Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 350 - TEXAS RISK REDUCTION PROGRAM › Subchapter C - AFFECTED PROPERTY ASSESSMENT › Section 350.51 - Affected Property Assessment

Current through Reg. 49, No. 28; July 12, 2024
(a)
				  The person shall conduct an affected property assessment in a manner
				  appropriate for the affected property considering the hydrogeology, physical
				  and chemical properties of the COCs, location of human and ecological
				  receptors, and the complete or reasonably anticipated to be completed exposure
				  pathways identified in §
										350.71 of
				  this title (relating to General Requirements). The assessment shall be designed
				  to collect information necessary to support notification of affected landowners
				  and remedy selection, determine whether or not water resources have been
				  affected or are threatened, and may also evaluate the effectiveness of existing
				  physical controls. Additionally, when existing physical controls will be used
				  as part of the response action in accordance with Remedy Standard B, then the
				  assessment may be conducted such that the primary focus is placed beyond the
				  limits of the existing physical control in order to reduce the degree of
				  assessment within the limits of the physical control. The assessment shall be
				  conducted in a manner most likely to detect the presence and distribution of
				  COCs above the concentration levels defined in subsections (b) - (e) of this
				  section considering the nature of the release and subsequent modifications to
				  the affected property (e.g., judgmental samples in hot spots, stratified random
				  sampling, systematic grid, etc.), and shall use appropriate quality
				  assurance/quality control. The geology and hydrogeology of the affected
				  property shall be adequately characterized, such that COC fate and transport
				  can be reliably predicted in order to confidently locate existing environmental
				  media containing COCs above the concentration levels defined in subsections (b)
				  - (e) of this section and an appropriate response action can be designed. The
				  person shall use sample collection techniques that meet the data quality needs
				  and are acceptable to the executive director. The results of the assessment
				  shall be documented in an Affected Property Assessment Report in accordance
				  with §
										350.91
				  of this title (relating to Affected Property Assessment Report). The person
				  shall conduct an assessment in a manner which is timely considering the size
				  and complexity of the situation, and shall comply with an assessment schedule
				  established in any commission rule, order, or permit, or any assessment
				  schedule approved by the executive director.
(b) The person shall perform an affected
				  property assessment through the collection and analysis of a sufficient number
				  of samples from environmental media to reliably characterize the nature and
				  degree of COCs in the source area(s), as well as the horizontal and vertical
				  extent of COCs in soil and groundwater, which equals or exceeds the applicable
				  concentration of COCs as specified in subsections (c), (d) and (e) of this
				  section, unless the executive director determines on a site-specific basis that
				  additional assessment of the extent of COCs is necessary to evaluate a
				  potential threat to human health and the environment. Information obtained from
				  attempts to attain Remedy Standard A may be submitted for this purpose. The
				  person shall characterize the nature, degree and extent of COCs in other
				  environmental media as required by the executive director in consideration of
				  property-specific factors. The executive director may require the person to
				  determine the concentrations of COCs in outdoor or indoor air on a
				  property-specific basis.
(c) The
				  person shall demonstrate that all COCs in environmental media (except for
				  on-site soils as noted below) which exceed the residential assessment level
				  have been characterized horizontally in all directions. If the assessment level
				  is based upon background concentrations, then the assessment shall only extend
				  to the background concentration level. For soils only, the person can focus the
				  horizontal on-site assessment to define the area exceeding the applicable
				  critical PCL (i.e., residential or commercial/industrial). However, the person
				  shall investigate environmental media, including soils, using adequate on-site
				  or off-site data to determine whether off-site properties have been affected
				  with concentrations of COCs which exceed the residential assessment levels. The
				  requirement to use an assessment level based upon a residential receptor (i.e.,
				  residential assessment level) pertains to all off-site properties (i.e., both
				  residential and commercial/industrial land use).
(d) For the vertical soil assessment to
				  adequately determine if groundwater has been or will be affected, the person
				  shall complete the requirements of paragraph (1), (2), (3) or (4) of this
				  subsection.
(1) The person shall demonstrate
				  that the vertical limit of COCs in soil which exceed the higher of the method
				  quantitation limit or background concentrations has been characterized. If the
				  person satisfactorily demonstrates that all reasonably available analytical
				  technology has been used to show that the COC cannot be measured to the method
				  quantitation limit due to sample specific interferences, then the sample
				  detection limit may be used in lieu of the method quantitation limit.
(2) If an adequate groundwater assessment has
				  been conducted (i.e., COC concentrations in groundwater have been measured from
				  appropriate locations), then the person shall characterize the vertical limits
				  of COCs in soil which exceed the residential assessment level. The 
				  GW Soil PCL may not be applicable in
				  the determination of the residential assessment level if the person has
				  conducted an adequate groundwater assessment and can meet the requirements of
				  §
											350.75(i)(7)(C)
				  of this title (relating to Tiered Human Health Protective Concentration Level
				  Evaluation). The executive director may omit or modify the requirement for a
				  groundwater assessment under this paragraph for use of §
											350.75(i)(7)(C)
				  of this title on a site-specific determination based upon a combination of
				  supporting evidence including, but not necessarily limited to, probable depth
				  to groundwater, presence of soils or bedrock that prohibit or impede vertical
				  migration of COCs, and physical and chemical properties of the COCs.
(3) If the uppermost groundwater-bearing unit
				  is encountered before the vertical limit of COCs is determined to the higher of
				  the method quantitation limit or background concentrations, then representative
				  groundwater samples (i.e., a groundwater sample does not have to be collected
				  from each boring) must be collected to evaluate potential groundwater impacts.
				  The vertical extent of the soil assessment shall continue beyond the uppermost
				  groundwater-bearing unit as appropriate based on the likelihood that COCs have
				  migrated deeper considering the chemical and physical properties of the COCs
				  (e.g., dense non-aqueous phase liquids) and the hydrogeology of the affected
				  property. The executive director may omit or modify this requirement on a
				  site-specific basis if the vertical assessment would exacerbate the vertical
				  migration of COCs.
(4) If a person
				  has already determined that the groundwater is impacted, then they may satisfy
				  the requirements of this subsection by declaring the entire soil column to the
				  top of the lowest impacted groundwater bearing unit as a soil PCLE
				  zone.