(a) For each individual COC for which PCLs have been developed
in response to §350.71(k) of this title (relating to General Requirements),
the person shall establish the critical PCL. The critical PCL is the lowest
PCL for a particular environmental medium considering all the exposure pathways
for which a PCL is developed in accordance with §350.75(i) of this title
(relating to Tiered Human Health Protective Concentration Level Evaluation)
and/or §350.77 of this title (relating to Ecological Risk Assessment
and Development of Ecological Protective Concentration Levels).
(b) If the critical groundwater PCL, or an attenuation action
level developed in accordance with §350.33(f) of this title (relating
to Remedy Standard B), is greater than the aqueous solubility limit for that
COC, then the COC should be addressed as NAPL should any NAPLs be present.
(c) If the critical PCL for a COC established in subsection
(a) of this section is less than the method quantitation limit as defined
in §350.4 of this title (relating to Definitions and Acronyms) or background
concentration for that COC as determined in accordance with §350.51(l)
and (m) of this title (relating to Affected Property Assessment), then the
greater of the method quantitation limit or background concentration is the
critical PCL for that COC.
(d) As an additional requirement, the critical PCL and any
attenuation action level must ensure that the explosive vapor provisions set
forth in §350.31(c) of this title (relating to General Requirements for
Remedy Standards) are met.
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