Illicit Discharge Detection & Elimination (IDDE) Flashcards
7 cards from real CSM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Illicit Discharge Detection & Elimination (IDDE) flashcards as text
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?
Answer: A cross-connected laundry or washing machine drain
Gray, sudsy water during dry weather is a classic sign of laundry or household washing machine wastewater cross-connected to the storm drain, due to the presence of detergents and surfactants.
What is the recommended approach for tracing an illicit discharge upstream once flow is confirmed at an outfall during dry weather?
Answer: Walk the contributing drainage area and systematically check manholes and inlets moving upstream
Systematic upstream manhole and inlet investigation — walking the system from the outfall — is the standard IDDE field methodology to isolate the source of an illicit discharge.
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?
Answer: Optical brighteners or fluorescent dye
Fluorescent dyes (such as fluorescein or rhodamine) or optical brighteners are introduced into building drains and detected downstream in the storm sewer to confirm an illicit connection.
When an IDDE inspector discovers a confirmed illicit discharge from a commercial facility, what is the appropriate immediate response?
Answer: Document findings, notify the appropriate regulatory authority, and require the discharger to eliminate the connection within a specified timeframe
Confirmed illicit discharges require documentation, regulatory notification, and an enforcement action requiring the responsible party to eliminate the source within a permit-specified timeframe.
Which of the following best describes a 'sanitary sewer cross-connection' in the context of an MS4 system?
Answer: A physical connection between a building's sanitary drain and the storm sewer that allows sewage to enter the storm system
A sanitary sewer cross-connection occurs when a building's plumbing — either intentionally or by error — routes sewage into the storm sewer instead of the sanitary sewer, causing illicit discharge.
Under most NPDES MS4 permit requirements, what is the minimum information that must be maintained in a storm sewer system map for IDDE purposes?
Answer: The location of storm drain inlets, pipes, and outfalls, and the receiving waters to which they drain
NPDES MS4 permit IDDE requirements specify that the system map must show storm sewer locations, outfalls, and the receiving waters they discharge to, enabling effective field investigations.
Which of the following outfall observations would be LEAST likely to indicate an illicit discharge during a dry-weather field screening visit?
Answer: A small trickle of clear, odorless water at an outfall 72 hours after a significant rain event
A small trickle of clear, odorless water 72 hours after significant rainfall is likely base flow or subsurface drainage, a common allowable condition, and is the least indicative of an illicit discharge.