Imperial County Research Articles

Use of airborne PM10 concentrations at air quality monitoring sites in Imperial County, California, as an indication of geographical influences on lung health during drought periods: a time-series analysis

Background2012–16 marked the worst drought in California, USA, in more than a century. Droughts are expected to recur in broader areas as a result of anthropogenic climate change. The Salton Sea, a landlocked depression without natural river inflow, is almost entirely dependent on agricultural irrigation of Imperial Valley's 475 000 acres of farmland, although its water level has been diminishing because of decreased precipitation and river flow. Exposure of the lakebed and ground heating in an already arid climate might cause an increase in airborne PM10 (particulate matter less than 10 μm in diameter), reactive nitrogen, and ground-level ozone, exacerbating asthma symptoms. During the most severe drought years, admissions of children to the emergency department for asthma-related symptoms in Imperial County were among the highest in California and double the number for the entire state. However, previous analyses have not taken into account environmental mediators with more specific geographical granularity than the county level. MethodsIn this analysis, we used 2006–16 data from the US Drought Monitor and the five air quality monitoring stations (AQMS) within Imperial County, CA, USA. To reconcile sampling differences between 7-day drought severity reports and 6-day PM10 measurements, a date windowing function was applied to match each PM10 measurement to the drought severity value at the most closely related point in absolute time. Upon visually examining the data, lower concentrations of PM10 appeared to drive the correlation between AQMS. Therefore, in two time series—all years and non-drought years only—all concentrations of PM10 that were lower than 75 ppm were removed, and the remaining concentrations were used to measure correlations between AQMS. FindingsPM10 concentrations across all years were poorly correlated between AQMS (r=0·41–0·80; p<0·05). When removing PM10 concentrations lower than 75 ppm and examining only the remaining values, the correlation coefficients for these values decreased (r=0·16–0·53; p<0·05). When removing drought years (2012 onwards), these values were slightly more correlated in comparisons between some AQMS than across all observed years (r=0·46–0·77; p<0·05). InterpretationThe inconsistency in PM10 concentrations between AQMS on high PM10 days and during drought years suggests that different AQMS do not experience the same changes in air quality, particularly on days most likely to cause asthma exacerbations. This finding indicates a geographical component of air-quality differences and the potential for children near rural farmland to be more susceptible to asthma and lung disease. Future research regarding respiratory health in drought areas will provide a perspective on under-represented local and regional environmental challenges. Drought is one of the most expensive natural events from a number of economic and public health stances, and findings in support of the health implications of agriculture and water use have broader potential implications for water policy, drought mitigation strategies, and health improvement. FundingNone.

Changing patterns in water toxicity associated with current use pesticides in three California agriculture regions.

Regulation of agriculture irrigation water discharges in California, USA, is assessed and controlled by its 9 Regional Water Quality Control Boards under the jurisdiction of the California State Water Resources Control Board. Each Regional Water Board has developed programs to control pesticides in runoff as part of the waste discharge requirements implemented through each region's Irrigated Lands Regulatory Program. The present study assessed how pesticide use patterns differ in the Imperial (Imperial County) and the Salinas and Santa Maria (Monterey County) valleys, which host 3 of California's prime agriculture areas. Surface-water toxicity associated with current use pesticides was monitored at several sites in these areas in 2014 and 2015, and results were linked to changes in pesticide use patterns in these areas. Pesticide use patterns appeared to coincide with differences in the way agriculture programs were implemented by the 2 respective Regional Water Quality Control Boards, and these programs differed in the 2 Water Board Regions. Different pesticide use patterns affected the occurrence of pesticides in agriculture runoff, and this influenced toxicity test results. Greater detection frequency and higher concentrations of the organophosphate pesticide chlorpyrifos were detected in agriculture runoff in Imperial County compared to Monterey County, likely due to more rigorous monitoring requirements for growers using this pesticide in Monterey County. Monterey County agriculture runoff contained toxic concentrations of pyrethroid and neonicotinoid pesticides, which impacted amphipods (Hyalella azteca) and midge larvae (Chironomus dilutus) in toxicity tests. Study results illustrate how monitoring strategies need to evolve as regulatory actions affect change in pesticide use and demonstrate the importance of using toxicity test indicator species appropriate for the suite of contaminants in runoff in order to accurately assess environmental risk. Integr Environ Assess Manag 2018;14:270-281. © 2017 SETAC.

A Mediation Analysis of Mothers' Dietary Intake: The Entre Familia: Reflejos de Salud Randomized Controlled Trial.

Examine intervention effects among mothers involved in a healthy eating randomized controlled trial. Furthermore, examine the mediating roles of individual and familial influences on observed outcomes. Between 2009 and 2011, 361 families were recruited; half were assigned to an 11-session community health worker-delivered family-based intervention targeting Spanish-speaking Latino families in Imperial County, California. The intervention was delivered over a 4-month period. Home visits and telephone calls were delivered approximately weekly, with tapering near the end of the intervention to promote independence from the promotora. In this article, mothers' self-reported dietary intake was the primary outcome. Evaluation measures were taken at baseline, 4 months, and 10 months. Daily servings of fruits were higher among intervention versus control mothers (mean = 1.86 vs. mean = 1.47; effect size [ES] = 0.22) at 10 months post-baseline. Mothers in the intervention versus control condition also reported consuming a lower percent energy from fat (mean = 30.0% vs. 31.0%; ES = 0.30) and a higher diet quality (mean = 2.93 vs. mean = 2.67; ES = 0.29). Mediators of improvements were behavioral strategies to increase fiber and lower fat intake, family support for vegetable purchasing, and decreased unhealthy eating behaviors and perceived family barriers to healthy eating. Family-based behavioral interventions are effective for changing the skills and family system needed to improve diet among Latina mothers. Health care providers and other practitioners are encouraged to target skill development and fostering a socially supportive environment.

Development and field validation of a community-engaged particulate matter air quality monitoring network in Imperial, California, USA

ABSTRACTThe Imperial County Community Air Monitoring Network was developed as part of a community-engaged research study to provide real-time particulate matter (PM) air quality information at a high spatial resolution in Imperial County, California. The network augmented the few existing regulatory monitors and increased monitoring near susceptible populations. Monitors were both calibrated and field validated, a key component of evaluating the quality of the data produced by the community monitoring network. This paper examines the performance of a customized version of the low-cost Dylos optical particle counter used in the community air monitors compared with both PM2.5 and PM10 (particulate matter with aerodynamic diameters <2.5 and <10 μm, respectively) federal equivalent method (FEM) beta-attenuation monitors (BAMs) and federal reference method (FRM) gravimetric filters at a collocation site in the study area. A conversion equation was developed that estimates particle mass concentrations from the native Dylos particle counts, taking into account relative humidity. The R2 for converted hourly averaged Dylos mass measurements versus a PM2.5 BAM was 0.79 and that versus a PM10 BAM was 0.78. The performance of the conversion equation was evaluated at six other sites with collocated PM2.5 environmental beta-attenuation monitors (EBAMs) located throughout Imperial County. The agreement of the Dylos with the EBAMs was moderate to high (R2 = 0.35–0.81).Implications: The performance of low-cost air quality sensors in community networks is currently not well documented. This paper provides a methodology for quantifying the performance of a next-generation Dylos PM sensor used in the Imperial County Community Air Monitoring Network. This air quality network provides data at a much finer spatial and temporal resolution than has previously been possible with government monitoring efforts. Once calibrated and validated, these high-resolution data may provide more information on susceptible populations, assist in the identification of air pollution hotspots, and increase community awareness of air pollution.

Characterization of Foliar Web Blight of Spinach, Caused by Pythium aphanidermatum, in the Desert Southwest of the United States.

A unique foliar disease of spinach, determined to be caused by Pythium aphanidermatum, was observed on spinach in Yuma County, AZ and Imperial County, CA desert spinach production areas in both 2015 and 2016. The foliar symptoms of the disease included water-soaked foliage, rapid collapse of young plants, and white, aerial, cottony mycelia. The disease was associated with hot (27 to 42°C) and wet conditions associated with overhead irrigation under high-density plantings (>8.0 million seeds/ha). Isolations were performed on symptomatic tissue, and DNA was recovered from pure culture of the isolates recovered and sequenced using the internal transcribed spacer (ITS) ribosomal DNA (rDNA) primers ITS1/ITS4 and gene cytochrome oxidase I (COXI) primers FM55 and FM59. BLAST searches in GenBank indicated that the isolates were P. aphanidermatum based on 99 to 100% homology of ITS rDNA. Moreover, the DNA sequences of the ITS and COXI were identical for the five representative isolates. The objective of this research was to determine whether P. aphanidermatum recovered from symptomatic spinach tissue was able to cause foliar web blight and damping-off of spinach and other crops. In addition to spinach, other hosts evaluated included cotton, soybean, pepper, tomato, cucumber, melon, squash, lettuce, corn, wheat, and rice in greenhouse trials. Inoculations were performed by either foliar inoculations or infesting the soil with plugs of potato dextrose agar colonized by the P. aphanidermatum. Web blight symptoms were severe on spinach and all other dicotyledonous hosts tested, except lettuce. No web blight symptoms were observed on corn or rice, and only minor symptoms were observed on 10-day-old seedlings of wheat. P. aphanidermatum caused severe preemergence damping-off of all dicotyledonous plant species tested but only caused limited seedling size reduction in corn and wheat. Mefenoxam treatment of spinach seed provided complete protection against preemergence damping-off of spinach at both low (0.15 g a.i./kg of seed) and high (0.70 g a.i./kg of seed) rates of application, and the high rate of the application resulted in complete protection against web blight of spinach for 10 to 20 days after planting.

Sulfate mineralogy of fumaroles in the Salton Sea Geothermal Field, Imperial County, California

The Salton Trough lies in the transition between the San Andreas Fault and oblique spreading centers and transform faults in the Gulf of California. The Salton Sea Geothermal Field is the northernmost expression of those spreading centers. In ~2007 two ammonia-emitting fumarole fields that had been submerged beneath the Salton Sea were exposed for the first time in nearly 50years. As the sea level continued to drop these fields have developed a number of boiling pools, mud pots, gryphons and a unique suite of ammonium sulfate minerals. These have been studied over time with long-wave infrared remote sensing coupled with ground truth surveys backed by laboratory analyses of the minerals. Many vents lie at the center of concentric rings of mineralization with systematic occurrence of different minerals from center to edge. Three semi-concentric zones (fumarole, transition and evaporite) have been defined with respect to ammonia-emitting vents and bubbling pools. The scale of these zones range from several meters, localized around individual vents, to that of the fumarole fields as a whole. The fumarole zone is closest to the vents and locally contains cavernous sulfur crystals and significant deposits of gypsum, mascagnite, boussingaultite and other ammonium sulfates. The transition zone comprises a dark brown surficial band of inconspicuous sodium nitrate underlain by anhydrite/bassanite that is thought to have formed by ammonia-oxidizing microbes interacting with the ammonium sulfates of the outer fumarole zone. The evaporite zone is the outermost and contains blödite, thenardite and glauberite, which are typical of the sulfates associated with the shoreline of the Salton Sea. Remote sensing has shown that the mineral zones have remained relatively stable from 2013 to 2017, with minor variations depending on rainfall, temperature and levels of agricultural runoff.

The Imperial County Community Air Monitoring Network: A Model for Community-based Environmental Monitoring for Public Health Action.

Summary:The Imperial County Community Air Monitoring Network (the Network) is a collaborative group of community, academic, nongovernmental, and government partners designed to fill the need for more detailed data on particulate matter in an area that often exceeds air quality standards. The Network employs a community-based environmental monitoring process in which the community and researchers have specific, well-defined roles as part of an equitable partnership that also includes shared decision-making to determine study direction, plan research protocols, and conduct project activities. The Network is currently producing real-time particulate matter data from 40 low-cost sensors throughout Imperial County, one of the largest community-based air networks in the United States. Establishment of a community-led air network involves engaging community members to be citizen-scientists in the monitoring, siting, and data collection process. Attention to technical issues regarding instrument calibration and validation and electronic transfer and storage of data is also essential. Finally, continued community health improvements will be predicated on facilitating community ownership and sustainability of the network after research funds have been expended. https://doi.org/10.1289/EHP1772

Cumulative Absolute Velocity as a Local Damage Indicator of Instrumented Structures

This paper addresses the critical issue of localized damage detection in structural health monitoring. It evaluates the application of cumulative absolute velocity (CAV) as a local damage indicator for analyzing the acceleration response of a shaking table test specimen as well as real instrumented buildings. A bridge column test specimen instrumented with 18 accelerometers is subjected to increasing six levels of shaking corresponding to different damage states. The CAV analysis of the horizontal response of the accelerometers identified the elevation where damage is located. The vertical CAV analysis not only identified the existence of damage but also located the damage with high precision. This method is subsequently applied to two instrumented buildings damaged during earthquakes. The results show that for the seven-story Van Nuys hotel, the CAV can correctly locate the damage that occurred during the 1994 Northridge earthquake. For the Imperial county services building, the CAV is also able to correctly identify the location of damage. Thus, the presented CAV method enables identifying the onset and location of damage to evaluate the structural integrity.

Material, Political, and Biopolitical Dimensions of “Waste” in California Water Law

AbstractCalifornia's state constitution prohibits the “wasteful” use of water; however, waste is subjective and context dependent. This paper considers political, biopolitical, and material dimensions of waste, focusing on the role of legal processes and institutions. The paper examines a case involving legal accusations of “waste and unreasonable use” of water by the Imperial Irrigation District in Imperial County, California. The determination that water was being “wasted” justified the transfer of water from agricultural to urban areas. However, defining these flows of water as a waste neglected water's complexity and relationality, and the enclosure of a “paracommons” threatens to bring about negative environmental and public health consequences. The paper shows that the project of discursively labeling certain material resource flows as waste and re‐allocating these resources to correct this moral and economic failure relies upon legal processes, and carries political and biopolitical implications.

Factors Affecting Implementation of the California Childhood Obesity Research Demonstration (CA-CORD) Project, 2013.

IntroductionEcological approaches to health behavior change require effective engagement from and coordination of activities among diverse community stakeholders. We identified facilitators of and barriers to implementation experienced by project leaders and key stakeholders involved in the Imperial County, California, Childhood Obesity Research Demonstration project, a multilevel, multisector intervention to prevent and control childhood obesity.MethodsA total of 74 semistructured interviews were conducted with project leaders (n = 6) and key stakeholders (n = 68) representing multiple levels of influence in the health care, early care and education, and school sectors. Interviews, informed by the Multilevel Implementation Framework, were conducted in 2013, approximately 12 months after year-one project implementation, and were transcribed, coded, and summarized.ResultsRespondents emphasized the importance of engaging parents and of ensuring support from senior leaders of participating organizations. In schools, obtaining teacher buy-in was described as particularly important, given lower perceived compatibility of the intervention with organizational priorities. From a program planning perspective, key facilitators of implementation in all 3 sectors included taking a participatory approach to the development of program materials, gradually introducing intervention activities, and minimizing staff burden. Barriers to implementation were staff turnover, limited local control over food provided by external vendors or school district policies, and limited availability of supportive resources within the broader community.ConclusionProject leaders and stakeholders in all sectors reported similar facilitators of and barriers to implementation, suggesting the possibility for synergy in intervention planning efforts.

Community engagement in development of a community air monitoring network in Imperial County, California

INTRODUCTION: Imperial County, California, is a low-income, primarily Latino community that faces disproportionate impacts from a range of environmental hazards. With consistently high rates of emergency room visits and hospitalizations for asthma among schoolchildren, the community identified air pollution as a priority concern. Community members collaborated with researchers to build a community air monitoring network to provide local data on air quality that can be used to protect community health. METHODS: A community-based organization responsive to local concerns participated in research planning from the outset, and a Community Steering Committee guided the project. Community members selected priority neighborhoods within the county for air monitoring, and over 40 local residents identified vulnerable population groups. Key informant interviews informed data display decisions. Data was visualized using an environmental health web platform developed by the community. RESULTS: Community participation increased the usefulness of the monitoring network to the community. Community members identified schools throughout the county as priorities for siting the first 20 monitors. Local schools and businesses facilitated monitor deployment, promoting local capacity for maintenance. Training on air monitoring established a common knowledge base. Selection of monitor sites and hosting of monitors by local residents promoted community ownership of the monitoring network. Community input determined priority data display needs. Conclusions: Substantial engagement of and leadership by community members at every stage of planning and implementation of an air monitoring network (1) enhances responsiveness of research to community priorities, (2) fosters community ownership of the project and builds local capacity, (3) ensures accessibility, usability and usefulness of data displayed, and (4) promotes potential for network sustainability beyond the research period.

Attitudes Towards Gambling, Gambling Problems, and Treatment Among Hispanics in Imperial County, CA.

Gambling problems are associated with a wide range of serious negative personal, social, health, and mental health consequences and are an important public health concern. Some data suggest that gambling problems may be more prevalent among Hispanics, but few studies have been conducted in this community. The aim of the current study was to gather community-based, gambling-related data in order to increase understanding of gambling problems and their treatment in the Hispanic community. We conducted a mixed-methods study of gambling behavior and attitudes towards gambling, those with gambling problems, and professional treatment for gambling problems in a publicly funded health center serving a primarily Hispanic clientele. Study participants included clinic staff and clinic patients. All participants completed a brief, self-report survey; however, staff participated in a focus group on gambling issues and patients were interviewed individually about gambling issues. Nearly 80% of patients had gambled in the past month, as compared to about 36% of clinic staff. Survey data showed that patients had many risk factors for gambling problems. Focus group and interview information indicated that most viewed gambling problems as a form of addiction, the elderly were seen as being at increased risk for gambling problems, and gambling outings represented one of the few recreational opportunities in the region. The majority of both staff and patients believed that there was a need for gambling-related treatment services in the county; however, a notable minority of patients said that they would first seek help from a trusted relative or family member. Possible avenues to increase awareness of, screening for, and treatment for gambling problems may include collaborations with publicly funded health care centers and the training of promotoras to serve as an interface between health services and the community.

Validation of the modified Parenting Strategies for Eating and Physical Activity Scale-Diet (PEAS-Diet) in Latino children

Research shows that Latino parenting practices influence children's dietary and weight outcomes. Most studies use parent-reported data, however data from children may provide additional insight into how parents influence their children's diet and weight outcomes. The Parenting Strategies for Eating and Activity Scale (PEAS) has been validated in Latino adults, but not in children. This study evaluated the factor structure and concurrent and predictive validity of a modified version of the PEAS (PEAS-Diet) among Latino children. Data were collected from 361 children ages 7–13 from Imperial County, California, enrolled in a randomized controlled trial to promote healthy eating. The PEAS-Diet included 25 candidate items targeting six parenting practices pertaining to children's eating behaviors: (a) monitoring; (b) disciplining; (c) control; (d) permissiveness; (e) reinforcing; and (f) limit-setting. Children were on average ten years old (±2), 50% boys, 93% self-identified as Latino, 81% were US-born, and 55% completed English versus Spanish-language interviews. Using varimax rotation on baseline data with the total sample, six items were removed due to factor loadings <.40 and/or cross-loading (>.32 on more than one component). Parallel analysis and interpretability suggested a 5-factor solution explaining 59.46% of the variance. The subscale “limit-setting” was removed from the scale. The final scale consisted of 19 items and 5 subscales. Internal consistency of the subscales ranged from α = .63-.82. Confirmatory factor analyses provided additional evidence for the 5-factor scale using data collected 4 and 6 months post-baseline among the control group (n = 164, n = 161, respectively). Concurrent validity with dietary intake was established for monitoring, control, permissiveness, and reinforcing subscales in the expected directions. Predictive validity was not established. Results indicated that with the reported changes, the interview-administered PEAS-Diet is valid among Latino children aged 7–13 years.

Engaging Imperial County Communities In Participatory Hazard And Asset Mapping And Development Of Public Health Actions

INTRODUCTION: Imperial County, California, near the U.S.-Mexico border, is a low-income, primarily Latino community exposed to poor air quality, pesticides, and water contamination. A community-academic-state health agency partnership facilitated a participatory mapping process using mobile phones to document local hazards and assets. Participants used collected data in planning actions to improve community health. METHODS: A Community Steering Committee, representing diverse local stakeholders with experience in environmental health advocacy, guided the project and prioritized impacted neighborhoods. Residents of these neighborhoods were recruited and trained. An innovative crowd-sourcing mapping tool designed by and for local residents was adapted to allow data capture with cell phones. Using collected data and resident expertise, participants engaged in a process to prioritize issues and organize public health actions. RESULTS: 45 community residents received training and mapped sites over an 8-day period, collecting locations, photographs, and other details. Over 70 hazards were identified, including agricultural field burning, abandoned homes, and noise from the Naval Air Facility. Almost 70 assets were identified, including community parks, sports playing fields, and local organizations and clubs. Proposed community actions include advocating for local regulation enforcement, education/awareness campaigns, and enhancing school flag programs. CONCLUSIONS: Training of local residents in environmental science and geospatial data collection and adaptation of an existing community web tool are steps that 1) build capacity to address local environmental issues, 2) promote engagement with and use of data gathered, 3) strengthen relationships between local environmental health experts, and 4) foster collaboration with environmental regulatory agencies at all levels. Mobile phones can be a valuable tool in community-based participatory environmental health research.

Evidence Supporting a Promotora-Delivered Entertainment Education Intervention for Improving Mothers' Dietary Intake: The Entre Familia: Reflejos de Salud Study

Entertainment education and the promotora model are 2 evidence-based health communication strategies. This study examined their combined effect on promoting healthy eating among mothers in a family-based intervention. Participants were 361 Mexican-origin families living in Imperial County, California, who were randomly assigned to an intervention or delayed treatment condition. The intervention involved promotoras (community health workers) who delivered 11 home visits and 4 telephone calls. Home visits included a 12-minute episode of a 9-part situation comedy depicting a family struggling with making healthy eating choices; an accompanying family workbook was reviewed to build skills and left with the family. Baseline and immediate postintervention data were collected from the mothers, including the primary outcome of daily servings of fruits and vegetables. Other dietary and psychosocial factors related to healthy eating were examined. At postintervention, mothers in the intervention reported increases in daily vegetable servings (p ≤ .05); however, no changes were observed in fruit consumption. Improvements were observed in behavioral strategies to increase fiber (p ≤ .001) and to decrease fat intake (p ≤ .001), unhealthy eating behaviors (p ≤ .001), and individual (p ≤ .05) and family-related (p ≤ .01) perceived barriers to healthy eating. Entertainment education and promotoras engaged families and improved mothers' diets. Further research should examine the dose needed for greater changes.

An efficient Bayesian inversion of a geothermal prospect using a multivariate adaptive regression spline method

In this study, an efficient Bayesian framework equipped with a multivariate adaptive regression spline (MARS) technique is developed to alleviate computational burdens encountered in a conventional Bayesian inversion of a geothermal prospect. Fast MARS models are developed from training dataset generated by CPU-intensive hydrothermal models and used as surrogate of high-fidelity physical models in Markov Chain Monte Carlo (MCMC) sampling. This Bayesian inference with MARS-enabled MCMC method is used to reduce prior estimates of uncertainty in structural or characteristic hydrothermal flow parameters of the model to posterior distributions. A geothermal prospect near Superstition Mountain in Imperial County of California in USA is used to illustrate the proposed framework and demonstrate the computational efficiency of MARS-based Bayesian inversion. The developed MARS models are also used to efficiently drive calculation of Sobol’ total sensitivity indices. Only top sensitive parameters are included in Bayesian inference to further improve the computational efficiency of inversion. Sensitivity analysis also confirms that water circulation through high permeable structures, rather than heat conduction through impermeable granite, is the primary heat transfer method. The presented framework is demonstrated an efficient tool to update knowledge of geothermal prospects by inversing field data. Although only thermal data is used in this study, other type of data, such as flow and transport observations, can be jointly used in this method for underground hydrocarbon reservoirs.

Uranium-Series Ages of Faulted Alluvial Fan Deposits, Mesquite Regional Landfill, Southeastern California

A multifaceted investigation of the western portion of the Mesquite Regional Landfill (MRL) site and vicinity (study area), located in the desert of southeastern Imperial County, California, included evaluation of slip geometry and activity of a fault located within the boundaries of the proposed landfill. Municipal waste will be placed on the southwest margin of the Chocolate Mountains on a gently southwest-sloping bajada consisting of seven laterally coalescing Quaternary alluvial fan units capped with variably developed desert pavement surfaces. Q1, the oldest, is estimated to be of early to middle Pleistocene age; Q7, the youngest, consists of historical and Holocene channel and flood deposits. Numerical ages of two intermediate units were calibrated using uranium-series (230Th/U) dating of pedogenic carbonate coatings on gravel clasts. The dates indicate minimum depositional ages of 106.2 ± 3.3 ka for Unit Q3 and 142.9 ± 6.1 ka for Unit Q2. A trench located over a buried step in crystalline basement exposed a near vertical, northwest-trending dextral fault with small (< 1 m) apparent vertical and horizontal separations cutting unit Q2. An extensive varnished desert pavement surface developed across overlying unit Q3 is undeformed across the projected trace of the fault. This observation and the uranium-series ages demonstrate that the minor fault was not active during the Holocene, a regulatory requirement for municipal landfills. The geomorphic expression, pedogenic development and numerical ages indicate that fan deposits and surfaces in the study area resemble alluvial fan sequences found elsewhere in the arid southwestern United States.

Identifying, Dating, and Explaining Fire-Affected Rock Features in the Western Colorado Desert, Alta California

Many hundreds of small features composed of fire-affected rock (FAR), often with no other cultural remains in proximity to them, have been documented along or within a few kilometers of the maximum +12-m shoreline of ancient Lake Cahuilla in southwestern Imperial County. Issues to be addressed in interpreting these features include confirming their cultural rather than natural origin, placing them within the prehistoric chronology of the region, and attempting to determine the functions they served.

Mexican and American Folk Architectural Traditions and Adaptations at Hedges: A Late Nineteenth–Early Twentieth-Century Mining Camp in the California Desert

In the spring of 1992, Burney and Associates of Boulder, Colorado, conducted archaeological investigations at the mining camp town site of Hedges in eastern Imperial County, California. The site represented a population of Mexican laborers and their families, as well as the influences of Anglo-American company management. Architectural data indicated that construction methods reflected the use of both the traditional Hispanic and the blending and adaptation of Mexican-Sonoran and Anglo-American architectural traditions. In communities like Hedges, where the vernacular architectural customs of the Sonoran Desert met those of the American East, the inventory of available folk design solutions increased dramatically for all residents. Although representing two distinct societies and cultures, the fundamental principles of both were embodied in long-standing customs. Efficiency and adaptability determined house form. These solutions embodied the essence of folk architecture. Through economy and innovation, design and materials were adapted to meet the builders’ specific needs.

Cylindropuntia chuckwallensis(Cactaceae), a New Species from Riverside and Imperial Counties, California

Abstract A gynodioecious hexaploid (n = 33), Cylindropuntia chuckwallensis M. A. Baker & M. A. Cloud-Hughes, is newly described. Populations of C. chuckwallensis extend from the Eagle Mountains of Joshua Tree National Park, through the Chuckwalla Mountains of Riverside County, to the north side of the Chocolate Mountains in Imperial County, California, USA, and occur on a variety of substrates primarily between 400–1600 m (1312–5250 ft) elevation. Of the flowering individuals studied, 38% produced only pollen-sterile flowers. Flower color in C. chuckwallensis ranges from dark red-purple (33%) through orange (54%) to yellow (13%). For most individuals (93%) the style and filaments are dark red to light pink. Morphological measurements were made for 15 populations of Cylindropuntia, including four of C. chuckwallensis, four of C. echinocarpa, three of C. multigeniculata, and four of C. acanthocarpa. Multivariate analyses indicated that C. chuckwallensis possesses a unique combination of characters. Fewer ...