Letter from Ryan Engineering 2-3-05
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LAND DEVELOPMENT SERVICES
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434 Lake Street
Excelsior, MN 55331
Tel 952-380-5000
Fax 952-380-5010
www.ryanengineering.com
February 3,2005
Mr. Matt Saam
Assistant City Engineer
City of Chanhassen
7700 Market Blvd., Box 147
Chanhassen, MN 55317
VIA MESSENGER.
Re: Hidden Creek Meadows
Single Family Subdivision
Dear Matt:
Graphic" which shows in plan arid
project as well as the area south of Highway 7 and a portion of
Per your request, we have labeled the culverts at the various creek crossings. We are also showing,
by shading, the area behind the Kirkwood Circle homes confined by the 944.5 elevation. We feel
this elevation is pertinent because it is the OHW of Lake Minnewashta and shows potential flooding
limits from the Lake Alone without any downstream effects.
You mentioned in your email that you thought shading of the 943.4 elevation which is the HWL of..\:
this wetland would be more appropriate. Eitherway, both o:Hliese'efevatlons area15ovellie-HWL~~;.>} ........,",
the wetland within our proposed subdivision which is at 942.8. . .
My understanding is that these HWL and OHW elevations were derived from the City's Stonp
Water Management plan which was put together by the City's consultant, Bonestroo. -
In your email on 1/25/05 you stated "what we want is for you to revise your drainage ca!~A~and
model for your site to show that the wetland will not rise above the box culvert elevatioftunder TH
7. " As you know, this would be impossible to show given the fact that the City's consultant has
already determined that the HWL of the wetland on our site is at 942.8, which IS ALREADY
ABOVE THIS CULVERT elevation of939.85.
We have shown, with the submitted Hydrocad modeling, that we are maintaining our flows to the
wetland at or below the pre-developed condition with our proposed development. Therefore, we
will not be' changing the HWL of this wetland within our site. It seems appropriate to then conclude
that this will not impact any "backup" of water to the south of Highway 7.
Page 2
Mr. Matt Saam
February 3, 2005
It seems what the City's concern is the proposed sizing of the pipe we are proposing under
Pipewood Lane. We are simply using the same sizing that the City and Watershed District approved
for the development to the south, Hidden Creek, used at the crossing at Pipewood Court. This is a
42" culvert.
Uyou recall, this sizing was derived by the above mentioned Storm Water Management Plan
prepared by the City's consultant. This plan showed a proposed 36" pipe sizing for this area. The
reason for the installation of the 42" crossing was that the Watershed District wanted this upsized by
6" for what they refer to as "critter crossings". This additional sizing allows small animals to go
through the structure during a high water event.
With this graphic, multiple emails, and the above description, we feel that as the Developer's
engineer, we have exhausted our efforts to display our case. To go beyond this would demand input
from the City's consultant if your department wants any further conclusion as to the proposed pipe
sizing.
If you have any further questions or comments, please contact our office.
Sincerely,
Enclosures
Cc: Mr. Dean Carlson - D & G of Chanhassen, LLC
Mr. Paul Oehme - City Engineer
Ms. Kate Aanensoil .. Community Development Director
Mr. Woody Love
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