DCA HOLD BAY 4 - DESIGN AND CONSTRUCTION PHASES
This project consists of the reconfiguration and expansion of the Taxiway B Hold Bay apron at Ronald Reagan Washington National Airport (DCA). Several design elements are included in this project. The apron is being expanded to support larger aircraft including the Boeing 757-200W and the Airbus A321-200S. Associated expansion requires that the existing blast fence and exisiting VSRs be relocated west of their original locations. This blast fence and VSR relocation enabled MWAA to reconfigure the existing glycol storage tanks located at the Taxiway B area and relocate them in one engineered area in lieu of randomly located around the glycol truck lot. With these new features, new high-mast light poles will be constructed, and two (2) new 80,000 gallon Glycol Storage Tanks rounded out this design.
The Robert B. Balter Company (Balter), as Geotechnical and Pavement Engineer of Record, provided consulting geotechnical engineering, subsurface explorations and materials laboratory testing services for this DCA project. With close coordination among the designers and MWAA, Balter established and provided a field investigation program distributed throughout the project limits. Multiple work hours, both day and night, were required based on the airport activities with shortened apron closures located between morning and afternoon flight schedules. Detailed work plans and permits were developed for MWAA approval.
Balter performed extensive geotechnical evaluations considering various structural load parameters, aircraft data, and the field and laboratory results to develop geotechnical recommendations for all of the project elements.
Foundations comprised of both shallow foundations and deep foundations and soil improvement recommendations for the new blast fence, the glycol tank foundations, and the high mast light poles.
Significant lateral load analyses using multiple iterations of load combinations was performed on the high mast poles which resulted in efficiently bearing on caissons. Close consulting with the project structural engineer was required to fully evaluate certain light pole structures due to their close proximity to the new blast fence location. Foundations at these locations recommended a combination caisson-grade beam footing to support both light pole and blast fence.
Discussions with the blast fence designer to gain an understanding of the structural components allowed for mostly shallow footings for support of the wall, given the variably unsuitable site soils encountered throughout the project.
Balter provided detailed evaluations of the proposed large glycol tank foundations. The deep soft Potomac River sediments presented a challenge related to allowable settlement tolerances for support of the tanks. An aggregate pier system was recommended which allowed for use of standard construction and improvement of those soils. Participated in significant reviews of the Contractor led aggregate pier design.
Related to pavements, Balter developed a P-501 pavement section for the new Hold Bay apron as well as a new VSR pavement section using FAARFIELD and AASHTO methods for pavement design.
Balter has been providing QA Testing and Inspection, as well as Special Inspections during the Hold Bay 4 project as it has moved into construction. This Special Inspection Program has included:
Bearing Capacity testing and compaction
Reinforcing Steel Placement Inspection;
Concrete Testing and Materials Laboratory Compressive Strength Testing.
Anchor and Bolt Inspections
Deep Foundations Inspections
Balter has also provided QA and acceptance testing on P401 and P501 materials. This testing icluded percent within limits (PWL) for all materials, as well as flexural beam testing in our highly accredited laboratory.