Geology topics

Ronald A. Sloto

Publications and source records attributed to Ronald A. Sloto.

At least 19 recordsLinked to original sources

USGS2017

Evaluation of long-term trends in hydrologic and water-quality conditions, and estimation of water budgets through 2013, Chester County, Pennsylvania

An evaluation of trends in hydrologic and water quality conditions and estimation of water budgets through 2013 was done by the U.S. Geological Survey in cooperation with the Chester County Water Resources Authority. Long-term hydrologic, meteorologic, and biologic data collected in Chester County, Pennsylvania, which included streamflow, groundwater levels, surface-water quality, biotic integrity, precipitation, and air temperature were analyzed to determine possible trends or changes in hydrologic conditions. Statistically significant trends were determined by applying the Kendall rank correlation test; the magnitudes of the trends were determined using the Sen slope estimator. Water budgets for eight selected watersheds were updated and a new water budget was developed for the Marsh Creek watershed. An average water budget for Chester County was developed using the eight selected watersheds and the new Marsh Creek water budget. Annual and monthly mean streamflow, base flow, and runoff were analyzed for trends at 10 streamgages. The periods of record at the 10 streamgages ranged from 1961‒2013 to 1988‒2013. The only statistically significant trend for annual mean streamflow was for West Branch Brandywine Creek near Honey Brook, Pa. (01480300) where annual mean streamflow increased 1.6 cubic feet per second (ft 3 /s) per decade. The greatest increase in monthly mean streamflow was for Brandywine Creek at Chadds Ford, Pa. (01481000) for December; the increase was 47 ft 3 /s per decade. No statistically significant trends in annual mean base flow or runoff were determined for the 10 streamgages. The greatest increase in monthly mean base flow was for Brandywine Creek at Chadds Ford, Pa. (01481000) for December; the increase was 26 ft 3 /s per decade. The magnitude of peaks greater than a base streamflow was analyzed for trends for 12 streamgages. The period of record at the 12 stream gages ranged from 1912‒2012 to 2004–11. Fifty percent of the streamgages showed a small statistically significant increase in peaks greater than the base streamflow. The greatest increase was for Brandywine Creek at Chadds Ford, Pa. (01481000) during 1962‒2012; the increase was 1.8 ft 3 /s per decade. There were no statistically significant trends in the number of floods equal to or greater than the 2-year recurrence interval flood flow. Twenty‒one monitoring wells were evaluated for statistically significant trends in annual mean water level, minimum annual water level, maximum annual water level, and annual range in water-level fluctuations. For four wells, a small statistically significant increase in annual mean water level was determined that ranged from 0.16 to 0.7 feet per decade. There was poor or no correlation between annual mean groundwater levels and annual mean streamflow and base flow. No correlation was determined between annual mean groundwater level and annual precipitation. Despite rapid population growth and land-use change since 1950, there appears to have been little or no detrimental effects on groundwater levels in 21 monitoring wells. Long-term precipitation and temperature data were available from the West Chester (1893‒2013) and Phoenixville, Pa. (1915‒2013) National Oceanic and Atmospheric Administration (NOAA) weather stations. No statistically significant trends in annual mean precipitation or annual mean temperature were determined for either station. Both weather stations had a significant decrease in the number of days per year with precipitation greater than or equal to 0.1 inch. Annual mean minimum and maximum temperatures from the NOAA Southeastern Piedmont Climate Division increased 0.2 degrees Fahrenheit (F) per decade between 1896 and 2014. The number of days with a maximum temperature equal to or greater than 90 degrees F increased at West Chester and decreased at Phoenixville. No statistically significant trend was determined for annual snowfall amounts. Data from 1974 to 2013 for three stream water-quality monitors in the Brandywine Creek watershed were evaluated. The monitors are on the West Branch Brandywine Creek at Modena, Pa. (01480617), East Branch Brandywine Creek below Downingtown, Pa. (01480870), and Brandywine Creek at Chadds Ford, Pa. (01481000). Statistically significant upward trends were determined for annual mean specific conductance at all three stations, indicating the total dissolved solids load has been increasing. If the current trend continues, the annual mean specific conductance could almost double from 1974 to 2050. The increase in specific conductance likely is due to increases in chloride concentrations, which have been increasing steadily over time at all three stations. No correlation was found between monthly mean specific conductance and monthly mean streamflow or base flow. Statistically significant upward trends in pH were determined for all three stations. Statistically significant upward trends in stream temperature were determined for East Branch Brandywine Creek below Downingtown, Pa. (01480870) and Brandywine Creek at Chadds Ford, Pa. (01481000). The stream water-quality data indicate substantial increases in the minimum daily dissolved oxygen concentrations in the Brandywine Creek over time. The Chester County Index of Biotic Integrity (CC-IBI) determined for 1998‒2013 was evaluated for the five biological sampling sites collocated with streamgages. CC-IBI scores are based on a 0‒100 scale with higher scores indicating better stream quality. Statistically significant upward trends in the CC-IBI were determined for West Branch Brandywine Creek at Modena, Pa. (01480617) and East Branch Brandywine Creek below Downingtown, Pa. (01480870). No correlation was found between the CC-IBI and streamflow, precipitation, or stream specific conductance, pH, temperature, or dissolved oxygen concentration. A Chester County average water budget was developed using the nine estimated watershed water budgets. Average precipitation was 48.4 inches, and average streamflow was 21.4 inches. Average runoff and base flow were 8.3 and 13.1 inches, respectively, and average evapotranspiration and estimation of errors was 27.2 inches."

Pennsylvania↗

USGS2017

Evaluation of the streamgage network for estimating streamflow statistics at ungaged sites in Pennsylvania and the Susquehanna River Basin in Pennsylvania and New York

The current (2015) streamgage network in Pennsylvania and the Susquehanna River Basin in Pennsylvania and New York was evaluated in order to design a network that would meet the hydrologic needs of many partners and serve a variety of purposes and interests, including estimation of streamflow statistics at ungaged sites. This study was done by the U.S. Geological Survey, in cooperation with the Pennsylvania Department of Environmental Protection and the Susquehanna River Basin Commission. The study area includes the Commonwealth of Pennsylvania and the Susquehanna River Basin in Pennsylvania and New York. For this study, 229 streamgages were identified as reference streamgages that could be used to represent ungaged watersheds. Criteria for a reference streamgage are a minimum of 10 years of continuous record, minimally altered streamflow, and a drainage area less than 1,500 square miles. Some of the reference streamgages have been discontinued but provide historical hydrologic information valuable in the determination of streamflow characteristics of ungaged watersheds. Watersheds in the study area not adequately represented by a reference streamgage were identified by examining a range of basin characteristics, the extent of geographic coverage, and the strength of estimated streamflow correlations between gaged and ungaged sites. Basin characteristics were determined for the reference streamgage watersheds and the 1,662 12-digit hydrologic unit code (HUC12) subwatersheds in Pennsylvania and the Susquehanna River Basin using a geographic information system (GIS) spatial analysis and nationally available GIS datasets. Basin characteristics selected for this study include drainage area, mean basin elevation, mean basin slope, percentage of urbanized area, percentage of forested area, percentage of carbonate bedrock, mean annual precipitation, and soil thickness. A GIS spatial analysis was used to identify HUC12 subwatersheds outside the range of basin characteristics of the reference streamgages. There were 320 HUC12 subwatersheds, or 19 percent of the study area, with basin characteristics outside the range represented by the reference streamgage watersheds. A GIS spatial analysis was used to identify geographic gaps in the streamgage network. For each streamgage, a watershed area, called the gage statistical area (GSA), was delineated. The GSA shows the drainage area within a specific drainage-area ratio of the streamgage for transfer of streamflow statistics from that streamgage to ungaged sites on the valid statistical reach of the GSA for a streamgage. In Pennsylvania, a drainage-area ratio of 0.33–3 times the drainage area of the ungaged site was found to perform as well as, if not better than, more traditional ratios such as 0.5–1.5 (or 2) for transfer of selected streamflow statistics. A total of 1,102 HUC12 subwatersheds, or 66 percent of the study area, are outside the GSA for a reference streamgage. The USGS Baseline Streamflow Estimator (BaSE) program was used to determine how well HUC12 subwatersheds outside the streamgage GSAs are represented by the reference streamgage network in Pennsylvania, based on estimated streamflow correlation. The centroid of each HUC12 subwatershed was run through the BaSE program to determine the reference streamgage with the highest estimated streamflow correlation. There were 929 HUC12 subwatersheds in Pennsylvania, or 56 percent of the State, with an estimated correlation coefficient less than 0.96. The results from the basin characteristic, geographic, and streamflow correlation analyses were combined to identify 1,405 HUC12 subwatersheds in Pennsylvania and the Susquehanna River Basin in Pennsylvania and New York that lack a representative reference, based on at least one identified gap. Of the 1,405 HUC12 subwatersheds, 139 exhibited all three gaps, indicating a 8-percent gap in the reference streamgage network. Streamgages in areas with similar hydrologic characteristics and in close proximity to one another can potentially provide similar information (termed streamgages with high substitution potential). Streamgages were considered to have a high substitution potential with a nearby streamgage(s) if (1) the streamflow correlation coefficient was equal to or greater than 0.96, (2) the streamgages had 10 years of concurrent record, and (3) the streamgages are in the same watershed within the GSA of the streamgage. Seventy-four current (2015) streamgages with high substitution potential with at least one other streamgage were identified in the study area. Although these identified streamgages have a high substitution potential, they provide valuable streamflow information to a stakeholder. Selected primary uses of these streamgages were identified to determine the overall need for an individual streamgage.

New York, Pennsylvania↗

USGS2016

Baseline assessment of groundwater quality in Wayne County, Pennsylvania, 2014

The Devonian-age Marcellus Shale and the Ordovician-age Utica Shale, geologic formations which have potential for natural gas development, underlie Wayne County and neighboring counties in northeastern Pennsylvania. In 2014, the U.S. Geological Survey, in cooperation with the Wayne Conservation District, conducted a study to assess baseline shallow groundwater quality in bedrock aquifers in Wayne County prior to potential extensive shale-gas development. The 2014 study expanded on previous, more limited studies that included sampling of groundwater from 2 wells in 2011 and 32 wells in 2013 in Wayne County. Eighty-nine water wells were sampled in summer 2014 to provide data on the presence of methane and other aspects of existing groundwater quality throughout the county, including concentrations of inorganic constituents commonly present at low levels in shallow, fresh groundwater but elevated in brines associated with fluids extracted from geologic formations during shale-gas development. Depths of sampled wells ranged from 85 to 1,300 feet (ft) with a median of 291 ft. All of the groundwater samples collected in 2014 were analyzed for bacteria, major ions, nutrients, selected inorganic trace constituents (including metals and other elements), radon-222, gross alpha- and gross beta-particle activity, selected man-made organic compounds (including volatile organic compounds and glycols), dissolved gases (methane, ethane, and propane), and, if sufficient methane was present, the isotopic composition of methane. Results of the 2014 study show that groundwater quality generally met most drinking-water standards, but some well-water samples had one or more constituents or properties, including arsenic, iron, pH, bacteria, and radon-222, that exceeded primary or secondary maximum contaminant levels (MCLs). Arsenic concentrations were higher than the MCL of 10 micrograms per liter (µg/L) in 4 of 89 samples (4.5 percent) with concentrations as high as 20 µg/L; arsenic concentrations were higher than the Health Advisory level of 2 µg/L in 27 of 89 samples (30 percent). Total iron concentrations exceeded the secondary maximum contaminant level (SMCL) of 300 µg/L in 9 of 89 samples (10 percent). The pH ranged from 5.4 to 9.3 and did not meet the SMCL range of greater than 6.5 to less than 8.5 in 27 samples (30 percent); 22 samples had pH values less than 6.5, and 5 samples had pH values greater than 8.5. Total coliform bacteria were detected in 22 of 89 samples (25 percent); Escherichia coli were detected in only 2 of those 22 samples. Radon-222 activities ranged from 25 to 7,400 picocuries per liter (pCi/L), with a median of 2,120 pCi/L, and exceeded the proposed drinking-water standard of 300 pCi/L in 86 of 89 samples (97 percent); radon-222 activities were higher than the alternative proposed standard of 4,000 pCi/L in 12 of 89 samples (13.5 percent). Water from 8 of the 89 wells (9 percent) had concentrations of methane greater than the reporting level of 0.24 milligrams per liter (mg/L) with the detectable methane concentrations ranging from 0.74 to 9.6 mg/L. Of 16 replicate samples submitted to another laboratory with a lower reporting level of 0.0002 mg/L, 15 samples had detectable methane concentrations that ranged from 0.0011 to 9.7 mg/L. Of these 15 samples, low levels of ethane (0.00032 to 0.0017 mg/L) were detected in 6 of 7 samples with methane concentrations greater than 0.75 mg/L. The isotopic composition of methane in 6 of 8 samples with sufficient dissolved methane (about 1 mg/L) for isotopic analysis is consistent with a predominantly thermogenic methane source (sample carbon isotopic ratio δ13C CH4 values ranging from -56.36 to -45.97 parts per thousand (‰) and hydrogen isotopic ratio δD CH4 values ranging from -233.1 to -141.1 ‰). However, the low levels of ethane relative to methane indicate that the methane may be of microbial origin and subsequently underwent oxidation. Isotopic compositions indicated a possibly mixed thermogenic and microbial source (carbon dioxide reduction process) for the methane in 1 of the 8 samples (δ 13 C CH4 of -63.72 and δD CH4 of -192.3 ‰) and potential oxidation of microbial and (or) thermogenic methane in the remaining sample (δ 13 C CH4 of -46.56 and δD CH4 of -79.7 ‰). Groundwater samples with relatively elevated methane concentrations (near or greater than 1 mg/L) had a chemical composition that differed in some respects (pH, selected major ions, and inorganic trace constituents) from groundwater with relatively low methane concentrations (less than 0.75 mg/L). The seven well-water samples with the highest methane concentrations (from about 1 to 9.6 mg/L) also had among the highest pH values (8.1 to 9.3, respectively) and the highest concentrations of sodium, lithium, boron, fluoride, arsenic, and bromide. Relatively elevated concentrations of some other constituents, such as barium, strontium, and chloride, commonly were present in, but not limited to, those well-water samples with elevated methane. Groundwater samples with the highest methane concentrations had chloride/bromide ratios that indicate mixing with a small amount of brine (0.02 percent or less, by volume) similar in composition to that reported for gas and oil well brines in Pennsylvania. Most other samples with low methane concentrations (less than about 1 mg/L) had chloride/bromide ratios that indicate predominantly man-made sources of chloride, such as road salt, septic systems, and (or) animal waste. Although naturally occurring brines may originate from deeper parts of the aquifer system, the man-made sources are likely to affect shallow groundwater. Geochemical modeling showed that the water chemistry of samples with elevated pH, sodium, lithium, bromide, and alkalinity could result from dissolution of calcite (calcium carbonate) combined with cation exchange and mixing with a small amount of brine. Through cation exchange reactions (which are equivalent to processes in a water softener) calcium ions released by calcite dissolution are exchanged for sodium ions on clay minerals. The spatial distribution of groundwater compositions generally shows that (1) relatively dilute, slightly acidic, oxygenated, calcium-carbonate type waters tend to occur in the uplands along the western border of Wayne County; (2) waters of near neutral pH with the highest amounts of hardness (calcium and magnesium) generally occur in areas of intermediate altitudes; and (3) waters with pH values greater than 8, low oxygen concentrations, and the highest arsenic, sodium, lithium, bromide, and methane concentrations can occur in deep wells in uplands but most frequently occur in stream valleys, especially at low elevations (less than about 1,200 ft above North American Vertical Datum of 1988) where groundwater may be discharging regionally, such as to the Delaware River. Thus, the baseline assessment of groundwater quality in Wayne County prior to gas-well development shows that shallow (less than about 1,000 ft deep) groundwater is generally of good quality, but methane and some constituents present in high concentrations in brine (and produced waters from gas and oil wells) may be present at low to moderate concentrations in some parts of Wayne County.

Pennsylvania↗

USGS2014

Baseline groundwater quality from 34 wells in Wayne County, Pennsylvania, 2011 and 2013

Wayne County, Pennsylvania, is underlain by the Marcellus Shale, which currently (2014) is being developed elsewhere in Pennsylvania for natural gas. All residents of largely rural Wayne County rely on groundwater for water supply, primarily from bedrock aquifers (shales and sandstones). This study, conducted by the U.S. Geological Survey in cooperation with the Pennsylvania Department of Conservation and Natural Resources, Bureau of Topographic and Geologic Survey (Pennsylvania Geological Survey), provides a groundwater-quality baseline for Wayne County prior to development of the natural gas resource in the Marcellus Shale. Selected wells completed in the Devonian-age Catskill Formation, undifferentiated; the Poplar Gap and Packerton Members of the Catskill Formation, undivided; and the Long Run and Walcksville Members of the Catskill Formation, undivided, were sampled. Water samples were collected once from 34 domestic wells during August 2011 and August and September 2013 and analyzed to characterize their physical and chemical quality. Samples were analyzed for 45 constituents and properties, including nutrients, major ions, metals and trace elements, radioactivity, and dissolved gases, including methane and radon-222. The quality of the sampled groundwater was generally within U.S. Environmental Protection Agency (USEPA) drinking-water standards, although in some samples, the concentrations of a few constituents exceeded USEPA drinking-water standards and health advisories. The pH of water samples ranged from 5.5 to 9.3 with a median of 7.0. The pH was outside the USEPA secondary maximum contaminant level (SMCL) range of 6.5 to 8.5 in water samples from 14 of the 34 wells (41 percent). Eleven samples had a pH less than 6.5, and three samples had a pH greater than 8.5. Dissolved oxygen concentrations ranged from 0.2 to 11.5 milligrams per liter (mg/L) with a median of 4.7 mg/L. The dissolved oxygen concentration was less than 1 mg/L in water samples from 6 wells; 5 of these 6 water samples had a pH greater than 7.7. Concentrations of dissolved methane ranged from less than 0.00006 to 3.3 mg/L. Methane was detectable in 22 of the 34 wells sampled (65 percent). Methane concentrations were greatest in the 5 samples with pH of 7.8 or higher, ranging from 0.040 to 3.3 mg/L. These samples also had among the lowest concentrations of dissolved oxygen. Three water samples, which had sufficient dissolved methane concentrations (greater than 0.9 mg/L), were analyzed for isotopes of carbon and hydrogen in the methane. The isotopic ratio values fell within (two samples) or close to (one sample) the range for a thermogenic natural gas source. The total dissolved solids concentration ranged from 33 to 346 mg/L; the median concentration was 126 mg/L. Sodium concentrations ranged from 1.07 to 116 mg/L; the median concentration was 9.42 mg/L. The sodium concentration exceeded the USEPA health advisory for sodium of 20 mg/L in water samples from 7 of the 34 wells (21 percent). Concentrations of dissolved arsenic ranged from less than 0.06 to 21.8 micrograms per liter (µg/L); the median concentration was 0.59 µg/L. Water samples from 2 of the 34 wells (6 percent) exceeded the USEPA maximum contaminant level (MCL) of 10 µg/L for arsenic. Concentrations of dissolved manganese ranged from less than 0.15 to 61.5 µg/L; the median concentration was 0.42 µg/L. A water sample from 1 of the 34 wells (3 percent) exceeded the USEPA SMCL of 50 µg/L for manganese; the concentration was less than the USEPA lifetime health advisory of 300 µg/L for manganese. Activities of radon-222 in water from the 34 sampled wells ranged from 110 to 7,180 picocuries per liter (pCi/L); the median activity was 2,105 pCi/L. Water samples from 33 of the 34 wells (97 percent) exceeded the proposed USEPA MCL of 300 pCi/L, and 4 water samples (12 percent) exceeded the USEPA proposed alternative MCL of 4,000 pCi/L for radon-222. Differences in groundwater chemistry were related to pH. Water with a pH greater than 7.6 generally had low dissolved oxygen concentrations, indicating reducing conditions in the aquifer. These high pH waters also had relatively elevated concentrations of methane, arsenic, boron, bromide, fluoride, lithium, and sodium but low concentrations of copper, nickel, and zinc. Water samples with a pH greater than 7.8 had methane concentrations equal to or greater than 0.04 mg/L.

Pennsylvania↗

USGS2013

Baseline groundwater quality from 20 domestic wells in Sullivan County, Pennsylvania, 2012

Water samples were collected from 20 domestic wells during August and September 2012 and analyzed for 47 constituents and properties, including nutrients, major ions, metals and trace elements, radioactivity, and dissolved gases, including methane and radon-222. This study, done in cooperation with the Pennsylvania Department of Conservation and Natural Resources, Bureau of Topographic and Geologic Survey (Pennsylvania Geological Survey), provides a groundwater-quality baseline for central and southern Sullivan County prior to drilling for natural gas in the Marcellus Shale. The analytical results for the 20 groundwater samples collected during this study indicate that only one constituent (gross-alpha radioactivity) in one sample was found to exceed the U.S. Environmental Protection Agency (USEPA) primary drinking water maximum contaminant level (MCL). Water samples from 85 percent of the sampled wells exceeded the proposed USEPA MCL of 300 picocuries per liter (pCi/L) for radon-222; however, only two water samples (10 percent of sampled wells) exceeded the proposed USEPA alternate maximum contaminant level (AMCL) of 4,000 pCi/L for radon-222. In a few samples, the concentrations of total dissolved solids, iron, manganese, and chloride exceeded USEPA secondary maximum contaminant levels (SMCL). In addition, water samples from two wells contained methane concentrations greater than 1 milligram per liter (mg/L). In general, most of the water-quality problems involve aesthetic considerations, such as taste or odor from elevated concentrations of total dissolved solids, iron, manganese, and chloride that develop from natural interactions of water and rock minerals in the subsurface. The total dissolved solids concentration ranged from 31 to 664 mg/L; the median was 130 mg/L. The total dissolved solids concentration in one water sample exceeded the USEPA SMCL of 500 mg/L. Chloride concentrations ranged from 0.59 to 342 mg/L; the median was 12.9 mg/L. The concentration of chloride in one water sample exceeded the USEPA SMCL of 250 mg/L. Concentrations of dissolved iron ranged from less than 3.2 to 6,590 micrograms per liter (µg/L); the median was 11.5 µg/L. The iron concentration in samples from 20 percent of the sampled wells exceeded the USEPA SMCL of 300 µg/L. Concentrations of dissolved manganese ranged from less than 0.13 to 1,710 µg/L; the median was 38.5 µg/L. The manganese concentration in samples from 35 percent of the sampled wells exceeded the USEPA SMCL of 50 µg/L. Activities of radon-222 ranged from 169 to 15,300 picocuries per liter (pCi/L); the median was 990 pCi/L. The gross alpha-particle radioactivity ranged from below detection to 33 pCi/L; the median was 1.5 pCi/L. The gross alpha-particle radioactivity of one water sample exceeded the USEPA MCL of 15 pCi/L. Concentrations of dissolved methane ranged from less than 0.001 to 51.1 mg/L. Methane was not detected in water samples from 13 wells, and the methane concentration was less than 0.07 mg/L in samples from five wells. The highest dissolved methane concentrations were 4.1 and 51.1 mg/L, and the pH of the water from both wells was greater than 8. Water samples from these wells were analyzed for isotopes of carbon and hydrogen in the methane. The isotopic ratio values fell in the range for a thermogenic (natural gas) source. The water samples from these two wells had the highest concentrations of arsenic, boron, bromide, chloride, fluoride, lithium, molybdenum, and sodium of the 20 wells sampled.

Pennsylvania↗

USGS2012

Baseline groundwater quality in national park units within the Marcellus and Utica Shale gas plays, New York, Pennsylvania, and West Virginia, 2011

Groundwater samples were collected from 15 production wells and 1 spring at 9 national park units in New York, Pennsylvania, and West Virginia in July and August 2011 and analyzed to characterize the quality of these water supplies. The sample sites generally were selected to represent areas of potential effects on water quality by drilling and development of gas wells in Marcellus Shale and Utica Shale areas of the northeastern United States. The groundwater samples were analyzed for 53 constituents, including nutrients, major inorganic constituents, trace elements, chemical oxygen demand, radioactivity, and dissolved gases, including methane and radon-222. Results indicated that the groundwater used for water supply at the selected national park units is generally of acceptable quality, although concentrations of some constituents exceeded at least one drinking-water guideline at several wells. Nine analytes were detected in concentrations that exceeded Federal drinking-water standards, mostly secondary standards that define aesthetic properties of water, such as taste and odor. One sample had an arsenic concentration that exceeded the U.S. Environmental Protection Agency maximum contaminant level (MCL) of 10 micrograms per liter (μg/L). The pH, which is a measure of acidity (hydrogen ion activity), ranged from 4.8 to 8.4, and in 5 of the 16 samples, the pH values were outside the accepted U.S. Environmental Protection Agency secondary maximum contaminant level (SMCL) range of 6.5 to 8.5. The concentration of total dissolved solids exceeded the SMCL of 500 milligrams per liter (mg/L) at four sites. The sulfate concentration exceeded the SMCL of 250 mg/L concentration in one sample, and the fluoride concentration exceeded the SMCL of 2 mg/L in one sample. Sodium concentrations exceeded the U.S. Environmental Protection Agency drinking water health advisory of 60 mg/L at four sites. Iron concentrations exceeded the SMCL of 300 μg/L in two samples, and manganese concentrations exceeded the SMCL of 50 μg/L in five samples. Radon-222 concentrations exceeded the proposed U.S. Environmental Protection Agency MCL of 300 picocuries per liter in eight samples.

New York;Pennsylvania;West Virginia↗

USGS2012

Total nitrogen and suspended-sediment loads and identification of suspended-sediment sources in the Laurel Hill Creek watershed, Somerset County, Pennsylvania, water years 2010-11

Laurel Hill Creek is a watershed of 125 square miles located mostly in Somerset County, Pennsylvania, with small areas extending into Fayette and Westmoreland Counties. The upper part of the watershed is on the Pennsylvania Department of Environmental Protection 303(d) list of impaired streams because of siltation, nutrients, and low dissolved oxygen concentrations. The objectives of this study were to (1) estimate the annual sediment load, (2) estimate the annual nitrogen load, and (3) identify the major sources of fine-grained sediment using the sediment-fingerprinting approach. This study by the U.S. Geological Survey (USGS) was done in cooperation with the Somerset County Conservation District. Discharge, suspended-sediment, and nutrient data were collected at two streamflow-gaging stations—Laurel Hill Creek near Bakersville, Pa., (station 03079600) and Laurel Hill Creek at Ursina, Pa., (station 03080000)—and one ungaged stream site, Laurel Hill Creek below Laurel Hill Creek Lake at Trent (station 03079655). Concentrations of nutrients generally were low. Concentrations of ammonia were less than 0.2 milligrams per liter (mg/L), and concentrations of phosphorus were less than 0.3 mg/L. Most concentrations of phosphorus were less than the detection limit of 0.02 mg/L. Most water samples had concentrations of nitrate plus nitrite less than 1.0 mg/L. At the Bakersville station, concentrations of total nitrogen ranged from 0.63 to 1.3 mg/L in base-flow samples and from 0.57 to 1.5 mg/L in storm composite samples. Median concentrations were 0.88 mg/L in base-flow samples and 1.2 mg/L in storm composite samples. At the Ursina station, concentrations of total nitrogen ranged from 0.25 to 0.92 mg/L in base-flow samples; the median concentration was 0.57 mg/L. The estimated total nitrogen load at the Bakersville station was 262 pounds (lb) for 11 months of the 2010 water year (November 2009 to September 2010) and 266 lb for the 2011 water year. Most of the total nitrogen loading was from stormflows. The stormflow load accounted for 76.6 percent of the total load for the 2010 water year and 80.6 percent of the total load for the 2011 water year. The estimated monthly total nitrogen loads were higher during the winter and spring (December through May) than during the summer (June through August). For the Bakersville station, the estimated suspended-sediment load (SSL) was 17,700 tons for 11 months of the 2010 water year (November 2009 to September 2010). The storm beginning January 24, 2010, provided 34.4 percent of the annual SSL, and the storm beginning March 10, 2010, provided 31.9 percent of the annual SSL. Together, these two winter storms provided 66 percent of the annual SSL for the 2010 water year. For the 2011 water year, the estimated annual SSL was 13,500 tons. For the 2011 water year, the SSLs were more evenly divided among storms than for the 2010 water year. Seven of 37 storms with the highest SSLs provided a total of 65.7 percent of the annual SSL for the 2011 water year; each storm provided from 4.6 to 12.3 percent of the annual SSL. The highest cumulative SSL for the 2010 and 2011 water years generally occurred during the late winter. Stormflows with the highest peak discharges generally carried the highest SSL. The sediment-fingerprinting approach was used to quantify sources of fine-grained suspended sediment in the watershed draining to the Laurel Hill Creek near Bakersville streamflow-gaging station. Sediment source samples were collected from five source types: 20 from cropland, 9 from pasture, 18 from forested areas, 20 from unpaved roads, and 23 from streambanks. At the Bakersville station, 10 suspended-sediment samples were collected during 6 storms for sediment-source analysis. Thirty-five tracers from elemental analysis and 4 tracers from stable isotope analysis were used to fingerprint the source of sediment for the 10 storm samples. Statistical analysis determined that cropland and pasture could not be discriminated by the set of tracers and were combined into one source group—agriculture. Stepwise discriminant function analysis determined that 11 tracers best described the 4 sources. An "unmixing" model applied to the 11 tracers showed that agricultural land (cropland and pasture) was the major source of sediment, contributing an average of 53 percent of the sediment for the 10 storm samples. Streambanks, unpaved roads, and forest contributions for the 10 storm samples averaged 30, 17, and 0 percent, respectively. Agriculture was the major contributor of sediment during the highest sampled stormflows. The highest stormflows also produced the highest total nitrogen and suspended-sediment loads.

Pennsylvania↗

USGS2011

Trace metals related to historical iron smelting at Hopewell Furnace National Historic Site, Berks and Chester Counties, Pennsylvania

Iron ore containing elevated concentrations of trace metals was smelted at Hopewell Furnace during its 113 years of operation (1771-1883). The ore used at Hopewell Furnace was obtained from iron mines within 5 miles of the furnace. The iron-ore deposits were formed about 200 million years ago and contain abundant magnetite, the primary iron mineral, and accessory minerals enriched in arsenic, cobalt, copper, lead, and other metals. Hopewell Furnace, built by Mark Bird during 1770-71, was one of the last of the charcoal-burning, cold-blast iron furnaces operated in Pennsylvania. The most productive years for Hopewell Furnace were from 1830 to 1837. Castings were the most profitable product, especially the popular Hopewell Stove. More than 80,000 stoves were cast at Hopewell, which produced as many as 23 types and sizes of cooking and heating stoves. Beginning in the 1840s, the iron industry shifted to large-scale, steam-driven coke and anthracite furnaces. Independent rural enterprises like Hopewell could no longer compete when the iron and steel industries consolidated in urban manufacturing centers. The furnace ceased operation in 1883 (Kurjack, 1954). The U.S. Geological Survey (USGS), in cooperation with the National Park Service, completed a study at Hopewell Furnace National Historic Site (NHS) in Berks and Chester Counties, Pennsylvania, to determine the fate of toxic trace metals, such as arsenic, cobalt, and lead, released into the environment during historical iron-smelting operations. The results of the study, conducted during 2008-10, are presented in this fact sheet.

Pennsylvania↗

USGS2011

Distribution of trace metals at Hopewell Furnace National Historic Site, Berks and Chester Counties, Pennsylvania

Hopewell Furnace, located approximately 50 miles northwest of Philadelphia, was a cold-blast, charcoal iron furnace that operated for 113 years (1771 to 1883). The purpose of this study by the U.S. Geological Survey, in cooperation with the National Park Service, was to determine the distribution of trace metals released to the environment from an historical iron smelter at Hopewell Furnace National Historic Site (NHS). Hopewell Furnace used iron ore from local mines that contained abundant magnetite and accessory sulfide minerals enriched in arsenic, cobalt, copper, and other metals. Ore, slag, cast iron furnace products, soil, groundwater, stream base flow, streambed sediment, and benthic macroinvertebrates were sampled for this study. Soil samples analyzed in the laboratory had concentrations of trace metals low enough to meet Pennsylvania Department of Environmental Protection standards for non-residential use. Groundwater samples from the supply well met U.S. Environmental Protection Agency drinking-water regulations. Concentrations of metals in surface-water base flow at the five stream sampling sites were below continuous concentration criteria for protection of aquatic organisms. Concentrations of metals in sediment at the five stream sites were below probable effects level guidelines for protection of aquatic organisms except for copper at site HF-3. Arsenic, copper, lead, zinc, and possibly cobalt were incorporated into the cast iron produced by Hopewell Furnace. Manganese was concentrated in slag along with iron, nickel, and zinc. The soil near the furnace has elevated concentrations of chromium, copper, iron, lead, and zinc compared to background soil concentrations. Concentrations of toxic elements were not present at concentrations of concern in water, soil, or stream sediments, despite being elevated in ore, slag, and cast iron furnace products. The base-flow surface-water samples indicated good overall quality. The five sampled sites generally had low concentrations of nutrients and major ions but had elevated concentrations of iron, manganese, and strontium when compared to sites sampled in adjacent watersheds. The background site on Baptism Creek generally had the lowest concentrations and yields of constituents. Low concentrations of nutrients and major ions at all five sites indicate that measured concentrations can be attributed to general land use and geology and not to point sources. Streambed-sediment sampling results indicated higher concentrations of all metals except nickel at sites on French Creek compared to the background site on Baptism Creek. Concentrations of aluminum, cadmium, and nickel were highest in sediment from the sampling site upstream from Hopewell Furnace. The highest concentrations of arsenic, boron, cobalt, copper, iron, lead, manganese, mercury, and zinc were detected at the site just below Hopewell Furnace, which indicates that the source of these metals may be in Hopewell Furnace NHS. The invertebrate community at the background site on Baptism Creek was dominated by pollution sensitive taxa indicating a healthy, diverse benthic-macroinvertebrate community. Benthic-macroinvertebrate communities at sampling sites on French Creek indicated disturbed communities when compared to the background site on Baptism Creek and that the overall stream quality immediately above and below Hopewell Furnace NHS is degraded. The benthic-macroinvertebrate communities were dominated by pollution-tolerant taxa, and taxa were less diverse than at the background site. Habitat conditions at the upstream site on French Creek were good but were degraded at downstream sites on French Creek. The major habitat issues at these sites were related to a lack of stable substrate, erosion, and deposition. Water quality and streambed-sediment quality do not indicate that the degraded benthic-macroinvertebrate communities are the result of poor water quality. Habitat conditions (erosion and sedimentation) and physical alterations (water temperature) from the outfall of Hopewell Lake are the most likely causes of the impaired communities.

Pennsylvania↗

USGS2011

Estimated suspended-sediment loads and yields in the French and Brandywine Creek Basins, Chester County, Pennsylvania, water years 2008-09

Turbidity and suspended-sediment concentration data were collected by the U.S. Geological Survey (USGS) at four stream stations--French Creek near Phoenixville, West Branch Brandywine Creek near Honey Brook, West Branch Brandywine Creek at Modena, and East Branch Brandywine Creek below Downingtown--in Chester County, Pa. Sedimentation and siltation is the leading cause of stream impairment in Chester County, and these data are critical for quantifying sediment transport. This study was conducted by the USGS in cooperation with the Chester County Water Resources Authority and the Chester County Health Department. Data from optical turbidity sensors deployed at the four stations were recorded at 15- or 30-minute intervals by a data logger and uploaded every 1 to 4 hours to the USGS database. Most of the suspended-sediment samples were collected using automated samplers. The use of optical sensors to continuously monitor turbidity provided an accurate estimate of sediment fluctuations without the collection and analysis costs associated with intensive sampling during storms. Turbidity was used as a surrogate for suspended-sediment concentration (SSC), which is a measure of sedimentation and siltation. Regression models were developed between SSC and turbidity for each of the monitoring stations using SSC data collected from the automated samplers and turbidity data collected at each station. Instantaneous suspended-sediment loads (SSL) were computed from time-series turbidity and discharge data for the 2008 and 2009 water years using the regression equations. The instantaneous computations of SSL were summed to provide daily, storm, and water year annual loads. The annual SSL contributed from each basin was divided by the upstream drainage area to estimate the annual sediment yield. For all four basins, storms provided more than 96 percent of the annual SSL. In each basin, four storms generally provided over half the annual SSL each water year. Stormflows with the highest peak discharges generally carried the highest SSLs. For all stations, the greatest SSLs occurred during the late winter in February and March during the 2008 water year. During the 2009 water year, the greatest SSLs occurred during December and August. For French Creek near Phoenixville, the estimated annual SSL was 3,500 tons, and the estimated yield was 59.1 tons per square mile (ton/mi 2 ) for the 2008 water year. For the 2009 water year, the annual SSL was 4,390 tons, and the yield was 74.3 ton/mi 2 . For West Branch Brandywine Creek near Honey Brook, the estimated annual SSL was 4,580 tons, and the estimated yield was 245 ton/mi 2 for the 2008 water year. For the 2009 water year, the annual SSL was 2,300 tons, and the yield was 123 ton/mi 2 . For West Branch Brandywine Creek at Modena, the estimated annual SSL was 7,480 tons, and the estimated yield was 136 ton/mi 2 for the 2008 water year. For the 2009 water year, the annual SSL was 4,930 tons, and the yield was 90 ton/mi 2 . For East Branch Brandywine Creek below Downingtown, the estimated annual SSL was 8,900 tons, and the estimated yield was 100 ton/mi 2 for the 2008 water year. For the 2009 water year, the annual SSL was 7,590 tons, and the yield was 84 ton/mi 2 .

Pennsylvania↗

USGS2011

An innovative method for nondestructive analysis of cast iron artifacts at Hopewell Furnace National Historic Site, Pennsylvania

The U.S. Geological Survey (USGS) is conducting research at Hopewell Furnace National Historic Site (fig. 1; see sidebar, page 53) in southeastern Pennsylvania to determine the fate of trace metals, such as arsenic, cobalt, and lead, released into the environment during the iron-smelting process. Arsenic is a carcinogen, cobalt is a suspected carcinogen, and lead can cause severe health problems. Iron ore containing elevated quantities of trace metals was smelted at Hopewell Furnace during its 113 years of operation (1771-1883). The ore used at Hopewell Furnace was obtained from local mines, mainly the Jones and Hopewell mines, which were within 5 miles (8 km) of the furnace. The iron ore deposits were formed during the early Jurassic period about 200 million years ago. The deposits are mineralogically similar and contain abundant magnetite, the chief iron mineral, and accessory minerals enriched in arsenic, cobalt, copper, and other metals.

Pennsylvania↗

USGS2010

Changes in groundwater flow and volatile organic compound concentrations at the Fischer and Porter Superfund Site, Warminster Township, Bucks County, Pennsylvania, 1993-2009

The 38-acre Fischer and Porter Company Superfund Site is in Warminster Township, Bucks County, Pa. Historically, as part of the manufacturing process, trichloroethylene (TCE) degreasers were used for parts cleaning. In 1979, the Bucks County Health Department detected TCE and other volatile organic compounds (VOCs) in water from the Fischer and Porter on-site supply wells and nearby public-supply wells. The Fischer and Porter Site was designated as a Superfund Site and placed on the National Priorities List in September 1983. A 1984 Record of Decision for the site required the Fischer and Porter Company to pump and treat groundwater contaminated by VOCs from three on-site wells at a combined rate of 75 gallons per minute to contain groundwater contamination on the property. Additionally, the Record of Decision recognized the need for treatment of the water from two nearby privately owned supply wells operated by the Warminster Heights Home Ownership Association. In 2004, the Warminster Heights Home Ownership Association sold its water distribution system, and both wells were taken out of service. The report describes changes in groundwater levels and contaminant concentrations and migration caused by the shutdown of the Warminster Heights supply wells and presents a delineation of the off-site groundwater-contamination plume. The U.S. Geological Survey (USGS) conducted this study (2006-09) in cooperation with the U.S. Environmental Protection Agency (USEPA). The Fischer and Porter Site and surrounding area are underlain by sedimentary rocks of the Stockton Formation of Late Triassic age. The rocks are chiefly interbedded arkosic sandstone and siltstone. The Stockton aquifer system is comprised of a series of gently dipping lithologic units with different hydraulic properties. A three-dimensional lithostratigraphic model was developed for the site on the basis of rock cores and borehole geophysical logs. The model was simplified by combining individual lithologic units into generalized units representing upward fining sedimentary cycles capped by a siltstone bed. These cycles were labeled units 1 through 8 and are called stratigraphic units in this report. Groundwater in the unweathered zone mainly moves through a network of interconnecting secondary openings--bedding-plane fractures and joints. Groundwater generally is unconfined in the shallower part of the aquifer and confined or semiconfined in the deeper part of the aquifer. The migration of VOCs from the Fischer and Porter Site source area is influenced by geologic and hydrologic controls. The hydrologic controls have changed with time. Stratigraphic units 2 and 3 crop out beneath the former Fischer and Porter plant. VOCs originating at the plant source area entered these stratigraphic units and moved downdip to the northwest. When the wells at and in the vicinity of the site were initially sampled in 1979-80, three public-supply wells (BK-366, BK-367, MG-946) and three industrial-supply wells (BK-368, BK-370, and BK-371) were pumping. Groundwater contaminated with VOCs flowed downdip and then northeast along strike toward well BK-366, downdip toward well BK-368, and downdip and then west along strike toward well MG-946. The long axis of the TCE plume is oriented about N. 18° W. in the direction of dip. In 1979-80, the leading edge of the plume was about 3,500 feet wide. With the cessation of pumping of the supply wells in 2004, the size of the plume has decreased. In 2007-09, the plume was approximately 2,000 feet long and 2,000 feet wide at the leading edge. On the western side of the site, TCE and tetrachloroethylene (PCE) appear to be moving downdip though stratigraphic unit 3. The downdip extent of TCE and PCE migration extended approximately 550 feet off-site to the northwest and 750 feet off-site to the north. TCE concentrations in water samples from wells at the western site boundary increased from 1996 to 2007. On the northern side of the site, TCE and PCE appeared to be moving downward and laterally though stratigraphic units 2, 3, and 4. Groundwater-flow directions shifted to the northwest in the intermediate and deep zones after cessation of pumping of well BK-366 in 2004. The shutdown of the Warminster Heights wells had little effect on the direction of groundwater flow in the shallow zone. In 2007, TCE concentrations measured in water samples from the three remediation wells by the USGS ranged from less than 340 to 3,000 µg/L, and PCE concentrations ranged from less than 8.4 to 51 µg/L. TCE concentrations in water samples from the source-area remediation wells have decreased with time but remain highly variable. From 2001 to 2008, the TCE and PCE concentrations in water samples from wells BK-370 and BK-371 showed a linear decreasing trend. TCE and PCE concentrations in water samples from well BK-1324 showed an exponentially decreasing trend. In 2007, TCE concentrations measured in water samples from shallow wells ranged from less than 0.1 to 14,000 µg/L, and PCE concentrations ranged from less than 0.1 to 340 µg/L. The TCE and PCE plumes followed the hydraulic gradient in the shallow zone. In 2007, TCE concentrations measured in water samples from on-site intermediate-depth monitor wells ranged from less than 0.1 to 500 µg/L, and PCE concentrations ranged from 1.3 to 28 µg/L. The TCE and PCE plumes followed the hydraulic gradient in the intermediate zone and extended off-site to the north and northwest of the source area. Concentrations of TCE in water samples north and west of the source area increased from 1996 to 2007. In 2007, the TCE concentrations measured in water samples from on-site monitor wells in the deep zone ranged from 1.1 to 86 µg/L, and PCE concentrations ranged from less than 0.1 to 8.4 µg/L. The TCE and PCE plumes generally followed the hydraulic gradient in the deep zone and extended off-site to the northwest of the source area. In general, concentrations of TCE in water samples from monitor wells outside the source area increased between 1996 and 2005 and decreased between 2005 and 2007; concentrations were less in 2007 than in 1996.

Pennsylvania↗

USGS2010

Groundwater-quality monitoring program in Chester County, Pennsylvania, 1980-2008

The U.S. Geological Survey in cooperation with the Chester County Water Resources Authority and the Chester County Health Department began a groundwater-quality monitoring program in 1980 in Chester County, Pa., where a large percentage of the population relies on wells for drinking-water supply. This report documents the program and serves as a reference for data collected through the program from 1980 through 2008. The initial focus of the program was to collect data on groundwater quality near suspected localized sources of contamination, such as uncontrolled landfills and suspected industrial wastes, to determine if contaminants were present that might pose a health risk to those using the groundwater. Subsequently, the program was expanded to address the effects of widely distributed contaminant sources associated with agricultural and residential land uses on groundwater quality and to document naturally occurring constituents, such as radium, radon, and arsenic, that are potential hazards in drinking water. Since 2000, base-flow stream samples have been collected in addition to well-water and spring samples in a few small drainage areas to investigate the relation between groundwater quality measured in well samples and streams. The program has primarily consisted of spatial assessment with limited temporal data collected on groundwater quality. Most data were collected through the monitoring program for reconnaissance purposes to identify and locate groundwater-quality problems and generally were not intended for rigorous statistical analyses that might determine land-use or geochemical factors affecting groundwater quality in space or through time. Results of the program found several contaminants associated with various land uses and human activities in groundwater in Chester County. Volatile organic compounds (such as trichloroethylene) were measured in groundwater near suspected localized contaminant sources in concentrations that exceeded drinking-water standards. Groundwater in some agricultural areas had concentrations of nitrate and some pesticides that exceeded drinking-water standards. Elevated concentrations of chloride were measured near salt storage areas and highways. Formaldehyde was detected in groundwater near cemeteries. In residential areas with on-site wastewater disposal, effects on groundwater quality included elevated nitrate concentrations and low concentrations of volatile organic compounds and wastewater compounds, such as antibiotics and detergents. Base-flow samples indicated that groundwater discharge to streams carried contaminants such as nitrate, pesticides, wastewater compounds, and other contaminants. Radionuclides, including radium-226, radium-228, radium-224, and radon-222, and gross alpha-particle activity were measured in groundwater at levels above established and proposed drinking-water standards in some geologic units, particularly in quartzite and quartzite schists. Arsenic concentrations above drinking-water standards were measured in a few samples and were most likely to occur in groundwater in the shales and sandstones in the northern part of the county. Other potential natural hazards, such as lead from aquifer materials or leached from plumbing because of pH, were present in concentrations above drinking-water standards infrequently (less than 10 percent of samples). Limited temporal sampling suggested that chloride concentrations in groundwater increased in the county since the program began in 1980 through 2008, reflecting increasing population and urbanization in that period.

Scientific Investigations Report↗

USGS2009

Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991-2008

Several shutdown-rebound tests have been conducted at the Henderson Road Superfund Site, which has been on the U.S. Environmental Protection Agency's National Priorities List since 1984. For a given test, the extraction wells are turned off, and water samples are collected from selected monitor wells at regular intervals before and during cessation of pumping to monitor for changes in chemical concentrations. A long-term shutdown-rebound test began on July 17, 2006. In support of this test, the U.S. Geological Survey conducted this study to determine the effects of shutting down on-site extraction wells on concentrations of selected contaminants and water levels. Concentrations were compared to ARARs (applicable relevant and appropriate requirements), which were set as remediation goals in the Henderson Road Site Record of Decision. Water from 10 wells in and near the source area and to the north, northeast, and northwest of the source area sampled in 2008 exceeded the 5.52 ug/L (micrograms per liter) ARAR for benzene. The greatest changes in benzene concentration between pre-shutdown samples collected in July 2006 and samples collected in February and March 2008 (19 months after the shutdown) were for wells in and north of the source area; increases in benzene concentration ranged from 1.5 to 164 ug/L. Water from five wells in the source area and to the north and northwest of the source area sampled in 2008 exceeded the 60 ug/L ARAR for chlorobenzene. The greatest changes in chlorobenzene concentration between pre-shutdown samples collected in July 2006 and samples collected in February and March 2008 were for wells north of the source area; increases in chlorobenzene concentration ranged from 6.9 to 99 ug/L. The highest concentrations of chlorobenzene were near or outside the northern site boundary, indicating chlorobenzene may have moved north away from the source area; however, no monitor well clusters are on the northern side of the Pennsylvania Turnpike, which is about 190 feet north of the source area. A much larger area was affected by chlorobenzene than benzene. Chlorobenzene concentrations decreased in the source area and increased at and beyond the site boundary. Water from four wells in and northeast of the source area sampled in 2008 exceeded the 5.06 ug/L ARAR for 1,1-dichloroethane (1,1-DCA). Increases in 1,1-DCA concentration between pre-shutdown samples collected in July 2006 and samples collected in February 2008 ranged from 0.4 to 20 ug/L. Water from two wells in the source area sampled in 2008 exceeded the 175 ug/L ARAR for total xylene. The 1,1-DCA and xylene plumes appear to extend in an east-northeast direction from the source area. Large drawdowns in the Upper Merion Reservoir during droughts in 1998 and 2001 affected water levels in the Chester Valley and at the Henderson Road Site, except for well HR-17-170. After the drought of 2001, water levels in the Chester Valley showed a protracted recovery lasting from September 2001 until June 2005 (46 months). Water-level data were evaluated temporally for 1997-2008 and spatially for (1) June 16, 2003, when the extraction wells were pumping at the full rate prior to the start of the June 2003 shutdown test; (2) July 10, 2006, during the period of reduced pumping after the June 2003 shutdown test; and (3) February 25-29, 2008, when the extraction wells were not pumping. Except for well HR-5-195, wells were categorized as shallow, intermediate-depth, and deep wells. The potentiometric surface for shallow wells did not appear to be affected by pumping of the extraction wells. The general direction of ground-water flow was to the north. The potentiometric surface for intermediate-depth wells showed a cone of depression when the extraction wells were pumping at the full rate but did not show a cone of depression when the extraction wells were pumping at the reduced rate. The ground-water-flow direction was toward the north and northeast, similar to

Scientific Investigations Report↗

USGS2008

Interpretation of Borehole Geophysical Logs at Area C, Former Naval Air Warfare Center, Warminster Township, Bucks County, Pennsylvania, 2007

This study was done by the U.S. Geological Survey in cooperation with the U.S. Navy at Area C of the former Naval Air Warfare Center in Warminster Township, Bucks County, Pa., in support of hydrogeological investigations conducted by the Navy to address ground-water contamination in the Stockton Formation. Borehole geophysical logs were collected, heatpulse-flowmeter measurements were made, and borehole television surveys were run in seven boreholes ranging from 31 to 75 feet deep. Caliper logs and borehole television surveys were used to identify fractures and the location of possible water-bearing zones. Heatpulse-flowmeter measurements were used to identify fractures that were water-bearing zones. Natural-gamma and single-point-resistance logs were used to correlate lithology across the area. Elevated concentrations of tetrachloroethylene (PCE) were measured in water samples from wells with water-bearing zones in the interval of the aquifer where monitor well HN-23A is screened. Water samples from wells with water-bearing zones above or below this interval had substantially lower concentrations of PCE. Wells screened in this interval yielded less than 0.5 gallon per minute, indicating that the interval has low permeability; this may account for the small areal extent and slow migration of PCE.

Open-File Report↗

USGS2008

Effects of Land-Use Changes and Ground-Water Withdrawals on Stream Base Flow, Pocono Creek Watershed, Monroe County, Pennsylvania

The Pocono Creek watershed drains 46.5 square miles in eastern Monroe County, Pa. Between 2000 and 2020, the population of Monroe County is expected to increase by 70 percent, which will result in substantial changes in land-use patterns. An evaluation of the effect of reduced recharge from land-use changes and additional ground-water withdrawals on stream base flow was done by the U.S. Geological Survey (USGS) in cooperation with the U.S. Environmental Protection Agency (USEPA) and the Delaware River Basin Commission as part of the USEPA?s Framework for Sustainable Watershed Management Initiative. Two models were used. A Soil and Water Assessment Tool (SWAT) model developed by the USEPA provided areal recharge values for 2000 land use and projected full buildout land use. The USGS MODFLOW-2000 ground-water-flow model was used to estimate the effect of reduced recharge from changes in land use and additional ground-water withdrawals on stream base flow. This report describes the ground-water-flow-model simulations. The Pocono Creek watershed is underlain by sedimentary rock of Devonian age, which is overlain by a veneer of glacial deposits. All water-supply wells are cased into and derive water from the bedrock. In the ground-water-flow model, the surficial geologic units were grouped into six categories: (1) moraine deposits, (2) stratified drift, (3) lake deposits, (4) outwash, (5) swamp deposits, and (6) undifferentiated deposits. The unconsolidated surficial deposits are not used as a source of water. The ground-water and surface-water systems are well connected in the Pocono Creek watershed. Base flow measured on October 13, 2004, at 27 sites for model calibration showed that streams gained water between all sites measured except in the lower reach of Pocono Creek. The ground-water-flow model included the entire Pocono Creek watershed. Horizontally, the modeled area was divided into a 53 by 155 cell grid with 6,060 active cells. Vertically, the modeled area was discretized into four layers. Layers 1 and 2 represented the unconsolidated surficial deposits where they are present and bedrock where the surficial deposits are absent. Layer 3 represented shallow bedrock and was 200 ft (feet) thick. Layer 4 represented deep bedrock and was 300 ft thick. A total of 873 cells representing streams were assigned to layer 1. Recharge rates for model calibration were provided by the USEPA SWAT model for 2000 land-use conditions. Recharge rates for 2000 for the 29 subwatersheds in the SWAT model ranged from 6.11 to 22.66 inches per year. Because the ground-water-flow model was calibrated to base-flow data collected on October 13, 2004, the 2000 recharge rates were multiplied by 1.18 so the volume of recharge was equal to the volume of streamflow measured at the mouth of Pocono Creek. During model calibration, adjustments were made to aquifer hydraulic conductivity and streambed conductance. Simulated base flows and hydraulic heads were compared to measured base flows and hydraulic heads using the root mean squared error (RMSE) between measured and simulated values. The RMSE of the calibrated model for base flow was 4.7 cubic feet per second for 27 locations, and the RMSE for hydraulic heads for 15 locations was 35 ft. The USEPA SWAT model was used to provide areal recharge values for 2000 and full buildout land-use conditions. The change in recharge ranged from an increase of 37.8 percent to a decrease of 60.8 percent. The ground-water-flow model was used to simulate base flow for 2000 and full buildout land-use conditions using steady-state simulations. The decrease in simulated base flow ranged from 3.8 to 63 percent at the streamflow-measurement sites. Simulated base flow at streamflow-gaging station Pocono Creek above Wigwam Run near Stroudsburg, Pa. (01441495), decreased 25 percent. This is in general agreement with the SWAT model, which estimated a 30.6-percent loss in base flow at the streamflow-gaging station.

Scientific Investigations Report↗

USGS2007

Interpretation of borehole geophysical logs, aquifer-isolation tests, and water-quality data for Sites 1, 3, and 5 at Willow Grove Naval Air Station/Joint Reserve Base, Horsham Township, Montgomery County, Pennsylvania: 2005

Borehole geophysical logging, heatpulse-flowmeter measurements, borehole television surveys, and aquifer-isolation tests were conducted in 2005 at the Willow Grove Naval Air Station/Joint Reserve Base (NAS/JRB) in Horsham Township, Montgomery County, Pa. This study was done by the U.S. Geological Survey (USGS) in cooperation with the U.S. Navy in support of hydrogeological investigations to address ground-water contamination. Data collected for this study are valuable for understanding ground-water flow in the Stockton Formation at the local and regional scale. The Willow Grove NAS/JRB is underlain by the Stockton Formation, which consists of sedimentary rocks of Triassic age. The rocks of the Stockton Formation form a complex, heterogeneous aquifer with partially connected zones of high permeability. Borehole geophysical logs, heatpulse-flowmeter measurements, and borehole television surveys made in seven boreholes ranging from 70 to 350 ft deep were used to identify potential water-producing fractures and fracture zones and to select intervals for aquifer-isolation tests. An upward vertical hydraulic gradient was measured in one borehole, a downward vertical hydraulic gradient was measured in four boreholes, both an upward and a downward vertical hydraulic gradient were measured in one borehole, and no flow was measurable in one borehole. The aquifer-isolation tests isolated 30 discrete fractures in the seven boreholes for collection of depth-discrete hydraulic and water-quality data. Of the 30 fractures identified as potentially water producing, 26 fractures (87 percent) produced more than 1 gallon per minute of water. The specific capacity of the isolated intervals producing more than 1 gallon per minute ranged from 0.02 to 5.2 gallons per minute per foot. There was no relation between specific capacity and depth of the fracture. Samples for analysis for volatile organic compounds were collected from each isolated zone. Tetrachloroethylene (PCE) was the most prevalent compound at Site 1; concentrations were as great as 62 µg/L (micrograms per liter). 1,1-dichloroethane was the most prevalent compound at Site 3; concentrations were as great as 9.3 µg/L. Toluene was the most prevalent compound at Site 5; concentrations were as great as 77 µg/L. For five out of the six wells (83 percent) sampled for field determinations of water-quality constituents, the interval with the lowest dissolved oxygen concentration had the highest total VOC concentration.

Pennsylvania↗

USGS2006

Estimated ground-water availability in the Delaware River basin, 1997-2000

Ground-water availability using a watershed-based approach was estimated for the 147 watersheds that make up the Delaware River Basin. This study, conducted by the U.S. Geological Survey in cooperation with the Delaware River Basin Commission (DRBC), supports the DRBC's Water Resources Plan for the Delaware River Basin. Different procedures were used to estimate ground-water availability for the region underlain by fractured rocks in the upper part of the basin and for surficial aquifers in the region underlain by unconsolidated sediments in the lower part of the basin. The methodology is similar to that used for the Delaware River Basin Commission's Ground-Water Protected Area in Pennsylvania. For all watersheds, ground-water availability was equated to average annual base flow. Ground-water availability for the 109 watersheds underlain by fractured rocks in Delaware, New Jersey, New York, and Pennsylvania was based on lithology and physiographic province. Lithology was generalized by grouping 183 geologic units into 14 categories on the basis of rock type and physiographic province. Twenty-three index streamflow-gaging stations were selected to represent the 14 categories. A base-flow-recurrence analysis was used to determine the average annual 2-, 5-, 10-, 25-, and 50-year-recurrence intervals for each index station. A GIS analysis used lithology and base flow at the index stations to determine the average annual base flow for the 109 watersheds. Average annual base flow for these watersheds ranged from 0.313 to 0.915 million gallons per day per square mile for the 2-year-recurrence interval to 0.150 to 0.505 million gallons per day per square mile for the 50-year-recurrence interval. Ground-water availability for watersheds underlain by unconsolidated surficial aquifers was based on predominant surficial geology and land use, which were determined from statistical tests to be the most significant controlling factors of base flow. Twenty-one index streamflow-gaging stations were selected to represent the 13 categories of predominant surficial geology and land use for the 38 Coastal Plain watersheds. A base-flow-recurrence analysis was used to determine the average annual 2-, 5-, 10-, 25-, and 50-year-recurrence intervals for each group of predominant surficial geology and land use. Average annual base flow for these watersheds ranged from 0.465 to 1.169 million gallons per day per square mile for the 2-year-recurrence interval to 0.178 to 0.670 million gallons per day per square mile for the 50-year-recurrence interval. Estimated 2-, 5-, 10-, 25-, and 50-year annual base-flow-recurrence interval values for each watershed in the Delaware River Basin are considered to be the quantity of ground water available for each watershed over a range of climatic conditions. The recurrence intervals are considered to be relative indicators of climatic difference; the 2-year-recurrence value represents wetter years, and the 50-year-recurrence value represents drier years. The remaining available ground water in each watershed was determined by subtracting current (1997-2000) ground-water withdrawals and consumptive domestic use and adding water recharged by agricultural irrigation and land application of treated-sewage effluent. Ground-water use ranged from 0 to 60.8 percent of available ground water for the 2-year-recurrence interval; it exceeded 25 percent in four watersheds and 50 percent in two watersheds. Ground-water use ranged from 0 to 75.9 percent of available ground water for the 5-year-recurrence interval; it exceeded 25 percent in five watersheds and 50 percent in three watersheds. Ground-water use ranged from 0 to 84.5 percent of available ground water for the 10-year-recurrence interval; it exceeded 25 percent in seven watersheds and 50 percent in four watersheds. Ground-water use ranged from 0 to 103 percent of available ground water for the 25-year-recurrence interval; it exceeded 25 percent in nine watersheds, 5

Delaware, New Jersey, New York, Pennsylvania↗