Magnolia Estates Public Water Supply (serving: Magnolia Estates Subdivision )
PWS ID # MT0004021
SOURCE WATER DELINEATION AND ASSESSMENT REPORT
Date of Report: April 2008
Report Prepared For: Magnolia Estates Jeff McCleary, Operator Barbara Howell, Administrative Contact 7501 Gardenia Drive Missoula, Montana 59808
Report Prepared By: Jeffrey Frank Herrick Source Water Protection Program Montana Department of Environmental Quality P.O. Box 200901 Helena, Montana 59620-0901 Magnolia Estates PWS # MT0004021 Draft SWDAR TABLE OF CONTENTS
TABLE OF CONTENTS ...... II INTRODUCTION...... 4 PURPOSE ...... 4 LIMITATIONS...... 4 BACKGROUND ...... 5 THE COMMUNITY...... 5 GEOGRAPHIC SETTING ...... 5 Table 1. Climatic Data ...... 5 DESCRIPTION OF THE SOURCE WATER ...... 5 THE PUBLIC WATER SUPPLY ...... 6 Table 2. PWS Facilities and Well Information...... 7 WATER QUALITY ...... 7 DELINEATION ...... 8 DELINEATION PROCESS...... 8 HYDROGEOLOGIC CONDITIONS...... 8 Table 3. Sources of Hydrogeologic Information ...... 8 Geologic Setting...... 9 Aquifer Properties...... 10 Table 4. Summary of Aquifer Test Results ...... 11 PWS SOURCE INFORMATION ...... 12 Table 5. PWS Source/Well Information ...... 12 Table 6. Summary of Inputs and Results for Time-of-Travel Calculation...... 13 DELINEATION RESULTS...... 13 LIMITING FACTORS ...... 13 INVENTORY ...... 15 INVENTORY METHOD...... 15 INVENTORY RESULTS...... 16 Control Zone ...... 16 Inventory Region...... 16 Recharge Region...... 17 Table 7. Potential Contaminant Sources...... 17 INVENTORY UPDATE...... 18 INVENTORY LIMITATIONS ...... 18 SUSCEPTIBILITY ASSESSMENT ...... 19 GENERAL DISCUSSION ...... 19 HAZARD DETERMINATION ...... 19 Table 8. Determination of Hazard for potential contaminant sources...... 19 Table 9. Susceptibility, Based on Hazard and Barriers ...... 20 DISCUSSION OF SUSCEPTIBILITY ...... 20
Page ii of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR SUMMARY OF SUSCEPTIBILITY ASSESSMENT ...... 20 Table 10. Susceptibility Assessment...... 22 REFERENCES...... 27 GLOSSARY...... 29 FIGURES...... 31 APPENDICES...... 32 APPENDIX A...... 32 DEQ PWS’s Database Output (for Magnolia Estates)...... 32 List of PWS Facilities...... 32 Sampling Schedule...... 32 Water Quality Data ...... 32 APPENDIX B...... 33 Sanitary Surveys...... 33 Well Log Information...... 33 Other Relevant Well Information...... 33 APPENDIX C...... 34 Concurrence Letter ...... 34 APPENDIX D...... 35 PWS-6 Report / SWDAR for Flying H Event Center (2007)...... 35
Page iii of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR INTRODUCTION
This Delineation and Assessment Report was completed by Jeffrey Frank Herrick, a hydrogeologist with the Montana Department of Environmental Quality (DEQ) – Source Water Protection Program (SWPP). This report was prepared for:
Magnolia Estates – Public Water Supply providing water to the Magnolia Estates Subdivision 7501 Gardenia Drive Missoula, Montana 59808
Purpose This report is intended to meet the technical requirements for the completion of the delineation and assessment report for the Magnolia Estates PWS (public water supply), which provides water to Magnolia Estates subdivision. This is required by the Montana Source Water Protection Program (DEQ, 1999) and the federal Safe Drinking Water Act (SDWA) Amendments of 1996 (P.L. 104-182).
The Montana Source Water Protection Program is intended to be a practical and cost-effective approach to protect public drinking water supplies from contamination. A major component of the Montana Source Water Protection Program is “delineation and assessment”. Delineation is a process of mapping source water protection areas, which contribute water used for drinking. Assessment involves identifying locations or regions in source water protection areas where contaminants may be generated, stored, or transported, and then determining the relative potential for contamination of drinking water by these sources. The primary purpose of this Source Water Delineation and Assessment Report (aka SWDAR) is twofold: to provide information that helps the Magnolia Estates PWS protect its drinking water source and to lay the groundwork for the development of source water protection planning.
Limitations This report was prepared to assess threats to the Magnolia Estates PWS (public water supply), and is based on published information and information obtained from persons familiar with the community. The terms “drinking water supply” or “drinking water source” refer specifically to the Magnolia Estates public water supply and not any other public or private water supply. Also, not all potential or existing sources of groundwater or surface water contamination in the area were identified. Only potential sources of contamination in areas estimated to contribute water to its drinking water source are considered.
The term “contaminant” is used in this report to refer to constituents for which maximum concentration levels (MCLs) have been specified under the national primary drinking water standards, and to certain constituents that do not have MCLs but are considered to be significant health threats.
Page 4 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR CHAPTER 1 BACKGROUND
The Community The Magnolia Estates subdivision is a subdivision located along the west side of Mullan Road, south of Frenchtown, and about 2 miles west of the Wye on I-90 in Missoula County. The subdivision is located northeast of the Clark Fork River and is within the center of the modern river valley. Figure 1, Figure 2, and Figure 3 display the subdivision’s relative location and are seen at the end of this document. According to the 2000 United States Census, Missoula County had 95,802 people and the City of Missoula had 57,053 people. Nearby Frenchtown is unincorporated and listed only as a Census Designated Place with a population of 883 people. The economic base of Missoula County is supported largely by private businesses, and is bolstered by the federal, state, and local government as major revenue contributors.
Geographic Setting The Magnolia Estates subdivision is situated in the Clark Fork River valley. The Clark Fork River runs generally northwest through the area toward Saint Regis, Plains, Thompson Falls, and ultimately to its confluence with the Columbia River on the Washington/Canada. The Clark Fork River runs through a northwest trending intermontane basin, which is one of several parallel valleys in this part of Montana. The valley around Magnolia Estates subdivision is bounded by the Bitterroot Range to the south and the Coeur D’Alene Mountains to the north.
The climate in this area is a modified Pacific maritime climate that is typical of lower elevation intermontane basins found in the Northern Rocky Mountains west of the continental divide. Generally, the area experiences warm summers and cool, humid winters. Historic climatic data for the nearby Missoula Airport is presented in Table 1 below. Average annual precipitation is approximately 13.6 inches and average annual snowfall is 45.9 inches.
Table 1. Climatic Data Missoula Airport WSO AP, Montana (245745) Period of Record Monthly Climate Summary Period of Record : 7/ 1/1948 to 12/31/2005 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Average Max. Temperature (F) 30.0 36.9 46.3 57.1 65.9 73.8 84.2 83.1 71.5 57.0 40.3 31.1 56.4 Average Min. Temperature (F) 15.0 19.7 25.5 31.9 39.0 45.6 50.0 49.0 40.7 31.5 23.9 17.1 32.4 Average Total Precipitation (in.) 1.16 0.76 0.90 1.08 1.81 1.92 0.96 1.03 1.06 0.86 0.92 1.13 13.58 Average Total Snowfall (in.) 12.6 7.2 6.1 1.9 0.6 0.0 0.0 0.0 0.0 0.8 5.7 10.9 45.9 Average Snow Depth (in.) 4 3 1 0 0 0 0 0 0 0 0 2 1 Source: Western Regional Climate Center, [email protected]
Description of the Source Water In the development of this SWDAR hydrogeologic information was found that addresses the immediate vicinity of Magnolia Estates subdivision. The following interpretations are drawn from the regional geologic map, area lithologic and well logs, and a general knowledge of geology/hydrogeology. Figure 4 (found at the end of this document) depicts the distribution of surficial geologic units around the Magnolia Estates subdivision. It should be noted that a recent Source Water Delineation and Assessment
Page 5 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Report (SWDAR) was completed for a proposed public water supply (a PWS) and submitted to DEQ for a planned horse arena that will be located directly south of the subdivision. The arena will be called the Flying H Event Center. The report was completed by Geomatrix Consultants Inc. out of Missoula. It was well written and drew information from the Magnolia Estates wells and other area wells to summarize the local geology and hydrogeology. Much of my geologic interpretation in this report is drawn from the Flying H Event Center SWDAR (a copy is found in Appendix D of this document). The information available suggests that the Magnolia Estates PWS wells draw water from a deeper aquifer beneath glacial lakebed sediments that are distributed along the flanks of the valley. The lakebed sediments are generally fine grained and can act as a confining unit, as they overlie more conductive water-bearing sediments. It appears that the water-bearing materials beneath the lakebed sediments behave as a confined aquifer. For the purposes of this SWDAR, the lower aquifer beneath the Magnolia Estates subdivision is considered to be under semi-confined conditions. This is the aquifer that the Magnolia Estates PWS draws water from a semi-confined aquifer that has a moderate sensitivity to contaminant sources at the surface.
Groundwater flow directions have been established on a broad scale for the valley, but not for precise locations in the Missoula Valley. It appears that groundwater basically flows from the mountains toward the river valley. Within the valley, shallow groundwater will flow toward, then sub-parallel to, surface water flow within the active stream. Based on valley-wide conditions, it is likely that groundwater flow in the aquifers beneath Magnolia Estates is probably to the northwest.
The Public Water Supply Magnolia Estates (# MT0004021) is classified by DEQ as a Community PWS. According to the most recent Sanitary Survey completed in 2007 and current DEQ files, the production wells (Well 1 East and Well 2 West) for the Magnolia Estates PWS daily supplies water to the 196 people (194 residents and 2 day workers in the subdivision) (Figure 3) through 57 active residential service connections. The Magnolia Estates PWS wells are located as seen on Figure 2 & Figure 3.
Well 1 East (WL002) was drilled in 1998 to a depth of 150 feet below ground surface (bgs) with the casing advanced to 148 feet bgs. The well casing was left with an open bottom as the intake. Static water level for Well 1 was listed on the well log as 21 feet bgs and pumping water level was 28 feet at a pumping rate of 290 gallons/minute. Well 2 West (WL003) was also drilled in 1998 to a depth of 159 feet below ground surface (bgs) with the casing advanced to 146 feet bgs. It should be noted that the Geomatrix SWDAR (2007) suggested that the well was 157 (which is very similar to the 159 feet seen on the well log). The well casing of Well 2 West was left with an open bottom as the intake. Static water level for Well 2 West was listed on the well log as 21 feet bgs and pumping water level was 24.3 feet at a pumping rate of ~296 gallons/minute. An attempt to seal outside the casing appears to have been made by continuous feed bentonite during the last 74 feet of casing installation. Continuous feed is a methodology that puddles bentonite slurry around a well casing as it is advanced downward during drilling. With this method, the bentonite is assumed to be entrained and carried downward along with the well casing. A well sealing process that is more trusted entails actively filling the gap between the outside of the well casing and the drilled borehole into which it is installed. This filling of the gap (aka the annulus of the well) is generally accomplished using a tremmie pipe to fill the gap from the bottom up, which assures that there really is grout surrounding the well casing and filling all voids present outside of the casing. The grouting material acts to reduce the migration of surface water or near surface water downward along the outside of the casing and reaching the aquifer. A poorly sealed well can have
Page 6 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR a significant bad impact on water quality in an aquifer and in the well pumping from the aquifer. Continuous feed is not generally considered a very adequate grout seal around the casing.
The wells are plumbed to a common header (CH001) located in the tank house located between the wells. Pressure provided by the submersible pumps is stored in the pressure tank found within the tank house. The pressure control assembly consists of 2,500 gallon pressure tank and pressure switch. A compressor is connected to the system and is utilized when the tank needs pressurization. The PWS does not appear to be treating the water prior to sending it to distribution. The water system is discussed in greater detail in the Sanitary Survey (2007). This Sanitary Survey and other relevant information concerning the PWS are included in Appendix B. Table 2 below is a summary of the facilities at Magnolia Estates PWS.
Table 2. PWS Facilities and Well Information Magnolia Estates PWS (#MT0004021) Contact Information Magnolia Estates Magnolia Estates Attn: Barbara Howell Attn: Jeff McCleary, Operator 7501 Gardenia Drive 10624 Oral Zumwalt Way Missoula, Montana 59808 Missoula, Montana 59803 406/ 728-2216 406/ 273-3197 PWS Classification Community
Well/Intake Source WL002 WL003
Well/Intake Name Well 1 East Well 2 West Active Active Common Header CH001, Common header for Well 1 and Well 2, with EP502 (sampling point) Active Pressure Control Assembly PC001, One 2,500 gallon pressure tank, located in the tank house Storage Facility No storage facilities are associated with this PWS
Distribution System DS001 Distribution System, with SP001 (sampling point) Active Treatment None
Water Quality Water quality data for the Magnolia Estates PWS is included in Appendix A. This data indicates that coliform bacteria have not been present in samples during routine sampling over the past several years. Further, no organic or inorganic contaminants (other than nitrate) have been detected in noteworthy levels during this time. The concentration of nitrate has ranged from 0.06 to 0.26 mg/L. These concentrations for nitrate are relatively low and probably represent background conditions in the area. The concentrations discussed above are not hazardous, but if the numbers increase steadily over the next several years, this trend might represent human impacts to groundwater. A concentration of 10 mg/L is the EPA mandated Maximum Contaminant Level (MCL) for nitrate in public water supplies.
Page 7 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR
CHAPTER 2 DELINEATION
Delineation Process The source water protection regions are identified in this chapter. They are the delineated land areas that contribute water to the Magnolia Estates PWS wells. Three (3) source water protection regions are usually identified. These three regions are the Control Zone, Inventory Region, and Recharge Region. The Control Zone, also known as the Exclusion Zone, is an area at least 100-foot radius around the PWS wellheads. Human activity in this area can have an immediate impact on water quality by introducing contaminants into the area directly above a well intake. As such, management of this Control Zone is critical to protect a PWS. For groundwater sources the Inventory Region usually represents the zone of contribution of the well, which can approximate a three-year groundwater time-of-travel or a 1-mile radius around a wellhead. The Inventory Region comprising a 1-mile radius circle around a well is often a conservative value that is used either for convenience or when insufficient geologic or hydrogeologic information is available about an area or when details are lacking on the construction of a production well. In certain circumstances where a PWS well taps into an aquifer that has been characterized as being confined, the Inventory Region can be limited to an approximate 1,000-foot radius around the wellhead, and the inventory of potential contaminant sources is only completed for those sources within 1,000-feet of the well. Activities or contaminant releases within the Inventory Region have the potential to reach a PWS well in a period approximating less than 3 years. The Recharge Region represents the entire portion of the aquifer or an area that contributes water to the local aquifer and over time supplies water to a well. This extended region of groundwater recharge is often, but not always, inclusive of the limits of a watershed. At times an entire watershed is too large to be realistically manageable by a PWS or community, so a subsection of that watershed is delineated as the Recharge Region. Long-term water quality at a PWS can be affected by larger contaminant releases or certain land use activities in the Recharge Region.
Hydrogeologic Conditions In the development of this SWDAR I found a relatively detailed hydrogeologic summary in the Geomatrix Consultants, Inc. SWDAR for the proposed Flying H Event Center public water supply (2007, see Appendix D). The Flying H site is directly south of the Magnolia Estates subdivision and the report provides hydrogeologic interpretations drawn from tests performed on the 2 Magnolia Estates PWS wells and other area wells. The following geology and hydrogeology are drawn heavily from the Flying H SWDAR (2007), but are also drawn from the geologic map, area lithologic and well logs, and a general knowledge of geology/hydrogeology. Table 3 below is a summary of some of the relevant geologic sources used to develop this SWDAR.
Table 3. Sources of Hydrogeologic Information (from the Geomatrix Consultants SWDAR for Flying H Event Center (2007)) Reference Source Summary Description
Grimestad (1977) Investigation of effluent from the nearby Smurfit-Stone pulp mill
Page 8 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Table 3. Sources of Hydrogeologic Information (from the Geomatrix Consultants SWDAR for Flying H Event Center (2007)) GWIC (2007) The state of Montana's online repository of well log information; also includes some water quality data
Lafave (2006) Map of potentiometric surfaces of Missoula area aquifers
McMurtrey etal. (1965) Geologic and hydrogeologic study of the Missoula Valley; methods included field mapping, geophysical surveys, and aquifer testing
Smith (1992) Hydrogeology of the northwestern part of the Missoula Valley
Smith (2006a) Map of thickness of Quaternary unconsolidated deposits in the Missoula area
Smith (2006b) Map of altitude of bedrock in the Missoula area
Geologic Setting The Missoula Valley is a structural basin bounded by normal and thrust faults that separate the lower elevations from the mountains (McMurtrey et al. 1965). Lewis (1998) provided a surficial geologic map of the Missoula Valley. According to Lewis, Quaternary-aged alluvium from the modern Clark Fork River channel and floodplain underlies the entire property (Figure 4 of the Magnolia Estates SWDAR). This recent alluvium underlies the floodplain of the Clark Fork River and extends to the north and south of the Flying H property. Older Quaternary alluvial deposits are found to the north and east of the property.
Quaternary unconsolidated deposits are between 100 and 150 feet thick in the area of the Flying H property and Magnolia Estates (Smith 2006a). McMurtrey et al. (1965) reported similar geology. Note that the Magnolia Estates Well 2 West hit bedrock at 147 feet bgs. According to the Montana Department of Health and Environmental Services (in Grimestad 1977), the stratigraphy of the Quaternary sediments in the area comprises two productive aquifers separated by a leaky confining layer. Transmissivity of the upper sand and gravel aquifer (15 to 35 feet thick) averaged approximately 9000 ft/day in an area approximately 1 mile north (Grimestad 1977). Based on an upper aquifer thickness of 25 feet, hydraulic conductivity is estimated to be 370 feet per day. A leaky confining layer of mixed clay, silt, sand, and gravel exists below the shallow aquifer and is 60-125 feet thick. The lowermost Quaternary lithologic unit is a deeper sand and gravel aquifer penetrated by many water supply wells in the vicinity of Magnolia Estates and the Flying H facility. The hydraulic conductivity of the lower aquifer is equal to or higher than that of the shallow aquifer (Grimestad 1977; McMurtrey etal. 1965).
The formation found immediately beneath the Quaternary deposits is fine-grained bedrock, encountered in the Magnolia Estates wells from 147 to 159 feet. Mapped units in the area do not closely match this description. Although the driller's log refers to the unit as an argillite, the rock may in fact be the Cambrian Hasmark Formation, a gray dolomite (Lewis 1998). Note that dolomite is a calcium and magnesium carbonate rock similar to limestone. Several lithologic logs from wells drilled northwest of the property indicate that a gray limestone unit was encountered at approximately 150 to 160 feet below ground surface (bgs). Below this bedrock, the Proterozoic Belt Supergroup forms the metamorphic basement.
Page 9 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR
In March 1998, Blackfoot Well Drilling of Bonner, Montana used a rotary drilling rig to drill and install two eight-inch diameter steel-cased supply wells in the southeast quarter of section 25 (Figure 2 and Figure 3 of the Magnolia Estates SWDAR). The Flying H SWDAR identified the wells as ME-PWS-I (for Well 1 East) and ME-PWS-2 (for Well 2 West). The purpose of well installation was to supply water to the Magnolia Estates Subdivision, which shares a property boundary with the Flying H Event Center parcel. The wells draw water from open bottoms and were not screened or perforated. ME-PWS- I (this is Magnolia Estates Well 1 East) was drilled to a total depth of 150 feet bgs, and the casing was advanced to 148 feet. Sediments encountered during drilling consisted of sand and gravel with minor amounts of silt, clay, and cobbles. The borehole for well ME-PWS-2 (this is Well 2 West) was drilled to 159 feet bgs. Lithologies encountered were similar to the first well, except that bedrock was encountered at 147 feet bgs. The casing was advanced to 146 feet bgs. During the drilling of each well, the water- bearing units produced approximately 350 gallons per minute (gpm) via airlifting. Lithologic descriptions indicate that the aquifer is either unconfined or is overlain by a leaky semi-confining unit.
Descriptions of sediments on well logs (see the appendices) are consistent with the geologic description given by Lewis (1998): modern alluvial sand and gravel. Field observations also correlate with the work of Smith (2006a), who mapped a thickness of 100 to 150 feet of Quaternary sediments in the general site area. According to the lithologic log for ME-PWS-2 (Well 2 West), Quaternary-aged materials extended to a depth of 147 feet. Smith (2006b) reported a bedrock elevation of approximately 2,900 feet in the southeast quarter of section 25. The ground surface elevation in this area is approximately 3,060 feet above msl (mean sea level), or 160 feet above the bedrock surface. This depth correlates roughly with the bedrock depth recorded on the lithologic log for well ME-PWS-2.
McMurtrey et al. (1965) show groundwater in the vicinity of the site flowing to the northwest, toward the Clark Fork River. Lafave's (2006) potentiometric map also shows groundwater flow to the northwest. A potentiometric map of the deeper aquifer by Smith (1992) shows flow to the west. Lafave showed that artesian conditions may be present on or near the Flying H property. Water levels in deep wells may be at or within ten feet of ground surface.
Wells in section 25 (43 well total) are completed to total depths ranging from 18 to 240 feet bgs (MBMG 2007). According to GWIC lithologic logs, these wells produce from 12 to 2,000 gpm. Several high-producing wells (1,800-2,000 gpm) serve the industrial needs of Smurfit-Stone Container Corporation's (SSCC) pulp mill located approximately 1.5 miles to the northwest of Flying H and Magnolia Estates. Most of the wells in section 25 are less than 150 feet deep and are finished in alluvial sand and gravel. Static water levels are shallow (5 to 21 feet bgs). Static water levels in the Magnolia Estates wells are approximately 21 feet bgs.
The Magnolia Estates public supply wells Well 1 East and Well 2 West produce water from the leaky confined alluvial aquifer, which is up to 120 feet thick, according to their lithologic logs. Bedrock underneath the sand and gravel units represents the vertical aquifer boundary, and the alluvial aquifer is bounded aerially by the hills and mountains at the valley margins.
Aquifer Properties During March 1998, two aquifer tests were performed on the Magnolia Estates PWS wells. Well ME- PWS-I (Well 1 East) was pumped at an average rate of 295 gpm for approximately 10 hours. The flow
Page 10 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR rate was apparently lowered by the test operator (from 320 gpm to 290 gpm) after approximately 100 minutes of pumping. The reason for the flow rate adjustment is unknown. Well ME-PWS-2 (Well 2 West) was pumped at a constant rate of 290 gpm for approximately 8 hours. Water levels were measured in the pumping well during the pumping and recovery periods of each test. Observation well drawdown measurements were not collected during either test. Plots showing drawdown and flow rate in the pumping wells are presented with the Flying H report found in Appendix D. The discharge rate sustained during each test does not appear to have stressed the aquifer sufficiently to produce typical time-drawdown curves. Additionally, the nearby Clark Fork River (approximately 3,500 feet west of the Flying H property) may have acted as a constant-head recharge boundary. During both tests, the water levels in the pumping wells stabilized after about one minute of pumping.
Geomatrix attempted to analyze water level drawdown and recovery data using the Theis (1935) equation, but because of the conditions described above, standard curve-matching techniques do not provide an appropriate method for estimating aquifer transmissivity. Specific capacity provides an independent estimate of aquifer transmissivity (Driscoll 1986). The specific capacity of a pumping well is the discharge per foot of drawdown. The drawdown values used were those determined during a period of stable drawdown late in each test. Using a discharge of 290 gpm and a drawdown of 6.8 feet, the transmissivity of the unconfined aquifer in the vicinity of well ME-PWS-I is estimated to be 64,000 gallons per day per foot, or 8550 ft2/day (Table 4). Using a discharge of 290 gpm and a drawdown of 3.3 feet, the transmissivity of the unconfined aquifer in the vicinity of well ME-PWS-2 is estimated to be 131,000 gpd/ft, or 17,600 ft2/day. McMurtrey et al. (1965) estimated transmissivity values using specific capacities of two production wells at the nearby pulp mill (Table 4). The aquifer thickness used to estimate hydraulic conductivity for these two wells was taken from Grimestad (1977). Data from these wells suggest that the hydraulic conductivity of the shallow aquifer in this area is higher than that beneath the Magnolia Estates subdivision.
Table 4. Summary of Aquifer Test Results (summarized in the Flying H Event Center SWDAR) Well Transmissivity Aquifer Thickness Hydraulic Conductivity (feet2/day) (feet) (feet/day)
ME-PWS-I 8,550 120 71
ME-PWS-2 17,600 120 147
Pulp Mill #1 77,000 35 2,200
Pulp Mill #2 1 25,000 35 3,571
Average Aquifer Hydraulic Conductivity 1,500
Some of the basic assumptions made by Geomatrix during their analysis are as follows. Precipitation, leakage from irrigation canals, excess irrigation water, snowmelt runoff, and losing streams recharge groundwater in the Missoula Valley. Groundwater in the area of the Flying H property originates from upgradient portions of the Missoula Aquifer, infiltration of precipitation and snowmelt runoff, recharge from the O'Keefe and La Valle Creek drainages, and leakage from irrigation ditches. Groundwater beneath the property ultimately discharges into the Clark Fork River west of the site (Smith 1992). The
Page 11 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR aquifer in which the PWS well will be installed is an unconfined or leaky confined system based on lithologic observations made during test well drilling. For the purposes of the source-water delineation analysis, Geomatrix assumed that the aquifer is isotropic and homogenous and extends underneath the entire property. Vertical boundaries include the bottom of the leaky confining unit and bedrock below the basal aquifer (Figure 4). The ground water flow direction is to the west-northwest. Depth to groundwater measured in the Magnolia Estates PWS wells was approximately 21 feet bgs in March 1998.
PWS Source Information Relevant information regarding Magnolia Estates PWS wells is summarized in Table 5 below.
Table 5. PWS Source/Well Information Magnolia Estates Public Water Supply (# MT0004021) Source Name Well 1 East Well 2 West
Source Code WL002 WL003 Active Active MBMG GWIC # Unknown Unknown
DNRC Water Right # Unknown Unknown
Date completed 06 March 1998 08 March 1998
Total Depth (feet bgs) 150 159 per the well log
Depth of Bedrock Note encountered 147 hit bedrock = argillite, gray
Depth of Well Casing (feet bgs) 148 146
Depth of Grout Seal (ft bgs) Continuous feed Continuous feed Bentonite to ~66 ft. Bentonite to ~74 ft. Perforated Interval (ft bgs) Not screened, open bottom casing Not screened, open bottom casing
Static Water Level (ft bgs) 21 21
Pumping Water Level (ft bgs) 28 24.3
Draw Down (ft) 7 3.3
Test Pumping Rate (gpm) 290 296 Note: The information on these wells listed above comes from the original well logs included in this report.
The following summarizes the assertions and assumed values concerning groundwater characteristics made by Geomatrix in the Flying H SWDAR. Based on the results of aquifer testing, K was estimated to be 1,500 ft/day. A gradient estimate of 0.004 was derived from Lafave (2006). Porosity is estimated to be 0.25 (U.S. EPA 1994) and, based on lithology encountered during the Magnolia Estates drilling, the average aquifer thickness is about 120 feet. The values presented above are estimates, and are the best approximations based on field data and information from the literature. Using these values, along with the estimated total average daily water demand of 35 gpm, it would take groundwater three years to travel from a point 25,000 feet (4.7 miles) upgradient to either Magnolia Estates well. The Inventory Region is based on the 3-year groundwater time-of-travel (TOT) distance. It should be noted that a 1- year groundwater TOT distance is also determined for this report. The significance of the 1-year and 3-
Page 12 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR year TOT distances will be discussed in the next section. Input variables and parameter estimates for the time-of travel calculation are summarized in Table 6.
Table 6. Summary of Inputs and Results for Time-of-Travel Calculation
Input Variable Value Used in Calculation Units
Hydraulic Conductivity 1,500 feet/day
Discharge/pumping rate 35 gpm
Aquifer Thickness 120 feet
Hydraulic Gradient 0.004 feet/foot
Effective Porosity 0.25 NA
Resulting Groundwater Time-of-Travel (TOT) Distances: 1-year TOT Distance ~1.6 miles 3-year TOT Distance -4.7 miles
Delineation Results Delineation for the source water protection regions was completed assuming that the Magnolia Estates PWS wells are withdrawing water form a laterally extensive but semi-confined deep aquifer. The information on well construction and other well and lithologic logs in the area support this assumption. The Control Zone is delineated to provide a minimum 100-foot radius buffer around the wellheads. The Inventory Region was delineated as 3-year groundwater time-of-travel (TOT) distance in an upgradient direction (east) from the PWS wellheads. The region extends to the area of the Missoula Airport and El Mar Estates. The north border for the Inventory Region is best defined by Highway I-90 and the south border is along the active flood plain for the Clark Fork River. The Inventory Region is depicted on Figure 5. On this figure it should be noted that I depicted a 1-year groundwater TOT distance as well as a 3-year TOT distance. The 1-year TOT distance encloses and area where potential contaminant sources are characterized as having an increased hazard to the PWS during the susceptibility assessment. The Recharge Region was delineated to enclose an area containing potential contaminant sources that may be likely to impact the water quality of the Magnolia Estates PWS over longer times. A constraint in defining a Recharge Region was to limit the region to an area that the PWS will be able to have some positive influence on the activities and practices that occur. The watershed upgradient from this PWS comprises the Blackfoot, Clark Fork, and Bitterroot River drainages, which would be too large an area for this PWS to have any significant influence on policy. As such, I’ve limited the Recharge Region to the Missoula Valley upgradient from the PWS wells (without including the City of Missoula). Figure 6 is a depiction of the Recharge Region I delineated for this SWDAR. Note that it reaches up Butler Creek, up Grant Creek, and extends up the Missoula Valley to the west end of Missoula.
Limiting Factors Groundwater behavior in general terms is understood in the Clark Fork River valley, but it is not easily predictable beneath specific locations. This is especially true around a certain well that is drawing water
Page 13 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR from a specific depth at a specific time of year. Groundwater flow direction fluctuates seasonally and from year to year. Here, several conservative assumptions were made in the delineation of the source water protection areas and the development of this report. Also, reliance on some basic hydrogeologic principals to define the aquifer boundaries and groundwater movement was employed. The SWDAR can and should be revised if more data becomes available that alters the assumed groundwater flow direction(s) or confinement.
Page 14 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR CHAPTER 3 INVENTORY
Inventory Method An inventory of potential sources of contamination was conducted for the Magnolia Estates PWS within the Control Zone, Inventory Region, and Recharge Region. Potential sources of all primary drinking water contaminants and Cryptosporidium were also identified and noted, however, only significant potential contaminant sources were selected for detailed inventory and the susceptibility evaluation that occurs in Chapter 4 of this SWDAR. It should be noted that the inventory emphasizes potential contaminant sources. Inclusion of a facility or business in the inventory does not indicate that it is an actual polluter. The exception to this would be known hazardous waste sites where past releases have occurred, areas with known onsite contamination, locations with leaking underground storage tanks (LUSTs), or wastewater lagoons or dischargers.
The inventory for the Magnolia Estates PWS focuses on all activities in the Control Zone the well, certain types of municipal and private facilities in the Inventory Region, and general land uses and large facilities in the Recharge Region. The following databases have been searched in an effort to identify generators, storage facilities, and land uses that could be potential generators of contamination in the Inventory Region.
Step 1: Urban and agricultural land uses were identified from the U.S. Geological Survey’s Geographic Information Retrieval and Analysis System (http://nris.state.mt.us/gis/datalist.html). Sewered and unsewered residential land uses were identified from boundaries of sewer coverage obtained from municipal wastewater utilities. Septic density (the density of private onsite septic systems) was determined based on the 2000 US Census and obtained from the Montana State Library’s Natural Resource Information System (NRIS) Thematic Mapper (http://nris.state.mt.us/mapper/ ) and (http://nris.state.mt.us/wis/swap/swapquery.asp). In addition, county tax records were examined to determine the predominant agricultural land uses in the area of the water system.
Step 2: As appropriate, EPA’s Envirofacts System (http://www.epa.gov/enviro/) was queried to identify EPA regulated facilities located in the Inventory Region. This system accesses facilities listed in the following databases: Resource Conservation and Recovery Information System (RCRIS), Biennial Reporting System (BRS), Toxic Release Inventory (TRI), and Comprehensive Environmental Response Compensation and Liability Information System (CERCLIS). The available reports were browsed for facility information including the Handler/Facility Classification to be used in assessing whether a facility should be classified as a significant potential contaminant source.
Step 3: The Permit Compliance System (PCS) was queried using Envirofacts (http://www.epa.gov/enviro/) to identify Concentrated Animal Feeding Operations with MPDES permits. The PWS system operator and/or system managers are familiar with the area included in the Inventory Region and should identify animal feeding operations that are not required to obtain a permit.
Page 15 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Step 4: Databases were queried to identify the following in the Inventory Region: Underground Storage Tanks (UST) (http://webdev.deq.state.mt.us/UST/), hazardous waste contaminated sites (DEQ hazardous waste site cleanup bureau), landfills (http://nris.state.mt.us/gis/datalist.html), abandoned mines (http://nris.state.mt.us/gis/datalist.html) and active mines including gravel pits. Any information on past releases and present compliance status was noted.
Step 5: Major road and rail transportation routes were identified throughout the Inventory Region (http://nris.state.mt.us/gis/datalist.html).
Step 6: 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. Underground storage tanks. 4. Known groundwater contamination (including open or closed hazardous waste sites, state or federal superfund sites, and UST leak sites). 5. Underground injection wells. 6. Major roads or rail transportation routes. 7. Cultivated cropland greater than 20 % of the Inventory Region. 8. Animal feeding operations. 9. Wastewater treatment facilities, sludge handling sites, or land application areas. 10. Septic systems (based on size or concentration/density). 11. Sewer mains. 12. Storm sewer outflows. 13. Abandoned or active mines.
Inventory Results
Control Zone In the most recent Sanitary Survey (2006), no significant potential contaminant sources (PCSs) were identified in the vicinity of the wells. However, the area south of the wells will be developed as the Flying H Event Center (a large stable and horse arena facility). It does not appear that any stables or animal pens will be found within 100 feet of the wellheads. Since this facility is in the works at the time of this writing, care should be taken to keep concentrations of animals out of the Control Zones for the wells.
Inventory Region The Inventory Region for Magnolia Estates PWS is shown in Figure 5. Potential contaminant sources (PCSs) are described below and summarized in Table 7.
Interstate Highway 90 passes along a tangent to the northeast edge of the Inventory Region. Although the highway is outside of the region, it is nearby and uphill from the wells. Accidents with chemical spills along this highway could generate considerable contamination. Highway 93 runs through the region, but is outside of the 1-year TOT distance to the well. If a large amount of VOCs, SOCs, metals, or a host of other hazardous materials are released, water quality could be impacted. The highways are considered to
Page 16 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR be a significant potential contaminant sources for this PWS. Hazard determination is discussed in the next chapter. It should be noted that multiple active railroad lines pass through the Inventory Region and close to the Magnolia Estates wells. Although infrequent, spills along these lines are inevitable and can be catastrophic.
Large capacity septic systems are associated with businesses that serve more than 20 persons per day. These are not listed on any database at this time, but can often be identified by the presence of a regulated public water supply. It a business provides water to the public and it’s outside of sewered areas, it probably operates a large capacity septic system. Septic systems in general are determined based on the 2000 US Census data and are broken out by census blocks. These blocks are depicted on Figure 5 and Figure 6 as areas of High and Medium Septic Density.
Less than 50% of the Inventory Region is devoted to agricultural crop production. It appears that the land is used for grazing, hay, irrigated cropland, and/or fallow land. In many situations, these crops are fertilized and may receive applications of pesticides/herbicides. In addition, farm equipment used to work the fields need fuel (gasoline or diesel). Any handling, transferring, application or spilling of these chemicals can impact the shallow aquifer and potentially the deeper aquifer. Any such spills or releases should be considered to be significant potential contaminant sources.
Along with the above PCSs described above, there are underground fuel storage tank sites (UST sites), leaking underground fuel storage tank sites (LUST sites), wastewater discharges, a golf course, and a proposed large equestrian center. These are described below in Table 7 and in the next chapter.
Recharge Region The Recharge Region entails the watershed (northeast) of the wells, inclusive of the Magnolia Estates subdivision and extends to the western edge of the City of Missoula. The potential contaminant sources for the Recharge Region are essentially the same type as seen within the Inventory Region with the inclusion of a couple of more subdivisions and several other businesses scattered along Mullan Road and along Highways I-90 and 93. The Recharge Region is depicted on Figure 6.
Table 7. Potential Contaminant Sources Magnolia Estates PWS—Inventory Region Source Contaminants Description
Highway I-90 Fuels (VOCs, hydrocarbons), Spills that result from vehicle accidents. If sufficient volume of (spills that may occur during SOCs, metals, pathogens material is spilled, shallow groundwater and possibly deep the low frequency by high groundwater could be affected. These spills are a very low probability truck accidents) frequency, but very high probability events. Railroad Lines Fuels (VOCs, hydrocarbons), Spills that result from train accidents and chemicals applied for (spills that may occur during SOCs, metals, pathogens weed management along the rail lines. If sufficient volume of the low frequency by high material is spilled, shallow groundwater and possibly deep probability truck accidents) groundwater could be affected. These spills are a very low frequency, but very high probability events. Large Capacity Septic Septic effluent containing These septic systems can and do generate large volumes of Systems nitrogen, pathogens, or other effluent to the subsurface. These systems may be failing and can (noted by the presence of compounds generate poorly treated effluent. Chemicals can be improperly Public Water Supplies). disposed to these systems. Treated as point sources.
Page 17 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Table 7. Potential Contaminant Sources Magnolia Estates PWS—Inventory Region Source Contaminants Description
Septic Systems Septic effluent containing These septic systems taken together can and do generate large (areas of increased density nitrogen, pathogens, or other volumes of effluent to the subsurface. These systems may be of private septic systems). compounds failing and can generate poorly treated effluent. Chemicals can be Treated as a non-point improperly disposed to these systems. Note that these areas of source. increased septic density are actually based upon population density census blocks (from the 2000 census) located outside areas served by sewers. Agricultural Land Use Fuels (VOCs, hydrocarbons), Routine handling and application of farm chemicals (fertilizers (chemical handling, pesticides & herbicides and/or pesticides and herbicides). Spills of these chemicals or fuel application, spills, or (SOCs), fertilizers (mostly leaks from equipment. Concentrations of animals can concentrate concentrations of animals) nitrogen), and animal wastes animal wastes.
Wastewater Discharges Storm water, process Generally containing treated or partially treated waste streams. wastewater, and septic These discharges are permitted, but don’t really conform to any effluent which can contain all specific process. Some are septic discharges, some are storm sorts of chemicals or water, and some appear to be process wastewater. pathogens. Golf Course Fertilizers, pesticides (SOCs) Chemicals used for landscape and greens maintenance. Applications of ag chemicals are at concentrations typically well above those for edible crops and are followed by heavy watering.
Flying H Event Center Animal wastes that produce Basically this will be a business where there will be periodic nitrates and pathogens concentrations of animals (horses and possibly cattle). If animals are concentrated, animal wastes are concentrated. These wastes can quickly impact the shallow groundwater.
Underground Fuel Storage Petroleum hydrocarbons Chronic or catastrophic leaks and spills of stored fuels that impact Tanks (USTs) (VOCs) groundwater. & Leaking Underground Fuel Storage Tanks (LUSTs)
Inventory Update To make this SWDAR a useful document in the years to come, the owners, managers, or the water system operator for the Magnolia Estates public water supply should update the inventory for their records every year. Changes in land uses or the presence of new potential contaminant sources should be noted and additions made as needed. This updated inventory should be submitted to DEQ at least every 5 years to ensure that this report/plan stays current in the public record.
Inventory Limitations The extent of the potential contaminant source inventory is limited in several respects. The inventory is based on data that is readily available through state documents, published maps and reports, GIS data, and discussions with people that are familiar with the area. Also, documentation may not be readily available on some potential sources. As a result, all potential contaminant sources may not have been identified or recognized as being significant potential contaminant sources. The author of this SWDAR is depending on local PWS owners and/or operators for site-specific knowledge. Their initial review of this document is sought and if their comments are provided, they will be incorporated.
Page 18 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR CHAPTER 4 SUSCEPTIBILITY ASSESSMENT
General Discussion Susceptibility is the potential for a public water supply to draw water contaminated by inventoried sources at concentrations that would pose concern. Susceptibility is assessed in order to prioritize potential pollutant sources for management actions by local entities, in this case Magnolia Estates PWS owner(s), manager(s), and the operator. The goal of source water management is to protect the source water by 1) controlling activities in the Control Zone, 2) managing significant potential contaminant sources in the Inventory Region, and 3) ensuring that major land use activities or other significant activities in the Recharge Region pose minimal threat to the source water. Management priorities in the Inventory Region are determined by ranking the significant potential contaminant sources identified in the previous chapter according to susceptibility. Alternative management approaches that could be pursued by the PWS owners and the operator to reduce susceptibility are recommended in this chapter.
Hazard Determination The Susceptibility of the Magnolia Estates PWS production wells to various types of contamination is assessed in the following paragraphs. The proximity of a potential contaminant source to a spring or well intake, potential contaminant migration pathways, or the density of potential non-point contaminant sources determines the threat of contamination, referred to here as hazard (Table 8). Hazard and the existence of barriers to contamination determine susceptibility, which is described in Table 9. Table 8 below describes the criteria to determine hazard within the Inventory Region as it was delineated in this SWDAR. Note that this table is specific to PWSs that draw their water from unconfined and semi- confined aquifers. It should be noted that potential contaminant sources (point sources) that are located within the 1-year groundwater TOT distance are ranked with a high hazard, those between the 1- and 3- year TOT distances are given a moderate hazard and those outside but in the proximity of the 3-year groundwater TOT distance are assigned a low hazard. The determination of hazard is somewhat different for other types of water sources including wells drawing water from confined aquifers. For the situation involving the Magnolia Estates PWS, its production wells draw water from a deep semi-confined aquifer.
Table 8. Determination of Hazard for potential contaminant sources. This is applicable to PWSs drawing water from Unconfined and Semi-Confined Aquifers Potential Contaminant High Hazard Moderate Hazard Low Hazard Source Point Sources Within 1 year TOT Between 1 to 3 years TOT Over 3 years TOT
Septic Systems More than 300 per sq. mi. 50 – 300 per sq. mi. Less than 50 per sq. mi. Municipal Sanitary Sewer More than 50 percent of Less than 20 percent of 20 to 50 percent of region (percent land use) region region Cropped Agricultural More than 50 percent of Less than 20 percent of Land 20 to 50 percent of region region region (percent land use)
Susceptibility is determined by considering the hazard rating for each potential contaminant source and the existence of barriers that decrease the likelihood that contaminated water will flow to the Magnolia Estates well intake. Barriers are things that will stand between a water source intake and any potential contaminant sources. These barriers typically fall into 1 of 3 varieties: management barriers, natural
Page 19 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR barriers, or engineered barriers. First, hazard is rated by the proximity of a potential contaminant source to the well(s) locations (within the 1-year TOT distance or between the 1- and 3-year TOT distances). Susceptibility ratings are then determined individually for each significant potential contaminant source and/or contaminant based on the number of barriers as prescribed by Table 9. These susceptibility ratings are the evaluation of the estimated vulnerability of wells to the potential contaminant sources. These susceptibility ratings are presented on Table 10.
Table 9. Susceptibility, Based on Hazard and Barriers
Hazard Presence Of Barriers High Moderate Low Very High Moderate No Barriers High Susceptibility Susceptibility Susceptibility High Moderate Low One Barrier Susceptibility Susceptibility Susceptibility Moderate Low Very Low Multiple Barriers Susceptibility Susceptibility Susceptibility
Discussion of Susceptibility A summary of the susceptibility assessment for the Magnolia Estates PWS wells is located in Table 10. Below is a brief discussion of the susceptibility assessment for the significant potential contaminant sources. Other sources of contamination may also exist and may pose threats to the public water supply wells. It is prudent to make further attempts to identify these sources, especially if they are up-gradient from the PWS, and to understand the treats they pose.
Summary of Susceptibility Assessment The Magnolia Estates Public Water Supply uses 2 wells that are installed into what appears to be a deeper semi-confined aquifer. Groundwater beneath the area is believed to flow in an approximate northwest direction. The Inventory Region was established as 3-year groundwater time-of-travel (TOT) distance upgradient from the wells as seen on Figure 5.
The public water supply wells for the Magnolia Estates PWS have a moderate susceptibility to contamination from animal wastes from the nearby Flying H Event Center and spills that may happen along the railroad tracks. Both of these potential contaminant sources (PCSs) were assigned a high hazard due to their close proximity to the PWS wells. It should be noted that the Flying H Event Center has applied to DEQ to operate a public water supply, but at the time of this writing (April 2008) the facility has not yet been built. It is recognized that there are several different types of barriers that stand between the PCSs and the PWS wells’ intakes, which results in a moderate susceptibility of the wells’ intakes.
The Magnolia Estates PWS wells have a low to very low susceptibility to the remaining PCSs within the Inventory Region. This is mostly due to the low density of these PCSs or to the distance between these PCSs and the PWS wells’ intakes combined with the number of barriers thought to be present.
The Recharge Region is depicted on Figure 6. The inventory of PCSs in the Recharge Region is much like that seen for the Inventory Region, except it extends further toward the City of Missoula. The identified
Page 20 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR PCSs in the greater Recharge Region can affect water quality at the PWS over time, but aren’t included in the susceptibility assessment conducted in this chapter.
Page 21 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR
Table 10. Susceptibility Assessment Magnolia Estates PWS – Inventory Region (only) Source Contaminants Description Hazard Rating Barriers Susceptibility Management Suggestions (natural, management, or engineered) Flying H Event Animal wastes Basically this High Hazard • Saturated thickness of sediment (thickness of Moderate • Friendly promotion of the use of BMPs (best Center that produce will be a standing water) above the intake is >50 feet. Susceptibility management practices) for animal waste handling. nitrates and business where (located within pathogens there will be 1-year GW • Aquifer is semi-confined with multiple clay or • Try to get a handle and understand surface water periodic TOT distance silt layers above the deeper semi-confined aquifer. drainage to reduce any potential that surface water and roughly concentrations of • Evidence suggests that the groundwater (impacted by animal waste) would flow toward the upgradient animals (horses throughput (amount of water moving past this site) PWS wells. If surface water is headed for your from the PWS and possibly and dilution is great in this part of the valley. wellheads, develop a drainage channel to catch and wells) divert surface water away from the wells. cattle). If • It is assumed that some ongoing boarding of animals are horses will occur. But the concentrations of animals • Sampling result for all PWSs has been made available concentrated, are mostly going to be episodic rather than full- online. It would be useful to call up the sampling animal wastes time. results for the Flying H Event Center PWS to see if are concentrated. chronic bacteriological or nitrate results are occurring. These wastes can • Best management practices will be utilized to At the time of writing this SWDAR, the PWS number quickly impact handle animal wastes. This will be a high end arena has not yet been assigned for the Flying H Event the shallow and will desire to maintain a good public image and Center PWS. a clean operation. groundwater. Railroad Lines Fuels (VOCs, Spills that result High Hazard • Missoula County, MDT, and the railroad lines Moderate • Maintain an emergency call-down list of responders in (spills that may hydrocarbons), from train (within the 1- have spill response and cleanup personnel and Susceptibility the event of a major spill (especially on Mullan Road). occur during the SOCs, metals, accidents and resources available in this area. low frequency pathogens chemicals year GW TOT • Monitor and support the development of a local by high applied for weed distance) • Saturated thickness of sediment (thickness of volunteer spill response capability. I don’t know if probability management standing water) above the intake is >50 feet. local emergency spill responders (fire department or derailment along the rail • Aquifer is semi-confined with multiple clay or others) are present in the area. If they aren’t there yet, accidents) lines. If silt layers above the deeper semi-confined aquifer. it’s worth promoting to get them established. sufficient • Evidence suggests that the groundwater • Evaluate surface water drainage along the railroad volume of throughput (amount of water moving past this site) line. It is desirous that surface water move away from material is and dilution is great in this part of the valley. the area of the PWS wells rather than toward them spilled, shallow (thus conducting spills away from the Control Zones). groundwater and • It would probably be a good idea to develop local possibly deep contacts that had resources this PWS could use during groundwater a spill event to protect themselves. Some of these could be resources could be a backhoe, a source of soil, etc. affected. These spills are a very low frequency, but very high probability events.
Page 22 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Table 10. Susceptibility Assessment Magnolia Estates PWS – Inventory Region (only) Source Contaminants Description Hazard Rating Barriers Susceptibility Management Suggestions (natural, management, or engineered) Highway I-90 Fuels (VOCs, Spills that result Moderate • Missoula County and MDT have spill response Low • Maintain an emergency call-down list of responders in and US 93 hydrocarbons), from vehicle Hazard and cleanup personnel and resources available. Susceptibility the event of a major spill (especially on Mullan Road). (spills that may SOCs, metals, accidents. If occur during the pathogens sufficient (outside the 1- • Saturated thickness of sediment (thickness of • Monitor and support the development of a local low frequency volume of year GW standing water) above the intake is >50 feet. volunteer spill response capability. I don’t know if TOT distance) by high material is • Aquifer is semi-confined with multiple clay or local emergency spill responders (fire department or probability truck spilled, shallow silt layers above the deeper semi-confined aquifer. others) are present in the area of the Wye or the accidents) groundwater and airport. If they aren’t there yet, it’s worth promoting • Evidence suggests that the groundwater to get them established. possibly deep throughput (amount of water moving past this site) groundwater and dilution is great in this part of the valley. could be affected. These • Both highways are somewhat lateral along the spills are a very groundwater gradient (they aren’t directly low frequency, upgradient). but very high • Several surface water features drain the land probability between the highways and the PWS wells. events. Large Capacity Septic effluent These septic Moderate • Saturated thickness of sediment (thickness of Low • Most of the large capacity septic systems are located Septic Systems containing systems can and Hazard standing water) above the intake is >50 feet. Susceptibility along Hwy I-90 and US 93 around the Wye and (noted by the nitrogen, do generate large (most are • Aquifer is semi-confined with multiple clay or toward the airport. As the city of Missoula presence of pathogens, or volumes of progressively extends sewer service, it would be in the Public Water other compounds effluent to the outside the 1- silt layers above the deeper semi-confined aquifer. year GW TOT best interest of this PWS to promote the extension of Supplies). subsurface. • Evidence suggests that the groundwater distance) sewer service northwest along the highways to the Treated as point These systems throughput (amount of water moving past this site) Wye. sources. may be failing and dilution is great in this part of the valley. and can generate • Several surface water features drain the land poorly treated between these large septic systems and the PWS effluent. wells. Chemicals can be improperly • Most of the Magnolia Estates sewer lines and the disposed to these septic drainfield is located downgradient from their systems. wells.
Page 23 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Table 10. Susceptibility Assessment Magnolia Estates PWS – Inventory Region (only) Source Contaminants Description Hazard Rating Barriers Susceptibility Management Suggestions (natural, management, or engineered) Septic Systems Septic effluent These septic Moderate • Saturated thickness of sediment (thickness of Low • Most of these septic systems are concentrated within (areas of containing systems taken Hazard standing water) above the intake is >50 feet. Susceptibility the 1-year TOT distance of the PWS wells and a there increased nitrogen, together can and (medium • Aquifer is semi-confined with multiple clay or is a high density of systems area concentrated within density of pathogens, or do generate large Magnolia Estates itself. It would be beneficial to have private septic other compounds volumes of density of silt layers above the deeper semi-confined aquifer. systems for a local educational program to promote septic systems). effluent to the • Evidence suggests that the groundwater about 50% of maintenance, pumping, and proper handling and Treated as a subsurface. throughput (amount of water moving past this site) the 1-year GW disposal of chemicals (and not in the septic system). non-point These systems and dilution is great in this part of the valley. Missoula County and DEQ are able to conduct these source. may be failing TOT distance and high training events. Within the subdivision, education and can generate materials can be provided along with PWS billing. poorly treated density within Magnolia These billing mailers have already been developed effluent. and are generally free to the PWS. Chemicals can Estates itself) be improperly • Most of the concentrations septic systems extend disposed to these toward the Wye, along Hwy I-90 and US 93, and systems. Note along Mullan Road. As the city of Missoula that these areas progressively extends sewer service, it would be in the are based on best interest of this PWS to promote the extension of population sewer service northwest along the highways to the density (2000 Wye and possibly along Mullan Road. US Census • Promote the development of County policy for your blocks). Inventory Region, where new or replacement septic systems need to provide Level II treatment. • Promote the development of Magnolia Estates policy where new or replacement septic systems need to provide Level II treatment.
Page 24 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Table 10. Susceptibility Assessment Magnolia Estates PWS – Inventory Region (only) Source Contaminants Description Hazard Rating Barriers Susceptibility Management Suggestions (natural, management, or engineered) Underground Petroleum Chronic or Moderate • Saturated thickness of sediment (thickness of Low • Active UST and LUST sites are managed by DEQ. Fuel Storage hydrocarbons catastrophic Hazard standing water) above the intake is >50 feet. Susceptibility Information on these sites is available online. I Tanks (USTs) (VOCs) leaks and spills (most of the • Aquifer is semi-confined with multiple clay or suggest that the PWS take a look at the info on current & of stored fuels status of some of these sites. Leaking that impact USTs and all silt layers above the deeper semi-confined aquifer. of the LUSTs Underground groundwater. • Evidence suggests that the groundwater are located Fuel Storage throughput (amount of water moving past this site) near the Wye Tanks (LUSTs) and dilution is great in this part of the valley. and along US93, which is • Several surface water features drain the land outside of the between most of the USTs & LUSTs and the PWS 1-year GW wells. TOT) • The UST sites are managed by DEQ and are required to have spill plans, spill and leak detection, and inventory management (to detect loss). • The LUST sites are managed by DEQ to ensure minimal impacts to groundwater. Wastewater Storm water, Generally Moderate • Saturated thickness of sediment (thickness of Low • All discharges operate under a permit issued and Discharges process containing standing water) above the intake is >50 feet. Susceptibility managed DEQ. Details of these permits are available wastewater, and treated or (all are located outside the 1- • Aquifer is semi-confined with multiple clay or online and in DEQ files. It may be of some benefit to septic effluent partially treated examine these details to see if the permits reflect which can waste streams. year GW TOT silt layers above the deeper semi-confined aquifer. distance) current activities and if there have been problems with contain all sorts These discharges • Evidence suggests that the groundwater exceedences of discharges. of chemicals or are permitted, throughput (amount of water moving past this site) pathogens. but don’t really and dilution is great in this part of the valley. • If new discharges are established within the region, especially within the 1-year TOT distance, you should conform to any • Several surface water features drain the land specific process. understand the discharge and determine is there are between these wastewater discharges and the PWS barriers between that wastewater discharge and your Some are septic wells. discharges, some well intake. are storm water, • These wastewater discharges are permitted and and some appear managed (locally or by DEQ). to be process wastewater.
Page 25 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Table 10. Susceptibility Assessment Magnolia Estates PWS – Inventory Region (only) Source Contaminants Description Hazard Rating Barriers Susceptibility Management Suggestions (natural, management, or engineered) Golf Course Fertilizers, Chemicals used Moderate to • Saturated thickness of sediment (thickness of Low to Very • Friendly promotion of the use of BMPs (best pesticides / for landscape Low standing water) above the intake is >50 feet. Low management practices) and effective IPM (integrated herbicides and greens (located • Aquifer is semi-confined with multiple clay or Susceptibility pest management) to reduce applications rates and (SOCs) maintenance. volumes. Applications of straddling the silt layers above the deeper semi-confined aquifer. outside border ag chemicals are • Evidence suggests that the groundwater of the 3-year at concentrations throughput (amount of water moving past this site) GW TOT typically well and dilution is great in this part of the valley. distance) above those for • Several surface water features drain the land Note the golf edible crops and between golf course and the PWS wells. are followed by course is seen heavy watering. on the aerial • These applicators are trained and certified, and photo at the receive continuing education. southeast • Applications are done according to label corner of the restrictions, best management practices (BMPs) and region. utilizing integrated pest management (IPM). Agricultural Fuels (VOCs, Routine handling Low Hazard • Saturated thickness of sediment (thickness of Very Low • Be a good neighbor and cultivate a positive Land Use hydrocarbons), and application (low standing water) above the intake is >50 feet. Susceptibility relationship with local agricultural landowners to (chemical pesticides & of farm encourage best management practices on those handling, herbicides chemicals percentage in • Aquifer is semi-confined with multiple clay or the region) silt layers above the deeper semi-confined aquifer. properties. A couple of fruit baskets are less expensive application, (SOCs), (fertilizers than a water treatment plant on your PWS. spills, or fertilizers and/or pesticides • Evidence suggests that the groundwater concentrations (mostly and herbicides). throughput (amount of water moving past this site) • Ensure that drainage of surface water does not allow of animals) nitrogen), and Spills of these and dilution is great in this part of the valley. the collection of water in the vicinity of the wellheads, animal wastes chemicals or fuel especially if the area has been cropped or grazed by • Several surface water features drain the land cattle. leaks from between the areas of agricultural land use and the equipment. PWS wells. Concentrations of animals can concentrate animal wastes. Note: • Many of these suggested activities can end up functioning as additional barriers that will stand between the potential contaminant source and the wells. They will each reduce the potential impacts to the drinking water from this PWS.
Page 26 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR
REFERENCES
Freeze, R. Allan and Cherry, John A., 1979. Groundwater. Prentice-Hall, Inc.
Internet source of graphical and tabular information provided by Montana State Library - Natural Resource Information Service: http://nris.state.mt.us/mapper/.
Internet source of tabular well information at the Montana Bureau of Mines and Geology Information Service: http://mbmgsun.mtech.edu/, http://mbmggwic.mtech.edu/.
Geomatrix Consulting, Inc., 2007. PWS-6 (Source Water Protection Delineation) and Preliminary Hydrogeologic Assessment Report, for the Flying H Event Center PWS. Report was written for Territorial-Landworks, Inc., Missoula, Montana.
Kendy, E. and R.E. Tresch, 1996. Geographic, Geologic, and Hydrologic Summaries of Intermontane Basins of the Northern Rocky Mountains, Montana: U.S. Geological Survey Water Resources Investigations Report 96- 4025, 233 p.
Montana Bureau of Mines and Geology, 1982. Open File Report 99, vol. 2, 132 p.
Montana Bureau of Mines and Geology, 1968. Geology and Ground Water Resources of the Kalispell Valley, Northwestern Montana, MBMG Bulletin 68, 42 p., Konizenski and others.
Montana Bureau of Mines and Geology, 1986. Groundwater Resources and Water Quality of the Unconfined Aquifers in the Kalispell Valley, Montana, MBMG Open File Report 177, Noble and Stanford.
Montana Bureau of Mines and Geology, 2001. Montana Ground-Water Assessment Flathead Lake Area, Atlas 2, Part B, Maps 1-11, MBMG Open File Versions
Montana Department of Environmental Quality, 1999. Montana Source Water Protection Program, Approved by EPA in November 1999, inclusive of personal communications with Joe Meek & Jeffrey F. Herrick in 2007 and 2008.
Montana Department of Environmental Quality, Permitting & Compliance Division and the Drinking Water Assistance Program - Montana Water Center: Ground Water Manual for Small Water Systems, January 1999.
Montana State Library - Natural Resources Information System (NRIS) map base of the USGS Topographical coverage at 1:24,000 scale in MrSID format.
Raines, G.L. and B.R. Johnson, 1996. Digital Representation of the Montana State Geologic Map: A Contribution to the Interior Columbia River Basin Ecosystem Management Project: U.S. Geological Survey Open File Report 95-691, 19 p.
United States Environmental Protection Agency (US EPA), Manual of Small Public Water Supply Systems, US EPA Office of Water (WH-550), EPA 570/9-91-003, May 1991.
Page 27 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR U.S. Geological Survey, 2000. National Landcover Dataset, Montana. 30-meter electronic digital landcover dataset interpreted from satellite imagery.
Page 28 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR GLOSSARY
Acute Health Effect. An adverse health effect in which symptoms develop rapidly.
Alkalinity. The capacity of water to neutralize acids.
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.
Delineation. A process of mapping source water management areas.
Effective Porosity. The percent of soil, sediment, or rock through which fluids, such as air or water, can pass. Effective porosity is always less than total porosity because fluids cannot pass through all openings.
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 an area expected to contribute water to a public water supply well within a fixed distance or a specified groundwater time-of-travel distance.
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 or virus 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.
Porosity. The percent of soil, sediment, or rock filled by air, water, or other fluid.
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Public Water Supply (PWS). A system that provides piped water for human consumption to at least 15 service connections or regularly serves 25 individuals.
SIC Code. The U.S. Standard Industrial Classification (SIC) Codes classify categories of businesses. SIC Codes cover the entire range of business categories that exist within the economy.
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.
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. 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.
Total Maximum Daily Load (TMDL). The total pollutant load to a surface water body from point, non-point, and natural sources. The TMDL program was established by section 303(d) of the Clean Water Act to help states implement water quality standards.
Turbidity. The cloudy appearance of water caused by the presence of suspended matter.
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.
Volatile Organic Compounds (VOC). Any organic compound that evaporates readily to the atmosphere (e.g. fuels and solvents).
Recharge Region / Watershed. The land area that drains into a stream; the watershed for a major river may encompass a number of smaller watersheds that ultimately combine at a common delivery point.
**Definitions taken from EPA’s Glossary of Selected Terms and Abbreviations and other sources.
Page 30 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR FIGURES Figure 1 Regional Map
Figure 2 Area Map
Figure 3 Subdivision Map
Figure 4 Geologic Map
Figure 5 Inventory Region Map
Figure 6 Recharge Region
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APPENDICES
Appendix A DEQ PWS’s Database Output (for Magnolia Estates) List of PWS Facilities Sampling Schedule Water Quality Data
Page 32 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Appendix B Sanitary Surveys Well Log Information Other Relevant Well Information
Page 33 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Appendix C Concurrence Letter
Page 34 of 35 Magnolia Estates PWS # MT0004021 Draft SWDAR Appendix D PWS-6 Report / SWDAR for Flying H Event Center (2007)
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