Civil & Environmental Engineering Dissertations Collection

Performance monitoring and analysis of integral abutment bridges

Kalayci, Emre — Wed, 16 Jan 2013 12:24:49 PST

Integral abutment bridges (IABs) have been constructed by State Departments of Transportation for a number of years. These bridges have been found to be cost effective from both an initial cost and life-cycle cost analysis. However, common design guidelines are lacking and non-uniform limitations on IAB design are imposed by different agencies. In order to evaluate design guidelines, the Vermont Agency of Transportation (VTrans) has initiated a program of field instrumentation and analysis to evaluate the performance of three IABs currently under construction. The research components are being conducted by the University of Massachusetts at Amherst. Three bridges are included, a straight bridge with 43 m (141 ft) span, a 15 degree skew bridge with 37 m (121 ft) span, and a curved two-span continuous structure with 11.25 degrees of curvature and 68 m (221 ft) total bridge length. The bridges are instrumented with 83, 89, and 131 gages, respectively. Instrumentation includes strain gages, pressure cells, displacement transducers, inclinometers, tiltmeters and thermistors. This dissertation describes the project scope, the bridge details and instrumentation of these sites, the finite element modeling scheme, the results of monitoring during construction and live load testing as well as the long-term monitoring for cyclic thermal loads with finite element modeling comparison.^

Risk Quantification of Maple Trees Subjected to Wind Loading

Ciftci, Cihan — Wed, 12 Dec 2012 05:34:35 PST

Because of property damage and people injuries in, almost, every year in different locations of the earth, unfortunately the topic of understanding trees and their risk assessments under wind forces has not lost its importance since approximately a half of the last century. In contrast to loss its importance, the number of researchers or studies increases with time thanks to inter-disciplinary studies on that topic. In this Thesis, tree dynamics and their risk assessments subjected to wind forces were addressed by two different disciplines (civil engineering and environmental conservation).

To mention includes of this inter-disciplinary study, first, a finite element modeling was developed for a real tree in Belchertown, MA. Then this modeling was compared with the experimental tests. After comparing the model and the tests of the real tree, same methodology of the modeling was, again, applied to a different tree in Amherst, MA. Second, a number of wind samples were generated randomly in order to apply to the models of the trees. Then, by comparing the moments at the stem of the trees and calculated maximum moments of the stems, the fragility curves of the failures of these trees was obtained with respect to mean wind-speed of the random wind samples. Third, the decay effects on the fragility curves were investigated by considering decreasing moment capacity of tree cross-sections due to decays. Finally, crown structure effects on tree dynamics were examined by several parametric studies which were applied to the tree in Belchertown, MA. These parametric studies refer to separately changes in several physical (such as stem diameter, branch slenderness ratio etc.) and material property (MOE) of the tree. Thus, thanks to these parametric studies, tree dynamics were understood better and the complex relationship between the stem and branches of the tree was explained better. Those better understandings, off course, produced several important practical outcomes for the life of the trees and as well as human-being.

1. Microbial characterization at a site exposed to highway runoff and deicing agents 2. Chloride dispersion across silt deposits in a glaciated bedrock valley

Rotaru, Camelia — Mon, 24 Sep 2012 11:01:03 PDT

Highway surfaces accumulate a wide range of pollutants (suspended solids, heavy metals, inorganic salts, aromatic hydrocarbons, oil and grease, rust and rubber particles, deicing agents, etc), which are washed off during rain or snow storm events into nearby waters or lands. This dissertation presents the impact of highway runoff to soil and groundwater. The dissertation is composed of two major distinct parts. ^ First part assessed the bacterial community diversity in highway runoff contaminated sediment from an infiltration basin located in Plymouth, MA that had undergone nineteen years of acetate-based de-icing agents addition followed by three years of acetate-free de-icing agents. Sediment sample from four drilled soil cores collected in two field events documented the change in bacterial community structure with depth and distance from the infiltration basin origin. ^ To meet the objective, a variety of multi-disciplinary techniques were employed. Soil samples were collected, using drilling and core barrel / freeze-shoe coring methods, from different locations and depths to obtain vertical profiles of bacterial distribution along groundwater plume. Analyses of groundwater dissolved oxygen and pH, physical and chemical properties of the soil complemented molecular phylogenetic determinations to distinguish ambient and contaminated plume zones. ^ Analysis of sediment samples from four drilled soil cores by means of 16S rDNA PCR indicated an overall high bacterial diversity both into the plume and into the ambient aquifer, with no prominent members within the communities. Sequence analyses provided evidences that each sediment sample displayed a specific structure bacterial community. Proteobacteria-affiliated clones (50%) predominated in all samples, followed by Actinobacteria (14%), Firmicutes (10%) and Chloroflexi (9%). Statistical analysis revealed that the levels of Fe(II) and dissolved oxygen were strongly correlated with bacterial communities. The plume in the infiltration basin was anaerobic and iron reducing. As iron levels declined as oxygen levels increased below the plume bottom, there was a gradual shift in the community structure toward the increase of aerobic bacteria. These data indicate shifts in microbial communities in correlation with depth, substrate and oxygen availability in a deicing agent impacted subsurface. ^ The second part of the dissertation investigated the subsurface fate and transport of deicing materials on groundwater quality across silt deposits in Dedham, Massachusetts. The deposit analyzed consists of two layers: a silty sand floodplain that is underlain by an aquitard, comprised mainly of silt. The aquitard overlies a confined aquifer, that is used as a public water supply. Soil and groundwater from the Neponset River aquitard and overlying floodplain deposit that receive high concentrations of deicing agents from nearby highways were collected and analyzed. Soil and groundwater samples collected over a period of four years from boreholes and 10 wells grouped in two well clusters were analyzed for dissolved chloride concentration. These data calibrate a one-dimensional, vertical dispersive transport model across the deposits. The flow and contaminant transport in floodplain is controlled by the aquitard presence and its low permeability. Soil and groundwater quality data confirmed a high chloride concentration at the floodplain surface near the highway runoff drainage outlets. These data confirmed the aquitard's capacity to contain deicing agents over decadal time frame, protecting the underlying aquifer from contamination.^

Evaluating Alternative Transportation Financing Approaches: A Conceptual Framework and Analytical Methods

Plotnikov, Michael — Thu, 06 Sep 2012 06:24:19 PDT

As states continue to consider taking on more responsibility in transportation, a major issue State Departments of Transportation (DOTs) face relates to financing future transportation investments. At present, many state transportation policymakers and State DOT administrators are considering alternative financing approaches to generate future revenue sources for transportation investments.

This dissertation focuses on several user fee based approaches currently being considered by state transportation policymakers and administrators in the U.S. Examples of such approaches include: increasing the current fuel tax and indexing the fuel tax to inflation; implementing an odometer based vehicle miles traveled (VMT) fee approach through vehicle inspection programs in selected states; establishing a global positioning system (GPS) based VMT fee approach for heavy vehicles where privacy and implementation costs are less of a concern; and increasing existing tolls and charging tolls on existing roads that do not have tolls, preferably with open-road tolling (ORT) and all-electronic toll (AET) payment systems. Meanwhile, major questions of interest relate to the potential impacts or consequences of such financing approaches.

Central to this dissertation is the development of a conceptual framework and analytical methods to aid state transportation policymakers and administrators in the planning and formulation of alternative financing approaches suitable for consideration in their state. The application of the framework and methods is illustrated in a case study. This case study includes an evaluation of alternative toll scenarios on a section of Interstate 93 in the Boston Metropolitan area where at present tolls are not charged. A major conclusion of the case study is that placing tolls along interstate highways where tolls are not currently collected has the potential to provide a significant source of revenue for State DOTs but that other impacts including route diversion, privacy, and equity need to be considered and addressed in the decision-making process. It is expected that the results of the dissertation will be of interest to state transportation policy makers as well as State DOT administrators currently involved in the development of a comprehensive transportation finance policy.

Effect of Building Morphology on Energy and Structural Performance of High-Rise Office Buildings

Krem, Mohamed — Tue, 04 Sep 2012 07:00:09 PDT

The civil engineering and architectural communities are highly focused, these days, on designing buildings that maximize utilization of energy available from natural resources. This dissertation presents a quantitative study of the effect of high-rise office building morphology on energy and structural performances for the major climates. The parameters of the building morphologies are varied - the building footprint shape, the placement of the structural core/walls, and the building orientation. The energy analysis is performed using Autodesk Ecotect Analysis 2011; while using SAP2000 for the structure analysis and design. The key observations are: 1) the building morphology has a significant effect on the annual energy consumption, 2) placement of the structural core/walls in the east and west sides significantly improve the energy performance, 3) the tradeoff in the cost of placing the structural core/walls to maximize operating energy efficiency is too great, 4) for built to code buildings the energy demand may be considered marginally sensitive to changes in aspect ratio, and 5) high quality thermal properties of code-built envelope systems offer more flexibility to designers with regard to the building site planning without creating negative impacts on total energy demand.

Real-time information and correlations for optimal routing in stochastic networks

Huang, He — Mon, 16 Apr 2012 14:15:01 PDT

Congestion is a world-wide problem in transportation. One major reason is random interruptions. The traffic network is inherently stochastic, and strong dependencies exist among traffic quantities, e.g., travel time, traffic speed, link volume. Information in stochastic networks can help with adaptive routing in terms of minimizing expected travel time or disutility. Routing in such networks is different from that in deterministic networks or when stochastic dependencies are not taken into account. ^ This dissertation addresses the optimal routing problems, including the optimal a priori path problem and the optimal adaptive routing problem with different information scenarios, in stochastic and time-dependent networks with explicit consideration of the correlations between link travel time random variables. There are a number of studies in the literature addressing the optimal routing problems, but most of them ignore the correlations between link travel times. The consideration of the correlations makes the problem studied in this dissertation difficult, both conceptually and computationally. ^ The optimal path finding problem in such networks is different from that in stochastic and time-dependent networks with no consideration of the correlations. This dissertation firstly provides an empirical study of the correlations between random link travel times and also verifies the importance of the consideration of the spatial and temporal correlations in estimating trip travel time and its reliability. It then shows that Bellman's principle of optimality or non-dominance is not valid due to the time-dependency and the correlations. A new property termed purity is introduced and an exact label-correcting algorithm is designed to solve the problem. ^ With the fast advance of telecommunication technologies, real-time traffic information will soon become an integral part of travelers' route choice decision making. The study of optimal adaptive routing problems is thus timely and of great value. This dissertation studies the problems with a wide variety of information scenarios, including delayed global information, real-time local information, pre-trip global information, no online information, and trajectory information. It is shown that, for the first four partial information scenarios, Bellman's principle of optimality does not hold. A heuristic algorithm is developed and employed based on a set of necessary conditions for optimality. The same algorithm is showed to be exact for the perfect online information scenario. ^ For optimal adaptive routing problem with trajectory information, this dissertation proves that, if the routing policy is defined in a similar way to other four information scenarios, i.e., the trajectory information is included in the state variable, Bellman's principle of optimality is valid. However, this definition results in a prohibitively large number of the states and the computation can hardly be carried out. The dissertation provides a recursive definition for the trajectory-adaptive routing policy, for which the information is not included in the state variable. In this way, the number of states is small, but Bellman's principle of optimality or non-dominance is invalid for a similar reason as in the optimal path problem. Again purity is introduced to the trajectory-adaptive routing policy and an exact algorithm is designed based on the concept of decreasing order of time.^

Investigation of excess sludge reduction by an anaerobic side-stream reactor (ASSR): The role of EPS and enzymes in sludge floc

Chon, Dong-Hyun — Mon, 16 Apr 2012 14:14:47 PDT

Over the last two decades, minimization of excess sludge generation within the activated sludge process has been studied. Among several net sludge reduction technologies, the anaerobic side-stream reactor (ASSR) process is of particular interest because it has shown significant sludge reduction without causing negative effects on operational performances. ^ This study focused on the verification of the ASSR process, the mechanisms of excess sludge reduction, and the development of a new process using high rate ASSR. The earlier part of this research found that a bench-scale ASSR with 10 day solids retention time (SRT) led to about 60% less sludge yield than conventional activated sludge, without causing negative effects on the main activated sludge process, i.e., sludge settling and effluent properties. This sludge yield result indicated that incorporation of an anaerobic side-stream reactor into activated sludge was a valid sludge reduction process and was much more effective than any other conventional methods (anaerobic digestion or aerobic digestion). New methods to estimate SRT and observed sludge yield for the ASSR process were also proposed during this stage of research. ^ The later part of this research investigated the interaction between ASSR and activated sludge and the role of extracellular polymeric substances (EPS) and enzymes in sludge flocs to reveal the mechanisms of excess sludge reduction in the ASSR process. It was observed that much of the organic matter, particularly the EPS, was solublized in the ASSR and readily degraded in the main activated sludge reactor as the previous study showed. By accounting for the mass of sludge in the reactors, it was determined that half of the sludge reduction occurred directly in the ASSR while the other half of the sludge was degraded in the aeration basin. From an intensive side-by-side reactor study, it was found that the amount of the released material from ASSR was not proportional to overall sludge reduction, indicating that the success of the ASSR process is not solely dependent on the extent of hydrolysis or anaerobic sludge degradation in the ASSR but on the recirculation of the whole sludge between aerobic conditions (activated sludge) and anaerobic conditions (ASSR). This sludge recirculation reduced the accumulation of excessive EPS fractions within the flocs, allowing for balanced EPS fractions even under extremely long SRT conditions, and thus resulting in effective flocculation and sludge settling. Overall, the ASSR process kept the sludge refreshed in spite of the extremely long SRT due to the extremely minimal sludge wasting. This concept is proposed in this research as Sludge Refreshment. ^ Preliminary research and examination of literature reviews during this doctoral research led us to develop a new hypothesis that deflocculation and subsequent sludge hydrolysis occur more effectively under the short period of anaerobic digestion and that recirculation of this sludge back to the aeration basin could lead to even more effective excess sludge reduction. To verify this hypothesis, an anaerobic batch study was conducted and various schemes of the ASSR process (different SRTs and temperatures) were operated side-by-side in the laboratory. The results from the anaerobic batch tests showed that maximum solubilization of key floc cations, extracellular polymeric substances, and enzyme activity occurred within 2 days of anaerobic digestion, regardless of temperature. The results from the reactor study showed that activated sludge with a 2.5-day-SRT ASSR, generated the lowest sludge yield among the studied systems. All these results indicate that an activated sludge process with a short-SRT (termed high rate) ASSR could result in greater solids reduction during wastewater treatment. ^ In summary, this research found that the ASSR process is valid for effective sludge reduction in biological wastewater treatment. The study of a novel high rate ASSR process also expanded insight into sludge flocs and allow a better understanding of the fate of EPS in aerobic and anaerobic repeating conditions. This process should be considered to be a very effective method for sludge reduction which also maintains good operational performance for the activated sludge process.^

Real-Time Information and Correlations for Optimal Routing in Stochastic Networks

Huang, He — Tue, 06 Mar 2012 10:02:18 PST

Congestion is a world-wide problem in transportation. One major reason is random interruptions. The traffic network is inherently stochastic, and strong dependencies exist among traffic quantities, e.g., travel time, traffic speed, link volume. Information in stochastic networks can help with adaptive routing in terms of minimizing expected travel time or disutility. Routing in such networks is different from that in deterministic networks or when stochastic dependencies are not taken into account. This dissertation addresses the optimal routing problems, including the optimal a priori path problem and the optimal adaptive routing problem with different information scenarios, in stochastic and time-dependent networks with explicit consideration of the correlations between link travel time random variables. There are a number of studies in the literature addressing the optimal routing problems, but most of them ignore the correlations between link travel times. The consideration of the correlations makes the problem studied in this dissertation difficult, both conceptually and computationally. The optimal path finding problem in such networks is different from that in stochastic and time-dependent networks with no consideration of the correlations. This dissertation firstly provides an empirical study of the correlations between random link travel times and also verifies the importance of the consideration of the spatial and temporal correlations in estimating trip travel time and its reliability. It then shows that Bellman's principle of optimality or non-dominance is not valid due to the time-dependency and the correlations. A new property termed purity is introduced and an exact label-correcting algorithm is designed to solve the problem. With the fast advance of telecommunication technologies, real-time traffic information will soon become an integral part of travelers' route choice decision making. The study of optimal adaptive routing problems is thus timely and of great value. This dissertation studies the problems with a wide variety of information scenarios, including delayed global information, real-time local information, pre-trip global information, no online information, and trajectory information. It is shown that, for the first four partial information scenarios, Bellman's principle of optimality does not hold. A heuristic algorithm is developed and employed based on a set of necessary conditions for optimality. The same algorithm is showed to be exact for the perfect online information scenario. For optimal adaptive routing problem with trajectory information, this dissertation proves that, if the routing policy is defined in a similar way to other four information scenarios, i.e., the trajectory information is included in the state variable, Bellman's principle of optimality is valid. However, this definition results in a prohibitively large number of the states and the computation can hardly be carried out. The dissertation provides a recursive definition for the trajectory-adaptive routing policy, for which the information is not included in the state variable. In this way, the number of states is small, but Bellman's principle of optimality or non-dominance is invalid for a similar reason as in the optimal path problem. Again purity is introduced to the trajectory-adaptive routing policy and an exact algorithm is designed based on the concept of decreasing order of time.

Structural Applications of Metal Foams Considering Material and Geometrical Uncertainty

Moradi, Mohammadreza — Fri, 09 Dec 2011 10:01:43 PST

Metal foam is a relatively new and potentially revolutionary material that allows for components to be replaced with elements capable of large energy dissipation, or components to be stiffened with elements which will generate significant supplementary energy dissipation when buckling occurs. Metal foams provide a means to explore reconfiguring steel structures to mitigate cross-section buckling in many cases and dramatically increase energy dissipation in all cases. The microstructure of metal foams consists of solid and void phases. These voids have random shape and size. Therefore, randomness ,which is introduced into metal foams during the manufacturing processes, creating more uncertainty in the behavior of metal foams compared to solid steel. Therefore, studying uncertainty in the performance metrics of structures which have metal foams is more crucial than for conventional structures. Therefore, in this study, structural application of metal foams considering material and geometrical uncertainty is presented. This study applies the Sobol' decomposition of a function of many random variables to different problem in structural mechanics. First, the Sobol' decomposition itself is reviewed and extended to cover the case in which the input random variables have Gaussian distribution. Then two examples are given for a polynomial function of 3 random variables and the collapse load of a two story frame. In the structural example, the Sobol' decomposition is used to decompose the variance of the response, the collapse load, into contributions from the individual input variables. This decomposition reveals the relative importance of the individual member yield stresses in determining the collapse load of the frame. In applying the Sobol' decomposition to this structural problem the following issues are addressed: calculation of the components of the Sobol' decomposition by Monte Carlo simulation; the effect of input distribution on the Sobol' decomposition; convergence of estimates of the Sobol' decomposition with sample size using various sampling schemes; the possibility of model reduction guided by the results of the Sobol' decomposition. For the rest of the study the different structural applications of metal foam is investigated. In the first application, it is shown that metal foams have the potential to serve as hysteric dampers in the braces of braced building frames. Using metal foams in the structural braces decreases different dynamic responses such as roof drift, base shear and maximum moment in the columns. Optimum metal foam strengths are different for different earthquakes. In order to use metal foam in the structural braces, metal foams need to have stable cyclic response which might be achievable for metal foams with high relative density. The second application is to improve strength and ductility of a steel tube by filling it with steel foam. Steel tube beams and columns are able to provide significant strength for structures. They have an efficient shape with large second moment of inertia which leads to light elements with high bending strength. Steel foams with high strength to weight ratio are used to fill the steel tube to improves its mechanical behavior. The linear eigenvalue and plastic collapse finite element (FE) analysis are performed on steel foam filled tube under pure compression and three point bending simulation. It is shown that foam improves the maximum strength and the ability of energy absorption of the steel tubes significantly. Different configurations with different volume of steel foam and composite behavior are investigated. It is demonstrated that there are some optimum configurations with more efficient behavior. If composite action between steel foam and steel increases, the strength of the element will improve due to the change of the failure mode from local buckling to yielding. Moreover, the Sobol' decomposition is used to investigate uncertainty in the strength and ductility of the composite tube, including the sensitivity of the strength to input parameters such as the foam density, tube wall thickness, steel properties etc. Monte Carlo simulation is performed on aluminum foam filled tubes under three point bending conditions. The simulation method is nonlinear finite element analysis. Results show that the steel foam properties have a greater effect on ductility of the steel foam filled tube than its strength. Moreover, flexural strength is more sensitive to steel properties than to aluminum foam properties. Finally, the properties of hypothetical structural steel foam C-channels foamed are investigated via simulations. In thin-walled structural members, stability of the walls is the primary driver of structural limit states. Moreover, having a light weight is one of the main advantages of the thin-walled structural members. Therefore, thin-walled structural members made of steel foam exhibit improved strength while maintaining their low weight. Linear eigenvalue, finite strip method (FSM) and plastic collapse FE analysis is used to evaluate the strength and ductility of steel foam C-channels under uniform compression and bending. It is found that replacing steel walls of the C-channel with steel foam walls increases the local buckling resistance and decreases the global buckling resistance of the C-channel. By using the Sobol' decomposition, an optimum configuration for the variable density steel foam C-channel can be found. For high relative density, replacing solid steel of the lips and flange elements with steel foam increases the buckling strength. On the other hand, for low relative density replacing solid steel of the lips and flange elements with steel foam deceases the buckling strength. Moreover, it is shown that buckling strength of the steel foam C-channel is sensitive to the second order Sobol' indices. In summary, it is shown in this research that the metal foams have a great potential to improve different types of structural responses, and there are many promising application for metal foam in civil structures.

Physical chemical and biological monitoring and analysis of four small New England watersheds during baseflow and stormflow conditions

Sadosky, Rebecca Baker — Wed, 19 Jan 2011 11:48:58 PST

As prolifically documented in the literature, wet weather events have a significant effect on the physical, chemical and biological properties of streams, thereby affecting the overall water quality of the stream as well as the receiving body of water. These effects are of particular importance when the receiving water body is a reservoir used as a source of drinking water in which a decrease in water quality could pose a significant risk to human health. Pathogens such as Cryptosporidium and Giardia are of particular importance to water supply authorities for their specific and direct threat to human health. Cryptosporidium and Giardia are known waterborne pathogens, whose effects on immunocompromised individuals can be life threatening. Because of the risk posed to human health by these pathogens, it is imperative to gain a solid understanding of the environmental factors affecting die-off and transport, and thus the ultimate concentrations in receiving waters. Testing for these pathogens is both expensive and time consuming. It is therefore also important to determine if other, more easily measured parameters can act as surrogates for these pathogens. ^ Documentation of outbreaks resulting from exposure to these resistant pathogens is plentiful and has in part been paralleled by the study described herein. However, this research was necessary owing to the reliance of Southern New England on surface water to supply drinking water to its population and has several focus points that have yet to be evaluated in the existing literature. Specific objectives of this research were to (1) identify and better understand factors affecting Cryptosporidium and Giardia concentrations entering the studied surface water supplies and; (2) develop a sampling protocol for future use by researchers and water utilities to most accurately determine nutrient and microbial concentrations entering a water supply. Factors evaluated included event rainfall, antecedent rainfall, streamflow, land use characteristics, and the validity of indicator organisms to predict the presence of Cryptosporidium and Giardia. The study sites for this research were four small streams in Massachusetts in watersheds with varying land use characteristics. This research focused on gaining a better understanding of the effects of rainfall on in-stream parameter concentrations for streams receiving water running off of areas with distinct land-uses. The effects of rainfall were investigated through field measurements and statistical analyses. The transport of Cryptosporidium and Giardia to receiving waters, as well as understanding the factors impacting their detection, were main focus areas of this research. ^ Study results suggest that the occurrence of Cryptosporidium and Giardia in the tributaries of small watersheds is not easily explained by basic hydrologic conditions, precipitation, land use, or the presence/absence of standard in-stream indicator organisms. Total event rainfall did not significantly affect the presence, absence or concentration of Cryptosporidium or Giardia. However, 72-hr antecedent rainfall totals greater than 20 mm were observed for all but one of the events where Cryptosporidium and/or Giardia were detected. Clostridium perfringens concentrations greater than 100 cfu/100mL was the only water quality parameter (both nutrient as well as microorganism) to provide an accurate indication for the potential presence of Cryptosporidium or Giardia. If present in the near stream area, even small amounts of precipitation when paired with wet antecedent conditions, were likely to result in transport and thus elevated in-stream concentrations of Cryptosporidium and Giardia. Concentrations were typically higher on the rising limb or near the peak of the storm hydrograph, suggesting that the nutrients and microorganisms evaluated were carried into the stream with the first flush. This flushing phenomenon was further evidenced by the clockwise hysteresis loops produced for all events that presented a single peak hydrograph. Cryptosporidium and Giardia were generally (6 out of 7 events) observed at higher concentrations at the downstream sampling location. Occurrence of Cryptosporidium and Giardia in surface waters appeared to be largely a factor of infectivity rates of wild and domesticated animals living within the watershed and their annual cycles. The animal population may have increased the probability of detecting Cryptosporidium or Giardia during the late winter and early spring. For watersheds where reservoirs are the major source of water withdrawals, sampling should be based on hydrodynamics of the reservoir and travel times from the tributaries to the intake. Attention should also be paid to antecedent rainfall conditions and time of year. This dissertation outlines the research objectives, reviews pertinent literature, describes the research design and methods as well as presents results and conclusions.^