Viewpoint: Island geology should be considered in Vortex application

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By HUGH GREENWOOD

Dear SSI Local Trust Committee members:

You appear to have placed insufficient weight on the advice of your staff and freshwater advisor, and have missed some important relevant data in regards to the Vortex application.

The initial advice in the first staff report of Dec. 17, 2019 recommends rejecting the application, citing numerous official community plan incompatibilities and problems with siting the project in a near-shore position with a water table susceptible to tidal influence and inadequate characterization and plans for the septic system. I believe their advice was excellent, well-researched and should have been followed. 

Another staff report recommends proceeding, with conditions. The geotechnical reports by Ryzuk and associates are thorough and focus mainly on the structural problems associated with building on a base subject to possible liquefaction, but suggest engineering remedies that would make it structurally acceptable. Hydrologic problems are not directly addressed.

Other available data that deserve consideration are the report by LaRocque, Allen and Kirste, the Geohydrology of Salt Spring Island, which is recorded in Trust files, and the geologic map by Greenwood and Mihalynuk (2009). The geohydrology study contains detailed analysis of how the groundwater table fluctuates under the influence of the tides, especially in near-shore environments with low topographic relief. The water table is shallow and vulnerable, even with normal tidal ranges and may adversely affect the proposed septic sewage field.

The geologic map is illustrated in the application, but an important feature is not addressed. One of the largest faults on Salt Spring runs along the northeast side of the Fulford valley directly beneath the bed of Fulford Creek. Such faults are known to have springs and are likely to provide major conduits for groundwater and may have a large influence on the groundwater in this area of low relief, high tides and a proposed septic system with planned direct discharge to the intertidal zone in Fulford Harbour.

I urge you to reconsider your approval of this project and to follow the advice of the first staff report, which recommends rejection. At the very least, there should be no approval without having a full professional report on the hydrology. This report should give specific attention to the possible hydrologic effects of a major fault underlying the site and the influence of the tides on the groundwater and on the proposed septic field. The hydrology study will likely require monitoring of a well over a range of tides to assess the dynamics of the tidal effect and responses to precipitation. There also should be a thorough professional report by a biologist to determine the effects of this project on the biology and ecology of the area, with special attention to the possible effect of the septic effluent on the intertidal zone that will receive the effluent. Until those reports are in hand there should be no further consideration of the project.

An alternative might be to insist on the original OCP setbacks and installation of a full tertiary sewage treatment plant with off-site removal of all effluent.

A better alternative would be direct rejection of the application.

The writer is a retired engineer living on Salt Spring.

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