This is an Administrative Order pursuant to CERCLA Section 106(a) issued to Walker Power Systems, Union Pacific Railroad, and Tiernay Properties. Respondents are each former or current owners or operators of the property at the time of disposal of hazardous substances, primarily volatile organic compounds (VOCs). The Order requires the Respondents to conduct a remedial investigation/feasibility study to characterize residual VOC contamination from aluminum parts cleaning and refurbishing operations conducted at the property from 1976 to the present. The Order also requires analysis of the facility's contribution to the Motorola 52nd Street Site groundwater plume, and requires payment of EPA's response costs incurred under the Order.