Overview

Outfall Reconnaissance Inventory and Outfall Mapping is one of the key elements of Minimum Control Measure (MCM) 3 Illicit Discharge Detection and Elimination (IDDE). According to this MCM the locations of all MS4 outfalls that discharge into waters of the State, must be field verified. In addition outfall reconnaissance inventory must be conducted at least once every five years.

Doing it yourself Vs Hiring Outside Help

Outfall Reconnaissance Inventory (ORI) can either be done internally or by hiring services from companies like Azertia. Some of pros and cons of doing the ORI in-house are listed below. The necessity and the urgency of doing an ORI should be the determining factor on which approach a municipality chooses.

Advantages of doing in-house ORI

Cost: Doing the ORI in-house can save money that the municipality does not have to spend on hiring an outside firm to do the work. It is important to keep a tight control on the scope of the work and plan the ORI well otherwise the cost can overshoot.

Timing: As the ORI has to be done covering every outfall at least once in a five year period, the work load is not very high. Municipalities can easily find employees with down time to do the ORI. However, the initial location and mapping of the outfalls takes significant time. If the resource availability is tight the municipality might consider hiring an external firm to do the initial outfall location and mapping and then handle the ORI in-house.

Focus: If the municipality is able to identify some problematic outfalls, doing the ORI in-house allows frequent checking of these outfalls. If an external firm is doing the ORI, the frequency depends on when the contract.

Advantages of hiring external firms for ORI

Trained Technicians: External firms (like Azertia) use technicians who are well trained and have experience in outfall location and inspection. They are able to identify any problems quickly and make a judgment on it.

Liability: Outfalls are typically located in wooded areas and are sometimes covered with rocks and debris. If the municipality uses interns  for either outfall location/mapping or ORI, they should be trained properly and operate in teams of 2 crew. Municipality may run into liability issues related to safety.  These liability issues do not arise when using an external firm to do the work.

GPS Quality: External firms (like Azertia) use mapping grade GPS to locate the outfalls that give an accuracy of 1-3 feet. If the municipality uses a recreational GPS to map the outfalls, the accuracy is in the range of 30-50 feet. This can make it difficult to relocate the outfalls when doing ORI every year.

Outfall Mapping & Reconnaissance Inventory Tips & Tricks

Azertia has been performing outfall mapping and ORI for more than 5 years. On the way we have learned several useful and important things that can be help any municipality that is trying to do this in-house.

1. Don't forget to take pictures when you are out locating the outfall or doing an ORI. Take at least 2 pictures for each outfall. One close up and the other zoomed out. Use a digital camera with "Image Stabilization" feature.

2. If you are not sure where the outfalls are located, identify all water bodies. Start at Catch basins located close to those water bodies and track the pipes from there.

3. Always keep a pair of rubber glove handy incase you have to take a water sample from the outfall.

4. Conduct the ORI in dry weather at least 48 hours after any rainfall event.

5. Use a 2 person crew for ORI

Free Resources

Inventory Form

Azertia has created a single page form for conducting the Outfall Reconnaissance Inventory. This form is similar to the one provided in the IDDE guidance manual, the main difference being the single page format.

You can download a copy of the form in PDF format by clicking here: Outfall Reconnaissance Inventory form (50KB)

If you need a copy of this form in Microsoft Word format, contact us by email.

Online Training

The US Environmental Protection Agency's office of wastewater management provides several webcasts and training courses. The two webcasts that are directly related to IDDE and Outfall mapping are listed below:

1. Developing Your IDDE Program (IDDE 101): This webcast starts with an overview of important IDDE terminology, a summary of findings and lessons learned from Phase I MS4 communities, and resultant key considerations for Phase II MS4 communities. Details are provided on the basic components of an effective IDDE program, including auditing existing resources; establishing legal authority' determining illicit discharge potential; developing program goals; searching for illicit discharges; eliminating and preventing illicit discharges; and evaluating program effectiveness.

2. Conducting Illicit Discharge Detection and Elimination Investigations (IDDE 201): Building on IDDE 101, this webcast discusses the field and lab methods necessary to conduct IDDE investigations. The webcast starts with a quick review of IDDE terminology and the basic components of an effective IDDE program. Details are then provided on how to prioritize field activities by conducting a desktop assessment of illicit discharge potential (IDO); how to conduct the Outfall Reconnaissance Inventory (ORI); post-screening prioritization; and detailed field sampling and lab analyses that may be used to confirm and identify illicit discharges.