3 Lift Station No. 2MEMORANDUM
CITYOF
CH H SB
7700 Market Bou!evard
PO Box 147
,.,~ ~,,,.,~n. MI,! 55317
Administration
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Planning &
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Public Works
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Web Sile
,', .',
TO:
FROM:
DATE:
SUB J:
Todd Gerhardt, City Manager
:
Teresa J. Burgess, Public Works Director/City Engin.ee.k~
July 1, 2002
Public Heating, Approve Feasibility Study, and Order Project for
Lift Station No. 2 and No. 10 System Utility Improvements
Project No. 01-11
REQUESTED ACTION
Hold the Public Hearing, Approve the Feasibility Study, and Order the
Improvements to Lift Stations No. 2 and No. 10.
DISCUSSION
The City Council authorized preparation of a feasibility study for improvements
to Lift Station No. 10. Those improvements were spurred by impending
development surrounding Lift Station No. 10. The original intention xvas to
address the improvements prior to the property being developed.
As part of the feasibility study, the Consultant modeled the system downstream of
Lift Station No. 10 and found significant issues at Lift Stations No. 1 and No. 2.
Staff is recolmnending that two of the recommendations (construction of a
parallel line at Lift Station No. 2 and installation of a permanent generator at Lift
Station No. 10) be done immediately with the remaining work to be scheduled as
part of the City's Capital Improvements Plan (CIY).
Lift Station No. 2: A recent valve problem (the bolts had been "eaten away" by
the acidic soils) required the City to dig a large area that requires restoration. The
bolts have been replaced with stainless steel bolts that are better for acidic soils
than the galvanized bolts that were standard when the valve was originally
installed. Rather than perform the restoration and then dig the area again in 2-5
years, it is recommended that this work be done in 2002. The parallel line will
allow Lift Station No. 2 to function more efficiently. The parallel line will be
constructed using directional drilling which creates minimal disturbance except at
the drilling pits, one of which would be located in the already disturbed area of
Sunset Hills Beach Lot. The parallel line will drop into an already existing
gravity line.
Lift Station No. 10: The City currently has a portable generator wired to Lift
Station No. 10. That generator is to address concerns about power issues in this
area as well as the short available response time due to wet well sizing. The
original intent of the feasibility study was to address those wet well sizing issues
The City et' Chanhassen · .'-. :'~?..ino ~_or'n, munR;, ;','ith '-"-~,~n lakes, o,,alit~; ~rhoot, a charming do;','nto;','n, thrivino businesses. "'; ..... '~
........ ~ ,,,nd,nu :,ahs, and beautiful parks. A g~at place to live. work. and nUw
Todd Gerhardt
July 1, 2002
Page 2
and make appropriate recommendations. Staff is recommending that a permanent
generator installation be made with proper screening. This will accormnodate the
immediate need at the site. The remaining improvements will be scheduled in the
City's CIP for future construction.
Lift Station No. 1: Improvement needs xvere also identified by Lift Station No. 1.
These improvements will be scheduled in the City's CIP for future construction.
RECOMMENDED MOTION
Move to approve the feasibility study and authorize preparation of plans and
specifications for improvements to Lift Station No. 2 and Lift Station No. 10 as
recommended.
Attachment: 1. Summary and Recommendations Section of Feasibility Report.
C:
Bonestroo, Rosene, Anderlik and Associates
Kelley Janes, Utility Superintendent
g:',eng',public' 01 - 11 'staff report 7-8-02.doc
VII. Summary and Recommendations
The following list of recommendations summarizes a priority list of projects based on immediate
needs identified by this study.
Priority No.
1
Description
Construct the emergency generator portion of Option A at Lift Station No. 10. If
a privacy fence is desired, it could be built with the generator project or a local
independent contractor could be hired to build a fence, which blends with the
development project. Cost savings and uniformity of appearance may be
achieved throughout the development if other decorative landscaping work-is
required in the development. The cost estimate includes the privacy fence and the
generator installation. The remaining elements of the recommended Option A are
included under the 4th priority recommendation.
Estimated Cost: S68,700 (with fence)
Estimated Cost: 748,700 (without fence)
Construct Lift Station No. 2 modifications and the new independent forcemain for
Lift Station No. 2. Because of the overloading problem currently being
experienced at Lift Station No. 2, this station needs to be upgraded pr/or to
rerouting the flow from Lift Station No. 1 into the aravity system contributory to
Lift Station No. 2. This recommended project needs to be coordinated w'ith the
results of the ongoing I/I investigation pertaining to Lift Station No. 2. The
results of that investigation will b~' used to finalize the lift station and forcemain
size. At this time, it is assumed that the results of the I/I analysis will show that a
Lift Station No. 2 capacity of 450 gpm will be sufficient to handle the required
inflow. This assumptions results in a recommendation to install two new 15 HP
submersible pumps into the existin~ 6 foot diameter wet well and to furnish and
install the associated nexv control'panel. This assumption also results in a
recommended 8" diameter forcemain. This.is the maximum station capacity that
can be accommodated with the existin~ wet well. If a lar_oer capacity is needed,
then a new wet well will need to be constructed: which would cause a substantial
increase to the estimated cost for this project. At this time, it is also assumed that
the new forcemain will be installed by utilizing directional drilling as needed to
minimize reconstruction costs of the streets and other restoration work. Lastly, the
upgrade in pump size will require the electric service to the site to be upzraded to
a true 3-phase service.
Estimated Cost.. $258,000
Construct a parallel 10" forcemain adjacent to the 6" forcemain from Lift Station
No. 1 to the existing 8" forcemain on Frontier Trail. Flow from Lift Station No. 1
Lift Station No. lO System Utility I,~provements
Feasibility Report
Page 25
will pump to the gravity sewer on Frontier Trail utilizing the existing 6"
forcemain. The gravity flow from this point flows to Lift Station No. 2. Near
Lift Station No. 1, the existing 8" forcemain from Lift Station No. 10 would be
connected to the new section of 10" forcemain, and it would be disconnected
from the existing 6" forcemain. Again, it is assumed that directional drilling
could be utilized to minimize disruption to the adjacent properties. It is also
recommended that the existing pumps in Lift Station No.1 be downsized to reflect
the much lower TDH that will be seen at this lift station. This will provide the
City with an ongoing energy savings.
Estimated Cost: $131,000
Construct the remaining options listed in Option A as an equipment upgrade and
control panel replacement project. The addition of a 10 foot diameter wet well
will improve cycle times and increase the response time available to the City in
an emergency. The existing control panel should be upgraded by the addition of
level sensing equipment for the new wet well, additional surge protection,
additional telemetry points, and spare parts including starter, phase monitor,
relays, timers, overload relays, circuit breakers, and fuses. In order to improve
the aesthetics at the site, it is recommended that a new lighting pole be installed.
It is recommended that the three existing gate valves be replaced, and that the
new wet well be piped into the forcemain so that the City could drop the existing
spare into the new wet well in the event of an emer~encv.~ A mobile starter panel
that would plug into the emergency generator and into tl~e pump cable would also
be provided to facilitate running the temporary pump. Odor control, in the form
of activated carbon style forced air filters could be added to the wet well vent pipe
system if odors become a nuisance. Since the flow through this lift station is
primarily fresh domestic waste, odor control equipment may not be necessary.
£stimated Cost: $]41,300 (with odor control)
Estimated Cost: $ 9!,300 (without odor control)
Due to the high cost of Option B and C and the lack of additional benefit to the City, Options B
and C are not recommended improvements.
Lift Station No. ]0 System Ufilit~, Improvemeuts
Feasibility, Report
Page 26