2003-07-28 Otsego Creek Hydrology StudyJuly 28, 2003
Mike Robertson
Otsego City Administrator
City of Otsego
8899 Nashua Avenue NE
Otsego, MN 55330-7314
Dear Mike:
1200 25th Avenue South, P.O. Box 1717, St. Cloud, MN 56302-1717 320.229.4300 320.229,4301 FAX
architecture engineering environmental transportation
RE: Albertville, Minnesota
Otsego Creek Hydrology Study
SEH No. A-ALBEV 0314.00 14
Our office has completed a hydrologic model of the Otsego Creek watershed within the City of
Albertville. Our objective was to determine the best outlet structure for Mud Lake, which outlets to
Otsego Creek. We would like to optimize the outlet structure so that outflow rates and peak
elevations in Mud Lake work for both of our cities.
The Otsego Creek watershed model has been run for several different outflow scenarios. We would
like to present you the results of our model for two of these scenarios:
1) Pre -development: Reflecting land use conditions from about 10 years ago and the existing
outlet condition.
2) Proposed: Reflecting existing and approved land uses and the proposed outlet structure.
The attached table lists the elevation and discharge rate at the 7& Street culvert for both conditions
and at Mud Lake for the proposed condition. The proposed condition reflects the following changes
to the Mud Lake outlet culvert from what is currently there:
1. The culvert size is the same, 36 inch diameter.
2. The culvert elevation is lowered 0.5 feet (from 946.2 feet to 945.7 feet).
3. The culvert location is moved to a location about 350 feet south of 70'h Street. This is the
location of a proposed new road and it will be much easier to access the culvert at this
location for maintenance and checking than it is at its current location near the outlet of Mud
Lake.
The attached table and graphs show the results from these two scenarios. In Pre -Development
condition, the 100-year storm results in an outflow at 70'h Street of 37 cfs and a water surface
elevation behind the culvert of 946.9 feet In the proposed conditions, the 100-year storm would
result in an outflow at 70`h Street of 31.5 cfs and a water surface elevation behind the culvert of
946.8 feet. The peak discharge decreases in the proposed condition because of runoff ponding
included in a proposed development south of 70'h Street.
Short Elliott Hendrickson Inc. Your Trusted Resource Equal Opportunity Employer
Mr. Mike Robertson
July 28, 2003
Page 2
The MN-DNR Ordinary High Water Level for Mud Lake is 947.3 feet. The DNR uses this elevation
as a jurisdictional elevation only. They do not intend for it to be used as a prediction of high water
elevations during specific storm events. However, in the past year, the Mud Lake water level has
been measured as high as 948.65 feet, and it has often been higher than 948.0 feet. Albertville
would like to replace the current outlet culvert for Mud Lake with an outlet and channel structure
that is easier to maintain and that will limit the high water elevations experienced over the past year.
Please accept this letter as an introduction to this issue. We request that Otsego review our model
results and the discharge shown at 70`h Street. If this information meets with your approval, we
would immediately begin working with the DNR to implement the improvements.
Sincerely,
SU*8RT EI I0VT HENDRICKSON INC.
Peter J. Carlson, PE
Albertville City Engineer
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Enclosures
c: Ron Wagner, Otsego City Engineer (w/enclosures)
Patricia Fowler, DNR Area Hydrologist (w/enclosures)
Colleen Allen, Wright Soil and Water Conservation District (w/enclosures)
Lynda Peterson, BWSR (w/enclosures)
Todd Udvig, SEH (w/enclosures)
Shannon Smith, SEH (w/enclosures)
xAae\a1bev\0314\corcV-otsego 072403.doc
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1. Models reflect the 100-yr storm event
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