Natural and Anthropogenic (Human-Made) Hexavalent Chromium, Cr(VI), in Groundwater near a Mapped Plume, Hinkley, California <p> <p> Professional Paper 1885 <p> <p> Prepared in cooperation with the Lahontan Regional Water Quality Control Board <p> By: John A. Izbicki <p> <p> https://doi.org/10.3133/pp1885 <p> <p> First posted April 25, 2023 <p> For additional information, contact: Director, dc_ca@usgs.gov <p> California Water Science Center https://ca.water.usgs.gov/ <p> U.S. Geological Survey https://usgs.gov/ <p> 6000 J Street, Placer Hall <p> Sacramento, California 95819 <p> <p> Abstract <p> <p> Between 1952 and 1964, hexavalent chromium, Cr(VI), was released into groundwater from the Pacific Gas and Electric Company (PG&E) Hinkley compressor station in the Mojave Desert 80 miles (mi) northeast of Los Angeles, California. Remediation began in 1992, and in 2010, site cleanup was projected to require between 10 and 95 years and was expected to cost between $36 and $176 million. A 2007 PG&E study estimated the natural Cr(VI) background in groundwater in Hinkley Valley to be 3.1 micrograms per liter (μg/L). This concentration was used for interim regulatory purposes by the Lahontan Regional Water Quality Control Board (RWQCB). In the fourth quarter (October–December) 2015, the regulatory Cr(VI) plume extended about 3.0 mi downgradient from the release location within the Hinkley compressor station, while groundwater having Cr(VI) concentrations greater than 3.1 μg/L was present more than 8 mi downgradient. Although rocks and minerals in the area are naturally low in chromium, alluvium eroded from the San Gabriel Mountains and transported to Hinkley Valley by the Mojave River, and locally small exposures of mafic rock, including hornblende diorite and basalt, may contribute Cr(VI) to groundwater. In response to limitations of the PG&E 2007 Cr(VI) background study’s methodology, uncertainty in the natural Cr(VI) background concentration, and an increase in the mapped extent of groundwater having Cr(VI) concentrations greater than the interim regulatory background of 3.1 μg/L, the Lahontan RWQCB concluded that the 2007 PG&E background Cr(VI) study should be updated. The purpose of the updated study is to estimate background Cr(VI) concentrations in groundwater within the upper aquifer upgradient, downgradient, near the margins, and within the footprint of the PG &E Cr (VI) plume in Hinkley, California. The scope of the study included eight tasks; results from those tasks are presented in the chapters within this professional paper. <p>

<p> Surficial geology and soils of the Elmira-Williamsport region, New York and Pennsylvania, with a section on forest regions and great soil groups <p> <p> Professional Paper 379 <p> By: Charles Storrow Denny, Walter Henry Lyford, and J. C. Goodlett <p> https://doi.org/10.3133/pp379 <p> <p> Abstract <p> <p> The Elmira-Williamsport region, lying south of the Finger Lakes in central New York and northern Pennsylvania, is part of the Appalachian Plateaus physiographic province. A small segment of the Valley and Ridge province is included near the south border. In 1953 and 1954, the authors, a geologist and a soil scientist, made a reconnaissance of about 5,000 square miles extending southward from the Finger Lakes, N.Y., to Williamsport, Pa., and eastward from Wellsboro, Pa., to Towanda, Pa. Glacial drift of Wisconsin age, covering the central and most of the northern parts of the region, belongs to the Olean substage of MacClintock and Apfel. This drift is thin and patchy, is composed of the relatively soft sandstones, siltstone, shales, and conglomerates of the plateaus, commonly has a low calcium carbonate content, and is deeply leached. Mantling its surface are extensive rubbly colluvial deposits. No conspicuous terminal moraine marks the relatively straight border of Olean drift. The Valley Heads moraine of Fairchild near the south ends of the Finger Lakes is composed of relatively thick drift containing a considerable amount of somewhat resistant sedimentary and crystalline rocks. Commonly this drift has a relatively high carbonate content and is leached to only shallow depths. The Valley Heads drift is younger than Olean, but its precise age is undetermined. The age of the Olean is perhaps between Sangamon and Farmdale, on the basis of, in part, a carbon-14 date from peat at Otto, N.Y. All differences in soil development on these two Wisconsin drifts are clearly related to the lithology of the parent material or the drainage, rather than to weathering differing in kind or in duration. The authors believe that the soils are relatively young, are in equilibrium with the present environment, and contain few, if any, features acquired during past weathering intervals. The effect of tree throw on soil profiles and the presence of soils on slopes clearly indicate that soils form rapidly. Sols Bruns Acides are the most extensive great soil group occurring throughout the region. Podzols and Gray-Brown Podzolic soils are also widespread, and on long, smooth slopes Low Humic-Gley soils are common. Organic soils are of small extent. South of the Wisconsin drift border, the surficial mantle consists chiefly of alluvial, colluvial, or residual deposits of Wisconsin or of Recent age, but there are many small isolated patches of older, strongly weathered materials of pre-Wisconsin age. Although such older materials are commonly overlain or mixed with less weathered mantle, the yellowish-red color, characteristic of the strongly weathered material, is generally not masked. Some of the older material is drift, presumed to be of Illionian age, that was probably strongly weathered to a considerable depth in Sangamon time and has been greatly eroded since the last interglacial period. No clear-cut exposure of Wisconsin drift resting on older drift or other strongly weathered mantle has been found. The old drift and the other strongly weathered materials apparently acquired their present red color in pre-Wisconsin time. Where exposed at the surface, such strongly weathered mantle is the parent material of modern Red-Yellow Podzolic soils. Sols Bruns Acides and Gray-Brown Podzolic soils, developed on slightly weathered parent materials, are found adjacent to these red soils. This suggests that these Red-Yellow Podzolic soils probably developed from strongly weathered parent materials. No buried soils were found nor were any soils recognized as relics from pre-Wisconsin time. Comparison of a map of the great soil groups with a map of the vegetation of the region, prepared by John C. Goodlett, does not reveal a close relation. Laboratory analyses of samples collected furnish data on textural, mineralogical, and chemical changes caused by weathering and soil formation. The results indicate that the amount of chemical weathering which the Wisconsin drift has undergone is slight. The Red-Yellow Podzolic soils on strongly weathered pre-Wisconsin drift have B2 horizons that have a finer texture than the A2 or C horizons. The parent materials of these soils seem to be strongly weathered because of the high chromas, reddish hues, friable condition of most rock fragments, relatively high kaolinite content, and presence of gibbsite in the clay fraction. Measurements at numerous localities show that the depth of leaching increases with decreasing carbonate content and is not a criterion of the age of the drift. Pebble counts of gravels also show that the depth of leaching of gravel is related to its limestone content. The location of the gravel deposits is probably due primarily to the presence of pebbles of resistant rock rather than to ice wastage involving abundant glacial melt water. The region is in the Susquehanna drainage basin except for its north fringe, which drains to Lake Ontario. Most of the region is a dissected plateau ranging in altitude from 700 to 2,500 feet and underlain by gently folded sedimentary rocks of Paleozoic age. Much of the region slopes moderately or steeply; the most extensive areas of gently sloping land are 011 the uplands. In the northern part are several straight and deep valleys the southern extension of the Finger Lakes basins separated by uplands with several low cuestas that face north. Similarly, some streams such as the Canisteo, Cohocton, and Chemung Rivers, and the part of the Susquehanna River that is in New York, trend at right angles to the Finger Lakes, flowing in valleys that parallel the regional strike of the bedrock. The Olean drift border is marked by a change from drift containing very few rounded or striated rock fragments to a mantle containing only angular rock fragments and traces of red, strongly weathered materials. A reconstruction of the surface of the ice sheet, at its maximum extent shows an inferred slope of its distal margin ranging from 100 to 500 feet per mile <p>

Hydrology and Water Quality of the Great Dismal Swamp, Virginia and North Carolina, and Implications for Hydrologic-Management Goals and Strategies <p> <p> Scientific Investigations Report 2020-5100 <p> <p> Prepared in cooperation with the U.S. Fish and Wildlife Service <p> By: Gary K. Speiran and Frederic C. Wurster <p> <p> https://doi.org/10.3133/sir20205100 <p> <p> First posted October 21, 2021 <p> <p> For additional information, contact: <p> Center Director, <p> dc_va@usgs.gov <p> Virginia and West Virginia Water Science Center <p> https://www.usgs.gov/centers/va-wv-water <p> U.S. Geological Survey <p> 1730 East Parham Road <p> Richmond, VA 23228 <p> <p> Abstract <p> <p> The Great Dismal Swamp is a peat wetland in the Coastal Plain of southeastern Virginia and northeastern North Carolina. Timber harvesting and the construction of ditches to drain the swamp and facilitate the harvesting are collectively implicated in changes that altered the wetland forests, caused subsidence and decomposition of the peat, and increased the risk of fire. In response to these changes, managers have implemented strategies to control water levels and rewet the swamp using a network of 64 adjustable-height, water-control structures on the ditches. Rewetting the swamp is intended to re-establish the original wetland-forest types, reduce the risk of fire, reduce subsidence and decomposition of the peat, enhance peat accretion, and reduce the risk of fire. Knowledge of responses of the swamp to hydrologic controls, however, is critical to developing and implementing effective management goals and strategies. Because the 2008 South One fire reemphasized the need for this knowledge, the U.S. Geological Survey in cooperation with the U.S. Fish and Wildlife Service began studies in 2009 to identify critical hydrologic controls and responses to these controls. <p> <p> These studies identified water sources, topography, the two-layered hydraulic characteristics of the peat, the absence of peat in some areas, the ditch and road network, water-control structures on the ditches, the Dismal Swamp Canal and associated infrastructure, and wetland forests as the primary hydrologic controls. Precipitation is the only water source across much of the swamp. The eastward flow of streams and groundwater from the Isle of Wight Plain, across the Suffolk scarp, and into the swamp are additional water sources to the western part of the swamp. Vertical differences in the hydraulic characteristics of the peat reflect an upper peat having a high hydraulic conductivity and specific yield overlying a lower peat and sand having lower hydraulic conductivity and specific yield. The upper peat forms the main aquifer for the storage, flow, and release of water from the swamp. Maintaining water in the upper peat is critical to water availability to the wetland forests because of these properties. <p> <p> Groundwater flows from the swamp into the ditches and the Dismal Swamp Canal where it discharges into nearby streams. Discharge typically is to the closest ditch except where a spoil-pile road that impedes flow intervenes between the swamp and the ditch. When groundwater levels in a ditch are about 2 feet lower than levels in the other three ditches surrounding a part of the swamp, however, most groundwater typically discharges to the ditch having the lower level. This occurs even if a spoil-pile road intervenes between the swamp and the ditch having the lower level. Flow to a single ditch shifts watershed boundaries and groundwater divides toward the ditches having higher water levels and demonstrates how flow and discharge are controlled by ditch water levels. Consequently, managing water levels based on these and other hydrologic controls and responses is critical to achieving management objectives. <p> <p> The chemistry of water across the swamp shows the effects of the peat. Dissolved organic carbon concentrations in the groundwater are among the highest reported globally, ranging from 55 to 195 milligrams per liter. The pH of groundwater and ditch water is commonly less than 4.0 standard units because of organic acids. A relation between the pH and specific conductance of groundwater and ditch water reflects water sources, flow paths, and the chemical evolution, as waters from the different sources mix and flow along the paths. <p>