A Simplified and Focused Approach to Meeting Regulatory Requirements and Guiding an Effective Stormwater Program
Under their NPDES permits, municipalities are required to implement effective actions and demonstrate the continued effectiveness of their stormwater programs at reducing pollutant loads to the receiving waters. However, no standardized methodology nor consistent guidance exists to assist them in demonstrating compliance in a meaningful manner. A feasible process to generate useful information that both informs decisions as well as meets short and long-term regulatory requirements is highly desired. Building upon the process and supporting programs developed for Lake Tahoe and the Central Coast, our team has taken a simplified and focused approach to estimate pollutant load reduction benefits and apply Rapid Assessment Methods (RAMs) to verify and track the effectiveness of the load reduction actions. We have also clearly defined the role and value of water quality monitoring of the receiving waters to evaluate the long term response as a result of the cumulative program-related actions.
We apply a set of guiding principles to build a general process and supporting tools to assist municipalities to prioritize water quality improvements, estimate expected benefits and meet annual permit requirements. By directly collaborating with the regulators and the municipalities during development, the process and supporting tools are feasible, informative, relatively easy to use, and meet the intended objectives of the NPDES permit requirements.
In this presentation we will review:
(1) critical strategies to delineate an MS4 into unit planning catchments and generate necessary attributes to estimate pollutant load reductions associated with our program actions;
(2) a streamlined and focused approach to quantify pollutant load reductions using customized models;
(3) the use of the load reduction results to iteratively prioritize catchments and/or land uses for improvements and track program load reduction progress;
(4) the use of Rapid Assessment Method (RAMs) to assess BMP effectiveness, identify maintenance priorities, and meet annual regulatory monitoring requirements; and
(5) a cost effective and feasible water quality monitoring programs to evaluate stormwater program effectiveness.
The fundamental components of our approach leverage the required Phase II MS4 permit requirement to map MS4 stormwater infrastructure into a discrete collection of catchments and associated critical attributes. The maps are informative and can guide planning for years to come. Each catchment attribute is a critical input to a simplified, yet technically robust, urban hydrology model. The model and its supporting data management system generate and compare expected average annual volume and pollutant loading to the receiving waters. The model architecture is intentionally focused on estimating the benefits of water quality improvement actions in a manner that is informed by available data and/or directly testable by additional data collection. All models are inaccurate, so we focus the sensitivity of the model on the relative effectiveness of water quality improvement actions as implemented under the stormwater program.
The integration is a well thought out complete process and supporting toolkit for stormwater managers to identify priority locations for cost effective improvements, demonstrate effective actions and track water quality benefits of the entire MS4 program. We believe this approach is flexible enough to apply to a wide range of municipalities in a way that addresses the unique financial, geographic and political goals of their programs.
The audience will be invited to share their challenges in leveraging regulatory requirements to inform their program decisions for each step. We will then brainstorm ideas on how components of their stormwater program can be applied within this methodology.