2007 Thesis Abstracts

     Construction grading projects utilize a variety of soils and equipment in order to achieve the required compaction for structural fills.  Diatomaceous soils have been reputed as being difficult to compact.  No known quantitative studies exist comparing the relative field compactions between diatomaceous soils and other soil types.  This paper compares the relative field densities achieved between three different soils with varying amounts of compactive energy.  The three types of soils used were diatomaceous, gravelly silty sand, and silty sand.  The soils were field tested in concrete molds representing a lift thickness of three inches and six inches, and rolled over with the rubber tire of a car, with a varying number of passes.  The highest relative compactions were achieved with the thinnest lifts.  In general, the coarsest grained gravelly silty sand achieved the highest relative compaction and the finest grained silty sand achieved the lowest relative compaction, which was as expected since coarse grained soils tend to compact more readily than finer grained soils.  The diatomaceous soil was not difficult to compact, and behaved like a typical fine to medium grained sandy soil, with relative compaction densities between the coarsest grained gravelly silty sand and finest grained silty sand.

Gary Michael Duby, 2007, Analysis of Selenium in the Surface and Ground Waters of Peters Canyon Wash and San Diego Creek in the San Diego Creek Watershed, Orange County, California; Research Project Committee Members: Dr. Barry Hibbs (Committee Chair), Dr. Nathan Onderdonk, Dr. Kim Bishop

     The average concentration of selenium in the ocean is ~0.05 mg/L (Butterman and Brown, 2004). Though this does not pose a risk to aquatic organisms, there are localized areas adjacent to continents where rivers systems transport sediments and solutes from terrestrial sources and selenium concentrations are much greater. The San Diego Creek Watershed in Orange County, California conveys water from inland sources to the ocean through the Upper Newport Bay. Selenium concentrations within the watershed are as high as 600 μg/L (Hibbs, 2000) posing a substantial health risk to organisms living in the watershed and adjacent bay (the EPA standard for selenium in surface water is 5 μg/L).

     In concern of this potential hazard, the State Water Resources Control Board of California (SWRCB) has contracted with California State University, Los Angeles (CSULA) to investigate the sources of selenium loading into the San Diego Creek Watershed. The purpose of this Master’s Project was designed to monitor the surface waters in Peters Canyon Wash and San Diego Creek twice a month every other week for one year. During this period, surface water in these channels was monitored for 24 hours, once in the summer of 2005 and once in the winter of 2006. Hyporheic water samples, springs and piezometers were also sampled during the study period. The objective of this project is to evaluate if selenium is currently being transported from the San Joaquin Hills and/or the Santa Anna Mountains into the watershed via Peters Canyon Wash (PCW) and/or San Diego Creek (SDC) in quantities considered hazardous by the EPA (SWRCB, 2004). Water samples were collected in both channels at upstream locations near mountain headwaters and at locations approximately one kilometer downstream. Surface water parameters were also measured during sample collection (i.e. pH, temperature, turbidity, electrical conductivity and dissolved oxygen content). Water samples were also analyzed for various anions (i.e. Cl-, F-, PO43-, NO3-, AsO42-, and SO42-) and for total and dissolved selenium.

     The results of this study indicate that headwater sources in the Santa Ana Mountains do not contribute significant quantities of selenium into the watershed during the dry season because the upland streams are ephemeral and dry. The results also indicated that the San Joaquin Hills are not a point source for selenium into the watershed for the same reason. The results of the study have implicated that groundwater is responsible for much of the increased selenium fluxes measured downstream in both PCW and SDC (downstream values averaged 4.62 μg/L in PCW and 3.87 μg/L in SDC). It is important to note that the geochemical analysis presented in this report represents only dry weather conditions. It is intuitive to expect that under wet weather conditions loading of selenium into the watershed from providences in the Santa Ana Mountains and/or the San Joaquin Hills might rise dramatically due to the increased rate of erosion of the lithologic units present in the upland areas.

Morton Price, 2007, Recharge And Water Quality Of Baldwin Lake At The Los Angeles County Arboretum & Botanic Garden, Arcadia, California   (Research Project Committee Members: Dr. Barry Hibbs (Committee Chair), Dr. Nathan Onderdonk, Dr. Kim Bishop)

          Baldwin Lake is a 3.5 acre sag pond on the grounds of the Los Angeles arboretum located along the south flank of the San Gabriel Mountains in the northern San Gabriel valley. Baldwin Lake varies in depth from a few feet to 6 ft and is a geomorphic expression of the Raymond fault which trends through the arboretum. Artesian conditions exist in the vicinity of Baldwin Lake along with shallow, buried marsh deposits and a spring which has been reported to feed Baldwin Lake. With the development of multiple production wells north of the Raymond fault, regional groundwater elevations have decreased since the 1930's. During seasons of drought, Baldwin lake has completely dried up. The solution to this dilemma was to fill the lake up with municipal water and integrate the lake into the county storm drain system. To evaluate the current recharge conditions and propose a new source of recharge for Baldwin lake, water quality samples were collected from Baldwin lake, associated surface water locations and three groundwater wells installed for this study. Analysis of water samples indicates that artesian groundwater observed in the monitoring wells is not recharging Baldwin lake. Further, results of water quality analysis and drilling data suggest that recharge is from irrigation water recharging the shallow subsurface to Baldwin lake and to a lesser extent, urban runoff from nearby homes around the arboretum. As a result of this study, a new source of recharge and a management plan is proposed for Baldwin lake.

Efe Karahan Sahin, 2007, Comparison of Optimum Moisture Content Values of Diatomaceous Soil Between Laboratory and Field Conditions;  Thesis Committee: Dr. Kim Bishop (Committee Chair),  Dr. Nathan Onderdonk, Dr. Pedro Ramirez

     The distinctive Monterey Formation is widely exposed in Southern California and is characterized by consisting of marine deposits rich in fossil diatoms. These diatomite deposits formed from the accumulation of diatom tests that settled to the ocean floor during mid-Miocene. Within the greater Los Angeles area, major exposures of the Monterey Formation (and its equivalent, the Modelo Formation) occur in the Palos Verdes Hills, Santa Monica Mountains, Simi Hills, and Santa Susana Mountains.

      Because of their widespread exposure, Monterey and equivalent diatomaceous strata are often involved in grading for construction projects as compacted fill. Two of the main purposes of compacting the fill soil during grading is to increase the bearing capacity of the soil to support proposed structures and to prevent settlement. The water content of fill soil at the time of compaction is a key factor affecting the degree of compaction that can be efficiently achieved. The most effective water content for compaction of a given soil is known as the “optimum moisture content”. The optimum moisture content for any given soil is determined from the Modified Proctor compaction test performed in the laboratory. According to Unified Building Code, fills must be compacted to minimum 90% of the laboratory determined maximum density during grading.

     Compared to other soil types, diatomaceous soil has significantly higher optimum moisture content. Furthermore, based on anecdotal observations the optimum moisture content of diatomaceous soil during field compaction appears to be higher than the optimum moisture determined from the Modified Proctor compaction test in the laboratory. The purpose of this study is to compare compaction characteristics of diatomaceous soil between laboratory conditions and field conditions. In order to do that, diatomaceous soil samples were collected from three different sites in Los Angeles and Santa Barbara counties. The Modified Proctor Maximum density tests were performed in the laboratory to determine maximum dry density and the optimum moisture content for each soil sample.  In the field, diatomaceous soil samples were compacted by rolling with the tire of a car and then tested for density using the sand cone method. According to laboratory and field test results diatomaceous soil samples show low maximum dry density values and high optimum moistures. Laboratory determined maximum dry densities vary between 35.5 to 48 lbs per cubic foot and field determined maximum dry densities vary between 30 to 38 lbs per cubic foot. Optimum moisture contents determined in the laboratory vary between 81% and 103% whereas field determined moistures vary between 98.5% and 117%.

Mylene M Guron, 2007, Simulations of Channel Modifications Along the Los Angeles River;  Thesis Committee: Dr. Pedro C. Ramirez (Co-Chair); Dr. Crist Khachikian; Dr. Terri Hogue; Dr. Laura Rademacher (Co-Chair)

     Government agencies, city municipalities, local residents and environmental organizations are in collaboration to improve the conditions of the Los Angeles River (LAR). Many are proponents of restoring the LAR to a more natural floodplain. Taylor Yard represents the greatest opportunity to create a meaningful watershed-based project that exemplifies the multiple benefits approach to river revitalization along the LAR. Taylor Yard is the largest undeveloped parcel in close proximity to downtown Los Angeles and presents a point of transportation interconnection and link to the surrounding communities. The purpose of this project was to create a one-dimensional hydraulic model along this stretch of the LAR channel adjacent to Taylor Yard in Los Angeles County, California. Simulations of potential channel modifications were performed using the HEC-RAS software. This numerical model computes one-dimensional steady water surface profiles for natural and prismatic channels. In addition, sediment transport analysis based on the Laursen-Copeland and Yang methods provides planning-level estimates of the potential rate of sediment deposition and/or erosion in the post-modification LAR. Simulations of more natural materials and engineering methods for channel construction following concrete channel removal were compared to existing conditions. The three alternatives tested were: constructing a rectangular concrete channel utilizing the levees for recreation; vegetating the bank slope with native plants and utilizing the levees for recreation; and stepped terraces utilizing gabions and vegetation with integrated trails and utilizing the levees for recreation. Hydraulic results of each alternative simulation indicated that the channel capacity would not contain floods larger than the 100-year peak flood event. Additionally, nearby bridges caused hydraulic jumps, drops and backwater effects. As a result, trends of erosion and deposition identified suggest that these effects were attributable to these hydraulic results.

     Hydraulic modeling using HEC-RAS provided valuable insight into the potential effects of channel modification alternatives. The results from this study evaluated the potential impact of changes made along the LAR channel in the vicinity of Taylor Yard. These results from this study were designed to assist future work in floodplain restoration along the LAR.

Elcin Ugural, 2007, Consolidation Characteristics of Diatomaceous Soils;  Thesis Committee: Dr. Kim Bishop (Committee Chair),  Dr. Nathan Onderdonk, Dr. Pedro Ramirez

     Diatoms are single-celled plants that live in both freshwater and seawater. When the organisms die, their microscopic tests settle to the ocean or lake floor to accumulate as sediment. In Southern California, diatomaceous deposits are common in the Monterey Formation, which crops out extensively in the Palos Verdes Hills and the Transverse Ranges. Because of their common occurrence, diatomaceous soils are often utilized as compacted fill during grading for land development. The typical required standard is to compact fill soil to 90% of the maximum density determined in the laboratory using the Modified Proctor compaction test. Diatomaceous soil has unusual compaction characteristics as compared to many typical soils that consist of clay, silt, and/or sand. An anecdotal observation is that compaction in the field by rolling to achieve a density of 90% of the laboratory maximum density is much more difficult than for more typical granular soils. Because of the unusual compaction characteristics, the main concern of this study is whether the consolidation characteristics of diatomaceous soils also vary from that of other soils. Therefore, this study investigated whether the consolidation characteristics of diatomaceous soils vary with density and vary from non-diatomaceous soils. Laboratory tests were performed on hand collected diatomaceous rocks from the vicinities of Lompoc, Goleta beach, Palos Verdes Hills, and non-diatomaceous soil samples collected from Tujunga Wash (sand), Sunland Hills (silt-sand), and La Tuna Canyon (silt). Before any tests were performed, all diatomaceous rocks were crushed in order to obtain diatomaceous “soil” (that is, in the engineering sense of soil). Then, each of six soil samples were tested for their Modified Proctor Maximum density and consolidated at different relative densities ranging from 84% to 94% in 2% increments of the Modified Proctor maximum density. In this study, acceptable consolidation percentage for 90% density is considered to occur if 3% or less consolidation takes place during the hydrocompaction phase. Based on the consolidation test results and comparing the diatomaceous soils to non-diatomaceous soils, the main conclusion of this study is that the percent consolidation and hydrocompaction behavior shows little difference between the two types of soils at the various relative densities tested.

Angela Ortega, 2007, Interpretation of Geochemical Groundwater Data Collected from Mud Volcanoes, Imperial Valley, California; Research Project Committee Members: Dr. Barry Hibbs (Committee Chair), Joe Hwong, Dane Robinson

     The Mud Volcanoes area is located within the Salton Trough, which is a topographic and structural trough that extends from southeastern California into Mexico. It is an example of a terminal sink basin. The Salton Trough contains the Coachella Valley to the north and the Imperial Valley to the south.  Not much is known of the Mud Volcanoes, very few people know of their existence.  Groundwater from the Mud Volcano shows very unique geochemistry that is distinct from the surrounding waters in the area.  The Mud Volcanoes are surrounded by a thriving community of agricultural, canal systems, agricultural drainages, geothermal fields and the Salton Sea.

     During a hydrogeology fieldtrip held during a weekend students were taken to the Coachella and Imperial County.  Water samples were taken from eight (8) different locations. Samples were analyzed for Fluoride, Chloride, Bromide, Nitrate, Phosphate, Sulfate, and NO3.  After reviewing the laboratory results, Mud Volcano water samples showed considerably higher levels of Chlorine, Bromide, Sulfate and Nitrate.  There is no physical evidence of any local or regional activity that may have caused direct impact to the Mud Volcanoes, with the exception of agricultural recharge. There is a potential that agricultural activities may have impacted the groundwater near the Mud Volcanoes but why are they significantly higher than the Salton Sea. Other potential sources may be the livestock farms near Brawley (15 miles south of Niland) and/or the several experimental geothermal developments in the Imperial Valley extending from the south shore of the Salton Sea into Mexico. 

     As part of this study, samples were collected from several locations to asses their geochemical and isotopic signatures and for comparison to the Mud Volcano. Analysis of stable isotopes identifies the Mud Volcano plotting away from the Global Meteoric Water Line.  The analysis showed two distinct clusters; one cluster consists of δ18O -11.0 to -10.0 ‰ and δ 2H ranging from -93 to -88 ‰. Results of the Mud Volcano displayed δ18O ranging from -2.5 to 9.5 ‰ and δ 2H ranging from 0 to -54. Hydro-chemical data suggest enrichment in the δ 2H and δ18O due to evaporation of the lighter end members (δ 1H and δ16O). As the water evaporates from the open stagnant surface of the Mud Volcano, its signature possibly moves away from the meteoric water line along a line having a slope of between two and about five (depending on the effect of humidity). Five postulates are presented to develop a hypothesis in explaining the possible sources of enriched chemical constituents and isotopic signature observed in water collected from the Mud Volcanoes. Additional sampling is recommended to assess the evolution of light stable isotopes over the course of one year.