DTSC has entered into a binding agreement with the California Department of Transportation (Caltrans) for the management of airborne lead (ADL) contaminated soils excavated by Caltrans as part of highway improvement projects (agreement). These activities were previously covered by a derogation from certain hazardous waste laws from 1996 to 30 June 2016. DTSC took the decision in July 2015 to move from a waiver to this new agreement to ensure the continued protection of human health and the environment. The agreement states that all soils contaminated with ADLs with a lead concentration higher than the unrestricted use (currently 80 mg/kg) of Caltrans must be properly managed. The agreement applies to existing and new Caltrans projects from 1 July 2016. The gap, which previously covered the management of ADL-contaminated soil excavated during caltrans highway improvement projects, ended on June 30, 2016. The management activities to which this Agreement generally applies are the storage, disposal, monitoring, transport and final disposal of ADL-contaminated soils. The DTSC will monitor compliance with the agreement and continue road improvement projects that reuse ADL-contaminated soils. Refineries in the United States began adding lead compounds to gasoline in the 1920s to increase octane and improve engine performance by reducing engine “knocking” and allowing for higher engine compression.
Exhaust emissions from automobiles using leaded gasoline contained lead and caused ADL to be deposited in and along roads across the state. The phasing out of lead in gasoline began in 1974 when the U.S. Environmental Protection Agency (EPA), under the supervision of amendments to the Clean Air Act of 1970, introduced rules requiring the use of unleaded gasoline in new cars equipped with catalytic converters. The introduction of catalysts to control emissions of hydrocarbons, nitrous oxide and carbon monoxide has forced motorists to use unleaded gasoline, as lead destroys the ability of catalysts to reduce emissions. By the early 1980s, lead levels in gasoline had declined by about 80% due to regulations and fleet sales. Beginning in 1992, lead was banned as a fuel additive in California. ADL-contaminated soils still exist along roads and medians and can also be found under some existing road surfaces due to previous construction activities. The transport of these soils to hazardous waste landfills calls into question the state`s limited capacity to dump hazardous waste and increases air pollution due to truck traffic. The alternative of transporting the soil out of the disposal state is resource-intensive and contradicts caltrans`s policy. By managing the soil in accordance with this agreement, Caltrans will reduce hazards, maintain landfill capacity and reduce the air quality impact associated with transporting soil for several kilometres to landfills, while protecting human health and the environment. .