As part of its electrical distribution system, Con Edison maintains approximately 275,000 underground structures (manholes, service boxes, and vaults) that contain electrical distribution cables and other electrical distribution equipment. Many of these structures contain sediment, which contains lead and other heavy metals from street runoff and equipment repair and maintenance activities. In order to safely work in these structures, the sediment must be removed and properly disposed of. After the Environmental Protection Agency issued the Toxicity Characteristic Leaching Procedure (TCLP) rule, Con Edison performed an extensive sampling and analysis program to determine whether the sediment in these structures exceeded hazardous waste thresholds. Based on the results of this sampling program, Con Edison decided to manage the sediment in manholes and some service boxes as hazardous waste due to the lead characteristic. Since management of these wastes as hazardous created regulatory burdens and resulted in high disposal costs, several lead stabilization chemicals and methods were investigated in an effort to render the wastes non-hazardous before they are removed from the underground structures. Initially, three lead stabilization chemicals were evaluated in the field. Two were found to be unsuitable, because they failed to successfully stabilize the lead and/or caused handling, waste management, or dusting problems. The other chemical, a liquid, buffered phosphate treatment reagent, was found to be potentially acceptable. More extensive field tests using this chemical indicated that it could successfully stabilize the lead in a manner that protects the safety of our workers and the public. Accordingly, Con Edison has entered into discussions with regulatory agencies regarding use of this chemical. This paper describes how Con Edison currently manages lead-contaminated sediment, the results of our evaluation of lead stabilization options, our proposed future sediment management program and the relevant federal, state, and local waste management requirements that apply under both current and proposed waste management scenarios.
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