CSM Illicit Discharge Detection & Elimination (IDDE) 2

Question 1

During an IDDE field investigation, a field technician observes gray, sudsy water flowing from an outfall during dry weather. Which upstream source is MOST likely responsible?

Accepted Answer

A cross-connected laundry or washing machine drain

Answer

A leaking underground storage tank (UST)

Answer

Stormwater ponded in a nearby retention basin

Answer

An overflowing sanitary manhole several blocks away

Question 2

What is the recommended approach for tracing an illicit discharge upstream once flow is confirmed at an outfall during dry weather?

Accepted Answer

Walk the contributing drainage area and systematically check manholes and inlets moving upstream

Answer

Sample the outfall water and wait for laboratory results before any field work

Answer

Issue violation notices to all businesses in the drainage area

Answer

Install automated samplers at the outfall and review data remotely

Question 3

Which chemical tracer is commonly used by inspectors to confirm a specific building's drain is connected to the storm sewer rather than the sanitary sewer?

Accepted Answer

Optical brighteners or fluorescent dye

Answer

Sodium chloride (table salt)

Answer

Potassium permanganate

Answer

Sodium hypochlorite (bleach)

Question 4

When an IDDE inspector discovers a confirmed illicit discharge from a commercial facility, what is the appropriate immediate response?

Accepted Answer

Document findings, notify the appropriate regulatory authority, and require the discharger to eliminate the connection within a specified timeframe

Answer

Issue a warning letter and schedule a reinspection in 90 days

Answer

Plug the storm drain outfall to prevent further discharge to the receiving water

Answer

Refer the matter to the EPA Region office and take no local action

Question 5

Which of the following best describes a 'sanitary sewer cross-connection' in the context of an MS4 system?

Accepted Answer

A physical connection between a building's sanitary drain and the storm sewer that allows sewage to enter the storm system

Answer

A pipe that carries both stormwater and treated wastewater to the same outfall

Answer

A sewer manhole that is shared between the storm and sanitary systems for maintenance access

Answer

An overflow structure on a combined sewer that diverts excess flow during storms

Question 6

Under most NPDES MS4 permit requirements, what is the minimum information that must be maintained in a storm sewer system map for IDDE purposes?

Accepted Answer

The location of storm drain inlets, pipes, and outfalls, and the receiving waters to which they drain

Answer

Pipe material only

Answer

Only outfall locations and receiving water names

Answer

The age and condition rating of each pipe segment

Question 7

Which of the following outfall observations would be LEAST likely to indicate an illicit discharge during a dry-weather field screening visit?

Accepted Answer

A small trickle of clear, odorless water at an outfall 72 hours after a significant rain event

Answer

Bright orange or reddish staining around the outfall pipe

Answer

A persistent flow with a sewage odor and gray coloration

Answer

Oily sheen on the water surface near the outfall