Temporal and Spatial Variations in the Subsurface

Louisiana State University LSU Digital Commons LSU Master's Theses Graduate School 2013 Temporal and spatial variations in the subsurface salinity of Lake Charles, Louisiana : an investigation of saline sources Alexandria Suding Louisiana State University and Agricultural and Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_theses Part of the Earth Sciences Commons Recommended Citation Suding, Alexandria, "Temporal and spatial variations in the subsurface salinity of Lake Charles, Louisiana : an investigation of saline sources" (2013). LSU Master's Theses. 948. https://digitalcommons.lsu.edu/gradschool_theses/948 This Thesis is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Master's Theses by an authorized graduate school editor of LSU Digital Commons. For more information, please contact [email protected]. TEMPORAL AND SPATIAL VARIATIONS IN THE SUBSURFACE SALINITY OF LAKE CHARLES, LOUISIANA: AN INVESTIGATION OF SALINE SOURCES A Thesis Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Master of Science in The Department of Geology by Alexandria M. Suding B.S., University of Notre Dame, 2011 August 2013 I dedicate this thesis to the late Dr. J.K. Rigby, Jr. I will never forget your strange, but memorable geology anecdotes! ii ACKNOWLEDGMENTS I would like to thank John and Wendy Lovelace for providing me with USGS water quality data. Also, thank you to Riley Milner for helpful advice and assistance in obtaining LADOTD well logs. Thank you to Dr. Jeffrey Hanor for the use of his SP to salinity spreadsheet, as well as all of his well log guidance along the way. Thank you to previous graduate students whose work has provided a knowledge base and an example to me, especially Callie Anderson. The graduate committee for this project included Dr. Clinton Willson from the Department of Civil Engineering, Dr. Phil Bart from the Department of Geology and Geophysics, and my committee chair Dr. Carol Wicks from the Department of Geology and Geophysics. I am very appreciative each of your unique contributions and suggestions. Finally, I want to express many thanks to my family and friends for their support and encouragement throughout this entire process. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS………………………………………………………………………iii LIST OF FIGURES………………………………………………………………….……………v ABSTRACT……………………………………………………………….……………….....…vii INTRODUCTION………………………………………………………………………………...1 GEOLOGIC SETTING……………………………………………………………………….…11 METHODS………………………………………………………………………………...…….20 RESULTS…………………………………………………………………………………..……27 DISCUSSION……………………………………………………………………………………40 CONCLUSIONS……………………………………………………………………………..….45 REFERENCES………………………………………………………………………………..…46 APPENDIX: TABLES OF WELL DETAILS AND SALINITY VALUES……………………49 VITA………………………………………………………………………………………..……65 iv LIST OF FIGURES Figure 1.1. Map Showing the Locations of the Aquifers of Louisiana……………………...……2 Figure 1.2. Location of Lake Charles, within Calcasieu Parish, LA………………………..……3 Figure 1.3. Total Groundwater Withdrawals in Calcasieu Parish from 1960-2010…………...…3 Figure 1.4. Pumping Well Locations from 1940-1959…………………………………...………5 Figure 1.5. Pumping Well Locations from 1960-1979……………………………………...……6 Figure 1.6. Pumping Well Locations from 1980-1999………………………………………...…7 Figure 1.7. Map Showing Regional and Local Cones of Depression in the Chicot Aquifer……..8 Figure 1.8. Map Showing the Location of the Three High Chloride Bodies in the 500’ Sand of the Lake Charles Industrial District…………………………………….……..8 Figure 1.9. Groundwater Level Data from Six USGS Wells in the Lake Charles Area……….…9 Figure 2.1. Regional Cross-Sections Illustrating the Changes in the Thickness and Interconnectedness of the Sand Units of the Chicot Aquifer…………………….………13 Figure 2.2. Interpreted Locations of Salt Domes in Calcasieu Parish……………………..........15 Figure 2.3. Stratigraphic and Structural Cross-section through Lake Charles Industrial Area……………………………………………………………………….…..17 Figure 2.4. Plot of Subsurface Pressure in the Central Industrial Area of Lake Charles.……….19 Figure 3.1. Linear Relationship Between Chloride Concentration and Specific Conductance for USGS Monitoring Wells in the Study Area…..…….…………..……..22 Figure 3.2. Example of a Spontaneous Potential Well Log Annotated with Shale Baseline, Maximum Deflection, and SSP Response ……………………………..24 Figure 3.3. Linear Relationship Between Mud Resistivity and Mud Fluid Resistivity at 75˚F...…………………………………………………………………...…26 Figure 4.1. 200’ Sand Chloride Contour Map for 1940-50s………………………..……...……29 Figure 4.2. 200’ Sand Chloride Contour Map for 1960-70s…………………………..…...……30 Figure 4.3. 200’ Sand Chloride Contour Map for 1980-90s…………………………..……...…31 Figure 4.4. 500’ Sand Chloride Contour Map for 1940-50s……………………………..…...…32 v Figure 4.5. 500’ Sand Chloride Contour Map for 1960-70s……………………………..…...…33 Figure 4.6. 500’ Sand Chloride Contour Map for 1980-90s………………….............................34 Figure 4.7. 700’ Sand Chloride Contour Map for 1940-50s………………………………….…35 Figure 4.8. 700’ Sand Chloride Contour Map for 1960-70s……………………………….....…36 Figure 4.9. 700’ Sand Chloride Contour Map for 1980-90s………………………………..…...37 Figure 4.10. Series of TDS Contour Maps (1,000-5,000 feet)………………………………….38 Figure 4.11. Series of TDS Contour Maps (5,000-8,000 feet)………………………………….39 vi ABSTRACT One of the most pressing issues facing groundwater managers is saltwater intrusion. In coastal Louisiana this issue is especially prevalent. One location that is currently threated by saltwater intrusion is the industrial area of Lake Charles, Louisiana, where three high chloride areas have been detected within the underlying Chicot aquifer. Three sand units of the Chicot aquifer are present in Lake Charles: the 200-foot (200’) sand, the 500’ sand, and the 700’ sand. Groundwater with elevated chloride concentrations was first noticed by industries in the early 1970s. An initial investigation determined that the northern and southern bodies had formed by upwelling of saline groundwater from the 700’ sand. However, the origin of the salinity in the central body was not determined. The objective of this study was to determine the origin of the salinity for the central chloride body. Two sources of data were obtained from wells in the area: (1) spontaneous potential (SP) and resistivity logs from oil and gas and water wells (2) water quality data from United States Geological Survey (USGS) monitoring wells. The result of this study was the creation of a series of isoconcentration contour maps that help illustrate the movement of the saline groundwater in each aquifer layer over time. Results indicate that saline groundwater has been introduced into the aquifer from a variety of sources over time, including surficial contamination and upwelling of brine from the Lockport salt dome. vii INTRODUCTION One of the most pressing issues threatening groundwater quality is the intrusion of saline water into freshwater aquifers (Tomaszewski, 1996; Barlow & Reichard, 2010; Welch & Hanor, 2011). Protecting groundwater from saline intrusion is important because once saltwater enters an aquifer, it is often difficult to reclaim that aquifer (Nyman, 1984). It is especially important to protect groundwater supplies that are the sole-source of drinking water for an area. A sole- source aquifer means that the aquifer supplies at least half of the drinking water for the area (USEPA, 2013). In coastal Louisiana, groundwater is at risk of saline water intrusion due to high rates of groundwater pumping and due to the existence of subsurface salt domes that may act as a source of saline water. This study is focused on the Chicot aquifer that serves as a sole-source water supply for most of southwestern Louisiana (Figure 1.1). One of the largest cities supplied by the Chicot aquifer is Lake Charles in Calcasieu Parish, Louisiana (Figure 1.2). In the Lake Charles area, the principle freshwater bearing sands of the Chicot aquifer are referred to as the “200-foot,” “500- foot,” and “700-foot” sands. All of these aquifers are utilized in Lake Charles, with the 500’ being the most heavily pumped (Lovelace, 1998). In recent history, Lake Charles has experienced saline water intrusion due to excessive groundwater pumping (Nyman, 1984). Groundwater pumping in Calcasieu Parish has decreased from past rates (Figure 1.3). Still, in 2010, 86.65 million gallons per day (Mgal/day) were withdrawn from the Chicot aquifer system, making Calcasieu Parish one of the top groundwater consumers in the state. The majority of this water was used for industry (40.88 Mgal/day) and public supply (25.73 Mgal/day) (Sargent, 2010). Lake Charles is a major center for both industry and population in Calcasieu Parish; thus, groundwater is pumped extensively. Figures 1.4-1.6 display the 1 Figure 1.1. Map showing the locations of the aquifers of Louisiana. The Chicot aquifer covers the majority of southwestern Louisiana. The yellow star denotes the approximate location of the study area. Modified from: LDNR GIS Center (1999). 2 Figure 1.2. Location of Lake Charles, within Calcasieu Parish, LA. Source: Figure was created using LDNR SONRIS (2012). Figure 1.3. Total groundwater withdrawals in Calcasieu Parish from 1960-2010. Dashed line indicates the opening of the Sabine River Diversion Canal. Source: Water Use Reports, 1960-2010,

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