Meet Our Graduate Students

Thesis: Multivariate Analysis of the 2021 Boise Drought in the Context of Natural-Human Systems

Proposal Defended Successfully Spring 2022

Droughts generally refer to lack of sufficient water for a certain purpose, and hence can be defined in several categories including meteorological, hydrologic, agricultural and socioeconomic. While drought is triggered by the lack of or reduced precipitation, other factors including low soil moisture, groundwater depletion, insufficient snowpack, reduced surface storage, increased evaporation, and contaminated surface water also contribute to various drought categories. Since drought can induce major and widespread impacts on communities, it is important to study drought occurrences and their causes to be able to better prepare for the inevitable future droughts.

Droughts impact many functional aspects of a community including agricultural production, recreation, access to clean drinking water, and the health of local ecosystems. Without access to a sufficient amount of water, agricultural production declines, especially in arid and semi-arid regions such as Idaho.  According to the Idaho State Department of Agriculture, agriculture makes up approximately 18% of the state’s total economic output, and hence drought is a major concern in Idaho.

As of October 12th, 2021, >90% of Idaho was in a severe, extreme, or exceptional drought according to the U.S. Drought Monitor. This drought was specifically impactful for Idahoans, since  a reasonable amount of snowpack and dam storage in the spring convinced local farmers to fully cultivate their farms. But lack of spring precipitation and excessive evapotranspiration forced farmers to use all of their available water allotted for the year as well as water they had stored in the dams from previous years in order to irrigate their crops during the course of the 2021 growing season, leaving them vulnerable if the drought continues into 2022. All signs, unfortunately, indicate that the drought will continue this year, with consequential impacts.

The purpose of this thesis is to study the drought experienced by the Boise River watershed in 2021 in the context of natural-human systems. We consider two natural storages, namely (1) snowpack and (2) atmospheric storage, i.e., spring precipitation, as well as the built storage, namely the three dams that regulate Boise River. We obtained historical (1982-2021) data for snow water equivalent for the Boise River watershed and the total dam storage at April 1st, as well as spring precipitation, which collectively support irrigation of agriculture in the Treasure Valley. We conduct univariate and multivariate frequency analysis to obtain a nuanced understanding of the drivers of the 2021 Boise drought. This will provide important insights for the future conditions of drought initiation and evolution in the region in a warming climate.

Thesis: Harsh-Braking Data from Connected Vehicles as a Surrogate Safety Measure with Validation from Historic Crash Data

Proposal Defended Successfully March 2022

Traffic safety may be analyzed with the use of surrogate safety measures, measures of safety that do not incorporate collision data but rather rely on the concept of traffic conflicts.  Use of these measures provides several benefits over use of more traditional analysis methods with historical crash data.  Surrogate measures eliminate the need to wait for crashes to occur to conduct safety analyses.  Similarly, these measures allow for safety analysis to be conducted prior to crashes occurring, potentially calling attention to hazardous areas which may be altered to prevent crashes.  In addition to these benefits, traffic conflicts occur much more frequently than collisions, generating many more data points which in turn make statistical methods of analysis more effective.

Evaluating surrogate safety measures for a particular transportation network is most effectively done with the use of traffic microsimulation or with connected vehicle data.  Traffic microsimulation (such as the use of PTV VISSIM) will generate kinematic data that may then be used for computation of surrogate safety measures.  A significant amount of research has been done on this topic, resulting in the establishment of algorithms for calculation of several different surrogate measures and validation of these measures.

Kinematic data from connected vehicles has also been used for the calculation of surrogate safety measures and is promising as a more effective alternative to microsimulation for surrogate safety measure analysis.  One data point collected by connected vehicles is harsh braking events which could serve as a surrogate safety measure.  Because drivers usually brake more gently if given the opportunity to do so, harsh braking events indicate that a traffic conflict has occurred which has taken away the driver’s opportunity to brake gently.  Past research has indicated that conflicts and collisions are correlated which means that an indication of a conflict should also be correlated to collisions.  Use of harsh braking as a surrogate safety measure may be validated through comparison of the predictions of a harsh braking safety model to historical crash data.

This study involves the use of connected vehicle data from Salt Lake City, Utah to develop a definition of a harsh braking event based on the value of the first derivative of acceleration, jerk, and also seeks to develop harsh braking safety models through regression with harsh braking event datasets and historical crash count datasets.

Thesis: Evaluation of energy release from wildfires across the elevation gradient

Thesis Successfully Defended March 31, 2022

Abstract: Wildfires are an integral process in vegetative terrestrial land which shape ecosystem
functions. A warming climate, however, has increase the size and occurrence of these fires with
significant ecosystem and societal implications. Furthermore, warming has changed
characteristics of wildfires enabling a median upslope advance of 252 m in high-elevation forest
fires from 1984 to 2017, allowing wildfires to burn in areas that were previously too wet to burn
frequently. This exposed an additional 81,500 square kilometers (11%) of western US montane
forests to fires.

In this thesis, I test the hypothesis that wildfires burn hotter in high elevation, mesic
forests. To this end, I will assess fire intensity, which refers to how much heat energy is released
during a fire, across the elevation gradient. I will use fire radiative power (FRP) that measures
the amount of radiant energy released from burning vegetation during a wildfire event as a proxy
for fire intensity. FRP data will be acquired from the MODIS satellite between 2000 and 2020,
which is then paired with elevation data using digital elevation maps, and forest potential maps. I will derive this data for the 15 mountainous ecoregions of the western US. I will then conduct
various hypothesis tests to determine whether or not there is a statistically significant trend in
FRP as a function of elevation. I will also assess whether or not the distribution of FRP for high-
elevation and low-elevation wildfires are equal.

High-elevation wildfires and their intensity are important for societal and ecological
systems that are affected by wildfires. They impact, for example, quantity and quality of water
resources for 70% of the western US population that depend on high-elevation areas as their
source of water. Understanding this phenomenon can inform wildfire and land management in a
warming climate.

Thesis: Wastewater Analysis of Emerging Constituents

Proposal Defended Successfully – Fall 2021

Abstract: Emerging Constituents (ECs), also called Contaminants of Emerging Concern (CECs) are defined by the United States Environmental Protection Agency (U.S. EPA) as, “…pharmaceuticals and personal care products.” It is highly likely that regulatory limits will be placed on many ECs as they tend to accumulate in the environment and human tissues with little to no transformation. ECs pose a threat to the health of ecological systems and the fundamental need for clean water, which is an essential resource for life. Whether directly or indirectly, clean water affects all aspects of life. ECs in the U.S. primarily enter water bodies through wastewater treatment facilities, whether on-site (e.g., septic systems) or centralized municipal utilities (e.g., City of Boise’s Water Renewal System). Research shows various psychotropic drugs, prescribed and illicit, are present in both receiving and discharge streams of many North American wastewater treatment facilities. Therefore, there is an increasing need to understand the concentration levels entering water renewal systems as well as the concentrations throughout the treatment processes. Preliminary research conducted at Boise State University has aimed to analyze select EC concentrations within the Lander Street Water Renewal Facility (LSWRF). Specifically, the EC concentrations entering and throughout the treatment processes, transformations or removals, and variations due to temporal effects. Trends were observed from the preliminary research that have guided its expansion in this proposed research. Additionally, Boise State University has partnered with the City of Boise, which conducted its own study in 2020 of over 300 different EC concentrations in the LSWRF influent and effluent. Goals of the preliminary research will be expanded through this proposed research. First, the number of ECs analyzed will be increased by approximately a factor of four and will include antibiotics, anti-inflammatories, anticonvulsants, and antidepressants. Second, the transformation or removal of ECs through solids treatment processes will be analyzed. Lastly, the sampling period will be increased to assess winter, spring, and summer samples to further understand temporal variations.

The purpose of this research is to quantify mobile emissions from local drive-thrus and correlate them with a main source, such as Interstate 84 (I-84). Specifically, this research will investigate the contribution of PM10 and PM2.5 to mobile emissions. Furthermore, this research will verify the Motor Vehicle Emission Simulator (MOVES) recommended for use by the United States Environmental Protection Agency (U.S. EPA) with observed data to assess the model’s ability to predict a variety of mobile emissions. Moreover, this research will elucidate the impact drive-thrus have on mobile emissions and assess the potential for regulations to limit public exposure.

Thesis: Emerging Constituents Behavior Within Water Renewal Facilities

Thesis Proposal Defended Successfully Fall 2021

Abstract: Emerging Constituents (ECs), also called Contaminants of Emerging Concern (CECs) are defined by the United States Environmental Protection Agency (U.S.EPA) as: “…pharmaceuticals and personal care products.” This also includes per- and polyfluoroalkyl substances (PFAS), which are used in waterproofing and non-stick cooking products. It is highly likely that regulatory limits will be placed on many ECs because they tend to accumulate in the environment and human tissues with little to no transformation. ECs pose a threat to the ecological systems of our nation and the fundamental need for clean water by all life on earth. Clean water is essential for food production, whether directly, through activities such as fishing, or secondarily, through irrigation for crop production. Research shows that ECs have affected the endocrine systems of certain fish species throughout the United States. Some studies indicate that upward of 85% of male fish sampled had eggs growing within their reproductive organs. ECs in the United States primarily enter water bodies through wastewater treatment facilities, whether on-site (e.g. septic systems) or centralized municipal utilities (e.g. City of Boise’s Water Renewal System). Research shows various psychotropic drugs, prescribed and illicit, are present in both receiving and discharge streams of many North American wastewater treatment facilities. It is unclear the extent to which ECs are removed or accumulate through wastewater treatment processes. This is further exacerbated by the abundant release of ECs into collections systems across our nation, and the rate at which new ECs are being generated for personal care and medical uses.

This research examined a targeted set of ECs within the Lander Street Water Renewal Facility (LSWRF), the older of the City of Boise’s two water renewal facilities. The project detected and mapped certain ECs as they processed through the LSWRF. Their paths through the facility, behavioral tendencies, and variations in concentration are presented here. While the concentrations detected are low in comparison to medical dosing concentrations, the accumulation potential of these substances in the natural receiving systems remains unknown. Water and soil must be healthy for life to thrive. We have been given the responsibility by our creator to be good stewards of the earth and it’s resources. ECs pose a threat to life. We must continue conducting research to find a way to prevent ECs from causing harm to our natural systems. Research such as this is a beginning point of good stewardship.

Thesis: Relationship of Hydraulic Conductivity and Rise of Excess Pore-Water Pressure during Seismic-induced Liquefaction

Proposal Defended Successfully Fall 2021

Liquefaction is a geohazard causing loss of lives and infrastructures around the world. Liquefaction results from a sudden increase in excess pore-water pressure (EPWP) in loose, saturated non-cohesive, fine soils during seismic shaking. Due to small pores and low hydraulic conductivity of these soils, the shaking-induced EPWP has less time to dissipate, leading to the loss of the effective stress and, in turn, frictional shear strength of the soil (referred to as liquefaction). If a soil’s hydraulic conductivity could be increased during seismic shaking, ample time would be afforded for EPWP dissipation. A potential theory, introduced by our research team, is that electromagnetic (EM) waves can increase granular soils’ hydraulic conductivity. This increase can potentially lead to liquefaction mitigation. Seismic accelerations will be induced using a shake table on a liquefaction-susceptible soil. This will be repeated while the specimen is excited using EM waves of various frequencies and power levels. Thus, the relation among seismic shaking, hydraulic conductivity, and generation and dissipation of EPWP will be evaluated. Three-dimensional numerical models of seepage and EM wave propagation are developed and validated to measure hydraulic conductivity under EM excitation and shaking.

Thesis: Innovative Foundation Alternative Inspired by Tree Roots

Proposal Defended Successfully – Summer 2021

Abstract: It is not easy to find a more efficient foundation system than the roots of a tree. Trees create a vast three-dimensional network of roots to support and anchor the critical above-ground trunks, leaves, and limbs. In this work, investigations are made for the feasibility of imitating such a technique and creating similar networks to support civil infrastructure, particularly those subjected to moment loads such as traffic signal posts. Some of the raised questions were: Is it feasible to have a shallow tree root-based foundation system to provide the same capacities as conventional foundation alternatives? If this is feasible: What would be the ideal depth of the Root Foundation System? How far should the roots extend to provide comparable support to a conventional deep foundation system? What diameter should the root bulb of the configuration be? How far should a vertical shaft extend into the ground?

Hence, the main objective of this research is to identify and test the most effective Root Foundation System geometric configurations that can provide a similar capacity as a conventional foundation for traffic signal posts. Finite element model simulations on 54 different root-based foundation models show potential for replacing the conventional drilled shaft foundation for traffic signal posts. The conventional foundation was also modeled and produced a 0.528 mm deflection. Whereas some of the best performing root foundation models achieved 0.23 mm. By comparing the resulting deflection of the conventional foundation model to the deflection of the root foundation models, the best performing root foundation models will be 3D printed and physically tested. After physical testing is complete, the root foundation models can be calibrated to predict the performance of root foundation models.

Thesis: Multiphysics Numerical Model for PFAS Transport within Vadose and Saturated Zones

Proposal Defended Successfully August 3, 2021

Per- and polyfluoroalkyl substances (PFAS) are persistent, mobile, toxic, manmade chemicals used in a large variety of applications (e.g., aqueous film-forming foams, AFFF, used to suppress fires contain PFAS).

The need to understand the fate and transport of PFAS has grown due to their widespread, persistent contamination of the environment The presence of PFAS in unsaturated soil complicates their transport due to their adsorption to the air-water interface (forming micelles) and solid phase. The air-water interface presence can significantly increase the retention of PFAS during its transport. The focus of this research is to develop a one-dimensional numerical model to study the transport of PFAS by coupling PFAS transport—considering advection, molecular diffusion, and mechanical dispersion, solid-phase adsorption, and micelle formation—and transient seepage. The numerical model will then be used to simulate and analyze various scenarios and validated against lab-scale experimentation results.

Thesis: Developing Implementable Policies Targeting Sustainable Building Construction by Learning from Other Countries

Thesis Defended Successfully Fall 2021

Climate change has continued to become more complex and damaging to the environment globally with all sectors having a negative impact on the planet. This certainly is not an issue Civil Engineers can solve alone; however, it is crucial for Civil Engineers to do their part in reducing impacts on the environment. The construction industry accounts for 38% of global energy use and the related carbon emissions hence it is important that sustainability is prioritized in this sector (United Nations Environment Programme, 2021). The current state of practice targeting sustainability within this sector is limited to sustainability policies of contracting firms which are not always implemented. Without federal policies or codes to ensure sustainable practice, nationwide implementation will continue to falter and not proceed at the rate the planet needs. While the United States is striving to be more sustainable, other countries have had great success in the matter. The United Nations Sustainable Development Solutions Network (SDSN) ranks countries based on seventeen Sustainable Development Goals (SDGs), ranked the United States at 32 while countries like Finland, Sweden, Denmark, Germany, and Belgium are ranked in the top 5 respectively (Sachs et. al, 2021). To promote sustainable policies within civil infrastructure in the U.S., it is proposed to analyze policies targeting sustainable building construction in the top five sustainable countries with a goal to adapt successful policies to U.S. governance. By narrowing down the research to building construction, dissection of related sustainable policies will be attainable, and the process can be reproduced for other facets of infrastructure as well as for other sectors.

Thesis: Ions and Residence Time Responses to a Semi-Arid Beaver Meadow

Thesis Defended Successfully Fall 2021

Abstract: North American beavers have historically been prolific ecosystem engineers and have shaped the riverine landscape in the western United States. Beaver dams transition narrow channels too wide valleys by slowing the flow of water and creating beaver meadows. These meadow complexes promote stable lateral hydrologic connectivity. When channels exhibit lateral connectivity water and
nutrients are free to flow from the channel to the riparian areas and the floodplain. As a result, beaver dams alter hydrology and hydraulics at the watershed scale. Nutrients and water are dispersed which supports an increase in species diversity and composition, provides redundancy against floods and alluvial incision and promotes biogeochemical processing and metabolism; which correlates to changes in water quality. Several studies have aimed to better describe the effects of beaver meadows on water quality and flow regimes and significant progress has been made in detailing the relationship between fine scale nutrient transport and processing. However there continues to be a lack of physically based correlations between stream discharge, water residence times, and water chemistry in these complexes. There also seems to be a lack of empirical information on specific environments, where several studies have been performed on the perennial North Saint Vrain Creek which drains Wild Basin the Rocky Mountain National Park, CO but few (if any) studies have characterized a semi arid intermittent stream. This project distinguishes itself by researching a semi-arid intermittent stream and by relating temporal shifts in the relative impacts of beaver meadows on water quality and residence times. Understanding this relationship within the Boise, Idaho foothills will help support efforts to sustain and restore natural channels in the mountain west.

Thesis: Understanding Mesoscopic Chemo-Mechanical Distress and Mitigation Mechanisms of Concrete Subject to ASR

Thesis Successfully Defended October 2020

Thesis Abstract: Alkali-silica reaction (ASR) is one of the common sources of concrete damage worldwide. Surrounding environment, namely, temperature and humidity greatly influence the alkali-silica reaction induced expansion. Global warming (GW) has caused frequent change in the climate and initiated extreme weather events in recent years. These extreme events anticipate random change in temperature and humidity and convey potential threats to the concrete infrastructure. Moreover, external loading conditions also affect the service life of concrete. Thus, complex mechanisms of ASR under the impact of seasonal change and global warming require a precise quantitative assessment to guide the durable infrastructure materials design practices. Despite decades of phenological observation study, the expansion behavior of ASR under these situations remains to be understood for capturing the ASR damage properly. Within this context this research focuses on the mathematical model development to quantify and mitigate ASR-induced damage. Mesoscale characteristics of ASR concrete was captured in the virtual cement-concrete lab where the ASR gel-induced expansion zone was added as a uniform thickness shell. Finite element method (FEM) was used to solve the ASR formation and expansion evolution. The results of this study are presented in the form of one conference and their journal manuscripts.

The first manuscript focuses on the development of the governing equations based on the chemical
formulas of alkali-silica reaction to account for the ASR kinetics and swelling pressure exerted by the ASR expansion. There is a fluid flow and mass transfer in the concrete domain due to ASR gel associated from ASR kinetics. This paper involves derivation of the mass and momentum balance equation in terms of the thermo-hygro-mechanical (THM) model. THM model accounts for thermal expansion and hygroscopic swelling in addition to traffic loads to represent volumetric change in the concrete domain.

The second manuscript is a case study based on different cement-aggregate proportions and alkali
hydroxide concentrations. It is important to know how ASR evolves under variable concentration of the chemical species. The simulated results show that high concentration of hydroxide ion in concrete initiates more reaction and damage in concrete. Also, chemical reaction moves to the right direction with low cement to aggregate ratio which means ASR expansion depends on the availability of the reactive aggregates in the concrete domain.

The third manuscript attempts to develop a simplified ASR model that integrates chemo-physio-
mechanical damage under stochastic weather impact. Stochasicity incorporates the random behavior of surrounding nature in the model. The simulated results elucidate that ASR expansion is more severe under the influence of global warming and climate change. This will support long-term damage forecasts of concrete subjected to extreme weather events.

The fourth manuscript focuses on the quantification of mechanical damage under ASR expansion and a dedicated mitigation scheme to minimize it. Added creep loads and physics identify the role of creep damage on ASR expansion.

The result from this paper confirms that the ASR-induced damage significantly minimizes the load carrying capacity of concrete. It directly affects the compressive strength, tensile strength, and modulus of elasticity of concrete. Damage in aggregates domain is more than the mortar phase under the creep loadings. Among many supplementary materials, fly ash is the most effective in minimizing ASR expansion and damage. This work also includes a petrographic comparison between different mineral types collected from different locations to identify the reactivity of certain aggregates.

Thus, the outcome of this research is a complete model which is a conclusive solution to the long-term ASR damage prediction. The validated model provides better understanding of ASR kinetics from mesoscale perspective. The developed model can potentially accelerate the precise prediction of concrete service life and mitigation schemes as well as can be used as an alternative scope to the costly laboratory tests methods.