Minimizing the Costs Associated with Implementing TMDL Allocations
Abstract:How TMDL allocations are structured can have a large impact on the total cost for water pollution control and on who pays what share of this cost. Development of more costeffective TMDLs on a watershed basis creates opportunities to reduce the overall cost, maximize the effectiveness of pollution control, and shift pollution control responsibilities from high cost to comparatively low cost controls. However, ad hoc allocation procedures, such as equalization of effluent concentrations, do not address cost, effectiveness or implementation schedule, and the complexity of real watersheds also rules out the use of most ad hoc allocation procedures. Cost, effectiveness, and implementation metrics must be formalized in a model capable of predicting and optimizing the performance of the whole system. An added benefit of this systematic approach is that it also allows the "fairness" of the allocation procedure to be addressed. The initial development of an Economic Allocation Model was described in an earlier paper presented at the TMDL 2005 conference. Since 2005, the Economic Allocation Model has been updated to consider non-point sources. The model was developed using data for an urban industrialized watershed in Los Angeles. It is based on a material balance around the entire watershed and includes both spatial and temporal effects. The cost, effectiveness, and implementation schedule for control technologies and BMP strategies for each source are input data to the model. The optimization procedure is flexible and allows the objective function and constraints to be easily modified. Various allocation procedures, such as equalization of effluent concentrations or waste loads, are built into the model for comparison. The model has been used to compare the cost impact of a variety of ad hoc allocation procedures for reducing the metals loading in an urban, industrialized watershed. The overall cost and the distribution of costs among sources was found to be quite variable. Results of this analysis have been used to quantify the benefits of watershed-wide waterquality trading for reducing the overall cost of metals control.
Document Type: Research Article
Publication date: 2007-10-01
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