Ground Water Resources of British Columbia
Chapter 9 — Ground Water Resources of the Basins, Lowlands and Plains
9.1.4 SUQUASH BASIN AND ISLANDS
by
J. C. Foweraker and E. Livingston
GENERAL DESCRIPTION
At the northern end of Vancouver Island there is an area of low relief and low rounded hills which was overridden by ice, called the Nahwitti Lowland (Holland, 1964). Within this lowland there is a triangular area bounded by Englewood, Quatsino and Port Hardy which is mainly below 1000 feet in elevation and called the Suquash Basin (see Chapter 8, Figure 8.3). This basin also includes Malcolm Island and Cormorant Island. The area is underlain by gently dipping Upper Cretaceous coal measures (Holland, 1964). According to Holland, erosion of the soft Cretaceous sedimentary beds has produced the low lying topography within the Suquash Basin whereas the harder and more resistant volcanic rocks of the older Vancouver Group resulted in the higher elevations of the Nahwitti Lowland.
GROUND WATER POTENTIAL
Available information on ground water potential, apart from domestic wells of limited yield, is mainly confined to wells constructed for communities at Port McNeill, Port Hardy, Sointula and Alert Bay.
PORT McNEILL
The production well at Port McNeill is a 15.2 m well, completed in sands and gravels. These sands and gravels appear to be outwash deposits overlying the glacio-marine stony silts which form the broad east-west ridge on which Port McNeill is located (Livingston, 1971). The Port McNeill well has a sustained yield of 15.8 L/s. The transmissivity is 2.01 X 10-3 m2/s.
PORT HARDY
At Port Hardy a few well records have reported yields from 36 to 68 L/min. These wells are completed in bedrock at depths between 9 and 45 m and draw ground water from fractures in the bedrock. On the east side of Beaver Harbour in the Port Hardy area, and in the vicinity of the airport, good domestic well yields are reported to have been obtained from shallow sand and gravel deposits.
MALCOLM ISLAND
Malcolm Island is located opposite the Nimpkish Valley. Both Malcolm Island and adjacent Cormorant Island have a prominent embayment on the south side known as Rough Bay and Alert Bay respectively. The presence of kettled areas, ice-contact deposits and lineations showing on air photos suggest surficial deposits associated with ice, which possibly came from the direction of the Nimpkish Valley (Foweraker, 1965). Water supply for the early Malcolm Island residents came from dug wells, and wash bored holes put down using a half inch to one inch pipe with an open pointed end and through which water was forced under pressure as the pipe was raised and lowered.
Depths over 61 m were recorded for wells drilled by this method. Production well drilling for Sointula (Foweraker, 1966; Badry, 1983) indicate a heterogeneous mixture of unconsolidated sediments probably ice contact deposits to 85 m with several aquifers in this sequence capable of supplying excellent quality water. Production well No. 3 at Sointula has a a reported yield of 12.6 L/s.
CORMORANT ISLAND
On Cormorant Island, the Village of Alert Bay obtains its water supply from a 108 m deep well located at the air strip approximately 61 m above sea level. This well drilled through a varied sequence of surficial deposits is completed with a 10 m length of screen with blank sections opposite a sand and gravel aquifer. The well yields 10.1 L/s with a static water level at 62 m below surface. The transmissivity is 1.4 X 10-2 to 2.9 X 10-2 m2 /s (Foweraker, 1975). The water is of the calcium-bicarbonate type, relatively low in dissolved mineral content with TDS near 120 mg/L and low sodium and chloride contents close to 10 mg/L. Preliminary Tritium analyses indicate the ground water is a mixture of pre-1953 and post 1953 waters indicating some of the water is less than 35 years old and recharge is active on the island.
Although the pumping water levels in the aquifer are below sea level, pumping from the main production well at an average continuous rate of approximately 11.4 L/s has not resulted in any significant changes in water quality due to proximity of the sea. This suggests that a minimum recharge rate equivalent to 15.7 cm of water over the entire island or 12 percent of the annual precipitation of 137 cm is returning to the aquifer. A shallow observation well sited in sands and gravels in the Village and near sea level yields 75.6 L/min.
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