Dear Editor:
I am increasingly concerned that the risk of damaging the water-source of the Shaughnessy Springs, and thus the Fish Hatchery, is real and may not be adequately assessed or may only be adequately assessable at considerable cost.
To my knowledge, there is no statistical risk assessment done that considers all the dependent and independent risk factors to assess the chance of water-table damage or slumping during and after construction.
The engineering reports say no water table was encountered in the shallow holes toward the west of the building site. Only in two holes groundwater was encountered, directly north and west of the Shaughnessy Springs.
This and other research shows that the location of the water table is largely unknown, but is likely up-dip from the Shaughnessy Springs under the proposed site.
I cannot find data regarding the risk of heavy duty building activity and vibration disturbing the critical water-table, the source for the Fish Hatchery.
There are two paragraphs in one report mentioning likely increased ground vibration, vibration induce turbidity and a higher risk for the Shaughnessy Springs water quality. There is no further discussion regarding these statements.
Once the water table is damaged, it is irreversible and the hatchery may be lost.
Also, I have not read about any potential risk of slumping during excavation, if the retainer for the bluffs is undermined.
Some additional concerns:
• The Piteau Hydro-Geological Assessment report predates the Glen Rock report based by 2.5 months. Was the Glen Rock draft complete enough for the Piteau report to be valid? Are any of the reports and their conclusions impacted by the design change? It went from 315 units in May to 380 in December. Could more weight mean a higher chance of disturbing the water-table?
• SPT tests were done to determine the soil stability in the test pits. Even if the soil for the building site is stable, there should be a discussion about the building activity and how it would impact the stability of the surrounding areas.
• Piteau assumes that the groundwater level generally follows “a subdued replica of surface topography” and concludes that the bottom of the parkade slap will be some 20 metres above the groundwater table. Following their assumption, simple math says that the water table could be as little as 10 to 15 metres below the bottom of the parkade. A referenced email about this is not shown on the municipal website, so their reasoning cannot be verified.
• Certain statements in the engineering reports are worrisome; they seem “safe statements.” An example from Rock Glen: “these spring areas do not directly affect building and development on this property from a slope stability perspective.” The question should be “does the building and development activity on this property affect the spring area and its source?”
Should there be a risk assessment by another independent party? It would be a benefit to all that we do not make an irreversible mistake.
Aart J. Dronkers
Structural Geologist
Summerland
