Navid H. Jafari

Service Life of HDPE Geomembranes Subjected to Elevated Temperatures

Subtitle D landfills may experience elevated temperatures for a variety of reasons such as hydration of combustion ash, waste biodegradation with and without leachate recirculation, aluminum production waste and combustion ash reactions, and wastes received with elevated temperature. Elevated temperatures can reduce service life or effectiveness of high density polyethylene (HDPE) geomem- branes by accelerating antioxidant depletion of geomembranes and polymer degradation. A case history is presented to illustrate the potential effects of elevated temperatures and time-temperature history on a HDPE geomembrane and the associated reduction in service life or effectiveness. The geomembrane service life was influenced by the peak temperature, e.g., 60-80°C, the duration of peak temperatures (time-temperature history), and the time to complete antioxidant depletion. This paper also discusses possible criteria for assessing the service life of geomembranes, such as applicable engineering properties, locations for service life assessments, definitions of geomembrane service life, and measures that could be adopted if service life were reduced significantly. DOI: 10.1061/(ASCE)HZ.2153-5515.0000188.

The July 10 2000 Payatas Landfill Slope Failure

This paper presents an investigation of the slope failure in the Payatas landfill in Quezon City, Philippines. This failure, which killed at least 330 persons, occurred July 10th 2000 after two weeks of heavy rain from two typhoons. Slope stability analyses indicate that the raised leachate level, existence of landfill gas created by natural aerobic and anaerobic degradation, and a significantly over - steepened slope contributed to the slope failure. The Hydrologic Evaluation of Landfill Performance (HELP) model was used to predict the location of the leachate level in the waste at the time of the slope failure for analysis purposes. This paper presents a description of the geological and environmental conditions, identification of the critical failure surface, and slope stability analyses to better understand the failure and present recommendations for other landfills in tropical areas. In addition, this case history is used to evaluate uncertainty in parameters used in back-analysis of a landfill slope failure.

Soil compressibility in transient unsaturated seepage analyses

Most levee underseepage and uplift analyses are based on steady-state seepage and can yield conservative results. Although computations are simpler and steady-state seepage parameters are easier to determine and readily available, transient unsaturated seepage analyses are more representative of levee seepage conditions because boundary conditions acting on the levee or floodwall and saturation change with time, which induce pore-water pressure and seepage changes with time in the embankment and foundation strata. In addition, these boundary conditions, e.g., flood surge or storm event, are rapid such that steady-state conditions may not have time to develop in the embankment and some foundation materials. Transient seepage analyses using a floodwall case study indicate that as soil compressibility of the underseepage layer decreases, rapid landside pore-water pressures increase and can approach steady-state values. The transient results also indicate that uplift factors of safety during the flood event a...

Spatial and temporal characteristics of elevated temperatures in municipal solid waste landfills

Elevated temperatures in waste containment facilities can pose health, environmental, and safety risks because they generate toxic gases, pressures, leachate, and heat. In particular, MSW landfills undergo changes in behavior that typically follow a progression of indicators, e.g., elevated temperatures, changes in gas composition, elevated gas pressures, increased leachate migration, slope movement, and unusual and rapid surface settlement. This paper presents two MSW landfill case studies that show the spatial and time-lapse movements of these indicators and identify four zones that illustrate the transition of normal MSW decomposition to the region of elevated temperatures. The spatial zones are gas front, temperature front, and smoldering front. The gas wellhead temperature and the ratio of CH4 to CO2 are used to delineate the boundaries between normal MSW decomposition, gas front, and temperature front. The ratio of CH4 to CO2 and carbon monoxide concentrations along with settlement strain rates and subsurface temperatures are used to delineate the smoldering front. In addition, downhole temperatures can be used to estimate the rate of movement of elevated temperatures, which is important for isolating and containing the elevated temperature in a timely manner.

Compound hazards yield Louisiana flood

On 11 August 2016, a severe weather system dropped 433 mm of rain in about 72 hours, triggering widespread flooding in southern Louisiana. This flood damaged at least 60,000 homes, required evacuation of more than 20,000 people, and led to 13 deaths ([ 1 ][1]). At one point, the Amite river crest

Ruling on IHNC Floodwall Failures during Hurricane Katrina

On 29 August 2005, Hurricane Katrina came ashore just east of New Orleans with sustained winds exceeding 212 km=h (125 mph), significant rainfall and storm surge, and widespread flooding. The ruling in Armstrong, C.A. No. 10-866 on 12 April 2013 by Federal Judge Stanwood R. Duval, Jr. against property owners in the Lower Ninth Ward that were inundated by two breaches of the floodwall along the Inner Harbor Navigation Canal (IHNC) essentially ended litigation against the United States of America. This paper discusses events leading up to and during Hurricane Katrina, IHNC floodwall performance, negligence claim brought by Lower Ninth Ward property owners against the United States and Washington Group, International (WGI), and the United States’s defense to the negligence claim with emphasis on the “cause in fact” prong. Recommendations for clarifying the causation issue are presented to help focus the trying and defense of future levee and floodwall negligence claims. On 12 April 2013, United States District Court Judge Stanwood R. Duval, Jr. (Duval 2013) ruled in favor of the United States of America and the Washington Group International (WGI) in a class-action case brought by six named Lower Ninth Ward property owners (Kenneth and Jeannine Armstrong, Fred Holmes, the Succession of Ethel Coats, Alvin Livers, and Clifford Washington) whose properties were rapidly and catastrophically inundated by two floodwall failures during Hurricane Katrina on 29 August 2005. The Court conducted a 15-day bench trial over 3 weeks to determine whether the United States and WGI were negligent before Hurricane Katrina in their environmental restoration activities in the Inner Harbor Navigational Canal (IHNC) that parallels the subject floodwall and Lower Ninth Ward. This paper discusses the events leading up to and during Hurricane Katrina, the negligence claim brought by property owners, the plaintiffs’ problems proving “cause in fact,” and why the defendants did not prove the cause of the two floodwall failures but only that the United States and WGI activities were not a substantial factor in either floodwall failure. Because of the many variables and uncertainties surrounding the two floodwall failures (e.g., soil compressibility, floodwall height and alignment; storm surge height and duration; wave heights in the IHNC; duration and height of floodwall overtopping; depth of landside scour and erosion; sheet pile tensile properties, repairs, interlocking, and performance; wind speeds; timing of floodwall failures), proving the exact cause of both floodwall failures with certainty was difficult, if not impossible. In fact, Judge Duval states in his 12 April 2013 ruling:

Unsaturated and Transient Seepage Analysis of San Luis Dam

AbstractThis paper uses the San Luis Dam upstream slide to evaluate the pore-water pressures at failure and progression of the phreatic surface through the fine-grained core for drawdown stability analyses. The hydraulic conductivity and compressibility parameters of saturated and unsaturated soils are calibrated using the reservoir hydrograph and 13 piezometers in order to evaluate the pore-water pressures at failure. The analyses show unsaturated and transient seepage analyses can be used to estimate pore-water pressures during drawdown for various stability analyses and evaluate the progression of the phreatic surface through the fine-grained core. The transient results also indicate the van Genuchten parameter α significantly influences unsaturated soil response during drawdown. Different meshing techniques can produce consistent moisture content profiles in two different seepage software packages, but in situ measurement of moisture content and suction pressure is recommended to develop an unsaturate...

Progression of elevated temperatures in municipal solid waste landfills

AbstractElevated temperatures in municipal solid waste landfills can pose health, environmental, and safety risks because they can generate excessive gases, liquids, pressures, and heat that can da...

Classification and Reactivity of Secondary Aluminum Production Waste

AbstractAluminum production wastes (APW) are produced during the recycling of aluminum scrap and dross. They are frequently disposed in dry form at Subtitle D nonhazardous waste landfills, where they may react adversely with liquids. Depending on the APW composition and landfill environment, the exothermic reaction can cause sustained temperature increases that inhibit normal anaerobic biodegradation. A constant pressure calorimeter test was developed to simulate the APW reaction in a basic environment and quantify the reactivity. APW reactivity was investigated under varying strengths of sodium hydroxide and particle size. Bench-scale calorimeter experiments show that concentrations greater than 4M NaOH oxidize metallic aluminum and increase temperatures rapidly to 100°C. Lower NaOH concentrations, such as 1M NaOH, are recommended to quantify the APW reaction in a constant pressure calorimeter. APW in neutral solutions was found to be stable, but reducing APW particles through ball-milling exacerbated re...

Landfill operational techniques in the presence of elevated temperatures

Elevated temperatures in municipal solid waste landfills can produce obnoxious odors, toxic gases, and aggressive leachates, as well as damage gas extraction, leachate collection, interim cover, and composite liner systems. They also can result in expensive remedial measures and warrant permanent closure of the facility. Several factors can lead to elevated landfill temperatures, including air ingress, partially extinguished surface fires, reactive wastes, and spontaneous oxidation. Landfills typically experience changes to gas composition and flow, leachate chemistry and volume generation, and surface movement. Based on observed management, operation, and maintenance of elevated temperature facilities, various operational techniques are proposed for isolating and containing the elevated temperatures in a landfill.