A WaterTreatmentPlant Prj 04-08
CITY OF
CHANHASSEN
7700 Market Boulevard
PO Box 147
Chanhassen. MN 55317
Administration
Phone 952.227.1100
Fax 952.227.1110
Building Inspections
Phone 952.227.1180
Fax 952.227.1190
Engineering
Phone 952.227.1160
Fax 952.227.1170
Finance
Phone 952.227.1140
Fax 952.227.1110
Park & Recreation
Phone 952.227.1120
Fax 952.227.1110
Recreation Center
2310 Coulter Boulevard
Phone 952.227.1400
Fax 952.227.1404
Planning &
Natural Resources
Phone 952.227.1130
Fax 952.227.1110
Public Works
1591 Park Road
Phone 952.227.1300
Fax 952.227.1310
Senior Center
Phone 952.227.1125
Fax 952.227.1110
Web Site
www.ci.chanhassen.mn.us
ICAHNED
A
MEMORANDUM
TO:
Todd Gerhardt, City Manager
FROM:
Paul Oehme, City Engineer/Dir. of Public Warks
r--7 tJ '
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DATE:
February 22, 2005
SUBJ:
Water Treatment Plant Update - Project No. 04-08
BACKGROUND
The City of Chanhassen provides municipal water to its residents from eight
wells. The raw water exceeds the recommended levels for both iron and
manganese and the arsenic levels are approaching the Maximum Contaminant
Level (MCL) of 10 parts per billion (ppb) in Well Nos. 5 and 6. Limited
sequestering treatment is provided with the addition of chlorine at the well
houses. Fluoride is also added at the well houses as required by the State of
Minnesota to prevent tooth decay, The average iron and manganese levels in
Well Nos, 2, 5 and 6 are 0.8 parts per million (ppm) and 0,3 ppm, respectively.
This is about 3 times the iron standard (0.3 ppm) and about 7 times the manganese
standard (0.05 ppm), These levels are too high for effective sequestering
treatment. Well Nos. 5 and 6 also have arsenic present at levels approaching the
MCL. Absorption of arsenic into the iron floc and subsequent filtration is
expected to reduce the arsenic levels by about 80% in the water treatment plant's
(WTP) finished water. Thus, the City desires to provide improved water quality
through the construction of a new WTP. It is anticipated that a minimum of three
to four new wells will be needed in the future to provide additional supply
capacity that will be treated at the new WTP.
In preparation for the present WTP design, the following studies have been
performed:
1. Pilot Report for the Removal of Iron, Manganese and Arsenic, May 17,
2004. The pilot plant study confirmed the effectiveness of the proposed
treatment.
2. Distribution System Capacity Study, May 20, 2004. This computer model
study confirmed the existing distribution system is adequate to handle the
output from a new 6,000 gallon per minute (gpm) WTP located at the
Ready-Mix Site,
3. Lotus Lake Well Siting Study, May 20,2004. This study confirmed the
glacial drift and Prairie du Chien-Jordan aquifers could each provide one
new 1,000 gpm (max. rate) well at both the WTP Ready-Mix Site and the
South Lotus Lake Park Site.
The City 01 Chanhassen' A growing wmmœflyu~ä\~øl~.~Iu¡¡jQ~~~, thriving businesses, winding trails, and beautiful parks. A great place to live, work, and play.
4. Preliminary Investigation Report, Lotus Lake Water Treatment Plant,
May 24, 2004, This report and subsequent review with the Minnesota
Department of Health confirmed the Ready Mix Site A to be the most
suitable for a new WTP,
S.E.H, Inc, received City Council approval to provide engineering services for a
new WTP on October 25, 2004,
An initial kick-off meeting was held on November 4, 2004 followed by a
complete design team kick-off meeting on December 9, 2004.
At the January 10, 2005 work session, staff met with Council and reviewed the
30% design of the plant and site layout.
DISCUSSION
The site is located between Highway 5 and the Twin Cities and Western Railroad
and just west of the intersection of Highway 5 (Arboretum Boulevard) and
Chanhassen Road, The WTP will have the following features:
· Water Treatment
L In-line pressure aeration,
2. Chlorine and potassium permanganate addition,
3. Gravity filtration using green sand and anthracite media.
4. Fluoride addition for prevention of tooth decay (state requirement),
5. Orthophosphate addition as a corrosion inhibitor.
· The WTP below-grade components and the filter cells will be constructed
with cast-in-place reinforced concrete.
· A finished water clearwell pumping chamber will be provided below the
WTP operating floor.
· The WTP above-grade components will be constructed with brick and
block.
· The WTP roof will be a blend of sloped standing seam metal roofs and flat
roofs with parapet perimeter walls,
· A buried Filter Backwash Tank will be constructed adjacent to the WTP,
It will also be constructed of poured-in-place concrete and provide for the
recycling of 90% of the water used in the filter backwash process.
· The WTP will include a control room, laboratory, meeting room, break
room and a unisex toilet, in addition to the basic treatment and pumping
facilities.
G:\ENGIPUBLlC\04-08 WTPIbkgd 022805 work session 60% review.doc
· A standby power generator will be provided to enable the WTP to operate
when the local electric power grid is inoperati ve.
· The WTP operation will be tied into the City's SCADA system and be
designed for automatic, un-manned operation,
· An emergency overflow system to prevent any damage due to equipment
malfunction or operator error. The local stormwater system must
accommodate this flow.
· A security system will include consideration of potential future homeland
defense security requirements. Staff has meet with security personal who
have worked on other security systems for other treatment plants. In
general, the security system staff is proposing will include:
1. Card readers that will provide entry into the plant by staff.
Backup entry will be provided by key locks.
2. Motion detectors with cameras will be placed in the pump rooms
and filter area.
3. Cameras will be placed along the perimeter of the building,
4, The site will be lighted all night.
5, Signs will be placed along the perimeter of the build notifying the
public that the building has a security system.
6. The Carver County Sheriffs office will be notified automatically
if an alarm is triggered.
Staff will have a security personal expert at the worksession to discuss this
Issue.
The consultant is working hard on the plans and will be provided the latest
drawing at the work session. The following items are submitted for the
preliminary design review or will be available at the work session for review:
1. Site Plan.
2. Floor Plan.
3. Typical WTP Cross Section.
4. Architectural Elevation.
G:\ENGIPUBLlC\04-08 WfPlbkgd 022805 work session 60% review.doc
SCHEDULE
The tentative schedule is as follows:
90% Design Review
Approve Plans & Specifications
Open Bids
Start Construction
Start Up of Treatment Plant
Alternate Start Up of Treatment Plant
Attachments
c: Jim Norton, SEH, Inc.
G:\ENGIPUBLl004-08 WfPlbkgd 022805 work session 60% review.doc
April 11, 2005
May 9,2005
June,2005
July, 2005
August, 2006
December, 2006
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East Elevation
Chanhassen Water Treatment Plant
Exterior
EB
Floor Plan