HomeMy WebLinkAbout2001-05-14 BCWD Ltr to Landform EngineeringBROWN'S CREEK
lo t WATERS ED DISTRICm
1825 Curve Crest Boulevard, Stillwater, MN 55082 Tel: 651-430-6826
Ma 14, 2001
Ms. Jancle Tave Project Representative
Landfon-n En
650 Butler North Buildin
510 First Avenue North
Minneapolis,, MN 55043
RE: Proposed Wal pro — Cit of Oak Park Hei
Dear Janelle:
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Fax: 651-43
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 y ou. In Januar of 2001, the Minnesota Board of
Water and Soil Resources approved an Order for the enlar of the BCWD that expands the watershed
district's boundar to include the land for the proposed Wal site. However, the BCWD Board of
Mana has dela permittin in this new area. Permittin has been dela until issues uni to the
enlar area have been resolved with local communities, the precise boundar has been delineated and
a upon and pendin resolution of le action b the Middle St. Croix Watershed Mana
Or in opposition to the enlar Order.
Therefore, while these comments provide a g reater level of compliance with the BCW` Rules, the are
advisor and ma be incorporated into approvals b the Cit of Oak Park Hei 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 applicant -provide water q ualit y / q uani ty _-pondinv.. on -site ., or document W h y .on-site
ponding is infeasible. If on -site ,._p not feasible, then the q pplicant should implement stormwater best
mana practices such as grass swales!,-.. infiltration trenches and in-line structural stormwater treatment
( trade names such as "Stormceptor", "V2B I'D.- -Based on m observation of the site and the proposed plan,
g rass swales, infiltration trenches and in-line structural stormwater treatment s would ver likel address
the incremental increases in ston-nwater runoff from this site. The followin table summarizes the incremetnal
chan in runoff from the pre and post development condition.
A/lana
Crai Leiser, President Karen Kilbercy, Vice-President Don Peterson, CAC Liaison E. J. Gordon., Treasurer * Jerry Turri Secretary
N/Is. Jancle'-Fave
C7
Ma 14, '200 1
Pa Two
Wal — Oak Park Hei Pre and Post Development Dischar Summar
Condition
I Year Storm
2.3" Rain124 hrs
10 Year Storm
4.2" Rain124 hrs
100 Year Storm
5.9" Rain124 hrs
Pre Development Dischar (Cubic Ft/Sec
0.82
2.30
3.80
Post Development ( Cubic Ft/Sec)
11 1.50
3.30
4.90
Difference (Increase (Cubic Ft/Sec & %)
0.68 cfs, 83%
1.00 cfs, 43%
1.10 cfs, 29%
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
temporar protection, it 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 eotextile silt fence in place 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 pr to,.place an additional row of silt fence in low areas to
minimize sediment from leavin 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 slopes steeper 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
V
Mark J. Doneux, CPESC*
Administrator
cc: David Beaudet, Middle St. Croix Watershed Mana Or
Tom Malena, Cit of Oak Park Hei
* Certified Professional in Erosion and Sediment Control
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