The Thursday night watershed
meeting was like no other I have ever been to. The MAC had their consultants
explain that they were going to use the jet grouting method to seal off
the construction sites for the tunnels, (The tunnels are to allow vehicles
to drive under the runway to access the land on the inside of the airport
property). instead of the metal grates. The main difference is that the
concrete grouting is permanent, but no more so than the tunnel itself.
This method is also considerably cheaper than the metalgrates.
The consultant explained that the grouting will allow them to patch the
wall once it is in place. This means that if the wall leaks that they
can simply add more concrete grouting to fix it. The way they will check
the wall to make sure it is holding, is that they expect no more than
900 gallons a minute pumping rate to empty the trench that will be dug
for the tunnel. Some water will leak into the construction site under
the concrete wall, but it will not be 900 gallons a minute. That figure
is only to pump the trench dry the first time. Once they pump it dry,
the concrete wall will stop almost all the water around the trench from
leaking in. Then the MAC will also monitor various wells around the construction
site to make sure that the water levels in the area do not drop. One of
the wells is at Camp Coldwater.
The Minnehaha Creek Watershed asked for assurances that the water levels
be protected, even if the concrete wall completely failed. Jeff Hamiel,
executive director and official spokesman of the MAC, said in no uncertain
terms that they intend to protect the water resources of the area. If
the wall completely failed or had extensive leaks, Hamiel said the project
will stop, and they will have to figure out another way to continue without
the drastic dewatering first proposed. Lynn Levine came up to the microphone
and asked for Hamiel to further state his position to be absolutely clear
on what the MACís position is, explaining that we have been tricked before.
Hamiel came back and said that even if the wall fails and it would completely
submerge the equipment and cause extensive damage to the construction
site, they will not drain the water to the Minnesota river to try and
keep it dry. Instead they would let it all go underwater and figure out
a way to fix the situation at that point.
The consultant said he did not think that this would happen, as when they
pump the trench dry the first time, if it requires excessive pumping they
will know that the wall is leaking and will fix it before anything else
happens. It was such a surprise to hear the MAC give such a guarantee
that they will do the right thing, people around me were noting the time
was 8:22PM in case they had to reference the statement at a latter date.
After all the problems with MnDOT, it appears that the MAC has come in
and, in the end, shown how to make a commitment to correct the situation
to protect outside water resources from their project area. We will have
to see if MnDOT can now duplicate this effort in their construction of
the Hwy 55 & 62 interchange. It appears that the drainage pond for the
road will have a bottom that is two feet lower than the Coldwater Spring.
An elementary understanding of gravity will show how this could permanently
dewater part of the Coldwater Spring (up to 25%). This is now the most
immediate danger to Coldwater.
The Minnehaha Creek Watershed
is looking into this situation to try and figure out the impact. The problem
is that wile the Coldwater area is in the Minnehaha Creek Watershed, because
of the political decision of the Board of Soil and Water Resources, the
highway interchange, that sits over part of the source water for the Coldwater
Spring is in the Lower Minnesota River Watershed District, who has no
permitting authority. The Next Lower Minnesota River Watershed meeting
is on Wednesday, September 20th at the Shakopee Community Center at 7PM...
Minnehaha Creek is trying to Work with Lower Minnesota to figure out the
risks and how to correct the situation. We have not yet heard of a response