[27 Pa.B. 4181]
[Continued from previous Web Page] Subchapter C. Statewide health standards
The Statewide health standard is one of the three cleanup standards available under Act 2. The Statewide health standards were developed in consultation with SAB, established by Act 2. Act 2 mandates the use of MCLs and HALs adopted by the Department and by the Federal Government by regulation or statute and mandates the development of health-based concentrations for Statewide health standards that eliminate any substantial present or probable future risk to human health and the environment. This rulemaking finalizes the health-based concentrations adopted by the Department. The MSCs included in Tables 1--4 and 6 are the concentrations that must be met in order to demonstrate attainment of a Statewide health standard, along with a screening protocol for the protection of ecological receptors.
To select the appropriate concentration from Tables 1--4, determinations must be made concerning the land use of the property, the background groundwater quality of the aquifer for total dissolved solids, depth of the soil contamination and the use or planned use of the aquifer.
On final rulemaking, the Board has chosen the use of a cancer risk factor of 1 × 10-5 for the development of soil and groundwater medium-specific concentrations. 1 × 10-5 means there is risk of one excess cancer in 100,000 in the human population. This risk factor was chosen because it falls within the risk range identified in Act 2, and it has been adopted by several other states, including California, Indiana, Massachusetts and Michigan, for use in the development of cleanup standards. Although the Statewide health standard does not take into account cumulative effects, one could have up to 10 regulated substances at a given site and, if the Statewide health standards are used, the cumulative excess cancer risk level would still not exceed the 1 in 10,000 limit of the acceptable risk range in Act 2.
The Board has not included soil and groundwater standards based on the dermal absorption route of exposure. Soils contaminated by regulated substances that meet ingestion and inhalation based standards would not pose a substantive dermal risk because of low bioavailability, low moisture content of surface soils, and short exposure periods for actual adherence of soil to the skin. For sediments, exposure is less frequent and of shorter duration than soils. For groundwater, the ingestion and inhalation standards provide adequate protection from the dermal contact route of exposure.
It cannot always be assumed that the Statewide health standards that are protective for humans will also be protective of ecological receptors. The complexity of how different substances interact with different species makes it very difficult to establish Statewide health standards protective of ecosystems in general. Therefore, an ecological screening procedure has been included to evaluate the effects of regulated substances on ecological receptors.
On final rulemaking, the section titled ''radionuclide numeric values'' and the MSCs for radionuclides in soil were deleted because the Board decided that the substances addressed by this section have not been commonly encountered in remediations in this Commonwealth. If a remediation is necessary with regard to these substances, the background or site-specific standards are available. Deletion of this section will avoid confusion with regard to the Nuclear Regulatory Commission's jurisdiction over the management of these materials.
Two new sections were added to this subchapter: ''current use and currently planned use of aquifer groundwater,'' which is located in § 250.303 (relating to aquifer determinations; current use and currently planned use of aquifer groundwater); and ''MSCs for surface water,'' which is located in § 250.309 (relating to MSCs for surface water). The subchapter was renumbered on final rulemaking and the summary which follows is based on the renumbered and retitled sections.
Section 250.301. Scope.
This section explains that the Statewide health standards are addressed in Subchapter C. References to the appropriate Tables for choosing a Statewide health standard are included. On final rulemaking, subsection (c) was added to this section to clarify that for regulated substances which do not have an MSC for the relevant medium listed on a Table, the background standard or site-specific standard must be met to qualify for a release of liability under Act 2.
Section 250.302. Point of compliance.
The points of compliance for surface water have been deleted on final rulemaking. Regulations concerning surface water have been established in a new section, § 250.309. This new section was added to implement Section 303(b)(1) of Act 2, which discusses the establishment of MSCs for any regulated discharge into surface water.
For groundwater MSCs, the point of compliance is the property boundary that existed at the time the contamination was discovered. The Statewide health standard must be attained at and beyond the point of compliance. The Department may determine, in writing, a point of compliance beyond the property boundary to be appropriate under certain specific situations. The point of compliance for soil MSCs is the concentration of the medium specific value at the depth specified in § 250.305 (relating to MSCs of soil). On final rulemaking, minor word changes were made to this section for clarification. In addition, subsection (a)(1) was deleted on final rulemaking because technology exists to meet a remediation standard at the property boundary even if the source of the contamination is at the property boundary. With the exception of the presence of secondary contaminants, the point of compliance can only be moved based on physical obstructions that prevent attainment at the property boundary.
Commentators indicated that the points of compliance should be uniform, regardless of which standard is used. It complicates the monitoring and remediation process to have different points of compliance apply to different parameters at a single site. Act 2 specifically creates a different point of compliance for the background standard by using the words ''in the area where the contamination occurs'' when describing the demonstration of attainment in section 302(b)(1) of Act 2. For the Statewide health standard and the site-specific standard, Act 2 states that a demonstration of attainment takes place at ''the point of compliance,'' which is a statutorily defined term. The differences in the points of compliance are based on the language of Act 2.
Commentators were concerned that the proposed language allowed the adjustment of the point of compliance only when SMCLs exist without the presence of other contaminants. On final rulemaking, subsection (a)(5) was modified to state that the point of compliance may be moved for measuring compliance with the groundwater MSCs that apply to secondary contaminants. ''Secondary contaminants'' is now a defined term in § 250.1.
Comments concerning the points of compliance for surface water are addressed under § 250.309.
Section 250.303. Aquifer determinations; current use and currently planned use of aquifer groundwater.
The aquifer determination section of the proposed regulations (§ 250.4), which was relocated to subsection (a) of this section, was changed substantially on final rulemaking. The proposed regulations referred to a yield of 200 gallons/day. Remediation standards applied only if a well had the specified yield and the groundwater was in an aquifer used or currently planned to be used. An inhalation exposure screen, however, was applied to groundwater that was not subject to remediation standards. On proposed, all drinking water and agricultural uses of water that existed as of the effective date of the rulemaking would have continued to be protected as ''currently used'' aquifer groundwater, regardless of the yield.
Commentators stated that the proposed yield was so low that performance of attainment in low permeability zones would be prolonged and costs associated with the cleanup would be too high with no benefit. The Department has reevaluated how to classify aquifers. The Department reviewed a United States Geological Survey field-verified groundwater site inventory and the water well inventory of the Pennsylvania Topographic and Geologic Survey. It is the Department's opinion that this Commonwealth is hydrogeologically best described as underlain by saturated unconsolidated or consolidated geologic formations, or both, or groups of formations which have the potential to yield sustainable, significant supplies of water to wells anywhere. Because of the local variability in well yield that can occur over short horizontal and vertical distances, attempting to assign a nonaquifer status to a geologic formation or subsurface interval based on the yield of one or more wells at a single site would very likely not be a valid indication of the hydrogeologic potential of the underlying formation nearby that site or well as a whole.
Commentators stated that the proposed yield was so low that it cannot be field tested and raised issues as to its potential enforceability. Demonstration of attainment will be required in all low yielding subsurface saturated intervals where they can be shown to have significant impact on the usability of the resource as a whole. The Manual will address the details for demonstrating attainment, such as placement of monitoring intervals, with the objective of providing protection to drinking water and agricultural uses of water.
Commentators indicated that water quality requirements for drinking water and for agricultural uses may be different and these differences should be recognized by the regulations. Section 303(b)(3) of Act 2 states that the MSCs for regulated substances in groundwater in aquifers used or currently planned to be used for drinking water or for agricultural purposes shall meet the MCLs or HALs established for drinking water.
The Board has decided to base the application of groundwater standards on whether the groundwater is currently used or planned to be used for drinking water or agricultural purposes, rather than on the yield of one or more wells at a specific location.
The new language for aquifer determination, in § 250.303(a), states that all geologic formations or parts of or groups of formations which are saturated are presumed to be aquifers for the purpose of applying the Statewide health standards. Geologic deposits overlying the bedrock formations which are hydrologically connected to the bedrock formations are also considered aquifers. The only groundwater that is not subject to remediation standards is seasonal, localized and hydrologically isolated perched systems under a property.
Subsections (b)--(e) replace the proposed regulation in § 250.6. On final rulemaking, the regulations were changed to indicate that groundwater in aquifers is presumed to be used or currently planned for use. In subsection (b), a person may request a determination be made by the Department that the aquifer is not used or currently planned to be used. If an aquifer is not used or currently planned for use, higher MSCs ranging from 1x to a 1,000x the MSCs may be used as alternatives to those that apply in aquifers used or currently planned for use. The methodology for these alternative MSCs and the standards can be found in § 250.304(d) and in Appendix A, Tables 1 and 2.
To qualify to use the higher MSCs for groundwater, a demonstration must be made that an aquifer is not used or currently planned to be used within the area defined as the property and a radius of 1,000 feet downgradient of the points of compliance plus any additional areas to which the contamination has migrated and might reasonably migrate at concentrations that exceed the MSC for an aquifer used or currently planned to be used. The Board recognized that an attenuation zone was needed between areas where higher nonuse aquifer MSCs would be applied and lower MSCs where aquifers are used or planned to be used would be applied. The primary purpose of the attenuation zone is to allow for time and distance before the substance reaches an area where the MSC for groundwater in an aquifer used or currently planned to be used applies. The exposure assumptions for the area defined by subsection (b) are no human ingestion and agricultural use of groundwater within the area.
To demonstrate that the aquifer is not used or currently planned to be used, subsection (c) requires that the following must be met within the area described above: 1) no groundwater derived from wells or springs is used or currently planned to be used for drinking water or agricultural purposes; 2) all downgradient properties are connected to a community water system; 3) the area described does not intersect a radius of 1/2 mile from a community water supply well source or does not intersect an area designated by the Department as a Zone 2 wellhead protection area in accordance with § 109.1. If any of the criteria is not met within the defined area, the MSC for groundwater in an aquifer used or currently planned to be used applies.
Section 250.304. MSCs for groundwater.
For groundwater in aquifers used or currently planned to be used, the MSCs are developed on the basis of the following hierarchy: 1) the use of MCLs; 2) when no MCL has been established, the use of lifetime HALs; 3) when no MCL or HAL exists, the use of the lowest concentration calculated by the equations in §§ 250.306 and 250.307 (relating to ingestion numeric values; and inhalation numeric values). Sites with groundwater that naturally exceeds 2,500 milligrams per liter for total dissolved solids may use an adjusted Statewide health standard. If this situation is occurring at a given site, the adjusted Statewide health standard shall be used as the basis for the development of a soil standard that is protective of groundwater.
A commentator stated that it is not clear what MSCs for groundwater apply if groundwater is not currently used and is restricted from future use. The final-form regulations establish MSCs for all groundwater, with a very limited exception for localized and hydrologically isolated perched systems under a property. The aquifer determination has been broadened significantly to include virtually all groundwater based upon information obtained on formations from the United States Geological Survey. Under the final-form regulations, a distinction between the use or nonuse of an aquifer and land use in the area of the release will determine which MSC for groundwater applies.
A commentator indicated that there should be residential and nonresidential MSCs where the numbers are based on MCLs or HALs, rather than just one number that applies to both. Section 303(b)(3) of Act 2 specifically states that the MSC of a regulated substance in groundwater in aquifers used or currently planned to be used for drinking water or for agricultural purposes shall comply with the MCL or HAL established for drinking water.
Commentators suggested that the vapor intrusion evaluation requirements are overly stringent because they are not limited to circumstances where vapor intrusion poses an actual risk to human health. The Board has deleted the screen from the final-form regulations, but the final-form regulations continue to protect against vapor intrusion by applying MSCs to all groundwater. Also, a solubility cap has been applied to the MSCs that will limit the formation of separate phase liquids, which are believed to be the primary cause of vapor intrusion problems.
Several changes were made to this section on final rulemaking. In subsections (b) and (e), references to a solubility limit for all groundwater MSCs were added to the text of the regulations. These references were inadvertently omitted from the proposed regulations. The numbers in Table 2 of the proposed regulations included the numerical limits.
In subsection (c), the words ''by the EPA'' were deleted because the Department may also establish MCLs under the State Safe Drinking Water Act.
A new subsection (d) was added to establish MSCs for groundwater in aquifers not used or currently planned to be used. Upon a determination under § 250.303 that an aquifer is not used or currently planned to be used, the MSCs in subsection (d) of § 250.304 may be used. In general, a natural attenuation factor was relied upon for developing the MSCs which was based on the adsorption and biodegradation processes. The MSCs are based on consideration of the organic carbon partitioning coefficient (Koc) and the first order decay coefficient (lambda). Koc and lambda were multiplied together (where data was available) to yield an attenuation factor. The product of these two factors gives an estimation of the mobility of the substances in groundwater. In the case of certain chlorinated volatile organic substances, which degrade into undesirable byproducts, the lambda was adjusted by dividing by 10. If the attenuation factor was less than 20, the MSC for groundwater in aquifers used or currently planned to be used was multiplied by 10 to yield the MSC for groundwater in aquifers not used or currently planned to be used. The attenuation factor of 20 is a reasonable cutoff to define mobility of volatile materials because it approximates where differences can be observed between categories of volatiles.
In subsection (d)(1), for volatile organic regulated substances with an attenuation factor of less than 20, the appropriate residential or nonresidential MSC is ten times the MSC for groundwater in aquifers used or currently planned to be used. In paragraph (2), for volatile organic regulated substances with an attenuation factor of greater than or equal to 20, the MSC is 100 times the appropriate residential or nonresidential MSC for groundwater in aquifers used or currently planned to be used. In paragraph (3), for semivolatile organic and inorganic regulated substances, the MSC is 1,000 times the appropriate residential or nonresidential MSC for groundwater in aquifers used or currently planned to be used, regardless of the attenuation factor. In general, the multipliers are an order of magnitude difference between categories of substances that must be supported on a site-specific basis, based on factors as soil type and groundwater flow and velocity. The multiplier for semivolatiles was based on the adsorbtive potential of the substance to soil. For benzene, the calculated attenuation factor was 19.8 and rounded off at 20, allowing a multiplier of 100. The higher multiplier is further substantiated by studies conducted by the University of Texas (R.E. Mace, et al., ''Extent, Mass and Duration of Hydrocarbon Plumes from Leaking Petroleum Storage Tank Sites in Texas,'' Geological Circular 97-1) and the California Environmental Protection Department (D.W. Rice, et al., ''California Leaking Underground Fuel Tank (LUFT) Historical Case Analyses,'' November 16, 1995), which show attenuation of benzene in plumes of petroleum releases in most cases at less than 1,000 feet. In paragraph (6), a statement was added that 5 micrograms per liter in groundwater must be used as the minimum threshold MSC for groundwater in an aquifer that is not used or currently planned for use.
The calculated MSC for groundwater in an aquifer not used or currently planned to be used is within the statutory risk range since there is no risk to humans if there are no exposure pathways (that is, no one uses the water).
Section 250.305. MSCs for soil.
Standards for soil are developed based on residential and nonresidential land uses. Along with changes in exposure factors, the depth to which the human health standards will apply varies based on land use. The standards are protective of human health through the ingestion, inhalation and volatilization routes of exposure. The standards are developed to ensure that future leaching of contaminants through soil will not exceed the groundwater standard as established in § 250.304.
To determine the depth at which the ingestion and inhalation standards apply, the Board decided that the depth should vary based on land use patterns and deed notice provisions. For residential land uses, one must remediate to the full depth of 15 feet from the existing ground surface. For nonresidential land uses, one must remediate to a depth of 2 feet from the existing ground surface, based on the lower of the ingestion or inhalation numeric value. Only the inhalation numeric value applies to the 2--15 foot depth interval.
Commentators suggested that in cases where soil contamination is located beneath a building, inhalation numeric values which consider volatilization to the indoor air should be established. In lieu of meeting a standard, indoor air sampling could be performed. The direct contact soil numbers consider inhalation health threats to a depth of 15 feet under both the residential and nonresidential standard. In addition to having the standards be protective of inhalation, the final-form regulations include a saturation cap which provides additional protection against vapor problems. The final-form regulations also include soil-to-groundwater pathway standards that apply below 15 feet and include the same saturation cap.
Commentators indicated that the proposed regulations did not provide for the severability of the soil-to-groundwater pathway numeric values from the direct contact soil standards if the person has selected to use a combination of cleanup standards. According to the commentators, current wording precludes a person from selecting the Statewide health standard for direct contact soils and a site-specific standard for soil-to-groundwater. Commentators also recommended that in cases where groundwater is not an issue, the regulations should allow persons to eliminate the application of the soil-to-groundwater pathway numeric value. Under the Statewide health standard, the soil standard includes both the direct contact and the soil-to-groundwater pathway. Section 303(b)(4) and (5) of Act 2 requires that the soil MSC not exceed either the soil-to-groundwater pathway numeric value or the direct contact value. They are not severable. However, the revisions to the soil-to-groundwater numeric values in the final-form regulations allow for greater flexibility in their application.
In subsection (b), the proposed saturation limit, which designated the physical capacity of the soil to contain a regulated substance, was retained on final rulemaking for regulated substances other than those which are organics and liquids. This limitation results in a dry soil concentration limit of 190,000 mg/kg. In effect, this physical limitation on the concentration of a regulated substance that could occur in soil was calculated to serve as an upper limit for direct contact MSCs in soil. On final rulemaking, a new saturation limit was included for regulated substances which are organics and liquids at standard temperature and pressure. For organic liquids, further limitation of the concentration beyond the 190,000 mg/kg was necessary to prevent liquids from coming out of the soil matrix, thereby causing additional exposure and risk to human health not considered by the generic assumptions used to derive the MSCs for soil. This physical limitation is based on an assumed porosity for the soil equal to 0.35, an assumed dry bulk density of soil equal to 1.8 kg/L, an assumed regulated substance density of 1.0 kg/L and an assumption of a residual saturation ratio of substance volume to soil void volume of 0.051.
In subsection (c), the word ''within'' was deleted and replaced with ''throughout the soil column'' to clarify the application of the standard. Also, the option to demonstrate a soil-to-groundwater pathway soil buffer or show a soil-to-groundwater pathway equivalency demonstration are included as alternatives to meeting the soil-to-groundwater pathway numeric value.
In subsection (d), the soil-to-groundwater pathway numeric value was inadvertently omitted on proposed for determining the nonresidential soil MSC for surface soils. On final rulemaking, this numeric pathway is included and, in addition, the option to demonstrate a soil-to-groundwater pathway soil buffer or show a soil-to-groundwater pathway equivalency demonstration are included as alternatives to meeting the soil-to-groundwater pathway numeric value. In subsection (e), the alternatives to the soil-to-groundwater pathway numeric value are also included.
A new subsection (f) is added to clarify that in all cases one of the following applies as the MSC for a regulated substance in soil at a depth greater than 15 feet: 1) the soil-to-groundwater pathway numeric value as determined by § 250.308(a); 2) the soil-to-groundwater pathway soil buffer; and 3) the soil-to-groundwater pathway equivalency demonstration.
Sections 250.306 and 250.307. Ingestion Numeric Values and Inhalation Numeric Values.
The algorithms or equations in §§ 250.306 and 250.307 are based on those presented in EPA's risk assessment guidance for the ''Superfund'' program, under the Comprehensive Environmental Response, Compensation and Liability Act, 42 United StatesC.A. §§ 9601--9675. The equations attempt to replicate how the average person is expected to come into contact with regulated substances in soil or groundwater and how the contact will impact human health. The equations include consideration of assumptions as to body weight, exposure frequency and duration, inhalation and ingestion rates and toxicity data. The protection goals of section 303 of Act 2 are built into the equations. Further discussion of the exposure assumptions used for the development of the numeric values can be found in the Preamble to the proposed regulations at 26 Pa.B. 3985. On final rulemaking, the only change to these sections is the deletion of § 250.306(d). This change was made because based on the Statewide health standards in the final-form regulations, nonaqueous phase liquids should not be present due to the saturation and solubility caps applied to the soil and groundwater standards.
A commentator indicated that the absorption rate of 1.0 in the default exposure assumptions should be modified to include actual absorption values readily available for regulated substances. For the purpose of developing generic assumptions, the absorption value of 1 was chosen. Values are currently not available for all compounds.
A commentator stated that the Department used invalid models to derive the soil MSC for lead since EPA's IEUBK model has been updated several times and the Department has not used the most updated model. In addition, the Department should adopt a preliminarily promulgated standard by EPA under the Toxic Substances Control Act (TSCA) or adopt a standard not less than 5,000 mg/kg. The final-form regulations are based on two state-of-the-art models for estimation of MSCs for lead in residential and nonresidential soils. Although more recent versions of EPA's IEUBK model have been developed, the use of the most recent version would result in a residential MSC for lead that is lower than the 500 mg/kg level. The TSCA notice in the Federal Register, September 11, 1995, recommends a range of lead concentrations in soil of 400 mg/kg to 5,000 mg/kg. The notice also includes recommendations for interim controls to reduce exposure of children to contaminated soil within that range. Under the final-form regulations, the Statewide health standards fall within the range identified in the EPA notice. In addition, exceedance of the 500 mg/kg residential soil MSC is not precluded under the site-specific standard. The interim controls identified in the EPA notice could be used under the site-specific standard in conjunction with a lead concentration in soil that is higher than 500 mg/kg.
Section 250.308. Soil-to-groundwater pathway numeric values.
The statute provides three options for the development of soil-to-groundwater pathway numeric values. Values in Appendix A, Tables 3 and 4, include concentrations developed using the following: 1) a concentration which is 100 times the MSC for groundwater; and 2) a concentration developed using an equilibrium partitioning method which would be protective of the MSC for groundwater. As a third option, the person remediating may use the Synthetic Precipitation Leaching Procedure in order to determine a level which would not produce a leachate in excess of the MSC for groundwater.
Commentators stated that the proposed soil-to-groundwater numeric values were too stringent, that the values should not apply when groundwater is not a medium of concern and that the methods used to calculate them are inappropriate. Based upon the many comments received, the method of calculating the soil-to-groundwater numeric values has been revised to provide for more achievable standards. The default dilution factor for unsaturated soils has been increased to 100 for all regulated substances. This value is less stringent than the EPA's default value of 10 in its Soil Screening Guidance. In addition, the calculation of these numeric values is linked to the appropriate residential or nonresidential groundwater MSC. To provide additional flexibility for meeting the soil-to-groundwater pathway requirement, the final-form regulations include a soil buffer option and an equivalency demonstration option as alternatives to meeting the numeric value.
Commentators also suggested that the soil-to-groundwater numeric values may be calculated for metals by substituting Kd values, as calculated in the EPA Soil Screening Guidance, for the Koc*foc term in the soil-to-groundwater equation. This suggestion has been incorporated into the final-form regulations.
In subsection (a)(3), the dilution factor was changed from one that varied based on the organic carbon partition coefficient for that substance and based on whether the soils were saturated or unsaturated to a default value of 100 for all substances. This change was made because it is more relevant to use the same dilution factor for all compounds.
In subsection (a)(4), the equilibrium partitioning coefficient method is applied to inorganic compounds. This methodology is used by the EPA in its Soil Screening Guidance. The difference between the application of this method to organic and inorganic compounds is that the fraction of organic carbon does not control the partitioning of inorganic compounds.
In subsections (b)--(d), demonstrations of equivalency can be made to show that groundwater will be protected. The demonstrations are available as substitutions for meeting the protectiveness of the soil-to-groundwater numeric values.
Subsections (b) and (c) provide a method for determining soil buffer zone thicknesses for some regulated substances which would ensure protection of groundwater even for levels in soil that exceed the soil-to-groundwater pathway numeric values for these regulated substances. The estimation of buffer zone thicknesses is based on the same equations and coefficients used for the development of the soil-to-groundwater numeric values. In the estimation of the buffer zone thicknesses, five different partition coefficients have been used. Each coefficient is used to represent the lower end of a range of coefficients. Regulated substances which possess partition coefficients which fall within a given range are assigned the buffer distance estimated from the coefficient used to represent that range. This accounts for five different buffer zone thicknesses: 30 feet for each regulated substance with a partition coefficient between 2.5 and 5; 20 feet for each regulated substance with a partition coefficient between 5 and 10; 15 feet for each regulated substance with a partition coefficient between 10 and 100; 10 feet for each regulated substance with a partition coefficient between 100 and 1,000; and 5 feet for each regulated substance with a partition coefficient exceeding 1,000. In determining the buffer zone thicknesses, the distance that the regulated substance travels over a period of 30 years in the soil column at a concentration of 1 part per billion or greater in soil pore water has been estimated. This estimation was then determined to be the approximate buffer zone thickness.
Subsection (d) provides the option of an equivalency demonstration to meet the protectiveness of the soil-to-groundwater pathway numeric value. To qualify to use this option, a person must first demonstrate that groundwater directly beneath the area of soil contamination does not exceed background or Statewide health MSCs prior to remediation. If a person demonstrates attainment with the direct contact soil standard, a demonstration may be made, by use of a fate and transport analysis, that groundwater is protected. Site specific data collected during the site characterization must be applied to the analysis. In addition, the analysis must demonstrate that the residual contamination will attenuate or stabilize over a period of 30 years and not cause an elevation of contaminant concentration in the groundwater above the MSC or the background standard, whichever is highest. Reporting and monitoring for eight quarters is required to show no exceedances of groundwater MSCs or the background standard for groundwater beneath the contaminated soil and to show no indications of an increasing trend of concentration over time that may exceed the standard.
Section 250.309. MSCs for surface water.
The proposed regulations identified points of compliance for surface water in § 250.302. Act 2 provides that for any regulated discharge into surface water, compliance with applicable laws and regulations relating to surface water discharges must be used to establish the MSCs for surface water. Therefore, a new section was developed on final rulemaking for MSCs for surface water.
A commentator stated that the potential for diffuse groundwater discharges to impact surface water bodies should be assessed using concentrations of regulated substances attributable solely to the site. The final-form regulations have been revised to include language that limits the determination of the expected instream concentrations of regulated substances to the concentrations attributable to releases at the site.
A commentator questioned the appropriateness of establishing the point of compliance for a spring where it is discharged from the ground. On final rulemaking, except where an NPDES permit is required, compliance with surface water quality standards in a spring must be measured at the point of first designated or existing use, as defined in §§ 93.1, 93.4 and 93.9 (relating to scope; Statewide water uses; and designated water uses and water quality criteria). When the point of first designated or existing use occurs in a surface water into which a spring flows, compliance with surface water quality standards must be determined in the same manner as required for diffuse discharges.
Commentators indicated that proposed § 250.302(b)(3) was too restrictive by not allowing the point of compliance to be moved if a site involves contaminants other than those identified as secondary contaminants. On final rulemaking, the word ''only'' was deleted in subsection (b)(5). While other contaminants may be present at a site, the point of compliance may be moved for substances that are secondary contaminants.
The final-form regulations, in subsection (a), require that any regulated discharge to surface water must comply with the applicable provisions of Chapters 91--105, including the antidegradation requirements.
Subsection (b) requires compliance with an NPDES permit for point source discharges to surface water. This requirement was in the proposed rulemaking in § 250.302(d)(1).
Subsection (c) is similar to the requirement proposed in § 250.302(d)(2). On final rulemaking, the regulations require a person to determine the expected instream regulated substance concentrations that are attributable to the site. If mass balance techniques indicate that instream surface water quality standards are not met, then the person has an opportunity to conduct sampling. If sampling indicates that the standards are being met, there is no requirement for further remediation. If the results of the modeling, and sampling if any, indicate that surface water quality standards are not being met, further remediation will be required.
In subsection (d), except where an NPDES is required, compliance with surface water quality standards in a spring must be measured at the point of first designated or existing use, as defined in §§ 93.1, 93.4 and 93.9.
Section 250.310. Minimum threshold MSCs.
This section provides cleanup standards for regulated substances where no toxicological data is available for the substances. The numbers are based solely on ingestion. After considering the United States Food and Drug Administration's final rule, Threshold of Regulation for Substances Used in Food-Contact Articles (Federal Register, Vol. 60, No. 136, July 17, 1995, pp. 36582-36596) and back-calculating the threshold numbers derived from the regulations to cleanup standards at 1 × 10-5 risk level, Statewide health standards were developed for regulated substances where no toxicological data exists. Further information regarding the development of the minimum threshold MSCs can be found at 26 Pa.B. 3991.
The minimum threshold MSCs may be used only when no toxicological data is available for the regulated substance. Under Act 2, the Department may require additional remediation for the regulated substances that meet a minimum threshold MSC if new chemical-specific toxicological information is obtained which revises the exposure assumptions beyond the acceptable risk.
Commentators indicated that by requiring the use of the lowest of the ingestion numeric value or the soil-to-groundwater pathway numeric value, the minimum threshold numeric value would not be used because the soil-to-groundwater value is significantly more restrictive. Section 303(b)(4) of Act 2 states that an MSC for soil shall not exceed either the direct contact soil MSC or the soil-to-groundwater pathway numeric value. Alternatives to the numeric value for protecting groundwater through the soil-to-groundwater pathway, which are not as restrictive, have been included in the final rulemaking at § 250.308.
On final rulemaking, language was added to subsection (c)(1) that requires the soil-to-groundwater pathway value to be calculated by either using a concentration in soil at the site which does not produce a leachate in excess of the MSC for groundwater or by using a value which is 100 times the MSC for groundwater, expressed in milligrams per kilogram of soil. An equivalency demonstration under § 250.308(d) may be substituted for the soil-to-groundwater numeric value. This new language was added to explain which soil-to-groundwater protection methodologies can be used for regulated substances which have no KOC values. Also, proposed subsection (c) was deleted. Since the ecological screen applies to all MSCs, it was not necessary to repeat that requirement here.
Section 250.311. Evaluation of ecological receptors.
SAB and the Department were unable to identify a method to develop generic Statewide health standards that are protective of ecological receptors to cover the effects of all combinations of species and substances. On final rulemaking, the Board adopted a screening protocol for identification of ecological receptors of concern. A person conducting a remediation under the Statewide health standard must address those receptors that are identified for protection at the end of the screening process.
Commentators stated that Act 2 does not authorize the Department to require the evaluation of ecological receptors, or if it does, the evaluation should only apply to sites remediated under the site-specific standard. Section 301(a)(2) of Act 2 requires that a Statewide health standard be adopted by the Board which achieves a uniform Statewide health-based level so that any substantial present or future risk to human health and the environment is eliminated.
Commentators recommended that the identification of receptors should be better defined. The final-form regulations include new definitions for ''species of concern'' and ''habitats of concern.''
Commentators suggested that the requirements of the screening process are complex, burdensome and costly. The screen takes into account several circumstances that will not require an ecological evaluation. Therefore, the number of sites that will require more thorough evaluation and some type of activity to address impacts will be minimal. In addition, the cost of collecting appropriate data for the screen should be minimal, as most of the necessary data will be collected as part of the site characterization activities. On final rulemaking, the screen has been substantially modified to identify only the most important steps of the screening process. Any additional explanatory details needed will be included in the Manual.
Commentators stated that the first step of the screen, the exemption for sites contaminated only with certain types of petroleum products, is inappropriate. This step was included based on the SAB's recommendation that a cleanup to the Statewide health standards identified for those regulated substances would be protective of the environment. The substances listed in this step of the screen are limited to a subset of petroleum products for which the chemical makeup and concentrations can be reliably predicted.
Commentators indicated that sites without constituents of potential ecological concern (CPECs) should not be required to undergo further evaluation. Sites contaminated with substances other than CPECs, such as petroleum hydrocarbons, may cause direct impacts from physical stress.
The ecological receptors screening procedure was substantially revised on final rulemaking. Many of the screening steps have been renumbered. In some cases, small word changes were made to clarify or simplify a concept.
In subsection (a), the list of ecological receptors to be evaluated was revised to delete paragraph (2), individuals of species of special concern as identified by the Game Commission and the Fish and Boat Commission, because these species are now included within the definition of ''species of concern.''
In subsection (b), the procedures were revised to include an additional circumstance for determining that no ecological evaluation is required. The final-form regulations state that no additional evaluation is required if the remediation attains a level equal to 1/10 of the value in Tables 3 and 4, if the regulated substance in question is not a CPEC. (This value is equal to the 1 × 10-6 cancer risk level for humans.) It is the expectation of the Department that the lower human cancer risk level will temporarily serve as a margin of safety to protect ecological receptors until SAB is able to study ecological protection more thoroughly and recommend appropriate standards that are protective of ecological receptors. In subsection (b)(1), the reference to ''no nonaqueous phase liquids are present'' was deleted because based on the the soil saturation limit in the Statewide health standards, nonaqueous phase liquids are not expected to be present at those levels.
In subsection (e), if ecological impacts are identified from the screening process that must be addressed, a person must do one of the following: 1) demonstrate that attainment of the Statewide health standard MSCs are protective of the ecological receptors; 2) if it cannot be shown that the Statewide health standard MSCs are protective, demonstrate that the postremedy use will eliminate complete exposure pathways at the time of the final report or in accordance with a postremediation care plan, or that mitigative measures have been instituted and are subject to postremediation care plan requirements; 3) demonstrate attainment of the background standard; or 4) follow the procedures in §§ 250.402(c) and 250.409 (relating to human health and environmental protection goals; and risk assessment report) and demonstrate attainment with the site-specific standard. On final rulemaking, subsection (f) specifies the requirements that must be met if a person performs mitigation to address the ecological impacts.
Section 250.312. Final report.
Under the Statewide health standard, the final report is the only report that must be submitted to and approved by the Department. The final report must document the site investigation activities including all laboratory results, the remediation activities, the demonstration of attainment of the standard and any postremediation activities, such as engineering or institutional controls, that are necessary to maintain attainment. The final report must also include information supporting the use of residential or nonresidential standards.
The final-form regulations contain several revisions. Subsection (a) contains a number of revisions for clarification. In subsection (b), there are new final report requirements where mitigation measures are used for protection of ecological receptors. There is a new subsection (d) which explains the types of information that must be submitted in a final report with respect to a demonstration of attainment. Subsection (e) identifies additional circumstances where a postremediation care plan must be documented in a final report. New subsections (f) and (g) contain additional final report requirements where soil-to-groundwater pathway buffer distances or an equivalency demonstration is used. New subsection (h) provides that documentation of access to property owned by a third party must be included as part of a final report when needed for remediation or monitoring.
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