A finite-element model was developed to evaluate mechanisms contributing to positive pore pressures measured with sealed pressure transducers in the geological buffer beneath the Environmental Management Waste Management Facility (EMWMF), a composite-lined mixed waste disposal facility operated by the US Department of Energy. The geological buffer is a 3-m-thick engineered fine-textured layer directly beneath the EMWMF’s composite liner, and above the groundwater table. The model accounts for changes in pore water pressure resulting from (i) moistening of the geological buffer due to equilibration with the underlying geological materials, (ii) loading imposed by waste placed on the overlying liner, and (iii) fluctuations in the elevation of the underlying groundwater table. Pore water pressures predicted by the model are in good agreement with pore water pressures measured in the field. The predictions confirm that positive pore water pressures recorded by the sealed pressure transducers in the geological buffer are excess pore water pressures induced by the vertical normal stress imposed by waste placed on the liner, and are not due to a rise in the groundwater table. Simulations also showed that two additional years of filling would further increase the pore water pressure without any change in elevation of the groundwater table. The geological buffer remained unsaturated during the simulation, with a Bw-coefficient similar to that computed from the field-measured pore water pressures and waste filling records. Larger increases in pore water pressure were observed when the geological buffer was assumed to have higher initial saturation, as was observed in the field data. Incorporating seasonal fluctuations in the groundwater table beneath the geological buffer in the model resulted in predictions of small seasonal oscillation in the pore water pressure predicted at the measurement location, similar to seasonal oscillations observed in the field. Predictions made with the model indicate that the dissipation of the excess pore water pressures will occur over decades due to the low hydraulic conductivity of the geological buffer material.
Modern regulated landfills are designed to protect the environment by containing and isolating municipal solid waste (MSW) from the environment. Instead of treating MSW as a hazard to be contained, next generation landfills, here termed Sustainable Energy Reactor Facilities (SERFs) are envisioned to be designed and operated with a main focus on energy generation (through anaerobic biodegradation processes) and sustainability. Towards this vision, a coupled hydraulic-biochemical-mechanical model that is based on the HBM model, is implemented in large laboratory-scale and field-scale studies to simulate the degradation process of MSW. The model captures the consumption of biodegradable organic fraction in the waste by microorganisms, eventually leading to biogas generation and changing solid waste and leachate characteristics. The model was first tested against 0.04 m3 laboratory experiments to assess its ability to predict the observed behavior and derive values for the various model parameters. Subsequently, the model is implemented on a 37m3 field lysimeter at Deer Track Park Landfill. The presented data indicates that the model has the capacity to be implemented in field scale and generate geospatially variable estimates of methane (i.e., energy) yield.
Various techniques can be considered for the remediation of contaminated sediments. The options can include capping, dredging, or physical, biological, and/or chemical treatments and natural recovery. Natural recovery could be beneficial over dredging due to a reduction in costs and lack of solid disposal requirements. Source control, however, is a major issue for sustainable remediation. In a case study, surface and core sediment samples were collected from a harbor on the north bank of the St. Lawrence River in the province of Quebec to assess heavy metal pollution and determine if natural recovery was occurring. Comparing the results of all analysis done for sediment for three different years (2015, 2017 and 2019) in the sampling area, it can be seen that some metals increased, some decreased and some of them showed nearly the same level of contamination. The results also indicated that during the sampling periods, copper, zinc and chromium were the main elements that exceeded the occasional effect level based on the Environment Canada sediment quality guidelines. Therefore, metal pollution has become a noticeable problem in this area and natural recovery was not achieved for several metals due to ongoing contamination and thus source control is critical.