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Oregon Demonstration Project: Alternate Project Delivery And Accelerated Bridge Construction On OR 38, Drain To Elkton
A key aspect of HfL demonstration projects is quantifying, as much as possible, the value of the innovations deployed. This entails comparing the benefits and costs associated with the innovative project delivery approach adopted on an HfL project (i.e., as-built) with those from a more traditional delivery approach on a project of similar size and scope. The latter type of project is referred to as a baseline case and is an important component of the economic analysis.
In addition to analyzing the baseline and as-built construction costs, ODOT used the StratBENCOST1 analysis approach to demonstrate the cost savings that stemmed from improved traffic flow and reduced impact on highway users (i.e., user costs). This analysis is in the "User Costs" section.
ODOT believes that, through overlapping the design and construction using alternate project delivery and using incentive and disincentive clauses and innovative accelerated construction technologies such as HSS, it was able to dramatically reduce the duration and impact of construction activities on neighboring residents, businesses, and roadway users. Although it took several months to complete the construction of the substructure and superstructure for crossings 3 and 4, the as-built construction impact on users was minimal until these structures were ready to be removed and replaced.
As stated earlier, during this removal and replacement time, full lane closures were established on only two weekends on the 11-mi stretch of OR 38 between Elkton and Drain. If a traditional approach had been used to remove and replace these crossings while maintaining traffic on OR 38, ODOT estimates that it would have taken an extra year to complete the project and the impact of construction-related activities on highway users would have been dramatic.
With the use of a temporary structure, ODOT was able to reduce the time for removal and replacement of crossing 5 to only 6 weeks from the original schedule of 6 months.
Overall, traffic was detoured on three occasions. During the removal and reconstruction of crossing 5, a detour was put in place using a temporary structure next to the old crossing. The total distance of this single-lane detour was only 300 ft. The detour use was controlled by flaggers at each end of the detour bridge 24 hours a day, 7 days a week for 6 weeks. Originally, the contractor was given 6 months to complete this bridge, but using a temporary structure enabled the contractor to reduce the impact on roadway users to only 6 weeks and receive an incentive of $135,000. Because of the low ADT on OR 38, the impact on travel time was minimal.
Detours were also established on two separate weekend closures for the removal and replacement of crossings 3 and 4. Motorists were advised in advance to use highway 138, which added about 50 mi to their travel.
Table 1 presents the differences in construction costs between the baseline and the as-built alternatives for crossings 3 and 4. All of the as-built and baseline cost estimates were provided by the ODOT project engineer assigned to this job. The baseline cost estimate is inexact, and the information presented is a subjective analysis of the likely cost differential rather than a rigorous computation of a cost differential.
Note: As-built represents rapid replacement technique.
Generally, three categories of user costs are used in an economic life-cycle cost analysis: vehicle operating costs, delay costs, and crash- and safety-related costs. The cost differential in delay costs was included in this analysis to identify the differences in costs between the baseline and as-built alternatives. The performance goal established by ODOT on motorist delay was that no vehicle should be delayed by contractor operations more than 20 minutes beyond its normal travel time. The contractor met this goal easily. Based on a travel time study conducted by HfL consultants, a delay of 5 to 9 minutes was computed for each vehicle during daytime hours. For the most part, the approach adopted was to maintain two lanes of uninterrupted traffic throughout the duration of construction except for 6 weeks on crossing 5, which required the use of a temporary bridge and two weekend closures for removal and replacement of crossings 3 and 4.
In conducting the user cost analysis, ODOT used the StratBENCOST model, an economic analysis tool widely used for analyzing large-scale transportation projects. This model, developed under a National Cooperative Highway Research Program study sponsored by FHWA, uses variables such as travel time cost, vehicle cost, crash cost, and environmental cost to determine economic savings from employing innovative features in a transportation project.
Table 2 presents user cost savings for all of the crossings except crossing 2. The contractor used no innovative features in reconstructing crossing 2, so there were no savings associated with that crossing.
In addition to achieving the above savings, ODOT cut the time required to complete the project by a full year by using the D-B method of project delivery in place of traditional D-B-B and by using ABC techniques. The potential savings from reduced labor costs and escalation costs of materials due to inflation for a 12-month period was estimated at $1.596 million (or 3.3 percent of construction value). An extra mobility savings of $311,230 was also assessed for all crossings. In addition, ODOT saved $1 million by using ABC techniques, which eliminated the need for detours for crossings 3 and 4. An additional savings of $265,000 was realized on crossing 5 by building a smaller detour and not purchasing additional right-of-way.
Table 3 represents a cost comparison summary of the as-built (accelerated construction) and baseline (traditional construction) alternatives for the entire project. The as-built cost of building crossings 3 and 4 is $933,000 more than the traditional method. However, under the as-built scenario, project completion was accelerated by about a year. This dramatically reduced labor costs, minimized traffic interference with construction activities, and resulted in reduced crashes, travel time, and vehicle operating costs. Considering these factors, ODOT achieved a net savings of $2,448,320, as shown in Table 3.
1 StratBENCOST is a benefit-cost analysis tool developed under National Cooperative Highway Research Program project 2-18(4) to evaluate highway investments at the strategic level (NCHRP Research Results Digest 252, March 2001).