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Illicit Discharge Detection and Elimination (IDDE)

The goal of IDDE is to improve water quality by identifying and eliminating contaminated, non-stormwater discharges entering stormwater drainage systems and ultimately discharging to surface waters.

One of the first IDDE projects Stone conducted was for the Town of Milton in 2005. Milton had recently been designated as an MS4 operator by VTDEC under EPA’s Phase II rules, and was required to develop an IDDE program plan. After assessing the extent and condition of the Town’s stormwater infrastructure, researching innovative and cost-effective water monitoring techniques, and considering staff availability and facilities, Stone drafted an IDDE program plan that promoted Milton’s interest in improving water quality without overcommitting the Town to prescriptive conditions. This plan was endorsed by VTDEC. Stone also drafted a related town ordinance prohibiting certain non-stormwater discharges to Milton’s stormwater system, satisfying a second requirement under the Phase II rules.

Stone has the necessary expertise, resources, and commitment to locate and characterize contaminant sources and initiate correction of bacterial, nutrient, and hazardous material discharges.

Since 2005, Stone Environmental and its partners have conducted IDDE surveys in over 65 Vermont communities. In total, Stone has assessed over 2,200 discharge points. A sanitary wastewater or washwater source was indicated at approximately 70 discharge points. Other types of contamination included petroleum (15 locations), treated drinking water (22 locations), industrial discharges (5), and road salt.

By combining drainage mapping, environmental investigative work, and municipal cooperation, Stone has decreased phosphorus loading to Vermont’s rivers and lakes and reduced the risk of pathogen exposure. A variety of other problems identified through these efforts have also been addressed: pet waste and trash dumping, truck washing runoff, mop water discharges via floor drains and catchbasins, and elimination of several small industrial discharges. In 2013 alone, Stone resolved approximately 20 illicit discharges. In the course of these IDDE projects, Stone has developed and refined the methods now preferred by VTDEC.