Holdrege & Kull performed an Initial Site Assessment (ISA) and a Phase II soil investigation for this improvement project, located south of Chico. The project was funded in part by Caltrans and by the County of Butte. Engineering design and environmental review was overseen by the Butte County Association of Governments and was subject to Caltrans’ design and environmental standards. The project was intended to address the higher-than-average accident rates at the intersection by installing signals and by constructing and improving turn lanes.
To facilitate environmental review, H&K performed an ISA in conformance with Caltrans requirements and the ASTM Practice E 1527-05. The ISA identified the potential for aerially deposited lead (ADL) associated with past leaded fuel vehicle emissions adjacent to the older, southbound lanes of State Route 99, as well as the potential for elevated metals concentrations in paint and thermoplastic striping.
Because soil disturbance was proposed as part of the intersection improvements, H&K performed a Phase II ADL investigation. H&K’s investigation included the development of a statistically defensible sampling plan and health and safety plan, soil sampling, laboratory analysis, and traffic control performed under a Caltrans encroachment permit. H&K’s statistical evaluation of the laboratory results demonstrated that soil in the proposed construction areas did not contain ADL at levels that would present a significant risk to site workers. Thus, the project did not require soil management in accordance with the applicable Caltrans special provisions for ADL or Variance No. V09HQSCD006 issued by the California Department of Toxic Substances Control.