HYDROGEOLOGIC CHARACTERIZATION OF THOMAS SPRING, JEFFERSON COUNTY, ALABAMA

Watercress Darter National Wildlife Refuge

GEOLOGICAL SURVEY OF ALABAMA

Berry H. (Nick) Tew, Jr. State Geologist

HYDROGEOLOGIC CHARACTERIZATION OF THOMAS SPRING, JEFFERSON COUNTY, ALABAMA

By Marlon R. Cook, Dorina Murgulet, and Alana L. Rogers

Partial funding for this project was provided by the U.S. Fish and Wildlife Service.

Tuscaloosa, Alabama 2014

TABLE OF CONTENTS Introduction ...... 1 Physiographic, stratigraphic, and hydrogeologic settings ...... 2 Land use/land cover ...... 5 Spring discharge, physical properties, and chemical composition ...... 6 Nutrients...... 12 Nitrate ...... 12 Phosphorus...... 13 Metallic constituents ...... 13 Organic constituents...... 15 Isotopic composition...... 16 References cited...... 19

ILLUSTRATIONS

Figure 1. Topography and assessment areas including drainage/recharge areas for Thomas and Glen Springs ...... 3 Figure 2. Geology in the Thomas and Glen Springs area ...... 5 Figure 3. Land-use/land-cover for the Thomas and Glen Spring assessment area...... 7 Figure 4. Thomas Spring physical and chemical parameters...... 9 Figure 5. Piper trilinear diagram showing major ion composition of water collected from Thomas Spring and Trussville wells...... 10 Figure 6. Stiff diagrams for the selected Trussville groundwater samples (FW, W-7, P-2, and W-10) and the Thomas Spring sample (ThS) ...... 11 Figure 7. Cross plot of the δD and δ18O isotope data relative to the GMWL and TLMWL ...... 18

TABLES Table 1. Concentrations (µg/L) of metallic constituents detected in the water sample from Thomas Spring ...... 14

ii INTRODUCTION The hydrogeologic assessment of Thomas Spring by the Geological Survey of Alabama (GSA) was commissioned by the U.S. Fish and Wildlife Service to characterize geologic, hydrologic, and geochemical conditions in Thomas Spring. The assessment consists of an evaluation of available hydrogeologic data and collection of stream and spring discharge data and water samples. The purpose of the assessment was to determine stratigraphic and structural controls for occurrence of the spring, groundwater recharge characteristics to determine spatial and volumetric characteristics of spring discharge, general water quality and contaminant impacts, and age dating of spring discharge to determine groundwater migration patterns. Watercress Darter NWR was established to protect Thomas Spring, one of only 4 known locations where the watercress darter was found naturally. Uplands around the spring contain a mixture of mature pine and hardwoods and dense understory of vegetation. The small size of the refuge (24 acres) and its location in a suburban setting does not provide for a diversity of wildlife. The primary purpose of the refuge is the protection of Thomas Spring and its population of watercress darters (U.S. Fish and Wildlife Service, 2014). The first population of watercress darters was collected at Glenn Springs in 1964. Additional field work has resulted in the location of three other populations: Thomas Spring (1976), Roebuck Springs (1978) and Seven Springs (2002). The greater Birmingham metropolitan areas encompass all of these sites, which are threatened with groundwater pollution and the presence of extensive impervious surfaces (e.g., roads, parking lots, and roofs), which divert water away from the recharge area of the springs’ aquifers and lessens flows. In 1970, the Service officially recognized the watercress darter as an endangered species (U.S. Fish and Wildlife Service, 2014). Little is known about the history of Thomas Spring, where Watercress Darter NWR is located, although it was apparently dammed up for about 20 years prior to the discovery of watercress darters. The damming of Thomas Spring created excellent habitat for the darters by providing slow-moving backwater that allowed dense aquatic vegetation to become established (U.S. Fish and Wildlife Service, 2014).

1 Although care was taken in collecting the water samples as close as possible to the groundwater inflow point, excessive algae in the pond made it impossible to determine the exact location of the inflow point. Therefore, unless the spring discharge rate is very high, samples likely represent a mixture of fresh groundwater with pounded water. Furthermore, during rain events, mixing of the spring water with meteoric water will likely occur in the pond. Nevertheless, a localized source of recharge can be attributed to the spring based on the isotope signature. The oxygen and hydrogen isotopes indicate that recharge to the investigated aquifers originates mainly locally. A more distant source of recharge may be possible through preferentially longer flowpaths along connected fractures.

PHISIOGRAPHIC, STRATIGRAPHIC AND HYDROGEOLOGIC SETTINGS Thomas Spring is located in the Alabama Valley and Ridge section of the Valley and Ridge physiographic Province and the Birmingham-Big Canoe Valley physiographic district (Sapp and Emplaincourt, 1975). The Birmingham-Big Canoe Valley district is a narrow limestone valley, about 4 to 8 mi wide, developed on a faulted anticlinorium with shale, sandstone, and chert outcroppings (Sapp and Emplaincourt, 1975). Elevations in this area vary from 298 to 1,522 feet (U.S. Geological Survey, National Elevation Dataset (NED) Digital Elevation Model (DEM), 1999). The drainage/recharge area for Thomas Spring, located towards the southwest of the Birmingham-Big Canoe Valley, is bounded eastward by Red Mountain, which serves as a surface-water and groundwater divide (fig. 1). Elevations in the designated area vary between 535 ft on the southwest margin to 778 ft atop Sand Mountain (U.S. Geological Survey, National Elevation Dataset (NED) Digital Elevation Model (DEM), 1999). Steeper slopes are characteristic of the eastern part of the study area (13 to 5%) grading to more gentle slopes towards the west including the spring (4-0.5%). After an exhausted search of well records and the study area it was found that no wells were available in the area. Therefore, a potentiometric surface map could not be constructed to determine groundwater flow patterns. However, based on the topography of the spring area and the surface water drainage (northeast- southwest), the probable Thomas Spring aquifer recharge and spring drainage area was determined to cover about 350 acres (fig. 1). Although limited to surface characteristics

2

Figure 1.—Topography and assessment areas including drainage/recharge areas for Thomas and Glen Springs.

(such as drainage pathways), the identified drainage/recharge area offers some insight on the source of recharge waters and potential sources of contamination. The spring and drainage/recharge area are situated towards the southwest terminus of the Birmingham anticlinorium. Geologic units outcropping in the delineated drainage/recharge area are the Chickamauga Limestone, the Copper Ridge Dolomite of the Knox Group, the Knox Group undifferentiated, the Kimbrell member of Conasauga Formation, and the Conasauga Formation (fig. 2). The Chickamauga Limestone, a light- to dark-gray fossiliferous limestone, comprises the eastern-most extremity of the drainage/recharge area, and occurs as a narrow band along the Red Mountain ridge (fig. 2). In the southeastern part (Greenwood quadrangle), this formation was described to be in part fenestral, shaly, and stylonodular (Ward and Osborne, 2006). On the northeastern side of the drainage/recharge area (Bessemer quadrangle), the Chickamauga Limestone consists of variably fossiliferous

3 limestone, calcareous siltstone, calcareous shale, and minor greenish-gray bentonite with a laminated to bioturbated texture (Osborne and Rindsberg, 2001). The Knox Group in Alabama can consist of several units including the Late Cambrian Copper Ridge Dolomite and the Early Ordovician Chepultepec Dolomite, Longview Limestone, Newala Limestone, and Odenville Limestone. Most of the Thomas Spring recharge/drainage area is underlain by Copper Ridge Dolomite (Knox Group) outcrops in the northeastern part (the Bessemer quadrangle), consisting of light- to medium-gray, laminated to stromatolitic, to brecciated, finely crystalline cherty dolomite (fig. 2) A small part of the drainage/recharge area, in the southwestern part (in the Greenwood quadrangle), is underlain by undifferentiated Knox Group (fig. 2) (Raymond and others, 2003) (Osborne and Rindsberg, 2001). The Knox Group undifferentiated, consists of chert nodules and stringers, and beds within the light- to medium-gray, finely to medium crystalline dolomite (Ward and Osborne, 2006). The Kimbrell member of Conasauga Formation comprises a small part of the drainage/recharge area (fig. 2). However, the spring resides on the outcrop of this formation (fig. 2). In the Greenwood quadrangle, Kimbrell member consists of dark-gray micritic limestone and limey dolomite (Ward and Osborne, 2006). Some dolomite containing common to abundant dark-gray chert as platy and irregular stringers, nodules, and masses has also been identified in this member (Ward and Osborne, 2006). The Conasauga Formation, comprising a very small part of the drainage/recharge area in the Bessemer quadrangle (fig. 2), consists of interbedded dark-gray shale and micritic limestone in the lower part; dark-gray stylonodular, bioclastic, and oolitic limestone in the middle and upper parts; and dolomite in the most upper part (Osborne and Rindsberg, 2001). Based on geologic and physiographic settings, it can be inferred that Thomas Spring waters originate from the Valley and Ridge aquifer which in this area is characterized by Middle to Upper Cambrian sedimentary rocks. Geologic units capable of yielding adequate quantities of water in this area consist of dolomite, limestone, and chert with little primary porosity and permeability.

4

Figure 3.—Geology in the Thomas and Glen Springs area.

However, secondary porosity and permeability is characterized by leached fossils, bedding plane conduits, abundant fractures, and karst development. Surface-water discharge, flow directions, and groundwater recharge and migration pathways are influenced by karst terrains and complex folds and faults characteristic of the Valley and Ridge.

LAND-USE/LAND-COVER In recent decades, human-generated processes have been the dominant force in shaping landscape patterns in the United States. Adverse anthropogenic impacts on environment are mainly the result of inappropriate distribution and placement of industrial, commercial, agricultural, high intensity residential, and other human developments. Polluted effluents resulting from developed areas can degrade surface water and indirectly groundwater quality wherever there is a connection between the two entities. In order to identify potential contamination threats to Thomas Spring, the 2010 National Agricultural Statistics Service (NASS) U.S. Department of Agriculture (USDA)

5 Cropland Data Layer (CDL) for Alabama was employed. These data were incorporated into a Geographic Information System (GIS) and ten Level II land-use/land-cover (LULC) classes, depicted in figure 3, were identified for the Five Mile Creek-Valley Creek Watershed that include Thomas Spring and the probable drainage/recharge area. The classification includes crops, pasture/hay/grass, open water, developed/open space and low intensity, developed/medium and high intensity, barren, mixed forest, shrubland, woody and herbaceous wetlands, and grassland herbaceous (fig. 3). Most of the watershed area is dominated by forest and developed (open space and low intensity) land uses (fig. 3). In the drainage/recharge area residential uses make up approximately 76.3% and mixed forest accounts for 17.8% (fig. 3). The rest of the area (5.9%) is covered by, in order of decreasing coverage area, shrubland, pasture/hay/grass, grassland herbaceous, and crops. Anthropogenic contamination from sewage and septic sources and other sources of household or commercial origin is expected in areas like the Thomas Spring recharge/drainage area. SPRING DISCHARGE, PHYSICAL PROPERTIES, AND CHEMICAL COMPOSITION Groundwater samples were collected during two site visits in February and June, 2010 to identify seasonal changes on groundwater quality. Major element analysis was conducted on the sample collected in February. Physical parameters and stable isotope of hydrogen (δ18O) and oxygen (δD) samples were collected during both visits. Aqueous

samples for Chlorofluorocarbon (CFCs) and sulphur hexafluoride (SF6) groundwater dating were collected in June. Samples were collected in the spring pond from a boat using a Wildco Beta subsurface water sampler. The sampler was lowered into the deepest part of the spring where direct groundwater discharge was most likely to occur. The sampler was allowed to fill and was closed at sampling depth using a messenger and line. The source of groundwater and surface water in the Thomas Spring area is precipitation, which averages about 56 inches per year (Southeast Regional Climate Center, 2009). Availability and distribution of this water are controlled by processes, which include overland flow into streams and lakes, evaporation into the atmosphere, transpiration by vegetation, and infiltration into the subsurface as groundwater recharge. The surface hydrology of the project area is dominated by Valley Creek and tributaries characterized by flashy runoff over relatively impermeable Paleozoic rocks. The

6

Figure 3.--Land-use/land-cover for the Thomas and Glen Spring assessment area. groundwater system is characterized as relatively shallow, fractured, Paleozoic carbonate aquifers with widespread karst development. Groundwater yields are highly variable due to locally variable porosity and permeability that affect the water-bearing characteristics of aquifer. Thomas Spring discharge was measured downstream from the spring pond during four field assessments in 2009 and 2010. Discharge varied from 0.21 to 0.66 cubic feet per second (cfs) (135,360 to 426,240 gallons per day (gpd)). Spring recharge (groundwater) was estimated using a simple volumetric/area method. Recharge was estimated to be 10.3 inches per year or about 18 percent of annual precipitation. Physical properties assessed in-situ include temperature (T), hydrogen ion activity (pH), specific conductivity (SC), oxydo-reduction potential (ORP), and total dissolved solids (TDS). Hydrogen ion activity in an aqueous solution is controlled by interrelated chemical reactions that produce and consume hydrogen ions (Hem, 1985). The reaction of dissolved carbon dioxide with water is one of the most important mechanisms in establishing pH in natural-water systems. Spring water collected during the winter

7 sampling events exhibited slightly acidic pHs (6.5 and 6.2) and specific conductance characteristic of groundwater originating from carbonate aquifers like those described herein (474 and 454 microsiemens per centimeter [μS/cm]). Water collected during the summer sampling event had neutral pH (7.2), and slightly lower SC (390 μS/cm). Total dissolved solids (TDS) in the summer sample were 255 milligrams per liter [mg/L]). An increase in pH was noted between the winter and summer events. However, this is accompanied by a decrease in SC between the two seasons. While there is no positive correlation between pH and SC, the measured SC values suggest the presence of water- 2+ 2- rock reactions and limestone/dolomite dissolution that release Ca , Mg, and HCO3 ions in solution. This is further supported by the analytic results of the water sample collected 2+ 2- in January that reveal the presence of elevated Ca , Mg, and HCO3 concentrations (58.1, 21.1, and 272 mg/L, respectively). Physical and chemical parameters indicate that the spring source water originates from groundwater moving through carbonate-rock aquifers (for example, Knox Group and Conasauga Formation). More than 90 percent of the dissolved solids in groundwater can be attributed to eight ions: sodium (Na2+), calcium (Ca2+), potassium (K+), magnesium (Mg2+), sulfate 2- - - 2- (SO4 ), chloride (Cl ), bicarbonate (HCO3 ), and carbonate (Co3 ) (Fetter, 1994). The quantity of major cations and anions determines water types, which are generally used to characterize groundwater quality. The absence of water wells within the drainage/recharge area prevented a comprehensive characterization of groundwater flow and geochemical evolution. Due to this limitation, groundwater chemistry, collected by the GSA Groundwater Assessment Program in 2010, from four wells situated in Trussville has been used as surrogates, in an effort to evaluate the source of recharge to Thomas Spring. Groundwater geochemical evolution can be assessed by evaluating the major anion and cation concentrations. The major ionic composition of water collected from Thomas Spring, as illustrated by the 2+ - 2+ Piper and Stiff diagrams in figs. 5 and 6, is dominated by Ca , HCO3 , and Mg ions. Similar to the Piper diagram, the Stiff diagram reveals these three elements as the dominant ions that have roughly equal importance in the shape of the plot (fig. 6).

8 1000 223 272 454 232 261 436

100 58.1 21.1 18 12.8 9.1 7.9 7.1 7 10 6.2

1.3 1

0.08 0.05 0.1 0.04 Concentrations (mg/L) Concentrations 0.03

0.01 0.003

0.001

y e r ) 3 Cl ty ss K S /L Ba Ca pH DO F e Mg Na Pb O4 OD OC S TDS C T lkalinit HCO BAS A M onductivi Hardn 3 as NO3 C O N (mg Physical and chemical parameters nts

rfacta u S Figure 4. -- Thomas Spring physical and chemical parameters.

Similarly to groundwater samples collected from the Tuscumbia Fort Payne and the Bangor Limestone aquifers in the Trussville area, carbonate has not been detected in the Thomas Spring water but bicarbonate concentrations have relatively high concentrations (100 to 199 mg/L in Trussville samples and 272 mg/L in Thomas Spring) (fig. 4). Furthermore, as observed with the Trussville samples, there is good correlation - 2+ 2+ between pH, HCO3 , Ca , Mg , and SC in the Thomas Spring water indicating the - 2+ ongoing dissociation of carbonic acid into CO2 and HCO3 . The presence of Mg in higher concentrations (fig. 4) in the Thomas Spring sample indicates that dolomite (Mg- carbonates) contributes more solutes to groundwater feeding Thomas Spring compared to that in the investigated Trussville carbonate aquifers (figs. 5, 6). This agrees with the higher frequency of occurrence of dolomite in the aquifers present in the spring drainage/recharge area (see the geology section). Water hardness, defined as the content of metallic ions that react with sodium soaps to produce solid soaps or produce mineral scales when evaporated, was 232 mg/L

CaCO3 in Thomas Spring water, which according to the Durfor and Becker (1964)

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Figure 5.--Piper trilinear diagram showing major ion composition of water collected from Thomas Spring and Trussville wells (modified from Cook and Murgulet, 2011).

classification is classified as very hard. Groundwater in the investigated Trussville samples varies between moderate to hard (Cook and Murgulet, 2011).

- - The presence of Cl and NO3 concentrations (9.1 and 7.1 mg/L, respectively) (fig. 4) higher than the baseline concentrations in these groundwaters, indicates the presence of anthropogenic contamination. In the investigated drainage/recharge area agricultural lands are spatially limited. However, given the high percentage of residential land uses in this area, sources of groundwater and surface water contamination are probably - associated with sewer breakthrough. This is also confirmed by the Cl/NO3 ratio higher than one (1.3) (for example, higher chloride concentrations are generally associated with septic contamination) (Alhajjar and others, 1990). Furthermore, elevated levels of chemical oxygen demand (COD) and total organic carbon (TOC) were recorded in the

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Figure 6.-- Stiff diagrams for the selected Trussville groundwater samples (FW, W-7, P- 2, and W-10) and the Thomas Spring sample (ThS). spring (fig. 4), indicating the existence of water with abundant organic matter. The geochemical similarity of the Thomas Spring and Trussville samples indicates that the source water to this spring comes from groundwater hosted by carbonate aquifers such as those in the drainage/recharge area. Furthermore, the higher Mg2+concentration measured in the spring sample suggests that groundwater discharging at the investigated spring originates from a more localized origin as oppose to a regional one.

11 NUTRIENTS Excessive nutrient enrichment is a major cause of water-quality impairment. Excessive concentrations of nutrients, primarily nitrogen and phosphorus, in the aquatic environment may lead to increased biological activity, increased algal growth, decreased dissolved oxygen concentrations at times, and decreased numbers of species (Mays, 1996). Nutrient-impaired waters are characterized by numerous problems related to growth of algae, other aquatic vegetation, and associated bacterial strains. Blooms of algae and associated bacteria can cause taste and odor problems in drinking water and decrease oxygen concentrations to euthrophic levels. Toxins also can be produced during blooms of particular algal species. Nutrient-impaired water can dramatically increase treatment costs required to meet drinking water standards. Nutrients discussed in this report are nitrate (NO3-N) and phosphorus (P-total). Large amounts of algae were

NITRATE The U.S. EPA Maximum Contaminant Level (MCL) for nitrate in drinking water is 10 mg/L. However, there is currently no MCL for nitrate related to fish and wildlife.

Typical nitrate (NO3 as N) concentrations in streams vary from 0.5 to 3.0 mg/L. Concentrations of nitrate in streams without significant nonpoint sources of pollution vary from 0.1 to 0.5 mg/L. Streams fed by shallow ground water draining agricultural areas may approach 10 mg/L (Maidment, 1993). Nitrate concentrations in streams without significant nonpoint sources of pollution generally do not exceed 0.5 mg/L (Maidment, 1993). The critical nitrate concentration in surface water for excessive algae growth is 0.5 mg/L (Maidment, 1993). The 0.5 mg/L nitrate criterion was exceeded in the sample

collected from Thomas Spring, with a nitrate as nitrogen (NO3 as N) concentration of 1.58 mg/L. This excessive nitrate is manifested in the spring pond where large amounts of algae were observed during each field assessment.

PHOSPHORUS Phosphorus in streams originates from the mineralization of phosphates from soil and rocks or runoff and effluent containing fertilizer or other industrial products. The principal components of the phosphorus cycle involve organic phosphorus and inorganic

12 phosphorus in the form of orthophosphate (PO4) (Maidment, 1993). Orthophosphate is soluble and is the only biologically available form of phosphorus. Since phosphorus strongly associates with solid particles and is a significant part of organic material, sediments influence water column concentrations and are an important component of the phosphorus cycle in streams. The natural background concentration of total dissolved phosphorus is approximately 0.025 mg/L. Phosphorus concentrations as low as 0.005 to 0.01 mg/L may cause algae growth, but the critical level of phosphorus necessary for excessive algae is around 0.05 mg/L (Maidment, 1993). Although no official water-quality criterion for phosphorus has been established in the United States, total phosphorus should not exceed 0.05 mg/L in any stream or 0.025 mg/L within a lake or reservoir in order to prevent the development of biological nuisances (Maidment, 1993). In many water bodies, phosphorus is the primary nutrient that influences excessive biological activity. These streams are termed “phosphorus limited.” The 0.05 mg/L phosphorus criterion was not exceeded for total phosphorus at Thomas Spring as it was below the detection limit of 0.02 mg/L. METALLIC CONSTITUENTS The U.S. Environmental Protection Agency (USEPA) compiled national recommended water quality criteria for the protection of aquatic life and human health in surface water for approximately 150 pollutants. These criteria are published pursuant to Section 304(a) of the Clean Water Act (CWA) and provide guidance for states and tribes to use in adopting water quality standards (USEPA, 2012). The criteria were developed for acute (short-term exposure) and chronic (long-term exposure) concentrations. Table 5 shows metals and their recommended acute and chronic maximum concentrations. Numerous metals are naturally present in streams in small concentrations. However, toxic metals in streams are usually a result of man’s activities. Water samples collected from Thomas Spring were analyzed for selected metallic constituents. Table 1 shows recommended criteria for protection of aquatic life maximum concentrations and sample concentrations that exceed the. Metals detected in water samples can occur naturally as a result of the erosion of fine grained sediments. This is probably true of iron and zinc concentrations observed at Thomas Spring (table 1). Lead was the only other

13 metal on the criteria list that was detected. The lead concentration (2.7 µg/L) exceeded the chronic maximum concentration; however adequate data to determine chronic conditions are currently unavailable. Although not included in USEPA criteria, barium, magnesium, strontium, and rubidium were also detected. The former three are common in Alabama waters, however rubidium is rarely detected and is used in the chemical and electronics industries. Although not a metallic constituent, pH is included in table 5 due to its importance in the occurrence and solubility of metals. pH was slightly acidic, relative to the USEPA criteria.

Table1.-- Concentrations (µg/L) of metallic constituents detected in the water sample from Thomas Spring. USEPA Analyzed concentrations Metallic standards for protection of aquatic Sample ThS-1 constituent life (µg/L) (µg/L) Acute Chronic ThS-1 Aluminum 750 87 BDL Arsenic 340 150 BDL Cadmium 2.0 0.25 *BDL Chromium BDL 570 74 (Cr3) Copper 4.67 n/a BDL Cyanide 22 5.2 BDL Iron n/a 1,000 29.7 Lead 65 2.5 2.7 Mercury 1.4 0.77 BDL Nickel 470 52 BDL pH n/a 6.5-9.0 6.4 Selenium n/a 5.0 BDL Silver 3.2 n/a BDL Zinc 120 120 2.6 * BDL = below detection limit. **Chromium reported as total chromium and is assumed to be primarily Cr3.

14 ORGANIC CONSTITUENTS Organic compounds are commonly used in our society today. Frequently, these compounds appear in streams and groundwater aquifers. Many of these compounds are harmful to human health and to the health of the aquatic environment. Selected organic constituents including total organic carbon, oil and grease, and phenols were analyzed from sample ThS-1 collected at Thomas Spring in order to make a general determination of the presence of organic anthropogenic contaminants in the drainage/recharge area. Total organic carbon (TOC) analysis is a well-defined and commonly used methodology that measures the carbon content of dissolved and particulate organic matter present in water. Many water utilities monitor TOC to determine raw water quality or to evaluate the effectiveness of processes designed to remove organic carbon. Some wastewater utilities also employ TOC analysis to monitor the efficiency of the treatment process. In addition to these uses for TOC monitoring, measuring changes in TOC concentrations can be an effective surrogate for detecting contamination from organic compounds (e.g., petrochemicals, solvents, pesticides). Thus, while TOC analysis does not give specific information about the nature of the threat, identifying changes in TOC can be a good indicator of potential threats to a hydrologic system (USEPA, 2005). Typical TOC values for natural waters vary from 1 to 10 mg/L (Mays, 1996). The TOC concentration in sample ThS-1 was 12.8 mg/L, which exceeds the value for natural waters. Elevated TOC in Thomas Spring probably originates from contaminated urban runoff in the drainage/recharge area. Phenols are used in the production of phenolic resins, germicides, herbicides, fungicides, pharmaceuticals, dyes, plastics, and explosives (USGS, 1992-96). They may occur in domestic and industrial wastewaters, natural waters, and potable water supplies. The USEPA has set its water quality criteria, which states that phenols should be limited to 10,400 µg/L (micrograms per liter) (10.4 mg/L) in lakes and streams to protect humans from the possible harmful effects of exposure (USEPA, 2009). Phenols cause acute and chronic toxicity to freshwater aquatic life. Phenols are common in waters in urban environments; however phenol in sample ThS-1 was below the detectable limit. Oil and grease includes fatty matter from animal and vegetable sources and from hydrocarbons of petroleum origin. Due to the types of land use in the Thomas Spring

15 discharge/recharge area oil and grease was expected, however no oil and grease was detected. Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants are used as detergents, wetting agents, emulsifiers, foaming agents, and dispersants and are routinely deposited in numerous ways on land and into water systems, whether as part of an intended process or as industrial and household waste. Some of them are known to be toxic to animals, ecosystems, and humans, and can increase the diffusion of other environmental contaminants. Detection of surfactants is an indicator of the presence and movement of other contaminants into surface water or groundwater. Surfactants were detected in Thomas Spring discharge (0.04 mg MBAS/L). This is another indication of urban contamination of the spring. However, no maximum contaminant level has been established by the USEPA.

ISOTOPIC COMPOSITION As part of this investigation water samples from Thomas Spring were analyzed for anthropogenic and natural and stable isotopes such as chlorofluorocarbon (CFCs) and 18 sulphur hexafluoride (SF6) and oxygen (δ O), and hydrogen (δD), respectively. These analyses provide essential measurements to identify the environment from which groundwater originates and constrains the period of time during which recharge occurred. Hydrogen and oxygen isotopes are best used in tracing sources of groundwater since they integrally compose the water molecule (Cook and Herczeg, 1999). These measurements provide information about recharge and discharge processes, and are successfully used in delineating recharge areas (Cook and Herczeg, 1999). Ocean derived atmospheric waters are depleted in heavy isotopes (18O and 2H) relative to the standard mean ocean water (SMOW). δ18O and δD isotopic composition of precipitation depends on the fraction of water remaining in the air mass from which the rain or snowfall is derived (Ellis and Mahon, 1977). Abundances of oxygen and hydrogen isotopes are measured relative to an accepted standard SMOW or Vienna SMOW (VSMOW) (Craig, 1961). The isotopic composition of the water is expressed in terms of the relative difference of the ratio of heavy to light isotopes in the sample compared to that of SMOW. The resulting compositional values are stated as positive (enriched) or

16 negative (depleted) percentages relative to VSMOW. The average isotopic variation of global precipitation is defined by a linear regression of δD as a function of δ18O. Craig and Gordon (1965) estimated the mean worldwide isotope composition of precipitation to be δ18O = -4 per mil (‰) and δ D = -22 ‰. The worldwide average correlation between hydrogen and oxygen isotope ratios in precipitation is given by the equation δD = 8 δ18O + 10‰, called the Global Meteoric Water Line (GMWL). Groundwater samples for the oxygen and hydrogen stable isotope analyses were collected during three site visits, November 2009 (ThS1), January (ThS2), and June (ThS3) 2010. The δD and δ18O values ranged between -26.6 to -24.5 ‰ and -5.1 to -4.7 ‰, respectively. The heavier δD and δ18O values were recorded in samples collected during the winter (November 2009-January 2010) sampling events (-25.3 and -24.5‰ and -4.8 and -4.7‰, respectively). More depleted isotope signatures were measured in the summer sample (-26.6 and -5.1‰, respectively). The weighted annual (3-year) δ18O and δD mean values of precipitation collected from Tuscaloosa, Alabama are -4.7‰ and - 24.3‰, respectively (Lambert and Aharon, 2009). Water samples collected from Thomas Spring during winter are very similar to those reported by Lambert and Aharon (2009). Summer values are slightly depleted. The summer isotope signature is very similar to the Trussville values collected during the same sampling event (fig. 7). The closer similarity of the winter samples isotope signature to the meteoric signature (TLMWL) may indicate the greater precipitation input to surface water (Thomas Spring) during the winter. Some evaporation may be associated with sample ThS1 as it plots below the TLMWL (fig. 7). On the other hand, during the summer when precipitation rates are lower, groundwater has a greater input to the spring pond. Therefore, samples collected during the winter event may be more representative of mixed groundwater and meteoric water. However, a limited input of meteoric water can be assumed given the high mineral content of water collected in January (see geochemistry section). Apparent ages estimated using both

CFCs and SF6 dating tools can be affected by factors such as introduced air, recharge temperature, and degradation of CFCs. In high organic content environments CFCs are degraded by microbial activity. Furthermore, microbial degradation of CFCs takes place in anoxic waters with sulfate-reduction or methanogenesis. CFC-11 is the most degraded

17 CFCs compound. Degradation leads to a decrease in concentration and age underestimation (Kazemi and others, 2006).

Age-dating using CFCs and SF6 for Thomas Spring was not successful, due to unknown sources of contamination that resulted in sample super saturation with respect to atmospheric equilibrium and degradation of dating compounds. The presence of nitrate, surfactant, COD, and TOC contents in the spring water are all indicators of

contamination that make CFCs and SF6 age dating impossible. However, correlation of these data with Trussville age data determined during the same investigation time and using the same tools helps derive an approximate age for groundwater discharging at Thomas Spring. Physical parameters and ionic concentrations characteristic of Thomas Spring water are very similar to those recorded for the Bangor Limestone waters in the

Tuscaloosa LMWL: -21 δD = 7δ18O + 9‰

-23 TP-2

-25 Trussville and Thomas TP-1 Spring water: δD = 6δ18O + 2‰ TP-3 -27

-29 D (‰ VSMOW) D (‰ δ

18 -31 GMWL: δD = 8δ O + 10‰

-33

-35 -6 -5.8 -5.6 -5.4 -5.2 -5 -4.8 -4.6 -4.4 -4.2 -4

δ18O (‰ VSMOW)

Figure 7.-- Cross plot of the δD and δ18O isotope data relative to the GMWL and TLMWL.

18 Trussville area (Cook and Murgulet, 2011). Groundwater ages in the Bangor Limestone aquifer are approximately 19±2 years (Cook and Murgulet, 2011). Regression models using calcium concentrations and available groundwater age data have been used to project groundwater ages for samples where age-data were not available (Robinson, 2004). This method requires knowledge of the hydrologic settings from which samples were collected. For example, projection of groundwater ages has to be conducted only for aquifers similar in nature. Using the age-data and calcium concentration for the Bangor Limestone aquifer (18.5±2 years and 60 mg/L) and the calcium concentrations recorded at Thomas Spring (58.1 mg/L), groundwater age at the spring was estimated to be approximately 18±2 years. Based on the two age-dates and specific conductivities, direct measurements of the dissolved solids in solution, for the Bangor Limestone (18.5±2 and 19.5±2 and 340 and 282 μS/cm) and the specific conductivity recorded at Thomas Spring (390 μS/cm), groundwater discharging at Thomas Spring may be roughly 17.7±2 years. Therefore, using both, calcium concentrations and specific conductivities, the average age of groundwater discharging at Thomas Spring is approximately 18 years. These estimates are determined assuming that carbonate dissolution contributes most of the ions in solution and the dissolution rates are similar on both aquifers. REFERENCES CITED Alhajjar, B.J., Chesters, G., Harkin, J.M., 1990, Indicators of chemical pollution from septic systems, Ground Water 28:559–568. Cook P.G. and Herczeg A.L. (1999) Environmental Tracers in Subsurface Hydrology. Kluwer Academic Press, Boston, 529 pp. Cook, M. R., and Murgulet D., 2011, Groundwater hydrogeologic characterization, preservation, and development in the Trussville area, Jefferson and St. Clair Counties: Geological Survey of Alabama Open-file Report- in review. Craig, H., 1961, Standard for reporting concentrations of deuterium and oxygen-18 in natural water: Science, v. 133, p. 1833-1834. Craig H. and Gordon L. I. (1965) Deuterium and oxygen 18 variations in the ocean and the marine atmosphere. Marine Geochemistry, Narragansett Marine Laboratory, University of Rhode Island, V. 3, 277-374.

19 Durfor, C. N., and Becker, Edith, 1964, Public water supplies of the 100 largest cities in the United States, 1962, U.S. Geological Survey Water-Supply Paper 1812, 364 p. Ellis, A. J., and Mahon, W. A. J., 1977, Chemistry and geothermal systems: Academic Press, New York, 75 p. Fetter, C. W., 1994, Applied hydrogeology, Third Edition: New York, New York, Macmillan, Inc., 691 p. Hem, J. D., 1985, Study and interpretation of the chemical characteristics of natural waters (3rd ed.): U.S. Geological Survey Water Supply Paper 2254, 264 p. Kazemi, G.A., Lehr, J.H., Perrochet, P., 2006, Groundwater Age. John Wiley & Sons, New York. Lambert, W. J., and Aharon, P., 2009, Oxygen and hydrogen isotopes of rainfall and dripwater at DeSoto Caverns (Alabama, USA): Key to understanding past variability of moisture transport from the Gulf of Mexico; Geochimica et Cosmochimica Acta 74 (2010) 846–861. Osborne, W.E. and Rindsberg, A.K., 2001, Geologic Map of the Bessemer 7.5-Minute Quadrangle, Jefferson County, Alabama, Quadrangle Series Map QSM-20-2001, Geological Survey of Alabama. URL: http://www.ogb.state.al.us/gsa/QS_results.aspx?PubID=QS20 Robinson, J. L., 2004, Age and source of water in springs associated with the Jacksonville Thrust Fault Complex, Calhoun County, Alabama: U.S. Geological Survey Scientific Investigation Report 2004-5145, 27 p. Sapp, C. D., and Emplaincourt, Jacques, 1975, Physiographic regions of Alabama: Alabama Geological Survey Special Map 168. Southeast Regional Climate Center, 2009, Historical Climate Summaries for Alabama, URL http://www.sercc.net/climateinfo/historical/historical_al.html, accessed February 11, 2009. Ward, E.W. and Osborne, W.E., 2006, Geologic Map of the Greenwood 7.5-Minute Quadrangle, Jefferson and Shelby Counties, Alabama, Quadrangle Series Map QSM-44-2006, Geological Survey of Alabama. URL: http://www.ogb.state.al.us/gsa/QS_results.aspx?PubID=QS44

20 U.S. Geological Survey, 1999, National Elevation Dataset (NED) Digital Elevation Model (DEM); URL: http://seamless.usgs.gov/

21 GEOLOGICAL SURVEY OF ALABAMA 420 Hackberry Lane P.O. Box 869999 Tuscaloosa, Alabama 35486-6999 205/349-2852

Berry H. (Nick) Tew, Jr., State Geologist

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