2.
Groundwater Response Actions
What is included: (Examples)
What is not included: (Examples)
Actions affecting cleanup of the various phases and
media in a groundwater system by removing,
destroying or containing contaminants in the dissolved
and sorbed phase from below the water table, including
pump-and-treat, monitored natural attenuation/
biodegradation, reactor trenches, in-situ groundwater
treatment, hydraulic containment of NAPL (not NAPL
recovery itself - see Category 6; see also Explanations
and Notes, No. 2, below)
The volume of water extracted and treated (*see notes,
below), non-aqueous phase liquid recovery (see
Category 6; see also Explanations and Notes No. 2,
below)
Target of this measure category:
Units for reporting this measure:
Physical volume of aquifer formation, including
matrix, water, and contaminant (not just the water) that
is contaminated above ROD cleanup standards and will
be subject to the response action.
Thousands of Cubic Yards (1000•yd3)
Methodology for calculating the measure:
1. Assemble a contaminant icoconcentration contour
map (“plume map”) for each hydrostratigraphic unit
(aquifer layer), and collect the information available on
the thickness of each unit.
2. For each unit, calculate either: (1) the physical area
which lies within the icoconcentration contour defining
the ROD cleanup standard the system will achieve, or
(2) the area which will be treated or addressed by the
groundwater treatment system or response action in
that unit. These two calculations should provide
similar results.
3. For each unit, multiply the area derived in (2) by the
average thickness of that unit to get a volume for that
unit (see Explanations and Notes No. 2, this category,
below).
4. Add the volumes derived in (3) for each of the units
involved to get a total volume.
5. Convert the volume to cubic yards and divide by
1000 to get the reporting volume in 1000s of cubic
yards.
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Useful conversion factors:
1 cubic yard = 27 cubic feet
1 cubic foot = 0.037 cubic yards
1 acre = 4840 square yards
1 square mile = 3,097,600 square yards
1 square mile•foot = 1,032,533 cubic yards
1 cubic mile = 5,451,776,000 cubic yards
Additional methodology elements for
special cases:
(1) In groundwater containment remedies using either
pump-and-treat or biodegradation, calculate the volume
of aquifer formation that is being contained (so that
contaminants cannot escape the containment zone)
(2) If the thickness of an aquifer unit varies by more
than 50% across the area in question, do not use the
average thickness, but divide the volume of affected
aquifer up into smaller subvolumes such that the
variation in thickness within each subvolume is less
than 50%. Then, (a) run the calculation for each of the
subvolumes, (b) add the subvolumes together to get a
total volume for that one hydrostratigraphic unit, and
finally, (c) add all the unit volumes to get the total
reported volume.
(3) If pump-and-treat will be used for part of the
cleanup and monitored natural attenuation will be used
for another part, and both processes will attain the
ROD standards, then report the volume as the sum of
the volumes being treated by each both process.
Explanations and notes:
(1) This method does not calculate the volume of water
pumped and treated. Make sure that you are
calculating the total volume of actual aquifer formation
(not just water) that is contaminated above treatment
standards and will be addressed by the system. Note
that aquifer porosity is not pertinent to the calculation,
because the goal is to clean the entire aquifer system of
contamination, not merely the water in the formation.
(2) There is a critical difference between NAPL
hydraulic containment and NAPL recovery. The former
actually contains the water around the NAPL to keep
dissolved contaminants from escaping. It is a
groundwater response action in that it addresses
dissolved phase contaminants. This type of response
action falls in this category. The latter, NAPL
recovery, involves removing pure NAPL from the
ground in the residual phase. This is addressed in
Category 6.
Source: 12/12/03 "Final Methodology for Estimating Superfund and RCRA Corrective Action
Case Conclusion Data Sheet (CCDS) Environmental Benefits", pp. 7 - 12 of the guidance.