A BETTER WAY TO CONDUCT TMDLS ON A SHOESTRING BUDGET
There are over 30 states in which TMDL development is driven by court-order schedules. In many of these states, as well as ones without court-orders, a vast number of TMDLs are being developed in a relatively short amount of time. Given these accelerated schedules and limited budgets,
it is imperative that an optimized strategy be employed to ensure that the implementation plan will achieve the intended goal in a fair and equitable manner. There exist defensible and straightforward steps that can be taken to understand the system under study and consequently aid in a more
accurate and encompassing TMDL. The objective of this paper is to present a three-step method that would be implemented before the onset of any water quality modeling or load allocation to aid in the accurate development of a TMDL. This first step of this method includes approaches for quantifying
loads at complex sites, including methods for estimating loads attributable to sources that are less straightforward to quantify. Approaches for quantifying non-point source pollution in surface water runoff without the development of a ‘high-level’ watershed model are discussed.
In addition, relatively simple calculations of sediment erosion, diffusion from sediment pore water, and flux from groundwater, which are most relevant for analysis of toxics and metals, are also presented. After load quantification, a mass balance for the system is attempted to ensure that
all loads are accounted and there are no important ‘missing’ sources that could hamper any eventual remediation. Finally, in the third step, a conceptual model of the system is ‘sketched’. This conceptual model is then used to support TMDL development, including any
model application, load allocation, and investigation into implementation strategies. A case study in Texas is highlighted to show the strengths of this three-step method in overall environmental analysis.
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