Golden Valley Office
2055 North Lilac Drive
Golden Valley, MN 55422
 October 11, 2000
 

                Office Tel: 763-797-3054
       Office Fax: 763-797-3181
 
 

Mr. Kevin Bigalke
 Lower Minnesota River Watershed District Administrator

 200 4th Ave West

Shakopee MN 55379
 

 RE: State Project 2725-57 (TH 55 & TH 62 Interchange)
      SW Pond Revision
 

Dear Mr. Bigalke:

MN/DOT has proposed to revise the SW Loop Pond to address concerns of pos~ible impacts to Camp Coldwater Springs from this pond. I have designed three alternatives for this pond. All three designs are similar in that the normal water elevations or pond bottom elevations are equal to the elevation of Camp Coldwater Springs 242.05.

Alternative #1 will have the pond bottom at elevation 242.05 and the normal water elevation at 242.55.

Alternative #2 is a dry pond and will have the pond bottom at elevation 242.05.

Alternative #3 will have the pond bottom at elevation 241.6 and the normal water elevation at 242.05.

Alternative #3 is the preferred design because it provides the most storm water storage and the permanent pool will provide
water quality benefits.

The revision of this pond will also require that the downstream storm sewer be modified. The 27" storm sewer pipes from structure 5602 to 5603, from structure 5603 to 5604, and from structure 5604 to 5606 will increase to 36".
The 30" storm sewer pipes from structure 5606 to 5610, from structure 5610 to 5613 will increase to 36".
The 33" storm sewer pipes from structure 5613 to 5616, from structure 5616 to 5653 will increase to 42".
The 36" storm sewer pipes from structure 5653 to 5654 will increase to 48". The 48" storm sewer pipes from structure 5654 to 5655 will increase to 66".
These proposed new pipe sizes are based on the same slopes and invert elevations as in the original plan An equal opportunity employer
 

 I have included, for your review, the Hydrocad modeling results along with the revised SW Loop Pond contours for each of the three alternatives. The storm sewer plan and profile sheets have not been revised yet but we will submit them when completed.

If you have any questions or require additional information please call me.
 
 Sincerely
 

Brian T. Kelly
Water Resources Engineering Project Manager
MN/DOT Metro Division
 

cc: Dennis Larson, Mn/DOT
Dan Dorgan, Mn/DOT (letter only)
Steve Kordosky, Mn/DOT (letter only)
Don Peterson, Mn/DOT (letter only)
L. Eric Evenson, Minnehaha Creek WSD (letter only)
Ron Hamack, BWSR (letter only)
Dale Homuth, Mn/DNR (letter only)