ARSD 74:56:05:07. Tier 1 action levels -- Criteria for calculation

The department shall calculate Tier 1 action levels shown in Table 1 in this section based on the petroleum contamination in soil leaching to the groundwater pathway, with an excess lifetime cancer risk not exceeding 1:100,000 and a chronic noncancer risk not exceeding a hazard index of one. The department assumes there are receptors actually or potentially ingesting groundwater at the point of maximum soil contamination. Table 1 is as follows: TIER 1 ACTION LEVELS FOR SOILS AT PETROLEUM RELEASE SITES Tier 1 Action Level (ppm = parts per million) 0.2 ppm Toluene 15 ppm Ethylbenzene 10 ppm Xylene 300 ppm Napthalene 25 ppm