For releases to ditches, discrete samples should be taken approximately every 20' along the ditch in the areas which have been contaminated. In general, excavated areas should not be backfilled with soil until sample results are received indicating all significant contamination has been removed. In the event that the excavation could be considered a physical hazard, one possibility might be to line the hole with Visqueen and replace the dirt in a manner such that it could be removed if testing results indicate the soil needs remediation. For soils which have been excavated and are to be disposed off-site, one grab sample should be taken for every 20 yards of material. Up to 10 of these grab samples may be composited together for analysis to characterize up to 200 yards of contaminated soil.
All samples are to be obtained from the areas of greatest visual contamination.
If there is any reason to believe that groundwater has been contaminated as a result of the spill or the spill is in a known groundwater protection zone, please contact the WMD for further assistance. Additionally, the soil cannot be left in place if it fails the TCLP test for hazardous waste. It is possible it could fail at 400 ppm. A variety of detection limits are used for the tests. Laboratory detection levels should be sufficiently sensitive to make the above determinations.