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185 records · Page 11Linked to original sources
USGS1996

Level II scour analysis for Bridge 38 (RANDTH00640038) on Town Highway 64, crossing the Second Branch of the White River, Randolph, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure RANDTH00640038 on town highway 64 crossing the Second Branch of the White River, Randolph, 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 of central Vermont. The 46.5-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the The upstream left bank is forested, the upstream right bank is covered primarily by brush, the surface cover is pasture on the downstream left and row crops on the downstream right. In the study area, the Second Branch of the White River has an incised, sinuous channel with a slope of approximately 0.0015 ft/ft, an average channel top width of 71 ft and an average channel depth of 8 ft. The predominant channel bed material is gravel with a median grain size (D 50 ) of 32.0 mm (0.105 ft). The geomorphic assessment at the time of the Level I site visits on August 10, 1994 and December 5, 1994 indicated that the reach was laterally unstable. The town highway 64 crossing of the Second Branch of the White Riveris a 43-ft-long, one-lane covered bridge consisting of one 35-foot steel-beam span (Vermont Agency of Transportation, written communication, August 1, 1994). The bridge is supported by vertical, stone abutments with upstream wingwalls. The channel bends sharply at it’s approach to the bridge, however, at the bridge face, the channel is skewed approximately 0 degrees to the opening. The opening-skew-to-roadway is also 0 degrees. A scour hole 2 ft deeper than the mean thalweg depth was observed upstream of the bridge along the outside of the channel bend. Other scour problems at this site included undermining of the right abutment at it’s upstream and downstream ends. 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 for all modelled flows ranged from 1.7 to 2.6 ft. The worst-case contraction scour occurred at the 500-year discharge. Abutment scour ranged from 7.2 to 24.2 ft. The worst-case abutment scour also 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. 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↗
USGS1996

Level II scour analysis for Bridge 28 (HARDTH00300028) on Town Highway 30, crossing the Lamoille River, Hardwick, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure HARDTH00300028 on town highway 30 crossing the Lamoille River, Hardwick, 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 New England Upland section of the New England physiographic province in north-central Vermont. The 63.7-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover upstream and on the downstream right is primarily pasture with some row crops. Trees line the immediate channel banks. The left bank downstream surface cover is primarily brush. In the study area, the Lamoille River has an incised, sinuous channel with a slope of approximately 0.002 ft/ft, an average channel top width of 76 ft and an average bank height of 6 ft. The predominant channel bed materials are gravel and cobble with a median grain size (D 50 ) of 46.6 mm (0.153 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 25, 1995, indicated that the reach was laterally unstable. The site was revisited on August 21, 1995, after the August 5-6, 1995 flood on the Lamoille River. Findings from this follow-up visit are presented in Appendix G. The town highway 30 crossing of the Lamoille River is a 54-ft-long, one-lane bridge consisting of one 52-foot steel-beam span (Vermont Agency of Transportation, written communication, April 3, 1995). The bridge is supported by vertical, stone abutments with wingwalls. Scour, about one foot below the mean thalweg, exists along the right abutment and right upstream wingwall. Sheet piling has been driven around the right abutment and wingwalls and filled with concrete. The channel is skewed approximately 5 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. 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 for all modelled flows ranged from 1.9 to 2.5 ft. The worst-case contraction scour occurred at the 100-year discharge. Abutment scour ranged from 11.2 to 17.8 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. 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↗
USGS2010

A summary of information on the rust Puccinia psidii Winter (guava rust) with emphasis on means to prevent introduction of additional strains to Hawaii

The neotropical rust fungus Puccinia psidii ( P. psidii ) was originally described from the host common guava in its native Brazil but has been found since on hosts throughout the myrtle family (Myrtaceae), including a dramatic host jump to nonnative Eucalyptus plantations. Most rust fungi are able to live only on a very narrow range of host species. P. psidii is unusual both for having a broad host range and for the intensity of its damage to susceptible young growth. This rust first got a foothold in the United States in Florida more than three decades ago. The U.S. Department of Agriculture (USDA) has since considered it a nonactionable, nonreportable pest. Hawaii and Florida are the only two states with native species in the myrtle family. Over a period of 30 years, this rust has done little damage to any of the scattered native Myrtaceae in Florida, although the host range of the rust has gradually grown to about 30 mostly nonnative species in the family, apparently because of increasing genetic variety of the rust by repeated introductions. However, Florida’s native Myrtaceae are among the roughly 1,100 neotropical species that are largely resistant to P. psidii . The 3,000 species of non-neotropical Myrtaceae of the Pacific, Australia, Asia, and Africa are expected to prove much more vulnerable to P. psidii . Little is known about the genetics or genetic strains of P. psidii , although existing literature shows that there are numerous strains that have differential ability to infect suites of host plants. The rust was first recorded in the state of Hawaii on Oahu in April 2005 and quickly spread throughout the Hawaiian Islands. The main concern in Hawaii became the potential threat to ohia, Metrosideros polymorpha (Myrtaceae), the endemic forest tree species overwhelmingly important in Hawaii’s nature and culture. The potential ecological consequences of a virulent strain of rust on ohia forests are immense, due to its role as a foundation tree species and the diversity of niches it fills in Hawaii. A single genetic strain of the rust is established in Hawaii, apparently composed of a single genotype lacking sexual reproduction. P. psidii has been found statewide in Hawaii attacking Myrtaceae from near sea level to about 1,200 m elevation in areas with rainfall ranging from 750–5,000 mm. Five of eight native Myrtaceae and at least 15 nonnative species have been observed as hosts of P. psidii in Hawaii. The federally endangered Eugenia koolauensis (nioi) and the nonendangered indigenous species Eugenia reinwardtiana are severely damaged. The introduced (an Asian species) and invasive rose apple, Syzygium jambos , is severely affected at a landscape scale, with widespread crown dieback and many instances of complete tree death. In spite of billions of wind-dispersed rust spores produced from rose apple infestations during 2006 to 2008, adjacent ohia have been little affected to date by the rust strain in Hawaii. Within the elevation range of the rust, P. psidii is found on less than 5 percent of the ohia trees in the wild; on those ohia trees on which the rust is found, it is normally found on less than 5 percent of the leaves. The strain in Hawaii has not attacked many of the species known to be infected by the rust elsewhere, including common guava. On the basis of the very substantial genetic diversity of the much-studied, crop-damaging species of the genus Puccinia , there is good reason to believe that there are at minimum dozens and likely hundreds or thousands of genotypes of P. psidii , likely concentrated in the core range in Brazil but with potential for dispersal by globalization. Multiple genotypes are believed already present in the United States and certain to spread freely in the absence of restrictions. The U.S. Forest Service has initiated a major collaborative project in Brazil to investigate the genetics of susceptibility of Hawaii’s ohia to P. psidii , but initial results will likely not be available for several years. If just one more strain reaches Hawaii, the consequences could be dire for ohia, with each new genotype arriving having an unknown likelihood of increasing damage to ohia; possibilities for mutation and (or) genetic mixing, even with asexual strains, are apparently substantial, based on what is known about other Puccinia species. Investigations are needed to clarify rust-nioi relationships. However, it is likely that keeping out new strains of P. psidii may be important for long-term survival of nioi as well as for the health of ohia forest. The source of Hawaii’s initial invasion by P. psidii is uncertain but is strongly suspected to have been decorative foliage of species in the myrtle family from the mainland United States, most likely California, where there had been outbreaks of this rust on cultivated myrtle in 2005. In 2006–7, Maui’s Hawaii Department of Agriculture (HDOA) inspectors intercepted several P. psidii infected shipments of foliage myrtle, shipped from several California counties. Recognizing the huge threat of the rust to Hawaii’s one million acres of ohia forests, and consequently to Hawaii’s watersheds and biodiversity, Hawaii’s Board of Agriculture unanimously approved an interim rule in August 2007 banning importation of plants in the myrtle family from “infested areas,” specified as South America, Florida, and California. However, the interim rule has not been made permanent by HDOA, and the department has stated that it needs further information to formulate a long-term rule that imposes appropriate measures. Rust spores can survive for 2 to 3 months, and the pathogen can be transported to Hawaii on Myrtaceae from anywhere in the world through the United States mainland. There is much geographic reshuffling of flowers and foliage among the far-flung firms in the trade, especially for bouquet making. Because P. psidii is a nonactionable and nonreportable pest in the United States, foliage and flowers of the myrtle family can move freely into the country (usually but not necessarily always through the ports of Miami or Los Angeles), and from state to state. Currently, the State of Hawaii regulates incoming plant material in the family Myrtaceae by visual inspection. Inspection capacity and latent (asymptomatic) infections limit the ability to detect the rust. New molecular tests could improve detection efficiency, but the cost and the time required to process samples currently precludes their routine use in ports of entry. Interdiction, which has effectively kept coffee rust ( Hemileia vastatrix ) out of Hawaii for 120 years, offers the strongest protection for Hawaii’s native ecosystems from P. psidii . Interdiction of Myrtaceae from the continental United States could have the important supplementary benefit of preventing establishment in Hawaii of other very significant pests of multiple species of Myrtaceae that are already in the country, including: the Eugenia psyllid Trioza eugeniae (Hemiptera: Psyllidae); Chrysophtharta m-fuscum , the Eucalyptus tortoise beetle (Coleoptera: Chrysomelidae); Leptocybe invasa , the blue gum chalcid wasp (Hymenoptera: Chalcidae); and the fungal pathogens Mycosphaerella molleriana (Ascomycota: Mycosphaerelliaceae, crinkle leaf disease of Eucalyptus spp.) and Neofusicoccum parvum (Ascomycota: Botryosphaeriaceae), currently causing serious damage to Syzygium paniculatum in south Florida nurseries. Each of these pests would be likely to cause very significant damage to native and (or) cultivated Myrtaceae in Hawaii. Each of these pests is a prime candidate for transport by the foliage and (or) nursery stock pathways from Florida and California into Hawaii. Hawaii Department of Agriculture has a clear mandate to protect Hawaii’s natural environment, forestry and cultivated Myrtaceae. Principles of the World Trade Organization’s Treaty on Sanitary and Phytosanitary Measures and the International Plant Protection Convention are consistent with the right of Hawaii to take action. The current threat of P. psidii and the other five serious threats to Myrtaceae are primarily posed by the importation of infected plants from the continental United States; however, that may change in the future. If Hawaii were to decide to take a stand (through State regulation) to protect its native and introduced Myrtaceae, there is a possibility that USDA would consider Federal regulation of Myrtaceae from foreign countries.

Hawaii↗
USGS2017

Mineral-deposit model for lithium-cesium-tantalum pegmatites

Lithium-cesium-tantalum (LCT) pegmatites comprise a compositionally defined subset of granitic pegmatites. The major minerals are quartz, potassium feldspar, albite, and muscovite; typical accessory minerals include biotite, garnet, tourmaline, and apatite. The principal lithium ore minerals are spodumene, petalite, and lepidolite; cesium mostly comes from pollucite; and tantalum mostly comes from columbite-tantalite. Tin ore as cassiterite and beryllium ore as beryl also occur in LCT pegmatites, as do a number of gemstones and high-value museum specimens of rare minerals. Individual crystals in LCT pegmatites can be enormous: the largest spodumene was 14 meters long, the largest beryl was 18 meters long, and the largest potassium feldspar was 49 meters long. Lithium-cesium-tantalum pegmatites account for about one-fourth of the world’s lithium production, most of the tantalum production, and all of the cesium production. Giant deposits include Tanco in Canada, Greenbushes in Australia, and Bikita in Zimbabwe. The largest lithium pegmatite in the United States, at King’s Mountain, North Carolina, is no longer being mined although large reserves of lithium remain. Depending on size and attitude of the pegmatite, a variety of mining techniques are used, including artisanal surface mining, open-pit surface mining, small underground workings, and large underground operations using room-and-pillar design. In favorable circumstances, what would otherwise be gangue minerals (quartz, potassium feldspar, albite, and muscovite) can be mined along with lithium and (or) tantalum as coproducts. Most LCT pegmatites are hosted in metamorphosed supracrustal rocks in the upper greenschist to lower amphibolite facies. Lithium-cesium-tantalum pegmatite intrusions generally are emplaced late during orogeny, with emplacement being controlled by pre-existing structures. Typically, they crop out near evolved, peraluminous granites and leucogranites from which they are inferred to be derived by fractional crystallization. In cases where a parental granite pluton is not exposed, one is inferred to lie at depth. Lithium-cesium-tantalum LCT pegmatite melts are enriched in fluxing components including H2O, F, P, and B, which depress the solidus temperature, lower the density, and increase rates of ionic diffusion. This, in turn, enables pegmatites to form thin dikes and massive crystals despite having a felsic composition and temperatures that are significantly lower than ordinary granitic melts. Lithium-cesium-tantalum pegmatites crystallized at remarkably low temperatures (about 350–550 °C) in a remarkably short time (days to years). Lithium-cesium-tantalum pegmatites form in orogenic hinterlands as products of plate convergence. Most formed during collisional orogeny (for example, Kings Mountain district, North Carolina). Specific causes of LCT pegmatite-related magmatism could include: ordinary arc processes; over thickening of continental crust during collision or subduction; slab breakoff during or after collision; slab delamination before, during, or after collision; and late collisional extensional collapse and consequent decompression melting. Lithium-cesium-tantalum pegmatite deposits are present in all continents including Antarctica and in rocks spanning 3 billion years of Earth history. The global age distribution of LCT pegmatites is similar to those of common pegmatites, orogenic granites, and detrital zircons. Peak times of LCT pegmatite genesis at about 2640, 1800, 960, 485, and 310 Ma (million years before present) correspond to times of collisional orogeny and supercontinent assembly. Between these pulses were long intervals when few or no LCT pegmatites formed. These minima overlap with supercontinent tenures at ca. 2450–2225, 1625–1000, 875–725, and 250–200 Ma. Exploration and assessment for LCT pegmatites are guided by a number of observations. In frontier areas where exploration has been minimal at best, the key first-order criteria are an orogenic hinterland setting, appropriate regional metamorphic grades, and the presence of evolved granites and common granitic pegmatites. New LCT pegmatites are most likely to be found near known deposits. Pegmatites tend to show a regional mineralogical and geochemical zoning pattern with respect to the inferred parental granite, with the greatest enrichment in the more distal pegmatites. Mineral-chemical trends in common pegmatites that can point toward an evolved LCT pegmatite include: increasing rubidium in potassium feldspar, increasing lithium in white mica, increasing manganese in garnet, and increasing tantalum and manganese in columbite-tantalite. Most LCT pegmatite bodies show a distinctive internal zonation featuring four zones: border, wall, intermediate (where lithium, cesium, and tantalum are generally concentrated), and core. This zonation is expressed both in cross section and map view; thus, what may appear to be a common pegmatite may instead be the edge of a mineralized body. Neither lithium-cesium-tantalum pegmatites nor their parental granites are likely to cause serious environmental concerns. Soils and country rock surrounding a LCT pegmatite, as well as waste from mining operations, may be enriched in characteristic elements relative to global average soil and bedrock values. These elements may include lithium, cesium, tantalum, beryllium, boron, fluorine, phosphorus, manganese, gallium, rubidium, niobium, tin, and hafnium. Among this suite of elements, however, the only ones that might present a concern for environmental health are beryllium and fluorine, which are included in the U.S. Environmental Protection Agency drinking-water regulations with maximum contaminant levels of 4 micrograms per liter and 4 milligrams per liter, respectively.

Scientific Investigations Report↗
USGS2006

Simulation of nutrient and sediment concentrations and loads in the Delaware inland bays watershed: Extension of the hydrologic and water-quality model to ungaged segments

Rapid population increases, agriculture, and industrial practices have been identified as important sources of excessive nutrients and sediments in the Delaware Inland Bays watershed. The amount and effect of excessive nutrients and sediments in the Inland Bays watershed have been well documented by the Delaware Geological Survey, the Delaware Department of Natural Resources and Environmental Control, the U.S. Environmental Protection Agency’s National Estuary Program, the Delaware Center for Inland Bays, the University of Delaware, and other agencies. This documentation and data previously were used to develop a hydrologic and water-quality model of the Delaware Inland Bays watershed to simulate nutrients and sediment concentrations and loads, and to calibrate the model by comparing concentrations and streamflow data at six stations in the watershed over a limited period of time (October 1998 through April 2000). Although the model predictions of nutrient and sediment concentrations for the calibrated segments were fairly accurate, the predictions for the 28 ungaged segments located near tidal areas, where stream data were not available, were above the range of values measured in the area. The cooperative study established in 2000 by the Delaware Department of Natural Resources and Environmental Control, the Delaware Geological Survey, and the U.S. Geological Survey was extended to evaluate the model predictions in ungaged segments and to ensure that the model, developed as a planning and management tool, could accurately predict nutrient and sediment concentrations within the measured range of values in the area. The evaluation of the predictions was limited to the period of calibration (1999) of the 2003 model. To develop estimates on ungaged watersheds, parameter values from calibrated segments are transferred to the ungaged segments; however, accurate predictions are unlikely where parameter transference is subject to error. The unexpected nutrient and sediment concentrations simulated with the 2003 model were likely the result of inappropriate criteria for the transference of parameter values. From a model-simulation perspective, it is a common practice to transfer parameter values based on the similarity of soils or the similarity of land-use proportions between segments. For the Inland Bays model, the similarity of soils between segments was used as the basis to transfer parameter values. An alternative approach, which is documented in this report, is based on the similarity of the spatial distribution of the land use between segments and the similarity of land-use proportions, as these can be important factors for the transference of parameter values in lumped models. Previous work determined that the difference in the variation of runoff due to various spatial distributions of land use within a watershed can cause substantialloss of accuracy in the model predictions. The incorporation of the spatial distribution of land use to transfer parameter values from calibrated to uncalibrated segments provided more consistent and rational predictions of flow, especially during the summer, and consequently, predictions of lower nutrient concentrations during the same period. For the segments where the similarity of spatial distribution of land use was not clearly established with a calibrated segment, the similarity of the location of the most impervious areas was also used as a criterion for the transference of parameter values. The model predictions from the 28 ungaged segments were verified through comparison with measured in-stream concentrations from local and nearby streams provided by the Delaware Department of Natural Resources and Environmental Control. Model results indicated that the predicted edge-of-stream total suspended solids loads in the Inland Bays watershed were low in comparison to loads reported for the Eastern Shore of Maryland from the Chesapeake Bay watershed model. The flatness of the terrain and the low annual surface runoff are important factors in determining the amount of detached sediment from the land that is delivered to streams. The highest predicted total suspended solids loads were found in the southern part of the watershed, where the values are associated with high total streamflow and a high surface-runoff component, and related to soil and aquifer permeability and land use. Nutrient loads from model segments in the southern part of the Inland Bays watershed were also higher than those measured in the northern part of the basin, due to relatively high runoff and the substantial amount of available organic fertilizer (animal waste) that results in over-application of organic fertilizer to crops. Time series of simulated hourly concentrations indicated a seasonal pattern in the simulated base flow for total nitrogen, with the lowest values occurring during the summer and the highest values during the winter months. Total phosphorus and total-suspended-solids concentrations were less seasonal and were more storm-dependent; in general, base-flow concentrations of total phosphorus and total suspended solids were low. During storm events, the total nitrogen concentrations tended to be diluted and total phosphorus concentrations tended to rise sharply. Nitrogen was transported mainly in the aqueous phase and largely through ground water, whereas phosphorus was strongly associated with sediment, which washes off during rainfall events.

Delaware↗