Bridgetown Pike Bridge Replacement
Project ASHE Nominee-2001 Project of the Year
By Peter W. Berthold, P.E., Pennsylvania
Department of Transportation
When the Pennsylvania Department of Transportation decided
to replace the existing bridge with a new bridge on new alignment
outside the floodplain, the Bridgetown Historic District (which
is comprised of four historic properties bordering the project)
required that the "crossroads" between Bridgetown
Pike and Newtown Pike (S.R. 413) remain within the same alignment.
The relocation of Bridgetown Pike to the new alignment would
have resulted in the elimination of the "crossroads"
of Bridgetown Pike and Newtown Pike and the demolition of the
stone mill floodgate walls, headrace walls, and a portion of
the headrace. Consequently, SITE-Blauvelt Engineers was retained
by PENNDOT Engineering District 6-0 to provide consulting services
that were needed to replace the structure, maintain the cultural
features of the historical district, and improve safety and
traffic operations within the study area.
The Bridgetown Pike (S.R. 2010) Bridge over Neshaminy Creek
was borne out of the need to replace an existing two-span, 142-foot-long,
riveted-steel, pony-truss bridge over the Neshaminy Creek. The
existing structure (which was ultimately left in place) provided
a total cartway of only 14-feet by 8½-inches and was
rated for a maximum load of three tons. In addition to the substandard
load rating, the existing bridge had many design deficiencies
that resulted in the need for its replacement. First, the structure
provided insufficient width to allow two-way vehicular traffic.
Second, the bridge was located within a flood plain at the confluence
of Core Creek and Neshaminy Creek that not only resulted in
flooding of the structure and approach roadways during a 50-year
storm, but also contributed to excessive scour at the pier and
abutments. Finally, the roadway alignment did not provide the
needed sight distance for motorists to see oncoming traffic
before crossing the bridge, thus resulting in traffic delays
and safety concerns.
The result was the design and construction of a new structure
to carry Bridgetown Pike over the Neshaminy Creek, in addition
to an additional structure replacement on Newtown Pike (over
Core Creek), realignment of the intersection of S.R. 2010 and
S.R. 413, various roadway safety improvements, implementation
of a bicycle/pedestrian facility, and enhanced bicycle and pedestrian
Significant Design Issues
The existing bridge was structurally unsafe and badly in need
of repairs but was to remain in place during and after construction.
In addition, it was necessary to eliminate an existing substandard
"S" curve in the alignment of S.R. 2010 (west of its
intersection with S.R. 413) that would greatly improve the operation
and safety of S.R. 2010. Realigning the intersection of S.R.
2010 and S.R. 413 also was necessary to rectify safety and capacity
deficiencies caused by the offset of two legs of S.R. 2010 and
to raise S.R. 2010 above the 50-year flood levels without increasing
To arrive at the most viable solution and avoid the use of
properties that were protected under Section 4(f), six alternatives
were considered that underwent extensive study. After careful
evaluation and coordination between PENNDOT and the project
stakeholders, the recommended alternative was to build a new
structure adjacent to the existing structure and maintain the
crossroads. The existing structure would be used as part of
a pedestrian/bicycle facility running thru the project from
Core Creek Park. The proposed action was selected because it
would minimize the impact on the Historic District, require
minimum right-of-way acquisition, and rectify the roadway, traffic,
and structural deficiencies that were present.
Data from previous FEMA studies indicated that both Neshaminy
Creek and Core Creek could cause flooding. As S.R. 2010 is relatively
level in this area, the opening of the structure had to be increased
to maintain the current channel flow rates and backwater. An
H&H study indicated that a 290-foot, continuous two-span
steel girder structure would pass 100-year flood levels. Furthermore,
significant attention had to be paid to the design and alignment
of the pier to reduce scour.
To properly assess the potential for future scour and determine
the appropriate foundation type, a comprehensive geotechnical
study was completed that established the need for a pile foundation
system that had the potential to resist high-stream velocities
and provide stability for a 42-foot high abutment on the eastern
leg. Alternate low-strength backfill was provided to allow the
contractor the opportunity to provide the most economical foundation
Because the existing bridge had been observed to be in flood
conditions and has always been at risk of washing out, design
provisions were made on the new crossing for an 8-foot pedestrian
and bicycle lane in the event that the steel-pony truss became
damaged. Furthermore, the substructure provides for the future
addition of a travel or turning lane if traffic at the intersection
of S.R. 2010/S.R. 413 increases above the 20 year study area
and requires additional roadway capacity in the future. Such
an addition is made possible through the provision of an extended
pedestal and footing width at the pier.
Description of Contract
The project bids were opened in March 2000, with Loftus Construction
being awarded the contract. The contract provided for 24-months
to complete demolition and construction of the entire project.
This included the Neshaminy Creek crossing, intersection improvements
at S.R. 413/S.R. 2010, intersection improvements along the detour
route, bicycle and pedestrian path, and replacement of an adjacent
bridge along the detour route, bicycle and pedestrian path,
and replacement of an adjacent bridge along Newtown Pike crossing
Core Creek that was impacted by the improvements to the intersection.
The proximity of emergency services that traveled the structure
and the current traffic volumes along Bridgetown Pike, caused
a review of the six-month closure proposed for the bridge during
construction. This closure was reduced to two weeks by constructing
a temporary roadway on an adjacent property owner's frontage,
constructing a temporary pile and lagging retaining wall to
withstand embankment needed to construct the new structure,
and installing a one-lane narrow roadway, with temporary traffic
signals on each end controlling the direction and flow of traffic.
Secondary impacts were identified along the detour route and
were mitigated through the implementation of intersection and
signal timing improvements.
The estimated cost for the project was $6 million. Through
the aggressive maintenance and protection of traffic program,
project work task scheduling, and innovative construction solutions
to problems experienced in the field, the project was completed
in only 18 months, with a final cost ($5.4 million) that was
90% of the estimated amount.
The new structure on Bridgetown Pike is a two-span,
continuous-composite, steel-plate girder, with one span being
148-feet long and the other 142-feet long, supported by concrete
abutments and a pier with steel H-pile footings. Weathering
steel was used for the superstructure, steel beam guide rail,
posts, terminal section, and all appurtenances and hardware
so that it would blend with the historical surroundings.
On the western leg of Bridgetown Pike, a mechanically stabilized
earth (MSE) retaining wall was constructed to protect the recreational/bike
trail from motorized traffic and to retain the embankment of
the proposed roadway. The wall was connected continuously with
the proposed bridge structure, and the same aesthetic treatments
were used to maintain the rustic appearance of the structure.
To match the colors and textures of the site, SITE-Blauvelt
focused on the colors and textures of the native building materials.
To blend with colors found in the immediate vicinity of the
site, the concrete was stained and mortar joints were used to
simulate the look of laid stone. The form liners that were used
for the concrete provided a random looking pattern of stone.
By staining the concrete at individual stones, additional variation
was provided to give a natural look.
Landscaping around the bridge was important because of the
historic setting of the area. Every effort was made to limit
the necessary work zone utilized by the contractor and reduce
the number of trees that were required to be removed. Areas
that had to be disturbed were regraded and planted with tree
species that were agreeable to the adjacent property owners
and the Historical District Society.
Although the footers were supported on piles, the pile caps
had to be depressed below grade to minimize the potential for
future scout. This required the contractor to install a temporary
cofferdam to divert Neshaminy Creek around each substructure
being constructed and divert Core Creek through temporary pipes
around the back of the abutment to also minimize its impact.
Because of unexpected storms through the first construction
season, the contractor had to reestablish the stream diversion
and temporary stream crossing during construction of the pier
Because of the height of the abutments (42 feet), high-strength
concrete was used along with low-specific gravity backfill material.
The causeway was reinforced with additional strength to provide
for the 900-ton crane that was needed to aid the contractor
during beam erection. With the 148-foot spans and use of the
larger crane, the beams were off- loaded on one end of the bridge
and swung into position.
Positive community relations were key to the successful completion
of the bridge replacement. The design was developed in conjunction
with the steering committee and the Historical District Society,
which emphasized the need to maintain the historical crossroads
and build the structure within a flood plain. Various historical
and aesthetic issues arose during construction, as well as the
concern that the new bridge would contribute to increased flooding
problems. To the satisfaction of the community, the contractor
was able to reestablish Core Creek to an improved condition
with the completion of the new structure.
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