Illicit Discharge Detection & Elimination (IDDE)

What is an Illicit Discharge?

An illicit discharge is the discharge of pollutants or non-stormwater materials to the stormwater drainage system. The result is untreated discharges that contribute high levels of pollutants, including bacteria, heavy metals, toxins, oils and grease, solvents, and nutrients to receiving bodies, like the Charles River. In fact, the segment of Watertown is classified by the EPA as impaired for a wide range of pollutants, some of which come from illicit discharges from surrounding communities.

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Is Stormwater Treated at a Treatment Plant?

No! The stormwater system is often confused with the sanitary sewer system. In Watertown, these are two completely separate systems. Flows to the sanitary sewer system (e.g., flushing toilets, shower drains, kitchen sink drains, etc.) are treated at Deer Island. Flows to the stormwater system (through catch basins and storm inlets) go directly to Charles River.

Where Do Illicit Discharges Come From?

Some illicit discharges are the direct result of human activity - someone dumping dog waste, oil or leaves down a catch basin. Others are less obvious. In Watertown, most sewers are over 50 years old, with some well over 100 years old.

These old pipes are prone to leaking, and some of the leaks make their way into the storm drain pipes and into our rivers. Old building sewers, particularly basement plumbing and floor drains, may have been inadvertently connected to a drain pipe instead of a sewer pipe or may themselves be leaky too.

How Do I Report an Illicit Discharge?

To report an illicit discharge, contact the Public Works Department at 617-972-6420. Many environmental problems can be resolved as a result of these investigations.

Have the following information available:

  • Name and contact information (if you would like a follow-up call)
  • Location of the incident
  • What materials that were involved in the incident
  • When you witnessed the incident (date and time)

Please report:

  • Clogged catch basins that are not draining stormwater during a storm.
  • Signs of recent spills of materials such as oil, paint, etc. near a catch basin
  • Someone pouring or sweeping anything down a catch basin (oil, paint, cleaning materials, litter, grass clippings, etc.)
  • Water coming from outfalls that looks oily, forthy or discolored

What is Watertown Doing About Illicit Discharges?

In May, 2011 the Town Council adopted an Illicit Discharge Ordinance (PDF) prohibiting illicit discharges to the storm drainage system. The Ordinance prohibits illicit discharges and includes provisions for enforcement.

The DPW has been conducting water quality monitoring of the Town’s outfalls since at least 2000 to identify where bacterial contamination was occurring to target those portions of the storm drain system for locating illicit discharges of sewage into the storm drain. In 2006, the DPW developed an Illicit Discharge Detection and Elimination Plan that was submitted to EPA and given approval to implement. The IDDE Plan presents a multi-phase program for systematically investigating the Town’s roughly 55 miles of storm drains to search for illicit discharges (direct and indirect) and take actions to remove the illicit discharge. The plan includes a variety of sampling methods, field investigations, and testing measures to identify the sources of illicit discharges.

Since June 2006 when the IDDE Plan was first implemented, 23 illicit discharges have been identified and corrected by the DPW removing an estimated 1,000 gallons per day of contaminated flow from the downstream outfalls. In almost every case where an illicit discharge was identified, it was caused by a defective sewer lateral or main leaking and migrating to a nearby storm drain pipe with an open joint or crack. It is very uncommon for the illicit discharge to be a hard-piped direct connection from a sanitary service to the storm drain.

IDDE Progress Reports

IDDE Progress Reports are prepared and submitted quarterly to EPA and present a summary of all the activities performed in the investigations for illicit discharges, the results of the quarterly water quality monitoring of the Town’s 27 river outfalls and 2 interconnections with adjacent Town’s storm drains, repairs made to the sewers and drains to remove illicit discharges, and a summary of the repairs and improvements made to the infrastructure by the DPW.

View the IDDE Reports.

IDDE Priority Catchment Areas (PDF)

Illicit Discharge Ordinance (PDF)