UBC Theses and Dissertations
Groundwater contamination from waste-management sites : the interaction between risk-based engineering design and regulatory policy Massmann, Joel Warren
This dissertation puts in place a risk-cost-benefit analysis for waste management facilities that explicitly recognizes the adversarial relationship that exists in a regulated market economy between the owner-operator of the facility and the government regulatory agency under whose terms the facility must be licensed. The risk-cost-benefit analysis is set up from the perspective of the owner-operator. It can be used directly by the owner-operator to assess alternative design strategies. It can also be used by the regulatory agency to assess alternative regulatory policies, but only in an indirect manner, by examining the response of an owner-operator to the stimuli of various policies. The objective function is written in terms of a discounted stream of benefits, costs, and risks over an engineering time horizon. Benefits are in terms of revenues for services provided; costs are those of construction and operation of the facility. Risk is defined as the expected cost associated with failure, with failure defined as a groundwater contamination event that violates the licensing requirements set forth by the regulatory agency. Failure requires a breach of the containment structure and contaminant migration through the hydrogeological environment to a compliance surface. Reliability theory is used to estimate the probability of breaching and Monte Carlo finite-element simulations are used to simulate advective contaminant transport. The hydraulic conductivity values in the hydrogeological environment are defined stochastically. The probability of failure is reduced by the presence of a monitoring network established by the owner-operator. The level of reduction in the probability of failure can be calculated from the stochastic contaminant transport simulations. While the framework is quite general, the development in this dissertation is specifically suited for a landfill in which the primary design feature is one or more synthetic liners and in which contamination is brought about by the release of a single, nonreactive species in an advective, steady-state, horizontal flow field. The risk cost benefit analysis is applied to 1) an assessment of the relative worth of alternative containment-construction activities, site-investigation activities, and monitoring activities available to the owner-operator, 2) an assessment of alternative policy options available to the regulatory agency, and 3) two case histories. Sensitivity analyses designed to address the first issue show that the allocation of resources by the owner-operator is sensitive to the stochastic parameters that describe the hydraulic conductivity field at a site. For the cases analyzed, the installation of a dense monitoring network is of less value to the owner-operator than a more conservative containment design. Sensitivity analyses designed to address the second issue suggest that from a regulatory perspective, design standards should be more effective than performance standards in reducing risk, and design specifications on the containment structure should be more effective than those on the monitoring network. Performance bonds posted before construction have a greater potential to influence design than prospective penalties to be imposed at the time of failure. Sitting on low-conductivity deposits is a more effective method of risk reduction than any form of regulatory influence. Results of the case histories indicate that the methodology can be successfully applied at field sites, and that the risks associated with groundwater contamination may be small when compared to the owner-operators' benefits and costs.
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