CTI and Associates Inc.

Pontiac, MI, United States

CTI and Associates Inc.

Pontiac, MI, United States
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Foye K.,CTI and Associates Inc. | Soong T.-Y.,CTI and Associates Inc.
Geotechnical Special Publication | Year: 2017

Past estimates of geomembrane longevity have typically focused on the degradation of the polymer tensile properties with time, demonstrating that these materials exceed expectations for typical municipal solid waste (MSW) facilities. However, interest in the performance of geomembranes for the disposal of low-level (LLW) and intermediate-level (ILW) radioactive waste landfills poses additional challenges. Many of these facilities use probabilistic models of long-term performance in terms of contaminant transport and exposure to make design decisions. However, current models have relatively little information quantifying the potential for leakage through the geomembrane that directly consider the change in material properties with time. Studies of the various mechanical modes of deformation and rupture for polyethylene sheet allow for this quantification. An example of this approach illustrates how the consideration of crack development in final cover geomembranes can be adapted for use in simulations of long-term landfill system performance suitable for LLW/ILW facility performance assessments. © ASCE.


Zhao X.,CTI and Associates Inc. | Te-Soong Y.,CTI and Associates Inc. | Subbarayan M.,CTI and Associates Inc. | Williams M.,County of St. Clair
Journal of Hazardous, Toxic, and Radioactive Waste | Year: 2013

A septage bioreactor landfill was constructed and operated at a publicly owned landfill in the U.S. state of Michigan. Residential septage was processed onsite and injected into municipal solid waste (MSW) using subsurface injection lines (for supernatant) and surface infiltration pits (for sludge) to accelerate the solid waste-decomposition process. For comparison, a leachate bioreactor landfill was also constructed and operated onsite. By comparing the systemperformance from both bioreactors, the impact of septage addition was identified. Extensive datasets consisting of parameters such as waste temperature, waste-moisture content, leachate quality, landfill gas generation, and waste settlement were systematically evaluated. The waste temperature in both bioreactors was in accordance with a similar trend. Using leachate addition, the waste-moisture content in the leachate bioreactor was controlled to maintain similar moisture content as the septage bioreactor. Using a first-order decay model, the gas-generation rate coefficients (first-order decay coefficient) were estimated at 0.296 and 0.082 year-1 for the septage bioreactor and leachate bioreactor landfills, respectively. This project demonstrated that wastedecomposition rate can be accelerated by septage addition and septage can be processed and treated in the septage bioreactor safely and effectively . . © 2013 American Society of Civil Engineers.


Maraqa M.A.,United Arab Emirates University | Zhao X.,CTI and Associates Inc. | Lee J.-U.,United Arab Emirates University | Allan F.,United Arab Emirates University | Voice T.C.,Michigan State University
Journal of Contaminant Hydrology | Year: 2011

Sorption of dimethyl phthalate (DMP), diethyl phthalate (DEP) and dipropyl phthalate (DPP) to two soil materials that vary in organic matter content was investigated using miscible displacement experiments under saturated flow conditions. Generated breakthrough curves (BTCs) were inversely simulated using linear, equilibrium sorption (LE), nonlinear, equilibrium sorption (NL), linear, first-order nonequilibrium sorption (LFO), linear, radial diffusion (LRD), and nonlinear, first-order nonequilibrium sorption (NFO) models. The Akaike information criterion was utilized to determine the preferred model. The LE model could not adequately describe phthalate ester (PE) BTCs in higher organic matter soil or for more hydrophobic PEs. The LFO and LRD models adequately described the BTCs but a slight improvement in curve-fitting was gained in some cases when the NFO model was used. However, none of the models could properly describe the desorptive tail of DPP for the high organic matter soil. Transport of DPP through this soil was adequately predicted when degradation or sorption hysteresis was considered. Using the optimized parameter values along with values reported by others it was shown that the organic carbon distribution coefficient (K oc) of PEs correlates well with the octanol/water partition coefficient (K ow). Also, a strong relationship was found between the first-order sorption rate coefficient normalized to injection pulse size and compound residence time. A similar trend of timescale dependence was found for the rate parameter in the radial diffusion model. Results also revealed that the fraction of instantaneous sorption sites is dependent on K ow and appears to decrease with the increase in the sorption rate parameter. © 2011 Elsevier B.V. All rights reserved.


Foye K.C.,CTI and Associates Inc. | Rajan R.,CTI and Associates Inc. | Kabalan M.,CTI and Associates Inc. | Soong T.-Y.,CTI and Associates Inc.
Geotechnical Special Publication | Year: 2014

Final covers for landfills containing radioactive waste, municipal solid waste, and other materials with highly variable properties are expected to perform for decades, centuries, or longer. Forthcoming regulations governing these facilities and concerns about long-term maintenance costs are demanding construction techniques that minimize long-term interventions to guarantee this performance. A primary problem maintaining final cover performance is differential settlement. Localized depressions resulting from differential settlement can compromise the drainage performance of a final cover, its primary function. Geosynthetic reinforcement can reduce the effects of differential settlement, but a reliable method is needed to quantify the reinforcement required and to index this requirement to measures of risk. For example, such a method would construct a list of reinforcement options and calculate the expected value of life cycle maintenance costs (risk) for each option using the resulting distribution of failed zones requiring repair. This paper presents a probabilistic analysis method to model reinforced final cover performance. The method draws from previous studies of road subgrade and sinkhole bridging reinforcement to allow the modeling of reinforcement effects on differential settlement performance. Example results are presented to show how the method can be used to proportion final cover design. © 2014 American Society of Civil Engineers.


Foye K.,CTI and Associates Inc.
International Journal of Environmental Research and Public Health | Year: 2011

Geomembranes are an important component of modern engineered barriers to prevent the infiltration of stormwater and runoff into contaminated soil and rock as well as waste containment facilities-a function generally described as a geomembrane cover. This paper presents a case history involving a novel implementation of a geomembrane cover system. Due to this novelty, the design engineers needed to assemble from disparate sources the design criteria for the engineering of the cover. This paper discusses the design methodologies assembled by the engineering team. This information will aid engineers designing similar cover systems as well as environmental and public health professionals selecting site improvements that involve infiltration barriers. © 2011 by the authors; licensee MDPI, Basel, Switzerland.


Dickson J.R.,CTI and Associates Inc.
Remediation | Year: 2016

Following costly repairs of a coastal landfill's shoreline protection system (SPS) within a tidal zone with additional future repairs imminent, a green and sustainable remedy optimization to eliminate the root cause of the damage was evaluated. The removal of the armored point located just north of the landfill that had been a major source of erosion to the SPS during storm events was proposed and implemented. The restoration of the beach to protect the landfill and restore natural longshore processes, while providing habitat for wildlife, was a key goal of the project. As a part of the work, the removal of a creosote-impregnated boat ramp was incorporated into the final design at the request of stakeholders. During the process, all materials excavated from the site were either beneficially reused in the construction or reused off-site as concrete, clean fill, or fuel. The work was implemented in the dry by working with the tides and successfully achieved the project goals. Based on the initial inspections following the repairs, no additional repairs are anticipated well into the future. © 2016 Wiley Periodicals, Inc. ©2016 Wiley Periodicals, Inc.


Hettiarachchi V.C.,CTI and Associates Inc. | Foye K.C.,CTI and Associates Inc. | Zhao X.,CTI and Associates Inc.
Geotechnical Special Publication | Year: 2012

Landfill operators depend on the available volume for waste placement, airspace, as their primary source of revenue. The ability to measure waste settlement and the corresponding increase in airspace is key to maximizing revenue, projecting cash flow, and conserving land area. Wet landfilling technology increases the rate of biological waste decomposition, accelerating settlement and increasing available airspace. In this paper, settlement data from a full-scale experimental wet landfill cell are presented. The experimental landfill cell is a 2.8-hectare cell in Smiths Creek, Michigan. Several pipes were installed and settlement profilers were used to measure the settlement within several discrete waste lifts. The paper examines this data to quantify the magnitude of waste settlement observed in the wet landfill cell. © 2012 American Society of Civil Engineers.


Foye K.C.,CTI and Associates Inc.
Advances in Civil Engineering | Year: 2011

The use of Reclaimed Asphalt Pavement (RAP) in lieu of virgin crushed stone aggregate is becoming a widely accepted practice for a number of construction applications, particularly pavement base courses. A number of laboratory RAP studies have considered the mechanical properties of RAP bases in order to support pavement designs incorporating RAP. These studies have revealed a number of interesting relationships between RAP moisture content, compaction, and stiffness. This paper discusses the experiences of a design-build contractor integrating a geosynthetic ground improvement program with a RAP base during the reconstruction of a 1.95ha asphalt parking lot. Field observations of base course construction with RAP explore some of the implications of laboratory findings. A number of interesting observations on the technical, construction, and economic issues resulting from the project challenges and the use of RAP are presented. Copyright © 2011 Kevin C. Foye.


Foye K.C.,CTI and Associates Inc. | Soong T.-Y.,CTI and Associates Inc.
Geotechnical Special Publication | Year: 2010

The long-term functionality of composite landfill final cover systems and composite floor liner systems depends on the distortions imposed on these systems by differential settlement. The evaluation of differential settlement is particularly challenging for final cover systems, because of the heterogeneity of waste, and for floor liners over highly variable subgrades (e.g. existing waste, mine spoil, etc.). The present ability to forecast these distortions is limited by a scarcity of long-term settlement measurements at modern landfills and difficulty characterizing waste and subgrade properties. Furthermore, deterministic approaches to landfill settlement prediction are not able to capture the spatial variability in the waste mass and subgrade properties which control this behavior. This paper considers a probabilistic approach to the long-term estimates of differential settlement beneath landfill final cover and floor liner systems using random fields to model the waste and subgrade properties. Finite element analysis of two dimensional random fields is used to calibrate appropriate spatial correlation parameters for use in simpler, one-dimensional analyses to estimate differential settlement. © 2010 ASCE.


Foye K.C.,CTI and Associates Inc. | Zhao X.,CTI and Associates Inc.
Geotechnical Special Publication | Year: 2011

The long-term functionality of composite landfill final cover systems and composite floor liner systems depends on the distortions imposed on these systems by differential settlement. The evaluation of differential settlement is particularly challenging for final cover systems, because of the heterogeneity of waste, and for floor liners over highly variable subgrades (e.g. existing waste, mine spoil, etc.). Deterministic approaches to landfill settlement prediction are not able to capture the spatial variability in the waste mass and subgrade properties which control differential settlement. An alternative, probabilistic solution is to use random fields to model the waste and subgrade properties. This paper discusses the application of a random field model to the design of landfill final cover and floor liner systems. The paper suggests an approach to select acceptable probabilistic criteria for design. © 2011 ASCE.

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