report - invermere water€¦ · overburden geology the overburden geological deposits covering the...

October 2010

DISTRICT OF INVERMERE

BACKGROUND REVIEW AND CONCEPTUAL HYDROGEOLOGICAL MODEL OF THE DEEP MUNICIPAL AQUIFER

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Report Number: 10-1348-0021

Distribution:

2 Copies District of Invermere

1 Copy Urban Systems Ltd.

2 Copies Golder Associates Ltd.

Submitted to:District of Invermere 914 - 8 Avenue P.O. Box 339 Invermere, B.C. V0A 1K0


October 2010 Report No. 10-1348-0021 i

Table of Contents

1.0 INTRODUCTION ............................................................................................................................................................... 1

2.0 PHYSICAL SETTING ....................................................................................................................................................... 4

2.1 Regional Physiography ........................................................................................................................................ 4

3.0 EXTENT OF DEEP AQUIFER .......................................................................................................................................... 4

4.0 DEGREE OF CONFINEMENT/AQUIFER VULNERABILITY ........................................................................................... 8

5.0 GEOPHYSICAL FORWARD MODELLING .................................................................................................................... 10

5.1 Scope of work .................................................................................................................................................... 10

5.2 Background Data ............................................................................................................................................... 10

5.3 Methods ............................................................................................................................................................. 10

5.4 Results ............................................................................................................................................................... 11

6.0 GAP ANALYSIS AND RECOMMENDATIONS .............................................................................................................. 14

7.0 CLOSURE ....................................................................................................................................................................... 15

TABLES

Table 1: Deep Water Well Data and Survey Notes .................................................................................................................... 3

Table 2: Resistivity and Conductivity Ranges .......................................................................................................................... 10

Table 3: Resistivity Model - Borehole GW01-04 ....................................................................................................................... 11

FIGURES

Figure 1: Regional Geology and Geological Cross-Section ....................................................................................................... 5

Figure 2: Water Well Location .................................................................................................................................................... 6

Figure 3: Deep Aquifer Elevation ............................................................................................................................................... 7

Figure 4: Cross-Section A-A' ...................................................................................................................................................... 9

Figure 5a&b: Test well GW01-04 Resistivity Modelling (100 Ohm-m aquifer resistivity) .......................................................... 12

Figure 6a&b: Test well GW01-04 Resistivity Modelling (200 Ohm-m aquifer resistivity) .......................................................... 13

APPENDIX A Records of Deep Water Wells


October 2010 Report No. 10-1348-0021 1

1.0 INTRODUCTION Golder Associates Ltd. (Golder), in association with Urban Systems Ltd. (USL) has been retained by the District

of Invermere (the District) to undertake an Aquifer Protection Plan as outlined in our joint proposal of

April 7th, 2010. Phase 1 of the study included the compilation of baseline information and the following tasks:

Gathering records from the B.C. Ministry of Environment’s Water Resources Atlas database for several

deeper wells that may penetrate the Deep Aquifer including any water quality and/or quantity reports that

are available.

Compiling available data and using it to construct a conceptual hydrogeological model of the Aquifer. The

model will be used to develop initial interpretations of the Deep Aquifer extent, aquifer hydraulic

characteristics, potential vertical “windows” through the overlying surficial aquifer (i.e., Aquifer #603) and

the relative vulnerability of the Deep Aquifer.

Field audits of wells that are interpreted to penetrate the Aquifer, including:

interviewing well owners regarding water quantity and quality and well use

obtaining owner’s records/logs for subject wells and for any unregistered wells identified during the

interviews

acquiring GPS locations for audited wells; and

where possible, obtaining water level measurements in audited wells

Consider the viability of utilizing geophysical methods to examine and interpret the physical attributes of the

Deep Aquifer. The conceptual model will be used to evaluate the potential effectiveness of common

geophysical survey techniques in supporting Golder’s interpretation of the extent of the Deep Aquifer.

Compile the data acquired through the above desktop data review/compilation and field work (i.e., well

audit) into GIS format compatible with the District’s current system.

Complete a gap analysis to identify critical hydrogeological information that is missing and additional

investigation(s) required to fill those gaps, if required. The limitations of the existing information will be

quantified and the risks of proceeding without further field investigations identified.

Background Information

In addition to the provincial water well database on the B.C. Water Resources Atlas web site, Golder compiled

and reviewed a number of existing geological and hydrogeological maps and reports on the Invermere area.

These included the following reports prepared by Golder and USL:

Golder Associates Ltd. (1999). Results of Groundwater Supply Investigation, Lake Windermere Resort,

Athalmer, British Columbia. Project number 992-2838, September 1999.

Golder Associates Ltd. (2000). Progress Report: Pumping Tests of Wells #1 and #3, Lake Windermere Resort. Project number 002-2805, April 2000.



Golder Associates Ltd. (2003). Evaluation of Groundwater Potential - District of Invermere, British Columbia. Project number 03-1324-063, September 16, 2003.

Golder Associates Ltd. (2004). Groundwater Supply Investigation in Athalmer, District of Invermere, British Columbia. Project number 03-1324-063, July 2004.

Golder Associates Ltd. (2005). Groundwater Supply Investigation on the Pointe of View Property, Invermere, British Columbia. May 2005.

Golder Associates Ltd. (2005). Groundwater Supply Investigation, Area North of Athalmer, District of Invermere, British Columbia. May 2005.

Golder Associates Ltd. (2005). Groundwater Supply Investigation in Athalmer, District of Invermere, British Columbia. May 2005.

Golder Associates Ltd. (2006). Well Construction, Testing and Assessment, District of Invermere, Production Well #1, Athalmer, British Columbia. August 2006.

Golder Associates Ltd. (2007). Manganese Concentrations and Implications of Adding Groundwater to the Municipal Drinking Water Distribution System, District of Invermere, British Columbia. December 2007.

Golder Associates Ltd. (2009). Recommended Groundwater Monitoring Program, Production Well #1, District of Invermere, British Columbia. June 2009.

Urban Systems Ltd. (2004). Water Supply Improvements (5829/P462), Draft Project Environmental Report. September 2004.

Urban Systems Ltd. (2007). Water Supply Improvements (5829/P462), Environmental Screening

Report. March 2007.

Water Well Survey

On June 28th and 29th, 2010, a Golder hydrogeologist visited the locations of each of the 18 deep wells listed in

Table 1 in order to obtain ground elevations and locations using a GPS. In addition, where wells were located,

attempts were made on two occasions to contact the well owners to obtain additional information on the use and

quality of their well water. Table 1 provides notes on these attempts and on the observations made at each site.

Where the well could be identified, GPS coordinates and ground elevations were recorded. Where the wells

could not be identified, but where coordinates were provided in the provincial water well database, ground

elevations were recorded. Where a residence was present, but no one was at home, as occurred in most cases,

a questionnaire were left with a stamped, self-addressed envelope and a letter requesting the well owner to

contact Golder or fill out and return the questionnaire. To date, none of these questionnaires have been

returned to Golder. However, the field survey was useful to obtain proper locations and ground elevations for

use of the well record information.

In a number of cases it did not appear that the well in question was present or still in use, likely because of the

more recent provision of communal piped water.

Well ID lat (deg mm.mmm) long (deg mm.mmm) elev (m) aquifer depth aquifer elev water level (m) note left? note

74824 ‐ ‐ 828 14.3 ‐ 54.6 813.7 ‐ 773.4 ‐ no could not find well elevation is typical of expected coordinates81574 50 29.946 116 00.536 810 0 ‐ 54.9 810 ‐ 755.1 ‐ yes

604 ‐ ‐ ‐ ‐ notalked to current owners of land, all on town water and no well is

known to them23528 50 30.341 116 00.734 818 47.0 ‐ 48.8 771 ‐ 769.2 ‐ yes40221 50 30.375 116 00.619 860 61.0 ‐ 103.7 809 ‐ 757 ‐ yes88458 50 30 23 116 00 39 61.6 ‐ 65.2 ‐ no could not locate

88608 50 30 32 116 00 41 ‐ 35.7 ‐ 55.5 ‐ nocoordinates lead to the bottom of a deep ravine with no easy

access from road56569 50 30.638 116 00.733 859 52.1 ‐ 55.5 806.9 ‐ 803.5 ‐ yes

54952 50 30 40 116 00 46 864 50.3 ‐ 55.5 813.7 ‐ 808.5 ‐ yesfenced area (barbed wire) with no trespassing signs. No sign of

tennants nor well. Left note tied to gate of property

559 50 30 40 116 00 55 805 61.3 ‐ 62.2 743.7 ‐ 742.8 ‐ nono well, coordinates indicate that the well location would be under

the present day road.

53640 50 30.844 116 00.771 867 51.5 ‐ 57.0 815.5 ‐ 810 ‐ yes

not at location of expected coordinates, found well just off side of the road and no other well locations plotted fit the well. Measured and left note at house on adjacent lot as this lot was empty (both

for sale with different buyers)

20632 50 30 55 116 01 2 ‐ 55.8 ‐ 62.8 ‐ nowell likely doesn't exist. Would be just off to the right as you come

into town by start of bridge.

16205 ‐ ‐ ‐ ‐ nodrove around downtown looking for this well. No evidence seen in

the field of it. Likely gone

85899 50 30.948 116 01.713 806 59.5 ‐ 72.0 746.5 ‐ 734 ‐2 nomunicipal well near rail line right of way. Measured water level in

nearby test well.

14802 50 30 16 116 01 47 818 53.7 ‐ 54.1 764.3 ‐ 763.9 ‐ nono well located. Site appears to have been built over with a combo

strip mall/apartment

74696 ‐ ‐ 820 ‐ notalked with current owner of property, he has had it since 2000 and

had never seen a water well within the block.74776 50 30 5 116 01 42 53.4 ‐ 59.5 no welll observed74775 50 30 5 116 01 44 820 51.8 ‐ 61.3 768.2 ‐ 758.7 ‐ no close to 74696 same, no well observed.

Table 1. Deep Water Well Data and Survey Notes



2.0 PHYSICAL SETTING

2.1 Regional Physiography According to J.F. Walker (Walker, 1926), the physiography of the Columbia River valley is typical of a glaciated

valley. The wide U-shaped valley has two hanging valleys, occupied by Toby Creek and Horsethief Creek,

entering it from the west. The floors of the hanging valleys are 122 to 152 m above the floor of the Columbia

River valley. The Columbia River valley is 4.8 to 9.6 km wide. The channel within the valley that contains

Windermere Lake is 1.2 km wide. The elevation of the water surface of Windermere Lake is approximately 800

m above sea level (ASL). Terraces are located at elevations of approximately 823 m, 853 m and 914 m ASL.

Overburden Geology

The overburden geological deposits covering the District of Invermere consist of Quaternary silt, sand and

gravels (Geological Survey of Canada, 1972). Based on records of water wells previously drilled within the

District of Invermere, the overburden deposits consist of sand, gravel, silts and clays ranging in thickness from 0

to at least 244 m (800 ft), with the thickest areas being in the valley. Significant deposits of alluvial and

glaciofluvial sands and gravels lie on or near the surface that are used locally as aquifers. A large alluvial fan

deposit at the mouth of Toby Creek forms a shallow aquifer in Athalmer that is tapped by many shallow wells.

The regional geology and geological cross-section of the area are provided on Figure 1.

Bedrock Geology

Sub-cropping bedrock beneath the District of Invermere is part of the Upper Proterozoic Horsethief Creek Group

which consists of slate, quartz pebble conglomerates, quartzite, feldspathic quartzite, limestones and schistose

quartzite (Geological Survey of Canada, 1972 and http://webmap.em.gov.bc.ca/mapplace).

3.0 EXTENT OF DEEP AQUIFER Based on the B.C. Water Atlas well record database, there are 18 wells in the Invermere area with aquifer

depths of between 48.4 m (160 ft) and 72 m (236 ft). The aquifer materials are all described as sand and/or

gravel. Considering the significant changes in topography in the area, it was important to obtain ground

elevations for these wells to allow an assessment of their likely continuity. Recorded or measured elevations

were obtained for only 12 of the wells as several could not be located. In a few cases’ ground elevation was

provided in the database, but for the others Golder used GPS to determine elevation at or near the well heads.

Figure 2 shows the location of the deeper wells identified and Table 1 summarizes the available data for them.

Because of the variability in the aquifer elevations, a key factor used to compare them was the water level

elevation in the wells, where it was recorded. This information was available for only seven of the wells, but it

indicates that there are two separate aquifers, a deep one with water level elevations between about 750 and

770 masl, and an intermediate one with water level elevations of approximately 815 masl. The Deep Aquifer

locations, including that intersected by the District of Invermere Production Well #1, are shown on Figure 3 and

are the focus of the following discussion.



Based on the locations where the Deep Aquifer has been identified (Figure 3), it is interpreted to extend across

the entire Columbia River Valley in the Invermere area, including beneath the lake. A deep sand and gravel

aquifer was also intersected by a Shuswap Band well about 2.1 km north of District production well PW#1,

suggesting its further extent to the north. The problem with assuming that the aquifer is continuous beneath the

valley, however, is that at least two wells in the area have been drilled to this depth without intersecting the sand

and gravel aquifer. These are a well drilled at the Lake Windermere Pointe development and one on the

ACE/Northstar lumber yard site, both in the Athalmer area. At Lake Windermere Pointe, about 0.6 km south of

District PW#1, strata at the depth of the Deep Aquifer were logged as “very fine to fine grained sand, some silt”,

which could still be considered as aquifer, although with much poorer yield potential. The test well drilled by a

developers’ group on the ACE lumber site on the north side of Athalmer intersected only “grey clay/silt” over the

typical depth of the Deep Aquifer. The well did intercept a deeper “fine sand with a trace of silt and gravel”

between 82.9m and 91.4 m (272 and 300 ft).

From the available information, which is somewhat sparse considering the large area of interest, one can

conclude that the Deep Aquifer appears to be continuous over a wide area below this portion of the Columbia

valley, although the Aquifer’s characteristics and yield potential are quite variable. In one location, the ACE

lumber site, no aquifer material was reported intersected at this depth.

Figure 3 shows only the six wells that intersected the Deep Aquifer along with the elevations at which it was

encountered. While, again, this is based on a limited number of data points, the corresponding thickness of the

aquifer indicates that it is considerably thicker (up to 12 metres) on the west side of Lake Windermere, but only a

few metres thick on the east side.

Figure 4 is a cross-section along the north-south line (A – A’) on the west side of the lake shown on Figure 3.

This section indicates that the Deep Aquifer rises significantly to the south, which would suggest that the source

of sediment was in this direction. It should be noted that no well record has been obtained for the Shuswap

Band well north of Athalmer.

4.0 DEGREE OF CONFINEMENT/AQUIFER VULNERABILITY While all overlying soil strata provide some degree of protection for underlying aquifers, confining layers are

typically considered to consist of silts, clays and mixtures of glacial soils known as tills. An aquifer that has little

or no overlying confining strata is considered to be potentially “vulnerable” to sources of contaminants related to

local land uses. As Athalmer and Invermere are in a largely developed area with varied land uses, aquifer

vulnerability should be a primary concern when selecting an aquifer for municipal supply. As reported by Golder

(2006), the deep municipal aquifer in which PW#1 was completed is considered “semi-confined” at that location,

but it has a total thickness of some 58.8 m (193 ft) of relatively fine grained strata overlying the aquifer.

Based on the stratigraphic logs of the 18 deep wells near Athalmer and east and west of Lake Windermere, the

Deep Aquifer is, for the most part, well confined and would be considered of low vulnerability within the

examined area. On the west side and northeast of the lake, confining beds vary from 29 to 46 m (95 to 152 feet)

in thickness. Further southeast, however, there are some wells where there may be little or no fine-grained

confining strata, although some of these logs are unclear. Nevertheless, this area is unlikely to be considered

for municipal supply by the District, based on its location.



5.0 GEOPHYSICAL FORWARD MODELLING

5.1 Scope of work Golder Associates Ltd. has undertaken a forward-modelling study to determine the applicability of the surface-

deployed electrical resistivity geophysical method for delineating a potential aquifer in the vicinity of Athalmer.

5.2 Background Data The soil profiles for two existing test wells were considered for this study; test wells GW01-04 and GW02-04

(near District PW#1). The potential aquifer within test well GW01-04 is identified by sand/gravel and silty sand

layers extending from an approximate depth of 59 m to 79 m below ground surface.

Test well GW02-04 identifies a gravel/sand and sand layers occurring between an approximate depth of 64 m

and 72 m below ground surface. An estimated flow rate was not indicated.

Test well GW01-04 was initially considered for the forward modelling study, since the potential aquifer in this well

log is thicker than the one identified in well log GW02-04 and would, therefore, have a greater potential for

detection using electrical resistivity methods. If it was determined that the potential aquifer in test well GW01-04

could not be identified using surface-deployed electrical resistivity methods, forward modelling would not be

undertaken for test well GW02-04.

5.3 Methods Electrical and electromagnetic geophysical survey methods are commonly used to differentiate between in-situ

soil types. As shown in Table 2, resistivity of soil and rock depends, in part, on the constituent materials. Clays

and silts are conductive (low resistivity) compared to sands and gravels. Fresh water saturation within clay-free

soils reduces resistivity in accordance with Archie’s Law. Increasing the concentration of dissolved solids,

particularly salts and metals, in groundwater normally reduces resistivity significantly. Typically, grain-size,

porosity, rock-type, temperature/ice content and water saturation are the primary factors controlling resistivity.

Table 2: Resistivity and Conductivity Ranges MATERIAL RESISTIVITY (Ohm-m) Conductivity (mS/m)

Fresh Water 100 10

Sea Water 0.2 500

Dry Sand 10-800 1.25-100

Saturated Sand 1-60 17-100

Gravel 1400 0.07

Saturated Gravel 100 10

Silts 10-700 1.4- 100

Clays 1-1000 1-100

Sand Clay/Clayey Sand 30-215 5-30

Sand and Gravel 30-225 4-30

Shale 20-2000 0.5-50

Limestone 50-5x107 2x10-5 -20

Granite 300-3x106 3.3x10-4-3



The potential aquifer identified by the two well logs is relatively deep. It was determined that a vertical electrical

sounding (1D sounding) might have the potential to identify the aquifer at this depth.

Briefly, a 1D sounding is a resistivity method that measures apparent resistivity as a function of depth below a

particular point at ground surface. Distances between current and potential electrodes are varied, resulting in a

variable penetration depth of the electrical current. The position of the measurement is taken to be the mid point

of the electrode array.

To test the sensitivity of the 1D resistivity sounding method, forward modelling was performed using a

conservative estimate of the resistivity values for the soil profile interpretation for test well GW01-04, as

illustrated in Table 3 (from Reynolds, 1997; table 7.1):

Table 3: Resistivity Model - Borehole GW01-04

Depth Interval (m) of Each Interpreted Layer

RESISTIVITY Model (Ohm-m)

0-15 29

15-22 100

22-36 29

36-40 67

40-50 30

50-56 100

56-60 29

60-80 (aquifer) 100

80-90 33

>90 30

The sensitivity of a 1D sounding was tested using the IPI2win software package.

5.4 Results Based on the information provided in the log of test well GW01-04, a forward model was derived (1a). The log of

the test well was then modelled with the 100 Ohm-m sand/gravel layer (aquifer) removed (Figure 5b). Only a

slight variation is apparent between the modelled resistivity responses of the two models.



Figure 5a&b: Test well GW01-04 Resistivity Modelling (100 Ohm-m aquifer resistivity)

In order to test the sensitivity of the forward model further, resistivity of the aquifer was increased to 200 Ohm-m

and the process was repeated. This resulted in a similar outcome (Figures 6a and 6b).



Figure 6a&b: Test well GW01-04 Resistivity Modelling (200 Ohm-m aquifer resistivity)

We, therefore, conclude that an aquifer of similar thickness occurring at a similar depth as that defined by test

well GW01-04 would likely not be detectable using surface-deployed resistivity methods. Resistivity surveying

is, therefore, not recommended as a valid means to map the major aquifer that occurs in the vicinity of the Town

of Windermere.



Based upon the results of the forward modelling for Borehole GW01-04, forward modelling was not undertaken

for test well GW02-04, which identified a thinner aquifer layer.

6.0 GAP ANALYSIS AND RECOMMENDATIONS The purpose of a gap analysis is to identify what critical information is missing to characterize the deep municipal

aquifer tapped by District production well PW#1 so that Step 2 of the B.C. Well Protection Toolkit can be

completed. As a reminder, the six steps are the following:

Form community planning team

Define well/aquifer protection area

Identify potential contaminants

Develop management strategies

Develop contingency plans

Monitor results and evaluate the Plan

Defining the well or aquifer protection area for the municipal Aquifer, or any aquifer, requires an understanding of

the aquifer’s hydraulic characteristics and extent so that modelling can take place to define well capture zones.

A protection strategy can then be developed for the well capture zones. The only alternative would be to apply

the strategy, such as land use controls, to the entire aquifer area surrounding and up-gradient of the well.

As discussed in Section 3 above, the extent of the Deep Aquifer is quite broad, as it appears to be present on

both sides of Lake Windermere and may extend northward 2 km from Athalmer to a Shuswap Band well.

However, the Aquifer is clearly not continuous beneath the full valley floor, as the test well at ACE Lumber did

not intersect it, although deeper aquifer material was reported.

Proper testing of the Deep Aquifer has been quite limited, with the 72-hour test of PW#1 being the only long-term

test of which we are aware. Since most of the other wells known to tap it are private wells, such testing is not

common.

As the District also wishes to evaluate the potential for further developing the deeper aquifer as a source of

additional water supply concurrent with the aquifer protection process, it is recommended that additional

exploratory drilling be conducted in a minimum of two locations. This will provide additional opportunity to obtain

additional relevant information on the Deep Aquifer, as well as allow for proper pumping tests to be run to

characterize it at these locations.

In order to choose locations for additional test drilling, one must consider, among other things:

the fact that there are sites to the north (ACE Lumber) and south (Windermere Pointe) where the Deep

Aquifer was not present or had poorer production potential,

the presence of a number of potential contaminant sources, and

sites available to the District for test well and/or production well drilling.


October 2010 Report No. 10-1348-0021

APPENDIX A Records of Deep Water Wells

Golder Associates Ltd.

102, 2535 - 3rd Avenue S.E.

Calgary, Alberta, T2A 7W5

Canada

T: +1 (403) 299 5600

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