Measure 3d: Implement illicit
“Implement an inspection program to detect dry weather
flows at system outfalls. Establish procedures for tracing the sources of
illicit discharges and for removing the sources. Develop procedures for
identification of priority areas likely to have illicit
discharges. Continue to identify, locate and update map of drainage system
components on a priority basis per approved Illicit Discharge Program.”
inspection is one of the most commonly used methods for identifying
Outfall inspections are easy and inexpensive to implement
and you can verify and update your storm sewer base map as you conduct
them. The disadvantage of outfall inspections is that illicit discharges
occur periodically and can be hard to find unless you are at the right
place at the right time. (That is why your permit also requires you to
have a public reporting mechanism so that your citizens can help find the
illicit discharges as they occur.)
There are four steps to completing the outfall detection
- Prioritize areas for inspection.
- Design an outfall tracking system.
- Conduct outfall inspections.
- Trace and remove illicit discharges.
Step 1: Prioritize areas for inspection
Each year, select a portion of your jurisdiction’s area
for dry weather inspection, starting with the highest priority areas and
moving to lower priority areas. Check your Stormwater Plan to see if you
agreed to inspect a certain percentage of your jurisdiction's area each
As you prioritize areas within your jurisdiction, bear in
mind the most common source of illicit discharges are:
- Illegal dumping
- Floor drains improperly connected to the storm sewer
- Broken sanitary sewer line
- Cross-connections with sewer line
- Sanitary sewer overflows
- Straight pipe sewer discharge
- Failing septic system
Potential high priority areas are older sections of town,
commercial or mixed use areas, high density areas, etc. Each year, you
should document your basis for selecting the high priority area.
Step 2: Design an outfall tracking system
You will also need to develop a tracking system to report
illicit discharges, suspect outfalls, citizen complaints, enforcement
actions and corrective measures. The Center for Watershed Protection has
developed an Outfall
Reconnaissance Inventory / Sample Collection Field Sheet to assist the
Phase II’s as they inspect their outfalls.
Step 3: Conduct outfall inspections
least two staff members should work together to conduct the inspections.
The most common approach to outfall inspection is to complete a visual
inspection of the outfall and a qualitative assessment of any flow
present, including observation of water color, odor, turbidity, floatables
and sediment (Zielinski and Brown 2001). In some cases, if the flow is
suspected to be inappropriate, a follow-up grab sample is taken for
quantitative assessment. Some local governments bypass the quantitative
tests and immediately move upstream to find the source of the discharge.
Step 4: Trace and remove illicit discharges
If you find an illicit discharge in the field, you should
try to identify the source of the discharge. Investigation of suspicious
discharges will be made by visual inspection and/or testing of discharges
within the storm drainage system upstream of the suspicious discharge.
Letters may be sent to residents and businesses alerting them to the
problem that is under investigation to solicit their assistance in finding
the source. A building-by-building evaluation may also be used in areas
where a problem has been isolated to a small area.
Once you have identified the source of the illicit
discharge, your staff should notify the responsible party verbally if
possible and follow-up with written notification. The written notice will
provide contact information as well as a schedule for the responsible
party to remove the illegal discharge. If the responsible party does not
comply with the schedule or receive approval for a revised schedule, you
will need to take enforcement action as defined in your ordinance.
EPA has developed guidance for removing the following
common sources of illicit discharges: