As current development trends continue to focus on green infrastructure and low-impact development, many storm water regulations are changing to comply with these trends. State and local agencies are setting new rules that require the water quality storm event to remain on site by infiltration, evapotranspiration or reuse to the maximum extent practical (MEP). To fulfill this requirement, one must have a clear understanding of what constitutes MEP. This poses a problem, as there is not a consistent definition of MEP.
The definition of MEP is generally left up to interpretation by the designer and the reviewer of each development project. This can result in different definitions and standards for individual projects.
The original intent of MEP was to allow flexibility, but current regulations do not provide a fair and consistent set of rules. This can result in problems when trying to comply with the requirements.
Leaving the regulations up to interpretation can be costly, and each individual site can have constraints such as building size, high groundwater or poor soils. It would be simpler and more cost effective for developers to adhere to these regulations if measurable goals were established. Creating a fair regulation that ensures water quality and meets the growing trend toward green infrastructure should be the goal of the regulations.
We need measurable standards and a process that clearly defines how to meet these standards. The rules need to explain how it would be feasible to keep water on site. For example, poor soils, hot soils, high groundwater and multiple other site-specific challenges preclude the use of infiltration practices. The rules need to address the level of treatment required if infiltration is proven infeasible.
If your site is not suitable for retaining the water quality volume on site and all options have been exhausted, it should not necessarily mean you should not build on that site. In fact, it still might be an ideal site to develop and there should be options to make that possible without compromising water quality.
I support the green infrastructure movement and retaining the onsite water quality volume to the maximum extent practicable, as long as measurable goals are established and options are clearly defined.
