SS9901-CS 990930Making sure a city's infrastructure keeps pace with rapid population growth is a criti-
cal challenge, one not always easy to finance or realize. However, one community
that successfully coped with this situation is Collierville, Tennessee, the state's
fastest growing community.
In just 15 ycars, Collierville's popu-
lation has grown fl-o m 10,000 to near-
ly 30,000 today. While everyone in
this comfortable suburb, some five
miles east o1' Mcmphis, assumed
growth would steadily continue at a
somewhat predictable pace, expan-
sion plans by Federal Express sud-
denly changed everything.
In 1996 FedEx chose Collierville
as the development site for its new
Technical Services Bnilding, hous-
ing its computer and information sy~
terns. That facility, in the Bailey Road
Subdivision, will be home to 1,100
employees. Jack Tyler, who heads
Memphis-based Jack Tyler Engineer-
ing Company explains, "Needing
more room than the area it domi-
nates around the Memphis airport,
Federal Express' announcement
meant Collierville could be faced
with an additional 4,000 to 5,000 res-
idents in the near future.
"That made it clear to Robert Gib-
bons, Collierville city engineer, and
consultant Fisher & Arnold, Inc.,
that the capacity of the existing
wastewater treatment plant facilities
would soon become insnfficient.
Therefbre, he and his staffdecided
that a major expansion was required,
one that would call for a new inter-
ceptor sewer system, a new waste-
water treatment plant as well as a
large pumping station."
Pleased with the city's experience
using prefabricated nnderground
pumping stations, Collierville offi-
A 45-ft deep pit was excavated to house
the new wetwell and pre-fabricated,
self-contained pump station. I
58 · September 1999 www. pwmag.com · ~LII]~C~I31~
CITY'.C: GROWTH
cials and the city's cousuhanls opled gcncral plans for m-ca sewage treat- t]m5 tale should ahvays malch
lbr a high capacity ulldclglouud silt- lllelll capacity expansion, inflow rate to the wetwell.
tion. Operating silently, odor h'cc, Ilo also sa}s the station will hah- If the llowinto thc wc~vcll increas-
arid ouI ofsighl, lhe facility would die strictly domestic alld business esheyondthefuslpu~pscapac~t),
cause no threat or anxiely to resi- stwagc. Stwagc is delivered ~ia Ihe the second pump is ac{ivated. The
d(nts of nearby homes. Nonconnah interceptor, and travels third pmnpis activated onlywhen tile
Uhiu~atcly, a prelhbritaled, sell: by gravity through 3(5 and 4S-in. flowexceedsthecapacityoffl~eofl~er
conlaincd pump station was con- diameler piping to a newly con two pumps. As the wetwell level
s, ucted, transported, and installed, strutted 40 by 16- h} 16-fl ccmcrele decreases, all pumps will steadily
Designed and huih h} l)akota Pmnp, wetwell. Situated four ti away and decr/asc in speed until all arc pump-
Inc. (Milchell,SomhDakola),ilislht ~arallc] to thc pump slation, Ihe lng approximately at hall capacity.
largest pump station ever iuslalled in ;elx;ell is conncctcd to thc three Shut down of the back-up pumps will
ShelbyComn; Tennessee, an area pumpsinthcstadonhylhree 14-in. then occur and the first pump will
Ihal etlCOlll])asses Memphis. diameter pipes, cominue to operate until thc wcnvcll
Thc station lkatu~cs std>me~sible level reaches Ihe shutoff level, and
immps opcrating in a dry well envi- ~[~ the compact thc fi~st pmnp will then he shut down.
ity lbcd lrom nearby rtsidcnlial and design, pumps chosen IlCCIS thc pump station to the ~olf
commcr~ iai dcvclopmclns, and pro- for the [nslal[alioa hag Ri;ret Trcatinent Plant and a second
pe]s Iha{ malerial to the new Wolf 30-' ~. forcc main is in place to hai1-
Rixre, Waste~a~er Trea~m¢m Plant to operate horJzo~ta[[y dle higher tlows in the futurc when
just under [btu miles :~';~>r' while laying on the third pump will he acti~rated.
Thc kn-cc mains are hdd about eight
UNDERGROUN9 their s[~o. fl deep over the 17,000-ft connect-
SUg~ERSIBLE OPEUIION lng distance.
Al Ihe heai'l of the pmnp slation's The pump control unit fkmtures X~n-ncr adds, "Depending on
opc]ations ;u'c (}n'ee ITT Flyg( an air buhblcr system when thc which combinalion of three mains
(Trumbull, Connecticut) CZ3231 we(well lexel rises to thc preset "level arc in use and the numher of pumps
150-hppumps,withspaccfi.-afimr/h o~'pos'l'oLap¢sst ¢s~Ctd~'satt'- (pe-t ~gatanygiventime, theflow
lmmp lhat will b~ added as needed, rated causing Ihe lit-st pmnp motor rate will vary from 1,500 gpm with
Thc 39.5 It wide, 14.3 ft deep, 11-fl ~o st;rtl. If Iht? inflow of sewage to thc ont pump to over 9,000 gpm with
mil slation weighs some 140,000 lb weTwcll does not exceed the tirst three pumps operating and utilizing
andisbt.'ied40tlm~derground. The pumpsmaximuml)mnpmgrale,lhe both thc 18-in. and 30in. force
quencydrives, airconditioning, hcat trolled by an at~justable frequency thatcouldbcflcxiblccnoughtomeet
lng, all internal inle~-t onnec(ing pump control systeln timt is conner t- relatively low initial demands and bc
a verlical equipment elevator, and a duccr. Thc pump station discharge needs dictate hy merely switching to
(;ivell Ihecompactdesign frumps ' :" '
lheh' side. Tyler adds, "This was an
well below-~rmmd installation. Of
flooding, Stlbmersib]epumps would ~r .~ ~
er and Arnold a Memphis engi-
contract with d~e tmxn of Col se ~ ~~
liervillc on thc prqjcct since 1994~
' South Dakota, a~e~'~'fl9
expansion d(finitcl}r accclm'ated
60 · September 1999
www, pwmag.com · Pubik:LUol'ks
a different fbrce main or adding ail
additional puinp online. The combi-
nation of Flygt pumps and dual force
mains allows us that flexibility."
He coutinnes, "While the first two
phases of the pump statiou's design
life will he handled by the three
pumps currently installed, the final
stage will be accomplished by simply
adding one identical pump. Thc
additional pump will allow three
pumps to run, meeting the 9,000-
gpm requirement with one space
pump reserved as standby."
For Louis Scbcrt, general inanag-
er and Dakota Pump co-owner, the
$500,000-Collierville pump station
was among tile largest his firm has
produced. The 3/4-in. steel walls,
and 49-11) per ft steel beams, all dou-
ble welded to ensnre leak-proof
operation, should guarantee long
and dependable service.
NO £&~¥ M0¥£
Converting paper plans into opera-
tional machinery was only part of the
KITY'~ fiRflWTH
job. Moving it to the site and secur-
ing its location was equally critical.
When finished in March 1998,
transporting the new station proved
challenging. Il was loaded onto a wide
trucking rig that--under a series of'
special state permits--slowly made its
way from South Dakota through Iowa,
Illinois, Kentucky, and Tennessee.
Only two-lane highways were traveled,
and movement occurred solely
between 8 a.m. and g p.m.
A snrprisingly huge March snow-
storm that dumped up to four fl of
snow along the pump station's route
also slowed progress.
Upon arrival after its five-day
sqjourn, tile pump station was read-
ied for placenzent in a pit carved ont
byRose Construction Company (Cov-
ington, Tennessee) in December
1997 and January 1998. Tile pit mea-
sured 120 ft from tile center in each
direction, and then pyramided down
to 26 ft in each (iirection fi-om the bot-
tom of the pit. Thc elevation differ-
ence from the top to thc bottonl of
the snbgrade was 45 vertical fl.
Rose Construction General Man-
ager Barry Beard recalls, "We
secnred a 450-ton Krupp crane with
a 900,000-lb load capacity to set the
new pump station in place." He adds,
"The 250,000-gallon capacity wetwell
is fi)m' ft from the pump station. It
receives material via two inlets. One
is a 48-in. diameter pipe coming from
the east, the other a BO-in. diameter
pipe fi'om tile west that's ready fin-
anticipated fimlre demands.'
Tyler, whose firm represents ITT
Flygt Corporation and Dakota
Pump, Inc., says he was pleased that
Collicrville accepted his snggestion
to usc thc sealed bid process, once
fi-n- the pump station and once for
the installation. That way additional
equipment nmrk-np and price shop-
ping befbre the bid was negated.
Now in operation, tile new Col-
lierville prethbricated pnmp station
is quietly handliug current needs
while set to handle virtually any
fiUnre growth burst. P~
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