DDOT – Frederick Douglass Bridge Replacement/South Capitol Street Realignment
Prince William County, VA
Prince William County / VDOT / Stantec Inc.
This design-build project involved widening about 2.0 miles of Route 1 (Jefferson Davis Highway) from a four-lane undivided highway to a six-lane divided highway with a raised median. The proposed construction work began at the intersection with Neabsco Mills Road and extended generally northeast to end at the intersection with Featherstone Road. The proposed construction also included new turn lanes, six concrete retaining walls, one stormwater management (SWM) pond, a new quad 12’x12’ concrete box culvert at Cow Branch, new sidewalks and asphalt trails.
DMY provided the following services:
Subsurface Investigation: DMY implemented a design level subsurface investigation program consisting pavement coring, soil test borings, in-situ soil sampling, groundwater monitoring, and laboratory testing in accordance with the VDOT MOI guidelines.
MOT Design: DMY designed and implemented a temporary traffic control program including lane closures per VDOT requirement to facilitate the subsurface investigation program.
Geotechnical Engineering: DMY prepared a final geotechnical report with geotechnical recommendations in accordance with VDOT MOI guidelines. Engineering design and analysis for asphalt pavements, retaining walls, large culverts, SWM ponds, embankments, and slope stability were provided.
Laboratory Testing: DMY performed a series of laboratory tests in our in-house AMRL certified laboratory. The tests consisted of soil classification, Proctor compaction, CBR, pH and Resistivity, as well as direct shear tests.
One major challenge of this project was the complex history of the existing pavement. The project section of Route 1 was originally built in early 1920s as a two-lane plain concrete pavement roadway. Over the past century, the roadways have been overlaid, widened, reconstructed, and realigned numerous times. DMY thoroughly researched the available pavement records from VDOT, the County, and other resources and performed a detailed site reconnaissance to visually evaluate the existing pavement conditions. DMY then prepared and implemented a pavement coring program based on the historic data research, existing pavement condition review, and the proposed roadway widening. The final pavement design consisted of mill and overlay of the existing pavements, pavement widening, and pavement reconstruction at various sections.
Another major challenge was the widespread presence of the wet and unstable subgrade soils at the site. The conventional undercut and replacement approach is time consuming, costly, and susceptible to inclement weather conditions. DMY worked closely with the design and construction team to design and implement a subgrade soil improvement program, including lime treatment of the wet and unstable subgrade soils. The lime stabilization design involved a series of laboratory tests to evaluate the lime contents, compaction characteristics, and strengths of the treated subgrade soils. All tests were completed in DMY’s in-house lab. The successful implementation of lime treatment on this project greatly helped reduce schedule setbacks and costs.
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