Bedrock aquifers of the Saanich-Victoria area

Based on a 2004 compilation by Sylvia Kenny for the Ministry of Water, Land Air and Parks (now Environment Ministry) http://www.env.gov.bc.ca/wat/aquifers/aquifers_crd/aquif_crd.html

Saanich-Victoria bedrock geology

Saanich Peninsula cross-section

Karmutsen Island Intrusive

Glacial and glacio-fluvial sediments

Bonanza Gp.

Major aquifers of the Saanich-Victoria area

Aquifer name Aquifer # wells % of Aquifer Geol. avg. depth avg. yield

  number   wells type unit m L/s

Lands End 607 285 8.4 BR Nanaimo Gp 46 0.19

North Central Saanich 608 1383 40.8 BR Granite (Is. I.) 46 0.25

Littlewood 609 12 0.4 UNC Quadra 8.1 1.4

Bazan Bay 610 49 1.4 UNC Quadra 6.7 1.2

Hagan 611 31 0.9 UNC Quadra 14 0.25

Keating 612 109 3.2 UNC Quadra 26 0.5

Karmutsen 614 216 6.4 BR Karmutsen 55 0.19

Cowichan Head 615 15 0.4 UNC Quadra 15 0.25

Cordova Bay 616 12 0.4 UNC Quadra 23 0.38

Wark-Colquitz 680 1051 31.0 BR Gneiss (WCC) 61 0.32

Willis Pt 681 165 4.9 BR Bonanza V. 58 0.25

Colwood Delta 682 34 1.0 UNC Glacio-fluvial 4.3 0.76

Parry Bay 683 24 0.7 UNC Quadra 17 0.32

3386

average depth and yield: BR 53 0.24

average depth and yield: UNC 14 0.63

from Kenny, 2004

Island Intrusive

“As water is transported within the aquifer through joints and fractures, the productivity of individual wells varies, depending on whether the well intercepts these structures, and upon the hydraulic connectivity of intercepted fractures with other major fault systems. … Previous studies have found the fracture network within the granodiorite can yield increasing quantities of water with depth, with the greatest yield occurring at depths between 40 and 80 metres….”62% of the wells are “confined” by either clay or till, or both.Hardness is a factor in some wells, and relatively high TDS is also an issue. It is not clear if the high TDS levels are derived from old deep water, or from sea-water.

Aquifer 608 – North Central Saanich – Granitic rocks (granodiorite) of the Island Intrusive suite (Jurassic)

41% of wells in the area.

Wark and Colquitz gneiss

“The majority of well records describe the bedrock of this aquifer as green, white and black “granite” (!). other records describe the occurrence of diorite and gabbro with feldspar and quartz venation …” Most water-bearing fractures are observed at depths of around 60 m28% of the wells are “confined” by either clay or till, or both.High iron and manganese levels have been reported. Numerous contaminated sites overly the aquifer, but no impact to water wells has been documented.

Aquifer 680 – Colwood, Langford, Esquimalt, southern Saanich and Victoria – Gneissic rocks of the West Coast Crystalline Complex (mafic Wark Gneiss and felsic Colquitz Gneiss)

31% of wells in the area