FW Forrester Heights Booster Station Review Water Hammer AnalysisIPM.Note
FW: Forrester Heights Booster Station Review Water Hammer Analysis
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Steve Harrington
Mike Ollivant
Steve Harrington
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Forrester Heights Booster Station Review Water Hammer Analysis
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From: Mike Ollivant <MOllivant@parametrix.com>
To: "steveh@ci.yelm.wa.us" <steveh@ci.yelm.wa.us>
CC: Randy Raymond <RRaymond@parametrix.com>
Date: Wed, 9 Jul 2008 10:20:00 -0700
Subject: FW: Forrester Heights Booster Station Review Water Hammer Analysis
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Mike Ollivant
SMTP
MOllivant@parametrix.com
Randy Raymond
Steve Harrington
Forrester Heights Booster Station Review Water Hammer Analysis
From: Jim Gibson [mailto:jimg@ci.yelm.wa.us]
Sent: Thursday, May 01, 2008 11:54 AM
To: Randy Raymond; Mike Ollivant
Cc: Grant Beck; Tim Peterson
Subject: FW: Forrester Heights Booster Station Review Water Hammer
Analysis
Randy -
Would you please review this email that I received from KPFF. After you
review it would you please respond to me so I may facilitate a
discussion within the city staff before we respond to KPFF on these
matters. What the city really needs to know is if these items are
required or recommended items. And also be considerating that as soon
as we get through this design with Forrester Heights we will be starting
a second booster station design for Tahoma Terra. If we feel that it
will be required on the larger booster station at Tahoma Terra I need to
know that also. It will be much harder for the City to require
additional features for a second booster station if we did not require
it for the first.
Thanks for your help on this project.
Jim Gibson P.E.
City of Yelm, Development Review Engineer
PO Box 479 Yelm,WA. 98597
Ph. 360.458.8438 Fx. 360.458.3144
jimg@ci.yelm.wa.us
________________________________
From: Clint Pierpoint [mailto:clint.pierpoint@kpff.com]
Sent: Thursday, May 01, 2008 10:59 AM
To: Jim Gibson; Grant Beck
Cc: Steve Chamberlain; 'RGD'
Subject: Forrester Hieights Booster Station Review Water Hammer Analysis
Jim,
On behalf of the project proponent, I would like to request
clarification on the recommended changes to the Forrester Booster
station piping identified in the Parametrix Technical Memorandum dated
April 24, 2008.
1. The memo indicates the power outage pump shutdown water hammer
analysis was performed by stopping all three large pumps at once at
1,660 gallons per minute. The maximum system demand is 867 gpm. All
three large pumps are not intended to operate simultaneously, two will
meet fire flow demands and one is redundant and would only operate if
one of the other pumps failed. However, the analysis resulted in
acceptable pressure levels without a pressurized surge tank. The
submitted design proposes a pressure tank that will reduce pump cycling
during low-flow conditions and dampen potential surges during normal
operation. The technical memo suggests increasing the line size between
the main and the proposed pressure tank to 4-inch “will improve the
ability of the surge tank to perform these functions” and cites the
results in Appendix B. The referenced Appendix B graph reflects results
for an analysis of a Power Outage Pump Failure at 1,660 gpm. Normal
operation of the booster pump station will be at 0-117 gallons per
minute. The analysis does not support the recommendation. The
connection port on the proposed bladder tank is 2-inch, we propose
increasing the line size to this limiting condition to maximize
operational function of the tank.
2. The memo also recommends the installation of an 8-inch check
valve with normally open isolation valves on either side, connecting the
suction and discharge manifolds which would allow some minimal domestic
flow and allow fire flow to be pumped through the booster station in the
event of complete pump station failure. Although the described scenario
is implausible, the intent of the described conditions could be sufficed
by manipulating the valves already included in the piping configuration
proposed. There is a 10-inch bypass installed in the watermain between
the suction and discharge stubs to the booster station which would allow
more water to be available downstream rather than realizing the head
losses through the booster station. This is a very expensive alteration
to the proposed piping layout and there is no engineering analysis
provided in the technical memo to support the recommendation.
3. The operation of the proposed redundant booster pump would be in
a fourth call position in the event of a pump failure and a fire flow
demand. The pump would start (across-the-line) in a third position as
demand exceeded the capacity of two pumps. The VFD’s on the other two
pumps would adjust to maintain the system demand. The recommendation of
a soft starter on the redundant booster pump is not supported in this
report.
4. It is recommended in the memo that the City consider requesting
a spare 132-gallon pressure surge tank. As demonstrated previously in
the memo, the power shutdown analysis resulted in acceptable pressure
levels without a pressurized surge tank. The booster pumps have
variable frequency drives and can operate without pressure tanks for a
limited period of time for tank maintenance or replacement. Pressure
tanks of this size have a life expectancy of eight to twelve years.
Degradation of an unused tank stored for that length of time would
likely result in an unusable product when needed. In addition, an
adequate interim pressure tank is available off-the-shelf at most any
plumbing supply and hardware stores.
Thank you for consideration in this matter. Please provide direction on
these items at you earliest opportunity so we are able to amend our
plans accordingly keep this project moving.
If you have any questions, please don’t hesitate to contact me.
Cordially,
Clinton D. Pierpoint | Associate
KPFF Consulting Engineers
4200 Sixth Avenue, Suite 309
Lacey, Washington 98503
O: (360) 292-7230 M: (360) 790-6832
F: (360) 292-7231
clint.pierpoint@kpff.com <mailto:clint.pierpoint@kpff.com>
www.kpff.com <http://www.kpff.com>
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FW%3A Forrester Heights Booster Station Review Water Hammer Analysis.EML
Steve Harrington
Steve Harrington
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/O=CITYOFYELM/OU=FIRST ADMINISTRATIVE GROUP/CN=RECIPIENTS/CN=STEVEH
steveh
steveh@ci.yelm.wa.us
SMTP
steveh@ci.yelm.wa.us
Randy Raymond
SMTP
RRaymond@parametrix.com
Randy Raymond
Randy Raymond