PGS: Gildea on geophysical site characterization

Please note the December meeting is a week early (first Thursday) to avoid conflicts with the AGU Fall Meeting.

Please join us for the December 5, 2019 meeting of the Potomac Geophysical Society at 7:00 p.m. at the DoubleTree by Hilton McLean Tysons, 1960 Chain Bridge Road, 22102.  As always, guests are welcomed and we encourage you to spread the word about our meetings to your colleagues and students (a flyer is attached).  If you plan on attending, please RSVP to by noon Monday, December 2.  We hope to see you there!

This month’s program:

The Use of Geophysical Surveys for Enhanced Site Characterization of Infrastructure Projects
by Kevin M. Gildea, EIT

Planning the expansion or construction of large infrastructure, such as roadways or airports, often begins with site characterization activities that use standard drilling and sampling techniques performed under the direction of a geotechnical engineer. In project areas that have the potential for geologic hazards, such as karst terrain, geologic contacts between units with contrasting physical properties, or structural geologic features such as joints/faults/fractures, this approach has often lead to poorly characterized site conditions resulting from low data density prior to construction. Poor site characterization can lead to unforeseen geologic conditions being encountered subsequent to breaking ground. If unforeseen conditions are deemed significant enough to consider a new design, poor characterization can lead to substantial project delays and increases in cost. As a result, the incorporation of a well-scoped geophysical survey calibrated with appropriate boring information is a valuable tool during the project planning and early site development, especially on large-scale projects.

This paper will present the results of several case histories in which multiple geophysical methods, supplemented by geologic data, were utilized to image potential geologic features of risk beneath, or in the vicinity of, a variety of infrastructure. These case histories involve the use of multiple geologic resources, LIDAR data, terrain conductivity via frequency domain electromagnetics, microgravity, electrical resistivity imaging (2-D and extrapolated 3-D), and downhole camera confirmation to best characterize potential geologic and/or geotechnical hazards. Upfront geophysical imaging, as opposed to reactionary geophysical imaging, allowed for the construction management team to properly plan and make more informed decisions to minimize total construction costs and schedule delays while maintaining safe working conditions.

Kevin Gildea holds both a B.S. in Geology & Geophysics and a B.S. in Geological Engineering from the University of Wisconsin-Madison.  His work as a geophysicist at Mundell & Associates, Inc. and a Water Resources Engineer at H2M Associates, Inc. has included field acquisition and analysis of seismic and geophysical data, three-dimensional visualization of city infrastructure and landscape groundwater flow models, and engineering design and construction management on water infrastructure projects. Kevin specializes in integrating a variety of near-surface geophysical surveying techniques and geospatial analysis tools towards solving the world’s continual infrastructure development and improvement needs.

The PGS meeting location is within one-half mile of the Tysons Corner Metro station, near I-495, and has free parking available.  Our private meeting room is located on the second floor of the hotel.  The optional dinner cost will bediscounted to $35 for members in good standing (have paid dues), and $45 for non-members, and is inclusive of coffee, tax and gratuity.  Drinks may also be purchased in the private meeting room on a cash basis.  Members and guests may attend the presentation after dinner for no charge; we estimate that the presentation will begin at 8:15 p.m.  For attendees who arrive early, social time will be held at the Tysons Social Pub on the first floor of the DoubleTree by Hilton hotel.

In summary:
Social Time: 6:00-7:00 p.m., Tysons Social Pub, first floor DoubleTree by Hilton
Dinner: 7:00-8:15 p.m., Overlook Room, Social Cafe, second floor DoubleTree by Hilton

Meeting & Presentation: 8:15-9:30 p.m., Overlook Room, Social Cafe, second floor DoubleTree by Hilton

Future meeting dates: Jan. 9, Feb. 13, Mar. 12, Apr. 9, May 21

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