Introduction

In 2018, the U.S. Geological Survey (USGS), in cooperation with the New York State Department of Environmental Conservation (NYSDEC), began a study of the unconsolidated and bedrock aquifers along the Salmon River corridor from the foothills of the Adirondack Mountains to the Saint Lawrence valley (also known as the "Saint Lawrence lowlands") in Franklin County, New York. The study supports the Aquifer Mapping Program, which is a collaborative effort of the USGS with the NYSDEC since 1980 to characterize the hydrogeology of stratified-drift aquifers across upstate New York (U.S. Geological Survey, 2015). Studies of the Aquifer Mapping Program inform policy and decision making for wellhead protection programs, groundwater remediation, and water-resource management and planning in upstate New York. Aquifers throughout New York State are at risk of contamination from human-related surface activities (for example, commercial, industrial, agricultural, and residential land uses). The need for groundwater-contamination protection in the Malone area is heightened by an increased need for residential drinking-water supplies caused by potential future population growth (including three correctional facilities), groundwater contamination by runoff from concentrated animal feeding operations (CAFOs), and contamination from the use of pesticides and other chemicals overlying the unconfined aquifer.

Purpose and Scope

This report summarizes the hydrogeology of the unconsolidated and bedrock aquifers in the foothills of the Adirondack Mountains and Saint Lawrence lowlands along the Salmon River corridor in Franklin County, New York (fig. 1). This report includes descriptions of (1) the study area, (2) water-well characteristics, (3) groundwater use, (4) surficial geologic units, (5) spatial distribution of aquifer and confining units, (6) results from horizontal-to-vertical spectral ratio (HVSR) passive seismic surveys, (7) the valley-fill aquifer system, (8) generalized potentiometric surface for the Potsdam Sandstone regional aquifer, and (9) groundwater resource potential. A rationale for resource potential and a generalized summary of groundwater characteristics within the aquifer system is also provided.

The following geospatial datasets that support this work are available for download in shapefile format in Fisher and others (2025a, b):

Study Area Description

The study area encompasses approximately 147 square miles along the Salmon River corridor in the foothills of the Adirondack Mountains and the Saint Lawrence lowlands in Franklin County, New York (fig. 1). This region includes parts of the Towns of Bangor, Bellmont, Brandon, Burke, Constable, Duane, Franklin, Malone, and Westville. The major population center is the Town of Malone, with about 14,000 residents. Other population centers within the study area include Fay, Malone Junction, Whippleville, Teboville, Chasm Falls, Owls Head, Porcaville, Mountain View, and Byrants Mill (fig. 1A). The average population density of the study area is 143 people per square mile, and the average population change from 2010 to 2018 was −3.2 percent (U.S. Census Bureau, 2018). The land cover is varied; about 60 percent of the land is forested, 15 percent is agriculture, 6 percent is developed, and the remainder is barren land, water, or wetlands (National Land Cover Database, 2016). The region has a warm-summer humid continental climate as defined by the Köppen-Geiger classification system (Beck and others, 2018). The average annual temperature is 42.7 degrees Fahrenheit, and the average annual precipitation is 38.7 inches (National Oceanic and Atmospheric Administration, 2020).

The northern half of the study area is in the Saint Lawrence lowlands, and the southern half is in the foothills of the Adirondack Mountains. The landscape is characterized by glacial and alluvial landforms interrupted by exposures of glacially sculpted hills of resistant bedrock that become larger and more defined to the south. The sedimentary bedrock in the north overlies the metamorphic rocks that are found in outcrops to the south (Nelson and others, 1956; Postel and others, 1956a, b; Isachsen and Fisher, 1970). Elevations within the study area range between 222 and 2,875 feet; the highest summits are along the southern border of the study area, within the Adirondack Mountains.

The study area is drained by two major watersheds (fig. 1B). The Salmon River watershed drains the greater part of the study area, whereas the Trout River watershed drains the northeastern corner of the study area. The Salmon River flows from its headwaters in the foothills of the Adirondack Mountains and enters the southeastern corner of the study area near Bryants Mill. It flows north-to-northwest for about 29 miles before exiting the study area and draining into the Saint Lawrence lowlands and eventually the Saint Lawrence River. The drainage area of the Salmon River at the downstream end of the study area encompasses 186 square miles (U.S. Geological Survey, 2016), of which 115 square miles are in the study area (fig. 1B). The largest tributaries to the Salmon River include Barnes Brook, Branch Brook, Duane Stream, East Branch Deer Creek, Hatch Brook, Ingraham Stream, Plum Brook, Townline Brook, and Winslow Brook. Trout River is fed by Little Trout River, East Branch Trout River, Middle Branch Trout River, and West Branch Trout River. The drainage area of the Trout River at the downstream end of the study area encompasses 48 square miles (U.S. Geological Survey, 2016), of which 32 square miles are within the study area (fig. 1B). Five major dams impede the Salmon River. From south to north, they are (1) Mountain View Lake Dam, (2) Chasm Falls Dam, (3) Ballard Mill Dam, (4) Whittelsey Dam, and (5) Lamica Lake Dam (fig. 1B; U.S. Army Corps of Engineers, 2018).

Data Sources and Methods

Methods and respective data sources used for the development of geospatial layers are described below and in Fisher and others (2025a, b). A surficial geologic map and derivative layers were created using light detection and ranging (lidar) 1-meter resolution data (Federal Emergency Management Agency, 2017), 10-meter digital elevation data (U.S. Geological Survey, 1995), data from the Soil Survey Geographic (SSURGO) database (U.S. Department of Agriculture, 2019), and a compilation of earlier geologic maps (Postel and others, 1956a, b; MacClintock and Stewart, 1965; Denny, 1974; Cadwell and Pair, 1991; Gadd and others, 1993). Well and boring logs from prior USGS investigations and from State agencies (New York State Department of Environmental Conservation [NYSDEC], Water Well Contractor Program; New York State Department of Transportation [NYSDOT]; USGS National Water Information System [NWIS; U.S. Geological Survey, 2020b]) were also used to define the valley-aquifer boundary, evaluate overburden thickness, define the spatial extent of unconfined and confined glacial aquifers, and delineate the spatial extent of the Potsdam Sandstone. Water levels reported by drillers at the time of well completion were used to construct a generalized potentiometric-surface map for the Potsdam Sandstone aquifer. The Topo to Raster Tool in ArcGIS Pro, version 10.7.1 was used to generate an overburden thickness map (Esri, Redlands, California). The geographic location of all well and boring sites used in this study were verified and mapped. Data from drillers' well logs were added to the record. A table of wells and borings that informed this study are provided in Fisher and others (2025a) and were entered into the USGS NWIS database (U.S. Geological Survey, 2020b).

Horizontal-to-vertical spectral ratio (HVSR) passive seismic surveys were completed at a total of 21 sites in the study area. Quality control checks were conducted to ensure that the two seismometers used in this study were functioning properly; this includes one side-by-side check measurement at one site with both seismometers, and seven control measurements next to wells with known bedrock depths. The HVSR method is a non-invasive and cost-effective tool for estimating the thickness of unconsolidated sediments over bedrock. This technique uses a single broadband three-component seismometer (x, y, and z directions) to record ambient seismic noise. The ratio of the averaged horizontal (x, y) to vertical (z) frequency spectrum is used to produce a spectral ratio curve and determine a peak resonant frequency for each site. This frequency can be empirically related to sediment thickness by using average local sediment shear-wave velocity or power-law regression analysis calibrated with a local site of known depths to bedrock (Ibs-von Seht and Wohlenberg, 1999; Lane and others, 2008; Chandler and Lively, 2014; Johnson and Lane, 2016).

HVSR data were collected for at least 30 minutes at each site using a Tromino Model TEP–3C1 three-component seismometer and published in Fisher and others (2025b). The data were processed with Grilla 2018 Rel. 8.0 software to (1) normalize the spectral traces, (2) remove background anthropogenic noise, (3) transform time-domain data to frequency domain data, (4) calculate spectral ratio curves, and (5) determine the resonance frequency (Heisig and Fleisher, 2022; Fisher and others, 2025b).

Two regression equations, derived from 43 control-point measurements with known bedrock depths from locations across upstate New York, including Malone, were used to estimate overburden thickness (Heisig and others, 2021; Fisher and Keto, 2022; Heisig and Fleisher, 2022; Heisig and Izdebski, 2022). The two equations used include the following: a high-velocity equation, y= 366.85∙x^−1.038, where y is equal to bedrock depth in feet and x is the measured resonance frequency in hertz; and a low-velocity equation, y=282.38∙x^−1.235, where y is equal to the bedrock depth in feet, and x is equal to the measured resonance frequency in hertz. These equations are described in detail in figure 2 of Heisig and Fleisher (2022). The high-velocity equation was used for measurements within the valley fill aquifer boundary where the sediments are composed of coarse sand and gravel, till, and mixed stratified sediments of thicknesses of 245 feet or greater. The low-velocity equation was used for measurements where overburden is 50 to 275 feet thick and the mixed stratified sediments are generally fine grained.

Bedrock Geology

The Saint Lawrence lowlands in the northern part of the study area are underlain by Late Cambrian to Early Ordovician sedimentary rocks that gently dip to the north and that overlie the highly metamorphosed rocks of the Adirondack Mountains (fig. 2). The sedimentary rocks include the Potsdam Sandstone and Theresa Formation (Postel and others, 1956a; Wiesnet, 1961; Rickard, 1973; Denny, 1974; Selleck, 1978; Lowe and others, 2015; Chiarenzelli and Selleck, 2016; Lowe and others, 2017; Hersi and others, 2021). The Potsdam Sandstone irregularly transitions upward from heterogeneous felspathic and argillaceous rock to a homogeneous, quartz-rich and matrix-poor rock (Williams and others, 2010). The dolomitic sandstones and sandy dolomite of the Theresa Formation overlie the Potsdam Sandstone and can be distinguished from it by its lesser feldspar content, absence of zircon, and greater rounding of quartz particles (Wiesnet, 1961; Williams and others, 2010). Both the Potsdam Sandstone and Theresa Formation can be found in outcrops in Plum Brook, East Branch Deer Creek, and the Salmon and Trout Rivers. The Altona formation (Lowe and others, 2015) underlies the Potsdam Sandstone east of the study area boundary, and although its western extent is unknown, it may be in the eastern part of the study area (Landing and others, 2009; Lowe and others, 2017; Landing and others, 2019; Hersi and others, 2021).

The foothills of the Adirondack Mountains in the southern part of the study area are underlain by strongly deformed Precambrian metamorphic rocks, mostly granitic gneiss (fig. 2; Isachsen and others, 2000). The resistant metamorphic rocks create substantial topographic relief in the foothills of the Adirondack Mountains. Features composed of metamorphic rock in the area include the Owls Head, Goldsmith, and Plumadore Ranges, and Titusville Mountain and Studley Hill. The Owls Head Range is underlain by Lyon Mountain Granite Gneiss; the Goldsmith and Plumadore Ranges are underlain by Hawkeye Granite Gneiss outcrops; and Titusville Mountain and Studley Hill are underlain by quartz syenite gneiss (fig. 2; Nelson and others, 1956; Postel and others, 1956b).

The study area contains two sets of roughly perpendicular topographic lineaments from fractures that trend southwest-to-northeast and southeast-to-northwest (fig. 2; Isachsen and McKendree, 1977; Earth Satellite Corporation, 1997). These fractured zones intersect both the sedimentary and metamorphic rocks. The age and origin of these and other fracture features are not known but may be a result of regional tectonic events during the Grenville orogeny and the current, slow rise of land-surface elevation throughout the Adirondack Mountain region following deglaciation (Isachsen and others, 2000). There are likely additional brittle structures, but these are concealed by extensive glacial sediments that mantle the region (Postel and others, 1956b).

Glacial Geology

The study area landscape today was largely shaped by the former action of glacial ice. Throughout the past 2.5 million years, the northeastern United States was intermittently covered by continental ice sheets (Ruddiman and Wright, 1987; Randall, 2001). The sediments deposited in the study area, however, are limited to the late Wisconsinan glacial stage and were deposited in five major phases: glacial, deglacial, lacustrine, marine, and postglacial. During the late Wisconsinan glacial stage, the region was covered by ice moving south-to-southwest, which abraded exposed bedrock, produced striae and megascale glacial lineations, and deposited lodgment till (fig. 3). During deglaciation, ablation till and stratified sediments were deposited in the region (Denny, 1974; Clark, 1980; Clark and Karrow, 1984, Franzi and others, 2016).

After the retreat of the glacier north out of the Saint Lawrence lowlands, the northern part of the study area and the present area of Lake Ontario were occupied by the main phase of glacial Lake Iroquois, and fine sand, silt, and clay accumulated in the lake and the northern half of the study area. Other, smaller proglacial-lake (lacustrine) environments in the southern part of the study area also enabled deposits of fine sand, silt, and clay (Clark, 1980; Clark and Karrow, 1984; Franzi and others, 2015; Franzi and others, 2016). Synchronous retreat of the ice margin from the Champlain valley in New York and Vermont allowed proglacial lakes to expand northward at the Ellenburg ice margin (fig. 3; Franzi and others, 2002; Franzi and others, 2015). When the Ellenburg ice margin recession uncovered Covey Hill just north of the United States-Canada Border, glacial Lake Iroquois drained catastrophically through the Covey Hill outlet initially to the level of proglacial Lake Fort Ann, and subsequently enabling the deposition of the Malone delta (fig. 3, MacClintock and Stewart, 1965; Randall, 2001). Further lowering of Lake Fort Ann resulted in shallower lacustrine phases, and fine-to-medium sand and gravel being deposited as beaches and deltas, including the Constable delta (fig. 3), at the northwestern limit of the study area (MacClintock and Stewart, 1965; Clark, 1980; Cadwell and Pair, 1991; Randall, 2001).

The retreat of the Laurentide Ice Sheet margin north of Warwick, Quebec, allowed glacial Lake Fort Ann to drain into the Gulf of Saint Lawrence (Clark and Karrow, 1984; Pair and Rodrigues,1993; Rayburn and others 2005; Franzi and others, 2016). Isostatic depression coupled with ice recession resulted in the Champlain Sea incursion (Pair and others, 1988; Pair and Rodrigues, 1993; Rayburn and others 2005, 2007; Cronin and others, 2012). During the incursion, marine silt and clay were deposited as plains; whereas fine-to-medium sand and sandy-to-bouldery gravel were deposited as beaches within the study area (Clark, 1980; Cadwell and Pair, 1991; Randall, 2001). Stratified sediments deposited during the postglacial period include floodplain alluvium and alluvial fan deposits (figs. 4, 5).

Groundwater Use

Groundwater is the primary source for commercial, industrial, and domestic water within the study area. Households and facilities that use municipal water were identified using tax parcel data from New York State GIS Resources (2020a) combined with population data from the U.S. Census Bureau (2020). Within the study area boundary, approximately 13,200 residents use water supplied from two production wells (U.S. Environmental Protection Agency, 2022), whereas an estimated 2,600 people rely on domestic wells that tap unconsolidated and bedrock aquifers.

Two production wells drilled to bedrock are completed in a thick unconsolidated aquifer south of Chasm Falls. These wells provide most of the water to study area residents not served by individual domestic wells (table 1). Data compiled from 2010 to 2018, excluding 2013, indicate that these production wells have an average yield of more than 1,500 gallons per minute (gal/min) and that the average annual withdrawal was 2.11 million gallons per day (Mgal/d; New York State Department of Environmental Conservation, 2020). The Potsdam Sandstone aquifer is tapped by 74 (40 percent) of the 187 verified domestic wells within the study area. The metamorphic bedrock aquifer is tapped by 38 (20 percent) of the domestic wells, the Theresa Formation is tapped by 12 (6 percent) wells, and an undefined bedrock aquifer supplies 18 (10 percent) of the wells in the study area.

Withdrawals for domestic wells that are completed in unconsolidated aquifers were estimated using orthoimages and tax parcels by counting houses, businesses, and farms within the aquifer boundary but outside the area served by the two production wells. The number of wells that are known to tap into bedrock were subtracted from this estimation, resulting in a count of an estimated 1,111 properties with potential wells that tap the glacial aquifer system. The resulting value is likely an overestimate, as the total number of bedrock wells in the study area are unknown. The count of properties with wells was multiplied by 2.34, the average number of persons per household in Malone (U.S. Census Bureau, 2020), resulting in an estimate of 2,600 people that relied on water withdrawn from private sand and gravel wells. The estimated withdrawal from wells other than the two active production wells was 195,000 gallons per day (gal/d) and 71.2 million gallons per year (Mgal/yr) from the unconsolidated aquifers (table 2). This total is an estimate based on an average water use of 75 gal/d per person for private water systems in New York (Dieter and others, 2018).

Hydrogeology

The spatial distributions of surficial sediments are presented in figure 4 and described in figure 5. The relations between surficial geology, subsurface glacial and postglacial deposits, and the underlying bedrock geology are presented in eight hydrogeologic sections (figs. 6–13); one section longitudinally transects the length of the Salmon River valley (fig. 6), and seven roughly cross the valley from west to east (figs. 7–13). Population centers identified in figure 1 are labeled horizontally above each cross-section. An isopach map depicts the approximate thicknesses of unconsolidated deposits within the valley in figure 14.

Unconsolidated Aquifers

The study area has the following three distinct types of unconsolidated aquifers as described by Randall (2001): (1) surficial sand-plain aquifers composed of stratified lacustrine and deltaic deposits near the northern boundary of the study area in Constable and Westville; (2) unsaturated mountain-front deltaic deposits that lie above the modern stream grade that are deeply incised, transition from sand and gravel downward to fine sand, and are located in the Town of Malone north of the village of Malone; and (3) coarse stratified valley-fill deposits widespread in most valleys in the southwestern part of the study area in the Towns of Malone, Duane, Bellmont, and Franklin.

Alluvial, outwash, lacustrine, deltaic, and ice-contact sand and gravel form the principal aquifers in the study area (figs. 6–10). These deposits, where exposed at the surface, also serve as recharge areas for the surficial and bedrock aquifers. Glacial till and thick lacustrine silt and clay deposits are less permeable and act as a confining or semiconfining layer to the surficial and bedrock aquifers. Thick (>30 feet), continuous deposits of medium to fine lacustrine sands deposited by glacial and proglacial lakes overlie the ice-contact deposits and are shown in sections A–Aʹ, B–Bʹ, and C–Cʹ (figs. 6–8). Thin, discontinuous lacustrine, and commonly gravelly deposits are in the northern part of the study area, as depicted in sections E–Eʹ, F–Fʹ, and H–Hʹ (figs. 10, 11, 13). The Salmon River valley bottom is filled with alluvium with thicknesses of up to 10 to 70 feet, and 1 to 10 feet in its tributaries (figs. 6–13).

The approximate extents of unconsolidated aquifers in the study area were delineated (fig. 15) through integrated analysis of well and borehole logs, HVSR measurements, and surficial geology (figs. 6–13). Both confined and unconfined sand and gravel aquifers are within the study area (fig. 15). The unconfined aquifers in the study area consist of saturated deposits of sand and gravel, above beds of lacustrine silt and clay, or till, or bedrock. The confined aquifers are composed of deposits of sand and gravel below confining beds of lacustrine deposits and till. Twenty-four percent of the 187 wells that are used for domestic water withdrawal in the study area and outside of the production well service area boundary are in unconsolidated aquifers. Depths of domestic wells in unconsolidated aquifers range from 30 feet to 360 feet, with a median of 118 feet. The reported yield for these wells ranges from 3 to 60 gal/min, with a median of 20 gal/min (fig. 16). Most domestic wells are not screened but completed as open hole and do not represent the true well yield potential of the unconsolidated aquifers. Two production wells near Chasm Falls have a combined average withdrawal of more than 1,500 gal/min (table 1). These highly productive wells are in an unconfined sand and gravel aquifer and likely induce infiltration from the Salmon River (Winslow and others, 1965; Alley and others, 1999).

The distribution of surficial facies depicted in figure 4 is consistent with the type of regional deglaciation described by Fairchild (1913, 1919), MacClintock and Stewart (1965), Clark and Karrow (1984), and Franzi and others (2016). As the glacier receded, the ice thinned and revealed lodgement till in the foothills of the Adirondack Mountains and along the valley walls. The valley walls of the Salmon River and surrounding uplands are covered with unstratified deposits of ablation till that were directly deposited by the glacier. Till consists of dense, unsorted sediment that has a fine-grained matrix (such as silt and clay), containing some pebbles, cobbles, and boulders throughout. Till generally has low permeability and yields limited amounts of water (Miller and others, 2022). Till originating from the Potsdam Sandstone tends to contain clasts of pebble and cobble size, whereas till from granitic gneiss contains a high proportion of sand-sized particles (Denny, 1974), resulting in some permeability.

In several locations, the retreating glacier left behind thick (>200 ft), stratified, and variably sorted ice-contact sediments, which were deposited by glacial meltwater in subaerial and subaqueous environments as fine- and coarse-grained layers, as depicted in sections A–Aʹ, B–Bʹ, C–Cʹ, and D–Dʹ (figs. 6–9). Till is likely interbedded with these layers because of slumping, mass movement from melting ice, or deposition from ice during minor readvances of the ice front (fig. 8). Common landforms associated in glaciated terranes include end moraines and ice-contact features such as terraces, pitted outwash, eskers, and deltas.

At section D–Dʹ, near the center of the study area, thick ice-contact deposits, consisting of stratified layers of sand, gravel, cobbles, and minor boulders, fill the valley (fig. 9). These coarse-grained sediments compose the aquifer framework due to their hydraulic conductivity and permeability, which allow for usable water yields. Well yields along this section range from 40 to 97 gal/min. This section is slightly northwest of an approximate ice margin (Denny, 1974), as shown in figure 3. A large southward sloping ice-contact delta was deposited in a proglacial lake confined to the Salmon River valley. The ice-contact delta has an elevation of 1,560 feet and is west of the population center of Owls Head along the upper Salmon River, south of D–Dʹ, and provides evidence that large meltwater streams drained into the Adirondack Mountains shortly before glacial Lake Iroquois expanded into the Saint Lawrence lowlands and the direction of meltwater flow in the northern Adirondack valleys reversed (Randall, 2001).

The valley broadens northward near Whippleville, south of Malone, at sections E–Eʹ and F–Fʹ (figs. 10, 11). Ice-contact deposits are thin, and the depth to bedrock is shallower here in comparison to the southern part of the valley. The northwest side of section E–Eʹ and the entirety of section F–Fʹ overlie the Potsdam Sandstone, which homeowners rely on for drinking water (figs. 6, 10, 11).

Section G–Gʹ (fig. 12) transects deltaic deposits composed largely of fine to coarse sand (with some gravel) that prograded over silt or clay deposited in nearly flat-topped deltas as proglacial lakes occupied the lowlands north of the Adirondack Mountains during deglaciation (Randall, 2001). The large delta in section G–Gʹ, deposited in proglacial Lake Fort Ann, marks the extent of a proglacial lake shoreline (Williams and others, 2010).

The highest elevation deltas close to the uplands are commonly coarse-grained, collapsed ice-contact deposits (Randall, 2001). Multiple deltas were built into the proglacial lakes by streams from the Adirondack Mountains to the south. The fine-grained deposits of sand, silt, and clay in lacustrine deposits have a low permeability and generally are a poor groundwater resource. Local domestic wells typically withdraw groundwater from the Potsdam Sandstone aquifer (figs. 6, 12).

Section H–Hʹ (fig. 13), located at the northern boundary of the study area, shows flat lying ice-contact deposits overlying the Potsdam Sandstone. Some shallower wells tap into these stratified ice-contact deposits; however, most wells tap the bedrock aquifer.

Bedrock Aquifers

Groundwater in the sedimentary and metamorphic bedrock aquifers is stored and flows in secondary porosity, such as separations along bedding and foliation planes, joints, faults, and other fractures. The uppermost part of the bedrock in the study area typically is weathered and fractured and, where saturated, readily transmits groundwater. The Potsdam Sandstone forms a fractured-rock aquifer of regional extent, with bedding-related fracture zones with transmissivities that convey usable quantities of water. Hydraulic-head gradients in the aquifer commonly are downward with a laterally extensive series of sub-horizontal flow zones serving as drains for the groundwater flow system. (Williams and others, 2010).

Water levels reported by drillers at the time that wells were completed, between 1977 to 2017, were used to construct a generalized potentiometric-surface map for the Potsdam Sandstone aquifer (fig. 2). Groundwater generally flows from recharge areas in the foothills of the Adirondack Mountains to the Potsdam Sandstone aquifer in a north-northwest direction. Recharge occurs in areas of thin, discontinuous till or where bedrock is exposed. Thick deposits of till or lacustrine silt and clay impede groundwater recharge to the aquifer.

The Potsdam Sandstone is the most productive bedrock aquifer in the study area. Reported yields from 74 domestic wells in the Potsdam Sandstone aquifer range between 3 to 200 gal/min, with a median yield of 17 gal/min (fig. 16). Only 12 known wells are drilled into the Theresa Formation and have yields that range from 2 to 30 gal/min, with a median of 20 gal/min (fig. 16). Metamorphic rocks are the least productive and have reported well yields that range from 0 to 45 gal/min, with a median of 4 gal/min (fig. 16). Boreholes (33), production wells (2), and test wells (5) are excluded in this assessment.

Summary

This report presents the findings of an investigation of the hydrogeology of the Malone valley-fill aquifer system and associated water resources in northern Franklin County, New York, led by the U.S. Geological Survey in cooperation with the New York State Department of Environmental Conservation. The study included data and interpretations contained in soil-survey maps, topographic maps, lidar, well records, and the published reports included in the “References Cited” section of this report. Twenty-one horizontal-to-vertical spectral ratio (HVSR) passive seismic measurements augmented the depth-to-bedrock database and aided the effort to define the geometry of the aquifer system. All well, boring, and HVSR measurements are provided in a supporting data release. Deglaciation and the resulting glacial deposits strongly influence well productivity and the distribution of confined and unconfined aquifers within the valley. Well locations, surficial geology, thickness of unconsolidated deposits, and locations of eight hydrogeologic sections are presented in the figures contained in this report and a supporting data release.

Groundwater is the primary source for commercial, industrial, and domestic water within the study area. Two production wells, completed in an unconfined thick glacial aquifer in the foothills of the Adirondack Mountains, located south of Chasm Falls, supply water to approximately 13,200 people, including three correctional facilities. The production wells yield an average of more than 1,500 gallons per minute (gal/min) and are likely receiving induced infiltration from the Salmon River. Most residents outside the area served by the two production wells rely on domestic wells that are drilled into bedrock aquifers. Domestic bedrock wells produce water at a rate between 0 gal/min to 200 gal/min, with a median yield of 12 gal/min. Forty percent (74) of the domestic bedrock wells are drilled into the Potsdam Sandstone regional aquifer. Wells drilled into the Potsdam Sandstone have yields that range between 3 gal/min to 200 gal/min, with a median yield of 17 gal/min. Domestic wells that draw water from unconsolidated glacial material have yields that range between 3 to 60 gal/min, with a median yield of 20 gal/min. Groundwater-resource potential is highest in the valley-bottom sediments south of Chasm Falls near the foothills of the Adirondack Mountains, where three unconfined aquifers and one confined aquifer are identified. Ice-contact, alluvial, outwash, and deltaic deposits form unconfined and confined aquifers; glacial till and thick clay act as a confining or semiconfining layer. Unconfined aquifers in the study area are potentially susceptible to contamination by runoff from concentrated animal feeding operations (CAFOs), and contamination from the use of pesticides and other chemicals overlying the unconfined aquifer.