PlaceDossier / BC places / Aquifers
BC aquifer 781 · bedrock · 1 ha · Capital
Aquifer 781: Kolb Island, East of Swartz Bay
Aquifer 781 (Kolb Island, East of Swartz Bay) is a fractured sedimentary rock aquifer of 1 ha in the Capital Regional District, mapped in 2006. The province rates its productivity low, its vulnerability to contamination from the surface high, and the demand on it moderate. 1 well on record is linked to it. It lies under North Saanich.
How the province rates it
Productivity low, vulnerability high, demand moderate.
| Rating | What it means | |
|---|---|---|
| Productivity how much water the aquifer gives up to wells, judged from well yields, the aquifer material and pumping tests | low | Water comes slowly: the guide's low band is silt, fine sand or fractured bedrock, or typical well yields under about 0.3 L/s (18 L/min). A well may still supply a house, but it isn't assured. |
| Vulnerability how easily something spilled at the ground surface could reach the water, judged from what lies above the aquifer and how deep the water is | high (class A) | Little natural protection (the guide's class A): a shallow water table or sand and gravel above it lets surface water and spills soak down quickly. |
| Demand how much the aquifer is used now, judged from the number and density of wells and what they're used for | moderate | Moderately used: about 4 to 20 domestic wells per km² where homes rely on private wells. |
| Level of development Inferred demand compared with productivity | Heavy or moderate (class I or II) | Read by us from the guide's table of demand against productivity; where it gives two classes the mapper chose with local knowledge. Heavy (I): new wells should be carefully assessed; moderate (II): given careful thought; light (III): more use is usually fine if the aquifer can supply it. |
Ratings are the province's, set when the aquifer was mapped (2006) from wells, geology and local studies. Vulnerability is about the ground, not what's built on it: a well-protected aquifer under a busy area can still be at more risk than an exposed one in the bush.
Sources: Ground Water Aquifers, Water Protection and Sustainability Branch, Province of BC and Groundwater Wells (GWELLS), Province of BC, as published on October 1, 2026 (Open Government Licence – British Columbia); ratings explained after Berardinucci and Ronneseth (2002), Guide to Using the BC Aquifer Classification Maps for the Protection and Management of Groundwater, BC Ministry of Water, Land and Air Protection. Summaries by PlaceDossier.
The wells in it
1 well on record is linked to this aquifer.
| Wells linked | 1 (0 water-supply) |
|---|---|
| Drilled | 1949 |
Depths are how deep the driller finished the well; yields are the driller's test, often an hour or less, in litres per minute. A domestic well's yield is usually judged against the household's peak use; ask a driller what's enough for yours.
Where it is
Outline simplified by us from the provincial map; not for locating a lot.
| Kind | Fractured sedimentary rock |
|---|---|
| Geological unit | Fractured sedimentary bedrock of Upper Cretaceous Nanaimo Group |
| Location, as described | Kolb Island, East of Swartz Bay |
| Area | 1 ha |
| Water use | Household wells |
| Water quality concerns | Isolated: concerns documented at a few wells |
| Mapped | 2006 |
Bedrock: water moves through cracks in the rock, so two wells close together can find very different amounts. The province's page for this aquifer lists the studies behind it and its observation wells: GWELLS aquifer 781.
Sources: Ground Water Aquifers, Water Protection and Sustainability Branch, Province of BC and Groundwater Wells (GWELLS), Province of BC, as published on October 1, 2026 (Open Government Licence – British Columbia); ratings explained after Berardinucci and Ronneseth (2002), Guide to Using the BC Aquifer Classification Maps for the Protection and Management of Groundwater, BC Ministry of Water, Land and Air Protection. Summaries by PlaceDossier.
What this record doesn't cover
The province maps aquifers where wells and studies give enough to go on, mostly in settled valleys; most of BC isn't mapped, and a lot outside every outline can still have groundwater. Outlines are drawn from geology and well logs at the scale of the study, so an edge can be well off on the ground, and one aquifer can lie under another. Wells are linked to an aquifer by provincial staff from the driller's log: not every well inside an outline is linked, and well depths and yields are as the driller reported them, often from a short test.
These are mapped ratings and drillers' records, not a test of any one lot. Before you buy a property on a well, or plan to drill, ask a qualified hydrogeologist or a registered well driller what this aquifer gives where you are, and test the water.