3b. High Zone Water Tower: Approve Plans & Specs; Authorize Advertising for Bids0
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
7901 Park Place
Phone: 952.227.1300
Fax: 952.227.1310
Senior Center
Phone: 952.227.1125
Fax: 952.227.1110
MEMORANDUM
TO: Todd Gerhardt, City Manager
',-7 b.
FROM: Paul Oehme, Director of Public Works /City Engineer I
DATE: July 11, 2011
SUBJ: High Zone Water Tower Construction: Consider Approval of Plans &
Specifications; Authorize Advertising for Bids
PROPOSED MOTION
"The City Council approves plans and specifications and authorizes advertising for
bids for a new water tower located on Minnetonka School District 276 Property,
6421 Hazeltine Boulevard ".
City Council approval requires a simple majority vote of the City Council present.
BACKGROUND
In November, 2008, the City completed an update to the Comprehensive Water
Plan. As part of the plan, a storage analysis was performed that recommended
additional storage be constructed in the existing high service zone. The high zone
water area has seen significant growth in recent years, which has driven the need
for additional storage capacity.
On May 19, 2011, staff discussed water storage needs in the high zone with the
Minnetonka School District and presented a proposal to the Board to construct a new
water storage tower in the southwest corner of the Minnetonka Middle School West
campus.
On May 23, 2011, staff presented a water storage needs analysis in the high zone to
the City Council at the worksession.
On June 8, 2011, staff held a neighborhood meeting to discuss the proposed water
tower at the southwest corner of the Minnetonka Middle School West campus.
DISCUSSION
Web Site The city has two main pressure zones. The low zone area services about 88% of
www.ci.chanhassen.mn.us the current city demand. Two water towers service this area along with the east
water treatment plant. The high zone area is serviced by two wells and a 200,000
gallon water tower located next to Minnetonka West Middle School. The tower
was constructed in 1971. The low and the high zone areas are not directly
Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow
Todd Gerhardt
High Zone Water Tower Construction
July 12, 2011
Page 2
hydraulically connected to each other. Water from the low zone cannot be pumped to the high
zone at this time. The population of Chanhassen in 1970 was 4,875. Today the population of
Chanhassen is 22,952. The high zone is mainly in a residential service area which has seen
significant growth in the past 15 years. Currently, the demand in the high zone area can be as
little as 100,000 gallons a day during the winter months and as much as 1,800,000 gallons during
peak summer time usage (2007).
Since the high zone does not have much storage capacity and water from the low zone cannot be
pumped to the high zone, during high demand periods the high zone tank cycles continuously
which causes many problems. The high cycling causes condensation to form on the tank which
accelerates tank corrosion. The condensation that forms on the tank also generates complaints
from adjacent properties because the condensation can fall off the tank and land on their
property. The continuous cycling also puts additional stress on pumps and motors needed to
supply the tower and is a very inefficient way to supply water. Also, the undersized storage
facility leaves little time for utility staff to respond to power outages and start auxiliary power
generation. In addition, the tank at this time is undersized for fire flow design.
Needs Analysis
One of the most critical roles that a water distribution system provides, especially in urban areas,
is fire protection. The Insurance Services Office (ISO) provides a score for municipalities based
on their ability to meet industry standards for required fire flow based on building size,
occupancy class, construction type, etc. Lower scores indicate better ability of systems to
suppress fires and typically result in lower insurance rates for commercial and industrial
property. The standard required available fire flow that ISO has is 3,500 gpm for 3 hours. Since
this is mostly a residential area and all the commercial buildings are sprinkled, the fire marshal
recommends using a 2,750 gpm for two hour fire flow.
Another industry guideline for required available fire flow is the American Water Works
Association (AWWA). According to AWWA, the minimum fire flow available at any given
point in a system should not be less than 500 gpm at a residual pressure of 20 psi. This
minimum criterion represents the amount of water required to provide for two standard hose
streams on a fire in a typical residential area with spacing greater than 100 feet. The distance
between buildings and the corresponding recommended fire flow for residential areas is
summarized in Table 1.
Table 1: Recommended Residential Fire Flow Rates
Distance
Between
Buildings (ft)
Needed Fire
Flow (gpm)
More than 100
500
31 -100
750
11 -30
1000
Less than 11
1500
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Todd Gerhardt
High Zone Water Tower Construction
July 12, 2011
Page 3
These two standards are typically used as guidelines when planning and designing for available
fire flow. While the majority of the high service zone includes residential -type construction,
there are several large commercial buildings, such as the Minnetonka Middle School West
building that could require substantial available fire flow needs. In addition, past discussions
with the Fire Chief and Utility Department have indicated that on more than one occasion, the
existing available storage was nearly depleted during fire suppression operations at some of the
large residential properties located in this zone. To provide a longer period of available fire
flow, additional storage is required.
Calculations have been performed based on this recommended available fire flow and are shown
in Table 2.
Table 2: Storage Capacity Needs for the High Pressure Zone
Water storage capacity should be adequate to sustain normal system demands as well as fire
protection operations. The storage volume capacity analysis for the high pressure zone is shown
in Table 2. This table shows that the existing Melody Hill Tank is not capable of providing
2,750 gpm as recommended. In addition, the amount of storage required to provide 2 hours of
2,750 gpm of available fire flow for full build -out is shown to be approximately 723,000 gallons.
gAeng \pub1ic \_2011 projects \11 -03 -high zone tower project \071111 bkgd appry ps ad for bid.doc
Existing
Ultimate
Projected
Demand
2 Hour Fire
2,750 gpm
2 Hour Fire
2,750 gpm
A
Average Daily Water Use in gpd
411,750
484,830
B
Maximum/Average Day Ratio
3.1
3.1
C
Maximum Day Water Use in gpd
1,800,000
1,900,000
D
Maximum Day Water Use in gpm
1,250
1,319
E
Firm Pumping Supply Capacity in gpm
2,000
2000
F
ISO Design Fire Fighting Rate in gpm
2,750
2,750
G
Fire Fighting Duration in Hours
2
2
H
Design Fire Fighting Volume in gal. (F x G x
60min/hour)
330,000
330,000
I
Total Coincident Demand in gpm (D + F)
4,000
4,069
J
Required Draft from Storage in gpm (I - E)
2,000
2,069
K
Adjusted Fire Fighting Storage in gal ( G x 60 min/hr x J)
240,000
248,333
L
Equalization Storage in gal /day ( C x 25 %)
450,000
475,000
M
Total Storage Need in gal ( K + L )
690,000
723,333
N
Existing Elevated Storage in gallons
200,000
200,000
Water storage capacity should be adequate to sustain normal system demands as well as fire
protection operations. The storage volume capacity analysis for the high pressure zone is shown
in Table 2. This table shows that the existing Melody Hill Tank is not capable of providing
2,750 gpm as recommended. In addition, the amount of storage required to provide 2 hours of
2,750 gpm of available fire flow for full build -out is shown to be approximately 723,000 gallons.
gAeng \pub1ic \_2011 projects \11 -03 -high zone tower project \071111 bkgd appry ps ad for bid.doc
Todd Gerhardt
High Zone Water Tower Construction
July 12, 2011
Page 4
This volume gives the city capacity to supply a 2,750 gpm fire flow rate for two hours while
concurrently meeting projected maximum day demands on the system. The standard tank size
for this demand is 750,000 gallons.
Staff has also evaluated the possibility of using the Melody Hill tower and reducing the size of
the proposed new tower. Staff looked at building a new 500,000 tank and still using the Melody
Hill tank. The Melody Hill tank is in need of repainting at this time. The last time this tank was
repainted was in 1996. The tank shows signs of significant deterioration of the paint and most
weld joints are rusting. A long lasting recoating of the tower would require the tank to be sand
sandblasted, reprimed and painted. The cost for this work is estimated at $250,000. The cost
difference to construct a 500,000 gallon concrete column with a steel tank to a 750,000 tank is
estimated at $193,000. For a steel tank, the cost difference is estimated at $260,000. The cost to
upsize a tank is mostly in the material for the larger size. The footings and structural design is
mostly the same. The cost to take down the Melody Hill tower is minimal since most of the cost
to take it down will be offset by scrap steel payment. Also, the tower may be able to be sold to a
smaller community at no cost to the City. Based on this analysis, it is more cost effective to
build a bigger tower and remove the old tower.
Alternative Sites Analysis
Over the past 2 years, staff has evaluated many sites for future water storage. Staff evaluated six
alternative sites that were reviewed in greater detail. Four of the sites were on the Minnetonka
School Middle School West Campus. Also, staff discussed the idea of constructing a water
tower on the Minnewashta Park property, but Carver County could not allow this type of
structure on their property because of the land purchase agreement requirements established at
the time of acquisition. Staff also evaluated Herman Field Park for a tower, but the elevations of
the park are too low to cost effectively build a tower. Based on the analysis that was completed
and the Minnetonka Schools District input, the recommended site for the new tower is in the
Southwest corner on the campus. This site is the preferred site by the School District. It is also
the site that has the least impact to surrounding residential properties. However, the property
directly to the south will have the most visual impacts because of the tower. The tower would be
250' away from the nearest home. The elevation of this residential property is approximately 23'
lower than the proposed tower site and mature trees do screen some of the tower. Staff is
working to try to address some of this property owner's concerns however little additional
screening can be added to eliminate the view of the tower. Staff is anticipating receipt of a letter
from the property owner regarding tower concerns. The letter will be handed out at the Council
meeting if it is received by that time.
Design
The design of the tower is complete and ready to bid. The bid will include several alternates for the
Council to consider. Staff's preferred tank style is the composite (concrete) column with a steel
bowl. Alternates for this style tank will include a block stone finish and staining the concrete. An
all steel fluted column tank similar to the TH 41 tank will also be an alternate.
Accommodations for cellular providers will be made in the tower design. The design includes a
separate entrance into the tower for cellular providers to access their equipment without accessing
the City water tower equipment. The cellular equipment is proposed to be installed in a second level
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Todd Gerhardt
High Zone Water Tower Construction
July 12, 2011
Page 5
with accommodations for installing a third level in the future if more cellular providers want to use
the tower. By installing the cellular equipment in the tower this will eliminate the need for separate
cellular external buildings and is quieter than keeping the equipment outside.
FUNDING
The engineer's estimate for construction of the tank which includes easement acquisition is
$2,000,000.
Budgets for the proposed work have been included in the 2011 CIP.
SCHEDULE
• School Board considers approval of Tower Easement
• Bid Opening
• Award Contract
• Utility Improvements and Soils Correction/Grading
• Tank Construction
• Tank Construction Substantial Completion
• Remove Melody Hill Tower
Attachments: Pressure Zone Map
Shadow Study Exhibit
Virtual Images of Proposed water tower
Site Location Map
CIP Page
Resolution
August 4, 2011
August 12, 2011
August 22, 2011
September, 2011
June- September, 2012
June, 2013
June, 2013 (contracted out
separately)
gAeng \pub1ic \_2011 projects \11 -03 - high zone tower project \071111 bkgd appry ps ad for bid.doc
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Pressure Zones
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C3 Low Pressure Zone ( 88% )
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Shadow Study
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MARCH/SEPTEMBER 21
JUNE 21
DECEMBER 21
View of Proposed Tank from TH 41 at School Entrance
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'4 View of Proposed Tank from Lake Lucy Road an Highover Drive
Minnetonka Middle School West
Water Storage Evaluation Locations
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Capital Improvement Program 2011 thru 2015 Department Water System Improvements
City of Chanhassen, MN Contact Paul Oehme
Project# W -042
ProjectName High Zone Elevated Storage Tank .
Account #1 700 - 702511751 Account #3
Account #2 Account #4
Type Improvement
Useru! Life
Category Utilities
Priority n/a
Total Project Cost: $1,900,000
ed on current and projected system demands, the high zone should have additional storage capacity. The 2008 water comprehensive plan
)mmends a total of- 750,000 gallons for storage. Currently, the high zone only has 200,000 gallons of storage. Thelocation. of the tank has not
been determined, but a few locations were identified in the 2008 comprehensive plan. A tank siting study should be completed to identify the
t location.
Justification
Co meet current and future Witter demands for the high zone area and to meet recommended fire flow storage requirements.
Expenditures 2011 2012 2013 2014 2015 Total
Construction 1,900,00 1,900,000
Total 1,900,000 1,900,000
Funding Sources 2011 2012 2013 2014 2015 Total
Water Utility Fund 1,900,000 1 1 900,000
Total 1,900,000 1,900,000
Budget Impact/Other
135
CITY OF CHANHASSEN
CARVER AND HENNEPIN COUNTIES, MINNESOTA
DATE: July 11, 2011 RESOLUTION NO: 2011-
MOTION BY: SECONDED BY:
A RESOLUTION APPROVING PLANS AND SPECIFICATIONS
AND AUTHORIZING AD FOR BIDS FOR THE HIGH ZONE WATER TOWER
CONSTRUCTION PROJECT NO. 11-05
WHEREAS, the City Engineer has prepared plans and specifications for the High Zone
Water Tower construction and has presented such plans and specifications to the Council for
approval;
NOW, THEREFORE, BE IT RESOLVED that the Chanhassen City Council:
1. Such plans and specifications, a copy of which can be reviewed at the office of the City
Engineer, are hereby approved.
2. The city clerk shall prepare and cause to be inserted in the official city newspaper and the
Construction Bulletin, an advertisement for bids upon the making of such improvement under such
approved plans and specifications. The ad shall be published at least two times, shall specify the
work to be done, shall state that bids will be opened and that the responsibility of the bidders will
be considered by the Council at 7:00 PM on Monday, August 22, 2011, for the High Zone Water
Tower Construction Project No. 11 -05, in the Council Chambers of the City Hall. Any bidder
whose responsibility is questioned during consideration of the bid will be given an opportunity to
address the Council on the issue of responsibility. No bids will be considered unless sealed and
filed with the clerk and accompanied by a bid security payable to the clerk for 5% of the amount of
such bid.
Passed and adopted by the Chanhassen City Council this 11 day of July, 2011.
ATTEST:
Todd Gerhardt, City Manager Thomas A. Furlong, Mayor
YES NO ABSENT