MnDOT unveils draft groundwater study
|On Wednesday June 13, 2000 MnDOT
revealed a preliminary groundwater study of the Coldwater area. The main
water flows have been shown by bedrock fractures. See
The blue lines are secondary fractures in the bedrock, and the green line is the primary fracture. Water flows from the southwest, to the northeast through the secondary fracture (blue) and when it hits the primary fracture(green) it flows southeast towards the Coldwater spring.
To get this documented is excellent because knowing how the water flows gives important information to constructing the road in a way so as not to damage the spring. MnDOT has shown a new willingness to work with the concerns of the area and people in having the meeting to discuss the issues, and produce this study.
They have agreed to monitor ground water much more closely during construction than originally planned and have redesigned sewer lines so that a minimum of excavation is expected. The depth into the rock they will dig into is expected to be about eight inches. Though it is not ideal to dig into the rock at all (because it caries significant risk), this is a far cry from the ~5 foot deep trenches they were previously digging.
No major storm sewers are going into the area. Most pipes are about three feet in diameter. The bridge that will be part of the interchange, is getting pilings to support it. This should not have as a significant effect that digging in giant footings could have. A preliminary dewatering test for the pilings and smaller footings look promising.
Though this is not an ideal situation, and their still is risk, the fact that SEH, hired by MnDOT, who is doing the groundwater analysis, is currently in the final process of developing and calibrating a computerized groundwater model, that will generally simulate the hydrogeologic conditions in the area, shows an attempt to get real data.
With real data plans can be modified to accommodate the area so as not to damage the spring. This could also be a baseline of evidence that could be useful for the airport tunnel construction. I hope that the airport can follow MnDOTís new lead and get some real data and plans for their major project. Currently the metropolitan airport commission is requesting a permit to dewater the entire region.