On February 8, 2017, EPA issued a CERCLA ? 106 Unilateral Administrative Order (UAO) to BAE Systems Information and Electronic Systems Integration, Inc. (BAE) to conduct the Pre-Remedial Design Investigation at Operable Unit 1 (OU1) of the North Penn Area 5 Superfund Site located in Montgomery and Bucks Counties, Pennsylvania (Site). EPA has determined that the actual or threatened release of hazardous substances may pose an imminent and substantial endangerment to public health or welfare or the environment. Trichloroethylene (TCE) and the other volatile organic compounds detected at the Site are ?hazardous substances? within the meaning of Section 101(14) of CERCLA. Data collected in 2014 demonstrated that TCE, which has an MCL of 5 μg/l, persists in the OU1 bedrock aquifer with a high value of 150 μg/l of TCE and that 1,1-dichloroethene (1,1-DCE) is also present in the bedrock aquifer with a high value of 130 μg/l. Present data also demonstrate that the plume has not been adequately delineated, and the migratory path of the plume has not yet been defined in certain directions.