At each selected sampling location for bulk PCB remediation waste or porous surfaces, collect at least 20 milliliters of waste, or a portion of sufficient weight for the chemical analyst to measure the concentration of PCBs and still have sufficient analytical detection sensitivity to reproducibly measure PCBs at the levels designated in Sec. 761.61(a)(4). Use a core sampler having a diameter =2 cm and <=3 cm. Collect waste to a maximum depth of 7.5 cms.