Check dam and polyacrylamide performance under simulated stormwater runoff.

Area of Science:

• Environmental Engineering
• Water Quality Management
• Erosion Control

Background:

• Construction sites frequently discharge stormwater with high turbidity and fine suspended sediments.
• Existing best management practices (BMPs) for sediment control are not always sufficient.

Purpose of the Study:

• To evaluate the turbidity reduction efficiency of three check dam types.
• To assess the impact of polyacrylamide (PAM) treatment on sediment retention and turbidity reduction.

Main Methods:

• Tested three check dam types: rock, excelsior wattle (fiber check dam - FCD), and rock + excelsior erosion control blanket (ECB).
• Installed check dams in a lined ditch and simulated three consecutive stormwater flows.
• Applied granular polyacrylamide (PAM) to check dams using two sediment sources with varying clay content.

Main Results:

• Without PAM, excelsior wattles and rock + excelsior ECBs achieved significantly lower effluent turbidity (<440 NTU) compared to rock check dams (>900 NTU).
• Sediment deposition was greatest behind excelsior wattles, followed by rock + excelsior ECBs, then rock check dams.
• PAM treatment reduced turbidity by over 75% for all check dam types, with excelsior wattles and rock + excelsior ECBs showing excellent performance (<90 NTU) even after the third storm event.

Conclusions:

• Fiber check dams (FCDs) and rock check dams with excelsior ECBs offer superior sediment retention and turbidity reduction compared to standard rock check dams.
• Passive treatment of construction site runoff with PAM on FCDs or rock + excelsior ECBs is a highly effective strategy for improving water quality.