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At least 37 records · Page 2Linked to original sources
USGS2007

Revisiting the cape cod bacteria injection experiment using a stochastic modeling approach

Bromide and resting-cell bacteria tracer tests conducted in a sandy aquifer at the U.S. Geological Survey Cape Cod site in 1987 were reinterpreted using a three-dimensional stochastic approach. Bacteria transport was coupled to colloid filtration theory through functional dependence of local-scale colloid transport parameters upon hydraulic conductivity and seepage velocity in a stochastic advection - dispersion/attachment - detachment model. Geostatistical information on the hydraulic conductivity (K) field that was unavailable at the time of the original test was utilized as input. Using geostatistical parameters, a groundwater flow and particle-tracking model of conservative solute transport was calibrated to the bromide-tracer breakthrough data. An optimization routine was employed over 100 realizations to adjust the mean and variance ofthe natural-logarithm of hydraulic conductivity (InK) field to achieve best fit of a simulated, average bromide breakthrough curve. A stochastic particle-tracking model for the bacteria was run without adjustments to the local-scale colloid transport parameters. Good predictions of mean bacteria breakthrough were achieved using several approaches for modeling components of the system. Simulations incorporating the recent Tufenkji and Elimelech (Environ. Sci. Technol. 2004, 38, 529-536) correlation equation for estimating single collector efficiency were compared to those using the older Rajagopalan and Tien (AIChE J. 1976, 22, 523-533) model. Both appeared to work equally well at predicting mean bacteria breakthrough using a constant mean bacteria diameter for this set of field conditions. Simulations using a distribution of bacterial cell diameters available from original field notes yielded a slight improvement in the model and data agreement compared to simulations using an average bacterial diameter. The stochastic approach based on estimates of local-scale parameters for the bacteria-transport process reasonably captured the mean bacteria transport behavior and calculated an envelope of uncertainty that bracketed the observations in most simulation cases.

Massachusetts↗
USGS1965

Vigil Network sites: A sample of data for permanent filing

The Vigil Network consists of places where observations are made through time to record changes in landscape features over a long period. Resurveys will usually be made once each year or every few years and the period of observation, hopefully, will extend through and beyond the International Hydrological Decade. Vigil Network sites will usually be chosen to represent some typical feature of a given landscape. In the example shown here, the feature is a small ephemeral channel in a basin of moderate relief underlain by silty sandstone typical of the surrounding area. Vigil sites are not protected from man's influence and indeed may be selected because of the possible or portending cultural influences. In this respect they differ from the Bench Mark Network whose purpose is to make precise observations of hydrologic factors in areas uninfluenced by and protected from man's use. The factors which might be observed are many and varied. A few might be mentioned here, others are explained at length elsewhere (Miller and Leopold, 1963; Leopold, 1962). Streamchannel position, form, depth, and profile; vegetation in form of transects or quadrats; soil movement on slopes; rock movement on slopes or in channels. These and many more would yield valuable information on changes with time. To assure permanence of initial field observations, including reference points, bench marks, and cross sections, brief descriptions, maps, and initial data should be filed identically in designated repositories where the data will be made available for inspection by any interested scientist. It is recommended that the designation of two such locations where records of the type here attached will be filed be taken up by the Coordinating Council of the International Hydrological Decade. In designating such repositories it should be recognized that there is no need for elaborate indexing. The main requirement is merely the maintenance of a simple file where the data are stored and can be inspected or copied by any scientist. There need be no special provision for lending or reproduction services. The present document is an example showing what data, maps, and descriptions should be included in those permanent files at the two repositories. The material in these repositories should be sufficient to permit someone in the indefinite future to find and remeasure the same features described now. Thus the scientific value of the original surveys increases with time, - provided that the descriptions are sufficient to allow a person to find with assurance the original feature in the field. It must be visualized that a permanent repository must economize in space. Thus, as the example here shows, the filed material is not all of the original field notes but a summary, brief but descriptive.

International Association of Scientific Hydrology ↗
USGS1981

Marine turtles of the Galapagos Islands and adjacent areas of the eastern Pacific on the basis of observations made by J.R. Slevin 1905-1906

The field notes of J. R. Slevin written during the expedition of the California Academy of Sciences to the Galapagos Islands in 1905-1096 contain previously unavailable data on the marine turtles of the eastern Pacific. 'Land basking' by green turtles in Galapagos was predominately, if not exclusively, a female behavior. These terrestrial emergences were not concentrated in the major reproductive season of Galapagos turtles. Female Chelonia were also collected on shore during daylight hours on Socorro Island southwest of Baja California, Mexico. Chelonia, green turtles, were observed to feed on seaweed, the leaves and shoots of mangrove trees, and the leaves of another unidentified shoreline shrub. Comparative data on the gonads of dark and yellow turtles indicated that the latter did not breed in Galapagos during Slevin's stay. Lepidochelys olivacea, the olive ridley, was recorded in Galapagos waters and fed on fish eggs

Journal of Herpetology↗
USGS1951

Vegetation of Southwestern watersheds in the nineteenth century

The recollections of many old-timers who tell of grass “stirrup high” have given rise to the idea that vegetation in the Southwest was uniformly better in the middle of the last century than it is at present. The change is usually attributed to overgrazing, which timed if it did not cause extensive gullying of the alluvial valleys, I lowering the water table and decreasing the availability of water for plant use. This idea of an originally verdant vegetation, deteriorated as a result of man’s activities, has led to overoptimism concerning the possible results of reduced grazing. Obviously, any decrease in grazing pressure is a step in the right direction, but it is no exaggeration to say that recovery fo vegetation density on depleted ranges, even after protection for years, has been spotty and, in many places, disappointing. We may have allowed ourselves to be deluded by hopes of ‘restoring’ over large areas a level of vegetation density that was originally attained only in selected localities. This conclusion is supported by the published diaries and field notes of members of early American exploring parties. They show that in certain places, particularly in south-central Arizona where grass is now meager, the alluvial valleys formerly supported large expanses of grassland. However, there were also many areas, even alluvial valleys, where grass was so poor that forage for a string of horses could hardly be obtained. Other areas, such as the Rio Puerco Valley, supported good grass in some places but only scattered shrubs, furnishing poor forage, in others, though until well past the middle of the nineteenth century extensive grazing had been prevented by frequent raids of hostile Indians.

Southwest↗
USGS1985

Recent Red-shouldered Hawk range expansion north into Oregon including first specimen record

In this paper we review 46 Red-shouldered Hawk ( Buteo lineatus ) observation records from Oregon between 1971 and 1983. The literature contained only two records prior to 1971: Johnson's (1880) record without a specific date or locality from the Willamette Valley of western Oregon, and Bendire's (1892) two nests located in 1878 near Camp Harney in eastern Oregon. Gabrielson and Jewett (1940) placed the species on the Oregon hypothetical list because they doubted the validity of the previous identifications. However, Browning (1973) measured the eggs collected by Bendire, reviewed his field notes, and concluded that there was ample evidence the species had occurred in Oregon despite the absence of records for nearly 100 years.

Oregon↗
USGS1970

Records of the brambling in North America

A Brambling, Fringella montifringella , was seen regularly in Portland, Oregon, from 22 November 1967 to 3 April 1968 and photographed by many people. First discovered at a feeder in the northeast section of the city by Jeff Gilligan and Ron Klein, from January on it was a daily visitor to the feeder of the Albert H. Praels in the same part of Portland. The bird, judged by plumage to be a male, fed regularly with House Finches ( Carpodacus mexicanus ) on sunflower seeds. The occurrence of this individual in Portland was recorded in Audubon Field Notes (22: 471, 1968) without detail.

The Auk↗
USGS1878

Bulletin of the United States Geological and Geographical Survey of the Territories: Volume IV, Number 3

Table of Contents ART. XXV.----Field-notes on Birds observed in Dakota and Montana along the Forty-ninth Parallel during the seasons of 1873 and 1874. By Dr. Elliott Coues, U.S.A., late Surgeon and Naturalist U.S. Northern Boundary Commission.....545-662 ART. XXVI.----Notes on a Collection of Fishes from the Rio Grande, at Brownsville, Texas-Continued. By D.S. Jordan, M.D......663-668 ART. XXVII.---Preliminary Studies on the North American Pyralidae. I. By A.R. Grote..... 669-706 ART. XXVIII.--Paleontological Papers No.6: Descriptions of New Species of Invertebrate Fossils from the Laramie Group. By C.A. White, M.D......707-720 ART. XXIX.----Paleontological Papers No.7: On the Distribution of Molluscan Species in the Laramie Group. By C. A. White, M.D......721-724 ART. XXX.-----On some Dark Shale recently discovered below the Devonian Limestones, at Independence, Iowa\; with a Notice of its Fossils and Description of New Species. By S. Calvin, Professor of Geology, State University of Iowa.....725-730 ART. XXXI.----On the Mineralogy of Nevada. By W.J. Hoffman, M.D......731-745

Report↗
USGS2015

Chemicals of emerging concern in water and bottom sediment in the Great Lakes Basin, 2012: collection methods, analytical methods, quality assurance, and study data

In synoptic surveys of surface-water quality across the United States, a large group of organic chemicals associated with agricultural, household, and industrial waste have been detected. These chemicals are referred to collectively as chemicals of emerging concern (CECs) and include prescription drugs and antibiotics, over-the-counter medications, reproductive hormones, personal-care products, detergent metabolites, and flame retardants. The U.S. Geological Survey (USGS) collaborated with the U.S. Fish and Wildlife Service and the U.S. Environmental Protection Agency on a study to identify the presence of CECs in water and bottom-sediment samples collected during 2012 at 66 sites throughout the Great Lakes Basin. The 2012 effort is part of a long-term study that was initiated in 2010. The purposes of this report are to document the collection and analytical methods, provide the quality-assurance data and analyses, and provide the water and bottom-sediment data for this study of CECs in the Great Lakes Basin for 2012. A previous report documents data collected during 2010 and 2011. The methods used for chemical analyses were identical between the 2010–11 and 2012 studies, with the exception that a method to determine nontarget chemicals was used during 2010–11. The data from this study are published as a USGS Data Series Report to ensure adequate documentation of the original methods and provide a citable source for study data. This report contains no interpretations of the study data. The chemical data are as reported by the laboratory and have not been censored or adjusted unless otherwise noted. Field measurements were recorded and samples were collected in April and May and in September 2012, by U.S. Geological Survey, U.S. Fish and Wildlife Service, and U.S. Environmental Protection Agency personnel. Study sites included tributaries to the Great Lakes located near Duluth, Minnesota; King, Wisconsin; Green Bay, Wis.; Detroit, Michigan; Monroe, Mich.; Toledo, Ohio, and Rochester, New York. Water and bottom-sediment samples were analyzed at the USGS National Water Quality Laboratory in Denver, Colorado, for a broad suite of CECs. During this 2012 study, 140 environmental and 8 field duplicate samples of surface water and wastewater effluent, 1 field blank water sample, and 5 field spike water samples were collected or prepared. Water samples were analyzed at the USGS National Water Quality Laboratory using laboratory schedule 4433 for wastewater indicators, research method 8244 for pharmaceuticals, and laboratory schedule 4434 for steroid hormones, sterols, and bisphenol A. For wastewater indicators in unfiltered water, 61 of the 68 chemicals analyzed using laboratory schedule 4433 had detectable concentrations ranging from 0.002 to 64.4 micrograms per liter. Thirty-eight of the 48 chemicals analyzed using research method 8244 for pharmaceuticals in unfiltered water had detectable concentrations ranging from 0.002 to 3.32 micrograms per liter. Twelve of the 20 chemicals analyzed using laboratory schedule 4434 for steroid hormones, sterols, and bisphenol A in unfiltered water had detectable concentrations ranging from 0.43 to 120,000 nanograms per liter. During this study, 53 environmental samples, 4 field duplicate samples, and 8 field spike samples of bottom sediment and laboratory matrix-spike samples were analyzed for a wide variety of CECs at the USGS National Water Quality Laboratory using laboratory schedule 5433 for wastewater indicators; research method 6434 for steroid hormones, sterols, and bisphenol A; and research method 9008 for human-use pharmaceuticals and antidepressants. Forty of the 57 chemicals analyzed using laboratory schedule 5433 had detectable concentrations ranging from 1 to 49,000 micrograms per kilogram. Fourteen of the 20 chemicals analyzed using research method 6434 had detectable concentrations ranging from 0.04 to 24,940 nanograms per gram. Ten of the 20 chemicals analyzed using research method 9008 had detectable concentrations ranging from 0.59 to 197.5 micrograms per kilogram. Five of the 11 chemicals analyzed using research method 9008 had detectable concentrations ranging from 1.16 to 25.0 micrograms per kilogram.

Great Lakes Basin↗
USGS2011

The Alaska Geochemical Database: v. 1.0 - Geologic Materials

What is the AGDB?: The Alaska Geochemical Database (AGDB) is a new, comprehensive compilation of geologic, spatial, descriptive, mineralogical, and analytical geochemical data for samples collected in Alaska and surrounding waters by the U.S. Geological Survey (USGS) from 1962 to 2009. Data for geologic materials (rocks, minerals and mineral separates, soils, lake sediments, bulk stream sediments, and a variety of heavy-mineral concentrates) will be released as a two-sided DVD (USGS Digital Data Series DS 637 v. 1.0) in October of 2011. Future data releases will include water, organic and leachate samples. The AGDB contains all Alaskan data from USGS legacy databases (for example, the RASS and PLUTO systems), and all results produced by USGS in-house and contract chemistry laboratories through December 2009. The database includes geochemical data resulting from the reanalysis of archived materials, such as those from the Alaska Mineral Resource Assessment (AMRAP) and National Uranium Resource Evaluation (NURE) programs, for additional elements and by newer methods. Reanalyses include samples collected statewide as part of the National Geochemical Survey, and samples from a project across the Alaska Range (data released in 2010). The AGDB also contains data for geologic materials from Alaska submitted by USGS researchers to non-USGS and non-contract labs, and a variety of other Alaskan geologic materials samples. Quality Control: Data in the AGDB have undergone extensive quality control screening including searching field notes and maps for accurate location information, verifying media and sample type, linking analytical data to geologic parameters recorded by the submitter, and documenting sample preparation and analytical methods. Data Files The AGDB v. 1.0 two-sided DVD includes: * a 4.3 GB Microsoft Access® 2007 relational database (as two linked .mdb files); * the same database in Microsoft Access® 2003; * Microsoft Excel® spreadsheet tables (.xls files) and ASCII text files that display the results of common queries to the database (for example, Ag-Cr values for concentrate samples; rock samples by quadrangle); * references for analytical methods; * references to published data; and * metadata in three file formats. Data Availability: * The Alaska Geochemical Database will be available in a searchable, spatially referenced, online format at http://mrdata.usgs.gov/; estimated availability early 2012. * A 2012 update (AGDB v. 2.0) will include water, organic, leachate, and miscellaneous sample media. For More Information: On sample media or analytical methods: http://minerals.cr.usgs.gov/projects/analytical_chem/references.html Text prepared by Jeanine M. Schmidt and Matt Granitto Figure prepared by Nora Shew; Layout by Jeanine Schmidt Artwork on page 1 by Daniel Granitto (used by permission) The USGS Mineral Resources Program is the sole Federal provider of research and information on nonfuel mineral resources.

Fact Sheet↗
USGS2014

Noble gas isotopes in mineral springs within the Cascadia Forearc, Washington and Oregon

This U.S. Geological Survey report presents laboratory analyses along with field notes for a pilot study to document the relative abundance of noble gases in mineral springs within the Cascadia forearc of Washington and Oregon. Estimates of the depth to the underlying Juan de Fuca oceanic plate beneath the sample sites are derived from the McCrory and others (2012) slab model. Some of these springs have been previously sampled for chemical analyses (Mariner and others, 2006), but none currently have publicly available noble gas data. Helium isotope values as well as the noble gas values and ratios presented below will be used to determine the sources and mixing history of these mineral waters.

Oregon;Washington↗
USGS2016

QRev—Software for computation and quality assurance of acoustic doppler current profiler moving-boat streamflow measurements—User’s manual for version 2.8

The software program, QRev computes the discharge from moving-boat acoustic Doppler current profiler measurements using data collected with any of the Teledyne RD Instrument or SonTek bottom tracking acoustic Doppler current profilers. The computation of discharge is independent of the manufacturer of the acoustic Doppler current profiler because QRev applies consistent algorithms independent of the data source. In addition, QRev automates filtering and quality checking of the collected data and provides feedback to the user of potential quality issues with the measurement. Various statistics and characteristics of the measurement, in addition to a simple uncertainty assessment are provided to the user to assist them in properly rating the measurement. QRev saves an extensible markup language file that can be imported into databases or electronic field notes software. The user interacts with QRev through a tablet-friendly graphical user interface. This report is the manual for version 2.8 of QRev.

Open-File Report↗
USGS2016

QRev—Software for computation and quality assurance of acoustic doppler current profiler moving-boat streamflow measurements—Technical manual for version 2.8

The software program, QRev applies common and consistent computational algorithms combined with automated filtering and quality assessment of the data to improve the quality and efficiency of streamflow measurements and helps ensure that U.S. Geological Survey streamflow measurements are consistent, accurate, and independent of the manufacturer of the instrument used to make the measurement. Software from different manufacturers uses different algorithms for various aspects of the data processing and discharge computation. The algorithms used by QRev to filter data, interpolate data, and compute discharge are documented and compared to the algorithms used in the manufacturers’ software. QRev applies consistent algorithms and creates a data structure that is independent of the data source. QRev saves an extensible markup language (XML) file that can be imported into databases or electronic field notes software. This report is the technical manual for version 2.8 of QRev.

Open-File Report↗
USGS2016

Preliminary geologic mapping of Cretaceous and Tertiary formations in the eastern part of the Little Snake River coal field, Carbon County, Wyoming

In the 1970s and 1980s, C.S. Venable Barclay conducted geologic mapping of areas primarily underlain by Cretaceous coals in the eastern part of the Little Snake River coal field (LSR) in Carbon County, southwest Wyoming. With some exceptions, most of the mapping data were never published. Subsequently, after his retirement from the U.S. Geological Survey (USGS), his field maps and field notebooks were archived in the USGS Field Records. Due to a pending USGS coal assessment of the Little Snake River coal field area and planned geological mapping to be conducted by the Wyoming State Geological Survey, Barclay’s mapping data needed to be published to support these efforts. Subsequently, geologic maps were scanned and georeferenced into a geographic information system, and project and field notes were scanned into Portable Document Format (PDF) files. Data for seventeen 7½-minute quadrangles are presented in this report. This publication is solely intended to compile the mapping data as it was last worked on by Barclay and provides no interpretation or modification of his work.

Wyoming↗
USGS2017

Noble gas isotopes in mineral springs and wells within the Cascadia forearc, Washington, Oregon, and California

Introduction This U.S. Geological Survey report presents laboratory analyses along with field notes for an exploratory study to document the relative abundance of noble gases in mineral springs and water wells within the Cascadia forearc of Washington, Oregon, and California (fig. 1). This report describes 14 samples collected in 2014 and 2015 and complements a previous report that describes 9 samples collected in 2012 and 2013 (McCrory and others, 2014b). Estimates of the depth to the underlying Juan de Fuca oceanic plate beneath sample sites are derived from the McCrory and others (2012) slab model. Some of the springs have been previously sampled for chemical analyses (Mariner and others, 2006), but none of the springs or wells currently has publicly available noble gas data. The helium and neon isotope values and ratios presented below are used to determine the sources and mixing history of these mineral and well waters (for example, McCrory and others, 2016).

California, Oregon, Washington↗
USGS1971

Preliminary tectonic map of the Arabian Peninsula

In 1963, in response to a request from the Ministry of Petroleum and Mineral Resources, the Saudi Arabian Government and the U. S. Geological Survey, U. S. Department of the Interior, with the approval of the U. S. Department of State, undertook a joint and cooperative effort to map and evaluate the mineral potential of central and western Saudi Arabia. The results of this program are being released in USGS open files in the United States and are also available in the Library of the Ministry of Petroleum and Mineral Resources. Also on open file in that office is a large amount of material, in the form of unpublished manuscripts, maps, field notes, drill logs, annotated aerial photographs, etc., that has resulted from other previous geologic work by Saudi Arabian government agencies. The Government of Saudi Arabia makes this information available to interested persons, and has set up a liberal mining code which is included in "Mineral Resources of Saudi Arabia, a Guide for Investment and Development," published in 1965 as Bulletin 1 of the Ministry of Petroleum and Mineral Resources, Directorate General of Mineral Resources, Jiddah, Saudi Arabia.

Open-File Report↗
USGS1972

Report of the field trip, February 24 to April 2, 1965 in part of the northeastern Hijaz quadrangle, Saudi Arabia

In 1963, in response to a request from the Ministry of Petroleum and Mineral Resources, the Saudi Arabian Government and the U. S. Geological Survey, U. S. Department of the Interior, with the approval of the U. S. Department of State undertook a joint and cooperative effort to map and evaluate the mineral potential of central and Saudi Arabia. The results of this program are being released in USGS open files in the United States and are also available in the Library of the Ministry of Petroleum and Mineral Resources. Also on open file in that office is a large amount of material, in the form of unpublished manuscripts, maps, field notes, drill logs, annotated aerial photographs, etc., that has resulted from other previous geologic work by Saudi Arabian government agencies. The Government of Saudi Arabia makes this information available to interested persons, and has set up a liberal mining coda which is included in "Mineral Resources of Saudi Arabia, a Guide for Investment and Development," published in 1965 as Bulletin 1 of the Ministry of Petroleum and Mineral Resources, Directorate General of Mineral Resources, Jiddah, Saudi Arabia.

Hijaz quadrangle↗
USGS1996

Water-level data for the industrial area northwest of Delaware City, Delaware, 1993-94

Water-level data for 171 wells and one surface-water site on Red Lion Creek in the industrial area northwest of Delaware City, Delaware, are presented for 1993 and 1994. Eight sets of synoptic ground- water-level measurements collected between April 1993 and September 1994, and locations and field notes for the 171 wells are presented. A hydrograph from December 19, 1993 through November 8, 1994 is presented for one surface-water site on Red Lion Creek in the industrial area. Hydrographs from October 15, 1993 through November 8, 1994 are presented for eight wells screened in the water- table aquifer. The U.S. Army Corps of Engineers collected the synoptic ground-water-level measurements. The U.S. Geological Survey collected the continuously recorded water-level data.

Open-File Report↗
USGS1997

Level II scour analysis for Bridge 7 (MORRTH00020007) on Town Highway 2 (FAS 239), crossing Ryder Brook, Morristown, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure MORRTH00020007 on Town Highway 2 crossing Ryder Brook, Morristown, 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 North-central Vermont. The 18.5-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is pasture and forest. In the study area, Ryder Brook generally is straight and incised with a slope of approximately 0.002 ft/ft, an average channel top width of 48 ft and an average channel depth of 3 ft. The channel bed is bedrock with pockets of sand and gravel in several locations through the reach. The gravel has a median grain size (D 50 ) of 17.7 mm (0.0581 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 16, 1996 indicated that the reach was stable. The Town Highway 2 crossing of Ryder Brook is a 84-ft-long, two-lane bridge consisting of one 84-foot steel-beam span (Vermont Agency of Transportation, written communication, January 31, 1996). The bridge is supported by vertical, concrete abutment walls with spill-through embankments. The channel is skewed approximately 10 degrees to the opening while the opening-skew-to-roadway is 15 degrees. The only scour protection measure at the site was type-3 stone fill (less than 48 inches diameter) on the spill-through embankments of each abutment. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows. Contraction scour predictions for all modelled flows at this site were zero. Abutment scour predictions ranged from 5.6 to 8.1 ft. The worst-case abutment scour occurred at the 500- year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. However, historical bridge records and field notes indicate the abutment footings may be set on bedrock. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗