Friends of the Cawthra Bush
Greater Mississauga Area
Pages of Special Interest;
Other Table of Contents;
copy, if there are errors, please e-mail me with corrections - my
comments are at the end, click on the highlited text to go to specific
comments, which will have numbers in brackets eg. 
ATTN: Urban Forest Management Advisory Committee
Mr. Donald Barber.
RE: [#10] Drainage presentation.
Dear UFMAC Members: - Nov. 6, 1995 [#10]
As a result of numerous letters to involved parties over concerns that the watermain had become a water course and is threatening the long term safety of the Canadian National Railway, the Ontario Clear Water Agency has responded (Jeff Marshall, President and C.E.O.), that there is now concern over water movement in the trench and action will be taken (Oct. 23/95). A letter I though I never would get, but it does show that a resident making every effort possible to raise legitimate concerns to the parties undertaking these works, can if they are will to stick it out and not go away, will help raise the quality of the undertaking, for all concerned.
The same letter is very short on facts or measurements, which is again understandable. I have offered to share my information with the parties but have been turned down. I don't understand how they think their water stop will work when confined to such a small area of the trench length. The water flow observed if not defined, as to how much is ground water or surface run off and what is the total volume (2 pumps run 24 hour a day just to keep the trench dry).
I still feel there is a long term threat to the West Village (the new subdivision on the north side of the C.N. tracks), from the concentrating and focusing of ground water to areas along the watermain route, the C.N tracks and where will this water end up finally? At the water treatment plant? This does sound a little off topic from decisions on the Woodlot Management Program but it does clearly show how development (which the City was warned about) near a natural area, can effect it. KMK has not, to date, written to me. From what I have seen regarding the "steady state" idea, it has not happened.
The Cawthra Bush has always been a swamp forest with a perched watertable, as clearly shown by the fact that the Cawthra house was build on a mount, this also shows that the builders felt the need to take the extra precaution in case other works undertaken in the forest to channel water clearly couldn't be trusted, given the site hydrology. It is a shame that bird & hale and Geomatics (conspicuous by its absents), were not given the City's D. Blyleven Environmental Assessment Report and told to do a full hydrology study report as well. The same is true for the watermain, they and we don't know just where this preached watertable is or if it has been cut into. But what really pains me is the City over looks the historical facts in its care to show that the most important element of this swamp forests ecology is it's hydrology and it didn't become wet as a result of the first two watermains! In fact the construction notes of the first two watermains could come in very useful to chart ground water flow.
It would be interesting to find out who and what they were referring to in the Jan. 20, 1994, news article in the Mississauga News, "Development on the edges and in the midst of the woodlot, changing drainage conditions and lack of forestry management have combined to cause some deterioration in the woodlot, one of the finest of the 40 owned by the public in Mississauga."
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I have always noted that staff were aware of the french drain effect, which could very well account for the Cawthra Bush currently running dry expect in its deepest part. How would we go about determining if any of this is true?
In the Master Plan there is a call for drainage to be installed for the formal gardens, will this add to the current hydrology problem? What sections of the forest are being drained and to what degree. Will the QEW tunnel add again to the Cawthra's problems and/or increasing the water flow in the trench (the Credit Valley Conservation has not review this undertaking either).
Can OCWA present to us similar cases in wet areas, of pipe of the same size and how effective were efforts to stop water flow in the trench? Can they predict what will happen in times of flood? This a case of an environmental concerns becoming safety concerns for those down stream and along side the trench. Will the area directly above the trench remain wet and muddy? I know it seems far afield from this committees concerns but in a worse case failure of the watermain in a time of flood and if the pipe becomes mostly empty, will the pipe start to float up?
The poured concrete dams in the trench have not been seen to work, water will take the path of less resistance and flow south, around the dams or through fractured shale (fractured by construction). Golder Associates have noted that the surface of the bedrock has more frequent variations in rock quality eg. weaker rock and open joints "resulting in higher groundwater inflows". So as the trench was open cut there are likely many fractures for water to move through and these dams are a poor substitute for the generally flat impermeability unbroken shale bedrock that existed from time immemorial at this site. It is a underground ditch, a french drain, the pipes were placed on a gravel bed in the trench. And the water flowed out of the forest side in such a high volumes that even in winter, the site had to have a stop work order issued, as the sides of the trenches were caving in. The contractor did promise the City and residents to use trench boxing and other means to lower the impact of the construction, but never did, and City didn't require them to carry out these promises.
I did try to inform the Ontario Government about the pumping of ground water into the sewers, but KMK informed them that as they were get 5 gal. pails filled at similar rates, the pumping was not going on 24 hours a day, water don't flow at night? I have observed on many nights the pumps were left running. Later when this was brought to the attention of the safety inspectors they were told, that they had to do that, to preserve the site and keep it safe. Even though water was noted as a hazard to construction no efforts have been mounted to measure just how this huge undertaking will and to what degree affect ground water or to ensure that the dams are working. Or maybe, they though they were doing us a favor by draining the area as this statement from the ESR goes on to say, the areas are low quality "The character of this marshy area is not in keeping with the adjacent residential developments, and does not serve as protection to the mature wood lot which is located more westerly." The swales dried up this year even before spring, it was not the hot weather. And adding paved and other hard surface paths also change the drainage, even more.
Please find enclosed:
Sincerely Yours Truly - Mr. Donald
RE: ONTARIO CLEAN WATER AGENCY PROJECT NO. 5-0020-53, CONTRACT #1
Thank you for your letter of September 14, 1995 outlining your concern about the C.N. tracks.
Because of the concerns about water movement along the trench, the Agency and our consultant, KMK Consultants Limited, met with C.N. and they agreed that a concrete waterstop would be installed just north of the C.N. track to stop the lateral water flow. The water flow observed in the trench during construction was the accumulation of natural groundwater flow and surface run off which had to be pumped out to facilitate construction. This water will continue to percolate down into the trench, filling the voids in the bed until a steady state situation is reached at the soil/rock interface. Any further precipitation will either percolate into soil, or run off through the local drainage system.
I understand you have also written to Mr. J. Allin about this matter and he has requested that KMK Consultants Limited write to you.
Jeff Marshall, President and C.E.O.
[ Comments by Don B. - ]
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