Older drivers may have more difficulty than the general driving public in attending to the driving task, and they may be slower at processing information, especially when required to make complex decisions. Traffic crashes caused by elderly drivers have been attributed to neglect of, or inattention to, relevant information from road signs, as well as to other cars and pedestrians on the road. This is especially true at intersections. To combat these safety issues, implementation of the Florida Elder Road User Program began on state-maintained roads. This program sought to improve roadways by increasing visibility and adding advanced signage and reflective pavement markings. This study sought to evaluate the effectiveness of the Florida Elder Road User Program by building a crash prediction model that examines older driver crash frequency using variables obtained from quantitative variables such as maximum posted speed limit and qualitative variables such as sign visibility. Crash data was collected for 601 intersections in the state of Florida for the years 2000-2002. Detailed analysis of geometric and traffic data collected from various resources, such as crash reports, Roadway Characteristics Inventory data, and video log archives, was performed to determine the correlation between these independent factors and crash frequency. The crash distribution was found to be negative binomial; the model needed to be inflated due to the presence of many zero-crash intersections. Therefore, a Zero-Inflated Negative Binomial (ZINB) crash prediction model was developed. The response variable in the model was crash frequency, and independent variables included roadway geometrics, traffic characteristics, and intersection characteristics. Crash frequency was found to have a very strong relationship with most of the independent variables as indicated by their p-values. Traffic volumes, signalization, and sign visibility had positive coefficients, indicating that, higher traffic volumes, signalized intersections, and sign visibility were associated with increased crash frequency. Many of the improvements, including sign visibility and reflective pavement markers listed in the Florida Elder Road User Program were found to be significant but did not reduce elderly driver crashes, proving that the program is not effective. / A Thesis submitted to the Department of Civil Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Fall Semester, 2006. / Date of Defense: November 3, 2006. / Older Driver, Transportation Safety, Florida Elder Road User Program, Crashes, Intersection Design, Modeling, Intersections, Elderly Driver / Includes bibliographical references. / Lisa Spainhour, Professor Directing Thesis; Renatus Mussa, Committee Member; John Sobanjo, Committee Member.

This dissertation presents the work of investigating methane emission and oxidation through landfill covers. Methane as a major source of greenhouse and is being emitted from solid waste landfill at a tremendous rates. These emissions could be mitigated by methanotrophic bacteria in enriched and non-enriched soil covers. Compost biofilters were constructed to study the methane oxidation capacity of compost. The aged chipped yard waste compost was obtained from Leon County landfill (Florida, USA). A one-dimensional dynamical numerical model was developed to simulate the methane transport and oxidation through the biofilter. This model was designed to incorporate dynamic parameters and use flux bottom boundary, which is measured by a flow meter. General agreements of methane outflux and oxidations were obtained between model simulation and experimental data. Field scale control cells and biocells were evaluated in the same landfill for methane emission and oxidation. Methane oxidation in biocells was significantly higher than in control cells. When outliers were removed, methane emission from biocells was significant less than from control cells. A numerical model was developed to separate blockage of the thicker biocells cover and the biological oxidation. Results showed that the low emission from biocells is caused by blockage of soil cover underneath the compost cover as well the high oxidation capacity of this compost cover. An additional modeling investigation was conducted to evaluate how landfill final earthen cover's construction and climate conditions affect methane emission and oxidation under different boundary condition and different soil oxidation capacities. This numerical model combined a water and heat flow model (HYDRUS1D) and a gas transport and oxidation model. Simulations showed that soil covers in subhumid areas can prevent high methane emission with blockage and decent oxidation capacity. In semi-arid sites, higher emission was obtained due to the higher air filled void space of the soil. Oxidation capacities in semi-arid sites are higher than those in subhumid sites since influxes of methane are higher in semiarid sites. High pressure underneath the cover caused higher emission in all sites. Even with active gas collection system (vacuum pressure), emissions were significant in semiarid climates. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2006. / Date of Defense: November 3, 2006. / Model, Oxidation, Methane, Emission, Landfill Cover / Includes bibliographical references. / Tarek Abichou, Professor Directing Dissertation; Jeffrey Chanton, Outside Committee Member; Kamal Tawfiq, Committee Member; Wei-Chou V. Ping, Committee Member.

Water conservation, wastewater treatment regulations, and the use of reclaimed/reuse water supplies have been on a collision course since society’s demand began outstripping the supply of fresh water. As potable water demand has risen, engineers have looked toward Waste Water Treatment Plants (WWTP) to alleviate the stress placed upon aquifers and surface water sources. Direct Potable Reuse (DPR), Indirect Potable Reuse (IPR) and Reuse/Reclaimed systems all conserve water; however, they also unintentionally conserve pollutants. The widespread use of WWTP effluent conservation requires additional treatment options such as Activated Carbon treatment to further treat plant effluent. Powdered Activated Carbon (PAC) has shown promise as a treatment method to reduce pollutants but challenges remain in effectively applying PAC to a wastewater stream. Of particular concern is the application of PAC to existing facilities in which the existing hydraulic profile does not allow the use of large sedimentation tanks normally associated with PAC use in potable water applications. Cloth Media Filtration (CMF) is an existing treatment process that has seen significant saturation into the WWTP market in the United States since being introduced in 1991. While mostly targeted at tertiary treatment, alternate processes such as primary filtration and storm water treatment are now being pursued. It is suspected that CMF will capture and retain Powdered Activated Carbon (PAC) in which the two processes could be combined in order to produce an energy friendly and cost competitive approach to pollutant reductions. This research examines the feasibility of application of PAC into existing hydraulic profiles by using inline injection and its quick removal by Cloth Media Filtration (CMF). One of the most challenging aspects of PAC usage is its removal, which can be facilitated by a commercial CMF. A bench sized cloth media filter was constructed and then operated in a side stream manner with a real-world wastewater treatment train. The results show excellent performance of the designed CMF. The removal of two commercially available PACs was more than 70% within a short time using the existing hydraulic conditions of the plant. Additionally, using the backwash rates and solids removal rates, it was determined that CMF performs as an acceptable means of removal for PAC in a WWTP. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2017. / July 14, 2017. / ACTIVATED, CARBON, CLOTH, FILTER, MEDIA / Includes bibliographical references. / Hafiz Ahmad, Professor Directing Thesis; Gang Chen, Committee Member; Youneng Tang, Committee Member.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 125-138). / Tropical peatlands in Southeast Asia have sequestered carbon over thousands of years and are an important global carbon stock. In natural peat swamp forests, high water levels inhibit decomposition due to anoxic conditions. However, they are being rapidly deforested and drained, releasing stored carbon to the atmosphere. In this thesis, we investigate the carbon dioxide and methane fluxes from both pristine and degraded peat swamp forests in Borneo using field measurements, modeling and remote sensing. We first study methane fluxes from natural peatlands. We use an isotope-based mass transport model to evaluate the extent of methane production, transport and oxidation. We find an order of magnitude more methane is produced than surface fluxes suggest. This dissolved methane is transported belowground to the rivers and streams draining peatlands. However, much of this methane is oxidized before reaching the atmosphere. We then study CO₂ emissions from peatlands. At the local scale, we use automated soil respiration chambers to assess how CO₂ emissions depend on temperature and water table. At a regional scale, we use remote sensing to investigate carbon losses due to peatland degradation. Drainage of peatlands enables peat decomposition and results in subsidence of the land surface. We track this subsidence using InSAR satellite data and use it to quantify regional CO₂ emissions. The spatial resolution of our technique allows us to uncover correlations with past and present land uses and peatland hydrology. / by Alison May Hoyt. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 137-144). / The Persian Gulf (also known as the Arabian Gulf) is a shallow marginal sea located in a region of Southwest Asia with arid climate. Because of this aridity, evaporation from the Gulf is extremely high (1.84 meters per year) and far exceeds the sum of freshwater inflow to the Gulf, mainly from precipitation and some from river flow. A residual circulation exists between the Gulf and the Indian Ocean such that saline water flows into the Gulf from the Indian Ocean in order to balance the freshwater deficit due to high evaporation rate; and since evaporation only removes freshwater, the salt associated with this inflow from the Indian Ocean is removed in dense saline water that naturally sinks to lower layers and exits the Gulf into the Indian Ocean. / The Gulf is also the source of seawater and sink of hypersaline effluent (brine) for many desalination plants representing about 50% of the world's seawater desalination capacity, because many of the countries on the Gulf have increasing human populations but no renewable freshwater resources. It has been recognized long ago that the impact of brine discharge on the Gulf cannot be discussed separately from the dynamics of the residual circulation, but to date there is no basin scale environmental analysis for the impact of seawater desalination activity on the Gulf. A coupled Gulf-Atmosphere Regional Model that simulates the residual circulation between the Gulf and the Indian Ocean is used to investigate the impact of desalination on the salinity of the Gulf. Satellite data on sea surface temperature and water surface elevation are used to constrain the model, and to analyze trends in the Gulf. Four main contributions of this thesis are emphasized. / First, the equilibrium state variables describing the Gulf are identified, including a new estimate of Gulf basin salinity of ~~ 40.5 - 41g/kg. Second, it is shown that desalination has minimal impact on salinity averaged at the basin scale but significant impact at regional scale. Changes in regional salinities are used to quantify the impact of desalination in different regions within the Gulf. Third, a specific criterion for placement of brine discharge systems in the Gulf that minimizes regional salt accumulation is proposed in order to guide planning and design of future seawater desalination plants, as well as management of existing plants. Lastly, trend analysis shows a small trend in sea surface temperature (~~2°C during 1993 - 2014), most likely caused by climate change, but slight trends in Gulf basin salinity that are likely due to natural variability. / by Hamed D. Ibrahim. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017 / Cataloged from PDF version of thesis. / Includes bibliographical references. / Polychlorinated biphenyls (PCBs), which were a widely used group of chemicals before their manufacture was banned in 1979 in the United States, still contaminate numerous aquatic systems. Although there are ongoing efforts to remediate these sites, our ability to implement effective remediation strategies has been hindered by a limited understanding of how PCBs are transported in the environment as well as how they bioaccumulate into aquatic animals. Investigations of contaminated sites often rely on sediment measurements since PCB concentrations are highest in the sediment phase. However, previous research has shown that sediment concentrations are a poor predictor of contaminant fate and effects, whereas freely dissolved water concentrations were able to predict the extent of bioaccumulation and the onset of toxicological effects more accurately. / Additionally, the concentration gradient between the porewater (i.e., the interstitial water in sediment beds) and the overlying water is thought to be a major driver in PCB transport from the sediment bed. Passive samplers, which are made of polymers like polyethylene (PE), accumulate PCBs when they are deployed into environmental media, can be used to estimate freely dissolved water concentrations. When used in the laboratory by mixing with sediment samples, they provide a measure of the sediment-water equilibrium porewater concentration. When deployed in the field, they can provide measures of the in situ porewater and overlying water concentrations. In this work, PE samplers were deployed at two Superfund sites contaminated with PCBs to investigate if in situ porewater and sediments were at equilibrium with each other. / In situ porewater concentrations were consistently found to be lower than equilibrium concentrations at both sites, an effect that was likely caused by water flow through the sediment bed. At one of the sites, measurements of a geochemical tracer also showed that the exchange of porewater with overlying water was occurring and that the transport of PCBs from sediments was affected by more than just the concentration gradient. Lastly, the sorptive disequilibria between environmental media and the spatial heterogeneity of contamination were shown to affect the extent of bioaccumulation in aquatic animals at one of the sites. / by Jennifer Nicole Apell. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Since 1984 the author has provided engineering services to property owners, insurance companies, attorneys, and others. The scope of those services typically included identifying the cause and origin of damage to residential and commercial structures as well as an estimation of the magnitude of damage sustained by those structures. The majority of those damaged structures were located in proximity to a coastal region and have experienced recent exposure to a storm or other weather event. The long-term performance of any building (structure) is directly related to, among other things, the design or physical features of the building, construction practices, routine maintenance, and exposure to severe weather events. During periods of increased external loading and water exposure, such as those resulting from severe weather events, deficiencies in design, construction, or maintenance often result in what would otherwise be avoidable building damage. As a result of more than one thousand case studies involving site inspections, it has become apparent that building related deficiencies are often found to exist as a common feature in similar structures. Some of those recurring deficiencies could be eliminated with alternate building design, better construction practices, or proper routine maintenance procedures. Compilation of those case studies has allowed identification and ranking of the occurrence of chronic building problems. Where applicable, proposed remedial solutions are presented for specific building deficiencies or problems identified. It appears that a significant lack of feedback to engineers, architects, and builders exists regarding long term building performance. An increased awareness of existing chronic deficiencies in the design and construction of buildings and a subsequent effort to eliminate those deficiencies is essential to the future performance of new construction, in general, and specifically to the storm survivability of many structures in coastal regions. Much of what has been learned as a result of this analysis can be of considerable value to professionals or future professionals involved in the building design and construction communities. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the Requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2005. / Date of Defense: October 28, 2005. / Buildings, Storm, Damage, Deficiency, Coastal / Includes bibliographical references. / Nur Yazdani, Professor Directing Dissertation; Kamal Tawfiq, Committee Member; Dauta Leszczynska, Committee Member; Mark Martinko, Outside Committee Member.

High groundwater table exerts detrimental effects on the roadway base and the whole pavement. Base clearance guidelines have been developed to prevent water from entering the pavement system in order to reduce its detrimental effects. This dissertation presents an experimental study to evaluate the effects of high groundwater and the moisture on determining pavement base clearance for granular subgrades. Full-scale in-lab and test-pit tests were conducted to simulate pavement profile and vehicle dynamic impact on the pavement. Eight types of granular subgrades were tested for this study. From the test, using layer theory, the results of the resilient modulus for each layer (layer resilient modulus) can be compared with the resilient modulus results from laboratory test. Multiple regression model will be established to predict soil resilient modulus without doing resilient modulus test. The dominant factor or factors of the effect of moisture to resilient modulus will be discussed. The results showed that a 24-inch base clearance was considered adequate for the base protection of most A-3 and A-2 subgrades against high groundwater tables. The lab resilient modulus and layer resilient modulus have the same trend for each soil according to the moisture content change. The SR-70 A-2-4 (14% fines) soil was the most susceptible to the change of groundwater table than the other soils. The percent of fines or the percent of clays of subgrade soil is not good indicator to measure the influence of moisture effect on the resilient modulus. The coefficient of uniformity and coefficient of curvature of the subgrade gradations, which better represent the whole shape of the gradation curve, are better indicators of the effect of moisture to modulus. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Summer Semester, 2004. / Date of Defense: June 18, 2004. / Moisture Content, Soil, Subgrade, Resilient Modulus / Includes bibliographical references. / W. Virgil Ping, Professor Directing Dissertation; Xufeng Niu, Outside Committee Member; Amy Chan Hilton, Committee Member; Tarek Abichou, Committee Member; Makola Abdullah, Committee Member.

A relatively new technique of electro-kinetic remediation is examined to evaluate and enhance removal of residual of the CCA (chromated copper arsenate) from clayey soil. A short duration (25-hours) treatment approach was initiated for this purpose. Laboratory 1-D column tests were performed on kaolin soil under the influence of DC electric field. Different chemicals (acid, alkali and oxidizing agents) and tap water were purged through electro-osmotic flow to enhance chromium, copper, arsenic remediation. Configuration of electrodes/reactor setup was also adjusted to improve the removal efficiency of the CCA chemicals by inducing buoyancy with electro-osmotic flow. Interesting results were obtained showing up to 78% of arsenic and 72% copper removal by purging sodium hypo-chlorite (NaOCl). Sodium hydroxide (NaOH) purging also indicated enhanced removal with 74% arsenic and 72% copper removal. It was difficult to remove chromium and maximum removal was only 3.75% when the soil was purged with tap water. The batch experiments show that with respect to individual contaminant remediation, the removal efficiency increases many times when contaminants in the soil are in mixed-form. Inclined reactor setup showed enhanced electro-osmotic flow due to the effect of buoyancy. A model combining main phenomena of contaminant movement: electro-migration, electro-osmosis, diffusion, and buoyancy was developed for a small Debye length. The model predicts the behavior of pH, which is an important parameter that governs the migration of contaminants. Calculation based on the model showed excellent agreement when compared with the pH profile of experimental data of tap water purging for copper remediation. Although additional modeling and experimentation is needed, the results of this thesis demonstrate that electro-kinetic remediation with suitable purging chemicals may offer enhanced removal of polluted soil. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2004. / Date of Defense: November 10, 2004. / Redox-Potential, Electro-migration, Ellectro-osmosis, Effluent / Includes bibliographical references. / Danuta Leszczynska, Professor Directing Dissertation; James F. Tull, Outside Committee Member; Andrew Dzurik, Committee Member; Amy Chan-Hilton, Committee Member.

"Green engineering" is the newest technology implemented for sustainability in the design of buildings and most recently highways. Sustainability concepts applied to the design and construction of roadways includes long term planning, new technologies and methods, construction management techniques and resource reuse. Green engineering is part of the global goal of long-term sustainability, which is to meet the needs of today without compromising those of the future. Leadership in Energy and Environmental Design (LEED®) rating systems have been heavily promoted and utilized in the construction industry, but only with applications to buildings. There is no such criteria for rating roadway construction. Only one documented attempt has been made to adapt the LEED rating system to highway construction but with limited results. While predominantly used and accepted, the LEED rating points are not quantitative and are not based on any traditional decision making theory. This research presents an evaluation of using the LEED rating system techniques for highway construction. A multi-criteria decision making model (MCDM) is then formulated as a framework for evaluating sustainability in roadway construction. Within Leon County, Blueprint 2000 is an intergovernmental organization to efficiently manage and plan roadway construction projects within Tallahassee, Florida. In cooperation with Blueprint 2000, one of their projects will be used as the local sustainable roadway example. This project will serve as the case study and be evaluated for successful applications of sustainable engineering utilized during roadway design and construction. This research will also include an analysis of the multi-criteria rating system developed on a local roadway project. Research will be comprehensive on the topics of stormwater design, erosion control and the usage of various construction materials. The completion of this research will offer a new insight into rating sustainability and also on both new technologies and innovative practices within the transportation and construction management fields. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Summer Semester, 2009. / Date of Defense: April 30, 2009. / Roadway Rating, Roadway Sustainability / Includes bibliographical references. / John O. Sobanjo, Professor Directing Thesis; Lisa Spainhour, Committee Member; Gang Chen, Committee Member.