April 2005 Meeting Abstract
Expansive and Compressive Soils in Amherst, New York
The Buffalo Association of Professional Geologists (BAPG) is pleased to announce that its monthly dinner meeting will be held at Marinaccio’s Italian Restaurant located at 5877 Main Street in Williamsville on 20 April 2005. The topic of the dinner presentation and discussion will be “Expansive and Compressive Soils in Amherst, New York” presented by Brad Guay from the US Army Corps of Engineers, Buffalo District. The presentation will focus on describing the geography, geology, and geotechnical data gathered during USACE’s one year investigation of foundation related damages to structures Town of Amherst in 2004.
Foundation damages generally result from lateral pressure and/or settlement. Of primary interest are the lacustrine soils in the lowland between the Niagara and Onondaga Escarpments. In Amherst, three-quarters of the homes receiving a foundation repair permit are located on these lacustrine soils. Of concern to surrounding towns, these soils extend 35 miles along an east-west trend from Grand Island to the Tonawanda Indian Reservation.
Geotechnically, the soils are classified as moderate to highly expansive. Expansive soils undergo volumetric changes as moisture content varies. Available water, confining pressures, and initial moisture content also influence potential volume change. In Amherst, a second causative factor for settlement involves the soft clay stratum beneath the stiff clay stratum where many residential footings are placed. This soft clay stratum is susceptible to consolidation by dewatering and surcharge loading.
Risks associated with building on expansive soils have been well known for decades in such Western states as Colorado, Texas, and California; however, experience with expansive soils in the Northeastern United States is relatively uncommon. Expansive soils in Western states generally have low soil moisture content, are comprised of highly expansive clay minerals and the houses typically utilize slab-on-grade construction. Conversely, soils in Amherst are generally moister, contain non-expansive clays, and houses have full basements. In both environments, non-uniform changes to the soil moisture content across the foundation footprint are a primary concern.
The confirmation of both expansive and compressible soils will have implications for new home construction in the region, as mandated in the New York State Residential Code. This study is a prime example of geologic investigations impacting the health and safety of New York State residents.
Brad Guay is Hydrologist/Technical Manager at the US Army Corps of Engineers at the Buffalo District. Brad received his PhD from the University of Arizona (2001) from the School of renewable Natural Resources, Watershed Resources, Program and Department of Hydrology and Water Resources, his Masters from SUNY Albany in Geography, and his Bachelors in Geology from the University of Maine. Brad has worked for several environmental firms as well as several state government organizations, notably the NYSDOH and NYSDEC.
Please RSVP as soon as possible as this meeting has a possibility of filling to capacity.
Michael C. Alfieri
BAPG Executive Vice-President