i
Nor more wet clothes steaming up the
windows this winderThe entire week1
washing FINISHED (washed AND dried)
in one short hour while .you read, knit
do bead •work or ‘write letters. Bet
s
ter yet - take a shower-.and roll up
youir hair while
^ou wait*
0.
00
r i r)
STATE OF ALASKA • NEWS RELEASE
Road and bridge building in Alaska is haH
mpered by rugged country.- severe weather, p- ;
remanently frozen earth, and other such
problems that the highwayyengineers hare have
come to accept as commonplace, but it seems
that each yeah brings another rare opportun
ity for t ese,engineers to pit their skills'
against the elements of a wilderness state
And the latest one-phenomenal though j
it may seem-— -: ib a natural phenominon, a
lake that/ re ate s itself each year and joist
as-'regularly empties itself / gorging the val-j
ley below with tremendous forces of water and:
iceo:But engineers from the Alaska Department
of Highways not only have conquered the ' .
problem, they have accomplished the studies
and design of Alaska!s beggest highway
projects in record time.
The Knik-Mat anus ka bridges and related
road work —- a §7 million project -
will be advertised this fall, following ten
months . of intense design work once the
projebt was condiered a priority job for the
stateo It involves three major cro sings of:
the Matanuska River, and one long span over
the Knik ^iver, a total of 4^076 feet of
continuous steel plate girder bridges, and
207 miles of new roadway to tie it to the
pre-bent primary hig i/ay system*
It is the biggest single construction
project ever to be undertaken by the Ai^c-Va
Department of HighwaysV ’
Although state engineers cuuld see the
need for a new structure to replace a 27 '
year- old truis bridge' over the Knik river,
there was no real urgency until May 1962, wh
en a truck carrying an overheight load;forced
its way through the old bridge bending portal
and vertical’ members and bracings of the
already damaged structure-. The maintenance j
forces of the Department of Highways ac.com-* i
plished $5^*000 worth of repair work on
the "bridge, but it will never be suitable
for heavy trucks again. Due to the severe "
structural damage, trucks presently are
restircted to a 10-ton load limit, one-way
traffic and no gear change while on the
bridge•
State bridge engineers studied the dama
ged structure at lenght. They found it was
not designed to carry the heavy loads allowed
A Shake goes good with a burger
on Alaska Highways, and that it would not be !
able to withstand many more trips with res
tircted loads. The 2.000 foot bridge, at
Mile 3$ on the Glenn Highway, is the lifeline j
to Anchorage, the largest city in Alaska
- if the bridge is out, Anchorage would not
have a direct land connection with the rest of
the United States, It was determined that
the bridge was badly overstressed for streng
th and traffic safety, and a crash program
was initiated to replace the weak structure.
In November subsurface explaoration was
begun and c ntinued throughout the winter*
•^he Department of Highways also requested the
United States Geological Survey to prepare
a bridge site report involving the study of
hydr°l°gic nnd hydraulic charactierisitcs
of the streams, meanwhile the Anchorage
^istirct Highway Office began surveys to de- !
termine the proposed centerline of the new
road and bridge complex. . ..
One of the problems confronting the
bridge design engineers was the annual break-:
up of Lake George, a glacial lake high above
the Glenn Highway. . According to the U.S.G.S.
report:
uFlooding in the Knik River Valley is
caused b' the annual failure of ice-dammed
lake Georgeo Continuous forward movement of.
the Knik Ciacieh keeps the Knik River plugged
with sblid ice except for a narrow channel
between the ice ’front and Mount Flamer. This j
narrow' channel, known as the Go,ge, is. kept
open by the emptying of lake George during
the late summer. After the lal:e_ has drained I
and the outflow roughly equals the inflow,
the Gorge becomes stable, Then after the ,s- 1
nowmelt decreases, the advance of the glacieit
overcomes the erosion of the river and closes^
the Gorge to form next seasonfs ice melt.11
When this natural phenomenon occurs,the
stream flow, which is normally around 10.000 '
cubic feet per second, swells to more than ;
350.000 c,f,s, Consequently, exceptionally I
high velocites of flow had to be taken into :
consideration for.bridges across this inter
braiding strea. 6ince it was anticipated
that scour may occur as much as 50 feet deep !
at the abutment.ar~as, rock, riprap protec- ;
tion plays an important part in the design.
Spur dikes also will be pi j
upaCream to guide the riv^x-’s flow before
it reaches the stincture., thereb alleviating
some scour damage, and all piers are armored ;
against ice and designed to take the shock
of ice flows. *
■X--X--X--X K X X X
; . • • • • X \ . > 1
All the bridges are identical in detail j
so tint. they can be mass produced in the fi
eld by repetitive work, a factor that could
save considerable money in a project of this
size. ..Of the four bridges, the Knik crosssing
is the- longest with a total lenght of 1.524
feet . / •.
500cm(. oif tanks $ 125
^ 0 QArV’ r)~r,01
f< JlUl)f JJ
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