1e. Koehnen Area Street Improvement Project No. 07-01: Approve Change Order No. 1 for Directional Bore of Storm Sewer
CITY OF
CHANHASSEN
7700 Market Boulevard
PO Box 147
Chanhassen, MN 55317
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Phone: 952.227.1100
Fax: 952.227.1110
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2310 Coulter Boulevard
Phone: 952.227.1400
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1591 Park Road
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Phone: 952.227.1125
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Web Site
www.ci.chanhassen.mn.us
.1e
MEMORANDUM
Paul Oehme, Director of Public Works/City Engineer~~O .
Joseph ShamJa, Project Engineer~,_ VA A
August 13, 2007 ~
TO:
FROM:
DATE:
SUBJECT:
Koehnen/Yosemite Reconstruction, Project No. 07-01:
Approve Change Order #1 (Construction of Pond Outlet and EOF)
REQUESTED ACTION
Approve Change Order #1 provided by the project contractor S.M. Hentges &
Sons, Inc. in the amount of $49,680.80 for the KoehnetrL.ArealY osemite A venue
storm sewer pond outlet and emergency overflow.
BACKGROUND
On January 9,2006, the City purchased an easementfoLstonnsewerponding for
the Koehnen ArealY osemite Avenue street and utility reconstruction project.
On April 3, 2007, Council approved the bids and awarded the contract toS.M.
Hentges & Sons, Inc. for the Koehnen ArealYosemiteAvenue street and utility
reconstruction project.
DISCUSSION
The storm water pond along W. 63rd Street was constructed during the Koehnen
ArealY osemite A venue Reconstruction Project. This pond is located in the
easement purchased from Ann Nye in January of 2006. The pond Was designed
to outlet to the nearby wetland. The wetland has an existing storm sewer outlet in
the southwest comer of the property. During construction, the outletofthe
wetland was determined to have deficiencies. The existing stornioutletconsists
of a deteriorated manhole and storm pipe with many sags and does not have the
storm water capacity that was originally calculated.
Further investigation of the wetland outlet determined that this stOfI11S~~t~p1does
not have an adequate emergency over flow (EOF) in this area. EOF'sallowthe
stormwater an alternative route in case the primary outlet malfunctions. The
primary reason for an EOF is to help prevent flooding. All new developments in
the City are required to provide EOF's. The backyards and side yards where the
EOF should be has been filled in, a fence has been installed and landscaping
constructed.
The City of Chanhassen · A growing community with clean lakes, quality schools, a charming downtown, thriving businesses, winding trails, and beautiful parks. A great place to live, work, and play.
Paul Oehme, Dir. Of Public Works/City Engineer
Koehnen Area Reconstruction Project - Approve CO #1
August 13, 2007
Page 2
Staff looked at the most cost effective and least disruptive way to complete both
objectives. The first objective was to provide a sufficient outlet to the wetland
and pond, and the second objective was to provide a better EOF to help prevent
backyard flooding. In order to complete the first objective, staff proposes to
remove the failing sections of the existing pipe and manhole and replace as
necessary. The second objective will be completed by directionally drilling a new
18" HDPE (High Density Poly Ethylene) pipe along the easement between the
properties.
Open cutting the proposed storm sewer in this area is not recommended. There
are many significant trees, a new fence, and a pool along the easement which
could be disturbed with the open-cut method. To install the pipe by the open-cut
method would require a deep cut through Wood Duck Lane which would require
additional disruption to the neighborhood and street restoration costs. Restoration
of the trees and fence along with the disruption to these properties prevents using
the open-cut method.
The improvements are proposed to be constructed during the Koehnen Area
Project prior to completion on the storm water pond.
Replacement of the failing pipe along with the added flood protection of an EOF
is anticipated to complete both objectives. Staff recommends approving Change
Order #1 in the amount of $49,680.80 for the Koehnen Area/Yosemite Avenue
Reconstruction Project. Staff has compared the unit prices in this change order to
other project bids of similar nature and finds the unit prices acceptable.
This Change Order is proposed to be funded out of the Storm Sewer Utility Fund.
Attachment: 1. Map of area of storm sewer installation.
c: Marcus Thomas, Bolton & Menk Inc.
g:\eng\public\_2007 projects\07-01 koehnenyosemite road imp\08-13-07 co report.doc
Proposed Directional Storm Sewer Pipe
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