Source Water Delineation and Assessment Report

 

 

 

 

 

 

City of Red Lodge

 

 

 

 

PWSID MT0000314

 

 

 

Report Date: March 14, 2003

Revised: April 11, 2003

 

 

 

Certified Operator: 

Wayne Tominich,

406-446-1606

 

 

Owner:

City of Red Lodge

PO BOX 45

Red Lodge, Mt.  59007

406-446-1606


TABLE OF CONTENTS

Introduction.. 4

Purpose. 4

Limitations. 4

CHAPTER 1 - BACKGROUND.. 5

The Community. 5

Geographic Setting. 5

General Surface- and Ground-water Setting. 5

The Public Water Supply. 6

Water Quality. 6

Monitoring and Enforcement Actions. 6

CHAPTER 2 - DELINEATION.. 7

Hydrogeologic Conditions. 7

The Occurrence of Ground Water: 8

Conceptual Model. 10

Surface Water Intake and Wells. 11

Delineation. 11

CHAPTER 3 – INVENTORY.. 13

Inventory Method. 13

Inventory Results/Control Zones. 14

Inventory Results/Inventory Regions. 14

Inventory Result/Spill Response Region and Recharge Region. 15

Inventory Update. 15

Inventory Limitations. 15

CHAPTER 4 - SUSCEPTIBILITY ASSESSMENT.. 16

Management Option: 19

CHAPTER 5 - Monitoring Waivers. 22

Waiver Recommendation: 22

Monitoring Waiver Requirements: 22

Figures. 26

Figure 1 – Site Location Map. 26

Figure 2 – Climate Data Summary for Red Lodge – Imbedded in Text page 5. 26

Figure 3 – Inventory Map with other PWSs in the Red Lodge Area. 26

Figure 4 – Stream Hydrograph for Rock Creek – Imbedded in text page 8. 26

Figure 5 – Well Hydrograph – Imbedded in text page 9. 26

Figure 6 – Well Depth Histogram for the Red Lodge Bench Area Wells – Imbedded in text page 9. 26

Figure 7 – Well Depth Histogram for West Fork of Rock Creek Wells – Imbedded in text page 10. 26

Figure 8 – General Geology of the Red Lodge Area (Modified from Lopez, 2001). 26

Figure 9 – Land Cover in the Spill Response Region. 26

Figure 10 – Land Cover in the Watershed / Recharge Region. 26

Appendicies. 27

Appendix A - Well Logs. 28

Monitoring Well (near water plant.) 31

Appendix B - Sanitary Survey. 32

Appendix C - Listing of Potential Contaminant Sources by Standard Industrial Code (SIC). 33

Appendix D - Water Quality Monitoring History from DEQ PWS’s Database. 34

 Inorganic Water Quality Sampling Results – Red Lodge PWS. 34

Bacteriological Sampling Data  - Red Lodge PWS. 36

Appendix E – Short-term Hydrologic Study of the Red Lodge Bench (Warren, 2000) 37

Appendix F - Concurrence Letter & Other Correspondence. 38

GLOSSARY*. 39

 

LIST OF TABLES

Table 1 – Public Water Supplies in the Red Lodge Area...................................................................................... 5

Table 2.  Information from drillers logs from wells near the city of Red Lodge..................................................... 11

Table 3.  Note: Time-Of-Travel Calculations are not used, therefore Table 4 is not included.............................. 12

Table 3.  Significant potential contaminant sources in the inventory region of Red Lodge public water system wells. 15

Table 4.  Hazard of Potential Contaminant Sources, Determination of For Surface Water Sources...................... 16

Table 5. Hazard of potential contaminant sources for PWSs using ground water.................................................. 17

Table 6. Susceptibility to potential contaminant sources based on hazard and the presence of barriers.................. 17

Susceptibility Assessment Results................................................................................................................ 18

Table 7.  Susceptibility Assessment for Significant Potential Contaminant Sources in the Inventory, Spill Response, and Watershed Regions for the Red Lodge Public Water Supply............................................................................................. 18

 


 

Introduction

 

This Source Water Delineation and Assessment Report, also known as a SWDAR, was completed by Jim Stimson, Hydrogeologist with Montana Department of Environmental Quality (DEQ).

 

Purpose

This report is intended to meet the technical requirements for completion of the delineation and assessment report as 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 whereby areas that contribute water to aquifers or surface water bodies that are used to supply drinking water are identified on a map. These areas are called source water protection areas.  Assessment involves identifying locations in the delineated 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 is to provide information that helps Red Lodge  protect their drinking water source.

 

Limitations

This report was prepared to assess threats to the Red Lodge public water system and is based on published information and information obtained from local residents familiar with the community. The terms “drinking water supply” or “drinking water source” refer specifically to the source of the Red Lodge public water system and not any other public or private water system.  Also, not all of the potential or existing sources of ground water or surface water contamination in the area are identified.  Only potential sources of contamination in areas that contribute water to Red Lodge public water system wells are considered.

 

The term “contaminant” is used in this report to refer to constituents for which Maximum Contaminant 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.

 


CHAPTER 1 - BACKGROUND

 

The Community

Red Lodge is located in Carbon County near the Beartooth Mountains, and about 60 miles southwest of Billings, Montana.  The town has a population of about 2,278 (Census and Economic Information Center, 2002), and represents the seat of Carbon County.  Carbon County has a population of about 9,552.  There are 15 public water supplies (PWSs) in the Red Lodge area (Figure 3 and 11).  Three of the PWSs are classified as community systems that serve 25 or more year round residences and the remainder are non-community transient PWSs that serve a transient population.  Table 1 below lists the PWSs and the source of water they use.

 

            Table 1 – Public Water Supplies in the Red Lodge Area.

 

 

 

 

Geographic Setting

Red Lodge is located in the Rock Creek Valley at 45.1858 latitude and -109.2468 longitude (decimal degrees).  This location is about 5,627 feet above sea level and is within the Upper Yellowstone Watershed (HUC # 10070006).  The Rock Creek Valley is approximately ½ mile wide at Red Lodge.  Rock Creek’s West Fork valley is about ¼ mile wide near the confluence with the main stem and narrows as it approaches the Beartooth Mountain Front.  Mountain peaks within the Beartooth Range rise above 10,000 feet above sea level and relief between the peaks and valley floor is on the order of 5,000 feet.

 

The average daily high and low temperatures at Red Lodge are 78°F and 49°F in July and 33°F and 12°F in January (Figure 2).  Precipitation averaging 24.27inches annually is heaviest in April and May.  Average annual snowfall is 125.0 inches with the largest average accumulation coming in April (Western Regional Climate Center).

 

General Surface- and Ground-water Setting

Red Lodge obtains part of its public water supply from a surface water intake located on the West Fork of Rock Creek.  The intake is located about one half-mile up-stream from the West Fork’s confluence with main stem of Rock Creek (Figure 3).  Red Lodge also uses two wells.  The city’s primary well (Well 1) is located in town and the backup well (Well 2) is located within the West Fork drainage approximately ¼ mile up stream from the surface water intake (Figures 1 and 3).  Well 1 is 74 feet deep and is used as the primary supply well.  Well 2 is 67 feet deep and is used as a backup well.  Both wells are completed in course gravel beds that are part of the Pinedale age glacial outwash deposits in the West Fork and main stem valleys.  The aquifer serving the two Red Lodge wells is interpreted to be unconfined, based on well logs information for the area.  According to the Source Water Protection Program criteria, an unconfined aquifer is considered highly sensitive to potential sources of contamination (Montana DEQ, 1999).  Surface water is also considered to be highly sensitive.

 

The Public Water Supply

Information on a public water supply’s individual sources, system layout, and water treatment is normally obtained from sanitary surveys that are completed every three to five years for community public water supplies.  No sanitary surveys are on record at the DEQ for the city of Red Lodge and as a result no information is available for the public water supply to include in this SWDAR.  No information is available indicating if the city of Red Lodge treats water from the two supply wells or the surface water intake.  Information will be added to this report when it becomes available either from the DEQ or city of Red Lodge. 

 

Water Quality

Data are not available for either Rock Creek or its West Fork.

 

Monitoring and Enforcement Actions

Red Lodge routinely monitors its water for compliance with drinking water standards.  Bacteriological monitoring occurs monthly.  There were no positive detects for bacteria during the last five years of monitoring.  Compliance with other drinking water standards is based on additional sampling on a variety of schedules depending on system classification and population served. There were no detects of regulated contaminants for any of Red Lodge’s sources during the past five years with the exception of nitrate.  Nitrate can come from human or animal wastes but also occurs naturally.  The highest level detected in Red Lodge’s water in the last five years was 1.28 mg/l, considerably below the maximum concentration level of 10 mg/l set by the U.S. Environmental Protection Agency (EPA).   Water quality monitoring results for inorganic constituents and for bacteria for the last five years are included in Appendix D.


CHAPTER 2 - DELINEATION

 

The source water protection areas for the Red Lodge public water system are delineated in this chapter.  The purpose of delineation is to map the source of the water supply's drinking water and to define areas within which to prioritize source water protection efforts.  Four types of management regions are mapped; they are the control zone, inventory region, recharge region for the city’s water supply wells, and a spill response region for the surface water intake.

  

The goal of management in the control zone is to avoid introducing contaminants directly into the water supply's well or immediate surrounding areas.  The inventory region should be managed to prevent contaminants from reaching the well before natural processes reduce their concentrations.  The goal of management in the recharge region and the surface water buffer is to maintain and improve water quality over long periods of time or increased usage.

 

Hydrogeologic Conditions

 

Geologic Setting:

Red Lodge is located within the Rock Creek Valley near the Beartooth Mountain front (Figure 1).  The Beartooth Mountains are composed of a large uplifted block of Precambrian metamorphic rocks (Reheis, 1987), and most of the rocks have a chemical composition similar to granite.   Uplift of the Beartooth block is thought to have taken place sometime between 55 and 34 Million Years Before Present (MYBP).  This interpretation comes from the observation that the Fort Union Formation, which is Paleocene in age (65 to 55 MYBP), was folded during the uplift of the Beartooth range, and other mountain ranges in southwestern Montana, while younger formations deposited during Eocene time (approximately 55 to 34 MYBP) were not folded (Alt and Hyndman, 1995).  The uplift of the Beartooth block had a strong influence on the development of alpine glaciers, patterns of erosion and the subsequent distribution of sedimentary deposits in the Red Lodge vicinity that are now used to supply ground water.   Figure 8 shows the geology in the vicinity of Red Lodge.

 

The area around Red Lodge can be subdivided into four geographical areas with distinct geology, geologic structure, and hydrologic characteristics (Feltis, 1987).  Geographic areas include the 1) Alpine area, 2) Beartooth Front, 3) Upland Plains, and 4) Stream Drainage Valleys.  The Precambrian metamorphic rocks of the Beartooth Mountains represents the Alpine area.  Younger Paleozoic sedimentary limestone and sandstone formations flank the Alpine area.  The formations are steeply dipping and form a band of hills that are referred to as cuestas and hogbacks. This area makes up the Beartooth Front and it is between 1 and 3 miles wide.  The Paleozoic rocks are thought to have been present on top of the Beartooth block (Alpine area) at one time but were removed by erosion during and after the uplift took place.  Beyond the mountain front there is an area of rolling hills composed of flat to steeply dipping Mesozoic and Cenozoic sedimentary rocks.   This represents an Upland Plains area and it includes prominent glacial terrace deposits adjacent major streams.  The Fort Union Formation is exposed at the land surface in the Upland Plans area.  Streams have eroded down through the terrace deposits, and in some cases have reworked the terrace sediments into relatively thin deposits of alluvium adjacent the streams.  The present day stream systems and alluvial deposits make up the Stream Drainage Valleys area as described by Feltis (1987).  Feltis (1987) used these geographic areas to help describe the variety of settings in which ground water occurs in the Boulder and Stillwater river basins northwest of Red Lodge.  The geographic areas will also be used in this report to discuss the ground water resources in the Rock Creek drainage and the source water used by the city of Red Lodge.

 

The Beartooth Mountains were heavily glaciated during the last ice age in the Pleistocene Epoch.  Three separate episodes of glacial advance are recognized in this area and, from oldest to youngest, are referred to as the Buffalo, Bull Lake, and Pinedale (Ritter, 1967).  Deposited of poorly sorted boulders, gravel, sand, and clay were left behind when the glaciers retreated.  The deposits are referred to as glacial till or as a glacial moraine.  Lateral moraines are present flanking the main stem of Rock Creek and the upper reaches of the West Fork (Figure 8).  During multiple episodes of glacial retreat, melt water from the alpine glaciers eroded and reworked the till to produce terrace deposits consisting primarily of gravel with some lenses of sand and clay.   These deposits are sometimes referred to as glaciofluial deposits because they result from the action of glaciers and glacial melt water. There are at least five terrace surfaces at different elevations above the valley floor in the Rock Creek drainage near Red Lodge (Ritter, 1967).  Studies of the glacial deposits in the Red Lodge area also show that soils developed on the glacial tills during periods of glacial retreat.  Soils are generally characterized by horizons of decomposed rock, increased red coloration, increased silt and clay content, and higher calcium carbonate content than non-soil horizons. (Reheis, 1987).  The increased silt, clay, and calcium carbonate in the paleo-soils reduce their porosity and their ability to transport water.

 

The Occurrence of Ground Water:

Although wells encounter ground water in all of the geographic areas described above, wells completed in the gravel and sands deposits within the terraces of the Upland area and within the Stream Drainage Valley areas often encounter more productive aquifers than wells completed in the other geographic settings.  The city of Red Lodge obtains its source water directly from the West Fork of Rock Creek and from wells completed in the glaciofluvial deposits located beneath the West Fork’s valley.  Discussion of Red Lodge’s source water will focus on the Red Lodge Bench, also known as the West Bench, which is a glacial terrace deposit immediately north of the West Fork of Rock Creek and on glaciofluvial deposits mapped as Pinedale Bench gravels that lie beneath the West Fork’s valley (Figures 1 and 3).

 

Red Lodge Bench: The Red Lodge Bench is a prominent terrace deposit that extends east-northeast from the mountain front out on to the plains beyond the city of Red Lodge (Figures 1, 3, and 8). The terrace is composed primarily of sorted gravel with lesser amounts of sand and clay that form discontinuous lenses (Ritter, 1967).  Ritter (1967) showed that the Red Lodge Bench gravel is on the order of 115 feet thick near the mountain front and thins to 15 feet about 17 miles from the mountain front.  Reheis (1987) described soil development on this bench with the B-horizon (where iron, carbonate, and clay accumulate) ranging in thickness between 5 feet near the mountain front and 1.5 feet near its distal end.  Elevation on the Red Lodge Bench ranges from about 6,220 feet above seal level (ft. asl) near the mountain front to 5,760 ft. ASL at the base of the terrace scarp near Red Lodge (Figures 1 and 3). The scarp typically rises 40 to 100 feet above the valley floor.  

 

Ground-water recharge to the bench comes from a combination of precipitation, snowmelt runoff, irrigation return flows, and leakage from Willow Creek and irrigation canals.  There are at least 5 diversion canals flowing on top of the bench and one other canal flows along the terrace’s southern edge (Figures 1 and 3).  An indication that the bench aquifer receives recharge from surface water sources is apparent by comparing a hydrograph from Rock Creek and a hydrograph from a monitoring well in the area.  Figure 4 shows the stream hydrograph for the period September 1976 through October 1980.  The hydrograph shows a consistent pattern of increasing streamflow during spring runoff, a maximum flow near the end of June, a steady decline through the winter, and a minimum flow in March or April.   Figure 5 is a hydrograph for the Remington Ranch Well showing changes in water level within the well over a 16-month period (Warren, 2000).  This well, and other wells on the Red Lodge Bench, indicates that water level in the bench aquifer increase from May to early July and then decrease from mid-July to April. The pattern is very similar to the stream hydrograph and shows the bench aquifer receives recharge from naturally flowing, and diverted, surface water runoff. 

 

A short-term study by Warren (2000) suggests that ground water flow is generally from the southern end of the Red Lodge Bench to the north.  Contours of the water table surface are approximately parallel to the topographic contours and ground water flow is directed perpendicular to the contours (See Figure 5 of Warren’s report: Appendix F).   Warren’s Figure 5 also shows a steep gradient on the water table near the southern edge of the bench just north of the city of Red Lodge. The lower part of the bench scarp in this area is fairly heavily vegetated.  Both the steep gradient and the vegetation suggest that some volume of ground water flows from the bench aquifer into the upper part of the aquifers that are present beneath the valleys of Rock Creek and its West Fork. 

 

Well information for 124 wells located on the Red Lodge Bench was retrieved from the Ground Water Information Center (GWIC) at the Montana Bureau of Mines and Geology (MBMG) for this report on January 8, 2003.  Figure 6 shows a frequency distribution of total depth of wells on the bench.  Figure 6 indicates that the majority of wells on the bench are relatively shallow, ranging between 30 and 60 feet deep.  The 60 wells that are between 30 and 60 feet deep represent 48% of the 124 wells on the bench.  Average depth for the bench wells is 91 ft. below land surface (ft. bls) and the maximum depth is 505 ft. BLS.  Average static water level for wells on the bench is 24 ft. BLS.  Pumping water level average is 53 ft. BLS and average yield for wells in this area is 42 gallons per minute (gpm) with a maximum yield listed at 500 gpm.  Well logs show that the majority of the wells are completed in gravel deposits.  Results from pumping tests in this area are sparse but Warren (2000) presented transmissivity and pumping rates from several ground water studies on the bench.  Transmissivity values ranging from 77,000 to 94,000 gallons per day per foot (gpd/ft) and pumping rates of 300 to 400 gpm.  Warren also states that nearby wells were not adversely affected by sustained pumping in the ranged mentioned.  Several well logs on the bench indicate the presence of a red clay horizon between 40 and 50 feet bls that does not transmit water as readily as the rest of the terrace gravel.  As mentioned above, these clay horizons could act as confining units between the shallow and deeper aquifers within the terrace gravel deposits.

 

West Fork of Rock Creek Valley:  Rock Creek and its West Fork have cut down through the terrace gravel deposits to form conspicuous valleys (Figures 1, 3, and 8).  The West Fork joins the main stem of Rock Creek about 1.5 miles southwest of Red Lodge and its valley extends southwest to the Beartooth Front and beyond into the core of the mountain range.  Material beneath the valley floor is composed dominantly of gravel and sand, and appears to be in on the order of 100 to 130 feet thick in the lower part of the West Fork’s valley.   Sandstones and coal beds that are likely part of the Fort Union Formation are penetrated by some wells in the valley at depths on the order of 100 feet.  Studies of ground water and the terrace deposits all mention that the depth to bedrock is variable throughout this area (Ritter, 1967, Reheis, 1987, and Feltis, 1987).

 

Ground-water recharge to the aquifer beneath the West Fork’s valley comes from a combination of precipitation, snowmelt runoff, leakage from the West Fork of Rock Creek, and at least one irrigation canal that crosses the valley about a half mile above the confluence with the main stem of Rock Creek.  The timing and pattern of recharge to this aquifer is very likely similar to that of the Red Lodge Bench discussed above. Some component of recharge may also come from bedrock beneath the gravel deposits.  Snowmelt runoff coming down the West Fork valley, and beneath the valley within the aquifer, is probably the dominant source of recharge for the aquifer used by the city of Red Lodge wells.

 

Well information for the West Fork valley for about 31 wells was retrieved from the GWIC database at the Montana Bureau of Mines and Geology (MBMG) for this report on January 8, 2003.   Figure 7 (West Fork Histogram) shows a frequency distribution of total depth for wells tapping the aquifer beneath the West Fork valley.  About 75 percent of the wells in this area are between 10 and 120 feet deep.  Average depth is 116 ft. below land surface (ft. bls) and the maximum depth is 310 ft. BLS.  Average static water level for wells in the West Fork Valley is 51 ft. BLS.  Pumping water level average is 64 ft. BLS and average yield for wells in this area is 92 gallons per minute (gpm) with a maximum yield listed at 1,040 gpm.  Gravels appear to be the most common aquifer material for this area.  Red clay or shale beds do not appear to be present in this gravel deposit beneath the West Fork’s valley.  No pumping test result could be located for wells in this area so the transmissivity range is unknown. 

 

Conceptual Model

The terrace gravel deposits that form the Red Lodge Bench hosts an aquifer that is used by a substantial number of wells that encounter the aquifer between 30 and 60 feet below the land surface.  The aquifer is interpreted to be unconfined.  Recharge originates from leakage from 5 or more irrigation canals flowing on top of the bench and from irrigation return flow. 

 

The aquifer used by most wells in the West Fork of Rock Creek valley ranges between 10 and 120 feet below the valley floor and is interpreted to be distinct from the shallow aquifer on the Red Lodge Bench.  The aquifer present in Rock Creeks main stem valley and in the West Fork appears to be unconfined.  Rock Creek and its West Fork are the dominant sources of recharge to this aquifer.  Some component of recharge within the West Fork comes from an irrigation ditch that diverts water from the main stem of Rock Creek and crosses the West Fork valley in route to the Red Lodge Bench (Figure 3).  Some recharge to the valley aquifer comes from the flank of the Red Lodge Bench immediately north of the West Fork Valley.   Figure 3 shows the general direction of ground water flow within the West Fork valley and on the Red Lodge Bench.  The largest component of the ground water is flowing to the north-northeast within the Red Lodge Bench and the gravel deposits beneath the West Fork valley.  Near the edge of the Red Lodge Bench there is a component of ground water flow from the bench into the upper part of the aquifer beneath the West Fork valley (Figure 3).

 

Surface Water Intake and Wells

Red Lodge’s surface water intake is located on the West Fork of Rock Creek fairly near the confluence with the main stem (Figures 1 and 3).  Red Lodge’s primary supply well (Well 1) is reported as 74 feet deep, has a static water level of 20 feet below the land surface and a reported yield of 900 gallons per minute (gpm), see Appendix A.  This well is located at 713 S. Grant Street.  Well 2, the city’s backup well, is located near the surface water intake southwest of town and is listed as 67 feet deep with a static water level of 8 feet below land surface.  The well log shows a yield of 1,040 gpm during a 5 hour pumping test (Appendix A).  This well is screened between 40 and 65 feet below the land surface.  Well construction information is summarized in Table 2.

 

                        Table 2.  Information from drillers logs from wells near the city of Red Lodge.

MBMG #

Well  # 1

(M13267)

Well  # 2 (M179787)

Location

07S 20E 34 BAACC

08S20E04 BD

Date Completed

9/17/1961

12/31/1999

Depth (ft. bgs*)

74

67

Screened Interval  (ft)

NA

40 to 65

SWL Depth (ft bgs)

20

8

PWL Depth (ft bgs)

NA

NA

Drawdown (ft bgs)

NA

NA

Test Pumping Rate (gpm**)

900

1,040

Specific Capacity (gpm/ft dd***)

NA

NA

*Feet below ground surface; ** Gallons per minute; *** Gallons per minute per foot of

drawdown.

 

Delineation

Methods and criteria for delineating source water protection areas are specified in the Montana Source Water Protection Program (DEQ, 1999).  Source water protection areas delineated for Red Lodge include a spill response region for the surface water intake; controls zones for each well, a common inventory region for the wells based on hydrogeologic mapping of the West Fork Valley, and a recharge region based on the 11 digit hydrologic unit 10070006140.

 

Control Zones - 100-foot radius control zones are delineated for the wells; all sources of potential contaminants should be excluded in this region.  All potential contaminant sources are identified within the control zone (Figure 3).

Inventory Region – A common inventory region is delineated for the wells based on hydrogeologic mapping of the aquifer beneath Rock Creek’s main stem and West Fork’s valley.  The inventory region outlines a portion of the aquifer that is interpreted to provide water to the Red Lodge public water supply wells.  The region extends from a position down gradient from Well 1 in Red Lodge to the main stem and West Fork’s valley margins, and up-valley to the Beartooth Front where both stream valleys become narrow (Figure 3).  The upper boundary of the Inventory Region is about 1 mile upstream from Well 2 and about 4 miles upstream from Well 1 (Figure 3).  The inventory region encompasses the area from which water or contaminants can flow into Red Lodge’s ground water source over a period of months to years.  All potential contaminant sources are identified within the Inventory Region.

 

Spill Response Region - This region extends one half mile from each bank of the West Fork of Rock Creek (Figure 10). The region also extends one half mile below the surface water intake and ten miles upstream from the intake.  All potential contaminant sources are identified within the Spill Response Region.

 

Table 3.  Note: Time-Of-Travel Calculations are not used, therefore Table 4 is not included.


CHAPTER 3 – INVENTORY

 

An inventory of potential contaminant sources was conducted to assess the susceptibility of Red Lodge’s wells and the west spring to contamination and to provide a foundation for source water protection planning.  The inventory for the park focuses on facilities that generate, use, or store potential contaminants and certain land uses in the inventory region delineated in the previous section.  Sources of all primary drinking water contaminants and cryptosporidium are identified, although only potential sources of contaminants that are the greatest threat to human health were selected for detailed inventory.  The contaminants of greatest concern to Red Lodge are nitrate, microbial contaminants, and agricultural chemicals including fertilizers and pesticides (SOCs).

 

Inventory Method

Databases were searched to identify businesses and land uses that are potential sources of regulated contaminants.  The following steps were followed:

 

Step 1: Land cover is identified from the National Land Cover Dataset compiled by the U.S. Geological Survey and U.S. Environmental Protection Agency (USGS, 2000).  Land cover types in this dataset were mapped from satellite imagery at 30-meter resolution using a variety of supporting information.

 

Step 2: EPA’s Envirofacts System was queried to identify EPA regulated facilities.  This system accesses the following databases: Resource Conservation and Recovery Information System (RCRIS), Biennial Reporting System (BRS), Toxic Release Inventory (TRI), Permit Compliance System (PCS), 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 is a significant potential contaminant source.

 

Step 3: DEQ databases were queried to identify underground storage tanks (UST), hazardous waste contaminated sites, landfills, and abandoned mines.

 

Step 4: A business phone directory was consulted to identify businesses that generate, use, or store chemicals in the inventory region.  Equipment manufacturing and/or repair facilities, printing or photographic shops, dry cleaners, farm chemical suppliers, and wholesale fuel suppliers were targeted by SIC code.

 

Step 5: Major road and rail transportation routes were identified.

 

Step 6: All significant potential contaminant sources were identified in the inventory region, sources of nitrate and microbial contaminants were identified in the surface water buffer, and land uses and facilities that generate, store, or use large quantities of hazardous materials were identified within the recharge region.

 

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

 


1)      Large quantity hazardous waste generators

2)      Landfills

3)      Hazardous waste contaminated sites

4)      Underground storage tanks

5)      Major roads or rail transportation routes

6)      Cultivated cropland


7)      Animal feeding operations

8)      Wastewater lagoons or spray irrigation

9)      Septic systems

10)  Sewered residential areas

11)  Storm runoff

12) Floor drains, sumps, or dry wells


Inventory Results/Control Zones

Land within the control zone of Well 1 includes city streets, several buildings, and municipal sewer lines (Figure 3).  It is not known what businesses currently occupy these building or if hazardous materials are used, stored, or transported near the Well 1.  The location of Well 1 within the city means municipal sewer lines and other potential contaminant sources surround the well.  Potential contaminant sources in such close proximity to the well within the control zone represent a high hazard to Well 1.  The control zone for Well 2 is largely undeveloped (Figure 3).  Structures present in the area appear to be related to the surface water filtration plant.  It is not known if the wellhead is fenced and locked.  It is also not known if any hazardous materials are stored on site or if herbicides are used for weed control in and around the immediate area.

 

Inventory Results/Inventory Regions

Land cover in the inventory region is 57 percent grassland, 32 percent forestland and 5 percent commercial or industrial.  Figure 3 shows a pie chart with the land cover percentages and Figure 9 shows the land cover is distributed within the inventory region and spill response region.   With the exception of the commercial – industrial land cover, these land cover types are not considered to be potential sources of contamination, and therefore, they do not pose a threat to city’s source water.  The commercial – industrial land cover is of concern even though it represents a relatively small area within the inventory region because is in such close proximity to Well 1.  Potential contaminant sources within this area include storm water drains, Class V injection wells (floor drains or French drains), and municipal sewer lines.  Spraying for weed and pest control near streets, or in some cases within buildings would also represent a potential threat to the well.   The commercial – industrial land cover represents a high hazard to Well 1. 

 

There are three underground fuel storage tanks directly up-gradient from Well 1 (Figure 3).  Two of the sites have leak histories.  There is also a small area of high septic density located directly up-gradient from the Well 1.  Well 2, on the other hand is located up-gradient from Red Lodge and the potential sources of contamination that are located there. (Figures 3 and 10).   Individual septic systems are considered a potential contaminant source for Well 2.  Most of the land area near and up-gradient from the two city wells has a low septic density (<50 systems per square mile).  One area within the inventory region and north of Well 2 has a moderate septic density (between 50 and 300 systems per square mile) and another area down-gradient of the wells with a high septic density (>300 systems per square mile.  Due to the relatively limited aerial extent of the moderate septic density and the fact that it is located north of the creek, septic systems in the area would likely not pose a threat to the ground water and Well 2.  Septic systems in the high density area also appear to pose no threat due to the fact that the area is down-gradient from Well 2.  However, if subdivision and growth continues in the area around the water treatment plant, wells, and surface water intake, the septic density could exceed a threshold so as to compromise water quality.  Increasing nitrate load in particular would be a concern, as would pathogens originating from the septic system effluent.

 

Herbicides used for weed control by the Carbon County or the city is considered a potential contaminant source.  Spraying along roads near the wells, or around the water treatment facility itself, is of particular concern.  Herbicide application should be kept away from the wells and up-stream areas near the surface water intake. 

 

No major highways or railroad corridors are present in the inventory region.  The road to the ski area northwest of Red Lodge is the only road that would periodically carry a significant volume of traffic.  Because of its location and the nature of vehicular travel on this road, it is not considered to pose a threat to the public water supply.

 

No businesses that use or generate hazardous chemicals were identified in the inventory region. 

 


Table 3.  Significant potential contaminant sources in the inventory region of Red Lodge public water system wells.

Source

Contaminants of Concern

Underground Storage Tanks (USTs)

Fuels, hydrocarbons, VOCs

Municipal Sewer Lines

Nitrate, pathogens, VOCs, and SOCs, and others

Storm water drains

Nitrate, pathogens, VOCs, and SOCs, and others

Individual Septic Systems

Microbial contaminants and nitrate

Class V Injection Wells

Nitrate, pathogens, VOCs, and SOCs, and others

 

Inventory Result/Spill Response Region and Recharge Region

Land cover in the Spill Response Region is 78 percent forestland, 20 percent grassland, 1 percent agricultural land, and 1 percent wetland (Figure 9). Within the recharge or watershed region (HUC 10070006140) land cover is 51 percent is forestland, 34 percent grassland and shrubland, 9 percent perennial ice and snow, and 6 percent bare rock (Figure 11).   Septic density throughout the recharge region and surface water buffer zone is low, with the exception of the two areas of moderate and high density mentioned previously in the section on the Inventory Region.  As mentioned above, forest and grasslands are not considered potential contaminant sources.  Agricultural land is considered a potential contaminant sources due to the use of fertilizers, pesticides and herbicides.  The concern here is the potential for mismanagement or over- application of fertilizers and/or pesticides on the agricultural lands that could result in SOCs entering the West Fork up-stream from the city’s intake, and the aquifer up-gradient of the wells. However, the percent of agricultural land in the area is small and is not considered to pose a threat to the city’s source water. 

 

Inventory Update

The certified water system operator will update the inventory for his records every year.  Changes in land uses or potential contaminant sources will be noted and additions made as needed.  The complete inventory will be submitted to DEQ every five years.

 

Inventory Limitations

The potential sources of contaminants described above are identified from readily available information.  Consequently, unregulated activities or unreported contaminant releases may have been overlooked.  The use of multiple sources of information, however, should ensure that the major threats to the source water for Red Lodge have been identified.


CHAPTER 4 - SUSCEPTIBILITY ASSESSMENT

 

The susceptibility of Red Lodge’s wells and the surface water intake to contamination is assessed in this chapter.  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 reach the PWS’s source water.  The proximity of a potential contaminant source to the source water or the density of non-point potential contaminant sources determines the threat of contamination, referred to here as hazard (Table 4).  Time-of-travel (TOT) calculations are not used to assign hazard to potential contaminant sources in the Red Lodge area. 

 

For the wells, hazard is based on whether a potential contaminant source is located within the inventory region, its size and proximity to the wells, and on the toxicity of the hazardous material handled or used at the site.  For the surface water intake, the hazard presented by point sources of contaminants depends on whether they are located within the spill response region and the contaminants can discharge directly into the West Fork of Rock Creek or its tributaries.  Point source hazard is also dependent on the health affects associated with potential contaminants. Hazard ratings for point and nonpoint sources are assigned based on criteria listed in Table 5. 

 

Barriers can be anything that decreases the likelihood that contaminated water will reach the Red Lodge wells or surface water intake. For wells barriers can be engineered structures, management actions or natural conditions.  Examples of engineered barriers are spill catchment structures for industrial facilities and leak detection for underground storage tanks.  Emergency planning and best management practices can be considered management barriers.  Thick clay-rich soils, a deep water table or a thick saturated zone above the well intake can be natural barriers.  For a surface water intake examples of barriers include: a vegetated riparian area, protective forest management practices, and dilution.  Table 6 shows how barriers are used to reduce the susceptibility rating applied to a given potential contaminant source.

 

Table 4.  Hazard of Potential Contaminant Sources, Determination of For Surface Water Sources





Potential Contaminant Sources

High Hazard Rating

Moderate Hazard Rating

Low Hazard Rating

Point Sources of Nitrates or Pathogens

Potential for direct discharge to surface water

Potential for discharge to groundwater hydraulically connected to surface water

Potential contaminant sources in the watershed region

Point Sources of VOCs, SOCs, or Metals

Potential for direct discharge of large quantities from roads, rails, or pipelines

Potential for direct discharge of small quantities to surface water

Potential for discharge to groundwater hydraulically connected to surface water

Septic Systems (density)

More than

300 per sq. mi.

50 – 300

per sq. mi.

Less than

50 per sq. mi.

Municipal Sanitary Sewer

(percent land use)

More than 50 percent of region

20 to 50 percent

of region

Less than 20 percent of region

Cropped Agricultural Land

(percent land use)

More than 50 percent of region

20 to 50 percent

of region

Less than 20 percent of region

 

 

 

 

Table 5. Hazard of potential contaminant sources for PWSs using ground water.





Potential Contaminant Source

High Hazard

Moderate Hazard

Low Hazard

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

(percent land use)

More than 50 percent of region

20 to 50 percent of region

Less than 20 percent of region

Cropped Agricultural Land

(percent land use)

More than 50 percent of region

20 to 50 percent of region

Less than 20 percent of region

 

Table 6. Susceptibility to potential contaminant sources based on hazard and the presence of barriers.

 

High Hazard

Moderate Hazard

Low Hazard

No Barriers

Very High

Susceptibility

High

Susceptibility

Moderate

Susceptibility

One Barrier

High

Susceptibility

Moderate

Susceptibility

Low

Susceptibility

Multiple Barriers

Moderate

Susceptibility

Low

Susceptibility

Very Low

Susceptibility

 

Red Lodge’s public water supply Well 2 and the surface water intake are located up gradient and up-stream from the town and the majority of identified potential contaminant sources (Figures 1, 3, and 9).  Those potential contaminant sources outside of the immediate Red Lodge area are either outside the West Fork drainage or located substantial distances from the intake and well field so as to not represent a threat to the city’s public water supply.  In addition, most of the land in the watershed above the Well 2 and the intake is undeveloped forestland and wilderness (Figures 9 and 10).  As a consequence, none of the potential contaminant sources identified in and around Red Lodge are considered to represent a threat to the source water originating from the surface water intake or Well 2.  However, it is worth noting that septic density on the Red Lodge Bench just north of the West Fork of Rock Creek and within a portion of the West Fork valley changed from low to moderate sometime during the period 1990 to 2000.  As noted previously, a relatively small area of moderate septic density occurs within the inventory region a little over a half-mile up-stream from the water supply wells (Figure 3).  Septic systems are considered a potential contaminant source and could pose a threat to the source water if development becomes more wide spread in the West Fork valley.

 

City Well 1on the other hand is susceptible to the multiple potential contaminant sources in the southern part of the City of Red Lodge.  The well’s location is surrounded by city streets, city services infrastructure like the municipal sewer lines, and several businesses that are considered to be potential contaminant sources.  Table 7 summarizes the potential contaminant sources for the City of Red Lodge, ranks the hazard for each source, lists identified barriers, and shows the final susceptibility rating.

 

 

 

 

 


Susceptibility Assessment Results

Table 7.  Susceptibility Assessment for Significant Potential Contaminant Sources in the Inventory, Spill Response, and Watershed Regions for the Red Lodge Public Water Supply.

Source

ID Number on Map in Figure 3

Contaminant

Hazard

Hazard Rating

Barriers

Susceptibility

Management

Municipal Sewer Lines & Storm water drains

1

Nitrate, pathogens, VOCs, and SOCs, and others

Leaks in sewer mains to groundwater, which may reach surface water

High

None

Very High

Ongoing testing and maintenance of lines and system, replacement of old lines, compliance with current regulations for discharges

 

- Educational workshops provided to the general public by the city, county, or state promote safe handling and proper storage, transport, use, and disposal of hazardous materials.

Underground Storage Tanks (USTs)

2 through 4

Fuels, hydrocarbons, VOCs

Spills, leaks impacting groundwater and/or reaching surface water

High

- Modern construction, spill detection, spill containment  and monitoring,

- Remediation for historic leaks

High

Continue monitoring and encourage state and local officials to proceed to have leaking sites mitigated.

Individual Septic Systems

5 through 7

Microbial contaminants and nitrate

Infiltration into shallow ground water and possible discharge to surface water.

Low

- Stream represents hydrologic barrier for shallow ground water

- Relatively small area of moderate septic density within the inventory region

 

Low

- Manage development in the West Fork valley up-stream of the intake and supply wells..

Class V Injection Wells

Not Numbered on  the map

Nitrate, pathogens, VOCs, and SOCs, and others

Infiltration of contaminants into aquifer

Unknown

None

Unknown

Inventory; Provide educational information, materials and resources to business owners and the public on proper waste disposal and recycling


 

Management Option:

 

Municipal Sewer System – The potential hazard imposed by pathogens and nitrate originating from the city’s municipal sewer and storm water mains located near Well 1 is high.   Other potential contaminants like household hazardous wastes including solvents and cleansers, pesticides, and herbicides (VOCs and SOCs) are also of concern.  Due to the fact that Well 1 is located in the city and in close proximity to the mains, there are no barriers exist to prevent leaks from entering the aquifer near the well.   A completed well log is not available for Well 1 and therefore it is not known if the well is properly sealed.  Susceptibility to leaks from the mains is rated very high.

 

UST/LUSTs- The potential hazard imposed by VOCs and hydrocarbons is high for three tank sites, two with leak histories, within the Inventory Region (Figure 3).  Overall, the susceptibility is rated as high due to the presence of several barriers including spill prevention and remediation (removal of leaking tanks). 

 

Septic Systems – Areas of high and moderate septic density are located within the Inventory and Spill Response Regions (Figure 3).  The high density area is relatively small and likely does not pose a threat to any of the city’s water supply sources.  The moderate density area that lies up-stream from the surface water intake and up-gradient from Well 2 is relatively small and is not likely to pose a threat to the public water supply.  However as noted above, continued growth and subdivision in the West Fork drainage could reach a threshold where septic systems could have a negitive impact on the shallow ground water and surface water. It may be advisable to encourage future development and subdivision to areas outside of the West Fork valley, and away from the Red Lodge Bench’s southern-most edge above the public water supply wells and surface water intake.  Hazard is low and susceptibility  to pathogens and nitrate from septic systems is rated as low.

 

Assorted Businesses in Town- Appendix C lists various businesses in town that are considered to represent non-significant potential contaminant sources based on the criteria within the Source Water Protection Guidelines (DEQ, 1999).  Based on their location with respect to the public water supply Well 2 and the surface water intake, these businesses are not considered to pose a threat to the Red Lodge Public Water Supply.  Some of the sites may represent significant potential contaminant sources for Well 1 and other public water supplies in and around Red Lodge.  A positive and proactive step to reducing the risk of unnecessary contamination in the community from these potential sources is to provide educational information and resources to business owners and the public on proper waste disposal and recycling. 

 

Class V Injection Wells – The potential hazard imposed by VOCs, SOCs, pathogens, nitrate, and other contaminants originating from the class V injection wells cannot be determined due to the fact that no inventory of Class V well is complete for most of Montana or the current inventory is inadequate.  The susceptibility of the intake to contaminants originating from this source is unknown. 

 

Management Recommendations

It should be noted that even small releases of some chemicals in close proximity to a public supply well or surface water intake can have significant negative impact on water quality, and is therefore a significant threat to the public water supply.  Steps can be taken to reduce the likelihood of releases in the source water for the PWS or in the vicinity of the sources. Some of these steps (considered management recommendations) are listed below.

 

Some management recommendations are also included in the susceptibility table for the Red Lodge PWS (Table 7).  If these, and other, management recommendations are implemented, they may be considered additional barriers that will reduce the susceptibility of the intake to specific sources and contaminants.

 

 

Management recommendations fall into the following categories:

 

·        Retiring Well 1 and using Well 2 and other city wells in the West Fork Valley as primary water supply wells.

·        Sewer maintenance and leak detection

·        Municipal sewer extension

·        Agricultural best management practices

·        Stormwater management

·        Proper disposal and monitoring of oil and gas production wastewater

·        Education

·        Emergency Response Planning

 

Retiring Well 1  - This option may have already been considered and deemed unfeasible for a variety of reasons.  However, from a Source Water Protection stand point, removing Well 1 from the Red Lodge public water supply system would reduce the susceptibility of the city’s source water to several potential contaminant sources, namely, the municipal sewer lines and the underground fuel storage tank sites.  By utilizing the surface water intake, Well 2, and possibly other city wells in the West Fork Valley, the city’s source water would originate from an area up-stream and up-gradient from all of the potential contaminant sources located in and around the city.  If development in the West Fork Valley remain at or near the current level, susceptibility to septic systems in the West Fork Valley should not pose a threat to the public water supply.

 

Sewer Maintenance and leak detection – Early warning of leaks and scheduled replacement of aging sewer lines may reduce the susceptibility of the City’s PWS to contamination from municipal septic wastes, and could also benefit other public water supplies in the Glendive area.

 

Sewer Extension – Installation of advanced septic treatment systems such as sand filters can limit contamination from new rural residential development, however, annexation and extension of sewers is the only way to reduce contamination from existing unsewered developments.

 

Agricultural and silvicultural best management practices (BMPs) – BMPs that address application and mixing of fertilizer and pesticides are a viable alternative to prohibition of their use. BMPs may also be utilized to minimize surface runoff and soil erosion on cultivated fields. Erosion control, selective logging, and other silvicultural practices (essentially BMPs) should be considered on a county-wide basis. BMPs are generally voluntary but their implementation can be encouraged through education and technical assistance. County planning can help promote the implementation of BMP on lands that are outside city limits but indirectly affect the city PWS.

 

Education - Educational workshops provided to the general public by the city, county, or state promote safe handling and proper storage, transport, use, and disposal of hazardous materials. Ongoing training provided to designated emergency personnel will promote the efficiency and effectiveness of emergency responses to hazardous material spills. Likewise, educational workshops provided to rural homeowners will promote the proper maintenance and replacement of residential septic systems. The EPA and the State of Montana can provide educational materials on these topics.

 

Hazardous Materials Collection Days – Several counties in the state that have vulnerable water supplies have implemented scheduled days for the collection of hazardous wastes from the public. These vary in the inclusiveness of what materials are collected, how the materials are handled, and how they are disposed of, but they all act to reduce the amount of unauthorized or improper disposal of these wastes. Used motor oil collection station could be established and available to the public on a regular basis.

 

Emergency Response Plan – Several counties have compiled Emergency Response Plans that were then adopted by the local communities. The usefulness and effectiveness of a response plan are maximized if it contains a clear listing of all emergency contacts, emergency numbers, and resources available within the county to respond to an emergency situation, such as a hazardous material spill. Emergency plans are not difficult to develop or distribute, but have a significant benefit to the citizens and municipalities within the county.

 

The City’s public water supply operators, the city administration, and the Carbon County administration can consider these management recommendations along with their ongoing efforts to protect the public water supply. Should contamination reach the town's intake, the City and County will likely need to work cooperatively to address remediation or relocation of the intake.


 

CHAPTER 5 - Monitoring Waivers

 

Waiver Recommendation:

Currently, the city of Red Lodge has a water quality monitoring wavier for Phase 2 Inorganic constituents that includes Barium, Cadmium, Chromium, Fluoride, Mercury, Selenium.  However, based on past monitoring results and the susceptibility assessment of the wells and surface water intake, the Red Lodge PWS may be eligible for additional monitoring waivers.  In particular, the Phase 5 waiver may be applicable and includes Antimony, Thallium, Beryllium, and Nickel.  Prior to requesting additional waivers, the PWS Operators would be encouraged to carefully review the following section on Monitoring Waiver Requirements.  If after reviewing this section it is determined that an additional waiver is feasible, the Red Lodge PWS should submit a letter with the proper documentation to DEQ requesting monitoring waivers.   Table 9 shows how identified potential contaminant sources effects the eligibility for monitoring waivers.   The PWS also needs to provide additional information to DEQ regarding chemical use within the inventory region.

 

Table 9. Susceptibility Assessment as it relates to waiver eligibility for significant potential contaminant

sources in the Spill Response Region Glendive PWS surface water intakes.

Source

Contaminant

Susceptibility

Waiver Eligibility

Municipal Sewer and Storm Water Mains

Nitrate, pathogens, VOCs, and SOCs, and others

Very High

Waivers are not available for pathogens and nitrate

UST/LUST Sites

VOCs, fuels, petroleum products

High

The number of sources in the Red Lodge likely precludes a waiver 

Septic Systems

Pathogens, nitrate

Low

Waivers are not available for pathogens and nitrate

Assorted Businesses in Town

VOCs, SOCs, petroleum hydrocarbons, metals, pathogens, nitrate

Low, except when located near Well 1

Chemical use likely precludes waivers for some chemicals

Waivers are not available for pathogens and nitrate

Class V Injection Wells

VOCs, SOCs, pathogens, nitrate

Unknown

Waivers are not available for pathogens and nitrate

 

Monitoring Waiver Requirements:

The 1986 Amendments to the Safe Drinking Water Act require that community and non-community PWSs sample drinking water sources for the presence of volatile organic chemicals (VOCs) and synthetic organic chemicals (SOCs). The US EPA has authorized states to issue monitoring waivers for the organic chemicals to systems that have completed an approved waiver application and review process. All PWSs in the State of Montana are eligible for consideration of monitoring waivers for several organic chemicals. The chemicals diquat, endothall, glyphosate, dioxins, ethylene dibromide (EDB), dibromochloropropane (DBCP), and polychlorinated biphenyls are excluded from monitoring requirements by statewide waivers.

 

Use Waivers

A Use Waiver can be allowed if through a vulnerability assessment, it is determined that specific organic chemicals were not used, manufactured, or stored in the area of a water source (or source area). If certain organic chemicals have been used, or if the use is unknown, the system would be determined to be vulnerable to organic chemical contamination and ineligible for a Use Waiver for those particular contaminants.

 

Susceptibility Waivers

If a Use Waiver is not granted, a system may still be eligible for a Susceptibility Waiver, if through a vulnerability assessment it is demonstrated that the water source would not be susceptible to contamination. Susceptibility is based on prior analytical or vulnerability assessment results, environmental persistence, and transport of the contaminants, natural protection of the source, wellhead protection program efforts, and the level of susceptibility indicators (such as nitrate and coliform bacteria). The vulnerability assessment of a surface water source must consider the watershed area above the source, or a minimum fixed radius of 1.5 miles upgradient of the surface water intake. PWSs developed in unconfined aquifers should use a minimum fixed radius of 1.0 mile as an area of investigation for the use of organic chemicals. Vulnerability assessment of spring water sources should use a minimum fixed radius of 1.0 mile as an area of investigation for the use of organic chemicals. Shallow groundwater sources under the direct influence of surface water (GWUDISW) should use the same area of investigation as surface water systems; that is, the watershed area above the source, or a minimum fixed radius of 1.5 miles upgradient of the point of diversion. The purpose of the vulnerability assessment procedures outlined in this section is to determine which of the organic chemical contaminants are in the area of investigation.

 

Given the wide range of landforms, land uses, and the diversity of groundwater and surface water sources across the state, additional information is often required during the review of a waiver application. Additional information may include will logs, pump test data, or water quality monitoring data from surrounding public water systems; delineation of zones of influence and contribution to a well; Time-of-Travel or attenuation studies; vulnerability mapping; and the use of computerized groundwater flow and transport models. DEQ’s PWS Section and DEQ’s Source Water Protection Program will conduct review of an organic chemical monitoring waiver application. Other state agencies may be asked for assistance.

 

Susceptibility Waiver for Confined Aquifers

Confined groundwater is isolated from overlying material by relatively impermeable geologic formations. A confined aquifer is subject to pressures higher than atmospheric pressure that would exist at the top of the aquifer if the aquifer were not geologically confined. A well that is drilled through the impervious layer into a confined aquifer will enable the water to rise in the borehole to a level that is proportional to the water pressure (hydrostatic head) that exists at the top of a confined aquifer.

 

The susceptibility of a confined aquifer relates to the probability of an introduced contaminant to travel from the source of contamination to the aquifer. Susceptibility of an aquifer to contamination will be influenced by the hydrogeologic characteristics of the soil, vadose zone (the unsaturated geologic materials between the ground surface and the aquifer), and confining layers. Important hydrogeologic controls include the thickness of the soil, the depth of the aquifer, the permeability of the soil and vadose zones, the thickness and uniformity of low permeability and confining layers between the surface and the aquifer, and hydrostatic head of the aquifer. These factors will control how readily a contaminant will infiltrate and percolate toward the groundwater.

 

The Susceptibility waiver has the objective of assessing the potential of contaminants reaching the groundwater used by the PWS. A groundwater source that appears to be confined from surface infiltration in the immediate area of the wellhead may eventually be affected by contaminated groundwater flow from elsewhere in the recharge area. Contaminants could also enter the confined aquifer through improper well construction or abandonment where the well provides a hydraulic connection from the surface to the confined aquifer. The extent of confinement of an aquifer is critical to limiting susceptibility to organic chemical contamination. Regional conditions that define the confinement of a groundwater source must be demonstrated by the PWS in order to be considered for a confined aquifer susceptibility waiver. Confinement of an aquifer can be demonstrated by pump test data (storage coefficient), geologic mapping, and well logs. Site specific information is required to sufficiently represent the recharge area of the aquifer and the zone of contribution to the PWS well. The following information should be provided:

 

·        Abandoned wells in the region (zone of contribution to the well),

·        Other wells in the region (zone of contribution to the well),

·        Nitrate/Coliform bacteria analytical history of the PWS well,

·        Organic chemical analytical history of the PWS well,

 

Susceptibility Waiver for Unconfined Aquifers

 

Unconfined aquifers are the most common source of usable groundwater. Unconfined aquifers differ from confined aquifers in that the groundwater is not regionally contained within relatively impervious geologic strata. As a result, the upper groundwater surface or water table in an unconfined aquifer is not under pressure that produces hydrostatic head common to confined aquifers.

 

Unconfined aquifers are usually locally recharged from surface water or precipitation. In general, groundwater flow gradients in unconfined aquifers reflect surface topography, and the residence time of water in the aquifer is comparatively shorter than for water in confined aquifers. Similar water chemistry often exists between unconfined groundwater and area surface water, and physical parameters and dissolved constituents can be an indicator of the hydraulic connection between groundwater and surface water. Consequently, unconfined aquifers can be susceptible to contamination by organic chemicals migrating from the ground surface to groundwater.

 

The objective of the susceptibility waiver application is to assess the potential of organic chemical migration from the surface to the unconfined aquifer. The general procedures make use of a combination of site specific information pertaining to the location and construction of the source development, monitoring history of the source, geologic characteristics of the unsaturated soil and vadose zones, and chemical characteristics of the organic chemicals pertaining to their mobility and persistence in the environment. The zone of contribution of the unconfined groundwater source must be defined and plotted. This should describe the groundwater flow directions, gradients, and a 3-year time-of-travel. All surface bodies within 1,000 feet of the PWS well(s) must be plotted. Analytical monitoring history of the PWS well and those nearby should be provided as well.

 


REFERENCES

 

Census and Economic Information Center, 2002, Year 2000 Census Data Population Estimates for Red Lodge, Montana. Montana Department of Commerce.

 

Feltis, R. D. and Litke, D. W., 1987, Appraisal of Water Resources of the Boulder and Stillwater River Basins, Including the Stillwater Complex, South-Central Montana: Montana Bureau of Mines and Geology Memoir 60, p120.

 

Reheis, M. C., 1987, Soils in Granitic Alluvium in Humid and Semiarid Climates along Rock Creek, Carbon County Montana, USGS Bulletin 1590-D.

 

Ritter, Dale F., 1967, Terrace Development along the Front of the Beartooth Mountains, Southern, Montana.  Geological Society of America Bulletin, V. 78, p. 467-484.

 

Montana DEQ, 1999.  Montana Source Water Protection Program, Approved by EPA in November 1999.

 

Uthman, Bill, 2002, An Evaluation of the Potential fro Adverse Impacts from the Development of Ground Water by the City of Red Lodge, Carbon County, Montana.  Montana Department of Natural Resources and Conservation file: City of Red Lodge Application 43D-30001172 for Water Use Permit.

 

U.S. Geological Survey, 2000.  National Landcover Dataset, Montana.  30-meter electronic digital landcover dataset interpreted from satellite imagery.

 

Warren, Kirk, 2000, Groundwater Levels at the South End of the Red Lodge Bench near Red Lodge, Montana.  Limited-Scope Investigation: Montana Department of Natural Resources and Conservation (DNRC), p.20.

 

Yuretich, Richard F., and Hicks, Jason F., 1986, Sedimentology and Facies Relationships of the Belfry Member, Fort Union Formation, Northern Bighorn Basin, p. 53-69. Montana Geologic Society – YBRA Field Conference Publication.

 


Figures

Figure 1 – Site Location Map

Figure 2 – Climate Data Summary for Red Lodge – Imbedded in Text page 5.

Figure 3 – Inventory Map with other PWSs in the Red Lodge Area.

Figure 4 – Stream Hydrograph for Rock Creek – Imbedded in text page 8.

Figure 5 – Well Hydrograph – Imbedded in text page 9.

Figure 6 – Well Depth Histogram for the Red Lodge Bench Area Wells – Imbedded in text page 9.

Figure 7 – Well Depth Histogram for West Fork of Rock Creek Wells – Imbedded in text page 10.

Figure 8 – General Geology of the Red Lodge Area (Modified from Lopez, 2001).

Figure 9 – Land Cover in the Spill Response Region

Figure 10 – Land Cover in the Watershed / Recharge Region


Appendicies


Appendix A - Well Logs

Primary Well for Red Lodge (AKA: Well 1)

Montana Bureau of Mines and Geology
Ground-Water Information Center Site Report
CITY OF RED LODGE - WELL 1 SOURCE 2

 

Location Information

GWIC Id:

132671

Source of Data:

LOG

Location (TRS):

07S 20E 34 BAACC

Latitude (dd):

45.1800

County (MT):

CARBON

Longitude (dd):

-109.2513

DNRC Water Right:

W045736-00

Geomethod:

MAP

PWS Id:

00314003

Datum:

1927

Block:

64

Certificate of Survey:

 

Lot:

3

Type of Site:

WELL

Addition:

HYPER

 

 

Site Notes:

TRACT LOCATION AND LAT\LONG BASED ON ADDRESS FROM DEQ. 713 SOUTH GRANT.

Well Construction and Performance Data

Total Depth (ft):

74.00

How Drilled:

 

Static Water Level (ft):

20.00

Driller's Name:

 

Pumping Water Level (ft):

 

Driller License:

 

Yield (gpm):

900.00

Completion Date (m/d/y):

9/17/1961

Test Type:

 

Special Conditions:

 

Test Duration:

 

Is Well Flowing?:

 

Drill Stem Setting (ft):

 

Shut-In Pressure:

 

Recovery Water Level (ft):

 

Geology/Aquifer:

Not Reported

Recovery Time (hrs):

 

Well/Water Use:

PUBLIC WATER SUPPLY

Well Notes:

 

 

Hole Diameter Information

No Hole Diameter Records currently in GWIC.

Casing Information1

No Casing Records currently in GWIC.

Annular Seal Information

No Seal Records currently in GWIC.

Completion Information1

No Completion Records currently in GWIC.

Lithology Information

No Lithology Records currently in GWIC.

1 - All diameters reported are inside diameter of the casing.

These data represent the contents of the GWIC databases at the Montana Bureau of Mines and Geology at the time and date of the retrieval. The information is considered unpublished and is subject to correction and review on a daily basis. The Bureau warrants the accurate transmission of the data to the original end user. Retransmission of the data to other users is discouraged and the Bureau claims no responsibility if the material is retransmitted. Note: non-reported casing, completion, and lithologic records may exist in paper files at GWIC.

 


Backup Well for Red Lodge (AKA: Well 2)

Montana Bureau of Mines and Geology
Ground-Water Information Center Site Report
CITY OF RED LODGE

 

Location Information

GWIC Id:

179787

Source of Data:

LOG

Location (TRS):

08S 20E 04 BD

Latitude (dd):

45.1575

County (MT):

CARBON

Longitude (dd):

-109.2693

DNRC Water Right:

 

Geomethod:

TRS-TWN

PWS Id:

 

Datum:

1927

Block:

 

Certificate of Survey:

 

Lot:

 

Type of Site:

WELL

Addition:

 

 

 

Site Notes:

 

Well Construction and Performance Data

Total Depth (ft):

67.00

How Drilled:

ROTARY

Static Water Level (ft):

8.00

Driller's Name:

ROCK CREEK

Pumping Water Level (ft):

 

Driller License:

WWC104

Yield (gpm):

1040.00

Completion Date (m/d/y):

12/31/1999

Test Type:

AIR

Special Conditions:

 

Test Duration:

20.00

Is Well Flowing?:

 

Drill Stem Setting (ft):

40.00

Shut-In Pressure:

 

Recovery Water Level (ft):

 

Geology/Aquifer:

Not Reported

Recovery Time (hrs):

5.00

Well/Water Use:

DOMESTIC

Well Notes:

 

 

Hole Diameter Information

From

To

Diameter

0.0

20.0

17.0

20.0

67.0

14.0

Casing Information1

From

To

Dia

Description

-2.0

65.0

12.0

STEEL

Annular Seal Information

From

To

Description

0.0

20.0

BENTONITE

Completion Information1

From

To

Dia

Description

40.0

65.0

12.0

SCREENS

Lithology Information

From

To

Description

0.0

64.0

BLACK/WHITE/GRAVEL/BOULDERS

64.0

67.0

TAN/CONGLOMERATE/DECOMP


Monitoring Well (near water plant.)


Montana Bureau of Mines and Geology
Ground-Water Information Center Site Report
RED LODGE THE CITY OF * RL#1

 

Location Information

GWIC Id:

173039

Source of Data:

 

Location (TRS):

08S 20E 04 BCDC

Latitude (dd):

45.1596

County (MT):

CARBON

Longitude (dd):

-109.2766

DNRC Water Right:

 

Geomethod:

NAV-GPS

PWS Id:

 

Datum:

1983

Block:

 

Certificate of Survey:

 

Lot:

 

Type of Site:

WELL

Addition:

 

 

 

Site Notes:

10/15/02 - SITE LOCATED AT RED LODGE CITY WATER FILTRATION PLANT. GO SOUTH ON HWY. 212 OUT OF RED LODGE. 1.1 MILE PAST WEST FORK RD. (ROAD TO SKI AREA). GO WEST ON SMALL ASPHALT ROAD (WATER WORKS RD.)APROX. 0.5 MI. TO FILTRATION PLANT. WELL LOCATED 75 YDS. EAST OF LARGE BRICK PLANT BUILDING ON NORTH SIDE OF ROAD. VISIBLE.

Well Construction and Performance Data

Total Depth (ft):

60.00

How Drilled:

ROTARY

Static Water Level (ft):

 

Driller's Name:

B & H

Pumping Water Level (ft):

 

Driller License:

WWC309

Yield (gpm):

 

Completion Date (m/d/y):

8/15/1998

Test Type:

 

Special Conditions:

 

Test Duration:

 

Is Well Flowing?:

 

Drill Stem Setting (ft):

 

Shut-In Pressure:

 

Recovery Water Level (ft):

 

Geology/Aquifer:

112OTSH

Recovery Time (hrs):

 

Well/Water Use:

TEST WELL

Well Notes:

10/15/02 - 6 IN. STEEL CASING WITH BOLT-ON CAP. NO PUMP OR POWER. WELL DRILLED FOR MONITORING PURPOSES.

 

Hole Diameter Information

From

To

Diameter

0.0

80.0

6.0

Casing Information1

From

To

Dia

Description

-2.0

60.0

6.0

STEEL

Annular Seal Information

From

To

Description

0.0

20.0

BENTONITE

Completion Information1

From

To

Dia

Description

60.0

75.0

5.0

80 PERFS

Lithology Information

From

To

Description

0.0

72.0

BOULDERS SAND & GRAVEL

72.0

80.0

DECOMPOSED CONGLOMERATE

 

 


Monitoring Well (near water plant.)

Montana Bureau of Mines and Geology
Ground-Water Information Center Site Report
RED LODGE THE CITY OF * RL#2

 

Location Information

GWIC Id:

173042

Source of Data:

LOG

Location (TRS):

08S 20E 04 CBB

Latitude (dd):

45.1600

County (MT):

CARBON

Longitude (dd):

-109.2750

DNRC Water Right:

 

Geomethod:

NAV-GPS

PWS Id:

 

Datum:

1927

Block:

 

Certificate of Survey:

 

Lot:

 

Type of Site:

WELL

Addition:

 

 

 

Site Notes:

 

Well Construction and Performance Data

Total Depth (ft):

69.00

How Drilled:

ROTARY

Static Water Level (ft):

9.00

Driller's Name:

B & H

Pumping Water Level (ft):

 

Driller License:

WWC309

Yield (gpm):

892.0

Completion Date (m/d/y):

8/31/1998

Test Type:

 

Special Conditions:

 

Test Duration:

4.00

Is Well Flowing?:

 

Drill Stem Setting (ft):

 

Shut-In Pressure:

 

Recovery Water Level (ft):

9.00

Geology/Aquifer:

Not Reported

Recovery Time (hrs):

0.50

Well/Water Use:

TEST WELL

Well Notes:

 

 

Hole Diameter Information

From

To

Diameter

0.0

69.0

8.0

Casing Information1

From

To

Dia

Description

-4.0

52.0

8.0

STEEL

65.0

69.0

7.0

STEEL

Annular Seal Information

From

To

Description

0.0

20.0

BENTONITE

Completion Information1

From

To

Dia

Description

52.0

65.0

7.0

8 TELESCOPE SCREENS

Lithology Information

From

To

Description

0.0

44.0

GRAVEL BOULDERS SAND

44.0

63.0

ROCK & GRAVEL

63.0

69.0

DECOMPOSED CONGLOMERATE


Appendix B - Sanitary Survey

 


Appendix C - Listing of Potential Contaminant Sources by Standard Industrial Code (SIC).


Appendix D - Water Quality Monitoring History from DEQ PWS’s Database


 Inorganic Water Quality Sampling Results – Red Lodge PWS




Bacteriological Sampling Data  - Red Lodge PWS



Appendix E – Short-term Hydrologic Study of the Red Lodge Bench (Warren, 2000)


Appendix F - Concurrence Letter & Other Correspondence


GLOSSARY*

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

 

Alkalinity.  The capacity of water to neutralize acids.

 

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

 

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

 

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

 

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

 

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

 

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

 

Delineation.  A process of mapping source water management areas.

 

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

 

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

 

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

 

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

 

Maximum Contaminant Level (MCL).  Maximum concentration of a substance in water that is permitted to be delivered to the users of a public water system.  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 sources that are diffuse and do not have a single point of origin.

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

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

 

Transmissivity.  The ability of an aquifer to transmit water.

 

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

 

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

 

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

 

* Definitions taken from EPA’s Glossary of Selected Terms and Abbreviations