Sedimentation basin performance at highway construction sites.

Area of Science:

• Environmental Engineering
• Water Quality Management
• Highway Construction Runoff

Background:

• Sedimentation basins (SBs) are critical for managing stormwater and pollution during highway construction.
• Their effectiveness in sediment removal and attenuation of storm waters is often assumed but requires rigorous evaluation.

Purpose of the Study:

• To evaluate the sediment removal efficiency of SBs used in highway construction.
• To assess the impact of construction site runoff and natural acidic drainages on water quality within SBs.

Main Methods:

• Monitoring of four SBs along a highway construction project in Pennsylvania over a 12-month period.
• Collection and analysis of inlet and outlet water samples for various parameters including TSS, metals, and pH.
• Observation and analysis of acidic seep impacts on SB water chemistry.

Main Results:

• Concentrations of TSS, aluminum, manganese, iron, and phosphate peaked with rainfall events.
• Sediment re-suspension occurred, with outlet TSS sometimes exceeding inlet TSS.
• SBs managed high flows but were generally ineffective at particulate capture.
• Acidic seeps introduced high dissolved metal and sulfate concentrations.

Conclusions:

• Current SB designs are inadequate for effective particle and associated metal removal.
• There is a need for revised Best Management Practices (BMPs) for SB design to address contemporary water quality concerns.
• Naturally occurring acidic drainages significantly impact SB water quality, necessitating specific management strategies.