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James E. Reddy

Publications and source records attributed to James E. Reddy.

31 records · Page 2Linked to original sources
USGS2013

Groundwater quality in western New York, 2011

Water samples collected from 16 production wells and 15 private residential wells in western New York from July through November 2011 were analyzed to characterize the groundwater quality. Fifteen of the wells were finished in sand and gravel aquifers, and 16 were finished in bedrock aquifers. Six of the 31 wells were sampled in a previous western New York study, which was conducted in 2006. Water samples from the 2011 study were analyzed for 147 physiochemical properties and constituents that included major ions, nutrients, trace elements, radionuclides, pesticides, volatile organic compounds (VOCs), and indicator bacteria. Results of the water-quality analyses are presented in tabular form for individual wells, and summary statistics for specific constituents are presented by aquifer type. The results are compared with Federal and New York State drinking-water standards, which typically are identical. The results indicate that groundwater generally is of acceptable quality, although at 30 of the 31 wells sampled, at least one of the following constituents was detected at a concentration that exceeded current or proposed Federal or New York State drinking-water standards: pH (two samples), sodium (eight samples), sulfate (three samples), total dissolved solids (nine samples), aluminum (two samples), arsenic (one sample), iron (ten samples), manganese (twelve samples), radon-222 (sixteen samples), benzene (one sample), and total coliform bacteria (nine samples). Existing drinking-water standards for color, chloride, fluoride, nitrate, nitrite, antimony, barium, beryllium, cadmium, chromium, copper, lead, mercury, selenium, silver, thallium, zinc, gross alpha radioactivity, uranium, fecal coliform, Escherichia coli, and heterotrophic bacteria were not exceeded in any of the samples collected. None of the pesticides analyzed exceeded existing drinking-water standards.

New York↗
USGS2012

Groundwater quality in the Upper Susquehanna River Basin, New York, 2009

Water samples were collected from 16 production wells and 14 private residential wells in the Upper Susquehanna River Basin from August through December 2009 and were analyzed to characterize the groundwater quality in the basin. Wells at 16 of the sites were completed in sand and gravel aquifers, and 14 were finished in bedrock aquifers. In 2004–2005, six of these wells were sampled in the first Upper Susquehanna River Basin study. Water samples from the 2009 study were analyzed for 10 physical properties and 137 constituents that included nutrients, organic carbon, major inorganic ions, trace elements, radionuclides, pesticides, volatile organic compounds, and 4 types of bacterial analyses. Results of the water-quality analyses are presented in tabular form for individual wells, and summary statistics for specific constituents are presented by aquifer type. The results are compared with Federal and New York State drinking-water standards, which typically are identical. The results indicate that groundwater genrally is of acceptable quality, although concentrations of some constituents exceeded at least one drinking-water standard at 28 of the 30 wells. These constituents include: pH, sodium, aluminum, manganese, iron, arsenic, radon-222, residue on evaporation, total and fecal coliform including Escherichia coli and heterotrophic plate count.

New York↗
USGS2012

Groundwater quality in the Genesee River Basin, New York, 2010

Water samples collected from eight production wells and eight private residential wells in the Genesee River Basin from September through December 2010 were analyzed to characterize the groundwater quality in the basin. Eight of the wells were completed in sand and gravel aquifers, and eight were finished in bedrock aquifers. Three of the 16 wells were sampled in the first Genesee River Basin study during 2005-2006. Water samples from the 2010 study were analyzed for 147 physiochemical properties and constituents that included major ions, nutrients, trace elements, radionuclides, pesticides, volatile organic compounds (VOCs), and indicator bacteria. Results of the water-quality analyses are presented in tabular form for individual wells, and summary statistics for specific constituents are presented by aquifer type. The results are compared with Federal and New York State drinking-water standards, which typically are identical. The results indicate that groundwater generally is of acceptable quality, although concentrations of the following constituents exceeded current or proposed Federal or New York State drinking-water standards at each of the 16 wells sampled: color (one sample), sodium (three samples), sulfate (three samples), total dissolved solids (four samples), aluminum (one sample), arsenic (two samples), copper (one sample), iron (nine samples), manganese (eight samples), radon-222 (nine samples), and total coliform bacteria (six samples). Existing drinking-water standards for pH, chloride, fluoride, nitrate, nitrite, antimony, barium, beryllium, cadmium, chromium, lead, mercury, selenium, silver, thallium, zinc, gross alpha radioactivity, uranium, fecal coliform, Escherichia coli, and heterotrophic bacteria were not exceeded in any of the samples collected. None of the pesticides and VOCs analyzed exceeded existing drinking-water standards.

New York↗
USGS2012

Specific conductance measurements in central and western New York streams - A retrospective characterization

U.S. Geological Survey (USGS) Data Rescue Program funds were used to recover data from paper records for 139 streamgages across central and western New York State; 6,133 different streamflow measurement forms, collected between 1970-80, contained field water-quality measurements. The water-quality data were entered, reviewed, and uploaded into the USGS National Water Information System. In total, 4,285 unique site visits were added to the database. The new values represent baseline water quality from which to measure change and will lead to a comparison of water-quality change over the last 40 years and into the future. Specific conductance was one of the measured properties and represents a simple way to determine if ambient inorganic water quality has been altered by anthropogenic (road salt runoff, wastewater discharges, or natural gas development) or natural sources. The objective of this report is to describe ambient specific conductance characteristics of surface water across the central and western part of New York. This report presents median specific conductance of stream discharge for the period 1970-80 and a description of the relation between specific conductance and concentrations of total dissolved solids (TDS) retrieved from the USGS National Water Information System (NWIS) database from 1955 to present. The data descriptions provide a baseline of surface-water specific conductance data that can used for comparison to current and future measurements in New York streams.

New York;Pennsylvania↗
USGS2011

Groundwater quality in the Eastern Lake Ontario Basin, New York, 2008

Water samples were collected from nine production wells and nine private residential wells in the Eastern Lake Ontario Basin of New York from August through October 2008 and analyzed to characterize the chemical quality of groundwater. The wells were selected to provide adequate spatial coverage of the 3,225-square-mile study area; areas of greatest groundwater use were emphasized. Eight of the 18 wells sampled, were screened in sand and gravel aquifers, and 10 were finished in bedrock aquifers. The samples were collected and processed by standard U.S. Geological Survey procedures and were analyzed for 223 physical properties and constituents, including major ions, nutrients, trace elements, radon-222, pesticides, volatile organic compounds (VOCs), and indicator bacteria. Water quality in the study area is generally good, but concentrations of some constituents exceeded current or proposed Federal or New York State drinking-water standards; these were: color (2 samples), pH (1 sample), sodium (5 samples), chloride (1 sample), aluminum (2 samples), iron (5 unfiltered samples), manganese (3 samples), radon-222 (13 samples), and bacteria (4 samples). Dissolved-oxygen concentrations in samples from wells finished in sand and gravel [median 3.8 milligrams per liter (mg/L)] were greater than those from wells finished in bedrock (median less than 0.7 mg/L). The pH of all samples was typically neutral or slightly basic (median 7.4); the median water temperature was 11.3 degrees Celsius. The ions with the highest concentrations were bicarbonate (median 174 mg/L) and calcium (median 24.1 mg/L). Groundwater in the basin ranges from soft to moderately hard [less than or equal to 120 mg/L as CaCO3] and median hardness was 90 mg/L as CaCO3. Concentrations of nitrate plus nitrite in samples from sand and gravel wells (median concentration 0.42 mg/L as nitrogen) were generally higher than those in samples from bedrock wells (median <0.04 mg/L as nitrogen). The trace elements with the highest concentrations were strontium [median 138 micrograms per liter (mug/L)], barium (median 38.2 mug/L) and iron (median 44 mug/L). Radon-222 activities were generally high [median 500 picocuries per liter (pCi/L)]; 72 percent of all samples exceeded a proposed U.S. Environmental Protection Agency (USEPA) drinking-water standard of 300 pCi/L. Five pesticides and pesticide degradates were detected among 6 samples at concentrations of 0.03 mug/L or less; most were herbicides or their degradates. Six VOCs were detected among 9 samples at concentrations of 1.2 mug/L or less; these included 3 trihalomethanes, benzene, toluene, and xylenes. Total coliform bacteria were detected in 3 samples, and the heterotrophic plate count exceeded the USEPA maximum contaminant level (MCL) of 500 colony forming units in one sample. Fecal coliform bacteria, including Escherichia coli, were not detected in any sample.

New York↗
USGS2011

Groundwater quality in the Chemung River Basin, New York, 2008

The second groundwater quality study of the Chemung River Basin in south-central New York was conducted as part of the U.S. Geological Survey 305(b) water-quality-monitoring program. Water samples were collected from five production wells and five private residential wells from October through December 2008. The samples were analyzed to characterize the chemical quality of the groundwater. Five of the wells are screened in sand and gravel aquifers, and five are finished in bedrock aquifers. Two of these wells were also sampled for the first Chemung River Basin study of 2003. Samples were analyzed for 6 physical properties and 217 constituents, including nutrients, major inorganic ions, trace elements, radionuclides, pesticides, volatile organic compounds, phenolic compounds, organic carbon, and four types of bacterial analyses. Results of the water-quality analyses for individual wells are presented in tables, and summary statistics for specific constituents are presented by aquifer type. The results are compared with Federal and New York State drinking-water standards, which typically are identical. Water quality in the study area is generally good, but concentrations of some constituents equaled or exceeded current or proposed Federal or New York State drinking-water standards; these were: sodium (one sample), total dissolved solids (one sample), aluminum (one sample), iron (one sample), manganese (four samples), radon-222 (eight samples), trichloroethene (one sample), and bacteria (four samples). The pH of all samples was typically neutral or slightly basic (median 7.5); the median water temperature was 11.0 degrees Celsius (?C). The ions with the highest median concentrations were bicarbonate (median 202 milligrams per liter [mg/L]) and calcium (median 59.0 mg/L). Groundwater in the study area is moderately hard to very hard, but more samples were hard or very hard (121 mg/L as calcium carbonate (CaCO3) or greater) than were moderately hard (61-120 mg/L as CaCO3); the median hardness was 205 mg/L as CaCO3. The maximum concentration of nitrate plus nitrite was 3.67 mg/L as nitrogen, which did not exceed established drinking-water standards for nitrate plus nitrite (10 mg/L as nitrogen). The trace elements with the highest median concentrations were strontium (median 196.5 micrograms per liter [(u or mu)g/L]), barium (median 186 (u or mu)g/L), and iron (median 72.5 (u or mu)g/L in unfiltered water). Five pesticides and pesticide degradates were detected among four samples at concentrations of 0.11 (u or mu)g/L or less; they included herbicides and herbicide degradates. Six volatile organic compounds (VOCs) were detected among four samples; these included four solvents, methyl tert-butyl ether, and one trihalomethane. Trichloroethene, a solvent, was detected in one production well at 5.5 (u or mu)g/L; the Federal and New York State Maximum Contaminant Level (MCL) (5 (u or mu)g/L) was exceeded. The highest radon-222 activities were in samples from bedrock wells [maximum 1,740 picocuries per liter (pCi/L)]; eight of the wells sampled exceeded a proposed U.S. Environmental Protection Agency (USEPA) drinking-water standard of 300 pCi/L. Any detection of coliform bacteria indicates a potential violation of New York State health regulations; total coliform bacteria were detected in four samples, and fecal coliform bacteria were detected in one sample.&mu;&mu;&mu;

Open-File Report↗
USGS2010

Hydrogeologic and geospatial data for the assessment of focused recharge to the carbonate-rock Aquifer in Genesee County, New York

Existing hydrogeologic and geospatial data useful for the assessment of focused recharge to the carbonate-rock aquifer in the central part of Genesee County, NY, were compiled from numerous local, State, and Federal agency sources. Data sources utilized in this pilot study include available geospatial datasets from Federal and State agencies, interviews with local highway departments and the Genesee County Soil and Water Conservation District, and an initial assessment of karst features through the analysis of ortho-photographs, with minimal field verification. The compiled information is presented in a series of county-wide and quadrangle maps. The county-wide maps present generalized hydrogeologic conditions including distribution of geologic units, major faults, and karst features, and bedrock-surface and water-table configurations. Ten sets of quadrangle maps of the area that overlies the carbonate-rock aquifer present more detailed and additional information including distribution of bedrock outcrops, thin and (or) permeable soils, and karst features such as sinkholes and swallets. Water-resource managers can utilize the information summarized in this report as a guide to their assessment of focused recharge to, and the potential for surface contaminants to reach the carbonate-rock aquifer.

New York↗
USGS2008

Ground-Water Quality in Western New York, 2006

Water samples were collected from 7 production wells and 26 private residential wells in western New York from August through December 2006 and analyzed to characterize the chemical quality of ground water. Wells at 15 of the sites were screened in sand and gravel aquifers, and 18 were finished in bedrock aquifers. The wells were selected to represent areas of greatest ground-water use and to provide a geographical sampling from the 5,340-square-mile study area. Samples were analyzed for 5 physical properties and 219 constituents that included nutrients, major inorganic ions, trace elements, radionuclides, pesticides, volatile organic compounds (VOC), phenolic compounds, organic carbon, and bacteria. Results indicate that ground water used for drinking supply is generally of acceptable quality, although concentrations of some constituents or bacteria exceeded at least one drinking-water standard at 27 of the 33 wells. The cations that were detected in the highest concentrations were calcium, magnesium, and sodium; anions that were detected in the highest concentrations were bicarbonate, chloride, and sulfate. The predominant nutrients were nitrate and ammonia; nitrate concentrations were higher in samples from sand and gravel aquifers than in samples from bedrock. The trace elements barium, boron, copper, lithium, nickel, and strontium were detected in every sample; the trace elements with the highest concentrations were barium, boron, iron, lithium, manganese, and strontium. Eighteen pesticides, including 9 pesticide degradates, were detected in water from 14 of the 33 wells, but none of the concentrations exceeded State or Federal Maximum Contaminant Levels (MCLs). Fourteen volatile organic compounds were detected in water from 12 of the 33 wells, but none of the concentrations exceeded MCLs. Eight chemical analytes and three types of bacteria were detected in concentrations that exceeded Federal and State drinking-water standards, which are typically identical. Sulfate concentrations exceeded the U.S. Environmental Protection Agency (USEPA) Secondary Maximum Contaminant Level (SMCL) of 250 milligrams per liter (mg/L) in three samples, and chloride concentrations exceeded the SMCL of 250 mg/L in two samples. Sodium concentrations exceeded the USEPA Drinking Water Health Advisory of 60 mg/L in nine samples. Iron concentrations exceeded the SMCL of 300 ug/L (micrograms per liter) in 14 filtered samples, and manganese exceeded the USEPA SMCL of 50 ug/L in 15 filtered samples, as well as the New York State MCL of 300 ug/L in 1 filtered sample. Arsenic exceeded the USEPA MCL of 10 ug/L in two samples, aluminum exceeded the SMCL for aluminum of 50 ug/L in one sample, and lead exceeded the MCL of 15 ug/L in one sample. Radon-222 exceeded the proposed USEPA MCL of 300 picocuries per liter in 24 samples. Any detection of coliform bacteria indicates a violation of New York State health regulations; total coliform was detected in 12 samples, and Escherichia coli was detected in 2 samples. The plate counts for heterotrophic bacteria exceeded the MCL (500 colony-forming units per milliliter) in four samples.

Open-File Report↗
USGS2008

Hydrologic and water-quality characterization and modeling of the Onondaga Lake Basin, Onondaga County, New York

Onondaga Lake in Onondaga County, New York, has been identified as one of the Nation’s most contaminated lakes as a result of industrial and sanitary-sewer discharges and stormwater nonpoint sources, and has received priority cleanup status under the national Water Resources Development Act of 1990. A basin-scale precipitation-runoff model of the Onondaga Lake basin was identified as a desirable water-resources management tool to better understand the processes responsible for the generation of loads of sediment and nutrients that are transported to Onondaga Lake. During 2003–07, the U.S. Geological Survey (USGS) developed a model based on the computer program, Hydrological Simulation Program–FORTRAN (HSPF), which simulated overland flow to, and streamflow in, the major tributaries of Onondaga Lake, and loads of sediment, phosphorus, and nitrogen transported to the lake. The simulation period extends from October 1997 through September 2003. The Onondaga Lake basin was divided into 107 subbasins and within these subbasins, the land area was apportioned among 19 pervious and impervious land types on the basis of land use and land cover, hydrologic soil group (HSG), and aspect. Precipitation data were available from three sources as input to the model. The model simulated streamflow, water temperature, concentrations of dissolved oxygen, and concentrations and loads of sediment, orthophosphate, total phosphorus, nitrate, ammonia, and organic nitrogen in the four major tributaries to Onondaga Lake–Onondaga Creek, Harbor Brook, Ley Creek, and Ninemile Creek. Simulated flows were calibrated to data from nine USGS streamflow-monitoring sites; simulated nutrient concentrations and loads were calibrated to data collected at six of the nine streamflow-monitoring sites. Water-quality samples were collected, processed, and analyzed by personnel from the Onondaga County Department of Water Environment Protection. Several time series of flow, and sediment and nutrient loads were generated for known sources of these constituents, including the Tully Valley mudboils (flow and sediment), Otisco Lake (flow and nutrients), the Marcellus wastewater-treatment plant (flow and nutrients), and springs from carbonate bedrock (flow). Runoff from the impervious sewered areas of the City of Syracuse was adjusted for the quantity that was treatable at the county wastewater-treatment plant; the excess flows were routed to nearby streams through combined-sanitary-and-storm-sewer overflows. The mitigative effects that the Onondaga Reservoir and Otisco Lake were presumed to have on loads of sediment and particulate constituents were simulated by adjustment of parameter values that controlled sediment settling rates, deposition, and scour in the reservoir and lake. Graphical representations of observed and simulated data, and relevant statistics, were compared to assess model performance. Simulated daily and monthly streamflows were rated “very good” (within 10 percent of observed flows) at all calibration sites, except Onondaga Creek at Cardiff, which was rated “fair” (10–15 percent difference). Simulations of monthly average water temperatures were rated “very good” (within 7 percent of observed temperatures) at all sites. No observed data were available by which to directly assess the model’s simulation of suspended sediment loads. Available measured total suspended solids data provided an indirect means of comparison but, not surprisingly, yielded only “fair” to “poor” ratings (greater than 30 percent difference) for simulated monthly sediment loads at half the water-quality calibration sites. Simulations of monthly orthophosphate loads ranged from “very good” (within 15 percent of measured loads) at three sites to “poor” (greater than 35 percent difference) at one site; simulations of ammonia nitrogen loads ranged from “very good” at one site to “fair” (25–35 percent difference) at two sites. Simulations of monthly total phosphorus, nitrate, and organic nitrogen loads were generally rated “very good” at all calibration sites. Sources of uncertainty in model results were identified, including (1) errors in precipitation data, (2) limitations in model structure, (3) nonuniqueness of values for highly sensitive parameters, (4) errors or bias in data used to calibrate the different components of the model, (5) misclassification of land-use and land-cover data, (6) changes in land use during the simulation period, (7) unidentified sources or sinks of chemical loads and water-quality processes that varied over time, and (8) differences in scale between large calibrated subbasins and small subbasins to which calibrated parameter values were transferred. Uncertainty in simulations of water-quality constituents was compounded by uncertainty in the processes on which the water-quality simulations were based. Therefore, sediment simulations were affected by uncertainty in the simulation of hydrology, and nutrient simulations were affected by uncertainty in both the hydrologic and sediment processes, as well as, in simulations of water temperature and dissolved oxygen concentrations. The calibrated model can be used to simulate scenarios that represent planned or hypothetical development and implementation of best-management practices in the Onondaga Lake basin and to assess the effects that these changes and practices are likely to have on rural and urban nonpoint sources of pollution to Onondaga Lake. Model results also can be used as input to a hydrodynamic model of Onondaga Lake that is being developed by Onondaga County and to prioritize areas of the basin where mitigative measures to decrease sediment and nutrient loads could provide the greatest benefits to Onondaga Lake.

New York↗
USGS2008

Geohydrology of the Unconsolidated Valley-Fill Aquifer in the Meads Creek Valley, Schuyler and Steuben Counties, New York

The Meads Creek valley encompasses 70 square miles of predominantly forested uplands in the upper Susquehanna River drainage basin. The valley, which was listed as a Priority Waterbody by the New York State Department of Environmental Conservation in 2004, is prone to periodic flooding, mostly in its downstream end, where development is occurring most rapidly. Hydraulic characteristics of the unconsolidated valley-fill aquifer were evaluated, and seepage rates in losing and gaining tributaries were calculated or estimated, in an effort to delineate the aquifer geometry and identify the factors that contribute to flooding. Results indicated that (1) Meads Creek gained about 61 cubic feet of flow per second (about 6.0 cubic feet per second per mile of stream channel) from ground-water discharge and inflow from tributaries in its 10.2-mile reach between the northernmost and southernmost measurement sites; (2) major tributaries in the northern part of the valley are not significant sources of recharge to the aquifer; and (3) major tributaries in the central and southern part of the valley provide recharge to the aquifer. The ground-water portion of streamflow in Meads Creek (excluding tributary inflow) was 11.3 cubic feet per second (ft3/s) in the central part of the valley and 17.2 ft3/s in the southern part - a total of 28.5 ft3/s. Ground-water levels were measured in 29 wells finished in unconfined deposits for construction of a potentiometric-surface map to depict directions of ground-water flow within the valley. In general, ground water flows from the edges of the valley toward Meads Creek and ultimately discharges to it. The horizontal hydraulic gradient for the entire 12-mile-long aquifer averages about 30 feet per mile, whereas the gradient in the southern fourth of the valley averages about half that - about 17 feet per mile. A water budget for the aquifer indicated that 28 percent of recharge was derived from precipitation that falls on the aquifer, 32 percent was from losing reaches of tributaries, 38 percent was unchanneled flow from hillsides that slope toward the valley (this estimate includes runoff and shallow ground-water inflow from till and bedrock), and the remaining 2 percent was from deep ground-water inflow from till and bedrock to the sides and bottom of the aquifer. Nearly all (94 percent) of the water discharged from the aquifer is equivalent to the streamflow gain in Meads Creek; the remaining 6 percent discharges as deep outflow to unconsolidated deposits in the Cohocton River valley. Several characteristics of the Meads Creek valley may contribute to flooding in the downstream area: (1) the southward decrease in the ground-water gradient impedes the ability of the aquifer to transmit water southward and can cause water levels to rise, (2) a high water table, typically only 5 to 10 feet below land surface, results in little storage capacity to absorb water from large storms, (3) a downstream narrowing of the valley impedes the southward flow of ground water and can cause water levels to rapidly rise during periods of prolonged or heavy precipitation, and (4) the upland slopes (till-covered bedrock) produce rapid runoff that recharges the aquifer. The combined effect of these conditions limits the ability of the aquifer to transmit sudden, large increases in recharge from precipitation and thereby provides a high potential for flooding in the southern third of the valley.

Scientific Investigations Report↗
USGS2007

Geologic Map of the Frederick 30' x 60' Quadrangle, Maryland, Virginia, and West Virginia

The Frederick 30? ? 60? quadrangle lies within the Potomac River watershed of the Chesapeake Bay drainage basin. The map area covers parts of Montgomery, Howard, Carroll, Frederick, and Washington Counties in Maryland; Loudoun, Clarke, and Fairfax Counties in Virginia; and Jefferson and Berkeley Counties in West Virginia. Many geologic features (such as faults and folds) are named for geographic features that may or may not be shown on the 1:100,000-scale base map. The geology of the Frederick 30? ? 60? quadrangle, Maryland, Virginia, and West Virginia, was first mapped on the 32 1:24,000-scale 7.5-minute quadrangle base maps between 1989 and 1994. The geologic data were compiled manually at 1:100,000 scale in 1997 and were digitized between 1998 and 1999. The geologic map and database may be used to support activities such as land-use planning, soil mapping, groundwater availability and quality studies, identifying aggregate resources, and conducting engineering and environmental studies. The map area covers distinct geologic provinces and sections of the central Appalachian region that are defined by unique bedrock and resulting landforms. From west to east, the provinces include the Great Valley section of the Valley and Ridge province, the Blue Ridge province, and the Piedmont province; in the extreme southeastern corner, a small part of the Coastal Plain province is present. The Piedmont province is divided into several sections; from west to east, hey are the Frederick Valley synclinorium, the Culpeper and Gettysburg basins, the Sugarloaf Mountain anticlinorium, the Westminster terrane, and the Potomac terrane. The geology of the Frederick quadrangle is discussed by geologic province and sections; the geologic units within each province are discussed from oldest to youngest. Where applicable, the discussion includes information on tectonic origins. For more information concerning the report, please contact the author.

Scientific Investigations Map↗
USGS2001

Preliminary lithogeochemical map showing near-surface rock types in the Chesapeake Bay watershed, Virginia and Maryland

This preliminary experimental lithogeochemical map shows the distribution of rock types in the Virginia and Maryland parts of the Chesapeake Bay watershed. The map was produced digitally by classifying geologic-map units according to composition, mineralogy, and texture; rather than by age and stratigraphic relationships as shown on traditional geologic maps. This map differs from most lithologic maps in that the lithogeochemical unit classification distinguishes those rock units having key water-reactive minerals that may induce acid neutralization, or reduction, of hosted water at the weathering interface. The validity of these rock units, however, is independent of water chemistry, because the rock units are derived from geologic maps and rock descriptions. Areas of high soil carbon content, and sulfide metal deposits are also shown. Water-reactive minerals and their weathering reactions yield five lithogeochemical unit classes: 1) carbonate rock and calcareous rocks and sediments, the most acid-neutralizing; 2)carbonaceous-sulfidic rocks and sediments, oxygen-depleting and reducing; 3) quartzofeldspathic rocks and siliciclastic sediments, relatively weakly reactive with water; 4) mafic silicate rocks/sediments, oxygen consuming and high solute-load delivering; and, 5) the rarer calcareous-sulfidic (carbonaceous) rocks, neutralizing and reducing. Earlier studies in some parts of the map area have related solute loads in ground and stream waters to some aspects of bedrock lithology. More recent preliminary tests of relationships between four of the classes of mapped lithogeochemical units and ground water chemistry, in the Mid-Atlantic area using this map, have focused on and verified the nitrate-reducing and acid-neutralizing properties of some bedrock and unconsolidated aquifer rock types. Sulfide mineral deposits and their mine-tailings effects on waters are beginning to be studied by others. Additional testing of relationships among the lithogeochemical units and aspects of ground and surface water chemistry could help to refine the lithogeochemical classification, and this map. The testing could also improve the usefulness of the map for assessing aquifer reactivity and the transport properties of reactive contaminants such as acid rain, and nitrate from agricultural sources, in the Chesapeake Bay watershed.

Maryland, Virginia↗