| (B) When the concentration of a COC in groundwater at the zone of discharge to surface water exceeds the SW SW for that COC at the time the affected property assessment required in §350.51 of this title is conducted, the person may establish a surface water dilution factor in accordance with subparagraph (C), (D), or (E) of this paragraph. (C) The person may use a surface water dilution factor of 0.15 for non-flowing surface waters such as lakes, estuaries, tidal rivers; and fresh water streams and rivers (where the groundwater discharge is clearly less than 15% of the 7Q2 stream flow as defined in §307.3(a)(34) of this title (relating to Definitions and Abbreviations)), as amended. The person shall use the 7Q2 flows as listed in §307.10(2) of this title (relating to Appendices A - E), as amended, for groundwater discharges directly to a classified segment as listed in §307.10(3) of this title, as amended. For groundwater discharges which are not directly to a classified segment, site-specific 7Q2 values must be determined for the water body directly receiving the groundwater discharge. (D) For freshwater streams and rivers where the groundwater discharge is clearly greater than 15% of the 7Q2 flow, the person shall estimate property-specific surface water dilution factors based on 7Q2 flows for chronic aquatic-life criteria, 25% of 7Q2 flows for acute aquatic-life criteria, and harmonic mean flows as defined in §307.3(a)(19) of this title, as amended, for human health criteria in accordance with the procedures contained in the Implementation Procedures, as amended. The person shall divide the SW SW by the estimated property-specific dilution factor. The person shall use the 7Q2 flows listed in §307.10(2) of this title, as amended, for groundwater discharges directly to a classified segment as listed in §307.10(3) of this title, as amended. For groundwater discharges which are not directly to a classified segment, site-specific 7Q2 values must be determined for the water body directly receiving the groundwater discharge. (E) As an alternative to using the dilution factor of 0.15 as specified in subparagraph (C) of this paragraph, the person may measure and/or estimate the groundwater dilution in surface water from appropriate models of groundwater plume dispersion, tracer studies, receiving water and sediment sample analyses, analytical calculations, or other techniques upon the executive director's approval using site-specific base flow conditions for groundwater, 7Q2 conditions for receiving streams, and critical mixing conditions for lakes, estuaries, and tidal streams. The executive director may require a receiving water study to ensure that benthic communities in the sediment are not adversely impacted. In cases where groundwater COCs include bioaccumulative COCs, the executive director may require a receiving water study or empirical analysis to ensure that the release of that particular COC is not causing, or will not result in harmful levels in the tissue of aquatic and terrestrial organisms that feed in the water body. (F) The person may be required by the executive director to take appropriate action to ensure that discharging groundwater plumes do not result in exceedances of surface water quality standards in significant areas of the potentially affected surface water body. (5) PCLs for other complete or reasonably anticipated to be completed groundwater exposure pathways. The person shall establish PCLs for exposure pathways other than those listed in paragraphs (1) - (4) of this subsection when, in the executive director's determination, those other exposure pathways are complete or reasonably anticipated to be completed. (6) PCLs for the combined exposure pathways of inhalation of volatile emissions and particulates from COCs in surface soil, dermal contact with COCs in surface soil, ingestion of COCs in surface soil, and for affected residential properties, ingestion of aboveground and below-ground vegetables grown in surface soil containing COCs (Tot Soilcomb ). The person shall establish this PCL using the applicable equation as shown in the figure in subsection (b)(1) of this section for Tier 1. (7) PCLs for groundwater protection from leachate containing COCs from surface and subsurface soil (GW Soil). (A) The person shall establish GW Soil for each COC present in the surface and subsurface soil such that soil leachate is protective for: (i) the critical groundwater PCL established in §350.78 of this title (relating to Determination of Critical Protective Concentration Levels) when the use of a plume management zone is not authorized in §350.33(f)(4) of this title (relating to Remedy Standard B); (ii) the attenuation action level for the nearest monitoring point when the use of a plume management zone is authorized under §350.33(f)(4) of this title; and/or (iii) the maximum concentration of COCs in the groundwater source area at the time of RAP submittal when a plume management zone is authorized for class 2 groundwater in response to §350.33(f)(4) of this title. (B) The person shall establish this PCL using the applicable equations as shown in the figure in subsection (b)(1) of this section for Tier 1. (C) The person may not be required to establish a soil leachate-to-groundwater PCL in accordance with subparagraphs (A) and (B) of this paragraph when a demonstration can be made with appropriate soil and groundwater monitoring data that the soils will attain the soil response objectives for groundwater protection set forth in Subchapter B of this chapter (relating to Remedy Standards). The determination that the soils are adequately protective shall be based on soil sample data, the concentration trends of groundwater monitoring data over time when groundwater is impacted, probable time since release occurred, adequate identification of the soil source areas, appropriate leachate test results, or other hydrogeologic or property-specific information. The executive director may also require that the change in soil concentrations over time be documented to support this evaluation in a property-specific situation. The executive director may require the person to install a sufficient number of groundwater monitoring wells to demonstrate that groundwater is not affected when soil COC concentration data are inadequate to sufficiently substantiate that groundwater is not affected. (8) PCLs for inhalation of volatile emissions in outdoor air from COCs in subsurface soils (Air Soil Inh-V ). The person shall establish this PCL using the applicable equations as shown in the figure in subsection (b)(1) of this section for Tier 1. (9) Theoretical soil saturation limit (C sat ). The person may establish a property-specific theoretical soil saturation limit for the volatilization exposure pathways required in paragraphs (6) and (8) of this subsection under Tiers 2 or 3. The C sat shall be based on the same property-specific parameters as those used to calculate Air Soil Inh-V . If the property-specific Air SoilInh-VP or Air SoilInh-V is greater than the property-specific Csat , then that exposure pathway shall not be considered a relevant exposure pathway for that COC. (10) Residual soil saturation limit (Soil Res ). The person shall establish the residual saturation level for each organic COC present in surface and subsurface soils which is a liquid at standard temperature and pressure using the applicable equation as shown in the figure in subsection (b)(1) of this section to estimate the mobile NAPL concentration and to determine if NAPL may be present. (11) PCLs for other complete or reasonably anticipated to be completed surface and subsurface soil exposure pathways. The person shall establish PCLs for surface and subsurface soil exposure pathways other than those listed in paragraphs (6) - (8) of this subsection when, in the executive director's determination, those other exposure pathways are complete or reasonably anticipated to be completed. (12) Air inhalation exposure pathways ( Air AirInh ). For air inhalation exposure pathways, the person may be required by the executive director to establish Air AirInh solely for the purposes of determining the protective concentration that must be met in air at the POE. The person shall use the applicable equation as shown in the figure in subsection (b)(1) of this section to establish Air AirInh . (13) Surface water exposure pathways ( SW SW). The person may be required by the executive director to establish SW SW when COCs are present in surface water or when COCs will enter into surface water due to a release, and a surface water response action is necessary to protect human or ecological receptors. The person shall use the applicable equation as shown in the figure in subsection (b)(1) of this section to establish SW SW. (14) Other air and surface water exposure pathways. The person shall establish PCLs for air and surface water exposure pathways other than those listed in paragraphs (12) and (13) of this subsection when, in the executive director's determination, those other exposure pathways are complete or reasonably anticipated to be completed. (15) The person shall establish PCLs for complete or reasonably anticipated to be completed sediment exposure pathways when, in the executive director's determination, those exposure pathways are complete or reasonably anticipated to be completed. (j) The person is not required to combine exposure pathways for a single environmental medium when determining PCLs with the exception of the combined exposure pathway required in subsection (i)(6) of this section, unless otherwise directed by the executive director. |
