HomeMy WebLinkAbout2002-02-21 MS&WCD Ltr to OPHWAQHINGTON SOIL AND WATER
ISERVATION DISTRICT
MINNESOTA
-Taw
r-ir illPOTOTC
Februar 21, 2002
Mr. David Beaudet, Middle St, Croix WMO
c/o Cit of Ba
294 North Third Street
Ba A/IN 55003
R-E: Proposed Si Carpet project — Cit of Oak Park Hei
Dear Ma Beaudet.-
1825 Curve Crest Blvd, Room II)i
Stillwater, MN 55082
(651 4 Fax - (651 Y43-0 6619-
2002
MR
FAXED AND MAILED
FAX 651-351-0857
F LW
Our office has received and reviewed the construction plans and specifications dated for the proposed Si
Carpet project site, located in Section 5, Town 29 North, Ran 20 West, CitY of Oak Park Heights. This
project is for the commercial/retail developmen of a currentl undeveloped propert As part of our review,, a
site visit was conducted. Since our a has no direct approval authorit over the project, our review is bein
made on behalf of the Middle St. Croix Watershed Mana Or Based upon the site conditions
observed and the proposed plans we would offer the following comments:
1) Stormwater Mana
The site is 2.24 acres of which onl that portion of 601h Street North on the propert is impervious. The
proposed project would have 1.21 acres (54%) of impervious surfaces. Currentl the northwestern 2/3 rds of the
d
site drains to the north and the southeastern 1/3' drains to the south. While the proposed pond appears to meet
the overall rate control re other concerns are have been noted. The water leavin the site currentl
drains to the pond 'at the southwest comer of Oak and Hi 36. The applicant is proposin to collect
and drain all of the site water to the south throu a storrnwater pond. The followin table summarizes the
incremental chan in runoff from the pre and post development condition.
Si Ca — Oak Park Hei Pre and Post Development ffiscbaree Summar
Condition
2 Year Storm
10 Year Storm
100 Y ear Storm
Pre Development Dischar (Cubic Ft/Sec
- 0.93
1.68
2.21
Post Devello a nent (Cubic Ft/Sec
0.65
0.71
1.57
Difference (Increase) (Cubic Ft/Sec & %)
-0.28 cfs, -30%
-0. 97 efs, - 8%
--0..64 efs, -29%
AN EQUAL OPPORTUNITY EMPLOYER
Mr. David Beaudet
February 21, 2002
Page Two
The first major concern with this site is the apparent undersizing of the permanent pool volume (dead storage)
for the pond. The permanent pool volume is that area below the outlet. Calculations provided by the applicant
show that 14,520 cubic feet is required. Yet only 8,867 cubic feet are provided. we would recommend that the
pond be sized to meet the requirements on site or an alternate plan be implemented that provides the required
permanent pool volume of 14,520 cubic feet.
The other concern is the incremental change in runoff volume that is proposed to be discharged onto
neighboring properties to the south. Based on observations at the site and the proposed plan, a few
modifications of the proposed stormwater pond could minimize the incremental increases in stormwater runoff
volume from this site. It is our recommendation that the live storage area of the pond (the area above the outlet)
be oversized to minimize discharges. The outlet control structure Gould be modified to further slow outflow by
placing a three inch PVC on the structure rather than the proposed four inch PVC. In situations of consecutive
storms, discharge rates and volumes would be reduced if the three inch PVC was also P laced at a lower
elevation on the outlet control structure.
2) Grading and Erosion Control
Although the plan specifies that geotextile silt fence be installed around the perimeter of the project area, we
would recommend that the contractor be prepared to install additional erosion control measures in the event that
concentrated flow leaves the site. These measures may include the placement of an additional row of silt fence
in low areas to minimize sediment from leaving the site. Silt fence along the project perimeter should remain in
place until the site is restored and stabilized.
I hope that these comments will assist you with the review and comment on this .project. If you have any
questions, please feel free to call me at 430-6826.
Sincepely,
Mark J. Doneux, CPESC Karen Kill
All
Water Resource Coordinator water resource Technician
cc: Kin Kampers, City of oak Park Heights
Jeff Hensel, Greystone Constniction Company, 1221 East Fourth Avenue, Suite 110, Shakopee, MNN
55379
* Certified Professional in Erosion and sediment Control