Dike Plan Not Foolproof Flood Protection
Wednesday, May 9, 2012 @ 3:45 AM
If the City of Prince George Council trots out the thought that any flood this year could have, “ may be” been prevented had we spent the money on the new dike, it will be a very tough sell.
The dike, for those that may not have read the info, was to be constructed from about the old Cameron St bridge site to where the boat launch is downstream.
There is talk that the city would then dredge,( did I hear that awful word, “dredge”) the back channel which would take any water around the confluence of the Nechako at the Fraser river certainly in the winter, but will have little if any effect in a spring runoff. Strange isn’t it, that the suggestion to dredge the side channel to was offered up during our major winter flood, but there were no takers. You may remember we instead got a warm water release into a normally dry channel.
Now let’s apply just a tad of common sense to the issue.
If the Fraser floods, which it may do if we get the right weather conditions , how do we prevent that underground water that the new dike was supposed to stop, from coming up through the ground and into the downtown? There is a reason why we have the pumping station at the bottom of the highway 16 east bridge. Now would you not expect that water would also seep under the ground to re surface from the area to the east of the boat launch, would you also expect the water to percolate under the ground from say the area west of the Cameron street bridge to those areas that we were about to spend 11 million to supposedly fix.
Then there is the pesky problem of the flooding both from above and below ground of the area north of the Nechako, or are we simply going to say it won’t come that way if we tell it to.
When you look at what we were about to get for 11 million bucks is it any wonder that 9271 people said no? People who build in the flood plain (and that includes CN and the City’s new energy system) have to accept some responsibility; it sure as hell isn’t the fault of the rest of the taxpayers that they built there.
As for the engineering design that Councillor Dave Wilbur talks about, there wouldn’t need to be any lawyers if those engineers got it right every time.
I’m Meisner and that’s one man’s opinion.
Comments
Judgeing from all of the input of the engineers I just can’t understand why they spend their time to become engineers. A good rule of thumb would be to do the exact opposite of whatever the engineers suggest.
Right on Ben. Anyone who has an even rudimentary understanding of the geology under the area in question would realize that the sand and gravel aquifer that extends under the area and is directly connected to the river is far too deep and extends so far upstream that the planned dike and cut off wall would have little real effect in stopping the groundwater from coming up in the city side. This idea just won’t work and seems to have a hole in its logic that is so big that one could drive an amphibex through it. No where in the City’s posted project info is this apparent discrepancy explained. If they did have engineers looking at this …were they the right kind of engineers? Any geotechnical or groundwater modeling? Unless that basic flaw is addressed … this whole idea should be killed permanently. That’s one of the reasons I signed the petition.
“The dike, for those that may not have read the info, was to be constructed from about the old Cameron St bridge site to where the boat launch is downstream.”
I did read the information and I have said all along that the City did not provide a clear enough definition on what it would do to go along with the money they were going to borrow.
The project web page is still up to be viewed. http://princegeorge.ca/publicsafety/RRDP/pages/default.aspx
This is the worst description of an engineering project that I have ever laid my eyes on. There is a most definite mindset at City Hall that the citizens are an inconvenience in the process to do whatever administration and council want to do. But that is a well known story which will hopefully come out in the core services review under the heading of âpublic communication servicesâ.
Since I cannot find a simple sketch of a section through River Road, the dike and the groundwater seepage prevention structure I really have not got a clue what the purple and brown lines on the map represent.
One of the several summary reports from the engineers can be seen here:http://www.princegeorge.ca/publicsafety/eoc/2008icejam/Documents/1%20Executive%20Summary.pdf
This is the summary report from May 2009. It clearly shows the line of the dike to be from the Cameron Street Bridge to the Fraser River railway bridge River Road overpass.
The market up aerial map is at the end of the report. It also states on page X of the document: âDike designs need to include internal drainage provisions and groundwater seepage preventionâ.
The red line on the aerial map is labeled with the words âDike along River Road (with seepage prevention and drainage).
For anyone curious enough one can find the information. But one really has to be dammed curious (pun intended). ;-)
As far as any report by any “expert” goes, one can take it or leave it. We must keep the saying that “one can lead a horse to water but cannot force it to drink” in mind at such times. ;-)
With that in mind, I just want to remind everyone that an attempt was made by the engineeers in their report to enlighten people about sediment removal.
In the above linked report you will find the words: “Sediment removal from the Nechako River or the Fraser River confluence is not considered a viable flood control solution for Prince George.
“Under present conditions, it is recommended that Prince George does not further pursue sediment removal from the main channels as a flood mitigation measure.”
WalterBesmer wrote: “the planned dike and cut off wall would have little real effect in stopping the groundwater from coming up in the city side”
Did you drill test wells to see what the draw down would be in the area in question? If so, please show us the results.
Gus,
There are several test wells in the area. The main water supply for the City is just west of the Cameron street bridge. I would think that that is similar geology to the area where the dyke would start. No? I would think that it would qualify as a test well.
The volume of water coming out of that well is horrendous. Yet, no perceptible drop in the water table. It’s because of this that we can have one of the largest wells in the world… Any other location with larger draw downs would need multiple smaller wells.
“The volume of water coming out of that well is horrendous. Yet, no perceptible drop in the water table.”
I already responded to that once to show that you are in error …. yes, it is a great water source both in quantity and in quality … however, there is a draw down as the tests for the well have shown.
Go find it and read rather than repeating the same stuff over again.
BTW, test borings to determine subsoil conditions have to be taken in several locations depending on an getechnical engineer’s estimate based on a number of observations before they are taken.
In Toronto there was a narrow long apartment buildiing about 250ft or so long. The normal test holes wer drilled at the 4 courners. None in the middle. The building got to be over 10 storeys high when it started to subside in the midedle by a good foot. The centre of the building was sitting on an old aquifer.
Just a few blocks fue north sat the U of T with a small road called TaddleCreek Rd. That was the only vestige of the creek remaining … the map designation of a street name.
One has to take their clues from a variety of things. 3 or so km along the river is very unlikely to have the same strata of porous soil. Like all land forms it varies by location.
Gus, you are truly the devil’s advocate.
That’s okay, we all need someone to keep us in line. ;)
metalman.
As a kid living in “The Cache” mid 50’s, River Road never flooded, but I had a cool raft to float over to where the old school was from our house on the south side of River Rd. And yeah, the water seeped up through the ground, just like it still does, ain’t that amazing?
I think the ‘people’ were right in votng down the dike. I’m not sure what ‘dimension’ the folks at city hall are dwelling in but it doesn’t seem that its this one.
Metalman …. when one has to certify or put a stamp on a design, drawing, or recommend a procedure, etc. and one has errors and omissions insurance which costs an arm and a leg, then one tends to be very conservative with recommendations.
So, along with other people in that position, engineers are typically very conservative people and base there recommendations on tried and true methodology.
So, in the case of flood mitigation recommendation there is, of course, no certainty, just as there is no certainty in a medical treatment.
However, based on previous experience of not only the expert and his close group of co-workers, but a whole community of experts, connected these days through the internet and various other technical literature distributiion systems rather than Pony Express or the Royal Mail Coach service, there is an excellent knowledge base which such experts have access to in order to come up with a reasonably good prescription of treating the problem to improve the normal outcome of an untreated course of events.
I’ll give it to you, Gus, that a dyke would help against a strong surge in the river an we do sometimes see this with an ice-jam.
I think we can all agree though, that it’s not much use against the water table rising.
I did go hunting regarding the “draw downs” that you said I should find. The “draw downs” affect the local well water height only–not the water table. I stand by my statement that digging wells and trying to pump the water out to lower the ground water is futile. It’s an industrial area, but we don’t even have enough hydro service in the area to provide the necessary power to keep those pumps going.
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