LAIRD IMPROVDlElW DIslRICT

Transcription

1 LAIRD IMPROVDlElW DIslRICT GR DEVELDPMBTC PROGRAM (1988) Prepared for Ihe Laird Imprwement District KAZA GRouNmaTm CONSULTING LTD. August, 1988

2 C TABLE OF OoNIWrs TAI3LEOFCONENTS.. Page... (i) SECTION 1 INTRODUCTION SECTION 2 BACKGROUNJI Geology Existing Wells SECTION 3 DESCRIPTION OF PRESENT PROGRAM SECTION 4 RESULTS OF PROGRAM Geological Conditions Well Completion Aquifer Test Results SECTION 5 CONCLUSIONS AND RECOMMEMlATIONS APPENDIX Aquifer test data Driller's lithologs

3 The present program of groundwater exploration and developnent was carried out to obtain an additional supply of water for the Laird Improvement District. The program was undertaken at the request of Mr. Eric Williamson, a Trustee with the Laird Improvement District. In past years, the Laird subdivision has relied on a shallow drilled well as the main source of water supply. In 1971, when the existing well was first completed, the water table was near surface and the well produced approximately 60 gallons per minute (gpm). Local conditions have changed however, and in more recent years the level of the water table has dropped considerably, reducing production from the existing well to about onethird of the original capacity. Two years ago, the Improvement District constructed a shallow dug well near the original source of supply, but this only increased total production by a few gallons per minute. As a result, the subdivision has been faced with a water shortage and recently water restrictions have been imposed. With the present and future housing expansion proposed for the subdivision, the District must expand their water supply capability. Several alternatives have been considered, one of these being the completion of additional water wells. During the present program, a total of four testholes were drilled (see Section 3 for locations). Favourable conditions were encountered at the fourth site, near Fortune Creek and a test/production well was completed. Finally,a 24hour pumping test was conducted with the new well to establish a safe, longterm capacity.

4 L The following report outlines the nature of the overall program, provides a discussion of the results and includes recomnendations for a safe pumping rate, pump setting and future groundwater development. Detailed imformation, including driller's lithologs and pumping test data is included in the Appendix. As a background to the investigation, information relating to the local hydrogeological conditions and existing wells is provided in Section 2 of the report.

5 2.1 Geology The Laird subdivision is located approximately 3 km east of Armstrong, B.C., near the base of the upland area draining Silver Star Provincial Park. The development has been built up along an alluvial fan complex, which was deposited during the downcutting of Fortune Creek and the much smaller Alderson Creek. With respect to topography, the property dips in a northwesterly direction, conforming to the gradient of the alluvial fan as it joins the Armstrong lowland area. Based on available geological data, the subsurface deposits occurring in the local vicinity are comprised of a thin veneer of coarse cobbly gravel mixed with silt and clay. This in turn is underlain by lacustrine (glacial lake) silts and clays. The granular material occurring near surface on the Laird property is likely fan gravel, deposited as Fortune Creek began downcutting. Available driller's logs indicate that the fan gravel in the local area is very thin and nonexistent at some locations. The underlying silts and clays are lake beds, deposited in extensive lakes formed by ponding during the retreat of the last glacial advance in the North Okanagan region. Existing drill log data, including the logs of testholes drilled for the Laird Improvement District, show that the lacustrine silts and clays extend fairly deep. _There is no accurate data indicating the total thickness of these deposits or the nature of the underlying material at this location. It is estimated that the depth to bedrock ranges between 250 and 700 feet (76 and 213 metres) at the Laird property. (3)

6 Existing Wells The existing well which has supplied the subdivision over the past fifteen years obtains water from two waterbearing gravel zones, which are separated by a clay bed. A log of the well is as follows: Depth Interval 0 7 ft ft ft ft ft. Lithologic Description Boulders and gravel Waterbearing gravel Clay Gravel, waterbearing Clay The well is constructed with #80 slot (80 thousandths of an inch slot opennings) well screen, set from 7 to 12 feet, a 6foot blank section and #80 slot screen set from 18 to 23 feet. During a pumping test carried out by Pacific Water Wells in 1971, the water level stabilized with 9.67 feet of drawdown, after pumping the well for 600 minutes at 90 gpm. Since the time of the original test, the level of the water table has dropped, which has reduced the available drawdown in the well and thereby well production. Available driller's reports obtained from the B.C. Ministry of Environment, incicate that, other than the existing well supplying the Laird subdivision, there are no other medium to high capacity wells in the imnediate vicinity. There are a few shallow drilled and dug wells nearby, which produce low yields suitable for individual domestic use only. A number of deeper testholes (200 to 400 feet) have been attempted, but they did not penetrate the lacustrine silts and clays and were reported as dry holes. One well located approximately 3.5 kmnorth and east of the Laird property is completed to a depth of 1570 feet and reportedly produces 70 gprn.

7 The majority of high capacity wells are located within the Armstrong lowland area which parallels Highway 97A. These wells are constructed to depths ranging anywhere from 50 to 350 feet and are generally completed in fine to medium grained sand deposits. At some locations, the aquifer material consists of coarse sand and gravel. Up until the present investigation, there was little or no data available for the vicinity around the apex of the fan associated with Fortune Creek. Results of the present study have altered this somewhat.

8 . Prior to the start of the exploratory test drilling program, a field reconnaissance was made in the general area of the Laird subdivision. At this time, a number of sites were selected where it was felt the hydrogeological conditions would be f avourable for the development of a shallow well. On May 31, 1988, McHarg Drilling Ltd. of Salmon Ann arrived on site and the drilling program was initiated. All of the drilling under the present program was conducted with an air rotary drill equipped with a casing harmer. As the drilling progressed, sixinch casing was driven into place and the nature of the subsurface material was determined by examining the cuttings returned to surface with the drilling rig's air compresser. Preliminary estimates of potential well yields from individual aquifers was determined in a similar manner, by measuring the quantity of water lifted to surface with air. In two instances, the casing was set to a specific depth and the remainder of the borehole was drilled open hole, returning the cuttings by circulating water. The first site selected is located approximately 400 feet east of the existing well on the Cotie property (see Figure 1). This testhole was drilled to a total depth of 200 feet without encountering favourable conditions for thecompletion of a well. The first 60 feet was drilled with 6inch casing and the remainder was drilled open hole. Upon completion, an air lift test was conducted, blowing the open interval 60 to 200 feet with compressed air and noting the quantity of water lifted to surface. Following the completion of T.H. #1, the rig was moved north to the Proty property and an 80foot testhole completpd. At this site the hole was drilled to the full depth with 6inch casing and the conditions, as for T.H. #1, were unfavourable for groundwater development. The rig was then moved to site No. 3, which is located on

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10 Bill Laird's property, south of T.H. #l. This testhole was drilled to a total depth of 120 feet, taking the 6inch casing to 57 feet. Upon completion, an air lift test was conducted, lifting a small quantity of water (approximately 15 gpm) from fine sand stringers encountered in the depth interval 57 to 120 feet. At this stage in the program, a meeting was held with project management and the various groundwater development options discussed. It was generally agreed that two options were available as follows: 1) Attempt a deep testhole, say up to600 feet near the existing pump house facility to explore for a deeper aquifer. 2) Try a totally different location further south near Fortune Creek to determine the nature of the subsurface material in this vicinity. _ It was decided to try the second option and following clarification of some minor easement and site access matters, McHarg Drilling set up on Site No. 4 on June 2, At this location, the subsurface conditions were considerably different than at previous sites. The silts and clays encountered at other locations were not evident in T.H. #4, but rather the material was granular. Initially the deposits consisted of cemented sand and gravel, but this changed at 114 feet and a waterbearing sand and gravel formation was encountered. The waterbearing material continued to a depth of 126 feet and because of the large quantity of water lifted to surface while drilling, a test/production well was completed in this aquifer. The final phase of the program involved a 24hour pumping test with the new well. To start the test, the pumping rate was set at 100 USgpn. As the test continued, the pumping rate was progressively increased until at the 120 minute time interval, the discharge rate was set and maintained at 360 USgpn. During the pumping test, water level drawdown was measured in the well with an electric well sounder and the discharge rate was monitored with an orifice meter. Water pumped from the well was discharged to waste into Fortune Creek.

11 4 RESULTS OF P R m 4.1 Geological Conditions During the initial stages of the program, the exploratory test drilling was carried out with the expectation of encountering a shallow waterbearing gravel formation which would augment the existing supply. If an aquifer of this nature was located near the existing pump house facility, then a supplementary source of water supply could be added to the system at a reasonable cost. As the drilling progressed however, it became evident that the fan gravels occurring downslope from the main housing development are extremely shallow and at some locations, nonexistent. It is because of this factor combined with the lowered water table that production from the existing well has decreased in recent years. Results of T.H. #3 indicate that conditions improve somewhat further upslope on the fan complex. At this location, the upper gravels were thicker, extenting to a total depth of 41 feet. Also, the underlying lacustrine deposits contained more sand than in the previous testholes and the sandy material produced a small amount of water. Moving further south towards the apex of the fan (T.H. #4), the subsurface conditions were totally different and the material was mostly granular. Based on these results, it would appear that the main concentration of fan gravels have not been deposited in a northerly direction extending out from the upland, but rather more in a westerly direnction coinciding with the present day Fortune Creek. 4.2 Well Completion After encountering favourable conditions at the site of T.H. #4, drilled adjacent to Fortune Creek, a test/production well was completed. The new well is constructed with 6inch casing set to a depth of 116 feet (35.4 metres) and 8.5 feet (2.6 metres) set in the (8)

12 depth interval to 126 feet (35.8 to 38.4 metres). A 3.5foot (1.1 metres) riser pipe is attached to the top of the screen assembly. Water is obtained from a coarse sand and gravel formation, which bottomed out at 126 feet (38.4 metres) in clay. Following installation of the well screen assembly, the well was developed by lifting and jetting with compressed air. A well Completion is shown in Figure Aquifer Test Results Upon completion of the well, a 24hour pumping test was conducted to evaluate the safe, longterm capacity of the new well. Results of the test have been plotted on a semilog graph of drawdown versus time. As seen on the drawdown plot, some problems were encountered in obtaining a water level reading during the first 80 minutes of pumping. The problem was rectified however and the missed readings do not effect the overall test results or interpretation. While pumping the well at a constant rate of 360 USgpm from the 120 minute time interval to the end of the test (1440 minutes), a steady rate of drawdown in the amount of 3.0 feet (0.9 metres) per log cycle was experienced. A comparison of drawdown at varying pumping rates during the initial stages of the test is as follows: Pumping Rate Drawdown Specific Capacity usgpm After 10 mins. USgpm/ft. of drawdown ft USgp/f t ft " USgpn/f t ft USgp/f t. The specific capacity data indicates that well loss factors become more significant at the higher pumping rates and the well becomes less efficient. Based on the test results, we would recommend a maximum safe, longterm pumping rate of 350 USgpm. This is projecting 67 percent of the available drawdown utilized, after five years of continuous pumping at the recomnended rate. A pump setting of 112 feet (34.1 metres) below ground level is recomnended.

13 1.1 m. Ground level Nonpumping water level /June 6/ ft. (20.74 m) ft (34.7 m) /joint 6inch, steel welded casing ft. (35.8 m) ft (38.4 m) / I1 I1 Figure K packer 5 l/zinch steel / riser pipe /Drive shoe Johnson's 6inch, telescopic stainless steel, #60 slot well screen.steel plate FIGUIE 2

14 The present program of groundwater exploration and development has resulted in the completion of a successful well, capable of meeting the present and future water requirements projected for the Laird subdivision. Results of the test drilling also provide new information with respect to the local hydrogeological conditions. The present results would tend to indicate that the deeper, more extensive waterbearing gravels, occur towards the apex of the fan and extend in a westward direction coinciding with the present day Fortune Creek. A sunanary of pertinent data regarding the new well is as follows: 1) The new well is constructed to a total depth of 126 feet (38.4 metres) and is completed with 8.5 feet (2.6 metres) of #60 slot well screen set from to 126 feet (35.8 to 38.4 metres). 2) The waterbearing formation is comprised of coarse sand and gravel which bottomed out in clay. 3) During the 24hour aquifer test, pumping the well at 360 USgpm, a steady rate of drawdown in the amount of 3.0 feet (0.9 metres) per log cycle, was observed. 4) A maximum longterm safe pumping rate of 350 USgp is recornended for the new well, which will utilize 67 percent of the available drawdown after five years of continuous pumping. 5) It is recomnended that the puinp be set at a depth of approximately 112 feet (34.1 metres) below ground level in the new well. 6) With respect to future groundwater development, it is recomnended that test drilling be conducted further west from T.H. #4, along Fortune Creek. Wells should be spaced at a minimum distance of 1000 feet (300 metres) to minimize drawdown interference between wells.

15 . LAIRD IMPROVDfEW DIsrlRIcT NEW sixm WELL (mm CEKEK) mm TEST Date test started: June 06/88 Time test started: 12:OO PM Pretest water level: m Reference point: Top of csg. Ht. of ref.: 1.1 metres Depth of well: 38.4 metres PUMPING INTERVAL, Time (t) since pumping started in minutes Depth to water (metres) Drawdown in metres Conmen t s < < < < < < < < < 6.38 < 6.38 < 6.38 < 6.38 < 6.38 < 6.38 < 6.38 < Pump rate: 100 USgpm Tape hungup at m Water level less than m Pump rate: 150 USgpn Pump rate: 200 USgpn Pump rate: 250 USgp Tape freed Pump rate: 300 USgpm Pump rate: 360 USgpm Pump rate: 360 USgpm

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17 4 c Laird Improvement District, Pumping Test, Recovery Interval RECQYERY INTERVAL Time (t) since pumping started in minutes Depth to water (metres) Drawdown in metres Comnents ~

18 *. c Depth Interval in feet Lithologic Description T.H. No Brown sand with gravel and cobbles Coarse cobbly, bouldery sand and gravel Brown clay Grey silty clay, very soft Grey silty clay with clay layers Grey silty clay with clay stringers T.H. No Brown clay, fairly dense Grey silty clay, soft Fine silty sand, very small amount of water Grey silty clay T.H. No. 3 T.H No. 4 (Test/Production Well) 01 Sandy loam Loamy gravel Coarse cobbly, bouldery gravel with silt Coarse sand and gravel, fairly clean, dry Brown sand with minor gravel Brown clay Fine grey sand, small amount of water Clay, brownish grey Silty clay, hard and soft layers with thin zones of fine sand (blow approx, 15 gpm open hole from 57 to 120 feet) Silty coarse sand with cobbles and boulders Sand and gravel, making some water Sand and gravel, cememted with silt and clay hole stays open while drilling Gravel with some sand, starting to heave Sand and gravel, waterbearing Clay with rocks

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20 c.*, I r ULA GROUNDWATER CONSULTING LTD. No. 208, th Avenue Vernon, B.C. VI T 3E3 Telephone (604) June 26th, 1987 Civic Engineering Services Ltd. 332 Victoria Street Kamloops, B.C. V2C 2AS Attention: Mr. D.G. Karst, P. Eng. Dear Sirs: Reference: Liard Water Utility Proposed Groundwater Supply Investigtaion The following is to outline our proposed study program with an estimate of costs, to assess the groundwater supply alternatives available to the Liard Water Utility and recomnend an imediate course of action. Based on a site visit with Mr. E. Williamson and subsequent discussions with yourself and Mr. Williamson, our understanding of the study objectives are as follows: 1) The Liard Water Utility is supplied by a shallow drilled well, which during the past three years has been incapable of providing an adequate supply of water. 2) At present the Utility requires a longterm sustained yield of 60 gpn to meet their water demand especially during the summer months. 3) The Board requires the services of an engineering firm to review and assess all of the available water supply alternatives, including expansion of the existing groundwater source, and recomnend a plan of implementation. Considering the available information at this stage, it would appear that the shallow aquifer in which the existing well is completed has reached its upper limits and consequently a process of dewatering is occurring. Our proposed study would involve a review of all available information, including existing well log data, hydrogeological reports, air photos and a topographic map.we would then make recomnendations to the Board with respect to alternate sites for well completion. Finally, we would recornend a drilling program with cost estimates. It is estimated that the study program will require eight (8) hours of our time at a fee of $50.40 per hour. Our cost estimate for the preliminary study is $ If the Board feels that a pumping test is necessary to evaluate the current capacity of the existing well, an Con'd../2

21 additional 12 hours cost to $ of our time will be required, bringing the total We trust this meets contact our office if your present requirements and please feel free to there are any questions concerning the above. LcT/c t Encl: Resume Yours truly, KALA GROUND ATER CONSULTING LTD. 36?dP L.C. Topp Hydrogeologist \