Wednesday, March 04, 2015

Colliery Dams - Spillway Capacity

Is that the real issue with the dams?

The current round of discussions in the ongoing, two year saga of the Colliery Dams Park saga is focused on the requirement for greater flow capacity of the spillway. The City engineers seem of the mind the spillways are undersized for the task but have not provided the CDPPS technical team with any information which would support this conclusion. In fact at the last city council meeting it was reported that Golder Engineering had not actually been on site to take physical measurements of the current spillway and has been relying on data from previous reports, which are not really consistent. Different engineering reports peg the capacity at anywhere from 25 - 55 cubic metres per second.

The technical team from CDPPS have requested on many occasions to be able to examine the science behind the numbers Golder used in arriving at their conclusion. That said, is the spillway capacity the real issue or is the assumption the dam would breach if they were to overtop in a 1:25,000 year rain event? It would seem the dam actually breaching is what increasing spillway capacity is trying to address, when a dam breach has not been established in an overtopping event. 

Until that issue has been established no one has determined the dam would fail. That should be established before we agree to remediate the spillway capacity. This seems to be a point of stumbling between the CDPPS and the city-directed engineering reports. 

Hopefully this issue can be addressed when city staff carry out the expressed wishes contained in Councillor Yoachim's Feb. 2 motion which staff seem to have ignored.



  1. Has the provincial authority ever informed the city what the problem is with the dam and what remedial work is required?

  2. This whole process makes no sense! We have a dam that has never came close to overflowing in 100 years.. We are now told that the spillway needs not to be increased by 10 or 20% to be safe but some where between 300 to 700% larger depending on which set of numbers they used to make us safe. Does that make sense?

  3. First it was imminent doom by earthquake - disproved, now it's imminent doom by flooding - in the process of being disproved...what next? City staff wants those dams down so there is something catastrophic to blame being cooked up as we speak. Do we trust anything they say - heck no. If they can't get it done, they will get the dams safety section to do it for them, I thought collusion but giving DSS the benefit of the doubt maybe it's just all the bull the city staff has been feeding them that is in turn being dumped on us.

  4. Is the planning for the over flow approaching the same likelihood as an asteroid strike?


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