| (A) use either an active restoration approach or monitored natural attenuation (if appropriate considering the hydrogeologic characteristics of the affected property, chemical-specific data for the COCs, and whether the anticipated time frame to achieve the critical groundwater PCLs is reasonable) to reduce the concentration of COCs to the critical groundwater PCLs throughout the groundwater PCLE zone; (B) while achieving subparagraph (A) of this paragraph, prevent COCs at concentrations above the critical groundwater PCLs from migrating beyond the existing boundary of the groundwater PCLE zone; (C) prevent COCs from migrating to air at concentration levels above the PCLs for air (i.e., Air Air Inh ); (D) prevent COCs from migrating to surface water at concentration levels above the PCLs for groundwater discharges to surface water (i.e., SW GW); and (E) prevent human and ecological receptor exposure to the groundwater PCLE zone. (2) Waste control unit. When the approved RAP includes an existing or planned waste control unit which overlies an existing groundwater PCLE zone, the person may, with the executive director's approval, exclude the groundwater throughout that portion of the groundwater PCLE zone directly underlying the waste control unit from the requirement to meet the groundwater response objectives provided in paragraph (1) of this subsection. To use this approach, the person shall comply with the institutional control requirements in §350.31(g) of this title (relating to General Requirements for Remedy Standards), with the exception that proof of compliance with the institutional control requirements must be submitted to the executive director within 120 days of approval of the RAP, which provides notice of the existence and location of the groundwater PCLE zone beneath the waste control unit and which prevents usage of and exposure to this groundwater until such time as the COCs may reduce to the critical groundwater PCLs. Beyond the perimeter of the waste control unit, the groundwater response objectives must be met. (3) Technical impracticability. A technical impracticability demonstration can be used for all three classes of groundwater under Remedy Standard B. To use this approach, the person must: (A) demonstrate in accordance with the United States Environmental Protection Agency (EPA) "Guidance for Evaluating the Technical Impracticability of Ground-Water Restoration" (Office of Solid Waste and Emergency Response Directive 9234.2-25 or subsequent version), as amended, or other method approved by the executive director, that it is not feasible from a physical perspective using currently available remediation technologies due either to hydrogeologic or chemical-specific factors to reduce the concentration of COCs throughout all or a portion of the groundwater PCLE zone to the applicable critical groundwater PCLs within a reasonable time frame; (B) use removal or decontamination actions to reduce the concentrations of COCs to the critical groundwater PCLs for any portion of the groundwater PCLE zone for which it is technically practicable; (C) prevent migration of COCs from that portion of the groundwater PCLE zone which satisfies the technical impracticability demonstration in subparagraph (A) of this paragraph; (D) achieve the performance criteria in subsection (f)(4)(E) of this section for NAPLs; (E) establish a plume management zone for the area where COCs cannot be removed so as to attain the critical PCLs, and prevent COCs at concentrations above the critical groundwater PCLs from spreading beyond the existing boundary of the groundwater PCLE zone; and (F) comply with the institutional control requirements in §350.31(g) of this title (relating to General Requirements for Remedy Standards), with the exception that proof of compliance with the institutional control requirements must be submitted to the executive director within 120 days of the approval of the RAP, which provides notice of the existence and location of the groundwater PCLE zone and which prevents usage of and exposure to groundwater from this zone until such time as the COCs may reduce to the critical groundwater PCLs. (4) Plume management zones. With the approval of the executive director, the person may use a plume management zone under Remedy Standard B for class 2 and 3 groundwater-bearing units which presently contain a groundwater PCLE zone. (A) To use a plume management zone, the person must demonstrate that the COCs will not pose a substantial present or potential hazard to human health or the environment as long as the attenuation action levels are not exceeded at the respective attenuation monitoring points based upon a consideration of the following factors: (i) potentially adverse effects on groundwater quality, considering: (I) the physical and chemical characteristics of the COC, including its potential for migration; (II) the hydrogeological characteristics of the affected property and surrounding land; (III) the quantity of groundwater and the direction of groundwater flow; (IV) the proximity and withdrawal rates of groundwater users; (V) the current and future uses of groundwater in the area; (VI) the existing quality of groundwater, including other sources of COCs and their cumulative impact on the groundwater quality; (VII) the potential for health risks caused by human exposure to COCs; (VIII) the potential damage to wildlife, crops, vegetation, and physical structures caused by exposure to COCs; (IX) the persistence and permanence of the potentially adverse effects; and (ii) potentially adverse effects on hydraulically-connected surface water quality, considering: (I) the volume and physical and chemical characteristics of the COCs present at the affected property; (II) the hydrogeological characteristics of the affected property and surrounding land; (III) the quantity and quality of groundwater, and the direction of groundwater flow; (IV) the patterns of rainfall in the region; (V) the proximity of the source area to surface water; (VI) the current and future uses of surface waters in the area and any water quality standards established for these surface waters; (VII) the existing quality of surface water, including other sources of COCs and their cumulative impact on surface-water quality; (VIII) the potential for health risks caused by human exposure to COCs; (IX) the potential damage to wildlife, crops, vegetation, and physical structures caused by exposure to COCs; and (X) the persistence and permanence of the potentially adverse effects. (B) Provided the person demonstrates that the establishment of a plume management zone is appropriate, the POE to groundwater may be changed from throughout the groundwater PCLE zone to an alternate location established in accordance with §350.37(l) or (m) of this title (relating to Human Health Points of Exposure) as applicable, or at the POE for ecological receptors determined in accordance with §350.77 of this title (relating to Ecological Risk Assessment and Development of Ecological Protective Concentration Levels), where that location is more restrictive. (C) In order to establish a plume management zone, the person must: (i) comply with the institutional control requirements in §350.31(g) of this title, with the exception that proof of compliance with the institutional control requirements shall be submitted to the executive director within 120 days of the approval of the RAP, which provides notice of the existence and location of the plume management zone and which prevents exposure to groundwater from this zone until such time as COCs may reduce to the critical groundwater PCLs; (ii) demonstrate through an appropriate technical presentation that COCs will not migrate beyond the downgradient boundary of the plume management zone at concentrations above the critical groundwater PCLs; and (iii) demonstrate through the performance of a field survey in the plume management zone that there are no artificial penetrations (e.g., abandoned wells or wells with open-hole completions) which can allow COCs at concentrations which exceed the critical groundwater PCLs to migrate from the groundwater PCLE zone to currently unaffected groundwater-bearing units. (D) The person shall establish groundwater attenuation monitoring points beginning at an appropriate hydraulically upgradient location within the groundwater PCLE zone and continuing down the approximate central flow path of the COCs to the downgradient extent of the plume management zone. Cont'd... |
