PETITIONED PUBLIC HEALTH ASSESSMENT
ATLANTA GAS LIGHT COMPANY
AUGUSTA, RICHMOND COUNTY, GEORGIA
ATSDR comparison values are media-specific concentrations that are considered to be "safe" under default conditions of exposure. They are used as screening values in the preliminary identification of "contaminants of concern" at a site. The latter is, perhaps, an unfortunate term since the word "concern" may be misinterpreted as an implication of "hazard". As ATSDR uses the phrase, however, a "contaminant of concern" is merely a site-specific chemical substance that the health assessor has selected for further evaluation of potential health effects.
Generally, a chemical is selected as a contaminant of concern because its maximum concentration in air, water, or soil at the site exceeds one of ATSDR's comparison values. However, it cannot be emphasized strongly enough that comparison values are not thresholds of toxicity. While concentrations at or below the relevant comparison value may reasonably be considered safe, it does not automatically follow that any environmental concentration that exceeds a comparison value would be expected to produce adverse health effects. Indeed, the whole purpose behind highly conservative, health-based standards and guidelines is to enable health professionals to recognize and resolve potential public health problems before they become actual health hazards. The probability that adverse health outcomes will actually occur as a result of exposure to environmental contaminants depends on site specific conditions and individual lifestyle and genetic factors that affect the route, magnitude, and duration of actual exposure, and not on environmental concentrations alone.
Screening values based on non-cancer effects are obtained by dividing NOAELs or LOAELs determined in animal or (less often) human studies by cumulative safety margins (variously called safety factors, uncertainty factors, and modifying factors) that typically range from 10 to 1,000 or more. By contrast, cancer-based screening values are usually derived by linear extrapolation from animal data obtained at high doses, because human cancer incidence data for very low levels of exposure simply do not exist, and probably never will. In neither case can the resulting screening values (i.e., EMEGs or CREGs) be used to make realistic predictions of health risk associated with low-level exposures in humans.
Listed and described below are the various comparison values that ATSDR uses to select chemicals for further evaluation, along with the abbreviations for the most common units of measure.
|CREG||= Cancer Risk Evaluation Guides|
|EMEG||= Environmental Media Evaluation Guides|
|EPA||= Environmental Protection Agency|
|kg||= kilogram (1,000 grams)|
|m3||= cubic meter (used in reference to a volume of air equal to 1,000 liters)|
|MCL||= Maximum Contaminant Level|
|mg||= milligram (0.001 grams)|
|MRL||= Minimal Risk Level|
|ppb||= parts per billion, e.g., µg/L or µg/kg|
|ppm||= parts per million, e.g., mg/L or mg/kg|
|RfD||= Reference Dose|
|RMEG||= Reference Dose Media Evaluation Guide|
|µg||= microgram (0.000001 grams)|
Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations in water, soil, or air that would be expected to cause no more than one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors.
Environmental Protection Agency (EPA) values are similar to ATSDR's EMEGs in that they are risk-based concentrations derived for carcinogens and non-carcinogens from RfDs and Cancer Slope Factors, respectively, assuming default values for body weight, exposure duration and frequency, etc. Unlike EMEGs, however, they are available for fish, as well as for water, soil, and air.
Environmental Media Evaluation Guides (EMEGs) are concentrations of a contaminant in water, soil, or air that are unlikely to be associated with any appreciable risk of deleterious noncancer effects over a specified duration of exposure. EMEGs are derived from ATSDR minimal risk levels by factoring in default body weights and ingestion rates. Separate EMEGS are computed for acute (< 14 days), intermediate (15-364 days), and chronic (> 365 days) exposures.
Maximum Contaminant Levels (MCLs) represent contaminant concentrations in drinking water that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day.
Minimal Risk Levels (MRL) are estimates of daily human exposure to a chemical (i.e., doses expressed in mg/kg/day) that are unlikely to be associated with any appreciable risk of deleterious noncancer effects over a specified duration of exposure. MRLs are derived for acute (< 14 days), intermediate (15-364 days), and chronic (> 365 days) exposures, and are published in ATSDR's Toxicological Profiles for specific chemicals.
(EPA's) Reference Dose (RfD) is an estimate of the daily exposure to a contaminant unlikely to cause noncarcinogenic adverse health effects over a lifetime of exposure. Like ATSDR's MRL, EPA's RfD is a dose expressed in mg/kg/day.
Reference Dose Media Evaluation Guide (RMEG) is the concentration of a contaminant in air, water or soil that corresponds to EPA's RfD of RfC for that contaminant when default values for body weight and intake rates are taken into account.
COMPARISON VALUE REFERENCES
- Agency for Toxic Substances and Disease Registry. Health Assessment Guidance Manual. Atlanta: ATSDR, October 1992.
- National Institute for Occupational Safety and Health. Pocket Guide to Chemical Hazards. Washington D.C.: Department of Health Human Services, June 1994.
- U.S. Environmental Protection Agency. New Interim Region IV Guidance for Toxicity Equivalent Factors Methodology for Carcinogenic PAHs. February 11, 1992.
ATLANTA GAS LIGHT, AUGUSTA, GA.
|PATHWAY NAME:||ON-SITE SEDIMENT||ON-SITE SURFACE SOIL||AIR||ON-SITE SURFACE WATER||OFF-SITE SURFACE SOIL|
|Environmental Medium:||sediment||soil||air||surface water||soil|
|Exposure Route:||ingestion and
|Exposure Point:||Third Level Canal||AGL||vicinity of Southern Parcel||Third Level Canal||residential yards and adjacent commercial areas|
|Receptor Population:||possible trespassers and on-site workers||possible trespassers and on-site workers||area residents||possible trespassers||area residents|
|Contaminants of Concern:||arsenic, benzene, benzo(a)pyrene, chromium, chrysene, ethylbenzene, fluoranthene, lead, naphthalene, pyrene.||arsenic, benzo(a)pyrene, chromium, chrysene, cyanide, ethyl benzene, fluoranthene, lead, naphthalene, phenanthrene, pyrene.||arsenic, benzene, benzo(a)pyrene, chromium, chrysene, cyanide, ethyl benzene, fluoranthene, lead, naphthalene, pyrene, toluene.||benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, methylene chloride.||arsenic, benzo(a)pyrene, chromium, chrysene, lead.|
|Number of People Affected:||unknown||unknown||approx. 9,848 residents within 1 mile of the site||unknown||approx. 9,848 residents within 1 mile of the site|
ATLANTA GAS LIGHT, AUGUSTA, GA
|PATHWAY NAME:||OFF-SITE GROUNDWATER||OFF-SITE SURFACE WATER||ON-SITE SEDIMENT|
|Environmental Medium:||groundwater||surface water||sediment|
|Exposure Point:||groundwater seeps during high water events||Third Level Canal||Third Level Canal|
|Exposure Route:||limited exposure to area residents during flooding events||ingestion and dermal contact||ingestion and dermal contact|
|Receptor Population:||approx. 9,848 residents within 1 mile of the site||area children||possible trespassers|
|Contaminants of Concern:||arsenic, benzene, chrysene, lead, naphthalene||methylene chloride||arsenic, benzene, benzo(a)pyrene, chromium, chrysene, ethyl benzene, fluoranthene, lead, naphthalene, pyrene|
ATLANTA GAS LIGHT, AUGUSTA, GA
|PATHWAY NAME:||OFF-SITE GROUNDWATER||ON-SITE SURFACE WATER||ON-SITE SUBSURFACE SOIL||OFF-SITE SUBSURFACE SOIL|
|Environmental Medium:||groundwater||surface water||soil||soil|
|Exposure Point:||private drinking water well users||Third Level Canal||AGL||residential yards|
|Exposure Route:||ingestion, dermal contact, inhalation||ingestion, dermal contact||ingestion, dermal contact||ingestion, dermal contact|
|Receptor Population:||area residents, if wells were developed||possible trespassers||possible utility workers||possible utility workers|
|Contaminants of Concern:||arsenic, benzene, chrysene, fluoranthene, naphthalene, pyrene||benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, methylene chloride||arsenic, benzene, benzo(a)pyrene, chromium, chrysene, cyanide, ethyl benzene, fluoranthene, lead, naphthalene, pyrene, toluene.||arsenic, benzo(a)pyrene, chromium, chrysene, fluoranthene, lead, naphthalene, pyrene|
Comment 1. Tar is not a "waste by-product." Rather, tar was a valuable commodity that was essential to the operating economics of the facility.
Response: In the summary and background section of the document, where the MGP operations are discussed, the phrase "tar waste by-product", has been changed to "tar by-product", since the company considered it a valuable commodity. However, throughout the remaining document, tar waste is maintained, adopting the EPA definition of waste, "Unwanted materials left over from a manufacturing process ( USEPA, Glossary of Environmental Terms and Acronym List, Office of Public Affairs (A-107), Washington, DC 20460, OPA-87-017, August 1988).
Comments 2. The Draft PHA states that, after the Southern Bituminous plant closed, "AGL pumped its tar directly underground, producing a tar plume below the site." There is no evidence indicating that tar was ever "pumped" underground (if such a feat is even possible), and no such equipment has ever existed at the site. Retirees who worked at the plant in the early 1950's reported that a relatively small quantity of tar was buried in a trench on the "south parcel" following decommissioning of the plant. However, tar appears still to be located in that same trench and is not the source of any "tar plume" beneath the site. The best available environmental information indicates that the plume of groundwater impacts (including some product phase material) is the result of the downward migration of various residual products and their constituents resulting from a variety of process-related releases over the course of the MGP's operation.
Response: Appropriate changes have been made within the text to clarify these issues. Specifically, references to pumping tar underground have been deleted and replaced with text describing the reported "small quantity of tar [that was] buried in a trench" on the southern parcel.
Comment 3. The PHA states that area residents requested ATSDR to "evaluate AGL's disposal practices and determine whether potential exposures to site-related waste products are at levels of public health concern." AGLC does not believe this phrase accurately characterizes ATSDR's scope of work because the agency normally does not "evaluate" companies disposal practices," and because the inquiry was not limited to "site-related waste products"but, instead, addressed all forms of hazardous substances, whether resulting from waste products ( of which there was very little generated by the MGP) or from other process-related releases. AGLC suggests describing the scope of work as "investigating health risk resulting from the presence of hazardous substances associated with the MGP site."
Response: On page 4, line 20, the phrase "evaluate AGL's disposal practices" has been changed to read, "investigate the existence of hazardous contaminants at the AGL site and ....."
Comment 4. AGLC does not know what ATSDR means that "exposure to contaminants in the past is plausible..." If this means that according to the Richmond County Water Works Department, the area has been supplied with municipal drinking water, for example, since 1840. Further, as explained below, the actual operating areas of the plant have been fenced for as long as anyone can remember, and local residents certainly would not have been wandering around on the plant site while it was operating.
Response: The extent of contamination off-site has not been completely defined for soil and sedimentand represents a data gap. Until this issue is resolved, exposure to off-site contaminants is a plausible scenario. Furthermore, nearby residents and workers onsite could have been exposed to air contaminants that may have over longer periods of time resulted in chronic levels of health concern, then the level experienced during remediation of the holding tank on the Southern Parcel. Since no information is available on the quality of air in the past and if the levels of contaminants measured in the air during remediation occurred in the past, "exposure to contaminants in the past is plausible."
Comment 5. Although benzene is normally present in tar, it is not accurate to describe benzene as a "primary component" of that material.
Response: It is correct that benzene is not characterized as a primary component of tar, however, this statement refers to the sentence above where tar-like material was sampled on-site in several locations and where the human carcinogen benzene was detected at between 0.23-1,500 ppm (Table 6, D10). ATSDR has determined that the comparison value for benzene in air for acute exposure is 50 ppb and for exposure through soil the comparison value for benzene is the CREG of 20 ppm.
Comment 6. There should be no reason to prohibit use of groundwater for any purpose so long as those uses are consistent with groundwater quality. In addition, groundwater use is already prohibited by City Ordinance.
Response: The type and concentrations of contaminants detected in the groundwater beneath the AGL site (Tables 1 and 2) exceeded in most cases ATSDR's comparison values and/or EPA's Drinking Water Regulations and Health Advisories (USEPA, Drinking Water Regulations and Health Advisories, Office of Water 4304, EPA822-B-96-002, October 1996). If residents were using the groundwater as a potable water supply, ATSDR would conclude that this pathway of exposure is complete and represents a public health hazard. However, since residents of Augusta obtain their drinking water from the Augusta municipal system, ATSDR does not use drinking water comparison values or drinking water standards since this pathway of exposure has not been completed. That is why ATSDR does not provide Drinking Water Comparison Values in Tables 1 and 2. However, in the future, this water source may be needed or used and an exposure potential could exist. Therefore, ATSDR concludes that the community should be made aware of the contaminants in groundwater and recommends that groundwater not be used for future industrial or agricultural purposes nor as a potable water source.
Comment 7. The description of the gas manufacturing process is not quite accurate. Over the course of the MGPs 102-year operation, three different processes were used to manufacture gas which used a variety of different feedstocks in vary amounts including coal and oil. "Tar vapors" are not commonly understood as part of the off-gas stream generated by the process. Rather, "tars" are simply the condensate fraction of the coal distillation products. Additionally, tar was not a "waste" but, rather a valuable commodity sold in the open market. While in operation, the Southeastern Bituminous operation purchased tar from the Augusta MGP as well as other MGP sites around the southeast. Also, as mentioned in Comment 3 above, there is no evidence that AGLC ever "pumped" tar underground. Additionally, prior to the 1940's, the gas storage vessels were located on the Northern Parcel.
Response: In the summary and background section of the document, where the MGLC operations are discussed, the phrase "tar waste by-product", has been changed to "tar by-product", since the company considered it a valuable commodity. However, throughout the remaining document, tar waste is maintained, adopting the EPA definition of waste, "Unwanted materials left over from a manufacturing process ( USEPA, Glossary of Environmental Terms and Acronym List, Office of Public Affairs (A-107), Washington, DC 20460, OPA-87-017, August 1988).
Comment 8. The Northern Parcel has been fenced for as long as anyone associated with the site can remember (and, as is customary in the industry, has most likely been fenced for as long as there have been operations on that parcel). The 1992 fencing operation merely extended the fence to portions of the canal. Accordingly, any trespassing on AGL property would have been extremely limited. Further, it seems possible that the evidence of trespassing mentioned on page 6 (cigarette butts and beer bottles) were not the result of actual on-site trespasser but, rather, may have resulted from litter thrown by persons passing by the site.
Response: ATSDR has made modifications to the text to accurately reflect when the site was first fenced. However, based on information ATSDR obtained during its January 30, 1997 site visit and meeting with petitioners, it is ATSDR's understanding that area residents accessed the site in the past and that children frequently played ball and rode bicycles on site. Also, the cigarette butts and beer bottles that ATSDR observed on-site were in areas at a distance from the site boundary. ATSDR continues to believe that these observations suggest recent trespassing onto the site.
Comment 9. The Southern Parcel has been fenced for as long as anyone associated with the site can remember (and, as is customary in the industry, has most likely been fenced for as long as there have been storage vessels on that parcel). The 1992 fencing operation merely extended the fence to portions of the canal.
Response: Please see response to comment # 8, above.
Comment 10. As mentioned in comment 4 above, there is no evidence that AGLC ever "pumped" tar underground. Retirees who worked at the plant in the early 1950's reported that a relatively small quantity of the tar was buried in a trench on the "south parcel" following decommissioning of the plant.
Response: Please see response to comment # 2, above.
Comment 11. AGLC is not aware of any significant off-site migration of "tar-like material." Rather, it is the constituents of tar and other residuals that have migrated off-site.
Response: ATSDR agrees that clarification is needed when referring to site-related contamination. ATSDR's use of the term "tar-like material" stems from discussions in the RI about "tar-like" or "by-product like" materials. While the RI appears to use the terms "product" and "by-product-like" material somewhat synonymously, ATSDR has made the necessary modification to the text to reflect the following: 1) "product" refers to tar material detected in monitoring wells (floating or at the bottom of the casing); 2) "constituents of tar and other residuals" are contaminants such as BTEX and PAHs; and 3) "tar-like material," where appropriate, is used to describe observed materials in soils/sediment. Material observed in the former gas holder is referred to as "by-product-like material."
Product was encountered in certain wells on-site during groundwater sampling activities. According to the RI, product was noted during 1994 sampling events in MW-08, MW-09, and MW-14. Product was not reported in any off-site wells. However, BTEX and PAHs have been detected in a limited number of off-site monitoring well and geoprobe locations (see PHA Table 11), primarily on Blocks A and E. Note that the data summarized in the PHA are results from off-site CLP laboratory analysis; some of the highest hits detected in perimeter wells were from screening results. Note that benzene was detected as high as 35,965 ppm in GP-228 (deep) and at 6,858 ppm in GP-221A (deep) in screening samples from these Block E locations. On Block A, screening analysis revealed benzene as high 4,250 ppm in GP-215. BTEX and PAHs were also detected in these three wells. These samples were field lab analyzed.
Note, that while only trace levels of BTEX/PAHs were detected in CLP-tested "off-site" samples, the highest benzene concentrations detected in available sampling data were in MW-12 (64,000 ppb) and MW-13 (28,000 ppb), both of which are located in site perimeter locations.
According to the RI, "by-product-like" material was detected along the southern edge of Block A in field screening locations GP-12, GP-13, GP-211, and GP-212 (between 5 and 10 feet bgs). BTEX and PAHs were both detected at approximately 8 ppm in the field lab sample. The draft RI report also indicates that "by-product-like" material was encountered during the drilling of MW-204 on Block E at 32, 58, and 95 feet below ground surface (page 3-15 and 4-18) and at 25 feet bgs in other Block E wells (GP-6, GP-223, GP-224, GP-224C, and GP-224D). Field analyses detected BTEX and PAHs ranging from not detected to 42 and 20.8 ppm, respectively, in the deeper groundwater samples, but no BTEX/PAHs were detected in samples analyzed by an off-site laboratory.
Only limited evidence of visible off-site contamination is available. The RI indicates that a "tar-like" substance was observed covering portions of the ground surface and banks of the canal of Block B (the former Southern Bituminous property). This is likely associated with past activities at this location. No sampling occurred on Block B, however, because access was not granted.
Comment 12. AGLC is not aware of the discovery of "rubble" 14 feet below ground surface on the Western parcel, although MGP-related constituents have been located at that depth. Additionally, under the current plan, the Western parcel will be addressed before the canal sediment.
Response: On page 7, ATSDR deleted references to rubble 14 feet below ground surface on the Western Parcel.
Comment 13. AGLC believes visible tar is only present along the canal bank on the Northern Parcel.
Response: While most of the visible tar was witnessed along the canal bank, tar solids on the ground surface on the Northern and Southern Parcels were also noted by ATSDR staff during the site tour. Most of the tar spots were hardened and appeared as "circles" indicating the tar had probably percolated through the soil to the surface during the warmer months.
Comment 14. All the parishioners of the church clearly do not live in the area of the MGP. Further, AGLC is aware of no evidence of day care activities at the church.
Response: This information was reported to ATSDR by residents during the community meeting (January, 1997).
Comment 15. There is no evidence that Southeastern Bituminous ever operated a "tar-disposal facility." Rather, it operated an asphalt production plant. Southeastern bituminous did purchase tar from the Augusta MGP as well as other MGPs throughout the southeastern United States. The releases at the Southeastern Bituminous facility, like those at the Augusta MGP, are believed to be primarily the result of spills and other process-related releases, although the dismantling of that plant, in which AGLC had no involvement, may have resulted in disposal on that property.
Response: ATSDR changed the text to indicate that Southern Bituminous operated an "asphalt production plant," not a "tar-disposal facility" (page 10).
Comment 16. "Tar manufacturing" should be changed to "gas manufacturing." In addition, the best available information indicates the Augusta MGP commenced operations in 1852 and ceased operations in 1954. The Northern Parcel is not currently used as "an operations center," although it is used for natural gas transfer.
Response: Thank you for the clarification, the necessary changes have been made.
Comment 17. The 13 monitoring wells were installed during the course of a series of investigations which preceded the RI. Additionally, AGLC has never been unable to construct wells at planned locations because of tar-like material. AGLC has abandoned three wells after construction because product was encountered.
Response: ATSDR changed the text to reflect that certain wells were abandoned during installation because product was encountered. See also Comment 11.
Comment 18. AGL has installed and sampled 4 wells on the Western Parcel.
Response: Based on data presented in the Western Parcel RI and on Comment 56, ATSDR reviewed data from 3 monitoring wells on the Western Parcel: MW-17, MW-18, and MW-19. Results are presented in Table 2, Appendix D.
Comment 19. The 75 ppm figure identified as the "Georgia residential "action levels" is somewhat inaccurate. Georgia does not have "action levels" in the same sense as does, for example EPA (which uses 400 ppm lead). Rather, the 75 ppm level is the default, non-site specific residential risk reduction standard for soil under the state Hazardous Site Response Act (HSRA). Health-based standards for lead is currently being developed by EPD. For residential property, EPD is currently proposing 400 ppm, with higher levels for non-residential property.
Response: The 75 ppm comparison value for lead in soil is from a Georgia Environmental Protection Department, Hazardous Sites Response Program document for Type 1 (i.e., protective of public health and the environment) Soil Criteria. This action level was included in the PHA to represent a conservative screening value. The text includes a discussion on the potential health implications of lead at the levels detected at and around the site. ATSDR also modified the text in Appendix D, Tables 5, 7, 8, 9, 13, and 14, identifying the 75 ppm value as a conservative screening value for residential soils. ATSDR has revised text and tables to reflect the 400 ppm residential cleanup level recently approved.
Comment 20. The TCLP test was not used to evaluate the potential for hazardous components to leach into groundwater. Rather, the test is a very aggressive assessment tool used to determine whether solid waste is regulated under the Resource Conservation and Recovery Act (RCRA). Other tests are available to estimate leaching under environmental conditions, but were not utilized at this site. See also, page 22, line 11.
Response: ATSDR understands that the purpose of the TCLP test was to evaluate whether the material was regulated under RCRA, but also recognizes that the premise of the TCLP test is to evaluate potential leachability. ATSDR understands that TCLP analysis is performed under aggressive laboratory conditions which are not likely to mimicked in nature. ATSDR modified the text slightly on Page 16 to more clearly state the purpose of performing TCLP analysis on AGL samples.
According to EPA 40 CFR Ch. 1 (7-1-92 Edition) Section 1.0 Scope and Application 1.1. "The TCLP is designed to determine the mobility of both organic and inorganic analytes present in liquid, solid, and multiphasic waste." 1.3 "If an analysis of any one of the liquid fractions of the TCLP extract indicates that high concentrations that, even after accounting for dilution from the other fractions of the extract, the concentration would be equal to or above regulatory level for that compound, then the waste is hazardous and it is not necessary to analyze the remaining fractions of the extract." While the TCLP is used for regulatory purposes, ATSDR used the Comparison Values established for assessing concentrations of hazardous substances at levels of public health concern not TCLP levels established by EPA for regulatory purposes.
Comment 21. Although all samples were analyzed for inorganic compounds, some were also sampled for other priority pollutant compounds as appropriate under the sampling program.
Response: Data tables in the RI present sampling data for inorganic compounds, acetone, carbon disulfide, and 2-butanone. Analytes detected below comparison value were not included in Table 10.
Comment 22. The best available information indicates the Northern and Southern Parcels have been fenced for as long as anyone associated with the site can remember (and, as is customary in the industry, have most like been fenced for as long as there have been operations on those parcels). The 1992 fencing operation merely extended the fencing to portions of the canal.
Response: Please see response to Comment 8, above.
Comment 23. Section A of the Pathway Analysis indicates that, 1) "On-site Sediment: Ingestion and Dermal contact;" 2) "On-Site Surface Soil: Ingestion and Dermal Contact;" and 3) "On-Site Surface Water: Dermal Contact," are all "Completed Pathways." However, the best available information indicates the Northern and Southern Parcels have been fenced for as long as anyone associated with the site can remember. The 1992 fencing operation merely extended the fencing to portions of the canal. Accordingly, it would not be accurate to characterize access to the site as "readily available" prior to 1992. (See page 25, line 22.) Rather, access to most of the areas where trespassers or even authorized persons might have come into contact with impacted media was limited by either fencing or natural barriers (ie., for the canal, slope, and vegetation) even prior to 1992. Furthermore, much of the evidence of trespassing (cigarette butts and beer bottles) could be the result of littering from persons passing by the site rather than trespassers. As such, it seems doubtful that any of the "On-site" exposure pathways have ever been actual completed pathways. Therefore, these "on-site" pathways should be moved to section C, "Eliminated Exposure Pathways" or, at most, "Potential Exposure Pathways" under section B.
Response: Please see response to Comment 8.
Under the section "Pathway analysis", ATSDR defines a completed exposure pathway (page 25). "An exposure pathway is complete if all five elements of an exposure pathway link the contaminant source to a receptor population and include; 1) a source of contamination, 2) environmental media in which the contaminants may be present or may migrate, 3) points of human exposure, 4) routes of human exposure such as ingestion, inhalation, or dermal exposure, and 5) a receptor population." As defined in the this section as well as summarized on page 76, levels of contaminants on-site were detected above ATSDR's health based comparison values in soil, sediment and surface water and that on-site AGL workers and occasional trespassers would have come into contact with these contaminants in the past. However, ATSDR states that the exposure duration would be intermittent and of short duration and would not likely result in adverse health effects.
Comment 24. The PHA suggests that "people may have been exposed to contaminated groundwater when the area floods." However, AGLC is aware of no process by which flood events in the area of the Augusta MGP could operate to bring groundwater to the surface. Further, in the event groundwater were somehow brought to the surface by flooding, concentrations of any of the constituents detected in groundwater during normal-stage periods would likely be diluted by orders of magnitude. Accordingly, off-site groundwater should not be considered even a potential exposure pathway.
Response: On January 30, 1997, ATSDR held a meeting with petitioners at the Trinity C.M.E. Church on Taylor St. Several members of the audience expressed concerns about the streets in the vicinity of the canal becoming flooded when it rains. The residents have expressed concern about whether the water is just rainwater, or whether the water is contaminated. ATSDR has no sampling data from such high water events. ATSDR agrees that concentrations of constituents would be diluted; however because the groundwater table is high and because of the reported presence of flood conditions, off-site groundwater cannot be ruled out as a potential exposure pathway. ATSDR evaluated what might be considered a worst-case scenario in the absence of actual data.
Comments 25. The PHA suggests people may be exposed to benzene in groundwater "during high water (flooding) episodes." However, as suggested earlier, AGLC does not believe this condition is possible in the area of the MGP. Further, in the event groundwater were brought to the surface by flooding, concentrations of any of the constituents detected in groundwater during normal-stage periods would likely be diluted by orders of magnitude.
Response: Please see response to Comment # 24, above.
Comment 26. While the City of Augusta does not directly prohibit the installation of groundwater wells for drinking purposes, it does require that homes serviced by drinking water wells employ septic systems and it prohibits the installation of septic tanks in areas serviced by the municipal sewer system. Accordingly, the practical effect is a prohibition on installing drinking water wells in areas like that surrounding the Augusta MGP which are serviced by the municipal sewer system.
Response: Please see response to Comment # 6.
Comment 27. ATSDR concluded that the site "represents an Indeterminate Public Health Hazard for past exposures." However, as explained above, access to most of the areas where trespassers or even authorized persons might have come into contact with impacted media was limited by either fencing or natural barriers (i.e., for the canal, slope and vegetation) even prior to 1992. Accordingly, the best available information indicates No Apparent Public Health Hazard even for past exposures.
Response ATSDR assigns a "Public Health Hazard Category", to each site and provides this information in the Health Assessment. This assignment of a hazard category is based on important factors including but not limited to the following; the presence of a completed or potential exposure pathway, characterization and availability of contaminant concentrations on- and off-site, presence of sensitive population and public health concerns, opportunity for acute or chronic exposures, the nature of toxic effects associated with site contaminants. Information on past exposure to contaminants in the air is not available for this site, however air data obtained during remedial activities identified contaminants of concern that may have health implications for long term "chronic" exposures. Additionally, residential surface soil "off-site" has not been sampled and represents a data gap. The ATSDR category C "Indeterminate Public Health Hazard", is used for a site where information or data is not available for all environmental media to which humans may be exposed. ATSDR makes recommendations to identify the data or information needed to assess the public health risk and the public health actions recommended depends on the hazard potential of the site as it relates to public health.
Comment 28. ATSDR recommends "health education regarding exposures to lead in the environment and home" (line 6, page 40) and also informing "residents of potential health effects associated with contaminated groundwater, soils, sediment, and air" (line 14, page 40). However, the PHA appears to conclude that there are no such risks posed by the MGP site. ATSDR should clarify that these educational efforts are intended as general information and not to describe specific, actual problems posed by the MGP site.
Response: Potential exposures may have existed in the past and may exist in the future if residents come in contact with the contaminants of concerned under the exposure scenarios defined on page 77. As mentioned above in ATSDR's response to Comment 27, public health action recommendations are made depending on the hazard potential of the site as it relates to public health. Community health education is recommended by ATSDR if but not limited to the following criteria; 1) a human population lives/works along potential pathway(s) of exposure associated with a hazardous waste site, 2) Community concern for public health exists as a result of reports about exposures and/or reports of disease in the community, and 3)human exposure to hazardous substance(s) may have occurred or may be occurring. ATSDR PHA Guidance Manual page 8-13.
Comment 29. ATSDR should clarify the nature and purpose of it's recommendation to inform residents of potential health effects associated with contaminated groundwater, soils, sediment, and air (p.40) given that the conclusion of the AGL Public Health Assessment was "No Apparent Public Health Hazard (p. 38). The Gradient company suggests that the document explicitly state that this recommendation was made for general health education purposes and not in response to any risk posed by the MGP site.
Response: Please see response to Comment 28.
Comment 30. ATSDR's recommendation to inform residents about potential health effects associated with air exposures is inconsistent with the statement that short-term exposure to air contaminants poses no apparent public health concern (p. 34).
Response: Short term exposure of residents to contaminants sampled in the air on the Southern Parcel during remedial activities that occurred between January 6, 1997 and June 5, 1997 are not expected to result in adverse health effects. However, we do not have air data for chronic exposures in the past which are plausible. Therefore, ATSDR recognizes this past exposure potential and makes recommendations for health education in the community.
Comment 31. ATSDR does not discuss the lack of association between odors and health risks, an issue that may become relevant when odors are released from sub-surface soils during MGP site remediation.
Response: Several reports and surveys have attempted to address the correlation between odors and perceived health risks in communities. Odors are the result of gaseous emissions from a number of potential environmental sources including hazardous waste, municipal, agricultural, and industrial air emission sources. Results of surveys and studies have shown that unacceptable environmental odors may trigger symptoms by a number of physiological mechanisms including the aggravation of an existing health condition, innate odor aversions, stress-induced illness, or pheromonal reactions. Detection techniques either are not sensitive enough or have not been developed to demonstrate a clear association between odors and health effects; however, given the type of operations on the AGL and surrounding sites, it is plausible that residents may have experienced noxious odors in the past. Since air data for past exposures is not available, it is difficult to speculate on any resultant health outcomes. While the severity of odors may be subjective and not validated by toxicological analysis, the perceived risk to health by the community is real and concerns need to be recognized and addressed.
Comment 32. ATSDR also recommends that the extent of lead contamination in soil on residential properties be evaluated and that residents be provided with health education regarding exposures to lead in the environment and home. We suggest that ATSDR explicitly state that this recommendation is being made for general health education purposes and not in response to any risk posed by the MGP site.
Response: Please see response to Comment 28.
Comment 33. The comparison values are not always provided for the reader. For example, Table 11 on page 64 lists the concentrations of chemicals detected in groundwater but does not list the comparison values. If the comparison values are not available or not applicable (because there is no exposure to groundwater), this should be clearly stated.
Response: At present, residents are receiving their drinking water from the Augusta municipal water system and ground water is not a completed pathway of exposure; therefore, ATSDR does not use drinking water comparison values to screen for contaminants of concern and further toxicological evaluations.
Comment 34. The comparison values listed in Table 9 (CREG, EMEG, RMEG) are not appropriate, since residents are not exposed to on-site subsurface soil. Further these comparison values are based on 10-6 cancer risk, which may not be appropriate for future on-site non-residential land use scenarios where appropriate target risks could range from 10-6 to 10-4.
Response: Comparison values in Table 9 are appropriate to screen for contaminants of concern that residents may have been or may be exposed to during periods of remedial activity where soil below 2 ft may be exposed. The risk values are EPA established regulatory guidelines and are not used by ATSDR to evaluate expected health effects.
Comment 35. ATSDR incorrectly identifies 75-ppm as the "Georgia Action Level: for lead. The 75-ppm is the default, non-site-specific residential risk reduction standard for soil under the Rules for Hazardous Site Response. The issue of the default value in Tables 5, 7,8, and 9 fails to recognize the USEPA Soil Screening Level for lead in residential settings (400 ppm), nor does it consider the background levels of lead near the site (ranging to a maximum of 659 ppm). Further, it should be noted that Georgia EPD has proposed the 400-ppm level as the applicable standard for residential clean up.
Response: Please see response to Comment 19.
Comment 36. Except for the benzene unit risk reported on page 85, the actual toxicity values used in calculating risk estimates (reference doses, unit risks) are not presented. The results of the risk equations (daily intakes, hazard quotients and incremental cancer risk estimates) are also not presented.
Response: ATSDR does not usually present EPA risk calculations in health assessments. Public Health Assessments are not risk-based documents.
Comment 37. Please note, the final Remedial Investigation (RI) has been released, but not approved.
Response. ATSDR is aware of the release of the draft final RI. ATSDR also realizes there may be additional changes made to the document before it becomes final.
Comment 38. The use of the word "site" in the Public Health Assessment differs from the use of the word "site" in other Atlanta Gas Light documents.
Response. In general, the word "site" is used in a variety of contexts. In this Public Health Assessment, ATSDR considers the three parcels (Northern, Southern, and Western) the "site".
Comment 39. The word "include" is used in several sections of the Public Health Assessment when identifying chemicals. Please clarify what this means.
Response. If a sentence states, 'including lead and arsenic', the sentence means 'including but not limited to lead and arsenic.' The list of chemicals presented after the word "include" is not exhaustive.
Comment 40. In several places in the Public Health Assessment, ATSDR refers to the time frame the facility was in operation. These references should be changed to state "from approximately the 1850s" and not "from the 1800s."
Response. This change has been reflected in the document.
Comment 41. The date the Remedial Investigation was initiated was April 1994. Further, there were five phases and not two.
Response: Thank you for the clarification, the necessary changes have been made.
Comment 42. Soil should be added to the list of media indicated in the second paragraph of the Summary section of the Public Health Assessment.
Response: Thank you for the clarification, the necessary change has been made.
Comment 43. Please clarify specific media being referred to on page 5, second paragraph.
Response: Please refer to the main text for this media clarification.
Comment 44. Please change the first sentence in the second paragraph in the Background section of the Public Health Assessment to state, "The MGP heated coal and oil to high temperatures to produce manufactured gas, most of which went to gas holders on the Northern and Southern Parcels."
Response: Change noted.
Comment 45. Southern Bituminous is not the correct name of the facility across the canal from AGL's Northern Parcel. The facility was called Southeastern Bituminous.
Response: The name of the facility has been changed in all places it is referenced in the Public Health Assessment.
Comment 46. Please verify if Southeastern Bituminous was "demolished" in the 1950s or just closed.
Response: On page 6, ATSDR has changed the word "demolished" to "closed."
Comment 47. Please add sediment to the media list in the first sentence of the third paragraph in the Background section of the Public Health Assessment.
Response: Change noted.
Comment 48. Please note that both the Remedial Investigation and previous site investigations indicated levels of contaminants above MCLs.
Response: This change has been noted in the main text of the Public Health Assessment.
Comment 49. Please change the section about the Gas Holder No. 5 to past tense since it has been removed.
Response: Change noted.
Comment 50. Remedial activities for the Western Parcel will not begin until 1998.
Response: Change noted.
Comment 51. In the Western Parcel description in the Background section, ATSDR may want to add a sentence about the sub-surface canal boring that detected tar material just to the south of this parcel.
Response: ATSDR's review of the Western Parcel's RI revealed that tar material was located on the northern and central portions of the site, and towards the Canal. ATSDR requires additional information to detail any contamination detected in the area south of this parcel.
Comment 52. Sampling data exists for Block B in the final Remedial Investigation report.
Response: ATSDR is aware the final Remedial Investigation report has been released, but not approved.
Comment 53. AGL installed and sampled a total of 17 on-site monitoring wells as a part of site investigations on the Southern and Northern Parcels, not 13 wells.
Response: ATSDR review ed the data and found reference to 16 on-site monitoring wells that were installed and sampled as part of the investigations of the northern and southern parcels (page 14).
Comment 54. Please verify the sentence, "AGL was not able to construct wells at several planned locations on-site because tar-like material was encountered during drilling."
Response: This statement is based on the following excerpt from page 3-7 of the RI: "Following a review of information gathered during the source characterization and ground-water screening field activities, it was determined that all four monitoring wells [originally planned to be installed on site] should be installed at off-site locations due to the presence of by-product-like material in the vicinity of the proposed on-site monitoring well locations."
Comment 55. Please verify the concentration of Benzene (14,000 ppb) is the maximum in MW-6 as the final RI data indicates a higher concentration for this well.
Response: ATSDR changed the next highest detected concentration of benzene from 14,000 ppb to 28,000 ppb, detected in MW-13. Benzene was detected at MW-6 at 20,000 ppb (page 14).
Comment 56. Please verify the number of wells on the Western Parcel. The Public Health Assessment text indicates 11 monitoring wells; however, there are only 3 wells. Also, please review Table 2, Appendix D, which also refers to 11 monitoring wells. Further, what does "UMW" refer to in Table 2?
Response: Please see Comment 18. UMW reportedly indicates unfiltered monitoring well. Refer to Table A-3, page A-3-3 and B-3-5 of the Western Parcel RI in which three samples are listed: UMW-17, UMW-18, and UMW-19. ATSDR changed "11 Monitoring Well" locations on the Western Parcel to 3 monitoring well and 3 geoprobe locations.
Comment 57. Please verify if the data mentioned in the paragraph about Surface Water from the On-site Contamination section is from phase II (as the Public Health Assessment indicates) or phase I.
Response: Text and table headings for surface water have been revised to clarify from where and when samples were collected. The data presented in the PHA only included data analyzed in certified laboratories off-site. Please see Table 4.
Comment 58. Please verify the numbers of sampling points in the paragraph about Sediment in the On-site Contamination section.
Response: Text and table headings for sediment have been revised to clarify from where and when samples were collected. The data presented in the PHA only included data analyzed in certified laboratories off-site. Please see Table 5.
Comment 59. Please clarify the second to last and the last sentences in the paragraph about Sediment in the On-site Contamination section as it sounds as if ATSDR is referring to Southeastern Bituminous property and not the canal.
Response: Change noted.
Comment 60. In the description about Surface Water in the Off-site Contamination section, was methylene chloride detected or is it a lab contaminant (i.e., please re-check data validation).
Response: Methylene chloride was listed in Table E-3 of the RI at 59.0 J; this is considered a valid sample and is therefore included in the data summary table. Data validation reports were not included with the RI. If there is additional information regarding lab contamination of the sample, please provide the information to ATSDR.