This report provides the results of a detailed Level II analysis of scour potential at structure
BRNATH00290034 on Town Highway 29 crossing Locust Creek, Barnard, Vermont
(figures 1-8). A Level II study is a basic engineering analysis of the site, including a
quantitative analysis of stream stability and scour (U.S. Department of Transportation,
1993). Results of a Level I scour investigation also are included in Appendix E of this
report. A Level I investigation provides a qualitative geomorphic characterization of the
study site. Information on the bridge, gleaned from Vermont Agency of Transportation
(VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is
found in Appendix D.
The site is in the Green Mountain section of the New England physiographic province in
central Vermont. The 11.5-mi2
drainage area is in a predominantly rural and forested basin.
In the vicinity of the study site, the surface cover is forest, except for pasture on the
downstream right overbank.
In the study area, Locust Creek has an incised, generally straight channel with a slope of
approximately 0.03 ft/ft, an average channel top width of 64 ft and an average channel
depth of 7 ft. The predominant channel bed materials are gravel and cobble with a median
grain size (D50) of 89.3 mm (0.293 ft). The geomorphic assessment at the time of the Level
I and Level II site visit on October 13, 1994 and December 16, 1994, indicated that the
reach was stable.
The Town Highway 29 crossing of Locust Creek is a 37-ft-long, one-lane bridge consisting
of one 32-foot concrete span (Vermont Agency of Transportation, written communication,
August 23, 1994). The bridge is supported by vertical, concrete abutments with wingwalls.
The channel is skewed approximately 25 degrees to the opening while the opening-skew-to-roadway is 25 degrees.
There was no observable scour protection measure at the site. Additional details describing
conditions at the site are included in the Level II Summary and Appendices D and E.
