Stormwater methods and trends for “first flush” treatment in Georgia

With the NPDES Phase II Final Rule taking effect, more municipalities are confronted with the requirement to develop, implement, and enforce a management plan to control post-construction stormwater runoff. The ultimate objective is to reduce pollutant loads and improve water quality. To accomplish this goal, many municipalities have adopted regulations that require all new and redeveloped areas to treat the “first flush” (first 1.2”) of rainfall prior to discharge. The engineer/developer must design a system that accomplishes this goal. Plans must then be approved by the local governing authority. The most common “first flush” treatment method to control post-construction stormwater (within the Metropolitan North Georgia Water Planning District) is Extended Dry Detention Ponds (EDDP). This paper will discuss the use of the EDDP as post-construction stormwater treatment and how it is being applied to new and re-development projects. In addition, the paper will address how the common practice of installing the EDDP online has negative, long term consequences that are only now becoming apparent.