows the same convention (Figure 4). Shallow aquifer groundwater data are of specific interest because of the potential impact on nutrient levels in nearby surface waters. Shallow aquifers are susceptible to surface activity, including contamination and climatic effects. Shallow aquifers are present in most of the subareas and generally occur in alluvium along stream valleys and in glacial outwash deposits (Figure 5). Important shallow aquifers in the watershed include the Evergreen aquifer in the Kalispell Subarea, the Mud and Post Creek aquifers in the Mission subarea, the Jocko River Alluvium in the Jocko Subarea, and the Flathead River alluvium downstream of Kerr Dam.

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Source: LaFave et al. (2004).

Figure 4. The 11 hydrogeologic subareas in the Flathead Lake groundwater study area.

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Figure 5. Generalized geology in the Flathead Lake Basin.

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3.1 Kalispell

The Kalispell subarea is located between the Whitefish Range to the north and the Swan and Salish Ranges to the east and west; at 700 square miles it is the largest subarea in the Flathead Lake Basin. Several distinct aquifer systems exist within the subarea and are summarized in subsections 3.1.1 through 3.1.4. In 2004 there were 10,291 wells in the subarea, the majority of which obtain water from intermediate, deep alluvial, and bedrock aquifers. There are two general water-level patterns in the Kalispell subarea. Levels in the shallow aquifers rise in the spring and early summer in response to runoff and then drop in the late summer, fall, and winter. Water levels in the deep flow system drop sharply in the late summer due to well pumping and recover quickly in the fall, remaining stable through the winter.

3.1.1 Evergreen Aquifer

The Evergreen aquifer is a shallow aquifer that sits atop low-permeability silt and clay. The aquifer extends over approximately 40 square miles between the Whitefish and Flathead Rivers. Well depths are generally around 25 feet and groundwater within the Evergreen aquifer flows south toward the confluence of the Whitefish and Flathead Rivers (LaFave et al. 2004). King (1988) reported that groundwater quality in the Evergreen aquifer is impacted by urban activity, with nitrate, phosphorus and total dissolved solids concentrations higher potentially due to septic contamination.

3.1.2 East-Side Aquifers

The thickness and extent of the aquifers east of Kalispell is variable and not well defined. The aquifers are located in sand and glacial outwash mixed with glacial-lake deposits. Groundwater flows generally from the Swan Range toward the Flathead River. These shallow aquifers appear to be hydraulically connected to and help to recharge the deep groundwater flow system. The median reported water level is 20 feet below ground surface.

3.1.3 Delta Aquifer

The Delta Aquifer is hydraulically separated from the Evergreen and East-Side aquifers (Konizeski et al. 1968). The aquifer lies between the north end of Flathead Lake and the Flathead River. Flow is dependent on seasonal stages in the Flathead River and lake. When lake levels are low groundwater flows from the aquifer to the river and the lake; when lake and river levels are high, groundwater flows from the river and lake to the aquifer (Konizeski et al. 1968). The median reported depth to the water table is 16 feet.

3.1.4 Lost Creek Fan

The Lost Creek Aquifer near Kalispell covers an area of approximately 8 square miles. Groundwater flow is generally from west to east. The Lost Creek Aquifer may be connected to the underlying deep alluvium, making it a possible important recharge source for the deep flow system. Elevated nitrate concentrations have been found in the Lost Creek Fan, indicating that groundwater has been impacted by surface contamination.

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Water level data in 2007 suggested that pond locations on the toe of the alluvial fan are connected to groundwater. The potentiometric map of this fan created in 2007 is located below (Tetra Tech 2008). In general, groundwater flow in December 2007 followed the topographic slope of the alluvial fan; to the northeast in the northern portion of the fan, to the east in the central portion of the fan, and to the southeast in the southern portion of the fan. The study found that the hydraulic gradient increases with increasing topographic slope (Tetra Tech 2008). Elevated nitrate levels in the Lost Creek Fan were first noted by the Montana Bureau of Mines and Geology (MBMG) in 1996 with nitrate measured above 5 mg/L. Follow-up sampling in 2002 detected nitrate concentrations in some residential wells as high as 40 mg/L and ten domestic wells were found to have nitrate concentrations exceeding 10 mg/L in a 2007 study (Alve 2007). The highest concentrations were observed at the northwest corner of the intersection of Farm-to-Market Road and Church Drive and north of Church Drive and, in general, elevated nitrate was found in the shallow wells and not in the deep wells. Total phosphorus (TP) groundwater concentrations ranged from below detection limits to 0.04 mg/L. Three-fourths of the shallow wells that were sampled had non-detectable levels of TP (Alvey 2007). Several potential sources of nitrates exist near the Lost Creek Fan, including the use of nitrogen-based fertilizers, dairy operations, cattle feedlots, the spreading of septic and dairy waste, septic systems, soil disturbance, and poorly constructed and sealed wells that can act as conduits for the movement of surface nitrates to groundwater (Alvey 2007).

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Figure 6. Potentiometric map of the Lost Creek Fan in Kalispell.

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3.2 Mission

The Mission subarea includes the valley bounded by the Salish Mountains to the west, the Mission Range to the east, and the Jocko Hills to the south. The northern boundary of the Mission subarea is marked by Flathead Lake and the Polson moraine. The Mission subarea contained 2,011 wells in 2004, the majority of which lie in shallow, intermediate, and deep alluvial aquifers. Water levels in the Mission subarea vary depending on location, while following a similar seasonal pattern. Water levels in the shallow aquifers near St. Ignatius typically peak in the late summer or early fall, decline during the winter, and reach minimum levels in the early spring. This pattern and data on irrigation ditch usage suggests that irrigation water is an important source of recharge. Water levels in another shallow aquifer associated with Dry Creek peak in mid-August and reach a low in April. This pattern suggests that infiltration from Dry Creek controls the magnitude and timing of groundwater levels in the aquifer. Water levels in the deep flow groundwater system of the Mission subarea seem to be influenced by seasonal pumping. Nitrate concentrations are generally low, averaging 0.88 mg/L for 91 samples (LaFave et al. 2004). Boettcher (1982) found that groundwater recharge in the central part of the Flathead Indian reservation is primarily from runoff from the mountains but also precipitation, and seepage loss from unlined irrigation ditches, discharge of groundwater occurs through springs, evapotranspiration, well pumping, and groundwater inflow to the Flathead River.

3.3 Flathead Lake Perimeter

The Flathead Lake Perimeter subarea is the area along the east and west edges of Flathead Lake. The Flathead Lake Perimeter contained 2021 wells in 2004. These aquifers likely depend on nearby bedrock aquifers for recharge. Bedrock aquifers are sensitive to drought and pumping because of their small storage capacities. Groundwater quality is reported to be good, with only one sample from 1984 above 10 mg/L for nitrate (LaFave et al. 2004).

3.4 Smith

The Smith Subarea is drained by Ashley Creek which flows east towards Kalispell. The middle of the subarea contains the Little Bitterroot River and the western portion of the watershed drains McGregor Creek. Shallow aquifers in the subarea are located near Smith Lake, Ashley Lake, and Marion. There were 680 wells in the Smith subarea in 2004, sixty percent of which were installed after 1990. Most of the wells are in bedrock and shallow alluvium and are sensitive to surface contamination because water moves quickly through the bedrock cracks and fractures and the shallow aquifers are unconfined. Nitrate concentrations from five samples in the Smith subarea were low with a maximum recorded sample at 0.35 mg/L (LaFave et al. 2004).

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3.5 Jocko

The Jocko Subarea is located in the northwest trending valley of the Jocko River. The northeast border is a steep escarpment at the foot of the Jocko Hills and the southwest/southeast border consists of a series of low hills. There were 661 well in the subarea in 2004 and sand and gravel accumulation was documented in more than half the shallow wells. The median depth to the shallow aquifer is 26 feet. Groundwater flow in the Jocko subarea is controlled by topography, flowing away from the valley margins toward the Jocko River. Water quality samples indicate that water quality in the Jocko Subarea is good. None of the samples exceed USEPA standards and water from bedrock was the least mineralized of the 11 Flathead subareas. Average nitrate concentrations from 28 samples in the subarea were 0.28 mg/L with a maximum recorded value of 1.69 mg/L (LaFave et al. 2004).

3.6 Coram

The Coram subarea is in the Flathead River valley east of Bad Rock Canyon, south of the Apgar Mountains and Glacier National Park. The subarea includes the south and north Fork Flathead River valleys and the Middle Fork Flathead River valley. The subarea contained 571 wells in 2004 and the median water level of shallow aquifers in the basin is 15 feet. Although a significant number of permanent and seasonal homes were build in the subarea in the late 1990s, groundwater quality was found to be good with all nitrate samples below 0.90 mg/L (LaFave et al. 2004).

3.7 Little Bitterroot

The Little Bitterroot subarea includes the Little Bitterroot river valley and extends to the northwest through Hot Springs to the Little Bitterroot Canyon near Niarada. Shallow alluvium lies along the Little Bitterroot River valley and its tributaries, although it is not thick or extensive. A total of 661 wells (mostly in the Lone Pine aquifer, which is deep and confined) were found in the Little Bitterroot subarea in 2004. Groundwater quality in the Lone Pine aquifer is unique. The median concentrations of chloride and sodium are ten times greater than those in the other subareas, while calcium and magnesium concentrations are much lower. Although elevated, none of the chloride or sodium water quality samples exceeded standards. However, several samples did exceed fluoride and arsenic standards, especially around the geothermal area at Wild Horse Hot Springs. Nitrate levels in Little Bitterroot were not elevated, the highest recorded sample was 1.90 mg/L (LaFave et al. 2004).

3.8 Swan

The Swan subarea contains the northern portion of the Seeley-Swan Valley in Lake County and the southern end of Swan Lake. The Seeley-Swan Valley is a narrow fault-bounded valley lying

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between the Swan and Mission Ranges. There were 278 wells in the subarea in 2004 and most were less than 200 feet deep. The shallow aquifers in the subarea lie in sand and gravel near the surface along Swan River and in some glacial outwash areas. The median thickness of the aquifer is 20 feet and till is common at the surface. Groundwater flow in the subarea is from higher elevations toward the low valley center. Water levels in the shallow aquifers are likely controlled by river stage. LaFave et al. (2004) reported elevated nitrate concentrations (4.8 and 4.9 mg/L) near Swan Lake, suggesting a potential surficial source of contamination.

3.9 North Fork

The North Fork subarea extends from the Apgar Mountains northwest to Canada. The subarea is bordered by the Whitefish Range in the southwest and the Livingston Range foothills in Glacier National Park in the northeast. The bedrock aquifers in the North Fork subarea lie in the mountains and the valley contains Tertiary sediments covered by deep alluvium, till, and shallow alluvium which is 300 feet thick in places. A layer of Tertiary siltstone, shale, sandstone, and conglomerate is common within 100 feet of the surface. The shallow aquifers in the subarea lie near the river floodplains and glacial outwash in sand and gravel deposits which have a thickness of 34 feet. The North Fork subarea is unique in that aquifers lying in Tertiary sedimentary rocks are an important source of groundwater. No nitrate was detected in water quality samples of the North Fork subarea (LaFave et al. 2004). The Canadian portion of the North Fork was studied by Appleman et al. (1990), who measured instantaneous discharge to determine the fate of groundwater in alluvial aquifers. This study found that in the Howell Creek valley alluvial deposits discharge to Howell Creek whereas the Flathead River downstream of Couldrey Creek discharges into the alluvial flood-plain.

3.10 Camas Prairie

The Camas Prairie subarea is a north-south oriented elliptical basin drained by Camas Creek in the southeast corner of the Flathead Lake Basin. There were 82 wells in the Camas Prairie Subarea in 2004 and the majority are in shallow aquifers and bedrock aquifers. Water quality samples showed similar water quality as other areas west of Flathead Lake. Nitrate concentrations for 10 samples ranged from below detection to 3.60 mg/L (LaFave et al. 2004).

3.11 Irvine Flats

The Irvine Flats subarea is a small valley drained by White Earth Creek west of Polson. White Earth Creek flows into the Flathead River downstream of Kerr Dam. Shallow aquifers in the subarea are found in limited areas of sheetwash and along small river floodplains which rest on Glacial Lake Missoula sediments. There were 77 wells in the subarea in 2004 but no summary of

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groundwater quality data is available due to only 4 samples being obtained in the subarea (LaFave et al. 2004).

3.12 Summary

A summary of the general characteristics of the 11 groundwater subareas within the Flathead River Basin is presented in Table 1.

Table 1. Summary of 11 groundwater subareas within the Flathead River Basin

Subarea # Wells in 2004 Drained By Majority Well Aquifer Type Use

Kalispell 10291 Flathead River and tributaries deep, shallow, intermediate, tertiary

Mission 2011 Flathead River shallow Flathead Lake Perimeter 2021 Flathead Lake shallow & bedrock

Smith 680 Ashley Creek bedrock and shallow

Jocko 661 Jocko River shallow

Coram 571 Flathead River Forks shallow

Little Bitterroot 661 Little Bitterroot deep

Swan 278 Swan shallow

North Fork 147 Howell Creek and Flathead River alluvial floodplain tertiary

Camas Prairie 82 Camas Creek shallow and bedrock

Irvine Flats 77 White Earth Creek shallow

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4 GROUNDWATER QUALITY DATA

This section of the report provides a summary of the known groundwater quality data within the Flathead Lake Basin.

4.1 LaFave 2004 Study

The quality of groundwater in the Flathead Basin was summarized by LaFave et al. (2004). The data summaries from that report are provided in Table 2 and Table 3 and include data outside the project study area. Table 2 indicates that average nitrate concentrations are the greatest in the Swan subarea and Table 3 presents the range in concentrations for a variety of other parameters. Anecdotal summaries of water quality within each of the 11 subareas are provided in Table 4.

Table 2. Summary of groundwater nitrate (mg/L) data by subarea as presented in LaFave et al. (2004)

Subarea First

sample Last

sample No. of

samples Average Minimum Maximum Camas Prairie 9/17/75 9/24/96 10 0.57 0.02 3.60 Coram 5/21/81 8/24/96 12 0.20 0.05 0.90 Flathead Lake Perimeter 9/17/75 11/7/96 32 0.85 0.02 12.21 Irvine Flats 9/16/75 8/9/85 4 0.79 0.03 2.43 Jocko 9/18/75 11/14/96 28 0.28 0.02 1.69 Kalispell 1/2/00 5/29/00 149 1.23 0.02 18.90 Little Bitterroot 8/27/75 5/27/00 78 0.28 0.01 1.90 Mission 1/2/00 11/8/96 91 0.88 0.02 10.60 North Fork 7/27/96 7/28/96 3 0.18 0.05 0.25 Smith 10/18/95 10/29/96 5 0.19 0.05 0.35 Swan 4/18/94 5/29/00 9 1.27 0.09 4.90

Source: LaFave et al. (2004). * Detection limits varied from 0.05 to 0.25 depending on sampling effort. Samples below the detection limit were treated as being at the detection limit in this summary.

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Table 3. Summary of select groundwater data in the Flathead Lake Basin as presented in LaFave et al. (2004). Samples were collected between 1975 and 2000

Parameter No. of samples Average Minimum Maximum

Calcium (mg/L) 424 38.9 0.1 181.0

Chloride (mg/L) 425 7.0 0.0 90.0

Carbonate (mg/L) 425 1.0 0.0 60.0

Hardness (mg/L) 424 160.4 1.5 662.3

Magnesium (mg/L) 424 15.1 0.1 59.5

Manganese (mg/L) 425 0.3 0.0 36.0

Sodium (mg/L) 425 31.7 0.7 402.0

Nitrate (mg/L) 425 0.8 0.0 18.9

Sulfate (mg/L) 425 11.5 0.0 360.8

Total Dissolved Solids (mg/L) 425 248.9 38.4 1,073.9

Source: LaFave et al. (2004) * Samples below the detection limit were treated as being at the detection limit in this summary.

Table 4. Summary of groundwater data by subarea in the Flathead Lake Basin as presented in LaFave et al. (2004). Samples were collected between 1975 and 2000

Subarea Water Quality Characteristics

Kalispell generally high quality; nitrate ranged from 0.05 to 3.6 mg/L; phosphorus generally less than 0.2 mg/L; groundwater nutrients a localized problem around Whitefish Lake; higher values were detected in the Lost Creek Fan

Mission nitrate concentrations generally low, averaging 0.88 mg/L for 91 samples Flathead Lake Perimeter

groundwater quality reported to be good, with only one sample from 1984 above 10 mg/L for nitrate; phosphorus reported to be highest within the Basin

Smith nitrate concentrations from five samples low with a maximum of 0.35 mg/L

Jocko average nitrate concentrations from 28 samples were 0.28 mg/L with a maximum recorded value of 1.69 mg/L

Coram all nitrate samples below 0.90 mg/L

Little Bitterroot

median concentrations of chloride and sodium ten times greater than those in the other subareas, while calcium and magnesium concentrations are much lower; several samples exceed fluoride and arsenic standards, especially around the geothermal area at Wild Horse Hot Springs; nitrate levels not elevated, with maximum of 1.90 mg/L

Swan elevated nitrate concentrations (4.8 and 4.9 mg/L) observed near Swan Lake, suggesting a potential source of contamination

North Fork not available

Camas Prairie similar water quality as other areas west of Flathead Lake; nitrate concentrations for 10 samples ranged from below detection to 3.60 mg/L

Irvine Flats not available

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4.2 Other Studies

A variety of other studies relevant to groundwater quality have been conducted in the Basin and are summarized in this section. In 2002 and 2003 MBMG analyzed samples at 38 wells and 2 springs in the shallow aquifers surrounding Flathead Lake. Nitrate was detected at least once in 26 of the wells but was not detected in the springs. Concentrations in the wells ranged from <0.5 mg/L to 8.5 mg/L. Orthophosphate concentrations were below the detection limit in all samples. Eight of the wells had nitrate concentrations that exceeded the typical 2.0 mg/L associated with background concentrations for shallow groundwater in undeveloped areas (McDonald and LaFave, 2003). Sampling by the Flathead Lake Biological Station from 2002 and 2003 of groundwater wells in and around Flathead Lake revealed no significant temporal trend in soluble reactive phosphorus concentrations. However, nitrate concentrations were found to be increasing. Values were highest north of Flathead Lake in the Evergreen Area compared to levels west of the Flathead River (Pothole Lakes) and around the Lakes Perimeter. Nitrate concentrations from 1968 in six wells near the Evergreen area ranged from below detection to 0.72 mg/L. In 1976 28 wells were sampled near Evergreen and the reported median concentrations of nitrate were 0.73 mg/L. In 1984 and 1985 Noble and Stanford sampled 15 wells with median nitrate concentrations of 0.83 mg/L. In the Craft and Ellis study, the median of nitrate concentrations measured 0.94 mg/L. SRP was reported to be the highest in wells within the Flathead Lake Perimeter subarea (Craft and Ellis 2004). Craft and Ellis (2004) were not able to make conclusions about groundwater nutrient loads and recommended combining the nutrient data from their report with data from a hydrologic flux model. They also recommended additional sampling of groundwater discharge and nutrient concentrations.

4.3 Groundwater Quality Database

To support the watershed modeling effort for the Flathead Lake Basin, a groundwater quality database has been created by compiling available online data from GWIC and Glacier National Park. These data were formatted to match data fields from the Flathead master water quality database (parameter codes added, source noted, etc.). A summary of all of the TP and nitrate data in the database is included below in Table 5 and Table 6 summarizes the data according to the 11 subareas. These data, in combination with the data and information discussed in Sections 4.1 and 4.2 and surface water quality samples, will be used to inform the selection of groundwater nutrient concentrations for the modeling effort. It is apparent from the tables that data are limited or non-existent for certain subareas and thus some assumptions will need to made during the modeling process.

20

Table 5. Summary of groundwater TP and nitrate data currently available in the project database

Parameter First sample

Last sample

No. of samples Average Minimum Maximum

Total Phosphorus (mg/L) 7/2/1980 6/15/2007 32 0.04 0.003 0.36

Dissolved Nitrate (mg/l) 10/1/1958 8/23/2007 695 1.53 0.01 66

Total Nitrate (mg/l) 8/26/1975 6/5/2001 88 0.35 0.01 2.51

Table 6. Summary of groundwater TP (mg/L) and nitrate (mg/L) data currently available in the project database by LaFave subarea

Subarea Name Parameter First

sample Last

sample No. of

samples Average Minimum Maximum

Coram

Dissolved Nitrate 5/28/1980 8/24/1996 41 0.19 0.03 0.9

Total Nitrate 5/28/1980 9/17/1981 39 0.19 0.05 0.56

Total Phosphorus 7/2/1980 9/25/1980 18 0.03 0 0.13

Flathead Lake Perimeter


Total Nitrate 8/26/1975 6/5/2001 6 0.5 0.02 2.17

Total Phosphorus 4/21/2007 6/15/2007 3 0.01 0.01 0.02

Kalispell

Dissolved Nitrate 10/1/1958 8/23/2007 410 2.09 0.01 66

Total Nitrate 6/11/1988 6/12/1988 11 1.15 0.2 2.51


Lost Creek Fan


North Fork Dissolved Nitrate 7/27/1996 7/28/1996 3 0.18 0.05 0.25

Not Assigned


Total Nitrate 5/29/1980 9/15/1981 30 0.24 0.01 1.1


Swan


Total Nitrate 1/24/1994 4/4/2001 2 0.35 0.19 0.5

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5 REFERENCES

Alvey, L. 2007. Report of Findings for the Lost Creek Fan Nitrate Investigation August-September 2006. Groundwater Remediation Program/Site Response Section/Remediation Division. Montana Department of Environmental Quality.

Appleman, R. A., R. A. Noble, J. L. Sonderegger, Jack A. Stanford, Bonnie K. Ellis, and R.,

Hauer. 1990. Baseline Water-Quality Conditions for the North Fork Flathead River, British Columbia and Montana. Open-File Report 233. Montana Bureau of Mines and Geology, A Department of the Montana College of Mineral Science and Technology, Butte, MT.

Baxter, C. V., and F. R. Hauer. 2000. Geomorphology, Hyporheic Exchange, and Selection of

Spawning Habitat by Bull Trout (Salvelinus confluentus). Can. J. Fish. Aquat. Sci. 57: 1470-1481 (2000).

Boettcher, A. J. 1982. Ground-Water Resources in the Central Part of the Flathead Indian

Reservation, Northwestern Montana. MBMG Memoir 48. Montana Bureau of Mines and Geology, A Department of Montana College of Mineral Science and Technology, Butte, MT.

Coffin, D.L., A. Brietkrietz, and R.G. McMurtrey. 1971. Surficial Geology and Water Resources

of the Tobacco and Upper Stillwater River Valleys, Northwestern Montana. Bulletin 81. Montana Bureau of Mines and Geology, Butte, MT.

Craft, J. A., and B. K. Ellis. 2004. Groundwater Nutrient Assessment of Selected Shallow

Aquifers in the North Flathead Valley and Flathead Lake Perimeter Area, Northwest Montana. Open File Report Number 180-04. Prepared for Flathead Basin Commission, Kalispell, Montana by Flathead Lake Biological Station, The University of Montana, Polson, MT. 42 pp.

Jourdonnais, J. H., J. A. Stanford, F. R. Hauer, and R. A. Noble. 1986. Investigation of Septic

Contaminated Groundwater Seepage as a Nutrient Source to Whitefish Lake, Montana. Open File Report. Flathead Biological Station, University of Montana, Bigfork Montana and Montana Bureau of Mines and Geology, Montana College of Mineral Science and Technology, Kalispell, MT.

King, J. B., 1988. Hydrogeologic Analysis of Septic System Nutrient Attenuation Efficiencies in

the Evergreen Area, Montana. MBMG Open-File Report 205. Montana Bureau of Mines and Geology, A Department of Montana College of Mineral Science and Technology, Butte MT.

Konizeski, R. L. A. Brietkrietz and R. G. McMurtrey. 1968. Geology and groundwater resources

of the Kalispell valley, northwestern Montana: Montana Bureau of Mines and Geology Bulletin 68, 42 pp

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LaFave, J. I., L. N. Smith, and T. W. Patton. 2004. Ground-Water Resources of the Flathead Lake Area: Flathead, Lake, Missoula, and Sanders Counties, Montana. Part A – Descriptive Overview and Water-Quality Data. Montana Bureau of Mines and Geology, Butte, MT.

LaFave, J. I. 2004a. Potentiometric Surface Map of the Southern Part of the Flathead Lake Area,

Lake, Missoula, Sanders Counties, Montana. Montana Ground-Water Assessment Atlas No. 2, Part B, Map 4. Montana Bureau of Mines and Geology, A Department of Montana Tech of The University of Montana, Butte, MT.

Makepeace, S. and B. Mlandenich. 1996. Contribution of Nearshore Nutrient Loads to Flathead

Lake, Prepared for the USEPA, TMDL Grant # X99818401-0, Prepared by CSKT Natural Resources Department.

McDonald, C. and J. I. LaFave. 2003. Ground-Water Assessment of Selected Shallow Aquifers in

the North Flathead Valley and Flathead Lake Perimeter Area, Northwest Montana. MBMG Open-File Report 492. Funded by U.S. Environmental Protection Agency 319 Grant (administered by the Flathead Basin Commission through the Montana Department of Environmental Quality).

Patton, T.W., L.N. Smith, and J.I. LaFave. 2003. Ground-Water Resources of the Flathead Lake

Area: Flathead, Lake, Sanders, and Missoula Counties, Montana. Information Pamphlet No. 4. Montana Bureau of Mines and Geology. January 2003.

Tetra Tech. 2008. Lost Creek Fan Shallow Aquifer Potentiometric Surface Mapping Report

Northwest of Kalispell, Montana. Tetra Tech Project No. 8570003. Prepared for Ms. Laura Alvey Montana Department of Environmental Quality Remediation Division.

U.S. Census. 2009. U.S. Census Bureau, 2008 Population Estimates, Census 2000, 1990 Census. <http://www.census.gov/> Accessed June 2, 2009.

Uthman, W., K. Wrren, and M. Corbett. 2000. A Reconnaissance Groundwater Investigation in

the Upper Flathead River Valley Area. Montana Bureau of Mines and Geology Open-File Report 414. Montana Department of Natural Resources and Conservation. Helena, MT.

Summary of the Groundwater System of the Flathead Lake Basin

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