SECTION 350.37. Human Health Points of Exposure

(a) General. The person shall use the prescribed on-site and off-site POEs for humans to environmental media to determine PCLs under Remedy Standard A in response to §350.32 of this title (relating to Remedy Standard A) and under Remedy Standard B in response to §350.33 of this title (relating to Remedy Standard B). In order to establish on-site or off-site POEs for commercial/industrial land use, or alternate POEs for on-site or off-site properties, the person must comply with §350.111 of this title (relating to Use of Institutional Controls). Consideration of competent, existing physical controls during the pathway analysis described in §350.71(d) of this title (relating to General Requirements) does not negate or otherwise supercede the POE locations specified in this section. Subsections (b) - (k) of this section identify the media-specific prescribed, on-site and off-site POEs while subsections (l) and (m) of this section establish alternate POEs for class 2 and 3 groundwater under Remedy Standard B. When establishing on-site and off-site POEs for residential or commercial/industrial land use, persons shall use the appropriate receptor as required in §350.71(b) of this title (relating to General Requirements) for the designated land use.

(b) Air human health POEs.

(1) On-site POEs. The prescribed on-site POE to air is within the breathing zone (2 meter height) directly over the soil or groundwater COCs.

(2) Off-site POEs. The prescribed off-site POE to air is within the breathing zone (2 meter height) starting at the nearest boundary with and continuing throughout neighboring off-site properties.

(c) Soil human health POEs.

(1) On-site POEs. The prescribed on-site POE to soil is throughout the surface soil.

(2) Off-site POEs. The prescribed off-site POE to soil is throughout the surface soil starting at the nearest boundary with and continuing throughout neighboring off-site properties.

(d) Human health POEs for class 1, 2, and 3 groundwaters which do not contain any COCs in excess of the critical groundwater PCLs.

(1) On-site POE. The prescribed on-site POE is throughout the upper-most groundwater-bearing unit.

(2) Off-site POE. The prescribed off-site POE is throughout the upper-most groundwater-bearing unit on the nearest boundary with the closest hydraulically downgradient off-site property.

(e) General provisions for human health POEs for class 1, 2, or 3 groundwater.

(1) Whenever there is an existing class 1, 2, or 3 groundwater PCLE zone beneath an existing waste control unit or a waste control unit planned as part of an approved RAP, under Remedy Standard B the person may, with the executive director's approval, exclude the area underlying the waste control unit as a POE to class 1, 2, or 3 groundwater.

(2) Groundwater travel time setback distances for class 1, 2, and 3 groundwater shall be determined based on groundwater seepage velocity which is dependent upon prevailing hydraulic gradient, hydraulic conductivity, and effective porosity.

(f) Human health POEs for class 1 groundwater.

(1) On-site POEs. The prescribed on-site POE to class 1 groundwater is a well which may be completed at all locations throughout the on-site groundwater PCLE zone. For on-site commercial/industrial land use, the person shall establish an additional on-site POE for class 1 groundwater for residents unless the residential-based groundwater PCLE zone already extends off-site. The residential POE shall be set at a distance of two-year groundwater travel time upgradient of the nearest boundary with the closest hydraulically downgradient off-site property. If the residential-based groundwater PCLE zone already extends beyond the two-year groundwater travel time setback distance but not off-site, then the residential POE shall be set at the existing limit of the residential-based groundwater PCLE zone.

(2) Off-site POEs. The prescribed off-site POE to class 1 groundwater is a well which may be completed at all locations throughout an off-site groundwater PCLE zone. For off-site commercial/industrial land use, the person shall establish an additional POE for class 1 groundwater for residents at, and all locations beyond, the existing limit of the off-site residential-based groundwater PCLE zone.

(g) Human health POEs for class 2 groundwater.

(1) On-site POEs. The prescribed on-site POE to class 2 groundwater is a well which may be completed at all locations throughout the on-site groundwater PCLE zone. For on-site commercial/industrial land use, the person shall establish an additional on-site POE for class 2 groundwater for residents unless the residential-based groundwater PCLE zone already extends off-site. The residential POE shall be set at a distance of two years groundwater travel time upgradient of the nearest boundary with the closest hydraulically downgradient off-site property. If the residential-based groundwater PCLE zone already extends beyond the two-year groundwater travel time setback distance but not off-site, then the residential POE shall be set at the existing limit of the residential-based groundwater PCLE zone.

(2) Off-site POEs. The prescribed off-site POE to class 2 groundwater is a well which may be completed at all locations throughout an off-site groundwater PCLE zone. For off-site commercial/industrial land use, the person shall establish an additional POE for class 2 groundwater for residents at, and all locations beyond, the existing limit of the off-site residential-based groundwater PCLE zone.

(h) POEs for class 3 groundwater.

(1) On-site POEs. The prescribed on-site POE to class 3 groundwater is at all locations throughout an on-site groundwater PCLE zone defined by concentrations greater than ^GW GW _Class3 for the applicable on-site land use.

(2) Off-site POEs. The prescribed off-site POE to class 3 groundwater is at all locations throughout an off-site groundwater PCLE zone defined by concentrations greater than ^GW GW _{Class 3} for the applicable off-site land use which is sourced from an on-site release of COCs. If commercial/industrial land use is assumed for the off-site property, then the person shall establish an additional POE for class 3 groundwater for residents at, and all locations beyond, the existing limit of the off-site residential-based groundwater PCLE zone.

(i) POEs for surface water runoff or groundwater discharges to surface water. The prescribed POE to surface water will be at the point of surface water runoff or groundwater discharge (i.e., within the groundwater) into and throughout the extent of any on-site or off-site surface water body meeting the definition of surface water in the state as defined in §307.4 of this title (relating to General Criteria), as amended. This includes the surface water body at the initial point of entry and other water bodies that may be impacted by COCs.

(j) POEs for releases of COCs directly to surface water. The prescribed POE for releases directly to surface water is at the point of entry of COCs into and throughout the extent of any surface water body meeting the definition of surface water in the state as defined in §307.4 of this title, as amended.

(k) POEs for sediment. The prescribed POE to sediment is within the upper one-foot of sediment beneath any surface water body meeting the definition of surface water in the state as defined in §307.4 of this title, as amended. For intermittent water bodies, both sediment and surface soil POEs may apply.

(l) Alternate POEs to class 2 groundwater under Remedy Standard B. Provided the person is authorized by the executive director to establish a plume management zone in response to §350.33(f)(4) of this title (relating to Remedy Standard B), the person may establish an alternate on-site POE or off-site POE to class 2 groundwater in accordance with paragraph (1), (2), or (3) of this subsection as dictated by the particular circumstances at the affected property. The current length of the residential-based groundwater PCLE zone shall be determined as of the submittal date of the RAP.

(1) On-site POEs.

(A) The on-site POE to class 2 groundwater may be modified to be a well for residents completed at the on-site downgradient boundary of a plume management zone which includes the current length of the residential-based groundwater PCLE zone plus an additional length determined in accordance with paragraph (4) of this subsection.

(B) In the situation where multiple on-site plume management zones exist, and have commingled, or are within 500 feet of one another such that the management as a combined plume management zone is more feasible and appropriate, with site-specific approval from the executive director, the person may combine the separate plume management zones into a single, combined plume management zone provided the alternate POE for the combined plume management zone satisfies paragraph (4) of this subsection.

(2) Off-site POEs for off-site properties with class 2 groundwater which currently contains the residential-based groundwater PCLE zone. The person may establish an alternate off-site POE to class 2 groundwater as a well for residents completed at the off-site downgradient boundary of a plume management zone which includes the current length of the groundwater PCLE zone plus an additional length determined in accordance with paragraph (4) of this subsection.

(3) Off-site POEs for off-site properties with class 2 groundwater which currently do not contain the residential-based groundwater PCLE zone.

(A) If the person can demonstrate that the subject groundwater-bearing unit has no reasonably anticipated future beneficial use, then the person may allow a plume management zone to extend onto an off-site property. The person shall establish an alternate off-site POE to class 2 groundwater as a well for residents completed at the off-site boundary of a plume management zone which includes the current length of the groundwater PCLE zone plus an additional length determined in accordance with paragraph (4) of this subsection.

(B) Unless the demonstration discussed in subparagraph (A) of this paragraph is made, the person shall not allow a plume management zone within class 2 groundwater to extend onto any off-site property which does not currently contain a residential-based groundwater PCLE zone.

(C) The determination of future beneficial use under subparagraph (A) of this paragraph shall be based upon the existing quality of groundwater, considering nonpoint sources of COCs and their cumulative impact on the groundwater quality, the lack of use of the groundwater based on the presence of superior water supplies, proximity and withdrawal rates of groundwater users, or the property is subject to a zoning or governmental ordinance which is equivalent to the deed notice, VCP certificate of completion or restrictive covenant that otherwise would have been required. The executive director may require the collection of groundwater samples to document the presence of the COCs originating from nonpoint sources.

(4) The maximum additional length of the plume management zone for the situations described in paragraphs (1), (2), and (3) of this subsection shall be established as the smallest of the following applicable distances, unless the affected property is subject to zoning or a governmental ordinance which is equivalent to the deed notice, VCP certificate of completion or restrictive covenant that otherwise would have been required, in which case subparagraphs (C) and (D) of this paragraph do not apply:

(A) up to 500 feet beyond the current length of the residential-based groundwater PCLE zone;

(B) a length of up to 0.25 times the current length of the residential-based groundwater PCLE zone (i.e., up to 25% additional plume length);

(C) to within two years groundwater travel time of the closest hydraulically downgradient off-site property:

(i) for which the owner has not provided written concurrence to allow the recording of an institutional control; or

(ii) which does not contain the residential-based PCLE zone and the groundwater has a reasonably anticipated future beneficial use;

(D) at the current downgradient extent of the residential-based PCLE zone when the residential-based groundwater PCLE zone is already within the two-year travel time setback distance for POEs under subparagraph (C) of this paragraph; or

(E) the distance to a surface water POE as described in subsection (i) of this section.

(m) Alternate POEs to class 3 groundwater under Remedy Standard B. Provided the person is authorized by the executive director to establish a plume management zone in response to §350.33(f)(4) of this title (relating to Remedy Standard B), the person may establish an alternate on-site or off-site POE to class 3 groundwater. The ^GW GW _{Class 3} PCL to be applied at this alternate POE shall be based upon residential land use. The boundary of the plume management zone may be established up to the lesser of:

(1) To within two years groundwater travel time upgradient of:

(A) The closest hydraulically downgradient off-site property for which the landowner has not provided written concurrence to allow the recording of an institutional control for situations where zoning or a governmental ordinance does not serve as the institutional control; or

(B) The downgradient limit of a zoning or governmental ordinance that serves as the institutional control; or

(2) The distance to a surface water POE as described in subsection (i) of this section.

Source Note: The provisions of this §350.37 adopted to be effective September 23, 1999, 24 TexReg 7436; amended to be effective March 19, 2007, 32 TexReg 1526