Level II scour analysis for Bridge 28 (BRNATH00660028) on Town Highway 66, crossing Locust Creek, Barnard, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure BRNATH00660028 on Town Highway 66 crossing the 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 21.5-mi² drainage area is in a predominantly rural basin. In the vicinity of the study site, the surface cover is pasture. In the study area, the Locust Creek has an incised, sinuous channel with a slope of approximately 0.01 ft/ft, an average channel top width of 47 ft and an average channel depth of 5 ft. The predominant channel bed materials are gravel and cobble with a median grain size (D₅₀) of 72.6 mm (0.238 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 22 and 29, 1994, respectively, indicated that the reach was stable. Additional Level I data was collected on 12/15/94 and was used to update the data shown in Appendix E. The Town Highway 66 crossing of the Locust Creek is a 41-ft-long, one-lane bridge consisting of a 39 ft steel stringer type bridge with a concrete deck (Vermont Agency of Transportation, written communication, August 24, 1994). The clear span is 36.8 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The upstream right wingwall is protected by stone fill. The channel is skewed approximately 10 degrees to the opening while the opening-skew-to-roadway is 0 degrees. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. This report provides the results of a detailed Level II analysis of scour potential at structure BRNATH00660028 on Town Highway 66 crossing the 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 21.5-mi2 drainage area is in a predominantly rural basin. In the vicinity of the study site, the surface cover is pasture. In the study area, the Locust Creek has an incised, sinuous channel with a slope of approximately 0.01 ft/ft, an average channel top width of 47 ft and an average channel depth of 5 ft. The predominant channel bed materials are gravel and cobble with a median grain size (D50) of 72.6 mm (0.238 ft). The geomorphic assessment at the time of the Level I and Level II site visit on September 22 and 29, 1994, respectively, indicated that the reach was stable. Additional Level I data was collected on 12/15/94 and was used to update the data shown in Appendix E. The Town Highway 66 crossing of the Locust Creek is a 41-ft-long, one-lane bridge consisting of a 39 ft steel stringer type bridge with a concrete deck (Vermont Agency of Transportation, written communication, August 24, 1994). The clear span is 36.8 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The upstream right wingwall is protected by stone fill. The channel is skewed approximately 10 degrees to the opening while the opening-skew-to-roadway is 0 degrees. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E.