2006 Thesis Abstracts

Richard D. Viergutz, 2006, Discharge of Sewage-Polluted Groundwater into Malibu Creek and Lagoon Resulting from Groundwater Surface Water Interactions; Committee Members: Dr. Barry Hibbs (Chair), Dr. Kim Bishop, Mr. Ernie Weber 

      The study area is twenty-seven miles west of downtown Los Angeles at the southern limit ofthe 109 square mile Malibu Creek watershed where it discharges surface water to the Pacific Ocean. The watershed drains portions of the Santa Monica Mountains and Simi Hills and includes Malibu Creek and Lagoon. Malibu Creek has been heavily studied and is unique in that its headwaters are actually north of the crest of the Santa Monica Mountains, in the SimiHills. Despite rapid uplift of the Santa Monica Mountains, creeks flowing in Malibu Canyon maintained their southerly course, cutting deeply incised canyons through the mountains. Other creeks in the watershed don’t cross the Santa Monica Mountain’s asymmetrical crest, but instead are characterized by their position on the north or southern flank of the mountains as long southerly flowing streams, or short northerly flowing streams.

      Malibu Lagoon covers approximately twenty-nine acres and is actually a reconstructed lagoon, rebuilt after others filled it to provide land. Nevertheless, the lagoon provides wetland habitat. Since lagoons are scarce along this stretch of coastal California the lagoon is often used as an educational tool. Unfortunately the lagoon suffers from eutrophication and high bacteria counts. During the summer when the discharge from Malibu Creek is low, constructive barrier forming wave action and long shore deposition of sand close off the lagoon’s outlet to the Pacific Ocean and water levels in the lagoon rise. During high creek discharge, the barrier is breached, rapidly eroded, and the impounded surface water is discharged to the Pacific Ocean. The County of Los Angles closes the nearby beach (Surfrider Beach) when this occurs since the bacteria counts in the discharged water make water contact recreation unsafe.

      In the 1960’s groundwater in the Malibu area was used for drinking water and agriculture. Over time the quality of groundwater declined due to seawater intrusion and septic system discharges. Importation of potable water followed suit and at the time of this study, 1999 and 2000, approximately 8,500 acre-feet per year of potable water were delivered to the City of Malibu. The streams are naturally ephemeral, but the importation of water combined with discharges of wastewater via septic systems has increased baseflow. 

      Groundwater adjacent to Malibu Creek and Lagoon and surface water was sampled from August 1999 through December 1999 prior to, during, and after Malibu Lagoon breached.  Groundwater near a septic system leachfield contained ammonia at up to 34.7 mg/L and high concentrations of bacteria. Storm drain discharges contained ammonia at up to 39.2 mg/L and high concentrations of bacteria. Stream aquifer interactions controlled by lagoon discharge and tidal fluctuations result in the discharge of polluted groundwater to surface water via storm drains and natural seepage pathways.

Russell Kyle, 2006, Feasibility of Artificial Recharge In the Vicinity of
      Baldwin Lake Big Bear Valley, California;  Thesis Committee:
      Dr. Barry Hibbs, Dr. Richard Hurst, Dr. Kim Bishop

          Testing was conducted to determine the geohydrologic and regulatory feasibility of a large scale surface artificial recharge program within the vicinity of Baldwin Lake, Big Bear Valley, California. The purpose of the program would be to prevent secondarily treated recycled water generated from within Big Bear Valley from being exported to Lucerne Valley. Instead, the water would be used to artificially recharge ground water by applying it to surface spreading basins. Geohydrologic explorations of the candidate site included uncased borehole drilling, monitoring well installation, controlled pumping tests, and ground water sampling. Characterization of sediments beneath the site revealed no laterally extensive layers of fine-grained material which would inhibit vertical migration of percolating water. A pilot scale artificial recharge test was conducted using soil moisture sensors and a sulfur hexafluoride tracer to monitor wetting fronts and track temporal and spatial migration of infiltrating water. Data from the pilot scale testing were used to estimate recharge rates, horizontal hydraulic conductivity and seepage velocity, critical to demonstrating compliance with regulatory requirements. Percolating water migrated approximately 100 ft and reached the ground iv water table approximately 3 days after the recharge test began, resulting in the development of a ground water mound beneath the test site. Estimates of vertical recharge rate ranged from 3.1 to 3.7 ft/day based on data collected from the soil moisture sensors and from known volumes of water applied to the test basin. Using data collected from the pilot-scale recharge test and from geohydrologic knowledge of the surrounding area, seepage velocities were calculated to range from 5.3 to 11 ft/day. Ground water quality was not adversely affected by the recharged water although the source of the recharge water was from nearby ground water production wells. Exploration and testing revealed that the recharge site is a valid candidate for a full-scale artificial recharge program using surface spreading basins.

      The Rio Grande Valley between El Paso and Fort Quitman, Texas is one of the most productive agricultural areas in Texas.  Yet, the Valley is plagued by a history of salinity problems.  Both surface water and shallow groundwater are used to irrigate extensive crops in the Valley.  High salinity of irrigation water impacts productivity of these crops. 

     To determine source(s) of surface water and groundwater salinization of a 100 square mile segment of the Rio Grande floodplain (the “San Elizario Island” area), water samples were collected from irrigation and domestic wells, hand installed piezometers, springs, and surface waters.  Samples were analyzed for standard inorganic constituents, halides, stable isotopes, tritium, carbon-14 and chlorine-36.   Hydrochemical and isotopic plotting procedures and mixing diagrams were then used to interpret causes of salinity.     

     Based on their chemical composition the waters were recognized as sodium-chloride type overall. However, the Rio Grande aquifer data yielded significantly different chloride/bromide (Cl/Br) ratios. The Cl/Br results suggest that there are two major types of groundwater: (1) highly saline waters containing 900 to 15, 0000 mg/L Cl, and Cl/Br weight ratios of 1000 to 6000, and (2) dilute waters with low Cl/Br weight ratios (500 to 900) and 200 to 900 mg/L Cl.  Stable isotope ratios for all waters in this study plot along the Rio Grande Evaporation Line, indicating that there is no difference in the stable isotope signature between saline and dilute waters in the Rio Grande aquifer.  Stable isotopes indicate that partial evaporation of irrigation waters in soils does not account for enrichment of salinity in the Rio Grande aquifer. 

     When examined together, the isotope and inorganic hydrochemistry of shallow groundwater suggests two principal sources of salinity: (1) complete evaporation of irrigation waters during dry years which accumulates salts in soils, followed by leaching of salts from soils into shallow groundwater during wet (heavy irrigation) years; and (2) water/rock interaction caused by dissolution of halite deposits that formed in an ancient evaporite unit before the Rio Grande floodplain deposits were formed.  The dissolution of halite is the demonstrable source of high Cl/Br ratios and high salinity in shallow groundwater.

     Chlorine-36 isotopes suggest that the ancient evaporite unit beneath the Rio Grande aquifer is the more important source of salinity of shallow groundwater in San Elizario Island.  Saline groundwaters discharge into agricultural drains that are fed back into the Rio Grande irrigation system downstream of San Elizario Island.  Thus, results of this study suggest that amendment of agricultural practices for controlling salinity in the Rio Grande Valley can only be partially effective, due to the natural and more important source of salinity from dissolution of halite in the buried evaporite unit.

Lisa Ann Alpert, 2006, Emplacement of Three Plutons by Nested Diapirism and Stoping in Cactus Flat, San Bernardino County, Southern California;  Thesis Committee: Dr. Robert Stull, Dr. Kim Bishop, Dr. Pedro Ramirez

     Three plutons comprise Cactus Flat, north of Baldwin Lake in the San Bernardino Mountains – diorite, biotite granite, and muscovite granite. These plutons intrude the Precambrian to Paleozoic Wood Canyon Formation and the Paleozoic Carrara Formation. Ion microprobe U-Pb results indicate emplacement of the three plutons over a period of ~6 Ma, beginning with the diorite and biotite granite emplaced at 83 Ma, and the muscovite granite at 77.5 Ma. The three intrusions form an ellipsoidal map pattern with the diorite occurring as a sublinear outcrop typically separating the biotite granite from the country rock. The muscovite granite is exposed in irregular masses within the biotite granite. Field evidence indicates mesozonal emplacement of the diorite through diapiric ascent with shouldering aside of the Paleozoic country rock and some stoping of the roof rock. Near contemporaneous emplacement of the biotite granite as a nested diapir followed emplacement of the still-cooling diorite, with shouldering aside and stoping of the country rock. A later pulse of magma emplaced the muscovite granite as globular masses within the biotite granite. Contacts with the country rock and internal contacts between plutons are sharp and intrusive. Petrographic evidence reveals subsolvus crystallization and minimal solid-state deformation of all plutons.  Chondrite-normalized REE plots show enrichment in LREE and negative Eu anomalies increasing in magnitude with increasing SiO2 from the diorite to the muscovite granite. Average Eu/Eu* values are 0.86 for the diorite, 0.57 for the biotite granite, and 0.09 for the muscovite granite. In addition, SiO2 concentrations, Rb:Sr, K:Rb, A/CNK, and Zr:SiO2 suggests that the diorite, biotite granite, and muscovite granite are related by fractional crystallization processes.

Humberto E. Nation, 2006, A Study of the Wildfires Induced Alteration of the Physico-Chemical Properties of Soils;  Thesis Committee: Dr. Richard Hurst, Dr. Laura Rademacher, Dr. Crist Khachikian

     The macro effects wildfires have on ecosystems and watersheds range from increased erosion and weathering rates to variations in the distribution of water among various flowpaths.  The end results often have negative effects on wildlife ecosystems and people living near the urban wildlife interface.  Many of these effects should be traceable to alterations in the physico-chemical properties in the affected underlying soil, such as increase hydrophobicity, reduced permeability, changes in the substrate surface area, and biologically derived activities.  However, due to the scarcity of published material in this topic, little is known of the wildfire induced changes to these properties, as well as their role in post fire-event behavior, and their contribution to an ecosystem’s recovery.  The present study will contribute to an initial baseline assessment of the physico-chemical properties of soils before and after fire events, and will recognize these changes on temporal and spatial scales.  Additionally, this study will shed light in understanding the function and evolution of the soil biota after wildfire events.  Preliminary results indicate an adverse relationship between soil moisture and permeability as expected.  However, there appears to be a weak correlation in fire affected areas between the soil’s hydrophobicity, as measured by the water drop penetration time (WDPT) test, and permeability.  The possible ramification this study will have in areas of soil recovery forestry, ecology and disaster planning could be significant and thus merit substantial consideration.

Anna Marie Foutz, 2006, Regional and Contact Metamorphism in the Cactus Flat   Area, San Bernardino Mountains, California;  Thesis Committee: Dr. Robert Stull, Dr. Kim Bishop, Dr. Pedro Ramirez

      Contact metamorphic effects due to emplacement of Mesozoic diorite and granite intrusions are overprinted on regionally metamorphosed rocks of Cactus Flat, north of Big Bear and Baldwin lakes in the San Bernardino Mountains of southern California. Regional prograde metamorphism of the Wood Canyon, Zabriskie, and Carrara Formations at the upper greenschist to lower amphibolite facies was synchronous with faulting and folding.  Textures supporting this interpretation include foliated and bent grains with serrated articulations.  Neocrystallization occurred, changing these rocks from sandstones, shales, and limestones to quartzites, phyllites, and marbles. Critical mineral assemblages indicate a maximum temperature of approximately 560ºC.

Intrusion of late Mesozoic diorite caused upper pyroxene hornfels to lower sanidinite facies contact metamorphism.  Effects of diorite emplacement by forceful intrusion include slaty cleavage, folds and disruption of sedimentary structures, and an increase in grain size.  Critical minerals in schist beds within the Carrara Formation are andalusite, sillimanite (fibrolite), and cordierite, and critical minerals in the marble beds are diopside, forsterite, wollastonite, and garnet.  Fibrolite in the Wood Canyon Formation is found only at the contact with diorite.  These minerals indicate a maximum temperature between 735-775ºC in the contact aureole.  As diorite began cooling, hydrothermal fluids left the magma and caused the hydrous calc-silicates epidote, actinolite, and hornblende to replace the anhydrous cal-silicates diopside, garnet, and wollastonite.  Continued cooling added additional hydrothermal fluids to the Carrara Formation and spinel, phlogopite, meionite, melilite, and gehlenite crystallized.  Fluorine metasomatism produced humite, clinohumite, and chondrodite.

The final stage of metamorphism in Cactus Flat occurred as granitic intrusions caused static, retrograde metamorphism in the albite-epidote-hornfels facies at temperatures of about 350-450˚C.  Recrystallization caused increase in grain size and forceful intrusion locally folded beds. Grains straightened, articulation smoothed, and minerals grew across foliation.  Low temperature, retrograde reactions occurred in marbles of the Carrara Formation as calcite and chlorite replaced higher temperature minerals.  Calcite replaced cordierite in schist beds of the Carrara Formation. Potassium metasomatism occurred, which caused growth of muscovite porphyroblasts and replacement of andalusite by muscovite. 

Pressure conditions during contact metamorphism can be suggested based on the mineralogy of the intrusions.  The diorite, biotite granite, and muscovite granite are all subsolvus intrusions (Alpert, 2006 unpub. MS thesis), which suggests a minimum emplacement pressure of about 5 kilobars at depths of about 20km (Morse, 1970). 

Contact metamorphism created by the biotite granite is overprinted on the contact metamorphic aureole of the diorite.  This relationship supports Alpert’s (2006) conclusion that diorite intrusion preceded granite intrusion in Cactus Flat.  Furthermore, the time interval between intrusions must have been on the order of 10⁶ years in order to allow sufficient cooling for this overprinting to be recorded. 

Raymond C. Friedrichsen, 2006,  The Possible Impact of Selected Hydrocarbons on The Local and Regional Aquifers from a Leaking Underground Storage Tank;  Thesis Committee: Dr. Barry Hibbs, Dr. Richard W. Hurst, Dr. Richard A. Vogel

     A vapor extraction and air sparge pilot tests were both conducted at the Bell site to determine if it is conductive to vapor extraction and air sparging conditions. If the tests prove that subsurface soil conditions are feasible for vapor extraction (VE) and air sparging (AS) activities, then a VE/AS remediation system would be designed, tested, and implemented at the site.  But if the tests prove that the subsurface lithology is not conductive to VE or AS remedial activities for any number of reasons, e.g.: tightness of soils or short circuiting of the vapor stream, then addition remedial methods must be tested.

     This pilot study was conducted at the City of Bell Police Department rear parking lot located in Bell, California.  Two continuous soil borings were drilled outside the hydrocarbon plume for plume delineation purposes. The soil boring GP-1 was successful at delineating the plume toward the north, while soil boring

     GP-2 delineated the plume toward the south, enough to conduct a very accurate and successful vapor extraction/air sparging pilot test.

     Before the pilot tests could be conducted two events of groundwater monitoring and sampling had to be conducted at the site. These groundwater monitoring events were to determine the hydrocarbon concentration in the groundwater, as well as determine the groundwater gradient flow direction. The groundwater flow direction and hydrocarbon concentrations must be known because as the test is being conducted it is important not to excel the speed of the groundwater; therefore, spreading the hydrocarbon concentration.

Mathew A. Kelliher, 2006, Sources and Evolution of Waters at Dos Palmas Preserve and Vicinity, Salton Sea, California;  Thesis Committee: Dr. Barry Hibbs,  Dr. Richard Laton, Mr. Ted Johnson

     The All American Canal and its Coachella Branch divert approximately 3.4 million acre-feet of water per year from the Colorado Rivers for use in the Imperial and Coachella Valleys.  Currently, about 100,000 acre feet per year of water is currently lost by seepage into the ground along unlined portions of All American Canal and Coachella Canal.  On the northeast side of the Salton Trough, leakage from the unlined Coachella Canal recharges local aquifers, and has created an extensive series of wetlands hydraulically downgradient of the Coachella Canal at the contact between coarse-grained alluvial fan material and Quaternary lacustrine sediments.  At the contact between alluvial fan material and lacustrine sediments, spring discharge has created an extensive system of wetlands that have grown dramatically since the Coachella Canal was constructed in 1949.  The wetlands were natural features prior to Canal construction, but their areal extent was limited due to minimal natural recharge.  Today the extensive wetlands support a habitat that includes a wide variety of flora and fauna.

     Lining of the entire Canal is in progress and is scheduled for completion in December 2006.  Samples were collected from several spring and well locations downgradient from Coachella Canal to assess their geochemical and isotopic signatures for comparison to Canal and native groundwater sources.  Analysis of stable isotopes identifies three distinct groups of water; one group consists of nearly pure Canal water with d18O ranging from -11.3 to -11.7 and d2H ranging from -84 to -95.  A second group consists of nearly pure native groundwater with d18O ranging from -7.3 to -8.7 and d2H ranging from -59.5 to -71.  A third group consists of various mixtures of Canal and native groundwater with d18O ranging from -8.7 to -11.1 and d2H ranging from -80 to -91.  Hydrochemical data suggest that Canal Recharge water evolves as it moves beneath the study area.  A progressive evolution is seen with increasing distance from the canal where dominant anions in water change from HCO3, SO4, and Cl near the Canal to SO4 and Cl dominated waters roughly midway across the study area to Cl and SO4 dominated waters at the furthest distance away from the Canal.  Evidence of halite dissolution is also evident, with increasing Na/Cl following a nearly one-to-one trend from the Canal to the furthest sampling location away from the Canal. Native groundwater within the basin is typically highly evolved with Na the dominate cation and Cl the dominant anion.

      It is likely that once lining of the Canal has been completed, flow at the wetlands will decrease.  As flow decreases the isotopic and hydrochemical signature of the waters should evolve toward that of native groundwater; this evolution will be a direct result of decreased recharge from the Coachella Canal.  Wetland habitat will also decrease due to diminished recharge and a gradual salinization of groundwater.  It is unknown how complete this transformation will be or how long it will take to occur; therefore, continued monitoring of these locations should be done after lining of the Canal to determine the effect of reduced spring and well flow on the current wetland areas.

James E. Walker III, 2005, Nitrate and Selenium Transport and Speciation in Relation to Land use Change in the San Diego Creek Watershed, Irvine California (Thesis Committee: Barry Hibbs, Richard Hurst, Ernie Weber)

The Upper Newport Bay Watershed is located in Irvine, California, within South Central Orange County.  The watershed is a sensitive ecological environment, home to many sensitive species of plants and animals. Nitrogen and selenium have been identified as two constituents of concern within the watershed.  Excess nitrogen has been shown to result I the growth of algal blooms in Upper Newport Bay, while excess selenium is suspected of causing birth defects in waterfowl.

The objectives of the study were to identify and quantify the transport and speciation of nitrogen and selenium in the watershed, as well as identify possible sources for these constituents.  Methods of analysis include gaging streamflows to determine if local creeks are gaining or losing streams, sampling soils and groundwater for selenium and nitrogen species, and performing temporal comparisons of nitrogen and selenium to seasonal fluctuations in groundwater elevations.

Stream gauging showed that gaining stream conditions were present along a controlled section of the watershed.  Controls were established by setting sand bags and monitoring equipment along several creeks and tributaries to confine surface flows to measurable cross sections.  Gaining stream conditions are defined as instances when groundwater elevations are greater than surface water elevations, leading to discharge of groundwater into surface flows.  Discharge increased an average of 2.4 cubic feet per second over the controlled reach of channel that was measured on three separate occasions over the course of one year.  Concurrent water quality sampling showed that upwelling groundwater contained greater concentrations of selenium and nitrate than surface water.  Nitrate loading due to groundwater seepage increased an average of 123.8 pounds per day while selenium loading increased an average of 0.453 pounds per day.

Nitrate and selenium concentrations in groundwater also showed temporal variations throughout the watershed.  The dominant control over the variation appears to be precipitation rates for the region.  A seasonal precipitation increased and as groundwater levels rebounded during recharge events, concentrations of nitrogen and selenium in groundwater also increased. This suggests that nitrate and selenium is leached from the unsaturated zone into groundwater.

A more detailed study of one of the tributaries of the watershed, Lane Channel, was performed in order to more thoroughly examine the processes that had been previously identified throughout the watershed.  Examination of soils adjacent to Lane Channel indicated that the unsaturated zone is the primary source of nitrate and selenium leaching into Lane Channel.  The presence of phreatic caliche and selenium sulfate salts in the unsaturated zone in Lane Channel suggest that the region around the channel was an area of shallow groundwater evaporation during predevelopment times.  Phreatic caliche forms in the subsurface when shallow groundwater evaporates, resulting in the precipitation of calcium carbonate.  As the groundwater evaporated off of the top of the water table and moved upward, various dissolved solids became supersaturated, and precipitated out as various soil horizons above the water table.

Lane Channel is located along the southern border of the “Swamp of the Frogs Marsh”, a marshy area that was reclaimed by development of the region at the beginning of the 20th century.  Shallow groundwater  evaporating along the southern border of the Swamp of the Frogs resulted in the precipitation of the caliche and then sulfate salts.  Groundwater in the Lane Channel region shows a higher concentration of sulfate than in other regions of the watershed, suggesting that the source of nutrients and trace metals in groundwater is leaching of salts and other constituents in the vadose zone from infiltrating rainwater.

The original source of selenium in the vadose zone is from deposition of selenium rich sediments in the “Swamp of the Frogs”.  The region was typified by wet marshy land, excellent for plant and animal habitat, but unsuitable for human purposes and needs.  The swamp, having a large quantity of organic matter was most likely a reducing zone.  Upon exposure to the reducing conditions in the marsh, selenium in the incoming soil was immobilized and stored in the marsh, building up over the years.  The area of the former marsh, having been reclaimed by ranchers at the turn of the twentieth century, is no longer a reducing environment.  Oxidizing rainwater now infiltrates through the soils that built up in the marsh, remobilizing trace metals, such as selenium, and transports them to the water table.  The original source of nitrogen in the watershed is most likely from historic agriculture in the region.  Higher concentrations of nitrogen in groundwater generally occur in regions that were identified as agricultural from aerial photos of the region.  Excessive fertilization of soils likely led to a buildup of nitrogen in the subsurface in areas of heavy agriculture, a common use of land in the orange county area.

The issues faced by the Upper Newport Bay Watershed are result of land use changes since development of the Irvine area began.  Reclamation of the land for use as pastures and farms resulted in the installation of drainage channels throughout the region.  These channels lowered the groundwater table, exposing previously saturated soil to infiltrating rainwater.  The use of the land for agricultural purposes led to the concentration of nitrogen in the subsurface.  Drainage of the marshlands also created oxidizing conditions that are ideal for remobilization and leaching of naturally occurring selenium from the unsaturated zone.  These results of this land use changes were not anticipated at the time that they occurred.  But understanding their impact now, helps us better understand the results of land use changes that being made today.