HRS rule, page 51625
Level I concentrations. Assign value(s) from Table 4-23 to each sensitive environment subject to Level I concentrations.
For those sensitive environments that are wetlands, assign an additional value from Table 4-24. In assigning a value from Table 4-24, include only those portions of wetlands located along the hazardous substance migration path in the area of Level I concentrations. If a wetland is located partially along the area of Level I concentrations and partially along the area of Level II concentrations and/or potential contamination, then solely for purposes of Table 4-24, count the portion(s) along the areas of Level II concentrations or potential contamination under the Level II concentrations factor (section 220.127.116.11.1.2) or potential contamination factor (section 18.104.22.168.1.3), as appropriate.
Estimate the total length of wetlands along the hazardous substance migration path (that is, wetland frontage) in the area of Level I concentrations and assign a value from Table 4-24 based on this total length. Estimate this length as follows:
- For an isolated wetland or for a wetland where the probable point of entry to surface water is in the wetland, use the perimeter of that portion of the wetland subject to Level I concentrations as the length.
- For rivers, use the length of the wetlands contiguous to the in-water segment of the hazardous substance migration path (that is, wetland frontage).
- For lakes, oceans, coastal tidal waters, and Great Lakes, use the length of the wetlands along the shoreline within the target distance limit (that is, wetland frontage along the shoreline).
Calculate the Level I concentrations factor value (SH) for the watershed as follows:
WH = Value assigned from Table 4-24 to wwetlands along the area of Level I concentrations.
Si = Value(s) assigned from Table 4-23 to sensitive environment i.
n = Number of sensitive environmental from Table 4-23 subject to Level I concentrations.