ACPA Quarter 3 2016

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Quarter 3, 2016 7
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Diamond interchanges and roundabouts
are not new in Pennsylvania, but the combina-
tion of a new diamond interchange along with
concrete roundabouts at the ramp intersec-
tions is something new for District 12 of the
Pennsylvania Department of Transportation
(PennDOT). The project also includes another
innovative approach—concrete roundabouts
constructed with stringless paving technologies.
The New Stanton interchange at I-70 will replace
two existing interchanges that were spaced so
closely together that adequate deceleration and
acceleration lanes could not be provided. “Use of
the diamond interchange and the roundabouts
is the most efficient design because there is a
tighter footprint for the interchange,” explains
Dominec Caruso, P.E., Assistant Construction
Engineer for the district.
New Interchange Features Diamond Traf fic Pat tern
and Multiple Roundabouts
By Sheryl S. Jackson
The total project includes widening and recon-
struction of I-70 for approximately 1.8 miles.
I-70 will be widened to provide a third lane
in each direction for 2,900 feet between the
existing turnpike interchange and the new
interchange.
To provide a connection to the new interchange,
one street will be extended to two others, con-
necting to one via roundabout, and some existing
streets that are routes to the new interchange
will be reconstructed with the project. The cost
of the total project is $53.7 million; it started in
August 2015 and completion is scheduled for
November 2018.
“It makes sense to build concrete roundabouts
because the rest of the interchange is concrete,”
says Caruso. “This provides a continuous paving
structure, reduces maintenance and ensures
the life cycle of the roundabouts and other
components of the interchange are the same.”
The first roundabout to be completed was the
circular roundabout that connected two streets
that provide a route to the new interchange. “This
was the first concrete roundabout we’ve paved,”
says David Sciullo, P.E., Vice President of Con-
struction for GoldenTriangle Construction. “Slip
forming in a tight radius of 65- to 80-feet presents
a challenge to keep all paving legs in sync as the
machine turns,” he says.
A trial run was held prior to paving to make sure
the slip-form paver is calibrated and ready for
concrete. “When we do a ‘dry run’ on a mainline
roadway, we may travel 100 ft to test the paver,
but we went completely around the roundabout
to make sure everything was running correctly,”
says Sciullo.