Public-Private Partnership Success
Ship Road and Swedesford Road Intersection Improvement Project
By Robert G. Prophet, P.E.
Project Manager, Highway Design
Traffic Planning and Design, Inc. (TPD)
Success
In
October 1998, Traffic Planning and Design, Inc. (TPD) began
design work on the Ship Road and Swedesford Road Intersection
Improvement Project in West Whiteland Township, Chester County,
PA. After construction was completed in April 2001, TPD and
West Whiteland Township won "2nd Runner Up" in the
Pennsylvania State Association of Township Supervisors (PSATS)
20th Annual Road and Bridge Safety Improvement Award program,
judged by a panel comprised of representatives from PHIA, PennDOT,
and PSATS. The "job well done" included structural
design, traffic signal design, intersection improvements, and
highway widening and realignments which "resulted in well-documented
safety improvements." This project also received Honorable
Mention from the Delaware Valley Section of the American Society
of Highway Engineers (ASHE) for 2001 Project of the Year Award.
As described below, this project involved close coordination
with multiple stakeholders and regulatory agencies, and required
quick turnaround due to other construction projects scheduled
in the surrounding area. Other firms contributing to this project's
success included Pennoni Associates, Inc. who completed the
original traffic study which included alignment alternatives
and Eastern States Engineering who completed the survey and
site work for the adjacent Swedesford Chase development being
constructed by Toll Brothers, Inc.
Project Description
The intersection of Ship Road (State Road 1001) and Swedesford
Road (Township Road 413) is located in West Whiteland Township,
Chester County, PA approximately ½ mile northeast of
the Exton Square Mall. Both Ship Road and Swedesford Road are
used as bypass routes for motorists trying to avoid traffic
delays and traffic signals on PA Route 100 (1/2 mile west of
the intersection) and Business Route 30 (1/2 mile south of the
intersection) both of which are classified as Principal Arterial
roadways. This junction was originally designed as two "T"
intersections, offset by approximately 275 feet, with a tributary
to Valley Creek located between the two intersections. This
type of design was commonly used in the early part of the 20th
century to avoid multiple stream crossings by both of the intersecting
roadways. This offset required vehicles traveling along Ship
Road to make two turning movements, therefore, increasing commuter
delay and the possibility of crashes. Concerns with the existing
intersection were magnified due to the large volume of vehicles
performing this movement and the consistent flow of traffic
on Swedesford Road, which did not allow for proper gaps in traffic.
A traffic study, which analyzed various design alternatives
for the intersection, was developed in late 1997 by Pennoni.
The focus of the study was to increase the safety and mobility
at the intersection of Ship Road and Swedesford Road. Based
on the study, the selected intersection improvement alternative
included signalizing the intersection, realigning the western
and southern legs of the intersection to create a single skewed
four-way intersection, and the addition of left turn lanes on
each approach. In October 1998, Toll Brothers, Inc. and West
Whiteland Township employed Traffic Planning and Design, the
Township Traffic Engineer, to develop plans for the intersection
redesign. The plans were required to be prepared and submitted
to PennDOT as a Highway Occupancy Permit (HOP) application with
West Whiteland Township as the permit applicant.
Design of the intersection was complicated by several factors
within the project limits including the Tributary to the Valley
Creek, the proximity of a Township and County Park on the northeast
and southeast corners of the intersection, historic structures
on the northeast and northwest corners, and the presence of
wetlands on the northeast corner. An existing 3'x 6½'
reinforced box culvert carried the Valley Creek tributary beneath
the offset leg between the two T-intersections. Originally,
it was expected that this existing box culvert would be able
to be extended as required or replaced with an elliptical pipe.
However, preliminary coordination with DEP eliminated this possibility.
Following this coordination, further research of the flood history
within the area indicated that the existing culvert had potential
flooding concerns. These concerns, along with the anticipated
extensive intersection improvements, dictated that the existing
box culvert be replaced. During the design process and the flood
history research, concerns also arose about flooding, which
was occurring in a residential area located downstream of the
intersection. This flooding occurred along the tributary to
the Valley Creek during higher intensity storm events. Therefore,
any design of a replacement box culvert carrying the creek through
the redesigned intersection needed to be developed in such a
manner as to minimize impact on downstream property owners.
Based on TPD's in-depth hydraulic analyses, the replacement
structure required for this project was 5½' x 14' reinforced
box culvert with a total required length of 206 feet. The extensive
culvert length was required because the Valley Creek tributary
flowed directly through the center of the proposed intersection.
Any attempts to relocate the intersection were prohibited by
the adjacent park and the adjacent historic structures, while
any attempt to minimize the culvert length required significant
stream relocation. Therefore, the location of the creek was
not altered as part of this project and the culvert was designed
and constructed at the 206' length. Since the total length of
the box culvert exceeded 100 feet, it was sized to handle a
100-year design storm. TPD coordinated with the Army Corp of
Engineers, Department of Environmental Protection, Chester County
Conservation District, and Trout Unlimited throughout the development
of the design of the box culvert.
Due to a scheduled structure replacement on PA Route 100, approximately
½ mile west of the intersection, West Whiteland Township
imposed extensive construction deadlines, since this intersection
would provide alternative traffic routes for commuters affected
by the elimination of one lane in each direction on PA Route
100. Due to this intense schedule, TPD, West Whiteland Township,
and PennDOT coordinated closely to achieve the required deadlines.
As a result of the tight schedule and late addition of structural
design tasks, a final structural plan package included a combination
of geometry, plans; and details developed by TPD, along with
specific precast culvert and precast wingwall shop drawings
provided by Rotondo Precast. This modified submission format,
which required extensive coordination between TPD, the Township,
PennDOT, Rotondo, and the contractor, resulted in the successful
fabrication and installation of the replacement culvert within
the required time constraints. A typical PennDOT submission
procedure would have extended the fabrication and construction
schedule by a minimum of three months.
Another element, which increased the complexity of the design
and coordination of the intersection realignment, was the presence
of eight (8) utility companies. There were five (5) existing
above-ground and underground utility lines, which were going
to be affected and, therefore, required relocation as part of
this project. An additional three (3) utility companies requested
that their lines be relocated/extended through the intersection
while it was under construction. Of particular concern was a
high-pressure Sun Oil pipeline running parallel to Swedesford
Road immediately south of the intersection. As part of this
project, the proposed box culvert was to be extended to the
south of the existing intersection immediately above the pipeline.
Therefore, a decision was made to relocate the high-pressure
line approximately 50 feet to the south to avoid any conflict
with the box culvert. Closure of the gas line required extensive
coordination with Sun Oil, West Whiteland Township and an adjacent
construction site located 1 mile east of the intersection of
Ship Road and Swedesford Road.
One final design element, which required special attention
of the utility companies and contractors, was the proximity
of two 100-year old trees on the northeast corner of the intersection.
West Whiteland Township officials requested that the trees remain
undisturbed during construction. Therefore, special measures
were taken when designing the curb line and utility relocations
as to not disturb the trees. To ensure that the trees would
survive construction, an arborist was hired by the Township
to trim certain portions of the trees where root damage could
have occurred.
Contract and Scheduling
Construction of the intersection improvements was performed
by Allan Myers, Inc. and managed by Toll Brothers, Inc., who
funded the improvements as part of their adjacent Swedesford
Chase land development. Construction was performed under a full
detour condition to accelerate completion and to allow for improved
safety during installation of the box culvert. Both the Township
and PennDOT deemed completion of the intersection improvements
critical due to the upcoming reconstruction of PA Route 100
through the Exton Mall area. PA Route 100 was scheduled to be
reduced from four lanes to two lanes in order to complete the
widening of a major structure. Traffic from PA Route 100 was
to be partially diverted onto Ship Road during that period.
Due to the efforts of West Whiteland Township, PennDOT, Toll
Brothers, Allan Myers, Rotondo, and TPD, the intersection improvements
were completed and the road was opened in time for the PA Route
100 lane closures. The following is a summary of the key events:
Commence Intersection Design November 1999
Commence Structural Design March 2000
Intersection Design Approved April 2000
TS&L Submission April 2000
TS&L Approval May 2000
Construction Started May 2000
Final Structure Plan Submission July 2000
Fabrication of Box Culvert Started July 2000
Final Structure Plan Approval August 2000
Utility Poles Relocated August 2000
Construction Substantially Completed September 2000
Roadway Open to Traffic September 2000
Final Paving and Pavement Marking April 2001
(Construction completed)
Significant Techniques or Innovations
The design and construction of the improvements at Ship Road
and Swedesford Road involved extensive public-private partnership.
Through this partnership, the design and construction of the
intersection improvements were completed within a seventeen
(17) month time period. This time period is significantly less
than the typical four-year time period for design and construction
of a similar size publicly funded project.
Coordination was critical to the successful completion of design
and construction of the intersection improvements. This involved
multiple meetings with utility companies, Township officials,
PennDOT, Toll Brothers, Inc. and TPD. In addition, engineers
from TPD met with Rotondo Precast, the box culvert fabricator,
to discuss and coordinate design issues, shop drawings, and
final structure approval. This intensive coordination culminated
in a final structure submission to PennDOT, which included drawings
and details provided by TPD and shop drawings prepared by Rotondo
Precast. This process expedited the approval and construction
schedule by approximately three months.
An additional method used by the designers and contractors to
accelerate the project was employing a full detour in which
all four approaches to the intersection were closed to traffic.
This method allowed for the reconstruction of Ship Road and
Swedesford Road and the continuous installation of the 26 segments
of the box culvert. The detour allowed for extended work hours
and provided staging areas for vehicles and equipment necessary
for the installation of the box culvert.
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