On October 13, 1943, a United States Army Air Force aircraft crashed on land located near the southwest corner of Kimball and Grove Avenues in Chino, California. The Crash Site is approximately 3000 square feet in area. In 2002, P purchased approximately 136-acres of property, which included the Crash Site. Ps were going to develop the land into a commercial and residential development. In 2000, prior to purchasing the Property, Ps hired an environmental consulting company to conduct a site investigation and report on the Property. This pre-purchase review did not uncover any evidence of contamination. In early December 2003, Ps were grading portions of the Property for development by removing 10,000 cubic yards of soils from land which included the Crash Site and putting the soils into Fill Site A. On December 5, 2003, they found .50 caliber machine gun rounds in Fill Site A. Operations were immediately halted and the area was cordoned off. The Fire Department Bomb Squad inspected the premises and remove all visible ordnance from the Crash Site. Ps then sought proposals from private contractors to clear munitions from Fill Site A. Operations resumed and the soils from the December 10th excavation were placed in an area referred to as Fill Site B. Ps eventually met with the Department of Toxic Substances Control, School Property Evaluation, and Cleanup Division (DTSC) to discuss an investigation and cleanup of munitions. DTSC sent a letter to Ps approving a work plan to remediate approximately 10,000 cubic yards of soil in Fill Site A that originated from the Crash Site. The approval letter did not address the removal of soils from Fill Sites B and C, or from the original Crash Site. Eventually, DTSC investigated and removed all ordnance and explosives (OE) with regard to Fill Sites A, B, and C and the Crash Site. In total, 46,442 tons of soil were processed through a soil screening plant, and 163 OE and suspect-OE were recovered. Ps sued D to recover $3.2 million in costs that Ps incurred in cleaning up a World War II airplane crash site that Ps discovered on their property in Chino, California. Ps argue that D bears all cleanup costs under section 107 of CERCLA on the basis that Ps qualify as 'innocent landowners.'