1987-03 March IBEW Journal.pdf - International Brotherhood of ...

"Mighty Mac's" Challenge Met
By Local Union 876 Members
Local 876 members were recemly
Involved in a demanding Job tnvul , ­
Ing the tn. lal lation of a fiber-optic·
cable sy tem lor the MichIgan Bell
Telephone Cumpany across the
Mackina Bridge, which connects the
Upper and Lower Penin -ulas of
MIchigan. MIchiga n Bell is 111staUing
the cable system lor their uHernal
u,e Irom one end of the state to the
oth er, and the crosslIlg at the StmilS
01 Mackinac presented a fomlidablc
hallcnge.
The "Mighty Mac," as It is known,
IS one of Lhe world', greatest uspen­
Ion bndges Wilh an overall length
from land to land of 19, 2.42. lect and
a dlstance between suspension to"' ·
crs of 3,800 feCI, with the uspenslon
span alone belOS 7,400 lect long. The
lowers LhclU~cl vc::' lise approXlmately
575 feel above the Water. Thc
bndge wa thought to be Impossible
to build lor years because of the
trong curren ts 111 the traits between
th e tWO pcnin'Ou las and the tremendous
pressure on the suspensiontoWer
loundatlons from ICC floes during
the long winters. However, the
bridge was linall y completed in 1957 ;
and up until now had never been
ll sed (or anything except vehicle
traffic.
MIchIga n Bell engincers ruled OUt
311 undcrw3lcr c rossing because of
the prevIOusly mentioned problems
amI subsequently negOliated a lea e
WIth the Macklnac Bndge Authomy
10 install a 4-lnc.h ga lvanized-sLCel
conduil acros~ tbe brid 'e in whicb
the cable would be pl aced. One of
the condlllon of the Icase was that
the conduit be installed under the
brit/I:" ruat/way, clear of any mtcr·
fcrcncC' Wllh the bridge authonty's
maintenance trolleys which are used
constantly to inspect and paint the
bndge_
This cOllduion resulted in a cha l­
lenge to the successful bidder, M. ).
El ectric In c. of Iron Mountain, Michiga
n, to deSIgn a movable scaffold
1Q I IBEW JOURNAL! MARCH 1987
Loca18/6 members Wayne VIllwock i:I/ld CI,arles Bishop perform Iheir work on Iho e;pecial scalfold
designed for 1he fiber-optic-cable installation Job on the Mackinac Bridge .
that wOll ld permit the conduit to be
install ed in 20-foot len/lths wilhout
exten ive building aod tearing down
of scaffo lding, Cond that would still
make a sale place for our members
to work wuhollt hlnekillg more than
one lane of traffic. M . ,. Electric'
engineer were able to come up with
a design lor a sca(fold made from
modIfied substation teel [ru c
mounted on a flatbed semitrailer
which were extended OUt over the
bridge rading, below the roadway,
and back unde.r the mat/way a distance
of approximately 8 fee t. An 18-
Ion Grove crane was used to pu ll the
assembly along as tbe nduit was
insta ll ed :and to disconnect tbt; wUlk
platfonn every ni ght to clear the
bridge. A total of 11,736 feet of COndUit
was installed in this manner
between the nonh and south shores
and the north and south su pen ioncable
anchorages. Between the north
and south cable anchorages on the
su pen ion portion of the bridge, tbe
conduit was installed using two 24-
inch by 40-foOl aluminum " picks"
in tead of the work platform because
the su pension cables interfered with
th e passage of the platform.
In addjtion to the pbtIorm, M. ).
Electric'S afcty DcpartIncnt required
that a safety cable be llUng
alongside of the conduit all along the
insta.l lotion rOu t ei LInd the m en were
I