CSM Illicit Discharge Detection & Elimination (IDDE)

Question 1

Which federal regulatory program is the primary driver requiring MS4 operators to develop and implement Illicit Discharge Detection and Elimination (IDDE) programs?

Accepted Answer

NPDES Phase I and Phase II Stormwater Permit Program

Answer

Clean Water Act Section 401

Answer

Safe Drinking Water Act Surface Water Treatment Rule

Answer

Resource Conservation and Recovery Act Subtitle D

Question 2

Which of the following is correctly classified as an illicit discharge to a municipal separate storm sewer system (MS4)?

Accepted Answer

Residential car washing wastewater entering a storm drain

Answer

Uncontaminated groundwater infiltration into storm pipes

Answer

Stormwater runoff from a construction site with an active permit

Answer

Irrigation return flows from agricultural operations

Question 3

What is the first critical step in establishing a municipal IDDE program?

Accepted Answer

Creating and maintaining a complete map of the storm sewer system

Answer

Installing dry-weather flow monitoring equipment at all outfalls

Answer

Issuing fines to businesses with suspected illegal connections

Answer

Training field staff in water quality sampling procedures

Question 4

Which water quality indicator is most commonly used in field screening to detect the presence of sanitary sewage contamination in stormwater outfall flows?

Accepted Answer

Fecal coliform or E. coli bacteria

Answer

Total dissolved solids (TDS)

Answer

Turbidity (NTU)

Answer

Total suspended solids (TSS)

Question 5

What is the primary purpose of conducting dry-weather screening at storm drain outfalls?

Accepted Answer

To detect non-stormwater flows that may indicate illicit connections or discharges

Answer

To measure peak flow rates for hydraulic modeling

Answer

To assess the structural integrity of outfall pipes

Answer

To calculate pollutant loading from impervious surfaces

Question 6

Under NPDES MS4 permits, which of the following discharges is typically listed as an allowable non-stormwater discharge and is NOT considered illicit?

Accepted Answer

Lawn watering and landscape irrigation runoff

Answer

Wastewater from floor drains in auto repair shops

Answer

Washwater from washing out concrete mixers

Answer

Discharge from portable toilet cleanouts

Question 7

Which field parameter, when measured above ambient background levels at a storm drain outfall during dry weather, is a strong indicator of a sanitary sewer cross-connection?

Accepted Answer

Surfactants (detergents) above background levels

Answer

Dissolved oxygen below 5 mg/L

Answer

pH between 6.5 and 8.5

Answer

Conductivity below 100 µS/cm