Current through Register Vol. 48, No. 52, December 27, 2024
a) Natural attenuation, access controls, and
point of use treatment shall not be considered engineered barriers. Engineered
barriers may not be used to prevent direct human exposure to groundwater
without the use of institutional controls.
b) For purposes of determining remediation
objectives under Tier 1, engineered barriers are not recognized.
c) The following engineered barriers are
recognized for purposes of calculating remediation objectives that exceed
residential remediation objectives:
1) For
the soil component of the groundwater ingestion exposure route, the following
engineered barriers are recognized if they prevent completion of the exposure
pathway:
A) Caps or walls constructed of
compacted clay, asphalt, concrete or other material approved by the Agency;
and
B) Permanent structures such as
buildings and highways.
2) For the soil ingestion exposure route, the
following engineered barriers are recognized if they prevent completion of the
exposure pathway:
A) Caps or walls
constructed of compacted clay, asphalt, concrete, or other material approved by
the Agency;
B) Permanent structures
such as buildings and highways; and
C) Soil, sand, gravel, or other geologic
materials that:
i) Cover the contaminated
media;
ii) Meet the soil
remediation objectives under Subpart E for residential property for
contaminants of concern; and
iii)
Are a minimum of three feet in depth.
3) For the outdoor inhalation exposure route,
the following engineered barriers are recognized if they prevent completion of
the exposure pathway:
A) Caps or walls
constructed of compacted clay, asphalt, concrete, or other material approved by
the Agency;
B) Permanent structures
such as buildings and highways; and
C) Soil, sand, gravel, or other geologic
materials that:
i) Cover the contaminated
media;
ii) Meet the soil
remediation objectives under Subpart E for residential property for
contaminants of concern; and
iii)
Are a minimum of ten feet in depth and not within ten feet of any manmade
pathway.
4)
For the ingestion of groundwater exposure route, the following engineered
barriers are recognized if they prevent completion of the exposure pathway:
B) Hydraulic control of
groundwater.
d) Unless otherwise prohibited under Section
742.1100, any
other type of engineered barrier may be proposed if it will be as effective as
the options listed in subsection (c).