5.5 Emergency Repairs, Pump Well No. 4 I I•
CITYOF
�----
1
:: . °j1 1 4 1 CHANHASSEN
I 690 COULTER DRIVE • P.O. BOX 147 • CHANHASSEN, MINNESOTA 55317
1 (612) 937 -1900 • FAX (612) 937 -5739
MEMORANDUM
1 TO: Mayor and City Council
FROM: Don Ashworth, City Manager
I DATE: January 14, 1991
1 SUBJ: Emergency Repairs, Pump on Well No. 4
I In 1989 the City hired Bruce Liesch and Associates to conduct an
analysis of our overall water system. The purpose was primarily to
ensure that future extensions of the system would be properly
sized, capabilities of the current system analyzed in comparison to
I anticipated future growth and to analyze weak spots in the system,
i.e. if Line A is shut down, can adequate pressure /firefighting
capabilities be maintained through supplies from Lines B and C.
1 The Bruce Liesch report additionally identified that the Well Pumps
#3 and #4 should be replaced (see attached synopsis from original
report). The report states "we would recommend that this
I replacement be done the next time the pumps need maintenance ".
That time is now. The booster tank for Well No. 4 has developed a
leak that could lead to an undermining of the wellhouse (park
shelter building on the north side of Lake Susan). Although quotes
I are not currently available, I am anticipating such to be available
by Monday evening. Jim Bullert of Bruce Liesch Associates will be
at Monday's meeting to present the quotes and to answer questions.
I The proposed purchase falls under the state definition of
"emergency purchases" which recognizes that certain circumstances
will arise which do not permit the formal bidding process.
1 Initial indications are that the quotes will range from $27,000 to
$37,000. This range differential recognizes an approximate $10,000
cost difference between a submersible pump versus an above ground
I pump. Mr. Bullert will respond to questions regarding the benefits
of each.
I The water availability fund maintains monies for emergency repairs.
In addition, both 1989 and 1990 revenues for this fund exceeded
budgeted expense.
1
1
1
1
Mayor and City Council
January 14, 1991
Page 2
RECOMMENDATION
Passage of a resolution establishing the repairs for Well Pump No.
4 as an emergency repair and awarding the contract to the lowest
responsible bidder, as presented Monday evening, is recommended.
^-(1
,=-2,--- .,- 4, , /3, ),,,
‘ ,
,, , ,
J � ,,1� ,N, s upply an minimize the size of future water mains. Further study will •be required
'V a �
,
p i d � to locate these well I , ..,
2. Construction of a new watermain loop to Lake Minnewashta. This watermain loop I
will be constructed as the Highway 5 corridor is developed. Current capital
improvement plans propose this construction in 1992 -1995. When these watermains 1
are constructed, it is advisable to make sure that the watermains are adequate to
provide a fire flow of at least 3500 gallons per minute to the area. Costs for 1
construction of this watermain are identified in the Capital Improvement Plan and I
total $1,000,000.
3. Replace well pumps 3 and 4 with submersibles. Well pumps 3 and 4 are both 1
r
: vertical turbine pumps with booster pumps in series. The well pumps pump the I
water into the suction of the booster pumps which then pump the water into the
watermain system. This causes a problem with synchronizing the two pumps to get '
them to pump the same rate. The current systems have a tendency to shut down }
when the pressure in the watermain drops due to the booster pump.being unable to
I
get adequate water from the well pump and overloading the motor. This system
also includes automatic pump control valves which have proven to be unreliable and
I
costly to maintain. We recommend that the well and booster pump be replaced with
a new submersible well pump in each of these wells. The submersible well pump
I
will not need the booster pump or the control valve and can be controlled to soft
start to minimize water hammer. A savings in energy use in the range of 30
I percent might be achieved by the new pump, helping to pay for the cost of the :.;
replacement. '
1
We would recommend that this replacement be done the next time the pumps need / I
maintenanc and need to pulled from the well. The estimated cost of the pump
t ,.
replacement would be $45,000 for each well.
I
! /leis 1
i /
1
�� , 31
.,d (� 1,rt /
S (r - ,[f Y OB
I " � o' 0 c r5 �� "v /�.;/
1