> i evernment OF BRITISH COLUMBIA a TO...?&.?...A 2....KO.?'!!&... Sr. *logical Engineer... Grou,,water. Section Hydrology Division Wat.er... In~.~s.tiga.ti.On.s..Branck.... 5 u BJECT...C;.roun.dw.ater...Snve st igat ion... -,Baynes Lake FROM D. Johanson Technician....Gr 0undw.a ter...se c.tio.n-...... Se.ptamhex... 14... 1926... OUR FILE...0..3405.08... YOUR FILE... An office investigation was undertaken of existing groundwater data to determine the likelihood of obtaining sufficient oroundwater for domestic use in the area of Bayne Lake, Plan 1181, Kootenay District. (The area of interest is outlined in pink on Figure 1 attached). This investigation consisted of reviewing existing data on file and new well logs received recently for the area. The investigation was conducted in response to a request received August 23, 1976, from Donald E. Goodwin, Lands Management Branch. GEOLOGIC SETTING According to the Geological Water Supply Paper 1899-L, as ice moved down the Rocky Mountain Trench, it ground and compacted the underlying deposits into clay till. Following damming of a 400-foot deep lake, streams from the adjacent mountains deposited their load along the foot of the steep walls of the Trench. The outwash deposits range in size from sand to boulders and contain less than 20% clay. Further sorting produced deltas of coarse sand to medium gravel which interfinger lakeward with lake bottom deposits of clay, silt and sand. The lake deposits rest on till. After recession of glacial conditions Y the glacial lake drained and the Kootenay River entrenched itself 200 to 300 feet into the lake bottom deposits. Figure 2 is taken from the Geological Survey Water Supply Paper 1899-L and shows a diagrammatic geologic section across the Tobacco Plains below the International Border. i! I z:m - 29m' -... (..'.'. 7... :+. >.-... 2
- 2 - Mr. A. Kohut September 14, 1976 "The Rocky Moun-ain Trench acted as a major channel for meltwater during retreat of the Cordilleran Ice Sheet from southern British Columbia. Wasting ice in the trench and in the flanking Rock8 and Columbia Mountains contributed meltwater which flowed south past 49 N latitude (Figure 48). Deposits and landforms of the southern Rocky Mountain Trench record late glacial events. The -flat valley floor is largely ground moraine with drumlins parallel to the Trench margins. This till plain is traversed by meltwater channels, many of which are underlain by outwash. Large valley trains and kame terraces occur along the margins of the Trench (Figure 48). The recessional outwash consists mainly of sand and gravel underlying meltwater channels or forming valley trains and kame terraces. On the east side of the Trench between Elk0 and Red Canyon Creeks is a large terraced and channeled outwash plain. Individual meltwater channels trend south and southwest from this outwash surface towards the axis of the Trench." (Clague, 1973. ) GROUNDWATER POSSIBILITIES Clague briefly discusses groundwater in his report. He believes the most accessible source of groundwater is late Wisconsinan outwash gravel underlying major meltwater channels which in turn overlie till or impermeable clay and silt. Clague also mentions that the character of sediments beneath the St. Eugene Formation (Rice, 1937, defined the St. Eugene silts as silts, sands and gravels of Miocene age underlying glacial and interglacial deposits) is not known, but these sediments fill a structural basin near the Elk River 1,500 metres deep. The deeper sediments below the upper till may be permeable enough to transmit abundant groundwater. WELL LOGS The more important well logs have been plotted on an overlay sheet on Figure 1. Copies of these well logs are attached and the red number in the upper right corner refers to its number on the overlap sheet. Many of these logs had not been located prior to this review of available data. Legal descriptions were obtained at the assessment office and these logs were plotted then on the overlay sheet. Most of these wells should be located quite close to their true location.... 3
E L ',-. '.' - 3 - Mr. A. Kohut September 14, 1976 These logs support Claguels interpretation of the surficial geology of the area; that is, they penetrate outwash sands and gravels, and some also penetrate the clay or underlying till. These also support Moncur's report in that some have been drilled quite deep and supply no water, whereas shallow-producing wells have been developed quite close to the same location. WATER LEVELS Figure 1 shows the Kettle lakes and ponds in the area coloured blue. These appear to be an expression of the water table in the area. The well logs, which give a static water level, also support this as their levels appear to be reasonably close to the same level as these lakes and ponds. These water levels have been converted to approximate elevations above sea level and plotted on the overlay sheet on Figure 1. This water is likely impounded by less permeable deposits, which lie to the east (see Figure 2), and allows only slow percolation towards the Kootenay River. RECHARGE "Annual precipitation on the floor of the southern Rocky Mountain Trench is less than water losses due to evapotranspiration, but there is a continual influx of surface water and groundwater from the adjacent water-positive mountainous areas. The water table is high throughout the area. Kettle lakes fluctuate in size seasonally but rarely dry up; springs and seepage occur along the walls of the major river valleys." (Clague, 1973.) WATER QUALITY From the few analyses we have of the water obtained in these outwash sands and gravels, it can be concluded that the water, except for being quite hard, is of very good quality. WELL CONSTRUCTION It would appear from the well logs that inadequate well construction techniques have likely caused the failure of some of these wells and the problem of silt in the water in others. No mention is made on any of the well logs of well screens being installed.... 4
- 4 - Mr. A. Kohut September 14, 1976 CONCLUSION As the outwash materials are poorly sorted and lenses of water-worked sand and gravel are present within the till or clay and silt, it is very important that careful sampling be done by the driller in each water-bearing zone. A cable tool rig would be probably best suited for doing this work. REFERENCES Clague, J.J. 1973. Late Cenozoic Geology of the Southern Rocky Mountain Trench, British Columbia. Unpublished Ph.D. thesis. Department of Geological Sciences, University of British Columbia. Coffin, D.L. 1970. A Preliminary Evaluation of Bank Storage Associated with Libby Reservoir in Northwestern Montana. Geological Survey Water Supply Paper 1899-L. Foweraker, J.C. 1974. Preliminary Groundwater Assessment for the East Kootenay Val ley (Libby Reservoir). Unpublished B. C. Water Resources Service report, file 0239014-B. D. Johans on Technician Groundwater Sect ion Hydrology Division Water Investigations Branch DJ/js Attachs.
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SEDIMENTS Adsl. ALLUVIUM @!!mil ALLWIAL f A N DEPOSITS OUTWASH SILT AND SAND m OUTWASH GRAVEL I TIU cxcl BEDROCK AT OR NEAR THE SURFACE BLUFFS OF UNCONSOLIDATED. SEDIMENTS d. k SURFACE DUNED. KEIILED. r-, 1'-