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Questions and Answers

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?

The wetland values for the frontage is either 25 or 0. Since the multiplier for Level I targets is 10, the difference in target values is the difference between 250 and 0.

If the average tidal cycle chloride content at a sampling point is 1,500 mg/l, should you use the freshwater or the saltwater benchmark?

Use the lower of the two benchmarks.

  • If the sensitive environment being evaluated is in fresh water, use fresh water value, except: if no fresh water value is available, use marine value if available.
  • If the sensitive environment being evaluated is in salt water, use marine value, except: if no marine value is available, use fresh water value if available.
  • If the sensitive environment being evaluated is in both fresh water and salt water, or is in brackish water, use lower of fresh water or marine values.

The PPE from the site is on a small stream with a streamflow of 25 cfs. The stream discharges into a large stream within about a mile from the site. The large stream has a streamflow of 250 cfs.

Three samples document observed releases to the small stream. The nearest sample is Level I and the next two are Level II.

There is wetland frontage along both the small and the large stream and habitats known to be used by two Federal designated endangered species are collocated with the wetlands.

The wetland frontage by zone of contamination is approximately:

Level I 100 feet
Level II 1400 feet
Potential (25 cfs) 3000 feet
Potential (250 cfs) 800 feet

What is the score for environmental targets?

Level I 10 for Level I x (o=(75+75)) 1500
Level II 1 for Level II x (25+(0)) 25
Potential 25 x 0.1 (dilution)
25 x 0.01 (dilution)
sum = 2.75 x 1/10 for potential
2.5
0.25
0.275
Targets 800 feet

The sensitive environments are assigned to Level I and are not counted in any of the other segments. A wetland value of 0 is assigned for the Level I frontage. All the other segments pick up a wetland value of 25. The value for potential is not rounded because it is less than 1. The HRS also instructs that the targets score not be rounded.

 

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