Northern Part of the Aquifer

The northern part of the Tug Hill glacial aquifer system is composed of several types of coarse-grained glaciofluvial and glaciolacustrine deposits as well as some recently deposited alluvium (fig. 8). Outwash ( o s g) and recent alluvium ( a l) form the aquifer in the Sandy Creek Valley east of the village of Adams. Where southwestward-flowing meltwater in Sandy Creek Valley had exited from its narrow valley just east of the village of Adams, it had debouched into a wide embayment that was part of proglacial Lake Iroquois and deposited a wide delta ( d s g). The delta is composed of either sand ( l s s) or sand and gravel ( d s g). The sediments that compose the delta generally grade from coarse to fine-grained material from east to west and with increasing depth below the land surface; the exception is the western margin of the delta, which had been locally reworked into a coarse-gravel beach deposit by wave action along the shoreline of proglacial Lake Iroquois ( b s g; fig. 8). The remaining aquifer area in the northern part is composed of a series of long and narrow beach ridges that had also been developed by wave action along the shoreline of proglacial Lake Iroquois where it had lapped up against the western flank of the Tug Hill Plateau. The beach deposit is composed of well sorted sand and gravel on the tops of beach ridges and medium- to coarse-grained sand on the lower western flanks of the beaches near shallow offshore areas of the lake.

The fine-grained lake-bottom sediments consisting of fine sand, silt, and some clay ( l s s) that were deposited in relatively deep water in former proglacial Lake Iroquois make up the rest of the stratified deposits in the northern part of the Tug Hill glacial aquifer. These fine-grained sediments settled out of suspension and were deposited at the bottom of the lake. In some places in the northern part of the Tug Hill glacial aquifer, these sediments of low hydraulic conductivity (and low permeability) form the boundary of the western side and bottom of the aquifer. The sediments grade westward from fine sand near the shoreline of Lake Iroquois to distal silt and clay in the deeper and quieter water that was farther from the shoreline.

Central Part of the Aquifer

Most of the central part of the Tug Hill glacial aquifer is dominated by a 2-mi-wide and 6.5-mi-long kame and kame-terrace sand and gravel deposit ( k s g; fig. 8). Along the northern and western sides of the aquifer are minor amounts of other types of deposits, including a narrow band of sand and gravel beach deposits ( b s g) that were deposited along the shoreline of Lake Iroquois and a deltaic plain ( d s g) that was deposited where the Salmon River had debouched into Lake Iroquois. In addition, along the eastern side of the aquifer are minor amounts of outwash sand and gravel that were deposited by meltwater streams; in some places, the outwash deposits might subsequently have become mixed with alluvial sand and gravel that drained meltwater from the Tug Hill Plateau during the postglacial period (fig. 8).

Northern Part of the Aquifer

Well and seismic data in the entire northern part of the aquifer indicate that the unconsolidated deposits range in thickness from 4 to 136 ft, with a median thickness of 38 ft. The aquifer geometry in the northern part of the aquifer varies depending on the geologic setting. Northeast of Adams, part of the Tug Hill glacial aquifer occupies a 5-mi-long by 0.4-mi-wide reach of the linear northeast-southwest-trending Sandy Creek Valley (fig. 5A). The aquifer in the Sandy Creek Valley is composed of 25- to 40-ft-thick deposits of outwash ( o s g) and alluvial ( a l) sand and gravel (figs. 8 and 9). Section A–A′ near Toad Hollow Road in the town of Rodman (figs. 5A, 8, and 9) shows that at least 20 ft of lodgment till underlie the 30 to 40 ft of sand and gravel; however, there are no data to determine whether the till extends to bedrock or other types of unconsolidated deposits underlie the till. Depth to bedrock in the center of the valley is about 80 ft below land surface based on a HVSR measurement in the center of the valley (fig. 9).

Approximately 1.5 mi east of the village of Adams, the aquifer in the 0.4-mi-wide Sandy Creek Valley expands out to the west and southwest, forming a broad, 2.2-mi-wide deltaic plain ( d s g; fig. 8). The delta consists mostly of sand, gravel, and pebbly sand in the upper part and mostly sand with some silt and till in the deeper zones (figs. 10 and 11). In general, the deltaic sand and gravel aquifer is 30 to 40 ft thick in the eastern part (fig. 10) and 40 to 55 ft thick in the western part. Locally, deposits are as much as 100 ft thick over a buried bedrock valley that underlies the central part of the delta (fig. 11). The buried valley beneath the delta is in the relatively soft and easily erodible Utica Shale ( Ordovician u) along its contact with the hard and resistant Trenton Limestone ( Ordovician t; fig. 11). It is likely that this contact was a bedrock control for the formation of the buried valley because of preferential erosion of the softer Utica Shale that proceeded along the contact.

The western side of the deltaic plain has been reworked into a beach ridge ( b s g; fig. 8) by wave action along the shoreline of proglacial Lake Iroquois. Beach ridges also form most of the narrow reaches of the aquifer to the north of and at the village of Adams as well as to the south of the deltaic plain (fig. 8). Well and seismic data indicate that the beach-ridge deposits range in thickness from 20 to 50 ft in the northern part of the aquifer (fig. 5A; Fisher and Keto, 2022a, b).

Central Part of the Aquifer

Because of differences in the sedimentary depositional history during deglaciation of the central and northern parts of the Tug Hill glacial aquifer, the composition of the aquifer material differs between the two parts. The largest difference is the deposition of a large kame-moraine deposit ( k s g) that dominates the central part of the aquifer (fig. 8) but is absent in the northern part. Similarities between the two aquifer parts include deltas and extensive beach ridges.

From well and seismic data collected for this study in the central part of the Tug Hill glacial aquifer, unconsolidated deposits range in thickness from 5 to 130 ft, with a median thickness of 43.5 ft. Geohydrologic section D–D′ (figs. 5B, 8, and 12) depicts the typical framework in the northern area of the central part of the aquifer. In this area, beach sand-and-gravel deposits were deposited along the shoreline of proglacial Lake Iroquois, which bounded the western flank of the Tug Hill Plateau in this area. These beach deposits typically range in thickness from 20 to 40 ft and directly overlie bedrock or a thin till layer above the bedrock. The bedrock and till form the bottom of the aquifer.

Section E–E′ (figs. 5B, 8, and 13) typifies the middle portion of the central part of the aquifer, which is dominated by a large complex of kames, kame deltas, and kame terraces ( k s g) that were deposited at the ice front of the retreating glacier. In some places in the western part of the aquifer, lake silt and fine sand ( l s s) and some minor amounts of aeolian sand (sand dunes; a s) overlie lacustrine, beach, and kame deposits (fig. 13).

Section F–F′ (figs. 5B, 8, and 14) typifies the aquifer framework in the southernmost area of the central part of the Tug Hill glacial aquifer, which is also dominated by a large complex of very hummocky kames, kame deltas, and kame terraces ( k s g). In this area, outwash sand and gravel overlie some of the kame deposits in some places in the eastern part of the aquifer (fig. 14).

Northern Part of the Aquifer

The Sandy Creek Valley northeast of the village of Adams, was investigated in detail because (1) the northernmost extent of the aquifer boundary was uncertain (on the basis of evidence that the aquifer might extend farther upgradient in the valley to the northeast than previously mapped by Miller and others, 1988), (2) the village of Adams was exploring nearby areas for an additional source of water, and (3) the linear shape of the valley might have been a result of faulting in the bedrock. In this case, a transmissive rubble zone might have developed along the fault and thus provided a significant local aquifer beneath the Tug Hill glacial aquifer.

If the suspected fault zone were sufficiently fractured and the gradient in hydraulic head vertical and upward within the zone, then a potentially abundant source of groundwater could feasibly flow upward through the rubble zone in the bedrock and recharge the overlying Tug Hill glacial aquifer. HVSR passive seismic surveys in the Sandy Creek Valley were used to determine the altitude of the top surface of bedrock (fig. 7) and detect any indication of fault displacement. Also, two-dimensional electrical resistivity surveys conducted by a hydrogeological consultant for the village of Adams (Hydrosource Associates Inc., 2012), indicated that there was a structural anomaly (possible fault) in this valley.

To find answers to the issues listed above, two USGS test wells (J 230 and J 231) were completed in the Sandy Creek Valley on October 29, 2013 (well logs shown on fig. 15). The test wells were at the previously mapped northernmost extent of the aquifer boundary (Miller and others, 1988), which is between two drumlins (composed of till) that constrict and narrow the Sandy Creek Valley (fig. 5A, inset D). Well J 230 was drilled to a depth of 42 ft below land surface and was finished as an open-end casing in sand and gravel of the Tug Hill glacial aquifer (fig. 15). After well J 230 was developed for 2 hours, the driller reported a visual estimated yield of more than 100 gallons per minute (gal/min); however, this estimate was lowered to about 50 gal/min by the USGS after a volumetric measurement was made of the discharge of the pumped water from the well.

Well J 231 was drilled to a depth of 202 ft below land surface and was finished as an open borehole in the bedrock from depths 136 to 202 ft (fig. 15). Bedrock was first encountered at 136 ft (fig. 15). After well J 231 was developed for 2 hours, the bedrock well yielded only a small amount of water (2 gal/min). During the drilling of well J 231 on October 28, 2013, a groundwater sample was collected from a sand-and-gravel zone at the depth of 30 ft; groundwater samples were collected from both finished wells on November 6, 2013, to characterize the quality of water in the bedrock and in the sand and gravel aquifers and to determine if there was a hydraulic connection between the two aquifers (the results of the chemical analyses are discussed in the “Water Quality” section of this report).

Water levels that were measured in both wells on November 6, 2013, May 8, 2014, and July 17, 2014, indicated that the hydraulic-head relation between the bedrock and sand and gravel aquifers varied: the hydraulic head was higher in the sand and gravel aquifer by 2.06 ft on November 6, 2013, and higher in the bedrock aquifer by 3.16 ft on May 8, 2014, and 2.30 ft on July 17, 2014. However, subsequent water-level measurements (fig. 19) collected by a continuous water-level recorder (data logger with pressure transducer) indicated that the water level in the bedrock well (J 231) was consistently higher than that in the sand and gravel well (J 230) by about 2 to 3 ft during the data-collection period. Therefore, the water-level data indicates that, most of the time, there is a hydraulic potential for upward vertical movement of groundwater from the bedrock into the overlying sand and gravel in this area (fig. 19). Even though there exists a hydraulic potential for a vertical component of groundwater movement from the bedrock upward into the overlying Tug Hill glacial aquifer, two layers of relatively impermeable sediment and low hydraulic conductivity separate the Tug Hill glacial aquifer from the bedrock—a 16.5-ft thick layer of firm silty clay at depths of 47.5 to 64 ft and a 32-ft-thick layer of compacted till at depths of 104 to 136 ft that directly overlies the bedrock (fig. 15). Because of the small differences in water levels and the two relatively impermeable units that separate the bedrock from the Tug Hill glacial aquifer, discharge rates from bedrock to the Tug Hill glacial aquifer in this immediate area are likely to be low.

Water-level data (fig. 20) collected from a pressure transducer that was installed in Sandy Creek (station identifier 04250730; fig. 21A) at a bridge about 1 mi south of the test wells J 230 and J 231 was used to determine the degree of interaction between surface water and groundwater in the bedrock and the Tug Hill glacial aquifer in the Sandy Creek Valley. The relation between the altitudes of the hydraulic heads in the bedrock and Tug Hill glacial aquifer and the altitudes of the stream stages in Sandy Creek are shown in figure 20. These data indicate that water levels in the Tug Hill glacial aquifer rise and fall rapidly and correlate with time and the stage fluctuations in the stream, but the water levels in the bedrock aquifer have a more muted response to fluctuations in stream stage. The water levels after a large snowfall followed by an immediate warming trend and rain during the last 10 days of November 2014 are shown in the inset (detail) graph on figure 20: the stream stage and the groundwater levels in the Tug Hill glacial aquifer increased rapidly, but the rise in the water level in the bedrock aquifer was slower and more gradual. Also, there was a lag in the timing of the water-level peak in the bedrock aquifer after the snowstorm and the melting of the snow (fig. 20, inset [detail] graph).

Because groundwater levels in bedrock usually follow, but lag behind those of the water levels in the Tug Hill glacial aquifer and of the stream stage in Sandy Creek (fig. 20), this trend suggests that either there is a small hydraulic connection between the bedrock, the Tug Hill glacial aquifer, and Sandy Creek at the test well site (even though there are two relatively impermeable units separating the Tug Hill glacial aquifer from the bedrock at the drill sites of test wells J 230 and J 231; fig. 5A) or the hydraulic connection may be in an area in the aquifer other than the test well site, possibly where the confining units are thinner or absent. One example of where the confining bed is absent is on the northwestern valley wall about 0.45 mi to the north of test wells J 230 and J 231 where bedrock is exposed in the stream channel of Sandy Creek; at this location, the stream impinges against the valley wall.

The regional direction of groundwater flow in the northern part of the Tug Hill glacial aquifer is from east to west, with all water ultimately discharging into Lake Ontario. Locally, the direction of groundwater flow depends on the geologic and hydrologic setting. In the Sandy Creek Valley, northeast of the village of Adams, the direction of flow is from the valley walls to Sandy Creek, which is the main groundwater sink in the valley (fig. 16A). In the beach deposits, north and south of the village of Adams, groundwater enters the eastern sides of the beaches and flows westward through the narrow aquifer and discharges to the headwaters of many small streams and wetlands that border the western side of the aquifer. In the broad deltaic plain part of the aquifer, south and east of the village of Adams, groundwater enters the eastern side of the delta and then fans out across the plain. Groundwater in the northern part of the fan flows to the northwest and discharges into Sandy Creek in the village of Adams. In the central part of the delta, groundwater generally flows to the west and discharges to wetlands and to the headwaters of many small streams that border the western side of the aquifer, which also flow to the west and discharge into Lake Ontario. In the southern part of the delta, groundwater flows to the southwest and discharges into Little Sandy Creek (fig. 16A), which also flows westward and empties into Lake Ontario (fig. 2).

Central Part of the Aquifer

The regional direction of groundwater flow in the central part of the Tug Hill glacial aquifer is predominantly from east to west (fig. 16B). Locally, the direction of groundwater flow is highly variable and depends on the local geologic and hydrologic setting. The direction of groundwater flow is controlled mostly by the distribution of sources of recharge and the configuration of the discharge areas, such as the stream and wetland network over the aquifer. It is difficult to describe or generalize the direction of groundwater flow in the central part of the aquifer because the direction of flow is complex and highly variable; it can change within a short distance because of the numerous wetlands that are scattered throughout this part of the aquifer and the complex network of streams that flow in many directions (all directions except eastward). The arrows, which are perpendicular to the contours on the water-table map (fig. 16B), depict the approximate directions of groundwater flow. Because water-level data were not available for the easternmost area of the central part of the aquifer, the altitudes of the water table could not be determined in these areas.

Northern Part of the Aquifer

Groundwater in the northern part of the Tug Hill glacial aquifer is recharged by (1) precipitation that falls directly on the aquifer, (2) unchannelized runoff from till and bedrock hills that border the eastern side of the aquifer, (3) losses from streams that drain the Tug Hill Plateau and discharge water into the eastern area of the aquifer, and (4) groundwater inflow from the till and bedrock on the adjoining Tug Hill Plateau (Miller and others, 2007) or in some places from bedrock underlying the glacial aquifer. Streamflow gain-and-loss measurements were made on June 2, 2009, in selected streams that flow over the Tug Hill glacial aquifer in and near the village of Adams (fig. 21A; table 3) to determine the amount of recharge that the aquifer receives from losing streams and the amount that discharges from the aquifer to gaining reaches of streams. The results of these measurements indicated that most stream reaches were gaining streamflow (receiving discharge from the aquifer) except for two tributaries to Sandy Creek on the eastern side of the aquifer between USGS sites 04250736 (1.2 cubic feet per second [ft³/s]) and 04250737 (0.81 ft³/s) and sites 04250738 (0.04 ft³/s) and 04250739 (0.0 ft³/s). Both these reaches (fig. 21A, orange lines) were losing streamflow to the aquifer. The streamflow gain-and-loss measurements made for this study are consistent with the conceptual recharge model proposed by Miller and others (2007, fig. 17).

Water-temperature data were collected from Sandy Creek Tributary 5 (fig. 21A) in the village of Adams from May 2008 to September 2009 (fig. 22) to determine the interaction between surface water and groundwater in this area of the northern part of the aquifer. The temperature data for the northern part of the aquifer at Sandy Creek Tributary 5 at Adams, N.Y. (USGS station number 04250747) shows an increase in surface-water temperature from 39.9 degrees Fahrenheit (°F; 4.4 degrees Celsius [°C]) in early spring 2009 to more than 60.1°F (15.6 °C) during summer the same year (fig. 22), indicating that groundwater discharges into the stream keep the brook at cool temperatures. The temperature at other streams that received less groundwater seepage or were warmed by sunlight rose to upper 60s to low 70s during summer.

Central Part of the Aquifer

Groundwater in the central part of the Tug Hill glacial aquifer receives recharge from precipitation that falls directly on the aquifer and from upland sources of recharge in the eastern part of the aquifer (Miller and others, 1988). These upland sources along the eastern margin of the aquifer include (1) unchannelized runoff that seeps into the aquifer from adjoining till and bedrock hillsides, (2) groundwater inflow (subsurface flow) that flows into the aquifer from the till and bedrock on the adjoining Tug Hill Plateau, and (3) seepage losses from streams that drain the Tug Hill Plateau and which flow over and lose water to the aquifer (Miller and others, 2007). Streamflow gain-and-loss measurements were also made in selected streams in the central part of the aquifer on May 29, 2008 (fig. 21B; table 3). The results of these measurements indicate that the stream reaches in the central and western parts of the aquifer gained streamflow except along the eastern margin of the aquifer, where streams generally lost water to the aquifer.

Water-temperature data were collected from Trout Brook, Spring Brook, Orwell Creek, and Beaverdam Brook (fig. 21B) from May 2008 to September 2009 and from the Salmon River from May to November 2008 (fig. 22) to determine the interaction between surface water and groundwater in these select sites in the central part of the aquifer. The water-temperature data (fig. 22) from Trout Brook near Centerville (0425040001), Orwell Creek near Altmar (04250000), Beaverdam Brook at Altmar (04249910), and Salmon River at Altmar (433043076000401) indicate that the water temperature cools to or below the freezing point during the winter, warms during spring, and peaks in the upper 60s to mid-70s during July and early August. Trout Brook was slightly cooler by 1.8 to 3.6 °F (1 to 2 °C) than other streams in the central part of the aquifer, presumably because either it receives more cooler groundwater discharging into its channel or its channel is better shaded by vegetation or both. Spring Brook at Richland (04250502), however, shows a temperature pattern different from the patterns for the other stream sites. At this site, large amounts of groundwater discharge to springs at the head of Spring Brook. The water temperature of Spring Brook (fig. 21B) is nearly constant between 46.0 and 48.0 °F (7.8 and 8.9 °C) all year, which indicates that most, if not all, of the water is from nearby sources of groundwater entering the channel (fig. 22). This groundwater, which has had little exposure to warmer and colder ambient air temperatures, stabilizes the low temperature of the water in this stream.

Northern Part of the Aquifer

The estimated average annual groundwater withdrawal from the northern part of the Tug Hill glacial aquifer in 2012 was 217 Mgal/yr (table 4). Of that amount, 197 Mgal/yr was withdrawn by municipalities (village of Adams, hamlet of Adams Center, and the village of Mannsville), and about 20 Mgal/yr was withdrawn by individual homeowners and farms that were not served by municipal water. Other unaccounted users of groundwater withdrawn from the northern part of the Tug Hill glacial aquifer include industries and businesses that are not supplied by municipal water.

In addition to pumping withdrawals, groundwater discharges from the aquifer to many wetlands and springs (not shown) mainly along the western margins of the northern part of the Tug Hill glacial aquifer and to the streams that gain groundwater as they flow from east to west across the aquifer. The discharge measurements on June 2, 2009, in the northern part of the aquifer indicate that all but three stream reaches had gained flow from groundwater seeping into their channels (fig. 21A; table 3).

Central Part of the Aquifer

The estimated average-annual groundwater withdrawal from the central part of the Tug Hill glacial aquifer during 2014–17 was about 1,000 Mgal/yr (table 4). Of that amount, about 261 Mgal/yr was withdrawn by municipalities (villages of Sandy Creek, Lacona, and Pulaski; hamlet of Orwell; and town of Richland), 701 Mgal/yr withdrawn by the NYSDEC Salmon River fish hatchery, and about 43 Mgal/yr withdrawn by individual homeowners and farms that are not served by municipal water. Other unaccounted users of groundwater withdrawn from the central part of the Tug Hill glacial aquifer include industries and businesses that were not supplied by municipal water.

As in the northern part of the Tug Hill glacial aquifer, groundwater in the central part of the aquifer discharges to springs, seeps, and the headwaters of streams in wetlands along the western boundary of the aquifer; and to wetlands and main trunks of major streams in the middle zones of the aquifer. The largest discharge zone in the central part of the Tug Hill glacial aquifer is in the hamlet of Richland, where exceptionally large amounts of groundwater discharge to springs that form the headwaters to Spring Brook (fig. 21B). Four dug wells (OW 493, OW 494, OW 495, and OW 496; locations of wells shown in fig. 5B) in this spring-discharge zone are used to tap the aquifer and supply water to the village of Pulaski (village 3.8 mi west of the wells; fig. 2).

On May 29, 2008, the spring discharge into the headwaters of Spring Brook at Richland (site 4250502; fig. 21B) was measured to be about 5.70 ft³/s (table 3), equal to about 3.7 Mgal/d or 1,350 Mgal/yr (table 3), which is almost twice the discharge (701 Mgal/yr) of the second largest user of groundwater, the fish hatchery (table 4). Streamflow measurements made on May 29, 2008, in the central part of the Tug Hill glacial aquifer indicate that most stream reaches in the central and western parts of the aquifer gained flow from groundwater discharging into stream channels (fig. 21B).

Surface Water

Thirteen surface-water samples were collected in conjunction with streamflow measurements to determine gains or losses in selected streams and tributaries during average annual base-flow conditions in and near the village of Adams on June 2, 2009. Another sample was collected from Sandy Creek on November 6, 2013, near test wells J 230 and J 231 northeast of the village of Adams (fig. 23A). The samples were tested for physiochemical properties, major ions, nutrients, and dissolved oxygen. Results of chemical analyses of surface-water samples are presented in table 1.1.

Groundwater

In the northern part of the Tug Hill glacial aquifer, 11 wells were sampled between August 27 and December 5, 2013—of those, USGS test well J 231 was sampled twice, once during drilling when the bottom of the casing was in sand and gravel (Tug Hill glacial aquifer) at a depth of 30 ft and once after it was finished in bedrock at a depth of 202 ft (fig. 15). of the 11 sampled wells, 3 were municipal wells, 3 were USGS test wells, and 5 were homeowner wells. Water samples that were collected from three municipal-supply wells included one sample each from the villages of Adams, Mannsville, and Sandy Creek/Lacona. In addition, a replicate sample was collected at the village of Adams municipal well (J 216). Water-quality analyses of all samples included measurements of physiochemical properties, major ions, nutrients, and trace elements. Dissolved gases were collected at two wells (J 202 and J 231), CFCs were analyzed in samples collected at three wells (J 202, J 231, and J1653), and tritium was analyzed in a sample collected from one well (J 202). In the northern part of the Tug Hill glacial aquifer, all sampled wells were finished in sand and gravel except for two sampled wells—J 231 and J2156, which were finished in bedrock (mostly limestone interbedded with thin shale beds).

Surface Water

Nine surface-water samples were collected in the central part of the Tug Hill glacial aquifer in conjunction with streamflow measurements to determine streamflow gains or losses in selected streams and tributaries. Eight of the nine surface-water samples were collected on May 29, 2008, and one sample was collected on November 5, 2013 (fig. 23B; table 1.3). All the samples were analyzed for physiochemical properties, major ions, and nutrients, and the sample from the Trout Brook below County Route 2 at Richland station (04250385) was also analyzed for trace elements.

Groundwater

Of the 9 wells where 11 samples were withdrawn on September 24 and November 5, 2013, wells OW1599 (QA2) and OW1643 (QA1) were sampled for quality control with a replicate and a blank sample, respectively (fig. 23B; table 1.4). The analyses of all samples included measurements of physiochemical properties and chemical constituents, including major ions, nutrients, and trace elements. To estimate the age of the groundwater in well OW1599, a sample was collected for analysis of dissolved gases and tritium. Of the nine wells sampled, six were completed in sand and gravel deposits, and three were completed in bedrock (two in shale and one in sandstone). Two municipal wells serving the town of Richland and the village of Pulaski (wells OW 491 and OW 400, respectively) were sampled. Two samples were collected from a well supplying the Salmon River Fish Hatchery (well OW1599), and five samples were collected from four homeowner wells.

Surface Water

Four median values of physiochemical properties of surface water—pH and water temperature—were slightly greater and specific conductance was much greater in the northern part of the Tug Hill glacial aquifer than in the central part. Three median concentrations of major ions in surface water—hardness (dissolved calcium and magnesium), calcium, and alkalinity—were much greater and most other major ions were slightly greater in the northern part of the Tug Hill glacial aquifer than in the central part probably because of the dissolution of the limestone that underlies most of that area and the high-carbonate content of the clasts in the sand and gravel. All median concentrations of nutrients in surface water were slightly greater in the northern part than in the central part of the Tug Hill glacial aquifer except for nitrate plus nitrite as nitrogen, which was about the same in both parts.

Groundwater

For median values of physiochemical properties of groundwater, dissolved oxygen was about two times greater in the central part of the Tug Hill glacial aquifer than in the northern part, and pH was slightly greater (by 0.3 pH unit) in the central part than in the northern part. Median values for specific conductance were about twice as great, dissolved solids were about two times as great, and water temperature was slightly greater (by 4.4 °F) in groundwater samples from the northern part than from the central part of the aquifer (fig. 24; tables 1.2 and 1.4).

For median values of concentrations of major ions in groundwater, hardness as CaCO₃ in the northern part of the aquifer was about twice as great and concentrations of calcium and sodium were more than three times as great as those in the central part. As was the case with surface water, the much greater median concentrations for calcium, hardness, and alkalinity in the northern part of the aquifer are likely caused by the dissolution of the limestone that underlies most of that area and to the high-carbonate content of the clasts in the sand and gravel. There was little or no difference in median concentrations between the two parts of the aquifer for silica and iron. Concentrations of most other major ions were slightly greater in the northern part than in the central part of the Tug Hill glacial aquifer; the exceptions were bromide, silica, and magnesium whose concentrations were greater in the central part. There were few differences in median values of concentrations of nutrients in groundwater between the northern and central parts of the Tug Hill glacial aquifer except for nitrate plus nitrite as nitrogen, which was higher in the northern part (with a median of 0.391 mg/L) than in the central part (with a median of 0.091 mg/L).

Median concentrations of the trace elements barium, boron, lead, nickel, strontium, uranium, and zinc in groundwater were much greater in the northern part than in the central part of the Tug Hill glacial aquifer (fig. 24). Median concentrations of copper, and molybdenum were slightly greater in groundwater from the northern part than in the central part. There was little or no difference in the median concentrations of aluminum, antimony, arsenic, beryllium, cadmium, chromium, lithium, selenium, and silver between the two parts of the aquifer.