OAR 340-122-0340: Cleanup Rules for Leaking Petroleum UST Systems: Sample Number and Location

The collection and analysis of soil samples is required to verify that a site meets the requirements of these rules. These samples must represent the soils remaining at the site and must be collected after contaminated soils have been removed or remediated. Each sample must represent a single location; composite samples are not allowed. The number of soil samples required for a given site and the location at which the samples are to be collected are as follows: (1) A minimum of two soil samples must be collected from the site: (a) These samples must be taken from those areas where obviously stained or contaminated soils have been identified and removed or remediated; (b) If there are two or more distinct areas of soil contamination, then a minimum of one sample must be collected from each of these areas; (c) The samples must be taken from within the first foot of native soil directly beneath the areas where the contaminated soil has been removed, or from within the area where in-situ remediation has taken place; (d) A field instrument sensitive to volatile organic compounds may be used to aid in identifying areas that should be sampled, but the field data may not be substituted for laboratory analyses of the soil samples; (e) If there are no areas of obvious contamination, then samples must be collected from the locations specified in sections (2)–(5) of this rule which are most appropriate for the situation; (f) If it is being proposed that a pocket of contamination be left in place pursuant to OAR 340-122-0355(4), then sufficient samples must be collected from the site in order to estimate the extent, volume, and level of contamination in this pocket, and the likelihood for the remaining contamination to result in unacceptable risk levels due to volatilization into buildings. (2) If water is not present in the tank pit: (a) Soil samples must be collected from the native soils located no more than two feet beneath the tank pit in areas where contamination is most likely to be found; (b) For the removal of an individual tank, samples must be collected from beneath both ends of the tank. For the removal of multiple tanks from the same pit, a minimum of one sample must be collected for each 150 square feet of area in the pit. (3) In situations where leaks have been found in the piping, or in which released product has preferentially followed the fill around the piping, samples are to be collected from the native soils directly beneath the areas where obvious contamination has been removed. Samples should be collected at 20-foot intervals. (4) If water is present in the tank pit, regardless of whether obvious contamination is or is not present, the Department must be notified of this fact. The responsible person shall then either continue the investigation under OAR 340-122-0240, or do the following: (a) Purge the water from the tank pit and dispose of it in accordance with all currently applicable requirements. This might require obtaining appropriate permits from the Department or local jurisdictions; (b) If the pit remains dry for 24 hours, testing and cleanup may proceed according to the applicable sections of these soil matrix cleanup rules. If water returns to the pit in less than 24 hours, a determination must be made as to whether contamination is likely to have affected the groundwater outside of the confines of the pit as indicated below: (A) For the removal of an individual tank, soil samples are to be collected from the walls of the excavation next to the ends of the tank at the original soil/water interface. For the removal of multiple tanks from the same pit, a soil sample is to be collected from each of the four walls of the excavation at the original soil/water interface; (B) At least one sample must be taken of the water in the pit regardless of whether obvious contamination is or is not present. This sample shall be collected as required by OAR 340-122-0345(4); (C) The soil samples must be analyzed for TPH and benzene, toluene, ethylbenzene, and xylenes (BTEX). The water sample must be analyzed for BTEX at all sites, and for PAHs where releases of non-gasoline fractions have occurred. Responsible persons may use TPH analyses on groundwater samples as a preliminary screen for PAHs. The TPH method detection limit must be no greater than 0.5 ppm. Any groundwater sample for which TPH is detected must be analyzed for PAHs. These analyses must be made using the methods specified in OAR 340-122-0218. The results of these analyses must be submitted to the Department; (D) The Department shall then determine how the cleanup shall proceed as specified in OAR 340-122-0355(3). (5) In situations where tanks, pumps, and lines will remain in place in areas of suspected contamination, the responsible person must submit a specific soil sampling plan to the Department for its approval. (6) In situations where TPH analysis indicates that contamination is present due to a release from a waste oil tank, at least one sample of the waste oil contaminated soils must be collected and analyzed for volatile chlorinated solvents, volatile aromatic solvents, and leachable metals (Cadmium, Chromium and Lead) using the analytical methods specified in OAR 340-122-0218(1)(c). Analysis for PCBs is also required if the contamination is from a waste oil tank other than one used exclusively for storage of automotive waste oils.