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Balter served as the Geotechnical Engineer of Record for recent upgrades at Dulles International Airport for United Airlines.  The upgrades included the addition or relocation of several jet bridges and tunnels at seven (7) gates.  The new and relocated jet bridges were recommended to be supported on drilled shafts. 


Our Geotechnical investigation and Report identified site soils and rock present at the site.  During our site investigation, undisturbed samples were collected for more sophisticated testing in Balter’s AASHTO accredited facility.  The Geotechnical Engineering Report included recommendations for vertical and lateral capacities of drilled shafts, as well as earthwork requirements for the proposed construction.  

Balter is also the Geotechnical Engineer for upgrades at the Winter Operations facility for United Airlines at Dulles.  The proposed project will consist of the installation of four (4) 30,000-gallon (Type I) and two 20,000-gallon (Type IV) glycol tanks at Dulles International Airport (IAD).  A climate-controlled water building will store water to blend Type I glycol, and on-site water pumps with pipe supports will be used to distribute product.  Future expansion includes one (1) 30,000 gallon and one (1) 20,000-gallon tank.  Balter’s Geotechnical Report includes recommendations for support of the proposed tanks, as well as earthwork and pavement design within the AOA. 

All Geotechnical work at Dulles is performed under certain environmental provisions.  All spoils generated during our drilling operations are placed in drums until Environmental testing and characterization can be performed.  All tooling is also decontaminated between samples to reduce the risk of cross contamination during drilling.  

In addition to environmental provisions, Balter coordinated closely with the FAA to obtain 7460 Permits for work near the main Air Traffic Control Tower.  Constant communication with the FAA, MWAA, United and the design team is paramount to maintaining not only the project schedule, but also to avoid disturbing operations on the airport.  

As Geotechnical Engineer of Record, Balter is provided consulting geotechnical engineering, subsurface explorations and materials laboratory testing services for these IAD projects. With close coordination among United Airlines (UAL), the designer, and MWAA, Balter established and provided a multiple field investigation programs distributed throughout the project limits with borings located in and around active gates.


Our Geotechnical work during the Jet Bridge and Gate upgrades included detailed analyses of collected rock cores.  The collected rock cores were evaluated in order to develop strength parameters for shallower more weathered rock, as well as deeper less fractured rock.  These parameters, along with a detailed study of the site geology, allowed for more accurate strength characteristics of the rock to be developed. 

Using the strength information gained from our detailed rock analyses, drilled shaft design recommendations were provided for support of the new Jet Bridges.  Due to the nature of the structures, a particular challenge involved large applied moments to the drilled shafts due to rotation of the jet bridges.  Recommended rock socket lengths, and caisson reinforcing recommendations to minimize lateral deflections. 

Design of the new glycol tanks also involved detailed observations of the existing rock.  Encountered depths and properties of the rock were required to limit total and differential settlement of the new tanks.  Additionally, the tanks required the installation of new utilities which required lateral support to resist internal pressures within the pipe. 

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