American Society of Civil Engineers (ASCE)-Environmental and Water Resources Institute’s (EWRI) Total Maximum Daily Load (TMDL) Analysis and Modeling Task Committee is releasing a new Manual of Practice (MOP) No. 150 on TMDL Development and Implementation: Models, Methods, and Resources in February/March 2022. The MOP was written by members of the Task Committee, edited by four of them (Harry X. Zhang, Nigel W.T. Quinn, Deva K. Borah, and G. Padmanabhan), and peer reviewed by a Blue Ribbon Panel with nationally recognized expertise. The end result is a comprehensive and state-of-the art manual that provides essential information on developing and planning implementation of TMDLs. The MOP contains detailed descriptions of the models, analytical tools, and resources available to develop a TMDL and its implementation plan together with guidance on state-of-the-practice and appropriate uses of the models, analytical tools, and resources.

Specifically, the MOP includes a brief history of the TMDL program and overall TMDL process. It summarizes watershed and receiving water models, integration or linking of those models for complex waterbody systems, and simple analytical and empirical procedures/methods and models, including models for seasonal variations (continuous) and critical conditions (extreme events). The MOP also discusses model data sources and processing tools, including remote sensing; calibration, validation, and performance quantifications of the models; and model uncertainty analysis and margin of safety quantifications for TMDL development.

The MOP describes an online database system of USEPA-approved TMDL reports, and a new online search tool to search those reports for various topics. A model selection protocol for TMDLs, that identifies the principal steps involved in modeling for TMDL development and implementation planning, is included along with an implementation planning case study example. The example was chosen to exemplify current analysis and modeling practices in TMDL implementation planning.

The MOP is expected to serve as useful resources to engineering practitioners involved in the development and implementation of TMDLs. It will also serve the regulators, educators, students, and the public well. The MOP will be available from ASCE for purchase in February or March 2022. For more information, one may contact the author. An overview of the Manual of Practice will be presented at the conference.