1200 Pennsylvania Avenue, N.W. Agency Washington, DC September 2007 O ce of Solid Waste and Emergency Response

Transcription

1 EPA United States Environmental Protection 1200 Pennsylvania Avenue, N.W. Agency Washington, DC September 2007 O ce of Solid Waste and Emergency Response Support Document for the Revised National Priorities List Final Rule South Minneapolis Residential Soil Contamination

2 Support Document for the Revised National Priorities List Final Rule South Minneapolis Residential Soil Contamination September 2007 State, Tribal, and Site Identification Center Office of Solid Waste and Emergency Response U.S. Environmental Protection Agency Washington, DC 20460

3 CONTENTS Executive Summary... iii Introduction... iv Background of the NPL... iv Development of the NPL... v Hazard Ranking System... v Other Mechanisms for Listing... vi Organization of this Document... vii Glossary... vii Region 5 South Minneapolis Residential Soil Contamination List of Commenters/Correspondents Site Description Summary of Comments/Correspondence Conclusion... 7 ii

4 EXECUTIVE SUMMARY Section 105(a)(8)(B) of CERCLA, as amended by SARA, requires that the EPA prepare a list of national priorities among the known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the United States. An original National Priorities List (NPL) was promulgated on September 8, 1983 (48 FR 40658). CERCLA also requires the EPA to update the list at least annually. This document provides responses to public comments received on the South Minneapolis Residential Soil Contamination site in Minneapolis, Minnesota, proposed on September 27, 2006 (71 FR 56433). This site is being added to the NPL based on an evaluation under the Hazard Ranking System (HRS) in a final rule published in the Federal Register in September Several additional sites are being promulgated concurrently. iii

5 INTRODUCTION This document explains the rationale for adding the South Minneapolis Residential Soil Contamination site in Minneapolis, Minnesota, to the NPL of uncontrolled hazardous waste sites and also provides the responses to public comments received on this site. The EPA proposed this site on September 27, 2006 (71 FR 56433). This site is being added to the NPL based on an evaluation under the HRS in a final rule published in the Federal Register in September Background of the NPL In 1980, Congress enacted CERCLA, 42 U.S.C. Sections 9601 et seq. in response to the dangers of uncontrolled hazardous waste sites. CERCLA was amended on October 17, 1986, by SARA, Public Law No , stat., 1613 et seq. To implement CERCLA, EPA promulgated the revised National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 CFR Part 300, on July 16, 1982 (47 FR 31180), pursuant to CERCLA Section 105 and Executive Order (46 FR 42237, August 20, 1981). The NCP, further revised by EPA on September 16, 1985 (50 FR 37624) and November 20, 1985 (50 FR 47912), sets forth guidelines and procedures needed to respond under CERCLA to releases and threatened releases of hazardous substances, pollutants, or contaminants. On March 8, 1990 (55 FR 8666), EPA further revised the NCP in response to SARA. Section 105(a)(8)(A) of CERCLA, as amended by SARA, requires that the NCP include criteria for determining priorities among releases or threatened releases throughout the United States for the purpose of taking remedial action and, to the extent practicable, take into account the potential urgency of such action, for the purpose of taking removal action. Removal action involves cleanup or other actions that are taken in response to emergency conditions or on a short-term or temporary basis (CERCLA Section 101(23)). Remedial action tends to be long-term in nature and involves response actions that are consistent with a permanent remedy for a release (CERCLA Section 101(24)). Criteria for placing sites on the NPL, which makes them eligible for remedial actions financed by the Trust Fund established under CERCLA, were included in the HRS, which EPA promulgated as Appendix A of the NCP (47 FR 31219, July 16, 1982). On December 14, 1990 (56 FR 51532), EPA promulgated revisions to the HRS in response to SARA, and established the effective date for the HRS revisions as March 15, Section 105(a)(8)(B) of CERCLA, as amended, requires that the statutory criteria provided by the HRS be used to prepare a list of national priorities among the known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the United States. The list, which is Appendix B of the NCP, is the NPL. An original NPL of 406 sites was promulgated on September 8, 1983 (48 FR 40658). At that time, an HRS score of 28.5 was established as the cutoff for listing because it yielded an initial NPL of at least 400 sites, as suggested by CERCLA. The NPL has been expanded several times since then, most recently on March 7, 2007 (72 FR 10105). The Agency also has published a number of proposed rulemakings to add sites to the NPL. The most recent proposal was also on March 7, 2007 (72 FR 10105). Development of the NPL The primary purpose of the NPL is stated in the legislative history of CERCLA (Report of the Committee on iv

6 Environment and Public Works, Senate Report No , 96th Cong., 2d Sess. 60 [1980]): The priority list serves primarily informational purposes, identifying for the States and the public those facilities and sites or other releases which appear to warrant remedial actions. Inclusion of a facility or site on the list does not in itself reflect a judgment of the activities of its owner or operator, it does not require those persons to undertake any action, nor does it assign liability to any person. Subsequent government actions will be necessary in order to do so, and these actions will be attended by all appropriate procedural safeguards. The purpose of the NPL, therefore, is primarily to serve as an informational and management tool. The identification of a site for the NPL is intended primarily to guide EPA in determining which sites warrant further investigation to assess the nature and extent of the human health and environmental risks associated with the site and to determine what CERCLA-financed remedial action(s), if any, may be appropriate. The NPL also serves to notify the public of sites EPA believes warrant further investigation. Finally, listing a site may, to the extent potentially responsible parties are identifiable at the time of listing, serve as notice to such parties that the Agency may initiate CERCLA-financed remedial action. CERCLA Section 105(a)(8)(B) directs EPA to list priority sites among the known releases or threatened release of hazardous substances, pollutants, or contaminants, and Section 105(a)(8)(A) directs EPA to consider certain enumerated and other appropriate factors in doing so. Thus, as a matter of policy, EPA has the discretion not to use CERCLA to respond to certain types of releases. Where other authorities exist, placing sites on the NPL for possible remedial action under CERCLA may not be appropriate. Therefore, EPA has chosen not to place certain types of sites on the NPL even though CERCLA does not exclude such action. If, however, the Agency later determines that sites not listed as a matter of policy are not being properly responded to, the Agency may consider placing them on the NPL. Hazard Ranking System The HRS is the principle mechanism EPA uses to place uncontrolled waste sites on the NPL. It is a numerically based screening system that uses information from initial, limited investigations -- the preliminary assessment and site inspection -- to assess the relative potential of sites to pose a threat to human health or the environment. HRS scores, however, do not determine the sequence in which EPA funds remedial response actions, because the information collected to develop HRS scores is not sufficient in itself to determine either the extent of contamination or the appropriate response for a particular site. Moreover, the sites with the highest scores do not necessarily come to the Agency's attention first, so that addressing sites strictly on the basis of ranking would in some cases require stopping work at sites where it was already underway. Thus, EPA relies on further, more detailed studies in the remedial investigation/feasibility study that typically follows listing. The HRS uses a structured value analysis approach to scoring sites. This approach assigns numerical values to factors that relate to or indicate risk, based on conditions at the site. The factors are grouped into three categories. Each category has a maximum value. The categories include: $ likelihood that a site has released or has the potential to release hazardous substances into the environment; $ characteristics of the waste (toxicity and waste quantity); and $ people or sensitive environments (targets) affected by the release. v

7 Under the HRS, four pathways can be scored for one or more threats: $ Ground Water Migration (S gw ) - drinking water $ Surface Water Migration (S sw ) These threats are evaluated for two separate migration components (overland/flood and ground water to surface water). - drinking water - human food chain - sensitive environments $ Soil Exposure (S s ) - resident population - nearby population - sensitive environments $ Air Migration (S a ) - population - sensitive environments After scores are calculated for one or more pathways according to prescribed guidelines, they are combined using the following root-mean-square equation to determine the overall site score (S), which ranges from 0 to 100: S = S 2 gw S sw + S s + S 4 2 a If all pathway scores are low, the HRS score is low. However, the HRS score can be relatively high even if only one pathway score is high. This is an important requirement for HRS scoring because some extremely dangerous sites pose threats through only one pathway. For example, buried leaking drums of hazardous substances can contaminate drinking water wells, but -- if the drums are buried deep enough and the substances not very volatile -- not surface water or air. Other Mechanisms for Listing Aside from the HRS, there are two other mechanisms by which sites can be placed on the NPL. The first of these mechanisms, authorized by the NCP at 40 CFR (c)(2), allows each State and Territory to designate one site as its highest priority regardless of score. The last mechanism, authorized by the NCP at 40 CFR (c)(3), allows listing a site if it meets all three of these requirements: $ Agency for Toxic Substances and Disease Registry (ATSDR) of the U.S. Public Health Service has issued a health advisory that recommends dissociation of individuals from the release; $ EPA determines the site poses a significant threat to public health; and vi

8 $ EPA anticipates it will be more cost-effective to use its remedial authority than to use its emergency removal authority to respond to the site. Organization of this Document The following section addresses site-specific public comments. The site discussion begins with a list of commenters, followed by a site description, a summary of comments, and Agency responses. A concluding statement indicates the effect of the comments on the HRS score for the site. Glossary The following acronyms and abbreviations are used throughout the text: Agency ATSDR CERCLA EPA HRS HRS Score NCP NPL NPL-### PA/SI PRP RCRA RD/RA RI/FS ROD U.S. Environmental Protection Agency Agency for Toxic Substances and Disease Registry Comprehensive Environmental Response, Compensation, and Liability Act of 1980, 42 U.S.C. Sections 9601 et seq., also known as Superfund U.S. Environmental Protection Agency Hazard Ranking System, Appendix A of the National Oil and Hazardous Substances Pollution Contingency Plan, 40 C.F.R. Part 300 Overall site score calculated using the Hazard Ranking System; ranges from 0 to 100 National Oil and Hazardous Substances Pollution Contingency Plan, 40 C.F.R. Part 300 National Priorities List, Appendix B of the NCP Public comment index numbers as recorded in the Superfund Docket in EPA Headquarters and in Regional offices Preliminary Assessment/Site Inspection Potentially Responsible Party Resource Conservation and Recovery Act of 1976 (U.S.C , as amended) Remedial Design/Remedial Action Remedial Investigation/Feasibility Study Record of Decision, explaining the CERCLA-funded cleanup alternative(s) to be used at an NPL site vii

9 SARA Superfund Amendments and Reauthorization Act of 1986, Public Law No , stat., 1613 et seq viii

10 Region 5 - South Minneapolis Residential Soil Contamination, Minneapolis, Minnesota 1. List of Commenters/Correspondents EPA-HQ-SFUND EPA-HQ-SFUND EPA-HQ-SFUND Comment dated November 27, 2006, from Melinda W. Hahn, Ph.D., and Mark A. Travers, P.G., on behalf of the CMC Heartland Partners Liquidating Trust Comment dated October 24, 2006, from R.T. Rybak, Mayor of the City of Minneapolis, Cam Gordon, Council Member of the Second Ward, and Gary Schiff, Council Member of the Ninth Ward Correspondence dated March 18, 2005, from Tim Pawlenty, Governor of the State of Minnesota 2. Site Description The South Minneapolis Residential Soil Contamination (SMRSC), also known as the Phillips Neighborhood site, is located in Minneapolis, Hennepin County, Minnesota. For HRS purposes, it comprises residential properties located in proximity to a former industrial source area known as the CMC Heartland Lite Yard (Lite Yard). The area of observed soil contamination in the HRS documentation record was defined as the area between 31 st and 21 st Streets East and between Hiawatha Avenue and 12 th Avenue South based on analytical results for soil samples collected in the area during 2001, 2003, 2004, and An area of observed contamination was delineated based on analytical results for surface soil samples collected from residential yards and within 200 feet of residences. Arsenic was detected in soil on the Lite Yard facility at concentrations as high as 18,000 24,000 mg/kg. Arsenicbased pesticides and raw materials were handled at this facility from 1938 at least through The site was scored based on the soil exposure pathway. Due to the presence of elevated levels of arsenic in surface soil samples collected from residential yards near the Lite Yard facility, the populations associated with residential properties are being impacted in part by the Lite Yard facility and the handling of large volumes of arsenic trioxide powder at the Lite Yard facility. The soil exposure threat was scored because there is a resident population located on and within 200 feet of an area of observed or inferred contamination. 3. Summary of Comments and Correspondence The Honorable Tim Pawlenty, Governor of Minnesota, expressed support for the listing of the SMRSC on the National Priorities List (NPL) because this listing is crucial to enable future removal of arsenic contaminated soil from residential properties in the South Minneapolis neighborhood of Minneapolis, Minnesota. The Honorable R.T. Rybak, Mayor of the City of Minneapolis, Cam Gordon, Council Member of the Second Ward, and Gary Schiff, Council Member of the Ninth Ward, also expressed support for the listing of the SMRSC on the NPL for timely clean-up, as recommended by the Regional EPA Administrator. 1

11 Two commenters, Ms. Melinda W. Hahn and Mr. Mark A. Travers, on behalf of the CMC Heartland Partners Liquidating Trust (the Trust) wrote to request that EPA fully consider other plausible and likely sources of arsenic to residential soil other than the operations at the Lite Yard Site from 1938 to 1963 and to properly identify potentially responsible parties. These comments do not question the validity of the Hazard Ranking System score or oppose the placement of the site on the NPL. 3.1 Support for Listing The Honorable Tim Pawlenty, Governor of Minnesota, the Honorable R.T. Rybak, Mayor of the City of Minneapolis, Cam Gordon, Council Member of the Second Ward, and Gary Schiff, Council Member of the Ninth Ward, expressed support for the listing of SMRSC on the NPL. In response, the Agency has added SMRSC site to the NPL. Listing makes a site eligible for remedial action funding under CERCLA, and EPA will examine the site to determine the appropriate response action(s). Actual funding may not necessarily be undertaken in the precise order of HRS scores, however, and upon more detailed investigation may not be necessary at all in some cases. EPA will determine the need for using Superfund monies for remedial activities on a site-by-site basis, taking into account site risks, State priorities, further site investigation, other response alternatives, and other factors as appropriate. 3.2 Site Definition CMC Heartland Partners Liquidating Trust made a comment asking why EPA did not also use preliminary data from an expanded investigation of the area that EPA conducted in At the same time, the commenter suggests that some of the observations included with these data are too far away from the Lite Yard Site to be associated with it. Thus, the commenter appears to suggest that this additional information may make precise definition of the site difficult and to take issue with the accuracy of EPA s delineation of the site included in the HRS documentation record. This response will address site definition. Section 3.3 below will address association of the data to the Lite Yard Site in more detail. In response, EPA acknowledges that preliminary data was available from As the HRS documentation record must be a legally defensible document, EPA could not use the preliminary data generated by the Agency as the data had not been validated and the usability of the data had not been determined when the 2006 HRS documentation record was completed. The new data does not change the HRS score and is not needed to further support that score, so EPA elected to proceed to finalize the site and begin urgently needed action rather than incorporate the new data and delay finalizing the site. The commenter s purpose appears to be related to attribution and ultimately liability, claiming others are responsible for the contamination and hence are liable. In addition, expanding the extent of the area of observed contamination will result in an increase in the site score, and thus would not change the listing decision. As stated on page 4 of the HRS documentation record at proposal, the maximum value for the soil exposure pathway is 100, and this site scored on the soil pathway. An increase in the number of actually contaminated targets would increase the overall site score from to a maximum of 50. Sections 3.3 and Section 3.4 below will address attribution and liability; the HRS does not assign liability. Furthermore, the SMRSC site has been defined in accordance with the terms of the HRS. According to Section 1.1 of the HRS, a site is defined as an area where a hazardous substance has been deposited, stored, disposed, or placed, or has otherwise come to be located. Such areas may include multiple sources and may include the area between sources. According to pages of the HRS documentation record, SMRSC is preliminarily defined by the residential properties located in proximity to the Lite Yard. An area of observed contamination was delineated based on analytical results for surface soil samples 2

12 collected from residential yards and within 200 feet of residences. All soil samples with arsenic concentrations greater than or equal to three times the background concentration were considered to be an area where a hazardous substance had been deposited, disposed, or placed, or had otherwise come to be located. Moreover, it is not necessary to precisely define the site for HRS scoring purposes. Similar to the definition of site in the HRS, CERCLA Section 101(a) defines a facility as the site where a hazardous substance has been deposited, stored, placed, or otherwise come to be located. The come to be located language gives EPA broad authority to clean up contamination when it has spread from the original source. As EPA stated on March 31, 1989 (54 FR 13298): HRS scoring and the subsequent listing of a release merely represent the initial (emphasis added) determination that a certain area may need to be addressed under CERCLA. Accordingly, EPA contemplates that the preliminary description of facility boundaries at the time of scoring will need to be refined and improved as more information is developed as to where the contamination has come to be located; this refining step generally comes during the RI/FS stage. In addition, the issue of site definition is discussed in Section F of the proposed rule (71 FR 56433, September 27, 2006). It states: [w]hen a site is listed, the approach generally used to describe the relevant release(s) is to delineate a geographical area (usually the area within an installation or plant boundaries) and identify the site by reference to that area. As a legal matter, the site is not coextensive with that area, and the boundaries of the installation or plant are not the boundaries of the site. Rather, the site consists of all contaminated areas within the area used to identify the site, as well as any other location to which contamination from that area has come to be located, or from which that contamination came. Following the listing on the NPL, an RI/FS may be completed and a remedial action may be selected. Until the investigation process has been completed and a remedial action (if any) selected, EPA generally does not attempt to estimate the full extent of contamination at the site, or describe the ultimate dimensions of the NPL site. Even during, or following, a remedial action (e.g., the removal of buried drums), EPA may find that the contamination has spread further than or not as far as previously estimated, and the known area of the site may be correspondingly expanded or reduced. 3.3 Other Potential Sources The Trust made comments stating that EPA has not fully considered other plausible and likely sources of arsenic to residential soil other than the Reade operations at the Lite Yard Site from 1938 to 1963, including emissions from a municipal solid waste combustor and an iron foundry, and homeowner application of fertilizers, pesticides, and herbicides, and use of chemically treated wood or wood mulch. Specifically, the Trust commented that there are at least two other potential sources of arsenic in the immediate vicinity of the Site: the former City Municipal Solid Waste (MSW) Combustor which closed in the 1970s, and the Smith Foundry which has reportedly been in operation for 80 years (both pre-dating ENVIROFACTS). The Trust suggests that these are potential point sources of arsenic. They commented that particularly in older neighborhoods, the historical individual application of lawn chemicals and use of CCA-treated wood or wood mulch can cause elevated concentrations in surficial soil. 3

13 They further commented that the presence of some samples located up to one mile from the Lite Yard Site still showing arsenic at greater than 95 mg/kg suggests that there are other sources. In response, EPA has properly established that at least some portion of the release is attributable to the site. HRS Section 2.3, Likelihood of release, requires that some portion of the release must be attributable to the site. HRS Section 5.0.1, General considerations (Soil Exposure Pathway), reiterates that a hazardous substance attributable to the site is present at a concentration significantly above background levels for the site to establish observed contamination. These requirements were met in the HRS documentation record as proposed for SMRSC. It is not a requirement that all of the contamination in the soil be attributable to the site. Two steps are generally involved in establishing attribution of a release to a site. Attribution generally involves demonstrating that the hazardous substance used to establish an observed release can be associated with the site and that the site contributed at least in part to the significant increase in the concentration of the hazardous substance. In the HRS documentation record as proposed, EPA established that the released substance is associated with the site (see pages 12 through 26 of the HRS documentation record as proposed). According to a deposition of Mr. Musselman, an employee of Reade, Reade used chemicals such as chlorates; borates; arsenic; and 2,4-D in the formulation of pesticides and herbicides.... Powdered arsenic trioxide was generally delivered to the facility on a hopper bottom railroad car. Significant volumes of this very light, powdered arsenic trioxide would spill onto the ground during the unloading process. Reade employees would attempt to sweep up the powdered arsenic trioxide, but some of the material would be dispersed in the air, depending on the wind direction and speed (Reference 26 of the HRS documentation record and page 24 of the HRS documentation record). Also described on page 24 of the HRS documentation record, Employee foot and parking lot traffic; vehicle traffic on unpaved roads; heavy equipment operation; wind aided migrations; maintenance and operational activities related to hoses and pipelines; building construction, maintenance or demolition would further aid, disturb and distribute the powdered arsenic that had been spilled and dispersed. In response, as mentioned above in Section 3.3, EPA has been unable to identify any other sources of the arsenic. In addition, the commenter provides no evidence that the potential sources it suggests are actually contributing arsenic to the SMRSC. Therefore, at least some portion of the release is attributable to the site is established by the presence of arsenic at the Lite Yard and the potential for this arsenic to become dispersed in the air (see page 24 of the HRS documentation record as proposed). It is clear that, and the Trust did not challenge, that the released substance arsenic is associated with the site. In the attribution section of the HRS documentation record as proposed (pp ), EPA points out that arsenic was detected in soil on the Lite Yard facility at concentrations as high as 18,000 24,000 mg/kg, and arsenic-based materials and raw materials were handled at this facility from 1938 through at least In fact, the Trust argues that the site impacts continued until While the Trust points to other potential sources as well, it has not provided any specific evidence connecting these potential sources to the contamination. EPA s investigation also failed to produce any evidence connecting any other specific sources to the contamination (p. 24). This comment does not result in a change in the site score. It instead goes to issues that may arise in defining the final scope and boundaries of the site that will be addressed after listing. See the liability discussion below. 3.4 Liability The Trust made a general comment and a subsequent specific comment 2, on page 2, that in relying upon results from a U.S. Borax-financed air model of site emissions, the [EPA] has not considered the plausible scenario that the U.S. Borax operations between 1963 and 1968 are also an additional source of arsenic contamination to the SMRSC Site. Proper identification of potentially responsible parties (PRPs) is 4

14 necessary, as these parties will be called upon to contribute to the funding of the ongoing investigation and remediation of the SMRSC site. As mentioned above in Section 3.3, the Trust asserted that EPA has not fully considered other plausible and likely sources of arsenic to residential soil other than the Reade operations at the Lite Yard Site from 1938 to 1963, including emissions from a municipal solid waste combustor and an iron foundry, and homeowner application of fertilizers, pesticides, and herbicides, and use of chemically treated wood or wood mulch. In response, it is clear that the comment asks EPA to consider these additional sources of arsenic rather than arguing that they are the only source of arsenic for the SMRSC site. Thus, EPA will consider these potential sources during characterization of the site following listing. In the attribution section of the HRS documentation as proposed (p. 24), EPA states It is possible that U.S. Borax may have continued to import powdered arsenic trioxide to the Lite Yard facility. Any contribution by U.S. Borax could only increase the amount of arsenic releases from the Lite Yard property. EPA has not determined if the municipal solid waste combustor, an iron foundry, and homeowner application of fertilizers, pesticides, and herbicides, and use of chemically treated wood or wood mulch are additional sources of arsenic contamination to the SMRSC site. These comments have not, moreover, presented any evidence demonstrating any attribution to these potential sources. These comments therefore do not result in a change in the site score. If the Trust has additional supporting information that U.S. Borax, the municipal soil waste combustor, an iron foundry, and homeowner application of fertilizers, pesticides, and herbicides, and use of chemically treated wood or wood mulch are (an) additional source(s) of arsenic contamination, the Agency can consider this information at any time during the Superfund process, usually following listing and completion of further investigations. Further, placement of a site on the NPL does not create, establish, or assign liability to any party. Liability and financial responsibility are addressed in a different phase of the Superfund process. 3.5 Observed Release: Attribution The Trust asserted that EPA has not proposed a method, either analytical or statistical, to differentiate between impacts from the Lite Yard Site and all of the other inputs of arsenic to residential soil. (second paragraph, p. 1). They commented that preliminary data from 2006 expanded the area of observed contamination to approximately one mile away from the former Lite Yard Site and suggested that the ongoing investigation must determine whether these observations at such great distances from the Lite Yard Site are related to former Lite Yard activities at all. The Trust further commented that redevelopment over time could have caused isolated pockets of clean soils, but the overall pattern of contamination decreasing exponentially in the predominant summer downwind direction should still be evident if the former Lite Yard Site is the primary source of arsenic in surficial residential soils. Based on the results of the 2006 investigation, this pattern is not evident. In fact, the pattern more closely resembles isolated pockets of contaminated soils, as one might expect with small, localized sources of contamination. In response, as mentioned above in Section 3.3, EPA has properly established that at least some portion of the release is attributable to the site. It is clear that, and the Trust does not challenge that the substance in the release arsenic- is associated with SMRSC. In addition, the Trust provides no evidence that the 5

15 potential sources it suggests are actually contributing arsenic to the SMRSC. Therefore, these comments do not result in a change in the site score. They instead go to issues that may arise in defining the final scope and boundaries of the site that will be addressed after listing. If the Trust has a method to differentiate between impacts from the Lite Yard facility and other inputs of arsenic, the Agency can consider this information at any time during the Superfund process, usually following listing and completion of further investigations. In addition, EPA, as part of the RI/FS, will determine whether these observations at greater distances from the Lite Yard Site can be attributed at least in part to former Lite Yard activities. 3.6 NPL Site Narrative The Trust quoted the following from the proposed listing s Fact Sheet [t]he patterns established in the residential soil sampling suggest that windblown deposition from the CMC Heartland Lite Yard Property may be responsible for the elevated levels of arsenic in the surrounding neighborhood. The trust then asserted that since the highest density of soil samples above 95 mg/kg (from block S7E04), is located southeast (upwind in summer) approximately one mile from the Lite Yard Site, there appears to be a discrepancy in the working hypothesis of windblown deposition from the Lite Yard Site. Individual homeowner s historical application of fertilizers, herbicides, pesticides and use of potentially contaminated wood and mulch could be an alternate explanation for the erratic observation of high and low concentrations of arsenic in surficial soil. In response, the NPL Site Narrative is a one page fact sheet which summarizes information from the HRS documentation record. The HRS documentation record established that at least some portion of the release is attributable to the SMRSC site and that EPA has no evidence to attribute the arsenic to any other specific sources. The conceptual site model was used as a tool to explain the potential source of arsenic; it was not used to score the SMRSC site. The SMRSC site scores on the arsenic in the residential yards and the number of people living in the homes adjacent to the yards. The HRS documentation record shows whether the soil contamination in the residential yards and within 200 feet of the residences are three times the background concentration and pose sufficient relative threat to warrant placement on the NPL. Therefore, the site scores independent of any information obtained from the model. To conclude, the HRS documentation record does not prove or disprove conceptual site models. Regarding the comment upwind in summer, this was the prevailing wind direction during the summer months (Ref. 24, pp. 8, 9, 10, 11 of the HRS documentation record). Reference 24 of the HRS documentation record also shows that the wind moved in all directions during the summer months as well as during the other nine months of the year. The wind direction is information that was used as a tool in the working hypothesis. This information was not used to determine the site score. Therefore, the site scores independent of any information obtained from the models. These comments do not result in a change in the site score. 3.7 Other Comments The Trust asserted that EPA suggested that it may expand its area of investigation even farther based on the results of the 2006 investigation. (third paragraph, p. 5) The Trust commented that Based on the conceptual model of fugitive emissions from the Lite Yard Site, the farther away a sample is collected, the less likely it is that arsenic detected can be attributed to the Lite 6

16 Yard Site. (third paragraph, p. 5). They asserted that without a statistical or analytical forensic procedure to link arsenic detected in residential soil to former Lite Yard Site operations, the area of investigation may continue to grow, and EPA may be unable to define true site boundaries (third paragraph, p. 5). They suggested that EPA consider other potential sources of arsenic as opposed to limiting the identified source of arsenic contamination to the SMRSC Site to only the activities of Reade (third paragraph, p. 5). In response, regarding the site definition, as stated previously in Section 3.2, until the investigation process has been completed and a remedial action (if any) selected, EPA generally does not attempt to estimate the full extent of contamination at the site, or describe the ultimate dimensions of the NPL site. Even during, or following, a remedial action (e.g., the removal of buried drums), EPA may find that the contamination has spread further than or not as far as previously estimated, and the known area of the site may be correspondingly expanded or reduced. In addition, EPA, as part of the RI/FS, will determine whether these observations at such great distances from the Lite Yard Site can be attributed at least in part to former Lite Yard activities. Also, if the Trust has additional supporting information that U.S. Borax, the municipal soil waste combustor, an iron foundry, and homeowner application of fertilizers, pesticides, and herbicides, and use of chemically treated wood or wood mulch are an additional source(s) of arsenic contamination, the Agency can consider this information at any time during the Superfund process, usually following listing and completion of further investigations. These comments do not result in a change in the site score. They instead go to issues that may arise in defining the final scope and boundaries of the site and identifying liable parties that will be addressed after listing. 4. Conclusion The original HRS score for this site was Based on the above response to comments, the score remains unchanged. The final scores for the South Minneapolis Residential Soil Contamination are: Ground Water: Not Scored Surface Water: Not Scored Soil Exposure: Air: Not Scored HRS Score: