Remediation & Mitigation Strategies Flashcards

Which condition most often causes a bioswale to fail and require remediation within the first five years of installation?

Answer: Concentrated flow entry points that cause channelization and erosion

Bioswales depend on sheet flow entry; concentrated inflows scour the channel, create rills, and bypass the vegetated treatment zone, causing rapid degradation.

A Certified Stormwater Manager is evaluating a site where previous land use involved dry cleaning operations. Which stormwater mitigation concern is most critical?

Answer: Chlorinated solvent (PCE/TCE) mobilization into stormwater

Dry cleaning operations commonly contaminate soil and groundwater with PCE and TCE, which can be mobilized by stormwater infiltration or surface runoff.

Which maintenance practice is most important to sustain the pollutant removal performance of a stormwater infiltration trench over its design life?

Answer: Periodic sediment removal from the pretreatment device upstream

Sediment accumulation in the pretreatment device (e.g., sediment trap or filter strip) is the primary cause of premature clogging; removing it extends infiltration trench life significantly.

Which design parameter is used to calculate the 'channel protection volume' in low-impact development stormwater design?

Answer: The runoff volume from the 1-year, 24-hour storm event

Channel protection volume is typically based on capturing and slowly releasing the 1-year storm runoff over 24–48 hours to prevent bankfull erosion in downstream channels.

In a Stormwater Pollution Prevention Plan (SWPPP), what is the primary purpose of a 'source identification' section?

Answer: To catalog all potential pollutant sources and their locations on site

Source identification maps and lists all activities, materials, and areas on site that could contribute pollutants to stormwater, guiding the selection of targeted BMPs.

Which performance standard is most commonly used in the northeastern United States to size stormwater BMPs for channel protection?

Answer: Reduce post-development peak discharge to pre-development rates for the 2-year and 10-year storms

The 2-year and 10-year storm peak flow matching standard is widely adopted in the northeast to protect receiving channels from increased erosive flows due to development.

Which assessment method is used to evaluate whether a stormwater BMP retrofit project has achieved its target pollutant load reduction in a TMDL watershed?

Answer: Load duration curve analysis combining flow frequency and concentration data

Load duration curves plot pollutant loading versus flow percentile exceedance, allowing managers to compare monitored loads against TMDL targets across the full range of hydrologic conditions.