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From environment issues to traffic flow to fluctuating state budgets and funding, there are factors both visible and unforeseen that can prolong a transportation project from a few years to many. A prime example of an evolving roadway project takes place in the northwest corner of New Hampshire. U.S. Route 302 was constructed in the 1930s and runs through three small towns for about nine miles...from Bath to Landaff to Lisbon. The region shoulders the mountainous topography of the White Mountain National Forest. The towns are hampered by logging trucks, sixteen wheelers, and tourist buses visiting the local museum and taking in the local color. The area has several historical properties that take a beating from the vibration of the truck traffic, not to mention the exhaust and other hazards delivered by in-town traffic.
A Roadway Project Begins
In 1992, the New Hampshire DOT publicized an RFP (Request for Proposal) for the development of Preliminary Designs for Route 302. The project began with aerial mapping, topological maps, and careful onsite analysis of the local vicinities. Civil engineers would assess the needs of the local communities, with major considerations being traffic delays, safety, and curtailed access to businesses. Preliminary design alternatives were completed in the following two years. The proposed new route would cut a beeline on the outskirts of Bath and Landaff to adjoin two sections of existing roads. The new artery would travel through mountainous terrain and involve large cuts and fills requiring extensive temporary erosion control measures. New intersections and bridges would also be factored into the plan.
The evolution of the Route 302 plan proceeded to 1998. The results of the environmental and engineering studies were reported in an environmental assessment (EA) and reviewed by local residents, state and federal authorities. Based on their feedback, the EA was finalized and is the base document and resource that defines the finished roadway project.
The Roadway Endeavor Advances
In 1999, the New Hampshire DOT posted an RFP for the final design and preparation of construction plans for the reconstruction of 5.5 miles of Route 302 in the towns of Bath and Landaff. The work would entail improvements to the engineering designs, the widening of an existing bridge, construction of three new structures, right-of-way impact plans, stormwater management, wetland impact and mitigation site plans. The project construction costs were estimated to exceed $30 million dollars, and involved 2M cubic meters of earthwork.
SEA Consultants of Concord, NH was chosen as the Prime Consultant, and the head of a multi-disciplinary team. The project commenced with another round of aerial mapping at a much lower altitude, and continued with supplemental field surveys, and site wetland delineation and mapping. The firm prepared base plans, and traffic control plans and detours, as Route 302 would have to stay open during all the construction phases.
In 1999, the New Hampshire DOT modified their CAD guidelines, and SEA standardized on MXROAD and MXRENEW (Infrasoft Corporation, Beverly, MA) design software, and Microstation (Bentley Systems, Exton, PA). The original design data created in 1992-93 was imported into the new CAD system. The MXROAD software introduced a whole new approach to transportation design with its 3D strings technology.
Louis P. Caron, P.E., a veteran civil engineer, has supervised the project from the beginning. "The original design alternatives and alignments were created in a much older version of AutoCAD, a CAD system we were using at the time. The designs were created with a template method (2D cross-sectional views), a standard way of representing roadway elements at the time."
"With MX software, we have no data translation problems with the NH DOT, not to mention that we meet our customer's (NH DOT) needs," states Caron. "The software is great for generating many preliminary alternative designs. It also enables us to rapidly transfer ideas onto paper and into deliverables for project reviews. For this phase of the Route 302 project, we had to take the alignments developed years before in AutoCAD, and convert the coordinate system from English to metric to meet the new specifications from the NH DOT. We imported the 2D alignment work and started with a brand new line model in MXROAD."
Stepping into the 3D World of Design
Using MX input files, a user can capture and archive 3D design data, coordinates, and command lines into associated files, and use them at a later date for modifications. "You can modify intersections through input files," said Cecil Luckern, civil engineer and CAD specialist with SEA Consultants. "Designing complex intersections has always been problematic using a template-based system and very labor intensive. It would take me 9 to 10 times longer to make a change in a template-based system, as opposed to a strings-based system, for a simple intersection. This is where the real power of the 3D software lies. Troubleshooting is also easier with 3D strings technology. For example, in a super elevation condition, if you elevate the high side, there are points critical for drainage. The software program can plot the break in the shoulder, so the engineer can immediately see if the super elevation is right," resolved Luckern.
Luckern's main challenges were to hit the grades, put in temporary road designs, and develop drainage systems in areas of steep grades. "I can also change horizontal or vertical alignments or offsets using input files. When I start a design, I use MX for the design and alignment phase. I capture those commands into input files. If I need to flatten a curve on a design, I can simply change the input file and rerun the design. That's the beauty of the software."
As a part of the Route 302 project, the consultancy also needed to compute quantities and estimate probable construction cost. "For this task, we use CAD to great advantage," cites Luckern. "Using input files, I can select materials, such as gravel or stone, and automatically estimate the amount of materials required for any part of the job. That's just another way we enjoy time savings."
Three-dimensional models have also improved collaboration and communication for the civil design team. "From the standpoint of visualization and decision-making, I need to generate a plan, a profile and cross sections, for Lou (Caron). He is the visual engineer here and he needs to study all of the elements of the project. I can create 3D objects, such as drainage pipes, sewers, telephone or power lines, and easily place copies of the objects in the plan. And by working in a 3D environment, all the 2D documentation derived from the 3D model automatically captures the small nuances of new layouts. If you had to draft this in 2D, it would take days."
A Tale of Two Cities and One Road: The Bath-Landaff Roadworks in 2002
The final design of the Route 302 Bath-Landaff project is currently on hold awaiting further subsurface soils analysis. A roadway segment in Landaff was completed in 2001 and ready to plug into the new road system. As the last modifications were added to the CAD designs, it looked as if the project would be on its way. A new dilemma arose when new geotechnical reports revealed the soil was weak in areas requiring substantial grade changes. Thus a new round of design changes is likely to facilitate this additional contingency. Cut sections with substantial grading up to hundreds of feet into the mountainside may need to be reworked. Construction on this project will likely begin in 2004.
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