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Targets: Wetlands

  • Wetlands, as well as the sensitive environments listed in HRS Table 4-23, are targets for the environmental threat.

    • Wetlands must meet the criteria stated in 40 CFR Section 230.3. This definition emphasizes vegetation types "typically adapted for life in saturated soil types."

  • The EPA definition of wetlands is different from the definition used by the U.S. Fish and Wildlife Service and on the National Wetland Inventory (NWI) maps.

    • For a comparison of the two definitions and an understanding of which types of wetlands appearing on the NWI are most apt to meet the HRS criteria, turn to A-20 through A-23 of the HRS Guidance Manual.

  • Wetlands that are important to the HRS score should be field-verified at the site inspection.

    • Some wetlands that appear on the USGS topographic maps no longer exist.
    • Other wetlands are found that do not appear on the maps.
    • Not all wetlands meet the criteria of 40 CFR 230.3.

  • Wetland values are assigned on the basis of frontage or perimeter.

    • Frontage on both sides of a stream or river is counted. This is illustrated in the HRS Guidance Manual by Highlights 8-61 through 8-64 beginning at page 333.
    • Perimeter is measured when the target is an isolated wetland or the probable point of entry (PPE) is within the wetland. This is illustrated in the HRS Guidance Manual by Highlight 8-65 on page 337. The segmentation of a wetland into zones of contamination is illustrated in Highlight 8-68 on page 342.
    • In HRS Table 4-24, page 51625, how many points are assigned for less than 0.1 miles of frontage or perimeter?

      The assignment of a value of 0 for less than 0.1 mile of frontage or perimeter is important when planning sample locations. Wrong location, no points.

      QUESTION: What is the difference in HRS target value between a Level I sample that picks up a bit more than 0.1 mile of wetland frontage versus a Level I sample that picks up a bit less than 0.1 mile? ANSWER

  • Total wetland frontage within the Target Distance Limit (TDL) is divided up into the frontage within Level I, Level II, and within each of the dilution ranges for potential.

    • This is the key difference between the listed sensititve environments in HRS Table 4-24 and wetlands. Wetland frontage is assigned to individual surface water segments. The listed environments have their value assigned as a block to the highest-valued segment they lie within, in whole or in part.

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