NATIONAL WATER-QUALITY ASSESSMENT PROGRAM Quality of Shallow Ground Water in Areas of Recent Residential and Commercial Development in Salt Lake Valley, Utah, 1999 Great Salt Lake WYOMING Basins Bear Significant Findings Lake study IDAHO • The nitrate concentration in water sampled from 26 of the 30 monitoring wells was higher area UTAH than an assumed background level of 3 mg/L. • At least one of the herbicides, atrazine, prometon, simazine, or tebuthiuron was detected in water sampled from 25 of the 30 monitoring wells. Great Salt Lake Salt • Chloroform, most likely from chlorinated public-supply water that has recharged the Lake shallow aquifer, was detected in water sampled from 27 of the 30 monitoring wells. City • Tetrachloroethene was detected in water sampled from 16 of the 30 monitoring wells with 1 concentration greater than the U.S. Environmental Protection Agency Utah 5 µg/L maximum contaminant level for drinking water. Lake

Introduction 111°37'30" Residential and commercial develop- ment of about 80 square miles that pri- 112°15' Jordan marily replaced undeveloped and agricul- Great Salt tural areas occurred in Salt Lake Valley, 80 WASATCH RANGE Lake Utah, from 1963 to 1994. The effects of 40°45' Tailings ponds human activities on the quality of shallow SALT LAKE VALLEY 15 ground water in the recently developed River areas were studied by the U.S. Geological Survey (USGS) as part of the National OQUIRRH MOUNTAINS Water-Quality Assessment (NAWQA)

program. The land-use study consisted 215 of 30 monitoring wells installed and sam- pled in 1999 in residential/commercial areas where shallow ground water has the potential to move to a deeper public- supply aquifer. The water samples were analyzed for major ions, nutrients, pesti- Salt Lake County cides, volatile organic compounds 40°30' Area of study shown in figure 2 (VOCs), trace elements, and radon. The occurrence of nitrate, pesticides, and Approximate limit of basin-fill VOCs in water sampled from these wells material in Salt Lake Valley can serve as an indicator of water affected Base from U.S. Geological Survey digital line graph data, 0 3 6 MILES 1:100,000 , 1979 and 1980 by human activities at land surface. This Universal Transverse Mercator projection, Zone 12 0 3 6 KILOMETERS report describes the nitrate, pesticide, and Figure 1. Location of residential/commercial land-use study area in Salt Lake Valley, Utah. VOC data collected during the study. dan River, which flows north along the The population in Salt Lake County Description of Study Area axis of the valley and discharges into in 1999 was about 850,000 (U.S. Census Salt Lake Valley covers almost 500 Great Salt Lake. The climate in Salt Lake Bureau, written commun., 2000) and is square miles and contains the Salt Lake Valley is semiarid, with a normal precip- growing rapidly. The population almost City metropolitan area (fig. 1). It is bound itation rate of about 12 to 20 inches per doubled between 1963 and 1994, corre- on the east by the Wasatch Range and on year. Lawns and gardens in the valley sponding to areas with recent residential the west by the Oquirrh Mountains. require irrigation to supplement precipi- and commercial development in the valley Mountain streams discharge into the Jor- tation during the growing season. (fig. 2). The cities of Sandy and West

U.S. Department of the Interior USGS Fact Sheet 106Ð00 U.S. Geological Survey July 2000 South Salt Lake EXPLANATION West Jordan have experienced substantial Valley Approximate limit of basin- growth. An adequate supply of water that City fill material Discharge area is suitable for domestic use is one of the Taylorsville most important factors in sustaining the Primary recharge area current population and in allowing for Murray Secondary recharge area continued economic growth in Salt Lake Recent residential/com- mercial land use Valley. Area that meets recent Cottonwood West Jordan residential/commercial Ground Water in Salt Lake Heights land-use study criteria 2 Valley Nitrate A generalized model of the saturated Nitrate concentration, in milligrams per liter basin-fill material in Salt Lake Valley South Jordan Less than 0.05 consists of a relatively deep unconfined 0.05– 3.0 aquifer near the mountain fronts that Sandy 3.0 – 5.0 5.0 – 10.0 becomes confined toward the center of 10.0 – 13.3 the valley by interbedded, discontinuous layers of silt and clay (fig. 3). Overlying Riverton Draper Nitrate this confined aquifer is a shallow, gener- ally unconfined aquifer. The primary South Salt Lake West recharge area for the deeper aquifers is Valley Atrazine City near the mountain fronts where there are Atrazine concentration, in no substantial layers of fine-grained ma- Taylorsville micrograms per liter Less than 0.001 terial to impede movement of water. Murray 0.001–0.020 Downward leakage of water from the 0.020–0.100 shallow aquifer to the deeper confined 0.100–1.00 1.00 –1.58 aquifer is possible where a downward Cottonwood gradient exists and confining layers are West Jordan Heights thin, absent, or discontinuous. These con- ditions can exist in the secondary recharge area. The shallow, generally unconfined South Jordan aquifer is susceptible to contamination Sandy from activities related to land use because of its proximity to land surface. Water from this aquifer is not currently used for Riverton drinking. The deeper unconfined aquifer Draper Atrazine also is vulnerable because of a lack of South Salt Lake Tetrachloroethene confining layers that can impede the West Tetrachloroethene concentration, downward movement of contaminated Valley in micrograms per liter City ground water. Water quality in the deeper Less than 0.1 Taylorsville 0.008– 0.1 (estimated values) confined aquifer can be degraded by the 0.1 – 1.0 secondary recharge of contaminated water Murray 1.0 – 5.0 from the shallow and deeper unconfined 5.0 – 7.8 aquifers. The deeper unconfined and con- fined aquifers in Salt Lake Valley are Cottonwood West Jordan Heights used extensively for public supply. More than half of the population in the valley receives ground water for household use.

0 2 4 MILES Volatile organic compounds have been

South Jordan 0 2 4 KILOMETERS recently detected in water pumped from public-supply wells completed in deeper Sandy N aquifers. These wells are primarily in urban/residential areas within the valley (Thiros, 2000). Tetrachloroethene was Riverton Draper Tetrachloroethene detected in water from seven public- supply wells in Salt Lake and Davis Coun- Figure 2. Distribution of nitrate, atrazine, and tetrachloroethene concentration in water sampled ties. Contamination of drinking-water from monitoring wells in Salt Lake Valley, Utah. supplies from VOCs and pesticides is a human health concern because many are EXPLANATION toxic and are known or suspected human Direction of ground-water movement carcinogens (U.S. Environmental Protec- Primary tion Agency, 1996). These compounds recharge are difficult and expensive to remove area Secondary from ground water. Additional data and recharge interpretation are needed to determine area Discharge the occurrence, distribution, and sources area of VOCs in the shallow aquifer and the Perched deeper drinking-water supply aquifers in Deeper water unconfined Salt Lake Valley. aquifer

Deeper Site Selection and Well confined Installation aquifer Shallow Study sites were selected with a com- unconfined aquifer puterized, stratified random selection Water level in shallow process (Scott, 1990). It identified 41 unconfined sites in Salt Lake Valley that met the study aquifer criteria: (1) location in residential and Fine-grained Consolidated material rock commercial areas developed from 1963 to 1994; (2) 75 percent of a 500- meter Water level in Shallow Basin-fill material of deeper aquifers confining layer Tertiary age circular buffer around the site contains targeted land use; (3) a downward gradient Figure 3. Generalized block diagram showing the basin-fill ground-water flow system, exists between the shallow and deeper Great Salt Lake Basins Study unit. (Modified from Hely and others, 1971.) aquifers; and (4) a minimum distance of 1 kilometer exists between each site field (Koterba and others, 1995) and in unconfined aquifers, it was less than 1 (Squillace and Price, 1996). Areas devel- the laboratory to evaluate and ensure the mg/L (110 analyses). oped after 1994 were not included in this reliability of the data. Nitrate concentration in water sampled study because of the time necessary for Chemicals Detected in Shallow from 26 of the 30 monitoring wells (86.7 new construction to affect the ground- percent) was higher than an assumed water system. Areas developed before Ground Water background level of 3 mg/L, indicating 1963, such as downtown Salt Lake City, Nitrate a possible human influence. Concentra- were also excluded because of a greater tions ranged from less than 0.05 mg/L to Although nitrate as nitrogen can occur potential for the land use to have changed 13.3 mg/L (fig. 2). The median nitrate naturally in ground water, elevated con- with time. concentration for the 30 samples was 6.8 centrations in urban areas are typically Monitoring wells were installed at 30 mg/L. caused by human activities. Some of the of the 41 sites according to NAWQA potential sources of nitrate in ground The U.S. Environmental Protection protocols (Lapham and others, 1995) (fig. water include nitrate leaching from areas Agency’s (EPA) maximum contaminant 2). Depth of monitoring wells ranged where manure has been applied, leaking level (MCL) for nitrate in drinking water from 23 to 153 feet, and the wells were or improperly functioning septic systems (10 mg/L) was exceeded in water from 3 completed with a 10-foot length of screen. and sewer pipes, and nitrogen-based fer- of the 30 wells (10 percent). Water from The top of the screened interval generally tilizers applied to lawns and gardens. 19 wells had concentrations greater than was about 5 feet below the water table. Background nitrate concentrations in 5 mg/L (63.3 percent). High nitrate con- One site was completed with two wells ground water from areas not associated centrations can cause methemoglobinemia to determine water-quality variations with with agricultural practices commonly are or “blue-baby syndrome” in small chil- depth in the shallow aquifer. The water less than 2 to 3 milligrams per liter (mg/L) dren and results from the reduced oxygen- level at another site dropped below the as nitrogen (Halberg and Keeney, 1993, carrying capacity of blood after the body bottom of the well and no water sample p. 316). Some existing nitrate data for converts nitrate to nitrite. was collected. Water levels in the wells ground water in the Great Salt Lake Basins ranged from about 5 to 135 feet below Pesticides study area are available from the USGS land surface. National Water Information System data- Nationally, pesticide results are avail- Protocols for parts-per-billion-level base. The median nitrate concentration able from 41 NAWQA land-use studies ground-water sampling documented by in water located in urban/residential areas completed during 1993Ð95. Pesticide Koterba and others (1995) were followed sampled from wells less than 150 feet compounds in shallow ground water were in the collection and processing of the deep was 1.1 mg/L (71 analyses); in water commonly detected nationally in both samples. The USGS National Water Qual- sampled from wells greater than 150 feet agricultural (56.4 percent; 813 sites) and ity Laboratory analyzed the samples. A deep, generally completed in the deeper urban (46.6 percent; 221 sites) settings quality-control program was used in the- (Kolpin and others, 1998). The most fre- quently detected pesticides in shallow (Zaugg and others, 1995). The mini- grams per liter (µg/L), the most frequently ground water in urban areas were prome- mum reporting level (MRL) for each detected pesticides were atrazine (36.7 ton, atrazine, deethylatrazine (DEA), si- compound indicates relative analytical percent) and prometon (20 percent). All mazine, and tebuthiuron, all herbicides. precision and detection sensitivity, but of the pesticide concentrations measured These were also the most frequently de- some concentrations were reported in were less than MCLs or health advisories tected pesticides in the Salt Lake Valley concentrations below the MRL if the for drinking water (table 1). Water sam- study (table 1) with at least 1 compound identification criteria for the method ples from two monitoring wells had con- detected in water sampled from 25 of the were met. Concentration values for centrations greater than 1 µg/L of atrazine 30 monitoring wells. Prometon, atrazine, detections below MRLs are designated but less than the MCL of 3 µg/L (fig. 2). simazine, and tebuthiuron are used to as estimated values. Overall, the MRL The water level in one of these wells is control weeds and other vegetation pri- for pesticides analyzed for the greater than 130 feet below land surface. marily along roads, driveways, rights-of- NAWQA program are lower than those The presence of pesticides in shallow way, parking lots, and utility corridors, of analyses done for regulatory purpos- ground water from residential/commercial and all, except for prometon, may only es. areas indicates relatively fast movement be used by licensed applicators. Nation- The most frequently detected pesti- from the land surface to the shallow aqui- ally, insecticides were seldom detected cides in water sampled for the study fer and is of concern because of the po- in ground water in urban areas. were atrazine (76.7 percent), prometon tential for movement to the underlying The water samples were analyzed for (50 percent), simazine (43 percent) and drinking-water-supply aquifer. 86 pesticides by using capillary column tebuthiuron (13.3 percent). At a com- Atrazine was detected in water sam- gas chromatography/mass spectrometry mon detection threshold of 0.10 micro- pled from 23 wells (table 1). All of the

Table 1. Summary of pesticides and volatile organic compounds detected in water sampled from 30 residential/commercial area monitoring wells in Salt Lake Valley, Utah, 1999

[Units in micrograms per liter; Maximum Contaminant Level is the U.S. Environmental Protection Agency established drinking water standard (U.S. Environmental Protection Agency, 1996); Lifetime Health Advisory is defined as the concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effect over a lifetime of exposure within a specified margin of safety (U.S. Environmental Protection Agency, 1996); -, no applicable standard; E, estimated value]

Minimum Maximum Lifetime Pesticide Trade name(s) Predominant use Number of Maximum reporting Contaminant Health or abbreviation detections concentration level Level Advisory

Atrazine AAtrex restricted use herbicide 23 1.58 0.001 3 3 Deethylatrazine DEA, Desethylatrazine degradation product of atrazine 22 .320 E .002 - - Prometon Pramitol general use herbicide 15 .518 .018 - 100 Simazine Aquazine, Princep restricted use herbicide 13 .027 .005 4 4 Tebuthiuron Brush, Spike, Perflan restricted use herbicide 4 .120 .010 - 500 Diazinon D-Z-N restricted use insectide 1 .002 E .002 - .6 Malathion Cythion general use insectide 1 .006 .005 - 200 P,P' DDE DDE degradation product of DDT 1 .002 E .006 - .1

Volatile Minimum Maximum Lifetime organic Alternative name Predominant use Number of Maximum reporting Contaminant Health compound or abbreviation detections concentration level Level Advisory

Chloroform Trichloromethane solvent, chlorination byproduct 27 2.41 0.052 100 - Bromodichloromethane Dichlorobromomethane chlorination byproduct 17 .508 .048 100 - Tetrachloroethene Tetrachloroethylene, PCE solvent 16 7.85 .100 5 - 1,1,1-Trichloroethane Methyl chloroform, TCA solvent 15 .224 .032 200 200 Dichloromethane Methylene chloride solvent 6 .319 E .380 5 - Trichloroethene Trichloroethylene, TCE solvent 5 1.54 .038 5 - m+p Xylene 1,3 + 1,4-Dimethylbenzene gasoline aromatic hydrocarbon 4 .081 E .060 10,000 10,000 Carbon disulfide - naturally occurring, organic synthesis 3 .096 E .370 - - Benzene - gasoline aromatic hydrocarbon 2 .006 E .100 5 - Ethylbenzene Ethylbenzol gasoline aromatic hydrocarbon 2 .018 E .030 700 700 Toluene Methylbenzene gasoline aromatic hydrocarbon 2 .010 E .050 1,000 1,000 Trichlorofluoromethane Freon 11, CFC 11 refrigerant, aerosol propellant 2 .087 E .090 - 2,000 1,1-Dichloroethene 1,1-DCE organic synthesis 2 .045 E .044 7 7 1,2,4-Trimethylbenzene Psuedocumene organic synthesis 2 .032 E .056 - - Methyl tert-butyl ether MTBE fuel oxygenate 1 .123 E .170 - 20-40 vatives, dry-cleaning dential areas of Salt Lake Valley. Chlo- agents, pesticides, fer- roform and bromodichloromethane are tilizers, cosmetics, and byproducts of chlorinated ground and refrigerants. Potential surface water reacting with organic ma- sources of VOCs to terial. ground water are direct Tetrachloroethene (perchloroethylene, industrial and waste- PCE), primarily used as a dry cleaning water discharges, infil- agent and solvent, was detected in water tration of accidental sampled from 16 wells (table 1). Although spills, leaking under- the median concentration of PCE for sam- ground storage tanks, ples was less than the minimum reporting stormwater runoff, and level of 0.10 µg/L, water from four wells atmospheric deposition had concentrations greater than 1 µg/L. of vehicle and industrial These wells are all in the northwestern emissions. The U.S. part of the study area (fig. 2). The maxi- Environmental Protec- mum PCE concentration measured was tion Agency (1996) has 7.85 µg/L, greater than the MCL in drink- established MCLs in ing water of 5 µg/L. It is not known if drinking water for 27 the PCE detected in the ground water in VOCs because of hu- Area surrounding a residential/commercial land-use study this area is from a point source or is part monitoring well in Salt Lake Valley. man health concerns. of a larger, diffuse plume. NAWQA urban Trichloroethene (TCE) and 1,1,1- wells with atrazine concentrations greater land-use studies collected about 300 µ trichloroethane (TCA) are commonly used than 0.1 g/L are located on the west side shallow ground water VOC samples as solvents (table 1). Trichloroethene was of Salt Lake Valley (fig. 2). This may be during 1993Ð95 from study units locat- detected in water sampled from five wells; the result of a particular land use, aquifer ed across the country (Volatile Organic the maximum concentration was 1.54 properties such as recharge rate or trans- Compound National Synthesis Project, µg/L. 1,1,1-tricloroethane was detected missivity, or a combination of factors. U.S. Geological Survey, written com- in water sampled from 15 wells; the max- Deethylatrazine is a degradation product mun., 1998). Nationally, the most fre- imum concentration was 0.22 µg/L. The of atrazine and was detected in all but quently detected VOCs were chloro- widespread occurrence of VOCs generally one of the samples that contained atrazine. form, methyl tert-butyl ether (MTBE, used as solvents in the shallow unconfined Prometon was detected in water sam- an additive to gasoline), tetrachloroet- aquifer in mostly residential areas may pled from 15 wells (table 1) and in 6 of hene, and trichloroethene. At a national be the result of their presence in household the 11 samples collected from wells on scale, these compounds were generally products used for cleaning, painting, car the east side of the valley. The maximum detected at low concentrations that were care, and other uses. µ almost always below MCLs or health concentration of 0.518 g/L is much less Methyl tert-butyl ether (MTBE) was than the health advisory for drinking advisories for drinking water. µ detected near the minimum reporting level water of 100 g/L. Prometon is registered Detection of many VOCs is the re- in water from one well (table 1). This for use by homeowners to control vege- sult of improved analytical methods compound is used to oxygenate gasoline tation. Nationally, it was the most fre- that allow measurement of lower con- to improve combustion and reduce air- quently detected herbicide in ground centrations (Conner and others, 1998). quality degradation. Ethanol is the primary water at urban sites sampled during The most frequently detected VOCs in oxygenate used in gasoline in the area 1993Ð95 for the NAWQA program water sampled for the study were chlo- but MTBE is used as an octane booster. (Kolpin and others, 1998). roform (90 percent), bromodichlo- Because of the high solubility of MTBE Simazine was detected in water sam- romethane (56.7 percent), tetrachloro- pled from 13 wells with a maximum ethene (53.3 percent), and 1,1,1- concentration of 0.027 µg/L (table 1). Of trichloroethane (50 percent) (table 1). the 13 detections, 12 were from samples At a common detection threshold of in the northwestern part of the area and 0.10 µg/L, the most frequently detected 1 from the eastern part. VOCs were chloroform (70 percent), bromodichloromethane (30 percent), Volatile Organic Compounds tetrachloroethene (26.7 percent), and Volatile organic compounds are car- 1,1,1-trichloroethane (10 percent). bon-containing chemicals that readily The widespread occurrence of chlo- evaporate at normal air temperature and roform and bromodichloromethane in pressure. They are contained in many shallow ground water is likely a result manufactured products such as gasoline, Thiros © 2000 Photo credit: Susan of disinfected public-supply water used Drill rig installing a monitoring well in a paints, adhesives, solvents, wood preser- to irrigate lawns and gardens in resi- residential area. Geological Survey Water-Resources In- vestigations Report 00-4043, 19 p. U.S. Environmental Protection Agency, 1996, Drinking water regulations and health advisories: Washington, D.C., Office of Water, EPA 822-B-96-002, 16 p. Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg, K.M., 1995, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-- Determination of pesticides in water by C-18 solid-phase extraction and capillary- column gas chromatography/mass spec- trophotometry with selected-ion monitor- ing: U.S. Geological Survey Open-File

Photo credit: Susan Thiros © 2000 Photo credit: Susan Report 95Ð181, 49 p. Golf course and residential development on west side of Salt Lake Valley, with Wasatch Range in background. Acknowledgments in water, atmospheric washout in urban Kolpin, D.W., Barbash, J.E., and Gilliom, The USGS thanks the landowners, and areas may be the source of low concen- R.J., 1998, Occurrence of pesticides in officials of municipalities, and Salt Lake trations in ground water (Squillace and shallow ground water of the United States: County who allowed USGS personnel others, 1996). Initial results from the National Water- access to their properties for the purpose Quality Assessment Program: Environ- of installing and sampling monitoring Implications mental Science and Technology, v. 32, no. wells. The presence of nitrate, pesticides, and 5, p. 558Ð566. volatile organic compounds in shallow Koterba, M.T., Wilde, F.D., and Lapham, National Water-Quality ground water indicates relatively rapid W.W., 1995, Ground-water data-collection Assessment Program protocols and procedures for the National movement of water from land surface and The Great Salt Lake Basins study unit therefore, vulnerability to contamination Water-Quality Assessment Program: col- lection and documentation of water-quality is 1 of 50 study units involved in the from these and other compounds. The samples and related data: U.S. Geological USGS NAWQA program. The goals of deeper confined aquifer used for public Survey Open-File Report 95Ð399, 113 p. the NAWQA program are to describe the supply in Salt Lake Valley may also be Lapham, W.W., Wilde, F.D., and Koterba, status and trends in the quality of the vulnerable because the potential exists for M.T., 1995, Ground-water data-collection Nation’ s ground- and surface-water re- water to move downward from the shallow protocols and procedures for the National- sources and to gain a better understanding aquifer. More information is needed on Water Quality Assessment Program: se- of the natural and human factors that the movement of ground water and on the lection, installation, and documentation affect the quality of these resources. The occurrence and distribution of pesticides of wells, and collection of related data: study design balances the unique assess- and volatile organic compounds in the U.S. Geological Survey Open-File Report ment requirements of individual hydro- deeper drinking-water supply aquifers. 95Ð398, 69 p. logic systems with a nationally consistent Scott, J.C., 1990, Computerized stratified References design structure that incorporates a multi- random site-selection approaches for de- scale, interdisciplinary approach. Conner, B.F., Rose, D.L., Noriega, M.C., sign of ground-water-quality network: Murtagh, L.K., and Abney, S.R., 1998, U.S. Geological Survey Water-Resources Information on the NAWQA Methods of analysis by the U.S. Geological Investigations Report 90Ð4101, 109 p. Program can be obtained from: Survey National Water Quality Squillace, P.J., Pankow, J.F., Korte, N.E., and Great Salt Lake Basins NAWQA Chief Laboratory—Determination of 86 volatile Zogorski, J.S., 1996, Environmental be- organic compounds in water by gas chro- havior and fate of methyl tert-butyl ether U.S. Geological Survey matography/mass spectrometry, including 2329 Orton Circle (MTBE): U.S. Geological Survey Fact Salt Lake City, UT 84119-2047 detections less than reporting limits: U.S. Sheet FSÐ203Ð96. Geological Survey Open-File Report http://ut.water.usgs.gov 97Ð829, 78 p. Squillace, P.J., and Price, C.V., 1996, Urban land-use study plan for the National Water- Halberg, G.R., and Keeny, D.R., 1993, Nitrate, Quality Assessment program: U.S. Geo- Additional information on health ef- in Alley, W.M., ed., Regional ground-water logical Survey Open-File Report 96Ð217, fects of nitrate, pesticides, or VOCs in quality: New York, Van Nostrand Reinhold, 19 p. drinking water and drinking-water regu- p. 316. Thiros, S.A., 2000, Analysis of nitrate and lations can be obtained by calling the Hely, A.G., Mower, R.W., and Harr, C.A., volatile organic compound data for ground EPA Safe Drinking Water Hotline at 1971, Water resources of Salt Lake County, water in the Great Salt Lake Basins, Utah, 1Ð800Ð426Ð4791. Utah: Utah Department of Natural Re- Idaho, and Wyoming, 1980Ð98, National sources Technical Publication 21, 244 p. Water-Quality Assessment Program: U.S. — By S.A. Thiros USGS Fact Sheet FSÐ106Ð00 Printed on recycled paper July 2000