HomeMy WebLinkAbout2001-05-10 MN S&WCD Ltr Re WalgreensMINNESOTA
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WA NGTON SOIL AND WATER
G% NSERVATION DISTRICT
SOIL AND WATER CONSERVATION DISTRICTS
Ma 10, 2001
Mr. Ken Hartun Cit Administrator
Cit of Ba
294 North Third Street
Ba MN 55003
RE: Proposed Wal project — Cit of Oak Park Hei
Dear Ken:
1825 Curve Crest Blvd., Room 101
Stillwater, MN 55082
(651 430-6820 Fax: (651) 430-6819
I 2001 � I 1
I� I� MAYS ---�J
FAXED AND MAILED
FAX # 439-7188
Our office has received and reviewed the construction plans and specifications dated April 20, 2001, for the
proposed Wal project site, located at the existin Bradshaw Funeral Home in Section 34, Town 30 North,
Ran 20 West, Cit of Oak Park Hei This project is the redevelopment of an existin propert As part of
our review we visited the site and discussed the plans with project representative, Janele Tave of Landform
En 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 followin comments:
1 Stormwater Mana
There appears to be an increase of 0.36 acres of impervious area for the proposed site. The site is 1.45 acres of
which currentl 0.85 acres (59%) is impervious. The proposed project would have 1.21 acres (83%) of
impervious surfaces. No water q uantit y or q ualit y pondin is currentl used or proposed for this site. We would
recommend that the a on-site, or pg
ppl.icant provide water q un l it y / q uanit y ponding document wh on -site ondin
is infeasible... If on-site pondin.gr is not feasibh',, then the , aip-pli cant should lement stonrwater best
management practices such as ass swales, infiltration trenches and in-line structural stormwater treatment
(trade names such as "Ston-nceptor",_"V2B.1_D. Based on m observation of the site and the proposed plan,
g rass swales I infiltration trenches and in-line structural stormwater treatment s would ver likel address
the incremental increases in stormwater runoff from this site. The followin table summarizes the incremetnal
chan in runoff from the pre and post development condition.
Walgreens — Oak Park Hei Pre and Post Development Dischar Summar
Condition
I Year Storm.
2.3" Rain124 hrs
10 Year Ston'n
4.2" Rairb')4 hrs
100 Year Storm
5.9" Rain/24 hrs
Development Dischar (Cubic Ft/Sec)
0. 8 2
2. 0
3.80
- Pre
Post Development ( Cubic Ft/Sec)
- 1.50
1 0
4.90
Difference ( Increase) ( Cubic Ft/Sec & %)
0.68 cfsl,.
1.00 cfs. 43%
1.10cfs,29%
AN EQUAL OPPORTUNITY EMPLOYER
Mr. Ken Hartun
Ma 10, 2001
Pa Two
2 Gradin and Erosion Control
Since much of the site work is located adjacent to impervious areas steep slopes and or fra soils erosion
control re will need to be closel followed to minimize soil erosion. If a straw mulch is used for
tempor must be weed and seed free, It has been our experience that straw or ha bales are not
effective in reducin sediment from leavin construction sites. Due to the slopes and sand soil conditions
prevalent on this site, we recommend substitutin heav dut ' geotexti le silt fence in p e of the straw or ha
"bale checks". We believe that the location of these practices is appropriate, just simpl replace bale checks
with silt fence and keep the other existin silt fence as shown. In. the event of concentrated flow leavin the site,
we would recommend that the contractor be prepared to place an additional row of silt fence in low areas to
minimize sediment from leaving the site. Silt fence alon the project perimeter should remain in place until the
site is restored and stabilized. The specifications should re the mechanical anchorin of straw mulch on
the contour, however, most e can not operate safel on slopes steeper that 4:1. Therefore, we
recommend that all s lopes ste that 4:1 be covered with erosion control mattin such as a wood fiber
blanket, instead of straw mulch.
I hope that these comments will assist y ou with the review and comment on this project. If y ou have an
q uestions, please feel free to call me at 430-6826.
Sincerel
-r, C, SC r. ,
Mark J. Doneux, CPE,
Water Resource Coordinator
cc David Beaudet, Middle St. Croix Watershed Mana Or
Tom Malena, Cit of Oak Park Hei
JaneleTavecrcria � En g ineerin g , LandformEncrineerincy 0 cr 650 Butler North Buildin 510 First Avenue North
C�0�
Minneapolis, MN 55043
* Certified Professional in Erosion and Sediment Control
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