In response to a request from Water Rights Branch, a short. In general, the sequence of post glacial events in the immediate. D. M.

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1 . TO Dr. J. C. Foweraker......! C&* Groundwater Div i s ion... GOVERNMENT OF BRITISH COLUMBIA M EM0 RAN DU M D. M. Callan Groundwater Division... July 6th SUBJECT GROUNDWATER INVESTIGATION HEDLEY, B. C.... OUR.iLE...Q.~.9.2.a_3... YOUR FILE... GENERAL STATEMENT In response to a request from Water Rights Branch, a short field investigation was undertaken June 28-29th, 1971, to examine surficial geology in the Hedley Area with a view to recommending possible well sites for a domestic supply for the town. It was understood that the required yield was 150 to 200 usgpm and that the source should not be further than approximately a 1500 foot radius of the centre of town. The cooperati\pn of Mr. Loomer, Hedley Improvement District representative is acknowledged for local information. SUMMARY OF SURF'ICIAL GEOLOGY AS IT RELATES TO GROUNDWATER In general, the sequence of post glacial events in the immediate area appears to be: Development of a thick sequence of coarse sands and rounded gravels as an aggraded deposit of the ancestral Similkameen River presumably when it was heavily charged by meltwaters, These deposits exist to an elevation of approximately 1740 feet or about 100 feet above the present Similkameen River level. Dissection of this aggraded gravel plain by the present Similkameen River and Hedley Creek as a new base level was established. Limited deposition has accurred contemporaneously at the mouth of Hedley Creek giving rise to fan deposits within the dissected gravel plain. Development of mudflow fans which swept out from the Valley walls incorporating angular debris in a silt ma.trix. These deposits are thick near the valley walls and thin as a veneer over the aggraded gravels imparting gentle slopes to the otherwise bench-like surfaces of the dissected gravel plain MARKS THE IOOTH ANNIVERSARY OF THE ENTRY OF BRITISH COLUMBIA INTO CANADIAN CONFEDERATION ON JULY

2 The major aquifer prospects would appear to lie in either he aggraded Similkameen gravels or in the Hedley Fan eposits, each of these is discussed below. a) Hedley Fan Deposits The town is built on these deposits and from local comments the uppermost materials are very coarse to bouldery debris evidently open and well drained. The materials might be expected to vary greatly in texture and to be vertically inhomogenous reflecting pulses of deposition during freshet periods. No information is available on depth to groundwater table. Lateral contributions by mud flows from the sides of Hedley Creek might be expected to contribute fine silts which would seriously influence the permeability of the fan deposits. The Creek is presently flowing along the eastern margin of its fan and has cut into and eroded mud flows just above the town. The silts removed in this process may have served to seal the present channel and may seriously impede groundwater recharge to the adjacent fan materials. In siting a well in the fan materials to intersect recharge from Hedley Creek drainage the following restrictive factors should be considered: Hedley Creek cuts through bedrock at about the upstream end of the uppermost tailings pond. The town discharges its sewage into the fan materials, posing a potential pollution problem in the lower part of the fan. Abnormal flooding may introduce chemicals to the regime by leaching of the existing tailings ponds. Heavy debris may be anticipated in the upper end of the fan introducing a possible difficulty in well drilling. b) Similkameen Gravels The aggraded Similkameen gravels have a reasonably well defined topographic expression and appear to be widely developed in the valley. Exposures in the gravel pits on the west side of the Hedley Creek dissection show well rounded coarse gravels and coarse sands in cycles with relatively little silt. Exposures in the cut bank on the north side of the Similkameen east of the Confluence with Hedley Creek are equally encouraging. It appears likely that these materials will underly the bench upon which the Colonial Inn is situated.

3 *?.,' :I ' Aggraded gravels which fill the Similkameen Valley twenty miles downstream at Keremeos represent an excellent groundwater aquifer sensitive to recharge by the Similkameen River. The situation at Hedley may very well be similar from all indications. WATER QUALITY The Hedley Creek water presently used by.the town is reported to be soft and of good quality.,sirnilkameen water is reported to contain more dissolved solids and consequently harder. The quality of any groundwater stored in Hedley Creek fan may not necessarily be identical to the presently used Creek water which is diverted some distance upstream. Groundwater in the Hedley Creek fan may be subject to some degree of chemical contamination by leaching from the tailings ponds, this is an unknown factor but one which should be borne in mind if a well is constructed in the fan. The quality of groundwater in the fan below the town may be suspect as a result of septic effluent draining into it. DISCUSSION OF SITE ALTERNATIVES From the geological evidence the most likely groundwater prospect in the area having adequate recharge would certainly appear to be the aggraded Similkameen gravels adjacent to the Similkameen River. This could be compromised by siting a well within a feasible distance of town in a position most likely to intercept Similkameen gravels and Similkameen River recharge. The best compromises might be under the benches in the neighbourhood of the Colonial Inn or the gravel pit on the west end of the town. In order to reduce drilling and lifting costs this might be further compromised to consider the neighbourhood of the school, which is reasonably close to the west side of the Hedley Creek dissection. This area may be advantageous in that the groundwater gradient in Similkameen gravels should be from west to east and recharge should be unaffected by the possibility of leaching from tailings ponds. It has the added advantage that the well structure would be on the same side of Hedley Creek as the town and would not be isolated if floods damage the river crossings. This site is shown as No. 2 on the attached figure. Estimated depth to water level is 70'. A second and somwhat less promising alternative would be to site a well near the upper part of the Hedley Fan above the town and below the uppermost tailings ponds in the hopes of intersecting Hedley Creek recharge adjacent to Hedley Creek.

4 Specifically, this alternative could be tested in the area as site No. 1 on the attached figure. If groundwater in sh@ eful quantities exists in the Hedley Creek fan this would seem to be the most optimum area in which to look. Estimated depth to water level is 10 to 15 feet. ESTIMATED WELL COSTS The cost of constructing a small well will vary mainly with the depth required to reach a useful aquifer. Assuming a local driller can be hired and conservatively estimating the aquifer materials, the fixed costs, regardless of depth are likely to be in the order of: Mobilization $ ' of 811 4O/OOO $60/ft. Fittings for screen Development of well 16 $20/hr Pump testing well, 24 $18/hr Total $ (permits 200 usgpm) The drilling costs over and above this should be about $14.00 per foot for an 8" hole and $16.00 per foot for a 10'' hole. A shallow well at site 1 to test the Hedley Fan materials would be no deeper than 40 feet. If no aquifer is encountered at this depth it would be advisable to move to a more optimum site to test the Similkameen gravels since their presence is not anticipated at Site 1. The probability of heavy boulders at site & demands that the hole be started at lo1! diameter. The cost of this well is therefore: 40 ft. a io!^ a $wft. fixed costs $ Tot a1 $ A deeper hole at site 2 to test the Similkameen gravels may be 120 to 150 feet deep. The elevation at site 2 is approximately 1700 feet. Similkameen river is approximately 1630 (the estimated static water level). It may be necesswy to start out with 10" hole until the rounded gravels are reached (assume 40 feet), the remainder

5 -5- of the hole could be 8'' diameter (assume 100 feet). ofach a well would therefore be: $ The cost RECOMMENDATIONS Total well cost $ In view of the costs of well drilling, Water Rights Branch may wish to consider a 40' hole at Site 1 to examine the possibilities of finding useful quantity and quality of groundwater. The estimated cost of the hole including mobilization is $ The quality of water could be tested and if results are favourable a 200 usgpm well could be constructed at a total cost of approximately $ If site 1 proved unfavourable the alternative site 2 could be drilled. A hole here would cost about $ and if favourable could be converted to a well at a total cost of about $ The sites described are positioned to make optimum use of geological factors, recharge, economics and local existing conditions; specific drill locations within those sites could be discussed with Water Rights Branch to facilitate aquisition of property. A chemical analysis of Similkameen River water adjacent to Hedley should be obtained by Water Rights Branch to estimate the probable quality of groundwater recharged by the Similkameen. D. M. Callan Groundwater Division DMC :ph

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