Development and population density have a strong effect on the Groundwater quality^*14

On an island the risks are significantly higher, especially, when the groundwater also serves as drinking water.

Studies have identified septic systems as significant sources of groundwater contamination including micro pollutants, like pharmaceuticals^*15. Polluted groundwater poses serious risks to human health and the environment. Various human activities and natural processes can introduce harmful substances into aquifers, compromising water quality.

Water Quality issues on Gabriola include seawater intrusion and contaminants from septic systems. Total coliform bacteria were present in up to 60% of samples. E.coli bacteria were present in a third of samples, indicating groundwater contamination with fecal matter which could contain other pathogens such as viruses^*16.

Type 1,2,3, septic systems do not filter out most pharmaceuticals and cosmetics (PPP’s) from sewage effluence. While type 3 systems, known as discharging systems, are more effective they are not designed to target synthetic chemical compounds*¹⁷. Very few pharmaceuticals are completely removed, for instance, chemotherapy and antibiotic drugs harm the beneficial bacteria in the septic system. PPP’s, polyfluoroalkyl (PFAS) substances, forever chemicals, do not break down and lead to the contamination of the groundwater.

Treated water discharged into a subsurface field in the soil and the saturated zone of the aquifer become your final lines of defence against persistent chemicals. High volumes of sewer can create a mound of treated effluence under the drain field. The pressure from this can accelerate the movement of contaminants toward the groundwater and its aquifer^*18.

If environmental protection is the goal, then a standard residential type 3 system is not enough to protect the groundwater from contamination. Densely populated areas such as small lots or multi-density housing units may well cause downstream pollution. 

The unique island environment makes the water supply very vulnerable^*19.

Endnotes:

1.     When the Forest Breathes, Suzanne Simard, Ch.4, pg77

2.      Natural ecosystems…climate change: Adapt Now: A Global Call for                            Leadership on Climate Resilience (Global Commission on                                            Adaptation, 2019)12, https: //gca

3.     Water Always Wins, Erica Gies, Ch.1, pg. 18        

4.     Freshwater Footprint Groundwater Hazard Map, Figure 69, pg. 126

5.     When the Forest Breathes, Suzanne Simard, Ch.4, pg.77

6.    Erica Gies, Intro. pg 8

7.     Seeing the Forest Among the trees, Herb Hammond, Ch.1, pg.27.

8.     Water Always Wins, Erica Gies, Into, pg. 8    

9.     Erica Gies, Ch.1, pg. 23       

10.   Erica Gies, Ch.1, pg.26

11.   Rapid groundwater decline in aquifers, globally:, Jasechko, Seybold,   Perrone, Fan, Natures portfolio

12.   B.C. Gov’t Water Sustainability Act, Section, 5B

13.   More Groundwater Notes, Nick Doe, Shale publ. #18, 2008, pg 56

14.   Islands Trust Freshwater Footprint, Hazard Map,pg.126,,Figure 59

15.   Islands Trust Freshwater Footprint, GW Solutions, pg. 124

16.   GW Solutions, pg.129

17.   US Geological Society

18.   Waste and Wastewater.com, Tertiary Treatment in Wastewater: Ensuring Water Quality and Environmental Safety, seen online July 22, 2026

19.   Online Waste and Wastewater engineer chat, July 2, 2026