Letter: Water Issues regarding Potlatch Density Transfer Proposal

Tuesday, September 13 2016

I am writing as a Professional Geoscientist who lives on Gabriola. I have spent several years studying the water situation on Gabriola and how to design practical solutions that optimize local water resources. I am co-author with Nick Doe of “The Hydrogeology of Gabriola Groundwater”, 2010, available on Nick’s web site at www.nickdoe.ca/pdfs/Webp649.pdf.

There have been numerous concerns expressed by members of the public and by members of the Advisory Planning Commission about the impact that the Potlatch Density Transfer will have on Gabriola, particularly with regard to water. In my opinion the plans will have major positive impacts in the donor lands, protecting the watershed at the eastern end of Coats Marsh, and may have some minor negative effects in the portion of the receiver parcels around Mallet Creek. 

I believe that any possible negative effects of the Potlatch proposal to the Mallet Creek watershed will be quite small, and can be easily mitigated by using either rainwater harvesting or storing well water during the wet winter months for future use during the dry summer months.

Let me back up a step. I have said many times that Gabriola does not have a water supply problem, we have a water management problem. So if we can store enough water, individually, during the wet winter season to cover the dry months of summer, then there is no net negative effect on the local watershed from our activity. 

At the sub-division stage the developer will need to prove to the Ministry of Transportation & Infrastructure (MOTI) that each lot has access to sufficient water (and by that the province means well water) and has conditions suitable to install a septic system (with advanced septic systems, virtually any lot with some soil can meet this requirement). So, each lot will have a well, whether or not it will be used in the future.

Typical usage for Gabriolans is about 30 gallons per day per person for people being reasonably careful, and not considering gardening or landscape irrigation. The average household on Gabriola is just over 2 people per household. So a “typical household” needs about 1800 gallons per month for household use. Approximately 1/3 of this use is for non-potable uses (principally toilets). 

Every house that has a full rainwater collection system would not put any pressure on the local aquifer.

If each house without rainwater collection had a properly designed cistern system with a timer system (say 5000 gallons), those cisterns could be filled with well water during the wet winter months and then the well pump turned off for the 80 days or so during the driest part of the summer period, thereby avoiding drawing on the local aquifer during the most critical time.

So the question then becomes how does one implement a requirement for storage cisterns or a full rainwater collection system. That requirement can be specified in a covenant. Equally importantly, how does proper use of cistern water (wells off in summer) get monitored into the future? Education on how to use cisterns properly would work in large part. 

Let me make several other short points:

• Any local effects from residential use are unlikely to extend more than about 100 m in any direction. It would be useful to ask the developer to make sure that any new wells are drilled at least 100 m from any abutting properties in order to mitigate any possible local effects.

• The house sites on the high ground near the Community Health Clinic will probably drill their wells at the foot of the cliff, thus tapping into a different watershed than Mallett Creek, with abundant water coming from above.

• The Mallett Creek watershed is a low demand watershed. It is part of the Descanso Bay Sub-Area, one of 13 Sub-Areas discussed in the SRK Consulting report (2012) entitled: Water Budget Project RDN Phase One: (Gabriola, Decourcy and Mudge Islands), which is available on the RDN website by searching on “SRK Water”. Table 1 shows that at the moment this sub-area has the least pumping stress of any sub-area on the island, even though it includes the Village Core Area. This is principally due to the large catchment area of Mallett Creek. The addition of 17 new wells (25 proposed – 8 by clinic) to this area will still leave it as one of the lowest stress watersheds on the island.

• The protection of the watershed feeding Coats Marsh is an ecological gain whose value should not be under-estimated. Nature Trust (who co-own Coats Marsh) would be a good organization to ask to quantify this value.

In closing, I think that this density transfer proposal is very positive for Gabriola on many points, and I support it. The water concerns in the Mallett Creek area are legitimate, but they can be addressed with a covenant requiring either a full rainwater collection system or storage of winter well water for summer use.

~ Sincerely, John W. Peirce, P. Geo.