Maintenance Guidelines for Accumulated Sediments in Retention/Detentions Ponds Receiving Highway Runoff

摘要

A two year study funded by FDOT and FHWA was conducted to investigate sedimentation rates, heavy metal enrichment (Cd, Cr, Cu, Fe, Pb, Ni and Zn) and leaching of metals using TCLP methodology by U.S. EPA from accumulated bottom sediments in detention/retention ponds. These studies assist in developing criteria for maintenance guidelines. Nine ponds covering the state of Florida from Ocala to Miami were studied. The accumulated top loose sediments exhibited higher percent moisture and % volatile matter and lower density than the underlying firm soil. They also showed higher nutrient content and heavy metal content. Metals are retained in the sediments and TCLP results suggest that these sediments are not hazardous waste. Therefore, land disposal of dredged sediments could be possible. A predictive empirical model for the accumulated sediment rates was developed to assist in the determination of the clean out cycle. The calculated clean out cycles for study ponds averaged 25 years.