United States Environmental Protection 1200 Pennsylvania Avenue, N.W. Agency Washington, D.C. 20460 September 2010 Office of Solid Waste and Emergency Response 

# Support Document for the Revised National Priorities List Final Rule – General Dynamics Longwood

# Support Document for the Revised National Priorities List Final Rule General Dynamics Longwood September 2010

Site Assessment and Reme dy Decisions Branch Office of Superfund Remediati on and Technology Innovation Office of Solid Waste and Emergency Response U.S. Environmental Protection Agency Washington, DC 20460Table of Contents Executive Summary ............................................................................................................................... .... iv

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25 29 30 Introduction ................................................................................................................................................. Background of the NPL .......................................................................................................................... Development of the NPL ........................................................................................................................ Hazard Ranking System ........................................................................................................................ Other Mechanisms for Listing ............................................................................................................. Organization of this Document ........................................................................................................... Glossary ................................................................................................................................................ 1. List of Commenters and Correspondence ........................................................................................ 2. Site Description ................................................................................................................................... 3. Summary of Comments ...................................................................................................................... 3.1 Support for Listing and Other Non-opposition Comments .................................................. 3.2 Site Name ............................................................................................................................... .... 3.3 Extent of the General Dynamics Longwood Site .................................................................... 3.4 Liability ............................................................................................................................... ....... 3.5 Purpose of NPL ......................................................................................................................... 3.5.1 Further Investigation

........................................................................................................... 3.5.2 Remedial Actions

................................................................................................................ 3.5.3 Public Notification/Participation

......................................................................................... 3.5.4 Potentially Responsible Party Notification

......................................................................... 3.6 Rationale for Listing ................................................................................................................. 3.7 Proper Notice ............................................................................................................................. 3.8 Biased Scoring ........................................................................................................................... 3.9 Scoring Other Pathways ........................................................................................................... 3.10 Source No. 1 and Associated Observed Releases .................................................................... 3.11 Description of Pathway ............................................................................................................. 3.11.1 Consideration of Pump-and-Treat System

.......................................................................... 3.11.2 Surficial Aquifer Clay Layer

...............................................................................................General Dynamics Longwood NPL Listing Support Document September 2010

3.12 Identification of a Source and Origin of Source Contamination .......................................... 32 38 38 40

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99 3.12.1 Evidence of Contamination

................................................................................................. 3.12.2 Evidence of Migration from Former Vapor Degreaser

....................................................... 3.12.3 Contamination from Upgradient Ground Water Releases

.................................................. 3.13 Likelihood of Releases – Sources ............................................................................................. 3.14 Source Description .................................................................................................................... 3.15 Source Type ............................................................................................................................... 3.16 Source Background ................................................................................................................... 3.17 Associating Substances with Source No. 2 .............................................................................. 3.18 Likelihood of Release - Background ........................................................................................ 3.18.1 Effects of Pump-and-Treat System

..................................................................................... 3.18.2 Selection of Background Samples

...................................................................................... 3.18.3 Temporal Differences Due to Flow Rate

............................................................................ 3.19 Likelihood of Release – Attribution ........................................................................................ 3.19.1 Consideration of Degradation Products

.............................................................................. 3.19.2 Ground Water Flow Direction

............................................................................................ 3.19.3 Contaminant Migration Direction

....................................................................................... 3.19.4 Conclusions from Previous Studies

.................................................................................... 3.19.5 Absence of Significant Soil Contamination

........................................................................ 3.20 Waste Characteristics ............................................................................................................... 3.20.1 Toxicity/Mobility

................................................................................................................ 3.20.2 Waste Quantity

.................................................................................................................... 3.21 Targets ............................................................................................................................... ........ 3.22 Revised Site Score ..................................................................................................................... 4. Conclusion ............................................................................................................................... .......... Attachment 1 Letter from EPA to General Dynamics, February 10, 2009 Attachment 2 Theoretical Ground Water Capture Rate from RW-2A Attachment 3 Reviewed Upgradient Samples

iiiGeneral Dynamics Longwood NPL Listing Support Document September 2010 

## 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 re leases of hazardous substances, pollutants, or contaminants throughout the United States. An orig inal National Priorities List (NPL) was promulgated on September 8, 1983 (48 FR 40658). CERCLA requir es that EPA update the list at least annually. This document provides responses to public comments received on the General Dynamics Longwood site, proposed on April 9, 2009 (74 FR 16162). This site is being adde d to the NPL based on an evaluation under EPA’s Hazard Ranking System (HRS) in a final rule published in the Federal Register in September 2010.

ivGeneral Dynamics Longwood NPL Listing Support Document September 2010



## Introduction This document explains the rationale for adding the General Dynamics Longwood site in Longwood, Florida, to the National Priorities List (NPL) of uncontrolled hazardous waste sites and provides responses to public comments received on this site lis ting proposal. The EPA proposed this site to the NPL on April 9, 2009 (74 FR 16162). 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 2010. 

### Background of the NPL In 1980, Congress enacted the Comprehensive Enviro nmental Response, Compensation, and Liability Act (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 the Superfund Amendments and Reauthorization Act (SARA), Public Law No. 99-499, stat., 1613 et seq. To implement CERCLA, EPA promulgated the revised National Oil and Hazardous Substances Polluti on Contingency Plan (NCP), 40 CFR Part 300, on July 16, 1982 (47 FR 31180), pursuant to CERCLA Section 105 and Executive Order 12316 (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 guid elines and procedures needed to respond under CERCLA to releases and threatened releases of hazard ous 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 rel eases 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). Remedial action is generally long-term in nature and involves response actions that are consistent with a permanent remedy for a release (CERCLA Section 101). 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. EPA promulgated the HRS 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, 1991. 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 th e known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout th e 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 lis ting 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 4, 2010 (75 FR 9790). The Agency also has published a number of proposed rulemakings to add sites to the NPL. The most recent pr oposal was on March 4, 2010 (75 FR 9843).

vGeneral Dynamics Longwood NPL Listing Support Document September 2010 

### Development of the NPL The primary purpose of the NPL is stated in the le gislative history of CERCLA (Report of the Committee on Environment and Public Works, Senate Repor t No. 96-848, 96th Cong., 2d Sess. 60 [1980]). The priority list serves primarily informa tional 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 govern ment actions will be necessary in order to do so, and these acti ons will be attended by all appropriate procedural safeguards. The NPL, therefore, is primarily an informational a nd management tool. The identification of a site for the NPL is intended primarily to guide EPA in determ ining 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 prio rity sites among the known releases or threatened release of hazardous substances, pollutants, or c ontaminants, 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 cer tain 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 inform ation from initial, limited investigations -- the preliminary assessment and site inspection -- to assess th e 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 inform ation 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 hi ghest 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/feasibilit y 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, b ased on conditions at the site. The factors are grouped into three categories. Each category has a maximum value. The categories are:

• likelihood that a site has released or has the potential to release hazardous substances into the environment;

viGeneral Dynamics Longwood NPL Listing Support Document September 2010

• characteristics of the waste (toxicity and waste quantity); and

• people or sensitive environments (targets) affected by the release. Under the HRS, four pathways can be scored for one or more threats as identified below:

• Ground Water Migration (S gw ) - drinking water

• Surface Water Migration (S sw ) The following threats are evaluated for two separate migration components, overland/flood migration 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 prescrib ed guidelines, they are combined using the following root-mean-square equati on to determine the overall site score (S), which ranges from 0 to 100 :



### 4 S + S + S + S = S 2 a 2 s 2 sw 2 gw

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 There are two mechanisms other than the HRS by whic h sites can be placed on the NPL. The first of these mechanisms, authorized by the NCP at 40 CFR 300. 425(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 300.425(c)(3), allows listing a site if it meets the following three 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

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• 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 contains EPA responses to s ite-specific public comments received on the proposal of the General Dynamics Longwood site on April 9, 2009 (74 FR 16162). The site discussion begins with a list of commenters, followed by a site description, a summary of comments, and Agency responses to each comment. 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: 1,1-DCE 1,1-dichloroethylene 1,1,1-TCA 1,1,1-trichloroethane Agency U.S. Environmental Protection Agency AOC Administrative order by consent ATSDR Agency for Toxic Substances and Disease Registry bls below land surface CERCLA Comprehensive Environmental Response, Compensation, and Liability Act of 1980, 42 U.S.C. Sections 9601 et seq ., also known as Superfund CFC – 113 1,1,2-trichloro-1,2,2-triflourethane CFR Code of Federal Regulations EPA U.S. Environmental Protection Agency FDEP Florida Department of Environmental Protection FR Federal Register FS Feasibility study GAFRI Great American Financial Resources, Inc. HRS Hazard Ranking System, Appendix A of the NCP HRS score Overall site score calculated using the Hazard Ranking System; ranges from 0 to 100 ID Identification number MDL Method detection limit MW Monitoring well μ g/kg Microgram per kilogram μ g/L Microgram per liter NCP National Oil and Hazardous Substances Po llution Contingency Plan, 40 C.F.R. Part 300

viiiGeneral Dynamics Longwood NPL Listing Support Document September 2010

ix NPL National Priorities List, Appendix B of the NCP PCE Perchloroethylene (also known as Tetrachloroethylene) PRP Potentially responsible party RI Remedial investigation RW Remedial well SAA Superfund Alternative Approach SARA Superfund Amendments and Reauthorization Act SB Subsurface soil sample SEC Sprague Electric Company TDL Target distance limit TCE Trichloroethylene VOC Volatile organic compoundsGeneral Dynamics Longwood NPL Listing Support Document September 2010 

## 1. List of Commenters and Correspondence 1

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 EPA-HQ-SFUND-2009-0067-0004 Corres pondence, dated December 8, 2008, to J. I. Palmer, Regional Administrator, USEPA, Region 4 from Michael W. Sole, Secretary, Florida Department of Environmental Protection EPA-HQ-SFUND-2009-0067-0005 Comment, dated June 4, 2009, submitted by Steven M. Siros, Jenner & Block LLP on behalf of General Dynamics Corporation EPA-HQ-SFUND-2009-0067-0005.1 Comment attachment , posted June 17, 2009, submitted by Steven M. Siros, Jenner & Block LLP on behalf of General Dynamics Corporation EPA-HQ-SFUND-2009-0067-0006 Comment dated June 4, 2009, submitted by Brown and Caldwell on behalf of General Dynamics Corporation EPA-HQ-SFUND-2009-0067-0006.1 Comment attachment , posted June 25, 2009, submitted by Brown and Caldwell on behalf of General Dynamics Corporation 

## 2. Site Description The General Dynamics Longwood site as detailed in the HRS documentation record at proposal is located in Longwood (Seminole County), Florida, and consists of two soil sources contaminated with chlorinated ethenes and an observed release of chlorinated ethenes to ground water. The site score is based on this contamination of the ground water migration pathway and potential c ontamination of nearby drinking water wells. The sources are located on a property formerly leased by General Dynamics (hereafter referred to as the General Dynamics property). Figure 1 below shows the general site area.

1General Dynamics Longwood NPL Listing Support DocumentSeptember 2010Figure 1: General Site AreaNote: The General Dynamics facility area and the SEC facility area are shown here as bounded byproperty boundaries.2General Dynamics Longwood NPL Listing Support Document September 2010

Geology/Hydrology 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 Ground water in the Seminole County, Florida area exists in two distinct units: the surficial aquifer and the deeper Floridan aquifer. These aquifers are sep arated by an intermediate confining unit (Hawthorn Group); however, the Hawthorn Group is not continuous; and is not present directly north (about 240 feet) of the General Dynamics property. The Floridan aquifer system is the principal source of ground water in east-central Florida. The surficial aquifer is unconfined and consists mainly of lenses of fine to medium quartz sand with varying amounts of shell and clay. The deposits are discontinuous and their lithology and texture can vary over short distances. Previous investigations at the General Dynamics and the Sprague Electric Company (SEC) property immediatel y to the south divide the surficial aquifer into two water bearing zones, A-zone a nd B-zone. The A-zone (upper surfi cial aquifer) and B-zone (lower surficial aquifer), are separated by a discontinuous cl ay layer (A/B clay). The A/B clay layer ranges in depth from 13.5 feet below land surface (bls) to 32 f eet bls across the General Dynamics property and is believed to be absent in the northwestern portion of th e property. The ground water flow direction in the A and B-zones is north to northeast across the Gene ral Dynamics property. Figure 2 below characterizes the general subsurface structures belo w the General Dynamics Longwood site.

3General Dynamics Longwood NPL Listing Support DocumentSeptember 2010Figure 2: General Subsurface Structures at the General Dynamics Longwood SiteSURFICIALAQUIFERHAWTHORNEGROUP(DISCONTINUOUS)FLORIDANAQUIFERDISCONTINUOUS CLAY LAYERSEPARATING SURFICIALAQUIFER INTO UPPERSURFICIAL (A-ZONE) ANDLOWER SURFICIAL (B-ZONE)42434445464748495051525354555657585960616263646566Note: Subsurface layers shown represent the general stratigraphic layers below the GeneralDynamics Longwood site. Certainlayers are documented as discontinuous below the site, such as theHawthorne Group and the surficial aquifer clay layer. Not toscale.4General Dynamics Longwood NPL Listing Support Document September 2010

Site History 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 Tenants at the General Dynamics property included Dy natronics (1959 to 1965); General Dynamics Corp. (1966 to 1978); Stromberg-Carlson, a subsidiary of General Dynamics Corp. (1979 to 1982); General Dynamics Land Systems, a subsidiary of General Dy namics Corp. (1983); Lexar Corporation and United Technologies Comm. Co. (1984 to 1985); and Lexar Corporation, UTCC, and Telex Computer Products (1986 to 1988). Gould Publications purchased the prope rty in 1993. Sunshine Publications of Florida (formerly Gould Publications) conducted printing and publication operations and currently owns the property.

Limited information exists on the operational history at General Dynamics. The property consists mostly of paved parking and unpaved grass areas. Structur es on the General Dynamics property include three large buildings (Building Nos. 1, 2, and 3) among smaller buildings. Building 1 contained the lobby, plant manager’s office, and personnel. Building 2 contained an engineering drafting and test area. Building 3 contained the manufacturing area, PC soldering, storage area, and a vapor degreaser. At an unspecified time, trichloroethylene 1 (TCE) was stored in an above ground storage tank located outside Building 3 near the vapor degreaser. Additional va por degreasers were located throughout the facility; however, the location of these degreasers as well as th e solvents used are unknown. A building which contained a maintenance shop is located to the northeast of Building 1. A shed was located to the east of Building 3 which held 55 gallon cont ainers of TCE. Painting and pla ting occurred east of Building 1.

General Dynamics manufactured printed circuit boards. After assembly, a cleaning process was used to remove residues from the circuit boards. Chemicals ge nerally used in the industry for the cleaning process include chlorinated solvents such as TCE, 1,1,1- trichloroethane (1,1,1-TCA), perchloroethylene 2 (PCE), and 1,1,2-trichloro-1,2,2-trifluor ethane (CFC-113), as well as various non-chlorinated solvents, such as acetone and alcohol. According to a previous employee at General Dynamics, the manufacture of printed circuit boards included a step requiring a vapor degreaser which is documented to have used chlorinated solvents.

The property bordering the General Dynamics Longwood site on the south was owned by Sprague Electric Company (SEC) from 1959 to 1992. From about 1959 to December 1964, a portion of the SEC property was owned by Dearborn. Both SEC and De arborn manufactured film capacitors at the SEC property. Film capacitors were assembled and then cleaned in a vapor degreaser; the chemicals TCA and

1 Trichloroethylene is also known as TCE and trichloroethene.

2 Perchloroethylene is also know n as PCE and tetrachloroethlyene 5General Dynamics Longwood NPL Listing Support Document September 2010

TCE were used as cleaning agents in the vapor de greaser. TCA, TCE, and their degradation products have been detected in sources at the SEC property and documented in ground water in the surficial and Floridan aquifers underlying the SEC property. In January 1986 and December 1987, the SEC property entered into a State of Florida Consent Order that was approved and monitored by the Florida Department of Environmental Protection (FDEP). 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 In July 1997 a ground water recovery/treatment sy stem was initiated by Great American Financial Resources, Inc. (GAFRI: legal successor to SEC) to minimize the amount of gr ound water contaminants migrating off the SEC site (in accordance with State of Florida Consent Order, dated January 9, 1986, and Consent Order, dated December 8, 1987, and as a pproved and monitored by the FDEP). The system consisted of three horizontal wells in the surficial a quifer A-zone and one vertical well in the surficial aquifer B-zone; the A-zone wells were meant to captu re and treat contaminants in the A-zone, and the Bzone well was meant primarily to limit the possibilit y of downward migration of contaminants from the B-zone into the Floridan aquifer. The A-zone wells run horizontally east-west, and are located along the northern SEC property line; the wells are named RW-1A (running approximately the western one-third of the property line), RW-2A (running approximately the eastern one-third of the property line), and RW-3A (running approximately the central one-third of the pr operty line). The vertical B-zone well, named RW1B lies roughly at the eastern end of RW-1A. The treatment system associated with the wells is made up of an air stripper with carbon absorption. Effluent from the system is discharged to the unnamed ditch that runs between the SEC site and the General Dynamics Longwood site. The approximate operation history for the A-zone horizontal wells is as follows:

• July 1997 – Initiation of pumping from RW-1A, RW-2A, and RW-3A

• December 1998 – All three wells shut down

• May 2000 – RW-2A restarted

• January 2002 – RW-2A shut down

• February 2003 – RW-2A restarted

• September 2008 – RW-2A shut down

In 2003, the lead agency for cleanup activities was tr ansferred to EPA and an administrative order by consent (AOC) for the SEC site was signed and approved by EPA in June 2004. Because it was recognized that ground water contamination was migr ating northward with ground water flow from under the SEC property to under the General Dynamics pr operty, this AOC originally included the General Dynamics property. The SEC site is currently be ing addressed under the Superfund Alternative Approach

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(SAA), a process in which remedial investigations and actions are carried out just as with normal NPL sites, meeting the same cleanup criteria, but avoiding the NPL listing process. 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 However, during several investigations from 2001 th rough 2007, it became clear that sources of chlorinated ethenes were present on the General Dyna mics property that were not associated with the SEC site, and that some portion of the ground wa ter contamination beneath the General Dynamics property was linked to these sources. Thus, EPA referred the General Dynamics Longwood site for NPL listing.

Sources As detailed in the HRS documentation record at pro posal, Source No. 1 was identified as subsurface soil contaminated with TCE located in the southwestern portion of the General Dynamics property. Source No. 2 consists of subsurface soil contaminated with 1,1-dichloroethylene (1,1-DCE) underlying the area of the former vapor degreaser on the General Dynamics property.

Observed Release/Attribution Two separate observed releases by chemical analysis to ground water were established in the HRS documentation record at proposal by ground water contamination detected in several samples at various depths underlying and downgradient of Source No . 1 and Source No. 2. Background ground water samples showed that these contaminated grou nd water samples contained hazardous substances significantly greater than background levels. In selec ting background and contaminated samples used to substantiate observed releases, vari ous parameters (e.g., depth, ground water flow direction and treatment system effects on flow and hydrology/geology) were taken into account to appropriately associate release samples with the sources and adequately screen out any influence upgradient SEC site contamination migration might have. Hazardous substances detected in observed release sampl es associated with Source No. 1 included TCE and several of its degradation products (cis-1,2-DCE, trans-1,2-DCE, 1,1-DCE, and vinyl chloride). Contaminants detected in ob served release samples associated with Source No. 2 included TCE, cis-1,2-DCE, and 1,1-DCE.

Targets The HRS documentation record at proposal scored near by drinking water wells as targets subject to potential contamination by the observed releases attribut ed to the site. Drinking water wells within a 4- mile radius of the site are considered subject to pot ential contamination. Finally, a wellhead protection

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area factor value was assigned to take into account the presence of a wellhead protection area within a 4- mile radius of the site. 165 166 167 168

169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 

## 3. Summary of Comments

Michael W. Sole submitted a comment on behalf of th e FDEP, and cited the degree of contamination at the site in support of listing the General Dynamics Longwood site on the NPL.

Steven M. Siros of Jenner & Block LLP submitted comments on behalf of General Dynamics in opposition to the listing. General Dynamics asserted that the listing of the General Dynamics Longwood site is “contrary to the intent and core purpose of the NPL,” arguing that site investigation, remediation, public notification, and potentially responsible part y (PRP) notification is already addressed by the 1987 FDEP consent decree and 2004 EPA AOC for the nearby SEC site.

General Dynamics stated that “no evidence has b een presented to show that General Dynamics contaminated the Gould [General Dynamics Longwood] site, and no evidence has been presented that anyone other than the SEC contaminated the Gould [General Dynamics Longwood] site.” Throughout its comments, General Dynamics used the name Gould to describe the site (referring to Gould Publications, a recent owner of the property), noting that references in the HRS documentation record used the name at the time they were written.

General Dynamics asserted that both FDEP and EPA had recognized that the General Dynamics Longwood site had been contaminated by the upgrad ient SEC site, and yet EPA inexplicably shifted focus to investigation of releases at the Genera l Dynamics Longwood site in 2007. General Dynamics claimed that EPA’s notification of General Dynamics regarding these investigations was not timely. General Dynamics further argued that, in spite of the fact it was complying with EPA’s request to perform an RI, EPA moved forward with the NPL listing process.

General Dynamics stated that TCE was the only solv ent established to have been used in the vapor degreaser at the site; General Dynamics specifically took issue with the mention of PCE in the HRS documentation record and asserted there is no indicati on PCE was used at the site. Citing historical information and employee depositions regarding facili ty operations, General Dy namics concluded that “there is no evidence of actual releases of TCE (or any other solvent) to the soil or groundwater” at the site.

8General Dynamics Longwood NPL Listing Support Document September 2010

General Dynamics stated that the HRS documentation record contains “numerous technical errors and invalid assumptions,” and that correction of these would lead to an HRS score of zero. General Dynamics identified the following items as erroneous or invalid: 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 • impermissibly concluding that the contamin ants identified in Source Areas 1 and 2 were the result of releases from the Gould site

• incorrectly identifying 1, l-DCE as a primary breakdown product of TCE as opposed to a primary breakdown product of 1,1,1-TCA

• basing determinations of toxicity on the presence of a release of TCE in the absence of evidence that such a release ever occurred

• improperly calculating the size and quantity of alleged release of hazardous substances

• failing to properly account for the population potentially affected by contamination migrating from the Gould site.

Based on these comments, General Dynamics concluded that “listing the Gould [General Dynamics Longwood] site on the NPL would be arbitrary and capricious and an abuse of discretion.” General Dynamics requested that EPA “(1) not finalize the NPL proposal; (2) remove the Gould [General Dynamics Longwood] site from the list of proposed NPL sites; and (3) discontinue any further consideration of listing the Gould [General Dynamics Longwood] site on the NPL.”

Brown and Caldwell prepared technical comments on the General Dynamics Longwood site for General Dynamics in opposition to the listing. Brown and Caldwell asserted that EPA’s HRS documentation record was based on incorrect assumptions and that, if corrected, the accurate HRS site score would be

zero.

Brown and Caldwell stated that the HRS documentation record did not support that a solvent release took place at the General Dynamics Longwood site, claiming the following reasons:

• Prior investigations show that the SEC site cau sed the contamination at the General Dynamics Longwood site.

o Soils composing the sources at the General Dynamics Longwood site are not soil but saturated aquifer material, and they have been contaminated by hazardous substances migrating via ground water from the SEC site.

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o 1,1-DCE (the contaminant in Source No. 2) is a primary degradation product of 1,1,1- TCA, but only a minor degradation product of TCE; use of 1,1,1-TCA has been established at the SEC site, but not at the General Dynamics Longwood site. 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 o The relatively high concentrations of 1,1-DCE in ground water beneath Source No. 2 coupled with the much lower concentrations found in Source No. 2 soils does not support a release from soil to ground water; rather, it is more likely the contaminants migrated from the SEC site.

• The FDEP has “previously acknowledged that cont amination in groundwater beneath the Gould [General Dynamics] property originated solely on the Sprague [SEC] site.”

• The geology of the area led to the migration of contaminants from SEC to the General Dynamics Longwood site. Brown and Caldwell asserted that EPA has not adequately evaluated:

o ground water flow rates and direction;

o impact of the SEC site pump-and-tr eat system on ground water flow; and

o the extent and slope of the A/B clay layer, and its ability to convey contaminants from the SEC site to the General Dynamics Longwood site.

• The site sources have been improperly identifie d. Brown and Caldwell specifically questioned the dimensions assigned to Source No. 1.

• Background samples have been incorrectly iden tified. Brown and Caldwell asserted that background and contaminated samples are in “the middle portions of groundwater contaminant plumes that originated on the Sprague propert y;” they claim that EPA has not accounted for physical and temporal complexities linked to ground water movement and the SEC site contamination.

• Source No. 1 and No. 2 are “[n]either an ‘[ o]bserved’ nor a ‘[p]otential’ release to [g]roundwater”. Brown and Caldwell asserted bot h sources are saturated soil within the water table and reflect contamination migrating in ground water from the SEC site. Brown and Caldwell also argued that past investigations do not support the HRS documentation record explanation of the origin for each source’s c ontaminants—that previous septic system analyses near Source No. 1 did not find contaminants, a nd Brown and Caldwell’s 2009 investigation of Building 3 and the floor beneath the vapor degreaser did not reveal any possible migration routes from the degreaser to the Source No. 2 soil below.

Brown and Caldwell stated that the HRS documentati on record used erroneous scoring factors. Brown and Caldwell argued that because the contamination at the General Dynamics Longwood site migrated from the SEC site, there is no release at the Genera l Dynamics Longwood site; the toxicity/mobility factor

10General Dynamics Longwood NPL Listing Support Document September 2010

used in HRS scoring for TCE is therefore incorr ect because TCE was not released at the General Dynamics Longwood site. By the same logic, Brown and Caldwell also claim that because there was no release, the hazardous waste quantity factor should be zero. 265 266 267 268 269 270 271 272 273 Brown and Caldwell stated that, because only a fractio n of the wells scored as targets subject to potential contamination are hydraulically downgradient of the site, EPA has overestimated the potential contamination factor value. 

### 3.1 Support for Listing and Other Non-opposition Comments

Comment : Mr. Michael W. Sole, Secretary, FDEP, wrote a letter to EPA Region 4 on behalf of FDEP in support of listing the General Dynamics Longwood site on the NPL. 274 275 276 Response : The General Dynamics Longwood site has been added to the NPL. Listing makes a site eligible for remedial action funding under CERCLA, and EPA will examine the site to determine what response, if any, is appropriate. Actual funding may not necessarily be undertaken in the precise order of HRS scores, however, and upon more detailed investiga tion may not be necessary at all in some cases. EPA determines the need for using Superfund monies for remedial activities on a site-by-site basis, taking into account the NPL ranking, State priorities, further site investigation, other response alternatives, and other factors as appropriate. 277 278 279 280 281 282 283 284 285 

### 3.2 Site Name

Comment : Both General Dynamics and Brown and Caldwe ll imply that the site name should include “Gould” instead of “General Dynamics.” Both st ated that the property at the General Dynamics Longwood site is currently owned by Gould Publications , and both refer to the site using the Gould name throughout their comments. General Dynamics also not es that this was EPA’s previous terminology used in reports prior to the HRS documentation record. 286 287 288 289 290 291 Response : The site name of General Dynamics Longwood has been retained. Neither CERCLA nor the NCP establishes a required procedure for assigning a site name to a proposed listing, and EPA considers it is reasonable to have named th e site General Dynamics Longwood. Since the primary purpose of an NPL listing is to inform the public that EPA has determ ined that the site warrants further investigation, EPA attempts to select the name that most clearly in forms the public as to where the site is, what appears to be the primary source(s) of the problems at the site, and/or considers assigning a geographic name. 292 293 294 295 296 297

11General Dynamics Longwood NPL Listing Support Document September 2010

EPA also attempts to select names that do not offe nd local sensitivities (see OSWER Directive 9345.1-08, Regional Quality Control Guidance for NPL Candidate Sit es, 12/26/91). EPA chose to name the site after the specific geographic location of the Longwood facility, and General Dynamics Corporation, which operated at the site from the mid-1960s to the early 1980s. General Dynamics’ previous operations are well-known with the local community. This offers a level of name-recognition that helps informs the community of the site. 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 EPA considers that the General Dynamics Longwood s ite’s present name reflects the general location of and at least one possible historic source of the 1,1- Dichloroethylene (DCE) release at the site. This hazardous substance is shown by the HRS documentation record to have been detected in Source No. 2 (soil under building No. 3 at the site) and in ground water beneath Source No. 2.

EPA also emphasizes that the name of the site does not in any way restrict the evaluation of the site, its sources, its releases, or extent of contamination to only the practices of the former General Dynamics Corporation. The HRS documentation record at propo sal on page 28 reflects the fact that other possible sources of 1,1-DCE at the site exist. As the Federal Register in which the General Dynamics Longwood site was proposed to the NPL (73 FR 51395, Section F) states, “the precise nature and extent of the site are typically not known at the time of listing.” EPA also expects to explore any and all areas of 1,1-DCE and other related solvent contamination associated with the site during post-lis ting investigation activities.



### 3.3 Extent of the General Dynamics Longwood Site 318

Comment : In several comments, General Dynamics a nd Brown and Caldwell ostensibly questioned whether or not the General Dynamics Longwood site is actually a separate site from the SEC SAA site. General Dynamics stated that “no evidence has b een presented to show that General Dynamics contaminated the Gould [General Dynamics Longwood] site, and no evidence has been presented that anyone other than the SEC contaminated the Goul d [General Dynamics Longwood] site.” General Dynamics claimed that EPA “agreed that the contam ination on the Gould [General Dynamics Longwood] site was the result of contaminant migration from the SEC Site.” General Dynamics asserted that in a 2004 AOC, EPA required GAFRI (legal successor to SEC) to “among other tasks, characterize the nature and extent of contamination at both the SEC and Gould [General Dynamics Longwood] sites. . . . Clearly, U.S. EPA included the Gould [General Dynamics Longwood] site because it recognized that contaminants were migrating from the SEC site ont o the Gould [General Dynamics Longwood] site.” 319 320 321 322 323 324 325 326 327 328 329 330 331 Brown and Caldwell stated that:

12General Dynamics Longwood NPL Listing Support Document September 2010

Previous Work Confirms that the Sprague Electric Site Has Contaminated the Gould Property [General Dynamics property] . . . As EPA acknowledges, ‘The SEC property, located hydraulically upgradient of the [Gould] property, is a known source of contamination’ and ‘The AOC signed and a pproved by EPA in June 2004 also includes the [Gould] property’ [quoting the HRS documentation record, page 53] . . . Previous investigative studies have shown this and have also generated raw data confirming that VOC contaminants detected at the Gould Property [General Dynamics property] are the result of these historic releases that were discovered in groundwater at the SEC site and traced northward to both the Gould Property [General Dynamics property] [emphasis in original comment] and offsite to the northwest across U.S. Highway 17-92. 332 333 334 335 336 337 338 339 340 341 342 Response : The General Dynamics Longwood site is a separat e site from the SEC site. However, because the commenters raised the issue of contamination fro m the SEC site potentially migrating into the Source 1 area of the General Dynamics Longwood site, EPA decided to drop Source 1 and its associated observed releases from the HRS evaluation. EPA be lieves this is reasonable because the HRS is primarily a screening tool for identifying sites that pose sufficient actual or potential risk to warrant further investigation. Questions concerning the extent of contamination will be investigated at the RI/FS stage of the Superfund process, and are not a factor in listing. As will be discussed further in section 3.22 of this document, the release from Source 2, by it self, is sufficient to qualify the General Dynamics Longwood site for the NPL with an HRS score of 50.00. Scoring Source 1 and its associated observed releases is not necessary to reach a sound listing d ecision and the HRS documentation record has been revised accordingly to document this rescoring. In light of this rescoring, EPA believes it is both reasonable and prudent to remove Source 1 from the HRS evaluation, rather than spend considerable resources to resolve the issues raised by the commenters at this pr eliminary stage in the Superfund process. Additionally, EPA’s decision to evaluate Source 2 on the General Dynamics Longwood site is consistent with prior correspondence to General Dynamics indicating the Agency’s concern about a source of contamination on the General Dynamics Lo ngwood site, independent fr om the SEC site. As EPA explained on page 2 of a letter to General Dy namics on August 27, 2008 (attached to the General Dynamics comment letter as Reference I), remedial investigations conducte d for the Sprague site indicated: 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 an additional source or sources of contam ination to the groundwater plume under investigation, as well as another, entirely di stinct groundwater plume. This new source area was located on the property owned by Gould Publications and was contributing a different contaminant from those found to be emanating from the Sprague Site.

This change however does not infer that the bounda ries of the site may not include releases due to General Dynamics in the Source No. 1 area and in other areas for which the investigation may be incomplete. Placing a site on the NPL is based on an evaluation, in accordance with the HRS, of a release

13General Dynamics Longwood NPL Listing Support Document September 2010

or threatened release of hazardous substances, polluta nts, or contaminants. However, the fact that EPA initially identifies and lists the releas e based on a review of contamination at a certain parcel of property does not necessarily mean that the site boundaries are limited to that parcel. 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 CERCLA Section 105(a)(8)(A) requires EPA to lis t national priorities among the known "releases or threatened releases" of hazardous substances; thus, the focus is on the release, not precisely delineated boundaries. Further, CERCLA Section 101(a) defi nes a “facility” as the “site” where a hazardous substance has been “deposited, stored, placed, or ot herwise 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.

The revised HRS (55 FR 51587, December 14, 1990) elaborates on the “come to be located” language, defining “site” as “area(s) where a hazardous substance has been deposited, stored, disposed, or placed, or has otherwise come to be located. Such areas ma y include multiple sources, and may include the area between the sources.”

On April 9, 2009 (74 FR 16165), EPA stated: The NPL does not describe releases in precise geographical terms; it would be neither feasible nor consistent with the limited purpo se of the NPL (to Identify releases that are priorities for further evaluation), for it to do so. . . . [T]he HRS inquiry focuses on an evaluation of the threat posed and therefor e the boundaries of the release need not be exactly defined. Moreover, it generally is im possible to discover the full extent of where the contamination ‘has come to located’ before all necessary studies and remedial work are completed at a site. . . .During the RI/FS process, the release may be found to be larger or smaller than was originally thought , as more is learned about the source(s) and the migration of the contamination. . . . [T]he known boundaries of the contamination can be expected to change over time.

Until the site investigation process has been complete d and a remedial action (if any) selected, EPA can neither estimate the extent of contamination at the site, nor describe the ultimate dimensions of the NPL site. Even during a remedial action (e.g., the removal of buried waste) EPA may find that the contamination has spread further than previous ly estimated, and the site definition may be correspondingly expanded. In addition, if anothe r, unrelated area of contamination is discovered elsewhere on the property, EPA may decide to evaluate that release for the NPL.

14General Dynamics Longwood NPL Listing Support Document September 2010 

### 3.4 Liability 406

Comment : General Dynamics indicated that it was not res ponsible for the contamination being evaluated as part of the site. General Dynamics asserted that “General Dynamics does not own the Gould [General Dynamics Longwood] site, no evidence has been presente d to show that General Dynamics contaminated the Gould [General Dynamics Longwood] site, and no ev idence has been presented that anyone other than the SEC contaminated the Gould [General Dynamics Longwood] site.” 407 408 409 410 411 412 Response : In as much as this comment concerns liability fo r the contamination at this site, whether any party may be liable for response costs is not consider ed when evaluating a site under the HRS. The NPL serves primarily as an informational and management t ool. The identification of a site for the NPL is intended primarily to guide EPA in determining wh ich sites warrant further investigation to assess the nature and extent of the human health and environmen tal risks associated with the site and to determine what CERCLA-financed remedial action(s), if any, may be appropriate. Identification of a site for the NPL does not reflect a judgment on the activities of th e owner(s) or operator(s) of a site. It does not require those persons to undertake any action, nor does it assign any liab ility 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. This position, stat ed in the legislative history of CERCLA, has been explained in the Federal Register (48 FR 40759, September 8, 1983 and 53 FR 23988, June 24, 1988 ). 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 Implications of this comment on attribution of the release being evaluated at the General Dynamics Longwood site are addressed in secti on 3.12, Origin of Source Contamina tion, of this support document. 

### 3.5 Purpose of NPL

Comment : General Dynamics claimed that “EPA’s efforts to list the Gould [General Dynamics Longwood] site on the NPL are contrary to the inte nt and core purpose of the NPL.” General Dynamics stated that the purpose of the NPL is to: 429 430 431 432 433 434 435 436 437 438 • determine which sites warrant further inves tigation to assess the nature and extent of the human health and environmental risks associated with the site

• identify when CERCLA-financed reme dial actions may be appropriate

• notify the public of sites that U.S. EPA believes warrant further investigation

• provide notice to PRPs that U.S. EPA may initiate CERCLA-financed remedial action.

15General Dynamics Longwood NPL Listing Support Document September 2010

General Dynamics asserted “[l]isting the Gould [G eneral Dynamics Longwood] site on the NPL serves none of these purposes.” 439 440 441 Response : The primary purpose of the NPL is stated in th e legislative history of CERCLA (Report of the Committee on Environment and Public Works, Senate Report No. 96-848, 96th Cong., 2d Sess. 60 [1980]), as follows: 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 The priority list serves primarily informa tional 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 govern ment actions will be necessary in order to do so, and these acti ons will be attended by all appropriate procedural safeguards.

Therefore, 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 that warrant further investigation. Finally, listing a site may, to the exte nt 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.

Specific related comments are addressed in th e following sections of this support document:

• 3.5.1 Further Investigation

• 3.5.2 Remedial Actions

• 3.5.3 Public Notification/Participation

• 3.5.4 Potentially Responsible Party Notification

3.5.1 Further Investigation

Comment : General Dynamics argued that it had already offe red to perform remedial investigation at the site, and therefore, this purpose of the NPL is alr eady served. General Dynamics argued that the first purpose is addressed because GAFRI, legal successor to SEC, is required to investigate and remediate both the SEC and General Dynamics Longwood sites under a 1987 FDEP Consent Decree and a 2004 EPA Order. General Dynamics noted that the SEC site is also addressed by the U.S. EPA Superfund Alternative site program. General Dynamics added th at it “offered (and remains willing) to investigate environmental conditions at the Gould [General Dynamics Longwood] site in an effort to obtain further 468 469 470 471 472 473 474

16General Dynamics Longwood NPL Listing Support Document September 2010

data at those areas of the site that MACTEC identified as potential source areas.” General Dynamics concluded “[a]s such, because investigation of th e Gould [General Dynamics Longwood] site can occur regardless of whether the site is listed on the NPL, listing is not necessary to further the first purpose.” 475 476 477 478 Response : Although the SEC site is addressed by EPA’ s SAA program, the General Dynamics Longwood site and the SEC site are two separate sites (see section 3.3, Extent of the General Dynamics Longwood Site, of this support document). Furthermore, a lthough contamination from the two facilities may have comingled under a portion of the General Dynami cs Longwood site, investigation of the General Dynamics Longwood site (particularly the area around Source No. 2) is not currently complete, and inasmuch as the General Dynamics Longwood site is a separate site from the SEC site, EPA cannot complete its investigation of the General Dynami cs Longwood site under the SEC site SAA; NPL listing of the General Dynamics Longwood site is therefore n ecessary to achieve adequate evaluation of this site. 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 Furthermore, the origin of the 1,1-DCE contamination in Source No. 2 soil and the full extent of associated 1,1-DCE contamination in ground water at the General Dynamics Longwood site are not yet clear. Also, there is some question as to whether TCE was the only chlorinated solvent used at the General Dynamics facility (see section 3.17, Associa ting Substances with Source No. 2, of this support document). Additionally, an investigation carried out by MACTEC in 2007 (Reference 10 of the HRS documentation record at proposal) revealed other pot ential source areas at which various metals were detected in soil samples. Therefore, there is a clear need for NPL listing of the General Dynamics Longwood site in order to realize sufficient fu rther investigation and assessment of the site.

General Dynamics’ comments regarding its willingness to perform a remedial investigation are addressed in section 3.6, Rationale for Listing, of this support document.

3.5.2 Remedial Actions

Comment : General Dynamics stated that because “GAFRI [legal successor to SEC] has already enrolled in the Superfund Alternative Program,” that “GAFRI is obligated to address the contaminants that are present on both the SEC and Gould [General Dynamics Longwood] sites;” therefore, “listing the Gould [General Dynamics Longwood] site separately will no t further the goal of identifying when a CERCLA financed remedial action is appropriate.” 501 502 503 504 505 506 Response : The SEC site and the General Dynamics Longwood site are two separate sites, and at least one of the releases under the General Dynamics Longwood facility does not originate at the SEC site (see 507 508

17General Dynamics Longwood NPL Listing Support Document September 2010

section 3.3, Extent of the General Dynamics Longw ood Site, of this support document). Therefore, GAFRI is not obligated to address releases originatin g solely at the General Dynamics Longwood site. 509 510 511 512 513 514 515 516 517 Furthermore, inasmuch as this comment addresses res ponsibilities for remedial activities, it is not relevant to the listing decision. Listing a site only identifi es that further investigation is warranted, not that remediation is required (see section 3.4, Liability, of this support document). Remediation decisions are made in a stage of the Superfund response process sepa rate from listing, when a record of decision is issued. At that time comments on that decision can be submitted for consideration.

3.5.3 Public Notification/Participation

Comment : General Dynamics asserted that the SEC site Superfund Alternative ac tivities already provide ample opportunity for public participation and invol vement. Thus, General Dynamics asserted “listing the Gould [General Dynamics Longwood] site on the NPL does nothing to advance the purpose of notifying the public of sites that warrant further i nvestigation since that was already accomplished when the SEC Site was enrolled in the Superfund Alternative Program.” 518 519 520 521 522 523 Response : The SEC Superfund Alternative site and the General Dynamics Longwood site are two separate sites (see section 3.3, Extent of General Dynamics Longwood Site, of this support document). Therefore, the public has not been informed that the General Dynamics Longwood site warrants further investigation. 524 525 526 527 528 529 3.5.4 Potentially Responsible Party Notification

Comment : General Dynamics claimed “there is no indication that GAFRI [legal successor to SEC] has refused to comply with its obligations under its FD EP and U.S. EPA orders such that a fund-financed remedial action would be necessary.” General Dynamics asserted that “General Dynamics was and remains willing to undertake a focused investigation in order to determine whether the contamination identified in the MACTEC report is the result of hi storical releases on the Gould [General Dynamics Longwood] site or migration from the SEC Site.” Ge neral Dynamics concluded that “listing the site will not further the goal of notifying potential PRPs that a CERCLA-financed remedial action may be necessary.” 530 531 532 533 534 535 536 537 538 Response : Listing a site serves to inform the general public that the site poses sufficient threat to warrant further investigation. Listing a site does not identify or provide notice to PRPs that they may be liable for releases at a site; listing does not assign liability to an y party (see section 3.4, Liability, of this support 539 540 541

18General Dynamics Longwood NPL Listing Support Document September 2010

document). Notification of PRPs is a separate step of the Superfund program from placement of a site on the NPL and is performed independently from the listing process. 542 543 544 545 

### 3.6 Rationale for Listing

Comment : In several comments General Dynamics implie d that, in decisions leading to the proposed listing of the General Dynamics Longwood site on th e NPL, EPA had been arbitrary and capricious. 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 General Dynamics claimed that EPA “agreed that the contamination on the Gould [General Dynamics Longwood] site was the result of contaminant migra tion from the SEC Site.” General Dynamics asserted that in a 2004 AOC, EPA required GAFRI (legal su ccessor to SEC) to “among other tasks, characterize the nature and extent of contamination at both the SEC and Gould [General Dynamics Longwood] sites. . . . Clearly, U.S. EPA included the Gould [General Dynamics Longwood] site because it recognized that contaminants were migrating from the SEC Site ont o the Gould [General Dynamics Longwood] site.” General Dynamics continued to state “[h]owever, fo r reasons that are not clear, in 2007, U.S. EPA reversed direction and began to focus on trying to pr ove that historical releases of chlorinated solvents had occurred on the Gould [General Dynamics L ongwood] site.” Genera l Dynamics added that: Although U.S. EPA was aware that General Dynamics had conducted operations at the Gould [General Dynamics Longwood] site as a result of General Dynamics’ response to an information request from U.S. EPA in 2003, it was not until August 2008 that U.S. EPA sent General Dynamics a general notice le tter demanding that it perform a Remedial Investigation/Feasibility Study at the site under the Superfund Alternative Program.

General Dynamics stated that during its November 20, 2008, meeting with EPA, General Dynamics disputed the identification of sources on the Gene ral Dynamics Longwood site but offered to further investigate these areas, and EPA concurred with this approach. General Dynamics asserted that EPA “[a]bruptly” shifted course, requiring on January 28, 2 009, signature of an AOC by January 30, 2009, to perform an “unbounded” Remedial Investigation/Feasi bility Study, or EPA would move forward with NPL listing. General Dynamics asserted that: General Dynamics met U.S. EPA’s deadline and submitted a proposed plan to investigate the Gould [General Dynamics Longwood] site per the terms agreed to on November 29, 2008. Rather than accepting General Dynamics’ proposal , U.S. EPA elected to propose the site for listing on the NPL.

Response : EPA has not been arbitrary and capricious or abu sed its discretion in the actions leading to and in the proposal of this site. This site has been placed on the NPL because it has an HRS score greater than 28.50 and meets all CERCLA and NCP listing criteria. As is shown throughout this support document, the comments submitted on the proposed listing of this site have not resulted in a change in the overall 575 576 577 578 19General Dynamics Longwood NPL Listing Support Document September 2010

site score, although some modifications to the evalua tion have been made. No commenter has identified that any of the information used in the HRS evaluation of the site is inadequate for the given purpose or arbitrarily or capriciously select ed for use in the evaluation. 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 Regarding the claim by General Dynamics that EPA has agreed that contamination on the General Dynamics Longwood site originated on the SEC site, EPA explained on page 2 of a letter to General Dynamics on August 27, 2008 (attached to the Genera l Dynamics comment letter as Reference I), that remedial investigations conducted after the 2004 AOC with GAFRI indicated: an additional source or sources of contam ination to the groundwater plume under investigation, as well as another, entirely di stinct groundwater plume. This new source area was located on the property owned by G ould Publications [previously the General Dynamics property] and was contributing a diffe rent contaminant from those found to be emanating from the Sprague Site.

Regarding the offer by General Dynamics to perform a remedial investigation, it was explained to General Dynamics on page 1 of a letter from EPA on February 10, 2009 (attached to this support document as Attachment 1) that:

General Dynamics has indicated they might be willing to consider performing a CERCLA Remedial Investigation (RI), but did no t believe that they were responsible for any contamination at the Site and were therefore unwilling to agree to perform a Feasibility Study (FS) to address any contamination found at the Site.

As contamination remained unremediated at the General Dynamics Longwood site, the decision was made to place this site on the NPL. 

### 3.7 Proper Notice

Comment : General Dynamics asserted that it was not notifie d of the previous investigations of the site, and that: 606 607 608 609 610 611 612 613 614 615 616 617 618 Although U.S. EPA was aware that General Dynamics had conducted operations at the Gould [General Dynamics Longwood] site as a result of General Dynamics’ response to an information request from U.S. EPA in 2003, it was not until August 2008 that U.S. EPA sent General Dynamics a general notice le tter demanding that it perform a Remedial Investigation/Feasibility Study at the site under the Superfund Alternative Program.

Also, General Dynamics stated that: Abruptly, on January 28, 2009, U.S. EPA a dvised General Dynamics that unless it signed by January 30, 2009 an Administrative Order on Consent to perform an unbounded Remedial Investigation/Feasibility Study at the Gould site, U.S. EPA would proceed to list the site on the NPL.

20General Dynamics Longwood NPL Listing Support Document September 2010

619 Response : All required CERCLA and Administrative Procedure Act notice requirements have been met regarding the promulgation of this s ite to the NPL. In developing the NPL regulation the Agency uses a notice and comment process that is consistent with the Administrative Procedures Act (5 USC Section 551 620 621 622 et seq .). According to this procedure, the Agency solicits comments on proposed listings, reviews and considers all comments received, and addresses those comments in the fina l rule. Through this process, commenters can provide any information they believe is relevant to the scoring and listing of proposed sites. This site was proposed for placement on the NPL on April 9, 2009, in the Federal Register (74 FR 16162), and comments were solic ited. All comments received during the comment period specified in that notice are addressed in this support document. Nowhere in these requirements is a requirement that EPA notify the public, including any potentially responsible party, that a site it may be associated with is under investigation prior to proposal of the site listing. 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 In addition, all appropriate access documents were obtained prior to any entry, sampling, or other investigation activities into the former General Dynamics facility property.

This comment has no effect on the HRS site score , or the decision to place the site on the NPL. 

### 3.8 Biased Scoring

Comment : General Dynamics claimed that EPA miscalculated the HRS site score. General Dynamics further asserted that “[t]hese errors were systemically made to exaggerate site risk and force the HRS score over 28.5.” 638 639 640 641 Response : General Dynamics has not demonstrated the in formation used in the HRS evaluation is in error; all the specific issues raised on this subject have been addressed in this support document. In addition, the information used to perform the HR S evaluation of the General Dynamics Longwood site has been reviewed based on the co mments submitted following the proposal of the site to the NPL. After this review, the site score remains unchanged. 642 643 644 645 646 647 

### 3.9 Scoring Other Pathways

Comment : Brown and Caldwell stated that EPA did not sco re the surface water migration pathway, soil exposure pathway, and air migrati on pathway, and stated that “Brown and Caldwell agrees that these pathways do not contribute to the site sco re and therefore need not be evaluated.” 648 649 650 651

21General Dynamics Longwood NPL Listing Support Document September 2010

Response : The HRS does not require scoring all four pathways, if scoring those pathways does not change the listing decision. For some sites, data for scoring a pathway are unavailable, and obtaining these data would be time-consuming or costly. In other cases, data for scoring some pathways are available, but will only have a minimal effect on the site score. In still other cases, data on other pathways could substantially add to a site score, but would not affect the listing decision. The HRS is a screening model that uses limited resources to determ ine whether a site should be placed on the NPL for possible Superfund response. A subsequent stage of the Superfund process, the remedial investigation (RI), characterizes conditions and hazards at the site more comprehensively. 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 To the extent practicable, EPA attempts to score all pathways that pose significant threats. If the contribution of a pathway is minimal to the overall score , in general, that pathway will not be scored. In these cases, the HRS documentation record may incl ude a brief qualitative discussion to present a more complete picture of the conditions and hazards at th e site. As a matter of policy, EPA does not delay listing a site to incorporate new data or score new pathways, if the listing decision is not affected.

EPA must balance the need to fully characterize a site with the limited resources available to collect and analyze site data. For this reason, the EPA gene rally will not score additional pathways upon receiving new data as long as the site still meet s the HRS cutoff score. However, any additional data characterizing site conditions could provide u seful information during the RI.

The HRS is intended to be a “rough list” of prioritized hazardous sites; a “first step in a process--nothing more, nothing less” Eagle Picher Indus. v. EPA, 759 F.2d 922, 932 (D.C. Cir. 1985) (Eagle Picher II). EPA would like to investigate each possible site co mpletely and thoroughly prior to evaluating them for proposal for NPL, but it must reconcile the need for certainty before action with the need for inexpensive, expeditious procedures to identify potentially hazardous sites. The courts have found EPA’s approach to solving this conundrum to be “reasonable and fully in accord with Congressional intent. “Eagle Picher Industries, Inc.” v. EPA, (759 F.2d 905 (D.C. Cir. 1985) Eagle Picher I).



### 3.10 Source No. 1 and Associated Observed Releases

Comment : Brown and Caldwell presented several arguments against the inclusion of Source No. 1 in the HRS evaluation. Specific arguments pr esented by Brown and Caldwell include: 681 682 683 • the origin of contamination within Source No. 1;

22General Dynamics Longwood NPL Listing Support Document September 2010

23 684 685 686 687 688 • the background conditions used to establish S ource No. 1 and observed releases from Source No. 1;

• the use of boundaries delineating Source No. 1;

• the source type of Source No. 1.

Response : Source No. 1, contaminated soil in the west side of the General Dynamics property, and the observed releases to ground water in the vicinity of this source has been dropped from consideration in the HRS evaluation at promulgation. Therefore, the following sections of this support document address technical comments regarding only Source No. 2 and the observed release in the vicinity of that source. 689 690 691 692 693 694 695 Figure 3 details the eastern portion of the General Dyna mics property which contains Source No. 2 and an observed release to ground water.General Dynamics Longwood NPL Listing Support DocumentSeptember 2010696Figure 3: Eastern Portion of the General Dynamics Longwood Site697698Note: Dotted red line presents the SEC SAA site. The general location of the General DynamicsLongwood site shown bounded bydotted blueline.Note that property boundaries are not depicted.24General Dynamics Longwood NPL Listing Support Document September 2010

The removal of Source No. 1 from the evaluation has r esulted in changes to the waste characteristics and target values in the HRS documentation record at promulgation. At proposal, observed releases by chemical analysis of 1,1-DCE, cis-1,2-DCE, trans-1,2-DCE, TCE, and vinyl chloride were identified at the site. Because the only hazardous substance establis hed in the remaining source (Source No. 2) is 1,1- DCE, the HRS documentation record at promulgation has been revised to document only 1,1-DCE as the hazardous substance associated with the observed release at the General Dynamics Longwood site; TCE and cis-1,2-DCE have been removed from consider ation in the HRS evaluation at promulgation. 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714

715 As Source No. 1 was removed from consideration fro m the General Dynamics Longwood site, the 4-mile target distance limit (TDL) was redrawn to show only t hose wells within a 4-mile radius of Source No. 2. (see revised Reference 30 of the HRS documentation reco rd at promulgation). Section 3.21, Targets, of this support document, details the effects of the new TDL.

That the site score remains at 50.00 is detailed in a site re-scoring analysis presented in section 3.22, Revised Site Score, of this support document.



### 3.11 Description of Pathway

Comment : Brown and Caldwell indicated that EPA did not adequately consider subsurface hydrogeologic conditions and the effects of human manipulation of ground water gradients in the HRS evaluation of the site. Brown and Caldwell disagreed with how th e ground water pathway is described in the HRS documentation record at proposal and alleged that a lack of accurate understanding of subsurface conditions, especially regarding flow gradients and the location of a clay layer, has caused EPA’s contractor to have “ grossly oversimplified the regional hy drogeologic conditions and groundwater flow patterns [emphasis in original comment] in the deve lopment of the HRS documentation record at proposal.” 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 Brown and Caldwell asserted that the HRS evaluation did not account for the operation of a ground water remediation pump-and-treat system on the SEC property, and stated that: EPA’s contractor provides absolutely no c onsideration to the temporal impact from operation of the existing groundwater pump-a nd-treat system that was installed by GAFRI along the northern border of the Sprague site. As discussed later in this document, the pump and treat system has signi ficantly altered groundwater flow patterns between the Gould and Sprague properties from those originally depicted in 1992 by

25General Dynamics Longwood NPL Listing Support Document September 2010

Sprague’s consultant. These omissions are a fatal deficiency in the scoring process for the Gould Property [General Dynamics property]. 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 Brown and Caldwell argued that the HRS evaluation di d not accurately determine variations in ground water flow direction over time, and that attributing the increased ground water contamination levels to releases from General Dynamics operations was fl awed. Brown and Caldwell commented that: consultants for the Sprague electric company showed that shallow groundwater flows from the location of Sprague’s release of TCE and 1,1,1-TCA directly onto the Gould Property toward the areas that EPA’s contractor calls . . . ‘Source No. 2’.

Additionally, Brown and Caldwell presented informat ion from an April 2009 subsurface investigation at the General Dynamics Longwood site, and asserted that th e presence and orientation of a clay layer in the surficial aquifer was not considered in developing th e site score. Specifically, Brown and Caldwell state that: The A/B clay unit slopes downward generally northward and, as depicted in Figures 1 and 2, the slope of the A/B clay unit in creases dramatically near Source No. 2 from approximately 0.06 ft/ft in the south to more than 0.5 ft/ft at Source No. 2. A westward deflection of the A/B clay slope was also observed east of Source No. 2. The similar downwarping of the underlying Hawthorn Group suggests that this observed deformation is the result of subsidence due to Karst activity north of Source No. 2. The geometry of this impermeable layer represents a transport mechanism for the northward migration of VOC-contaminat ed groundwater from the upslope Sprague Electric site to the downslope Gould Property [General Dynamics property] that was not considered by EPA’s contractor when scoring the Gould Property [General Dynamics property] [emphasis in original comme nt]. Upgradient releases of TCE, 1,1,1- TCA, and their breakdown products likely migrated down the slope of the A/B clay layer. This northward migration of contaminants from Sprague to Gould [General Dynamics] was driven by groundwater recharge that tran sported contaminants to the base of the A Zone where they were funneled by the cl ay topography northward to Source No. 2.

Response : Subsurface geological and hydrogeological cond itions at the General Dynamics Longwood site were sufficiently evaluated and understood to support the HRS score for the site, and the additional information provided by Brown and Caldwell does not alter the evaluation. The subsurface conditions were properly understood for the evaluation of the ground water pathway in general and specifically regarding the likelihood of release to ground water. The HRS documentation record at proposal establishes the subsurface geological characteristics, in cluding the existence of subsurface clay layers. Also, ground water aquifers, flow gradients associated with them, and the confining layers within and between aquifers are established in th e HRS documentation record at proposal. 763 764 765 766 767 768 769 770 771

26General Dynamics Longwood NPL Listing Support Document September 2010

To evaluate the HRS ground water pathway of a s ite, the scorer needs to delineate the aquifer being evaluated, including the existence of any interconnec tions with other water-bearing strata within 2 miles of the site source(s) and any discontinuities within th e 4-mile target distance limit. Brown and Caldwell did not provide any specific comments on this delineation. No ground water flow direction information is specifically required in the HRS; however, in evalua tion of Likelihood of Release to ground water, it is necessary to establish a background contaminant level for purposes of showing a significant increase and attributing a release to the site (see section 3.18 , Likelihood of Release – B ackground, of this support document). This background contamination level is usually established by analyzing samples from upgradient of the site sources 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 Page 30 of the HRS documentation reco rd at proposal describes the genera l regional geological strata and depositional formations in the subsurf ace underlying the site. It states: The General Dynamics property is located in the western section of Seminole County on the Florida Platform section of the Atlantic Co astal Plain province (Refs. 4, p. 3; 10, p. 48; 67, pp. 2, 3; 69, p. 4). The topography in Seminole County is divided into two types: a flat lowland and hilly uplands (Refs. 68, p. 6; 70, pp. 6, 7). Elevation at the General Dynamics property is about 35 feet above sea level (asl) (see Figure 1 of this HRS documentation record) (Ref. 30). The General Dynamics property is underlain in descending stratigraphic order by undifferentiate d deposits of the Holocene, Pleistocene, and Pliocene age; the Hawthorn Group of th e Miocene age; the Ocala Limestone, Avon Park Formation, and Oldsmar Formation of the Eocene age; and the Cedar Keys Formation of the Paleocene age (Ref. 68, pp. 10, 13).

The aquifers underlying the site were described on pages 30-31 of the HRS documentation record at proposal, as follows: Ground water in the Seminole County, Florid a area exists in two distinct units: the surficial aquifer and the Floridan aquife r. These aquifers are separated by a discontinuous intermediate confining unit (H awthorn Group). The surficial aquifer has limited use due to low yields to wells and the potential for contamination. Water withdrawn from the surficial aquifer is used mainly for lawn irrigation (Refs. 8, Figure 4- 40; 29; 68, pp. 2, 13; 71, p. 32). The Floridan aquifer system is the principal source of ground water in east-central Florida and is di vided into two aquifers of relatively high permeability, the Upper Floridan and the Lowe r Floridan aquifers. These aquifers are separated by a less permeable unit that restricts the downward movement of water (Ref. 68, p. 19). The surficial aquifer consists of undifferentia ted sediments of the Holocene, Pleistocene, and Pliocene ages; the intermediate confini ng unit consists of part of the Hawthorn Group; and the Floridan aquifer consists of portions of the Hawthorn Group, Ocala Limestone, the Avon Park Formation, the Olds mar Formation, and the upper part of the Cedar Keys Formation (Ref. 68, pp. 13, 19). In Seminole County, the surficial aquifer is separated from the Floridan aquifer by the confining bed of the Hawthorn Group;

27General Dynamics Longwood NPL Listing Support Document September 2010

however, the Hawthorn Group is not continuous ; and is not present directly north (about 240 feet) of the General Dynamics property (Refs. 8, Figure 4-40; 29; 71, p. 32). 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 The surficial aquifer is the upper most water bearing unit in Seminole County. The system is unconfined and consists mainly of lenses of fine to medium quartz sand with varying amounts of shell and clay. The deposits are discontinuous and their lithology and texture can vary over short distances. The t op of the surficial aquifer is defined by the water table (Ref. 68, p. 14). The base of the surficial aquifer system is characterized by the first persistent beds of Miocene or P liocene age containing a significant increase in clay or silt. The altitude at the base of the surficial aquifer system ranges from about 75 feet asl to more than 75 feet below sea level in Seminole County (Ref. 68, p. 16).

Page 32 of the HRS documentation reco rd at proposal described the surficial aquifer, the clay layer associated with it, and the general ground water flow gradient in the aquifer directly under the site, as follows: Previous investigations at the General Dyna mics and SEC properties divide the surficial aquifer into two water bearing zones, A-zone and B-zone, and refer to the Upper Floridan aquifer as the C-zone. The A-zone (upper su rficial aquifer) and B-zone (lower surficial aquifer), are separated by a discontinuous clay layer (A/B clay) (Ref. 8, pp. 3-3, 3-4, Figure 2-3). The A/B clay layer ranges in de pth from 13.5 [feet] bls to 32 feet bls across the General Dynamics property and is absent in the northwestern portion of the property (Ref. 8, p. 2-4, Figure 2-3, Appendix C, pp. 27 through 49). The ground water flow direction in the A and B zones is north to northeast across the General Dynamics property (Refs. 8, Figures 3-6 and 3-7; 10, p. 57).

That the geologic and hydrogeologic conditions underlying the site were adequately identified in the evaluation of the site is discussed in the following s ubsections of this support document. The aquifers being evaluated were properly delineated in the HR S documentation record at proposal according to HRS criteria. Specifically, the interconnection between the surficial aquifer and Floridan aquifer was established within 2 miles of Source No. 2, and aq uifer discontinuities within the 4-mile TDL were evaluated.

Brown and Caldwell’s specific arguments regarding subsurface conditions are addressed in the following subsections of this support document:

• 3.11.1 Consideration of Pump-and-Treat System

• 3.11.2 Surficial Aquifer Clay Layer.

28General Dynamics Longwood NPL Listing Support Document September 2010

3.11.1 Consideration of Pump-and-Treat System 851 Comment : Brown and Caldwell asserted that the HRS evaluation of the General Dynamics Longwood site did not take into account the operation of the pump-and-treat remediation system on the SEC property. 852 853 854 855 Response : The pump and treat activities between the SEC site and General Dynamics Longwood site have certainly some local effect on the flow gradient in the area, based on monitoring of flow gradient during the pump-and-treat operations; however, this impact did not alter the overall ground water flow direction from south to north while the activities were in operation. Multiple years of environmental investigations and monitoring have produced ground water potentiometric data (i.e., ground water level data) from various periods of time, as presented in the references to the HRS documentation record at proposal. 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 Also, that the pump-and-treat system has not had a significant effect on the northerly flow direction can be seen in Exhibit J of Brown and Caldwell’s comments (docket ID EPA-HQ-SFUND-2009-0067- 0006.1), which present flow direction during different times of the operation of the remediation system. These figures show that both the A and B zones of the surficial aquifer have maintained a generally northerly flow direction both during static conditions and during pumping conditions.

Thus, analysis of the data indicates that, even during years when the remediation system was operational, there has been a generally northward movement of ground water in the vicinity of Source No. 2. The operation of the remediation system at the SEC property has not had any significant observable impact on the ground water flow gradients in the surficial aquifer in the vicinity of Source No. 2, and has not impacted the establishment of Sour ce No. 2 or associated releases.

Section 3.18.3, Effects of Pump and Treat, of th is support document addresses the commenter’s assertions regarding ground water flow rates and the effects of the pump-and-treat system on the validity of background sample locations for the east ern (Source No. 2) part of the site.

This comment has no effect on the HRS site score or the decision to place this site on the NPL.

29General Dynamics Longwood NPL Listing Support Document September 2010

3.11.2 Surficial Aquifer Clay Layer 882 Comment : Brown and Caldwell presented information from an April 2009 subsurface investigation at the General Dynamics Longwood site, and asserted that the ge ometry of the surficial aquifer clay layer (A/B clay layer) between the upper and lower surficial a quifer acts as a mechanism for the transport of VOC (volatile organic compound)-contaminated ground wa ter from the SEC site to the General Dynamics Longwood site. Brown and Caldwell stated that: 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 Lithologic profiling by Brown and Caldwe ll provides a much better understanding of hydrostratigraphy in the region of the si tes lying between the Sprague and Gould [General Dynamics] properties. Figure 1 (Exhibit G) depicts the topographic surface of the top of the A/B clay unit based on data from Brown and Caldwell’s borings in April 2009 coupled with data taken from historic so il borings by other consultants. Figure 2 (Exhibit H) is a cross section running through AOC [area of concern]-A (Source No. 2) and the area to the south.

Additionally, Brown and Caldwell asserted that 1, 1-DCE concentrations in ground water samples collected directly above the A/B clay unit and unde rlying Source No. 2 indicate that solvents released from the SEC site are migrating along the clay layer. Brown and Caldwell stated that: Analytical results for groundwater samples collected directly above the A/B clay unit in 2005 and 2007 indicate that the relatively high concentrations of 1,1-DCE in groundwater at Source No. 2 are coincident with a scenario in which they were originally released at the Sprague site and traveled to the Gould Property [General Dynamics property] along the steep slope of the A/B clay unit [emphasis in original comment]. These VOCs (TCE and 1,1,1-TCA and their breakdown pr oducts) appear to have been confined by the topography of the unit. This configuration suggests that northward-migrating contaminants in groundwater encountered a zone of decreased groundwater flow at the break in slope where the A Zone abruptly increased in thickness from approximately 6 feet of saturated thickness to 22 feet.

Figures summarizing the results of subsurface borings advanced by Brown and Caldwell at or near Source No. 2 were included as Exhibit G and H of Br own and Caldwell’s comments (docket ID EPA-HQSFUND-2009-0067-0006.1). These figures document that the surficial aquifer clay layer decreases in elevation underlying Source No. 2, and that ground wa ter samples collected from directly above the A/B clay layer document high levels of 1,1-DCE.

Response : The A/B clay layer as defined in the HRS doc umentation record at proposal and associated references was adequately delineated in the HRS evaluation. The clay layer was used to segment the surficial aquifer into the “A” zone and the “B” zone and to guide the selection of background and releases samples in the two zones. The information regardin g the location of the clay layer provided by Brown and Caldwell, while potentially increasing the delineation of the clay layer, does not change the 916 917 918 919 920

30General Dynamics Longwood NPL Listing Support Document September 2010

delineation of the surficial aquifer or the identifi cation of the wells used in establishing an observed release, as it is screened above the clay layer. In fact, the subsurface investigation information discussed by Brown and Caldwell was not provided with informa tion outlining the full scope of its investigation, sampling plan, or complete analytical results, nor performed under the direction of a state or federal agency. Thus, its claims regarding the informati on obtained from this subsurface investigation at the General Dynamics Longwood site ar e not adequately documented. 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 The HRS does not contain specific instruction on ho w to delineate subsurface clay layers, except in establishing interconnection, where confining units ar e to be characterized as they correspond to ground water aquifers. HRS Section 3.0.1.2.1, Aquifer Interconnections , instructs the evaluator to: Evaluate whether aquifer interconnections occur within 2 miles of the sources at the site. If they occur within this 2-mile distance, co mbine the aquifers having interconnections in scoring the site. In addition, if observed gr ound water contamination attributable to the sources at the site extends beyond 2 miles from the sources, use any locations within the limits of this observed ground water contamination in evaluating aquifer interconnections. If data are not adequate to establish aquifer interconnections, evaluate the aquifers as separate aquifers.

The aquifers being evaluated were properly delineat ed in the HRS documentation record at proposal in accordance with the HRS. Aquifer interconnection between the surficial (both A and B zones) and Floridan aquifers was established within 2 miles of Source No. 2, and aquifer discontinuities within the 4- mile target distance limit were evaluated. (See sec tion 3.11, Description of Pathway, of this support document.)

The HRS documentation record at proposal documents th e existence of the A/B clay layer and that it was discontinuous in the vicinity of the site. Speci fically, page 16 of the HRS documentation record at proposal states regarding the surficial aquifer that: [t]he “A” zone and “B” zone are separated by a clay layer (A/B) that exists at depths ranging from 11 feet to 32 feet bls across the SEC and General Dynamics properties; however, the A/B clay layer is absent in certain areas of both properties.

The analysis of the A/B clay layer was supported by Reference 8, Figure 2-3 of the HRS documentation record at proposal. This figure displays the da ta gathered during the 2005 Remedial Investigation conducted by URS, and was used in the characterization of the surficial aquifer clay layer.

The new information provided by Brown and Caldwell supplements and further refines the existing data used in the HRS evaluation. However, this new information does not disprove that aquifer

31General Dynamics Longwood NPL Listing Support Document September 2010

interconnection was correctly established, or that ground water samples used in the establishment of the observed release were correctly identified as located in the upper surficial zone of the surficial aquifer. 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 Regarding Brown and Caldwell’s assertion that high VOC concentrations detected above the clay layer are indicative of contaminant migration along the clay layer from the SEC site to the General Dynamics Longwood site, EPA does not disagree that contaminated ground water could be following the A/B clay layer from the SEC site to under the General Dynamics Longwood site. However, there is not sufficient evidence to prove this has occurred; on the contrary , as discussed in section 3.19, Likelihood of Release – Attribution, of this support document, the review of historical upgradient sampling data indicates that 1,1- DCE was detected in ground water at the release sample location underlying the General Dynamics property at a significantly higher level than the levels of 1,1-DCE documented at any other location on the General Dynamics property or the hydraulically upgrad ient SEC property, and is therefore not the result of contaminated ground water migration along the clay layer.

Section 3.19.3, Contaminant Migration Direction, of this support document further addresses the commenter’s arguments regarding the surficial aquifer clay layer and its impact on the selection of background samples for and the attribution of the rel ease in the area of Source 2 to the General Dynamics Longwood site.

This comment has no effect on the HRS site score or the decision to place this site on the NPL.



### 3.12 Identification of a Source an d Origin of Source Contamination

Comment : General Dynamics and Brown and Caldwell as serted that contamination associated with Source No. 2 was improperly linked to General Dynami cs’ operations; they argued that Source No. 2 in the HRS documentation record was the result of opera tions at the Sprague facility. General Dynamics asserted that EPA’s contractor incorrectly concluded that contaminants identified in Source No. 2 were the result of releases from the General Dynamics Longw ood site. Brown and Caldwell also asserted that there is no evidence of a release to soil which could potentially be released to ground water. Brown and Caldwell added that: 980 981 982 983 984 985 986 987 988 989 990 991 992 EPA’s contractor incorrectly interpreted sa mple results discussed on pp. 18-28 of the Record [referring to the Source Characterization section of the HRS documentation record at proposal]. These samples were collected from saturated aquifer materials, or at the very worst in one instance, within th e capillary fringe of the upper water bearing zone.

32General Dynamics Longwood NPL Listing Support Document September 2010

Brown and Caldwell continued that “ [t]his is a fatal flaw in the HRS scoring process and because of it, EPA’s contractor has incorrectly concluded that th ere is evidence of a release in the soil at the Gould Property [General Dynamics property] [emphasis in original comment].” 993 994 995 996 Response : Source No. 2, contaminated soil, was established and evaluated in the HRS score for the site consistent with the HRS definition of source , and other HRS requirements. A source need not be linked to a specific operation to meet the HRS definition of a source, nor must the original cause of the contamination be known. (EPA notes, however, as discussed in section 3.19, Likelihood of Release – Attribution, of this support document, EPA attributes a release of the substance in the soil to operations on the General Dynamics property.) 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 In HRS Section 1.1, Definitions , the HRS defines source as Any area where a hazardous substance has been deposited, stored, disposed, or placed, plus those soils that have become contamin ated from migration of a hazardous substance.

HRS Section 2.2.1, Identify sources , outlines the requirements to be fo llowed when identifying sources at a site. It states: For the three migration pathways, identify th e sources at the site that contain hazardous substances. Identify the migration pathway(s) to which each source applies.

HRS Section 2.2.2, Identify hazardous substances associated with a source , discusses the HRS requirement used to identify the hazardous subs tances associated with a source. It states: For each of the three migration pathways, consider those hazardous substances documented in a source (for example, by sampling, labels, manifests, oral or written statements) to be associated with that source when evaluating each pathway.

Also, HRS Section 2.2.3, Identify hazardous substances available to a pathway , states: In evaluating each migration pathway, co nsider the following hazardous substances available to migrate from the sources at the site to the pathway: Ground water migration.

-Hazardous substances that meet the criteria for an observed release (see section 2.3) to ground water -All hazardous substances associated with a source with a ground water containment factor value greater than 0 (see section 3.1.2.1).

HRS Section 3.1.2.1, Containment , directs the scorer to:

33General Dynamics Longwood NPL Listing Support Document September 2010

Assign a containment factor value from Table 3-2 to each source at the site. Select the highest containment factor value assigned to those sources with a source hazardous waste quantity value of 0.5 or more (see section 2. 4.2.1.5). (Do not include this minimum size requirement in evaluating any other factor of this pathway.) Assign this highest value as the containment factor value for the aquifer be ing evaluated. Enter this value in Table 3-1. 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 The HRS documentation record at proposal containe d the information necessary to establish Source 2 to be a contaminated soil source with a ground water contai nment value greater than 0. Page 23 of the HRS documentation record at proposal stated that “Sour ce No. 2 is contaminated soil located beneath the southeastern corner of Building 3 in the vicinity of the former vapor degreaser.” Page 24 of the HRS documentation record at proposal discussed the met hod by which hazardous substances were documented to be associated with Source No. 2 by showing that: Subsurface soil samples, SB-006-3, SB-017-3, and SB-037-3, were collected from the General Dynamics and SEC properties at the same depth (3 feet bls) and were used to establish background concentrations (Refs. 49, Figure 3; 75, pp. 13, 20; 80, pp. 27, 29). The contaminated subsurface soil sample, SB -038-03, was collected in the area of the former vapor degreaser located in the southeast ern corner of Building 3 at a depth of 3 feet below the building floor. The sample was collected inside the building by coring through the concrete using a direct push rig. (R efs. 16, pp. 14, 15, Exhibit 1; 49, Figure 3; 80, pp. 29, 30). The background subsurface soil samples and contaminated subsurface soil samples were collected from the same soil type (urban land, 0 to 12 percent slopes), at the same depth, during the same sampli ng event, and in accordance with the same sampling procedures.

As cited above, three subsurface soil samples we re collected from the General Dynamics and SEC properties to establish background concentrations, while a contaminated soil sample (SB-038-3) was collected from the General Dynamics Longwood site. These samples indicate that a significant increase of the CERCLA hazardous substance, 1,1-DCE, w as documented within soil sample SB-038-3 that exceeded the background contamination levels from the SEC site and the General Dynamics Longwood site. Table 1 below presents the hazardous substance documented within Source No. 2 soils, as presented on page 24 of the HRS documentation record at pro posal, and Figure 4 presents the soil sample locations used to document the contaminated soil source.

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35 1072 1073 Table 1: Soil Analytical Data from Source No. 2 Sample ID / Station ID Facility Location Hazardous Substance Hazardous Substance Concentration MDL Documentation Record References Background Subsurface Soil Sample SB-006-3 SEC 1,1-DCE 4.5U μg/kg 4.5 μg/kg 28, pp. 1-3; 50, pp. 7, 44; 51, pp. 57 through 61; 75, p. 13 SB-017-3 General Dynamics 1,1-DCE 4.7U μg/kg 4.7 μg/kg 28, pp. 1-3; 51, pp. 62 through 66; 75, p. 20; 76, pp. 13, 46 SB-037-3 General Dynamics 1,1-DCE 3.2U μg/kg 3.2 μg/kg 28, pp. 1-3; 51, pp. 47 through 51; 80, p. 27; 92, pp. 18, 43 Contaminated Subsurface Soil Sample SB-038-3 General Dynamics 1,1-DCE 19.2 μg/kg 2.5 μg/kg 28, pp. 1-3; 77, pp. 15, 34; 51, pp. 2 through 6; 80, p. 29 1074 Notes : 1075 1076 1077 1078 1079 1080 1081 1082 1083 1,1-DCE 1,1-Dichloroethlyene ID Identification number μg/kg Microgram per kilogram MDL Method detection limit MW Monitoring well SB Subsurface soil sample U Material not detected at or above reporting limitGeneral Dynamics Longwood NPL Listing Support DocumentSeptember 20101084Figure 4: Source Soil Sample Locations36General Dynamics Longwood NPL Listing Support Document September 2010

Regarding the ground water migrati on containment factor, section 2.2.3 of the HRS documentation record at proposal states that: 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 The subsurface soil sample collected from Source No. 2 contained an elevated concentration of 1,1-DCE (Refs. 49, Figure 3; 77, pp. 15, 34) (also see Table 5 of this HRS documentation record). Source No. 2 c onsists of an area of contaminated soil located in the southeastern portion of Buildi ng 3 on the General Dynamics property (Ref. 16, pp. 14, 15, Exhibit 1). Analytical results for ground water collected in the vicinity of Source No. 2 indicate that a release of h azardous substances has occurred to the ground water migration pathway as documented in Section 3.0 of this HRS documentation record. During the 2005 RI, a liner was not observed during sampling activities (Ref. 56). Therefore, a containment factor value of 10 was assigned for the ground water migration pathway (Ref. 1, Section 3.1.2.1, Table 3-2).

The HRS documentation record at proposal appropr iately associated a hazardous substance (1,1-DCE) with Source No. 2 through sampling, and by compari ng the contaminant levels to background levels demonstrated that the soil came to be contaminated due to migration. Additionally, a ground water containment factor value of 10 was documented as asso ciated with the source. Thus, Source No. 2 was established as a contaminated soil source according to HRS criteria.

As the identification of the cause for the hazardous s ubstances to be found within Source No. 2 is not an HRS requirement to identify a source, the HRS documentation record at proposal need not and did not identify the origin of the contamination documen ted within Source No. 2. However, the HRS documentation record at proposal did identify possible origins of the 1,1- DCE.

Furthermore, the identification of the origin of the contaminants within a source is a liability issue (see section 3.4, Liability, of this support document for di scussion of why liability is not relevant to the listing process.)

Brown and Caldwell’s specific arguments regarding the origin of contamination at Source No. 2 as being from General Dynamics operations are addressed in th e following subsections of this support document:

• 3.12.1 Evidence of Contamination

• 3.12.2 Evidence of Migration from Former Vapor Degreaser

• 3.12.3 Contamination from Upgradient Ground Water Releases.

37General Dynamics Longwood NPL Listing Support Document September 2010

3.12.1 Evidence of Contamination 1119 Comment : Brown and Caldwell stated that “VOC concen trations in shallow soil beneath Source No. 2 showed only minute concentrations of 1,1-dichloroethy lene (1,1-DCE) and tetrachloroethylene (PCE), but no detections of TCE.” 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 Referring to the soil samples collected near Source No. 2 within the 2008 Site Inspection Report completed by MACTEC, Brown and Caldwell also co mmented that “[t]he only detection above the method reporting limit was in the duplicate sample for SB-6,” which Brown and Caldwell noted contained carbon disulfide. Brown and Caldwell con tinued to state that “[c]arbon disulfide is not a breakdown product of TCE,” a nd “[t]hus, here [sic] are no soil sample results that provide any evidence of a release of the TCE in the vicinity of the vapor degreaser that was allegedly present in Building 3 [emphasis in original comment].”

Response : Regarding the comment that only “minute” concentr ations of 1,1-DCE were detected in Source No. 2 soil, the concentration found in sample SB-038-03 from the 2005 investigation (as presented in Table 1 of this support document) satisfies the HRS requirement to identify hazardous substances in a source. The HRS definition of a source does not speci fy a minimum concentration of contaminants in a soil source, only that the soils came to be contaminat ed due to migration. The concentration of 1,1-DCE detected within Source No. 2 soils exceeds the concentration of 1,1-DCE in related background samples, therefore the contaminants were not naturally presen t and came there due to migration. The other compounds mentioned by the commenter (PCE, TCE, a nd carbon disulfide) are not identified specifically as associated with the source and were not used in establishing Source No. 2 or scoring the site. 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 This comment has no effect on the HRS site score or the decision to place the site on the NPL.

3.12.2 Evidence of Migration from Former Vapor Degreaser

Comment : Regarding the former vapor degreaser discussed in the HRS documentation record, Brown and Caldwell commented that “[t]he Record places great weight on the existence of a vapor degreaser as a source of contamination to groundwater, but there is no evidence of any release to soil or groundwater at this location.” Brown and Caldwell argued that: 1145 1146 1147 1148 1149 1150 1151 1152 1153 In fact, inspection of the area provides evid ence that there was not a release at this location. Brown and Caldwell’s April 2009 subsurface investigation evaluated environmental conditions at the Gould Prope rty [General Dynamics property]. The investigation included advancing ten bori ngs inside Building 3 (at AOC [area of concern]-A) to evaluate VOC concentr ations in groundwater in the SAS.

38General Dynamics Longwood NPL Listing Support Document September 2010

1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 Brown and Caldwell continued that: Observations of the concrete slab beneat h the removed flooring at AOC [area of concern]-A revealed no evidence for a sump or floor drain associated with the former Source No. 2 vapor degreaser. This indicates that the Source No. 2 degreaser was a small, floor-mounted unit – a description that is consistent with descriptions provided by former General Dynamics employees (Reference 88). Further, as s hown by photographs taken during Brown and Caldwell’s direct ob servations in April 2009 . . . the sub-tile concrete slab was observed to be free of penetrations, large cracks, or patches other than for previous environmental investigation bor ings advanced by others. The absence of penetrations or cracks means that any degreasing solvents that might have been spilled would have had limited opportunity to penetrate into subsurface soils beneath Building 3 [emphasis in original comment].

In support of its assessment of the floor within Bu ilding 3, Brown and Caldwell asserted that previous inspections at the General Dynamics property have s hown no trenches, floor drains, sumps, pits, or sewers in the vicinity that could have functioned as a preferential pathway for solvent to have reached the subsurface. Additionally, Brown and Caldwell comme nted that “[t]he April 2009 inspection by Brown and Caldwell confirmed the absence of floor drains other than those identified in the 2004 report.”

Brown and Caldwell stated that the condition of th e floor in Building 3 “[i]s further evidence that no significant amount of solvent was released to the floor at Source No. 2 [emphasis in original comment],” and that because of a lack of elevated VO C concentrations measured in the soils beneath the concrete slab during Brown and Caldwell’ s April 2009 investigations, it is “ consistent with the explanation that these VOCs originated away from the Gould Property [General Dynamics property] [emphasis in original comment].”

Response : The HRS documentation record at proposal does not state specifically that the former vapor degreaser is the origin of the contamination with in Source No. 2. However, the HRS documentation record at proposal discusses the former vapor degreaser , as well as storage tanks and drums to illustrate the usage of solvents in the vicinity of the contamin ated soil. Furthermore, the HRS definition of source does not require identification of the origin of the contamination (see section 3.12, Identification of a Source and Origin of Source Contamination, of this support document). 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 In addition, although the HRS documentation record discusses the use of TCE in the cleaning processes of printed circuit board manufacturing, and that TC E use in a former vapor degreaser at the General Dynamics facility was described in deposition testimonies by former General Dynamics employees, the HRS documentation record at proposal does not establish that TCE was the exclusive solvent used at the

39General Dynamics Longwood NPL Listing Support Document September 2010

facility. Deposition testimony by Quentin Glynn (Reference 88 of the HRS documentation record at proposal) indicates the usage of 1,1,1-TCA at the site , as the former General Dynamics employee testified using a product called “1,1,1-Tric,” in the cleaning of printed circuit boards. Trichloroethylene and PCE would not have correctly been identified with “1,1 ,1-” preceding their names, according to chemical nomenclature, while 1,1,1-TCA could have been. Th is suggests the possible use of 1,1,1-TCA at the General Dynamics Longwood site. As noted by th e commenter, 1,1,1-TCA is known to degrade 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 3 to 1,1- DCE, the hazardous substa nce documented in the source and observed release.

This comment has no effect on the HRS site score or the decision to place the site on the NPL.

3.12.3 Contamination from Upgradient Ground Water Releases

Comment : Brown and Caldwell asserted that the basis provided in the HRS documentation record to “identify Source No. 2 as a release location is technica lly flawed,” and alleged that the sample used to establish Source No. 2 (SB-038-038) was: 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 collected from an elevation that is in the satur ated zone or, at worst, in the capillary fringe atop the aquifer. Detection of 1,1-DCE refl ects soil pore water that has migrated from the upgradient Sprague property. The capilla ry rise is estimated at a minimum of 23 inches from the top of the water table, which ranges from 2.7 to 4.2 feet (32 to 50 inches) below ground surface based upon URS measurements in 2005 and 2006.

Additionally, Brown and Caldwell commented that th e “[r]elatively high concentrations of VOCs” detected in ground water between 20 to 24 feet belo w ground surface at Source No. 2, compared to the shallow soil and ground water concentrations of 1,1- DCE “that are three orders of magnitude lower,” is

“ inconsistent with a surface release of solvents at Source No. 2 and means that the likely source of the 1,1-DCE is not from a hypothetical release at the Gould Property [General Dynamics property] , but from the documented 1,1,1-TCA release at the SEC site [emphasis in original comment].” 1215 1216 1217 1218 1219 1220 1221 Brown and Caldwell alleged that plum e(s) originating at the Sprague s ite have affected the ground water sample results which the HRS documentation record presents, and that the HRS documentation record relies upon “one saturated or capillary fringe soil sampl e6 [sic] that reflects 19.2 μg/kg of 1,1-DCE that

3 Parent chlorinated solvent compounds, such as TCE and 1,1,1-TCA, degrade preferentially to specific daughter products. 1,1,1-TCA, is known to preferentially degrade to 1,1-DCE, and TCE is known to preferentially degrade to cis-1,2-DCE, depending on th e subsurface conditions as pointed out by Brown and Caldwell in its comments and in Exhibit D of its comments. 40General Dynamics Longwood NPL Listing Support Document September 2010

has migrated from the upgradient Sprague site while undergoing abiotic degradation of the 1,1,1-TCA release that originated there.” 1222 1223 1224 Response : The HRS does not require the original cause of the contamination to be known to identify the contaminated soil as a source, as explained in sections 3.12, Identification of a Source and Origin of Source Contamination, and 3.12.2, Evidence of Migration from Former Vapor Degreaser, of this support document. Regarding the commenter’s assertion that hazardous substances released from the SEC property have migrated through the ground water from releases on the SEC property and have contaminated soils at Source No. 2, it is not likely that the contaminated soil at Source No. 2 was impacted in this manner. Due to the nature of ch lorinated solvents which are denser than water and preferentially dissolve or move as free product into the ground water and sink to lower levels of the subsurface, it is more likely that solvents originated from an original release near Source No. 2, possibly from the nearby handling of solvents in drums, above or underground storage tanks, or the vapor degreaser. Further, ground water contamination associated with the hydraulically upgradient SEC property also would be expected to act in a similar fa shion in the subsurface. A migration of solvents in the ground water toward the General Dynamics property from the SEC site would be expected to have a downward component, not upward from the ground wate r into soil in the unsaturated zone. Thus, solvents detected at the General Dynamics propert y in the vicinity of Source 2 and the associated observed release are the result of a release at that pr operty, and are not considered a migrated solvent from the SEC site. Refer to section 3.15, Source Type , of this support document for a discussion on the consideration of soil within the “capillary fringe.” 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 The commenter’s argument regarding the attribution of the observed release from Source No. 2 to ground water is addressed in section 3.19, Likelihood of Release - Attribution, of this support document.

This comment has no effect on the HRS site score or the decision to place the site on the NPL.



### 3.13 Likelihood of Releases – Sources

Comment : Brown and Caldwell questioned the inclusion of Source No. 2 in the HRS evaluation because EPA did not score the likelihood of release for this source. Brown and Caldwell asserted that Source No. 2 is not “an ‘[o]bserved’ nor a ‘[p] otential’ [r]elease to [g]roundwater.” Brown and Caldwell stated that: 1250 1251 1252 1253 1254 1255 1256 As noted on p. 56 of the Record, EPA’s cont ractor did not score alleged Source No. 2 for the HRS’s ‘potential to release’ factors. Brown and Caldwell agrees that there is no credible evidence to suggest that Source No. 2 should be scored at this time.

41General Dynamics Longwood NPL Listing Support Document September 2010

Response : Source No. 2 was established and included in th e Ground Water migration pathway evaluation consistent with the HRS definition of source and the applicable HRS directions (see section 3.12, Identification of a Source and Origin of Source C ontamination, of this support document). The commenter appears to have confused the identifica tion of sources and the evaluation of the likelihood of release in an HRS evaluation. There is no requirement in the HRS that a source be evaluated for its likelihood of release for the source to be eligible for evaluation—only that source containment for the pathway being evaluated be greater than zero. 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 HRS Section 2.2.3, Identify hazardous substan ces available to a pathway , states: In evaluating each migration pathway, co nsider the following hazardous substances available to migrate from the sources at the site to the pathway:

• Ground water migration. o Hazardous substances that meet the criteria for an observed release (see section 2.3) to ground water o All hazardous substances associated with a source with a ground water containment factor value greater than 0 (see section 3.1.2.1).

HRS Section 3.1.2.1, Containment , directs assignment of a containment factor value to each source at a site, stating: Assign a containment factor value from Table 3-2 to each source at the site. Select the highest containment factor value assigned to those sources with a source hazardous waste quantity value of 0.5 or more (see section 2.4. 2.1.5). . . . Assign this highest value as the containment factor value for the aquifer being evaluated. . . . If no source at the site meets the minimum size requirement, then select the highest value assigned to the sources at the site and assign it as the containment factor value for the aquifer being evaluated.

Page 26 of the HRS documentation reco rd at proposal documents the assignment of a factor value of a 10 for containment of this source for the ground water pathway. It states that: The subsurface soil sample collected from Source No. 2 contained an elevated concentration of 1,1-DCE (Refs. 49, Figure 3; 77, pp. 15, 34) (also see Table 5 of this HRS documentation record). Source No. 2 c onsists of an area of contaminated soil located in the southeastern portion of Buildi ng 3 on the General Dynamics property (Ref. 16, pp. 14, 15, Exhibit 1). Analytical results for ground water collected in the vicinity of Source No. 2 indicate that a release of h azardous substances has occurred to the ground water migration pathway as documented in Section 3.0 of this HRS documentation record. During the 2005 RI, a liner was not observed during sampling activities (Ref. 56). Therefore, a containment factor value of 10 was assigned for the ground water migration pathway (Ref. 1, Section 3.1.2.1, Table 3-2).

The HRS documentation record at proposal appr opriately assigns to Source No. 2 a ground water containment factor value of 10, which is greater th an 0; thus, Source No. 2 is properly included in the

42General Dynamics Longwood NPL Listing Support Document September 2010

HRS evaluation. Furthermore, an observed release to ground water attributable to the site is correctly established for this site and this release is attributable at least in part to this source (see section 3.18.1, Selection of Background Samples, of this support document). 1299 1300 1301 1302 1303 1304 1305 This comment has no effect on the site score or the decision to place this site on the NPL. 

### 3.14 Source Description

Comment : General Dynamics asserted that Source No. 2 was identified as releases from a vapor degreaser. General Dynamics stated that “[i]n accord ance with its instructions, MACTEC identified two potential sources of contamination on the Gould [Gen eral Dynamics Longwood] site. . . . The second potential source was an alleged release from a vapor degreaser located in the sout heast corner of Building 3 at the Gould [General Dynamics Longwood] site, wh ich is referred to in the HRS Record as ‘Source 2.’” 1306 1307 1308 1309 1310 1311 1312 Response : Source No. 2 was identified at proposal as a contaminated soil source. 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 While the source was described as in the vicinity of a vapor degreaser, the vapor degreaser was not included as a source in the HRS evaluation.

Source 2 was correctly identified as a source with the source type contaminated soil consistent with HRS Section 1.1, Definitions, which defines source as: Any area where a hazardous substance has been deposited, stored, disposed, or placed, plus those soils that have become contamin ated from migration of a hazardous substance.

As explained in section 3.12, Origin of Source Contamination, of this support document, Source 2 was correctly identified as a source with the sour ce type contaminated soil consistent with the HRS section 1.1, Definitions

. Page 23 of the HRS documentation record at proposal identifies Source 2 as a contaminated soil source: Number of source : 2 1328 Name of source : Contaminated soil in the southeaster n corner of Building 3 (vicinity of the former vapor degreaser) 1329 1330 1331 Source Type : Contaminated soil 1332 1333

43General Dynamics Longwood NPL Listing Support Document September 2010

Also, page 23 of the HRS documentation record at proposal, under the heading Description and Location of the Source, described the contaminated soil as bein g in the vicinity of a former vapor degreaser, but there was no statement that the degreaser was the origin of the contamination. 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 Thus, General Dynamics’ claim that the contaminatio n in the soil definitively came from a release from a vapor degreaser in the HRS documentation record is incorrect, although the record does suggest that possibility. However, regardless of the possible origin of the contamina tion, as explained in section 3.12, Origin of Source Contamination, of this support docum ent, the soil source was identified consistent with the HRS. The origin of the contamination need not be determined for this identification.

Regarding the commenter’s assertions that Source No . 2 was established by findings from the MACTEC report, the HRS documentation record did not rely on data presented within this report for establishing Source No. 2. While information gained from the MACTEC report was used in the HRS documentation record, Source No. 2 was established from data collected from the 2005 Remedial Investigation conducted by URS (see section 3.12, Identification of a Source and Origin of Source Contamination, of this support document).

This comment has no effect on the site score or the decision to place this site on the NPL. 

### 3.15 Source Type

Comment : Brown and Caldwell asserted that EPA’s contractor incorrectly characterizes the “Source Type” as contaminated soil for Source No. 2, and that EPA’s contractor made an incorrect interpretation of sample results labeled as “soils” on pp. 18-28 of the HRS documentation record at proposal; Brown and Caldwell claimed that the samples identified as “so ils” are actually “saturated aquifer materials or, at the very worst, in one case, w ithin the capillary fringe of the upper water-bearing zone.” 1354 1355 1356 1357 1358 1359 Response The source type for Source 2was correctly id entified as contaminated soil in the HRS documentation record at proposal. The HRS does not contain a definition for “soil”; however, a common definition defines it as “the loose surface material of the earth in which plants grow usu., consisting of disintegrated rock with an admixture of organic matter and soluble salts,” and “the surface earth of a particular place with reference esp. to its composition or its adaptability.” ( 1360 1361 1362 1363 Webster’s New International 1364 Dictionary , 3d ed., s.v. “soil.” ) 1365 1366

44General Dynamics Longwood NPL Listing Support Document September 2010

Page 23 of the HRS documentation record describes Source No. 2 as “contaminated soil located beneath the southeastern corner of Building 3 in the vicinity of the former vapor degreaser.” Additionally, page 26 of the HRS documentation record at proposal unde r the heading Hazardous Substances Available to a Pathway, states that: 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 The subsurface soil sample collected from Source No. 2 contained an elevated concentration of 1,1-DCE (Refs. 49, Figure 3; 77, pp. 15, 34) (also see Table 5 of this HRS documentation record). Source No. 2 c onsists of an area of contaminated soil located in the southeastern portion of Buildi ng 3 on the General Dynamics property (Ref. 16, pp. 14, 15, Exhibit 1).

Based on the common interpretation of soil, as supporte d by the definition above, earth materials in the capillary fringe 4 of the ground water are still considered so ils for HRS purposes. The amount of water saturation is not a determining factor in whether or not a material can be considered “soil.”

Therefore, Source No. 2 was assigned the source type “contaminated soil” consistent with the HRS (see section 3.12, Origin of Source Contamination, of th is support document). Source No. 2 was established as contaminated soil according to the HRS definition of “source” because it is composed of soil that came to be contaminated due to migration.

This comment has no effect on the site score or the decision to place this site on the NPL. 

### 3.16 Source Background

Comment : Brown and Caldwell questioned the adequacy of the soil samples used to document the presence of soil contamination above background soil levels at Source No. 2 and the nomenclature used in referring to them. Specifically, Brown and Ca ldwell alleged that establishment of Source No. 2 resulted from comparison of samples from the SEC site to samples on the General Dynamics Longwood site. Brown and Caldwell further commented that “[t]he Sprague site sample results are called ‘background concentrations’ and the Gould Property [General Dynamics property] sample results are termed as ‘contaminated concentrations’ in the Record.” 1389 1390 1391 1392 1393 1394 1395 1396 Response: The background samples used to document that th e Source 2 soil came to be contaminated due to migration were appropriate for this purpose. 1397 1398 1399

4 “The porous material just above the water table which may hold water by capillarity (a property of surface tension that draws water upwards) in the smaller void spaces” ( from EPA’s Terms of Environm ent: Glossary, Abbreviations and Acronyms, available at http://www.epa.gov/OCEPAterms/cterms.html ). 45General Dynamics Longwood NPL Listing Support Document September 2010

The HRS Section 1.1, Definitions, defines source as: 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 Any area where a hazardous substance has been deposited, stored, disposed, or placed, plus those soils that have become contamin ated from migration of a hazardous substance.

The HRS does not direct how to identify that soils have “come to be contaminated due to migration.” That the soils came to be contaminated was documen ted in the HRS documentation record at proposal by demonstrating the contaminant levels in the soil are gr eater than in surrounding soil. Page 24 of the HRS documentation record at proposal, under section 2.2.2, Hazardous Substances Associated with the Source, discussed the method by which hazardous substances were documented within Source No. 2, and the hazardous substance detected in the source soil sample. It states that: subsurface soil samples, SB-006-3, SB-017-3, and SB-037-3, were collected from the General Dynamics and SEC properties at the same depth (3 feet bls) and were used to establish background concentrations (Refs. 49, Figure 3; 75, pp. 13, 20; 80, pp. 27, 29). The contaminated subsurface soil sample, SB -038-03, was collected in the area of the former vapor degreaser located in the southeast ern corner of Building 3 at a depth of 3 feet below the building floor. The sample was collected inside the building by coring through the concrete using a direct push rig. (R efs. 16, pp. 14, 15, Exhibit 1; 49, Figure 3; 80, pp. 29, 30). The background subsurface soil samples and contaminated subsurface soil samples were collected from the same soil type (urban land, 0 to 12 percent slopes), at the same depth, during the same sampli ng event, and in accordance with the same sampling procedures.

Table 1 in section 3.12, Identification of a Source a nd Origin of Source Contamination, of this support document presents the analytical data used in establishing Source No. 2.

The Source No. 2 background samples were collected from both the General Dynamics property and from the hydraulically upgradient SEC property, and are docu mented to have similar sample characteristics to the contaminated sample. Adequate similarity between the source soil sample and the background soil samples ensured that analytical variation of contaminants due to dissimilar soil types or sampling collection methods were minimized. Therefore, the source background samples were valid in the determination of a contaminated soil source, as the in creases in hazardous substa nces in the source sample was shown to not be due to differences in sample media.

As shown in the data above, the 1,1-DCE levels in the soil sample from Source No. 2 are significantly greater than those detected in the soil background samples. Therefore, it was concluded the 1,1-DCE came to be in the source sample due to migrati on from operations at the General Dynamics property. Additionally, both soil and ground water samples collected at the site and at the hydraulically upgradient SEC property indicate that high levels of 1,1-DCE are not found at the same concentrations everywhere in the vicinity of the site. Specifically, page 23 of the HRS documentation record at proposal documents a

46General Dynamics Longwood NPL Listing Support Document September 2010

significant increase of 1,1-DCE in the ground water unde rlying or downgradient of Source No. 2, and that the concentration of the contaminant in that location is significantly higher than any other sample taken from the General Dynamics or SEC properties. It states: 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 During the 2005 RI conducted by URS, two direct push ground water samples were collected from ground water underlying Source No. 2, DPGW-22 and DPGW-34. During the RI, the greatest concentration of 1,1-DCE was detected in direct push ground water sample DPGW-34 at a depth of 22 feet bls. This sample contained the highest concentrations of 1,1-DCE detected in direct push ground water samples collected during the 2005 RI from the General Dynamics or SEC properties (Ref. 8, Figures 4-29 through 4-32, 4-38, 4-39) (see Figure 2 of this HRS documentation record ). In addition, a review of analytical results from 1989 to 2005 indicate that the concentrations of 1,1-DCE detected in direct push ground water sample DPGW-34(22 ′ ), collected from ground water underlying Source No. 2, contained the high est concentrations of 1,1-DCE detected during ground water investigations con ducted at the General Dynamics and SEC properties. The hazardous substance 1,1-DCE was detected in ground water underlying or downgradient of Source No. 2 at significantly higher levels than the levels of 1,1-DCE documented anywhere else on the General Dynamics Longwood site, or the hydraulically upgradient SEC property. This indicates that a migration of solvents in the ground water from releases at the SEC property has not impacted the samples used to establish Source No. 2, and contaminants from Source 2 must have come from operations on the General Dynamics property.

Furthermore, even if the source soil background sampl es were affected by releases at the SEC property, the Source No. 2 contaminated soil sample still exhibits a significant increase in 1,1-DCE when compared to the background samples.

This comment has no effect on the HRS site score or the decision to place the site on the NPL. 

### 3.17 Associating Substanc es with Source No. 2

Comment : General Dynamics and Brown and Caldwell questi oned the association of chlorinated solvents with Source No. 2. General Dynamics commented that “[a]lthough the HRS Record provides a laundry list of solvents that were historically used in the industry to clean printed circuit boards, the HRS Record acknowledges that TCE was the only solvent used in the vapor degreaser at the Gould [General Dynamics Longwood] site.” 1469 1470 1471 1472 1473 1474 1475 General Dynamics stated that:

47General Dynamics Longwood NPL Listing Support Document September 2010

in the Record describing the operational a nd regulatory history, PCE is referenced repeatedly, and seems to imply by repetition that PCE was used at the Gould [General Dynamics Longwood] site. To clarify, U.S. EPA never alleges that PCE was used at the Gould [General Dynamics Longwood] site and there is no evidence that PCE was used at the Gould [General Dynamics Longwood] site. 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 General Dynamics asserted that: This is consistent with th e deposition testimony of former General Dynamics’ employees. . . . These former employees were also unaware of releases of solvents or other hazardous substances at the site. . . . These employees testified as to the absence of floor drains in the manufacturing areas at the Gould [General Dynamics Longwood] site. . . . Similarly, these employees were instructed not to pour TCE (or any other hazardous materials) down the drain, on the floor, or onto the ground. . . . Rather, spent TCE was collected in barrels and picked up for off-site disposal by a chemical disposal company. . . . As such, there is no evidence of actual re leases of TCE (or any other solvent) to the soil or groundwater at the Gould [General Dynamics Longwood] site.

Discussing solvent usage in operations at the Gene ral Dynamics facility, Brown and Caldwell asserted that “[p]rinted circuit board fabrication by Genera l Dynamics and its successors as described on p. 14 of the Record is consistent with the use of TCE (not 1,1,1-TCA) for photo-resist stripping during the manufacturing process.”

Response : The hazardous substance 1,1-DCE, a chlorinated solvent, was correctly associated with Source No. 2 according to HRS criteria. 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 HRS Section 2.2.2, Identify hazardous substances associated with a source , directs the evaluator: For each of the three migration pathways, consider those hazardous substances documented in a source (for example, by sampling, labels, manifests, oral or written statements) to be associated with that source when evaluating each pathway.

The analytical data used in establishing Source No. 2 are shown in Table 1 in section 3.12, Identification of a Source and Origin of Source Contamination, of this support document. The hazardous substance 1,1- DCE was associated with a source by demonstrati ng it was in a source soil sample above background levels, as soil sample SB-038-03 was documented to c ontain 1,1-DCE at an elevated concentration above the background soil samples. Therefore, it was concluded that the 1,1-DCE came to be in the source soil sample due to migration from operations on the General Dynamics property (see section 3.16, Source Background, of this support document).

The HRS documentation record at proposal describes other chlorinated solvents such as TCE and PCE as commonly used in printed circuit board manufact uring cleaning processes. Although these other

48General Dynamics Longwood NPL Listing Support Document September 2010

chlorinated solvents or their degradation products are discussed as present or possibly used at the site, they are not identified as associated with Source No. 2. Only 1,1-DCE, and its association with Source No. 2, is used in the scoring of this source. 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 The discussion of other solvents within the HRS documen tation record at proposal is intended to illustrate the general usage of solvents at the site, and no speci fic solvent is singled out as having exclusively been used at the General Dynamics Longwood site. That TCE is the only confirmed solvent used at the General Dynamics facility does not preclude the use of ot her solvents at the facility. In fact, testimony from former General Dynamics employees indicate that TCE and other solvents, such as 1,1,1-TCA, may have been used in former operations at the site. The deposition testimony by Quentin Glynn (Reference 88 of the HRS documentation record at proposal) indi cates the usage of 1,1,1-TCA at the site, as the former General Dynamics employee testified using a product called “1,1,1-Tric,” in the cleaning of printed circuit boards. Trichloroethylene and PCE would not have correctly been identified with “1,1,1-” preceding their names, according to chemical nomenc lature, while 1,1,1-TCA would have been. This indicates the use of 1,1,1-TCA at the General Dynamics Longwood site.

In addition, a testimony of Cecil Carter (Reference 16 of the HRS documentation record at proposal), another former General Dynamics employee, indicates the use of PCE at the General Dynamics facility, as the deponent responded to questioning about the use of a product called “perc.” PCE is known as “perchloroethylene,” and is commonly referred to as “perc.” Although this deponent was not aware of the use of this product in the vapor degreaser, PCE u se at the General Dynamics facility was indicated.

Regarding Brown and Caldwell’s assertion that former em ployees testified as to the lack of spills, and/or the lack of careless practices of handling solvents (either in usage or disposal), it cannot be construed that these testimonies establish that soil or ground water contamination at the General Dynamics Longwood site could not have been due to the use of solvents at the site. Given the consid erable length of operations at the facility, and the fact that General Dynamics has been unable to produce historical information regarding solvent use at the General Dynamics facility for the entire length of operations and for all of their operations, limited deposition testimonies are not sufficient to exclude that the mishandling of solvents contributed to the contamination at the site.

This comment has no affect on the HRS site score or the decision to place the site on the NPL.

49General Dynamics Longwood NPL Listing Support Document September 2010 

### 3.18 Likelihood of Release - Background 1549

Comment : Brown and Caldwell challenged the adequacy of the ground water sample locations used as representative of upgradient ground water conditions for establishment of observed releases. Brown and Caldwell asserted that there is a “ fundamental scientific error in the interpretation of what areas on the Sprague property represent actual ‘background’ in the Record [emphasis in original comment],” and that: 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 data utilized for comparison are actually in the middle portions of groundwater contaminant plumes that originated on the Sprague property. This is apparent from examination of the groundwater concentra tion trends and plume geometries over time as well as the presence and spatial distributions of both abiotic and biotic degradation products, and aquifer characteristics re lative to groundwater velocity.

Brown and Caldwell stated that their analysis: bolsters other elements of Brown and Caldwe ll’s evaluation of site-specific information about geology, hydrogeology, and contaminant distribution and means that contamination that is present today in groundwater beneath the Gould Property [General Dynamics property] has originated solely from sources on the Sprague site [emphasis in original comment]. Attribu ting groundwater VOC contamination at the Gould Property [General Dynamics property] to historic manufacturing operations by General Dynamics and its predecessors is not technically justified.

Response : Background levels of 1,1-DCE were adequate ly established for the identification of an observed release to ground water by chemical analysis. 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 HRS Section 2.3, Likelihood of release , states The minimum standard to establish an observed release by chemical analysis is analytical evidence of a hazardous substance in the medi a significantly above the background level.

This HRS section also refers to HRS Table 2-3 which identifies the significant increase criteria for identifying an observed release by chemical analysis. This table directs that when the sample measurement (i.e., the chemical concentration of a ha zardous substance in a candidate release sample) is greater than or equal to the sample quantitation limit, an observed release can be established: If the background concentration is not detected (or is less than the detection limit), an observed release is established when the sample measurement equals or exceeds the sample quantitation limit. If the background concentration equals or ex ceeds the detection limit, an observed release is established when the sampl e measurement is 3 times or more above the background concentration.

HRS Section 3.1, Likelihood of release , states: 50General Dynamics Longwood NPL Listing Support Document September 2010

For an aquifer, evaluate the likelihood of re lease factor category in terms of an observed release factor or a potential to release factor. 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 HRS Section 3.1.1, Observed release , states: Establish an observed release to an aquifer by demonstrating that the site has released a hazardous substance to the aquifer. Base this demonstration on either:

• Direct observation . . .

• Chemical analysis – an analysis of ground water samples from the aquifer indicates that the concentration of hazardous substa nces(s) has increased significantly above the background concentration for the site (see section 2.3). Some portion of the significant increase must be attributable to the site to establish the observed release, except: when the source itself consists of a ground water plume with no identified source, no separate attribution is required.

At this site, observed releases by chemical analysis of 1,1-DCE, cis-1,2-DCE, trans-1,2-DCE, TCE, and vinyl chloride were identified at the time of proposal . However, as explained in section 3.10, Source No. 1 and Associated Observed Releases, of this s upport document, the HRS documentation record at promulgation has been revised to document only 1,1- DCE as the hazardous substance associated with the observed release at the General Dynamics Longwood site.

The relevant samples used in identifying an ob served release from Source No. 2 are shown in HRS documentation record pp. 40, 41, 52. Background and release samples were collected at a depth of 22 feet to ensure comparability. Analytical resu lts for samples DPGW-23(22’) and DPGW-26(22’) 5 , the background samples used in establishing observe d release, are presented on Table 12 of the HRS documentation record at proposal. The hazardous subs tance 1,1-DCE was not detected in sample DPGW26(22’), and was detected at 9.2 microgram per liter (μg/L) in sample DPGW-23(22’). Table 14 on page 52 of the HRS documentation record at proposal presen ts sample DPGW-34(22’), used to establish an observed release, as having a concentration of 26,500 μg/L of 1,1-DCE. These results are presented on Table 2 below.

5 Note that for these 2005 investigation samples, the sample ID consists of a sample type identifier (“DPGW” stands for direct-push ground water), a location code (e.g., “-23”), and a depth code (e.g., “(22’)” indicates a depth of 22 feet below ground surface). 51General Dynamics Longwood NPL Listing Support Document September 2010

Table 2: Samples Used in Establishing Observed Release by Chemical Analysis 1622 Background Samples Used in Establis hing Observed Release from Site Sample ID Hazardous Substance Concentration Reporting Limit References

DPGW23(22') 1,1-DCE 9.2 μg/L 0.50 μg/L 28, p. 1; 51, pp. 7 through 11; 72, p. 33DPGW26(22') 1,1-DCE 0.50U μg/L 0.50 μg/L 28, p. 1; 51, pp. 7 through 11; 72, p. 65 Contaminated Ground Water Samples Used in Establishing Observed Release from SiteDPGW34(22') 1,1-DCE 26,500 a μg/L 1.0 μg/L 28, pp. 1- 3; 51, pp. 2 through 6; 77, pp. 9,10 1623 Notes : 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 a Result if from Run #2 DCE Dichloroethylene DP Direct push μg/L micrograms per liter ' Feet (#) Depth of direct push ground water sample in feet

The HRS documentation record at proposal established an observed release by chemical analysis at the site, as a significant increase (more than 3-fold) in the concentration of the hazardous substance 1,1-DCE was documented above background samples. The HRS requirement for assigning a likelihood of release factor value of 550 was met.

Specific comments regarding the background level used to establish an observed release are addressed in the following subsections of this support document:

• 3.18.1 Effects of Pump-and-Treat System

• 3.18.2 Selection of Background Samples

• 3.18.3 Temporal Differences Due to Flow Rate

52General Dynamics Longwood NPL Listing Support Document September 2010

3.18.1 Effects of Pump-and-Treat System 1643 Comment : Brown and Caldwell asserted that the effects of the ground water pump and treat system on ground water flow gradients was not considered in selecting background sample locations. Brown and Caldwell specifically argued that: 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 EPA’s contractor provides absolutely no c onsideration to the temporal impact from operation of the existing groundwater pump-an-tr eat system that was installed by GARFI along the northern border of the Sprague site.

Brown and Caldwell remarked that “the pump and tr eat system has significantly altered ground water flow patterns between the Gould [General Dynamics property] and Sprague properties from those originally depicted in 1992 by Sprague’s consultant,” and that “[t]hese omissions are a fatal deficiency in the scoring process for the Gould Property [General Dynamics property].”

Brown and Caldwell stated that the natural ground wate r movement in the vicinity of the site has caused hazardous substances and their degrad ation products released on the Spra gue site to migrate beneath the General Dynamics Longwood site, and “human mani pulation of the groundwater has also caused pronounced changes in local groundwater flow patterns.”

Brown and Caldwell claimed that the alteration of ground water flow patterns by the Sprague remediation system is well known, yet not taken into consideration by EPA’s contractor, which Brown and Caldwell asserted is “another significant error in the analysis that results in an inaccurate HRS score” and that: It is likely that the addition of the N a nd NW groundwater flow vectors has pulled a greater mass of released VOC materials from the Sprague property onto the Gould Property [General Dynamics property] (as comp ared to the prior direction before 1996 when zone A was flowing more toward Source No. 2).

Response : Ground water flow gradient data have been collected from the General Dynamics Longwood site over multiple years, as presented in the references to the HRS documentation record at proposal (see section 3.11.1, Consideration of Pump-and-Treat System, of this support document). Analysis of this data indicates that there has been a generally northward movement of ground water in the vicinity of Source No. 2 and the eastern portion of the site whether or not the pump and treat system was operating. Upon analysis of ground water flow gradient data from historic investigations, the operation of the remediation system may have had extremely local effects on flow direction but has not significantly changed the overall northerly ground water flow gradients in the su rficial aquifer in the eastern portion of the site. (This trend is supported by Exhibit J of Brow n and Caldwell’s comments [docket ID EPA-HQ-SFUND1669 1670 1671 1672 1673 1674 1675 1676 1677

53General Dynamics Longwood NPL Listing Support Document September 2010

2009-0067-0006.1], which documents a generally no rthward ground water flow during various time periods). 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 Additionally, using the commenter’s assertions regard ing subsurface porosity and ground water flow rates at the site, calculations reveal that the remedial well (RW-2A) located hydraulically upgradient of Source No. 2 and the observed release location does not pump a significant portion of the estimated ground water flow in the upper surficial aquifer. As detailed in Attachment 2 of this support document, RW-2A would only process approximately 14 – 33% of the theoreti cal ground water flow passing the pump-and-treat system within the upper surficial aquifer. This rate of ground water withdrawal is not expected to have created a subsurface ground water “dam” that would have totally blocked the movement of ground water and contaminants from the SEC property to the Genera l Dynamics property, and did not affect the overall lateral flow direction except in the immediat e vicinity of the pump-and-treat system.

Since the pump-and-treat system did not significantl y alter the overall northerly flow in the eastern portion of the site, and the background samples used in the establishment of the observed release in this area are south of and upgradient of the observed release, they are representative of background conditions for this evaluation.

This comment has no effect on the HRS site score or the decision to place this site on the NPL.

3.18.2 Selection of Background Samples

Comment : Brown and Caldwell claimed that EPA did not adequately consider the location of potential upgradient sources in selecting background sample lo cations, citing as an example, a contaminated sample under the SEC property. 1699 1700 1701 1702 1703 1704 1705 1706 Brown and Caldwell asserted that an “upgradient b ackground sample on the Sprague property that was not considered in the Record is the 25,100 μ g/L concentration of TCE measured in DPGW-28 at approximately 42 feet bgs.”

Response : The upgradient background sample referenced by the commenter is not relevant to the identification of an observed release of 1,1-DCE in the eastern portion of the site. First, while the sample (DPGW-28) does contain high levels of TCE, the we ll from which it was collected is located in the western portion of the SEC property and is not directly upgradient of the observed release sample (DPGW-34). Therefore, sample DPGW-28 is not considered a background sample for identifying the 1707 1708 1709 1710 1711

54General Dynamics Longwood NPL Listing Support Document September 2010

55 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 observed release in the eastern part of the site (See Figure 7 in section 3.19, Likelihood of Release – Attribution, of this support document for a presentation of the area considered upgradient of the observed release location).

Second, chlorinated solvents preferentially dissolve or move as free product into the ground water and sink to lower levels of the subsurface (see section 3.12.3, Contamination from Upgradient Ground Water Releases, of this support document). Sample DP GW-28, the sample referenced by the commenter, contained high levels of TCE at 42 feet bls, wher eas, sample DPGW-34, the observed release sample, was collected at 22 feet bls. A migration of solvents in the ground water from the SEC property toward the General Dynamics property would be expected to ha ve a downward component; thus, the contamination documented at DPGW-28 would not likely have had a significant impact on the observed release for this site.

Third, the observed release being evaluated was documented to contain significant levels of 1,1-DCE— not TCE. The highest level of 1,1-DCE at the samp le location referred to by the commenter (DPGW-28) was 453 μg/L, which is less than a factor of three when compared to the concentration of 26,500 μg/L of 1,1-DCE found in the observed release sample location (DPGW-34). Therefore, even if the sample location referred to by the commenter (DPGW-28) were an upgradient sample of the observed release in the eastern portion of the site, it would not contradict the finding of a significant increase of 1,1-DCE over background levels, and if used as a background level, an observed release would still have been identified. Figure 5 below presents the aforementioned samp le location (DPGW-28) referred to by the commenter, and its concentration of 1,1-DCE in relation to the site.General Dynamics Longwood NPL Listing Support DocumentSeptember 2010Figure 5: Depiction of DPGW-2817351736173717381739174017411742174317441745174617471748174917501751175217531754175517561757175817591760176117621763176417651766176717681769177056General Dynamics Longwood NPL Listing Support Document September 2010

Fourth, even if releases of TCE from the sample location referred to by the commenter were to migrate directly towards the Source No. 2 release location, th e TCE would not have degraded to 1,1-DCE, as the commenter asserted (see section 3.19.1, Degradation Products, of this support document). Yet, 1,1-DCE is the predominant chlorinated solvent docu mented at the observed release location. 1771 1772 1773 1774 1775 1776 1777 1778 This comment has no effect on the HRS site score or the decision to place this site on the NPL.

3.18.3 Temporal Differences Due to Flow Rate

Comment : Brown and Caldwell argued that the high gr ound water flow rate at the site was not accounted for in establishing background contam ination levels. Brown and Caldwell asserted that: 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 the groundwater velocities at the Sprague site and the Gould Property [General Dynamics property] are on the order of 300 to 450 feet/year in the ‘A’ zone and 50 to 75 feet/year in the ‘B’ zone of the upper aquifer. This mean s that a particle of water originating on the Sprague site when operations reportedly began there in 1959 could have traveled 15,000 to 22,500 feet by now in the ‘A’ zone and 2,500 to 3,750 feet in the ‘B’ zone some 50 years later.

Brown and Caldwell continued that: The rates of movement of the TCE and 1,l-DCE plumes that emanate from the Sprague property and then move downgradient beneath the Gould Property [General Dynamics property] are somewhat retarded by sorption to soil particles in the aquifer. The retarded groundwater travel distances then range from 5,170 feet to 7,760 feet for 1,l-DCE in the ‘A’ zone and 860 to 1,290 feet in the ‘B’ zone. For TCE, the corresponding distances are 4,050 to 6,080 feet in the ‘A’ zone and 680 to 1,010 feet in the ‘B’ zone. . . . The distances from the southern boundaries of the Sprague site to the far northern boundaries of the Gould Property [General Dynamics propert y] are much less than the retarded travel distances in the ‘A’ zone, approximately 750 feet to 1,700 feet. These cross-property distances are almost identical to the travel distances calculated for the ‘B’ zone. A complicating factor is that there is a net dow nward vertical gradient between the ‘A’ and the ‘B’ zones, which would tend to increase th e potential length of travel of the plumes for a specified period of time.

Response : It is recognized the high ground water flow rate certainly could have caused migration of hazardous substances from the SEC property to under the General Dynamics property; however, there is no evidence that 1,1-DCE or a parent substance could ha ve migrated via this route in sufficient quantity to cause the significant increase in 1,1-DCE levels found in the release well sample collected from the eastern part of the General Dynamics property. 1804 1805 1806 1807 1808 1809

57General Dynamics Longwood NPL Listing Support Document September 2010

58 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 The HRS does not identify that flow rate should be considered in choosing a background location or in establishing background levels. However, since for HR S purposes, background levels are used to show a significant increase in contaminant level due to a release, it is relevant to consider that an increase in a contaminant level as a result of release from an upgradient area that has then migrated to a downgradient sampling location. Such information was incorporated into the evaluation.

Regarding the observed release of 1,1-DCE in the east ern portion of the General Dynamics property, page 44 of the HRS documentation record at proposal id entifies background direct-push locations DPGW-23 and DPGW-26, from each of which one sample was taken at a depth of 22 feet bls. The locations of these wells were presented in Figures 4-29 through 4-32 of Reference 8 to the HRS documentation record at proposal. The highest 1,1-DCE concentration in the two background samples was 9.2 μg/L and was thus used as the background level.

Page 52 of the HRS documentation record at pro posal identified the corresponding release well, DPGW34. The location of this well was also presented on Figures 4-29 through 4-32 of Reference 8 of the HRS documentation record. The release sample came from a depth of 22 feet bls. The 1,1-DCE concentration in the release well sample was 26,500 μg/L. Howe ver, as discussed in section 3.19, Likelihood of Release – Attribution, of this support document below, the references to the HRS documentation record at proposal contained ground water sampling data from over 34 sample locations upgradient of the release sample location on the eastern side of the Genera l Dynamics property and on the SEC property, from investigations performed as early as 1988, and having a range in depths of approximately 10 to 42’ bls. These data have been reviewed and the highest 1,1-DCE concentration found at any sample location upgradient of the release sample location was 1,700 μg/L (see Figure 6 below, and section 3.19, Likelihood of Release – Attribution, of this suppor t document). Using 1,700 μg/L as a background level would still result in a more than 3 -fold increase in 1,1-DCE levels in the observed release sample. In addition, Brown and Caldwell asserted that the pr incipal decomposition product of 1,1,1-TCA is 1,1- DCE, and the highest 1,1,1-TCA concentration in any of these sample locations is 520 μg/L. Thus, if all of the 1,1,1-TCA degraded and moved to the rel ease sample location, it would still not explain the concentration of 1,1-DCE levels in the release sample DPGW-34.General Dynamics Longwood NPL Listing Support DocumentSeptember 20105918391840184118421843184418451846184718481849185018511852185318541855185618571858185918601861186218631864Figure 6: Reviewed Upgradient Sample LocationsGeneral Dynamics Longwood NPL Listing Support Document September 2010

Thus, while the commenter raised a theoretical po ssibility that the background well locations and the timing of the sampling could possibly have resulte d in the background sample not assuring that the contamination in the release well did not come from the SEC property, there is no evidence that this possibility actually occurred, and there are more than 15 years of sampling data indicating it did not

occur. 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 Comments regarding the degradation of solvents are discussed in section 3.19.1, Degradation Products, of this support document.

This comment has no effect on the site score or the decision to place this site on the NPL.



### 3.19 Likelihood of Release – Attribution

Comment : General Dynamics asserted that EPA has not do cumented that the ground water contamination under the General Dynamics property can be attribut ed to releases associated with General Dynamics operations and not attr ibuted to releases attributable to SEC operations. General Dynamics alleged that: 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 No evidence has been presented to show th at General Dynamics contaminated the Gould [General Dynamics Longwood] site, and no evidence has been presented that anyone other than Sprague Electric Company (SEC) contaminated the Gould [General Dynamics Longwood] site.

Regarding associating the observed release substance, 1,1-DCE (or its possible parent 1,1,1-TCA) usage in previous operations at the General Dyna mics facility, Brown and Caldwell stated that: [p]rinted circuit board fabrication by Genera l Dynamics and is successors as described on p. 14 of the Record is consistent with the use of TCE (not 1,1,1-TCA) for photo-resist stripping during the manufacturing process.”

Brown and Caldwell continued that: Direct observation by people who were pr esent when operations were conducted at the Gould Property [General Dynamics property] also does not support a conclusion that there was an observed release. Depositions ha ve been taken of a number of former employees and none have tes tified to having observed or known about any release of VOCs to soil or groundwater.

Brown and Caldwell also stated that: EPA’s contractor should have concluded, based on the overwhelming evidence discussed in the public record available to them, that there was no ‘Observed Release’ at the Gould Property [General Dynamics property], nor is there any evidence of a release to soil which could potentially be released to groundwater

60General Dynamics Longwood NPL Listing Support Document September 2010

[emphasis in original comment]. Had they done so, then the value for the HRS Site Score would have been zero. 1903 1904 1905 Response : An observed release of 1,1-DCE by chemical analysis, including attribution of the release to the General Dynamics-Longwood site, was established consistently with the HRS regulation. This release was attributed to the site—not to a company or its operations. At the time of proposal, observed releases of TCE, cis-1,2-DCE, trans-1,2-DCE, and vi nyl chloride were also identified, but these releases have been dropped from the HRS scoring (see section 3.10, Source No. 1 and Associated Observed Releases, of this support document). 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 HRS Section 2.3, Likelihood of release , presents the basic requirements for identifying an observed release by chemical analysis: The minimum standard to establish an observed release by chemical analysis is analytical evidence of a hazardous substance in the medi a significantly above the background level. Further, some portion of the release must be attributable to the site.

HRS Table 2-3 identifies the observed release by chemical analysis criteria. This table requires: If the background concentration is not detected (or is less than the detection limit), an observed release is established when the sample measurement equals or exceeds the sample quantitation limit.

. . . . . If the background concentration equals or ex ceeds the detection limit, an observed release is established when the sampl e measurement is 3 times or more above the background concentration.

HRS Section 3.1, Likelihood of release , and its subsections provide the specific requirements for assigning a likelihood of release factor category value for the ground water migration pathway: For an aquifer, evaluate the likelihood of re lease factor category in terms of an observed release factor or a potential to release factor.

HRS Section 3.1.1, Observed release , states: Establish an observed release to an aquifer by demonstrating that the site has released a hazardous substance to the aquifer. Base this demonstration on either:

• Direct observation . . . .

• Chemical analysis—an analysis of ground water samples from the aquifer indicates that the concentration of hazardous substance(s) has increased significantly above the background concentr ation for the site (see section 2.3). Some portion of the significant increase mu st be attributable to the site to

61General Dynamics Longwood NPL Listing Support Document September 2010

establish the observed release, except: when the source itself consists of a ground water plume with no identified source, no separate attribution is required. 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 A significant increase in the concentration of 1,1- DCE was documented as the release sample DPGW34(22’) contained 1,1-DCE at a concentration (26, 500 μg/L) greater than 3-times the higher of two upgradient background concentrations (9.2 μg/L) in samples DPGW-23(22') and DPGW-26(22') collected at the same depth of 22 feet. (See section 3.18 , Likelihood of Release – B ackground, of this support document.)

That the significant increase in 1,1 DCE is attri butable to the General Dynamics Longwood site was demonstrated on page 54 of the HRS documentation record at proposal, under the heading Attribution: In 2005, 1,1-DCE was detected at an elevat ed concentration in a subsurface soil sample collected from Source No. 2 . . . During the 2005 RI conducted by URS, two direct push ground water samples were collected from ground water underlying Source No. 2, DPGW-22 and DPGW-34. The greatest concentration of 1,1-DCE was detected in direct push ground water sample DPGW-34 at a depth of 22 feet bls. This sample contained the highest concentration of 1,1-DCE detected in direct push ground water samples collected during the 2005 RI from the General Dynamics or SEC properties (Ref. 8, Figures 4-29 through 4-32) (see Figure 2 of this HRS documentation record). In addition, analytical results from 1989 to 2005 indicate that the concentration of 1,1-DCE detected in direct push ground water sample, DPGW-34(22' ), collected from ground water underlying Source No. 2 contained the highest concentration of 1,1-DCE (26,500 μg/L) detected during ground water investigations con ducted at the General Dynamics and SEC properties.

. . . . . Ground water samples collected at the adjacent SEC property also contain TCE and its degradation products. However, ground water samples collected downgradient of SEC sources and upgradient of Source Nos. 1 a nd 2 on the General Dynamics property were used to differentiate between sources of contamination at the SEC and General Dynamics properties. When compared to background samples, ground water samples collected downgradient of Source Nos. 1 and 2 at the General Dynamics property document chlorinated solvent releases in ground water underlying and downgradient of Source Nos. 1 and 2.

Thus, the significant increase in 1,1-DCE was attribut ed to the site, based on the finding that 1,1-DCE was associated with a site source, and that upgradie nt background concentrations of DCE found at the SEC site indicated that releases from the SEC site di d not contribute significantly to the increase of the concentration of 1,1-DCE in the release sample.

Furthermore, because of ground water flow rates in th e range of feet per day, EPA has reviewed past sampling and analysis data from sample locations upg radient of the release sample location (see section

62General Dynamics Longwood NPL Listing Support Document September 2010

63 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 3.18.3, Temporal Differences Due to Flow Rate, of this support document). From this review, it is evident that 1,1-DCE was detected in ground water at the release sample location underlying the General Dynamics property at a significantly higher level than the levels of 1,1-DCE documented at any other location on the General Dynamics property, or th e hydraulically upgradient SEC property.

To illustrate this, the analytical and sampling data from 1988 to 2006 available in the references to the HRS documentation record at proposal have been review ed to characterize the contamination levels in the ground water hydraulically upgradient of the release sample; these data include historical results for monitoring well samples from the A-zone and B-zone of the surficial aquifer and direct push ground water samples. The sample locations selected for re view are from the area depicted in Figure 7 below, which presents the extent of the area considered hydraulically upgradient of the release sample. Analysis of historical ground water elevation data indicates that there has been a generally northward movement of ground water in the vicinity of Source No. 2 – both in the A-zone and B-zone of the surficial aquifer, and variations due to the pump-and-treat system do not ap pear to have a significant impact on the overall flow direction between the background and release sample locations used to establish the observed release in the eastern part of the General Dynamics site. (See s ection 3.11, Description of Pathway, of this support document). The western-most extent of the upgradient area in Figure 7 was selected to be as inclusive as reasonably possible based upon analysis of the gro und water flow direction maps provided in the references to the HRS documentation record at propo sal. As discussed in previous sections of this support document, a generally northern flow directi on of ground water has been documented from various investigations at the site.General Dynamics Longwood NPL Listing Support DocumentSeptember 201064Figure 7: Area Considered Hydraulically Upgradient of Observed Release LocationNote: The hatch-marked area represents the area hydraulically upgradient of the observedrelease sample. Information from samplestaken from this area is presented in Attachment 3 to this support document.General Dynamics Longwood NPL Listing Support Document September 2010

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 Analytical data from ground water samples in this ar ea determined to be upgradient of the observed release sample are presented in A ttachment 3. Tables 3-1 through 3-4 of Attachment 3 of this support document present concentrations of 1,1-DCE in samples upgradient of the release sample. Concentrations of possible parent compounds of 1,1- DCE (PCE, TCE, and 1,1,1-TCA) are also listed for each location. These sample locations are plotted in Figures 3-1 through 3-3 of Attachment 3 of this support document; the highest detected concentration (if any) of 1,1-DCE is shown at each location. In addition, from these historical results presented in Attachment 3, Table 3 below presents the greatest historical detected concentration of 1,1-DCE or its possible parent compounds from any of the locations considered upgradient of observed release location DPGW-34.

Table 3 – Greatest Historical Upgradient Detectio n of Either PCE, TCE, 1,1-DCE, or 1,1,1-TCA in Ground Water Samples 1 Analyte Result (μg/L) Sample Location Investigation Reference

PCE 100 MW-2B Aug 88 Ref. 8, pp. A-20, A-21, Fig. 4-39 TCE 23,000 MW-5B Mar 91 Ref. 8, pp. A-26, A-27, Fig. 4-39 1,1,1-TCA 520 MW-5B Apr 98 Ref. 8, pp. A-26, A-27, Fig. 4-39 1,1-DCE 1,700 MW-5B Sep 89 Ref. 8, pp. A-26, A-27, Fig. 4-39 1 Direct-push or monitoring well ground water samples 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 The highest 1,1-DCE concentration found at any sam ple location upgradient of the release sample location was 1,700 μg/L; using this as a background le vel would still result in a more than 3-fold increase in 1,1-DCE levels in the observed release sample (w hich had a concentration of 26,500 μg/L 1,1-DCE). In addition, Brown and Caldwell asserted that the principle parent compound of 1,1-DCE is 1,1,1-TCA, and the highest 1,1,1-TCA concentration in any of these sample locations is 520 μg/L. Thus, if all of it degraded and moved to the release sample location, it would still not explain the concentration of 1,1- DCE levels in the release sample DPGW-34. Even the highest historical potentially upgradient TCE detection would not account for the levels of 1,1-DC E in the release sample, as Brown and Caldwell have argued that 1,1-DCE is a minor degradation produc t of TCE. The observed release of 1,1-DCE is therefore appropriately attributed to the General Dynamics Longwood site.

Specific comments regarding attribution of the release to the General Dynamics-Longwood site are addressed in the following subsections of this support document:

• 3.19.1 Consideration of Degradation Products

65General Dynamics Longwood NPL Listing Support Document September 2010

• 3.19.2 Ground Water Flow Direction 2038 2039 2040 2041 2042 2043 • 3.19.3 Contaminant Migration Direction

• 3.19.4 Conclusions from Previous Studies

• 3.19.5 Absence of Significant Soil Contamination

3.19.1 Consideration of Degradation Products

Comment : General Dynamics cited EPA’s contractor as “incorrectly identifying 1,1-DCE as a primary breakdown product of TCE as opposed to a pr imary breakdown product of 1,1,1-TCA”. 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 Brown and Caldwell stated that “[t]he Record uses incorrect HRS scoring factors [emphasis in original comment] because EPA’s contractor incorrectly iden tifies 1,1-dichloroethene (1,1-DCE) as a primary degradation byproduct of trichloroethylene (TCE).” Brown and Caldwell asserted that the 1,1-DCE at the site “is a breakdown product of 1,1,1-TCA, not TCE, that there is no evidence that 1,1,1-TCA was used at the Gould Property [General Dynamics property], but its use and release at the SEC site is confirmed, and concluded that “the presence of 1,1-DCE is attri butable to SEC, not the ‘General Dynamics Longwood’ site.”

Brown and Caldwell explained that: Biodegradation of TCE to 1,1-DCE is less prevalent, and ‘of the three possible DCE isomers, 1,1-DCE [is] the least significant intermediate . . .’ [quoting an exhibit attached to the Brown and Caldwell comment document] . . . However, 1,1-DCE is the dominant VOC in groundwater at Source No. 2 and th e fact is well documented that 1,1,1-TCA breaks down to 1,1-DCE and 1,1-DCA de pending on environmental conditions.

Brown and Caldwell identified that: the Record states that TCE was utilized on the Gould Property [General Dynamics property], but that both TCE and 1,1,1-TCA were used a nd released on the upgradient Sprague property. Further, although releases of both chemicals have been documented on the Sprague property, no such discoveries have occurred at the Gould Property [General Dynamics property].

Brown and Caldwell continued that: Where 1,1-DCE is the principle contaminant, the source material is 1,1,1-TCA. . . . The detections of 1,1-DCE at the Gould Property [General Dynamics property] clearly indicate that the parent source material was 1,1,1-TCA. According to the Record, only TCE (and not 1,1,1-TCA) is suspected of being used at the Gould Property [General Dynamics property] while release of 1,1,1-TC A was confirmed at the Sprague site many years ago. . . . Mischaracterizing the byproducts from TCE degradation is a

66General Dynamics Longwood NPL Listing Support Document September 2010

significant error by EPA’s contractor that distorts the entire HRS scoring procedure [emphasis in original comment]. 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 Brown and Caldwell conc luded that “[t]he record fails to demonstrate that a solvent release occurred at the ‘General Dynamics Longwood’ site [emphasis in original comment] – either at ‘Source No. 1’ or at ‘Source No. 2,’” and that: the distribution of contaminants detected at the Gould Property [General Dynamics property] . . . is the result of an historic, aged, degraded release of 1,1,1-trichloroethane (1,1,1-TCA) that occurred 20 years ago or more at the Sprague Electric Company (SEC or Sprague) site located upgradient of the G ould Property [General Dynamics property].

Brown and Caldwell also commented that “[t]o stat e that 1,1-DCE is anything other than a minor breakdown product of TCE is intenti onally misleading,” and “[i]n fact, if TCE were the parent product associated with the elevated concentrations of 1,1-DCE detected at the Gould Property [General Dynamics property], then cis-1,2-DCE would be presen t in significantly higher concentrations than 1,1- DCE.”

Response : The attribution of the significant increase of 1,1-DCE to the General Dynamics Longwood site is not dependent on it being a degrad ation product of any pa rticular substance, or even its presence being a result of degradation of another substance. The rel ease of 1,1-DCE can be attributed to the site for three reasons. First, 1,1-DCE is associated with the site based on its presence in Source No. 2 (see section 3.12, Identification of a Source and Origin of Source Contam ination, of this support document). Second, there is no evidence suggesting 1,1-DCE migrated to the release sample location from another site, including the SEC site (see section 3.19, Likelihood of Release – Attribution, of this support document). Third, even if the presence of 1,1-DCE were the result of degradation of another solvent—PCE, TCE or 1,1,1- TCA, there is no evidence of sufficient quantities of these possible parent substances in upgradient samples to have caused the signifi cant increase in 1,1-DCE found in th e release sample (see section 3.19, Likelihood of Release – Attribution, of this support document). 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 The degradation of chlorinated solvents was considered in the HRS evaluation to the extent practicable, as there are certainly degradation daughters, likely coming from specific parent solvents found at the General Dynamics and SEC sites. However, the assu mption that the theoretical degradation process will dictate in a dynamic environment what the daughter components will be and their ratios to each other at any location is not a valid assumption, especially given the site-specific conditions. For example, this site is subject to a high ground water flow rate, and th e rate of migration of each solvent daughter product varies, as pointed out by Brown and Caldwell in the second paragraph of page 1-7 of its comments

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(docket ID EPA-HQ-SFUND-2009-0067-0006). Even if a mixture of parent and daughter compounds are present in expected typical ratios at one location, because some individual constituents of this mixture migrate faster than others with ground water flow an d through soil, the ratio of the individual constituents at any given location will vary as the contaminants migrate further from their point of origin. 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 Also, the rate of degradation and th e products of degradation will vary depending on other factors, such as microbial activity in the subsurface. As discussed in Exhibit M of Brown and Caldwell’s comments (docket ID EPA-HQ-SFUND-2009-0067-0006.1), the rate of microbial influenced degradation can be dependent upon aerobic or anaerobic conditions. At this site, oxygen levels in the subsurface could be impacted by the presence of surface coverage by bui ldings or paved areas which block oxygen transfer and the availability of other nutrients needed for microbial growth.

Regarding the commenter’s assertion that only specific pa rent solvents (such as 1,1,1-TCA) were used at the SEC property and not at the General Dynamics prope rty, this has not been completely demonstrated. The HRS documentation record at proposal describ es chlorinated solvents such as TCE and PCE as commonly used in printed circuit board manufacturing cleaning processes to illustrate the general usage of solvents at the site (see section 3.17, Identifica tion of a Source and Origin of Source, of this support document). No specific solvent is singled out by the HRS documentation record at proposal as having exclusively been used at the General Dynamics Longw ood site. That TCE is the only confirmed solvent used at the General Dynamics facility does not preclude the past use of 1,1,1-TCA, PCE, 1,1-DCE or any other solvent. Also, testimony from former Gene ral Dynamics employees indicate that PCE and 1,1,1- TCA may have been used at the facility (see section 3.17, Associating Substances with Source No. 2, of this support document).

Thus, detections of hazardous s ubstance documented at the Genera l Dynamics Longwood site indicate that the 1,1-DCE found in the observed release was asso ciated with a release from the site, and even when considering the dynamics of solvent degradation, cannot be associated with an upgradient, degraded release of chlorinated solvents.

3.19.2 Ground Water Flow Direction

Comment : Brown and Caldwell asserted that because EPA did not accurately determine variations in ground water flow direction over time, EPA’s ra tionale for attributing the increased ground water contamination levels to releases from General Dynamics operations was flawed. 2142 2143 2144 2145

68General Dynamics Longwood NPL Listing Support Document September 2010

Brown and Caldwell commented that consultants for SEC historically showed that shallow ground water flows from the location of a release of TCE and 1,1,1-TCA, directly onto the General Dynamics Longwood site toward Source No. 2. Brown and Caldwell stated that: 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 It is apparent that EPA’s contractor has grossly oversimplified the regional hydrogeologic conditions and groundwater flow patterns [emphasis in original comment] during their development of the HR S score for the Gould Property [General Dynamics property]. This error has resulted in invalid conclusions being made about the potential impacts on groundwater quality from hi storic operations at the Gould Property [General Dynamics property].”

Brown and Caldwell continued: As one example, there is no discussion in the Record of groundwater gradients or rates of movement, or the impact of lithologic discontinuities on groundwater movement and contaminant migration in the area. [

Response : Ground water flow direction was adequately identified to establish an observed release attributable to the General Dynamics Longwood site ( see section 3.11, Description of Pathway, of this support document). 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 Ground water flow direction information is not sp ecifically required in the HRS; however, in the evaluation of Likelihood of Release and specifically, when establishing an observed release by chemical analysis to ground water, flow direction informati on is often used to establish a background contaminant level to show a significant increase in a hazardous substa nce and attribute a release to the site (see section 3.18, Likelihood of Release – Background, of this support document). This background contamination level is usually established by analyzing sa mples from upgradient of the site sources.

Analysis of historical ground water elevation data indicates that there has been a generally northward movement of ground water in the vicinity of Sour ce No. 2 – both in the A-zone and B-zone of the surficial aquifer, and variations due to the pump a nd treat system do not appear to have a significant impact on the overall flow direction between the ba ckground and release wells used to establish the observed release in the eastern part of the Gene ral Dynamics Longwood site. (See section 3.11, Description of Pathway, of this support document.)

An observed release by chemical analysis was doc umented according to the HRS (see sections 3.18, Likelihood of Release – Background, and 3.19, Likelihood of Release – Attribution, of this support document). The background samples used to establis h the significant increase in 1,1-DCE levels were from upgradient sample locations, ruling out the possib ility of contamination migration from the SEC site

69General Dynamics Longwood NPL Listing Support Document September 2010

to the release location, and thus the significant increas e in 1,1-DCE in the release sample did not come to be located on the General Dynamics Longwood site due to migration and the release is attributable to the site. Because the general ground wa ter flow patterns at the site were identified, and the subsurface geological conditions were properl y evaluated for HRS purposes, the evaluation of observed release background, and thus the likelihood of release fact or of the HRS score for this site was properly established. 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 This comment has no effect on the HRS site score or the decision to place this site on the NPL.

3.19.3 Contaminant Migration Direction

Comment : Brown and Caldwell commented that EPA had not considered the impact of a clay layer that slanted toward the General Dynamics property when it attributed an observed release to the site. It claimed that subsurface geologic features underlying the site, specifically a clay layer, at a depth of approximately 12 to 25 feet below land surface, slanting downward from the Sprague site to the General Dynamics site, is oriented in such a way that den se solvent contamination would migrate along this clay layer from under the Sprague site to under the General Dynamics site. 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 Brown and Caldwell stated: The geometry of this impermeable layer represents a transport mechanism for the northward migration of VOC-contaminat ed groundwater from the upslope Sprague Electric site to the downslope Gould Property [General Dynamics property] that was not considered by EPA’s contractor when scoring the Gould Property [General Dynamics property] [emphasis in original comme nt]. Upgradient releases of TCE, 1,1,1- TCA, and their breakdown products likely migrated down the slope of the A/B clay layer. This northward migration of contaminants from Sprague to Gould [General Dynamics Longwood site] was driven by groundwater recharge that transported contaminants to the base of the A Zone where they were funnel ed by the clay topography northward to Source No. 2.

Additionally, Brown and Caldwell alleged that the r esults for ground water samples collected “above the A/B clay unit in 2005 and 2007 indicate that the relatively high concentrations of 1,1-DCE in groundwater at Source No. 2 are coincident with a scenario in which they were originally released at the Sprague site and traveled to the Gould Property [General Dynamics property] along the steep slope of the A/B clay unit [emphasis in original comment].”

Brown and Caldwell asserted that:

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These VOCs (TCE and 1,1,1,-TCA and their breakdown products) appear to have beenconfined by the topography of the unit. This configuration suggests that northwardmigrating contaminants in groundwater en countered a zone of decreased groundwater flow at the break in slope where the A Zone abruptly increased in thickness from approximately 6 feet of saturated thickness to 22 feet. 2219 2220 2221 2222 2223 2224 Response : The clay layer under the SEC and the General Dynamics Longwood site was considered in attributing the observed release to the General Dynamics Longwood site. The subsurface was adequately identified and interpreted in the HRS evaluation (see sections 3.11, Description of Pathway, and 3.11.2, Surficial Aquifer Clay Layer, of this support document ). The clay layer was used to segment the surficial aquifer into the “A” zone and the “B” zone and to guide the selection of background and release samples in the two horizons. 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 Chlorinated solvents moving through the subsurf ace along the A/B clay layer may be a theoretical mechanism of transport of chlorinated solvents from the SEC property to the General Dynamics property. However, hydraulically upgradient of Source No. 2, sa mples have been taken at various depths of the surficial aquifer over various periods of time during past investigations and analyzed for 1,1-DCE and its possible parent substances. If the cause of the significant increase in 1,1-DCE levels were due to significant concentrations of these contaminants migrating along this A/B clay layer, historical sampling data from upgradient of Source No . 2 would have shown detections of these chlorinated solvents matching levels found underlying or downgradient of Source No. 2. Historical sampling data indicates that such detections at high enough levels to ha ve caused the significant increase in 1,1-DCE in the release sample in the eastern portion of the Genera l Dynamics Longwood site were not documented in the upgradient areas—including locations where samples were taken at or just above the clay layer in the surficial aquifer (see section 3.19, Likelihood of Rel ease – Attribution, and, and Attachment 3 of this support document). There is, therefore, no evidence th at a significant portion of the contaminants in the observed release sample associated with Source No. 2 migrated from the SEC site by migrating along the clay layer.

This comment has no effect on the HRS site score or the decision to place this site on the NPL.

3.19.4 Conclusions from Previous Studies

Comment : Brown and Caldwell asserted that previous studies have shown, and EPA and the State of Florida have acknowledged that the contamination unde r the Sprague property had migrated to under the General Dynamics property. 2251 2252 2253

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2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 Brown and Caldwell asserted that previous studies confirmed that the Sprague Electric site had contaminated the Gould Property [General Dynamics property], and stated that: . . . As EPA acknowledges, ‘The SEC property, located hydraulically upgradient of the [Gould] property, is a known source of contamination’ and ‘The AOC signed and approved by EPA in June 2004 also includes the [Gould] property’ [quoting the HRS documentation record, page 53] . . . Previous investigative studies have shown this and have also generated raw data confirming that VOC contaminants detected at the Gould Property [General Dynamics property] are the result of these historic releases that were discovered in groundwater at the SEC site and traced northward to both the Gould Property [General Dynamics property] [emphasis in original comment] and offsite to the northwest across U.S. Highway 17-92.

Brown and Caldwell also stated that contaminati on of the General Dynamics Longwood site by Sprague Electric has been acknowledged by Florida Regulators, and that: In an August 9, 2002 letter from FDEP to Mr. Tim Sleeth (GAFRI’s outside legal counsel) that is discussed in a 2003 CERCLA Reassessment Report, state regulators were noted to have reiterated their position that ‘ FDEP did not concur with the assertion that contamination in Zone B was migrating upgr adient from sources on the Gould property” [General Dynamics property] and that ‘ there was no evidence of contamination sources on the Gould property [General Dynamics property] or heavy irrigation or septic tank discharges . . .” [emphasis added by Brown and Caldwell].

Response : The statements made in the 2003 and 2004 reports and studies by EPA and by Florida were made prior to the most recent investigati ons, especially the investigation used to document an observed release of 1,1-DCE in the eastern portion of the site. The release of 1,1-DCE was based on sampling information collected in 20 05 (see analytical results for background and release samples in pp. 39-52 of the HRS documen tation record at proposal). This release has been correctly attributed to the General Dyna mics Longwood site (see s ection 3.19, Likelihood of Release – Attribution, of this support documen t). Conclusions from previous studies which identified the potential origin of hazardous s ubstances represent conclusions made at that particular time using available e nvironmental and analytical information; they do not disprove the establishment of the observed release. 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 Since these earlier conclusions or assumptions, further sampling and analysis has taken place— including the 2005 investigation used to estab lish the observed release in the HRS documentation record at proposal—which have advanced the unde rstanding of the site. EPA explained on page 2 of a letter to General Dynamics on August 27, 2008 (attached to the General Dynamics

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comment letter as Reference I) that remedial inv estigations, conducted after the 2004 AOC with GAFRI, indicated the presence of: 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 an additional source or sources of contam ination to the groundwater plume under investigation, as well as another, entirely di stinct groundwater plume. This new source area was located on the property owned by G ould Publications [previously the General Dynamics property] and was contributing a diffe rent contaminant from those found to be emanating from the Sprague Site.

Thus, although early findings suggested that th e contaminants under the General Dynamics Longwood site could have originated under th e SEC site, this previous understandi ng of interactions between the two sites was appropriately updated to reflect the availability of new and more complete investigative data (that used in the HRS documentation record to score the site), which documented an independent source (Source No. 2) and an observed release in the eastern portion of the General Dynamics Longwood site.

This comment has no effect on the HRS site score or the decision to place this site on the NPL.

3.19.5 Absence of Significant Soil Contamination

Comment : Brown and Caldwell asserted that there is a lack of soil contamination at the site indicative of a surface release of hazardous substances. It stated: 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 Although borings advanced into shallow groundwater beneath the former degreaser location showed elevated levels of 1,1-DCE, this contaminant is the result of historic releases of degreasing solvents that occurred upgr adient at the Sprague site. As early as 1992, Spragues’s own consultant documented that shallow groundwater in both the A Zone and B Zone flows directly from the confirmed source area from the TCE and 1,1,1- TCA release at the SEC site onto the Gould Property [General Dynamics property]. [

Brown and Caldwell continued that: Relatively high concentrations of VOCs have been documented in groundwater at depths of between 20 to 24 feet below ground surface (bgs) at Source No. 2. However, only concentrations of 1,1-DCE that are three orders of magnitude lower have been measured in shallower soil and groundwater at Source No. 2. The presence of th e relatively clean shallow zone is inconsistent with a surface release of solvents at Source No. 2 and means that the likely source of the 1,1- DCE is not from a hypothetical TCE release at the Gould Property [General Dynamics property] , but from the documented 1,1,1-TCA release at the SEC site [emphasis in original comment]. 2322 2323 2324 2325 2326 2327 Response : That high levels of contamination were detected in ground water at depths below the general area of Source No. 2 and low levels of contamina tion were found within Source No. 2 soils, does not necessarily indicate that ground water contamination did not migrate through the soil to the groundwater release location, or that it necessarily had to have migrated from a hydraulically upgradient location on 2328 2329 2330 2331

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SEC property. The chlorinated solvents just as lik ely moved downward through the soil and dissolved or moved as free product into the ground water, since their high density causes them to sink. 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 To establish an observed release, attribution to the site, not to a specific source, is required (see section 3.19, Likelihood of Release – Attribution, of this support document). Thus, Source No. 2 may not be (and need not be) the origin of the 1,1-DCE in the release well. It is just as acceptable that whatever caused the soil to become contaminated was also the origin of the contamination in the ground water. It is also possible that the contaminated soil may have pr eviously had a much higher concentration of 1,1,- DCE, but as part of the migration route of the 1, 1-DCE toward the ground water, with the passage of time, the contamination has migrated away. Alternatively, it could be that other undiscovered contaminated soil or other sources in the vicinity of Source 2 existed which contributed to releases to ground water.

In fact, the HRS documentation record at proposal in dicates there must be another source or “origin” of the 1,1 DCE or of its parent substance. The sour ce type for Source No. 2 is identified as contaminated soil, which, as stated in the HRS definition of so urce (see section 3.15, Source Type, of this support document), is correctly identified as an eligible source when the soil has come to be contaminated due to migration.

There are several possible original source locations of chlorinated solvents on the General Dynamics property which are adjacent to Source No. 2 including: the location of a former above ground storage tank identified as used for storage of solv ents, located directly to the east of the Source No. 2; the location of a former underground storage tank to the south and west of Source No. 2; and the location of a former vapor degreaser in Building 3 (see Figure 4 of Reference 10 of the HRS documentation record at proposal). (See sections 3.12.2, Evidence of Migration from Former Vapor Degreaser, and 3.12.3, Contamination from Upgradient Ground Water Releases, of this support document.) There is evidence suggesting the use of 1,1 -TCA (a parent substance for 1,1-DCE) by General Dynamics (see section 3.17, Associating Substances with Source No. 2, of this su pport document). These findings, and the lack of any evidence from 18 years of sampling of upgradient contam ination in high enough concentration to have caused the significant increase in 1,1-DCE concentrations are sufficient to attribute the 1,1-DCE release to the General Dynamics Longwood site (see sections 3.12, Identification of a Source and Origin of Source Contamination, and 3.18, Likelihood of Re lease – Background, and above in section 3.19, Likelihood of Release – Attribution, of this support document).

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This comment has no effect on the HRS site score or the decision to place this site on the NPL. 2366 2367 2368

2369 2370 2371 2372 2373 2374 2375 

### 3.20 Waste Characteristics General Dynamics and Brown and Caldwell challenge d the HRS documentation record evaluation of waste characteristics. Specific comments are addr essed in the following subsections of this support document:

• 3.20.1 Toxicity/Mobility

• 3.20.2 Waste Quantity

3.20.1 Toxicity/Mobility

Comment : General Dynamics and Brown and Caldwell indicated that because there is no release attributable to the General Dynamics Longwood site , there are no substances to assign toxicity/mobility values in the HRS documentation record. 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 General Dynamics asserted that the toxicity determinations were based upon the presence of a release of TCE “in the absence of evidence that such a release ever occurred.”

Additionally, Brown and Caldwell commented that th e toxicity/mobility factor value of 10,000 assigned presented within the HRS documentation record is “based upon the unsupported conclusion that there has been a release of TCE at the Gould Property [General Dynamics property]” and that “[i]n fact, a review of all the evidence suggests that the source of that TC E is historical releases on and issuing from the SEC site, along with the subsequent migration of the TCE downgradient in groundwater.”

Response: The toxicity and mobility factor values used in the HRS evaluation at proposal were assigned consistently with the HRS. Revising the HRS score at promulgation to reflect only Source No. 2 and an observed release in the eastern part of the site change s the combined toxicity/mobility factor value for the site but does not change the overall HRS site score. Furthermore, toxicity and mobility factor values are not assigned only to substances found in an observed rel ease, but also to substances associated with a source with a containment value greater than zero. Source 2 is such a source. 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 HRS Section 3.2, Waste Characteristics , states: Evaluate the waste characteristics factor cat egory for an aquifer based on two factors: toxicity/mobility and hazardous waste quantity. Evaluate only those hazardous

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substances available to migrate from the sour ces at the site to ground water. Such hazardous substances include: 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 • Hazardous substances that meet the criteria for an observed release to ground water.

• All hazardous substances associated with a source that has a ground water containment factor value greater than 0 ( see sections 2.2.2, 2.2.3, and 3.1.2.1). Thus, the HRS directs toxicity and mobility values to be assigned to substances either in an eligible source or in an observed release.

HRS Section 3.2.1, Toxicity/Mobility , states: For each hazardous substance, assign a toxicity factor value, a mobility factor value, and a combined toxicity/mobility factor value as specified in the following sections. Select the toxicity/mobility factor value for the a quifer being evaluated as specified in section 3.2.1.3.

HRS Section 3.2.1.1, Toxicity , states: Assign a toxicity factor value to each hazardous substance as specified in Section 2.4.1.1.

HRS Section 3.2.1.2, Mobility , states: Assign a mobility factor value to each hazardous substance for the aquifer being evaluated as follows:

• For any hazardous substance that meets th e criteria for an observed release by chemical analysis to one or more aquifers underlying the sources at the site, regardless of the aquifer being evaluated, assign a mobility factor value of 1.

HRS Section 3.2.1.3, Calculation of toxicity/mobility factor value , states: Assign each hazardous substance a toxicity/mobility factor value from Table 3-9, based on the values assigned to the hazardous substance for the toxicity and mobility factors. Use the hazardous substance with the high est toxicity/mobility factor value for the aquifer being evaluated to assign the value to th e toxicity/mobility factor for that aquifer. Enter this value in Table 3-1.

For containment considerations, HRS Section 3.1.2.1, Containment , states: Assign a containment factor value from Table 3-2 to each source at the site. Select the highest containment factor value assigned to those sources with a source hazardous waste quantity value of 0.5 or more (see section 2. 4.2.1.5). (Do not include this minimum size requirement in evaluating any other factor of this pathway.) Assign this highest value as the containment factor value for the aquifer be ing evaluated. Enter this value in Table 3-1.

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The HRS documentation record at proposal explaine d the assignment of toxicity and mobility factor values for the site. Based on substances associated with Sources No.1 and No. 2, and substances in observed releases in all parts of the site, the toxicity /mobility factor value was assigned based on TCE. However, only 1,1- DCE is associated with Sour ce No. 2 and in the observed release in the eastern portion of the site. Below is a discussion of the assign ment of the combined toxicity/mobility factor value based only on 1,1-DCE using information contained in the HRS documentation record at proposal. 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 Page 26 of the HRS documentation record at propos al documents the establishment of a containment factor value of greater than 0 for Source No. 2 as follows: The subsurface soil sample collected from Source No. 2 contained an elevated concentration of 1,1-DCE (Refs. 49, Figure 3; 77, pp. 15, 34) (also see Table 5 of this HRS documentation record). Source No. 2 c onsists of an area of contaminated soil located in the southeastern portion of Buildi ng 3 on the General Dynamics property (Ref. 16, pp. 14, 15, Exhibit 1). Analytical results for ground water collected in the vicinity of Source No. 2 indicate that a release of h azardous substances has occurred to the ground water migration pathway as documented in Section 3.0 of this HRS documentation record. During the 2005 RI, a liner was not observed during sampling activities (Ref. 56). Therefore, a containment factor va lue of 10 was assigned for the ground water migration pathway (Ref. 1, Section 3.1.2.1, Table 3-2).

Page 56 of the HRS documentation record at proposal lists 1,1-DCE as a hazardous substance detected in Source No. 2. It states that: The toxicity and mobility factor values fo r the hazardous substances detected in the source samples with containment factor values of greater than 0 are summarized in Table 15. The combined toxicity and mobility f actor values are assigned in accordance with Reference 1, Section 3.2.1. Hazardous substances detected in the observed release to ground water are assigned a mobility factor value of 1 (Ref. 1, Section 3.2.1.2).

In addition, an observed release to ground water of 1,1-DCE was established in the HRS documentation record at proposal (see sections 3.18, Likelihood of Release – Background, and 3.19, Likelihood of Release – Attribution, of this support document).

Thus, 1,1-DCE is an eligible hazardous substance fo r assigning toxicity and mobility both because it is a hazardous substance associated with Source No. 2, and because it is an observed release substance. Therefore, the toxicity/mobility factor value fo r 1,1-DCE was correctly evaluated in the HRS documentation record at proposal according to HRS criteria.

1,1-DCE has a toxicity factor value of 100 and a mob ility factor value of 1. Thus, according to Table 3-9 of the HRS, the toxicity/mobility factor value for the HRS evaluation of the General Dynamics

77General Dynamics Longwood NPL Listing Support Document September 2010

Longwood site is 100. Using this toxicity/mobility valu e in the HRS evaluation results in a change in the toxicity/mobility factor value from 10,000 to 100. (The 10,000 toxicity/mobility value assigned at proposal was based on TCE, a substance associated with Source No. 1.) However, this change does not result in a change in the HRS score for the site (see section 3.22, Revised Site Score, of this support document). 2481 2482 2483 2484 2485 2486 2487

2488 This comment has no effect on the HRS site score or the decision to place this site on the NPL.

3.20.2 Waste Quantity

Comment : General Dynamics and Brown and Caldwell ch allenged the hazardous waste quantity factor value assigned to the sources in the HRS documentation record at proposal. They asserted that the two sources are not due to releases from General Dynamics, but from the SEC site because they argued that there is no release attributable to the General Dyna mics Longwood site. Brown and Caldwell stated that: 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 there is no observed evidence of a solvent re lease to soil on the Gould Property [General Dynamics property] and, based on prior sa mpling conducted beneath both Sources, no such soil release is likely to have occurred. EPA’s contractor should therefore have used an HWQ Factor of 0 (zero).

Both of these commenters also challenged the waste quantity estimates assigned to the two sources. General Dynamics specifically asserted that the size and quantity of the “alleged release of hazardous substances” was improperly calculated.

Brown and Caldwell asserted that “EPA’s contractor incorrectly assessed the potential size of a potential groundwater release.” Brown and Caldwell claimed that “[c]ontrary to the statements on p. 57 of the [HRS Documentation] Record, there have been sufficient investigative data collected at both the Sprague and Gould Property [General Dynamics Longwood] sites over the past 21 years,” and that “[t]his would make it possible to evaluate a hazardous constituent quantity for the ‘General Dynamics Longwood’ site had a release actually occurred there.”

Response : The estimate of waste quantity for the two s ite sources and for the ground water pathway at proposal was developed consistently with the HRS requirements. The pathway hazardous waste quantity at proposal was correctly assigned as 10 at the time of proposal based on a sum of the waste quantities for Sources No.1 and No. 2 of greater than 0. As not ed earlier in this support document, and as explained below, Source 1 has been removed from the HRS scoring, however, the pathway waste quantity of 10 remains the same based on the waste quantity estimate for Source 2 alone. 2509 2510 2511 2512 2513 2514 2515

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HRS Section 2.4.2, Hazardous waste quantity , states: 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 Evaluate the hazardous waste quantity factor by first assigning each source (or area of observed contamination) a source hazardous waste quantity value as specified below. Sum these values to obtain th e hazardous waste quantity factor value for the pathway being evaluated.

HRS Section 2.4.2.1, Source hazardous waste quantity , states: For each of the three migration pathways, assign a source hazardous waste quantity value to each source (including the unallocated source) having a containment factor value greater than 0 for the pathway being evaluated . . . For all pathways, evaluate source hazardous waste quantity using the following four measures in the following hierarchy:

• Hazardous constituent quantity.

• Hazardous wastestream quantity.

• Volume.

• Area.

HRS Section 2.4.2.1.1, Hazardous constituent quantity , states, in part, “[e]valuate hazardous constituent quantity for the source (or area of observed contam ination) based solely on the mass of CERCLA hazardous substances (as defined in CERCLA section 101(14), as amended) allocated to the source (or area of observed contamination).” HRS Section 2.4.2.1.1 continues: Based on this mass, designated as C, assign a value for hazardous constituent quantity as follows:

• For the migration pathways, assign the source a value for hazardous constituent quantity using the Tier A equation of Table 2-5

•

. . . . If the hazardous constituent quantity for the source (or area of observed contamination) is adequately determined (that is, the total ma ss of all CERCLA hazardous substances in the source and releases from the source [or in the area of observed contamination] is known or is estimated with reasonable confidence), do not evaluate these other three measures discussed below . . . . If the hazardous constituent quantity is not ad equately determined, assign the source (or area of observed contamination) a value for hazardous constituent quantity based on the available data and proceed to section 2.4.2.1.2.

HRS Section 2.4.2.1.4, Area , directs the evaluator to: Evaluate the area measure using the area of the source (or area of the area of the observed contamination). Based on this area, designated as A, assign a value to the area measure as follows:

79General Dynamics Longwood NPL Listing Support Document September 2010

• For the migration pathways, assign the source a value for area using the appropriate Tier D equation of Table 2-5. . . . 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 The relevant portions of HRS Section 2.4.2.2, Calculation of hazardous waste quantity factor value , state: [s]um the source hazardous waste quantity values assigned to all sources (including the unallocated source) or areas of observed cont amination for the pathway being evaluated and round this sum to the nearest integer, ex cept: if the sum is greater than 0, but less than 1, round it to 1. Based on this value, select a hazardous waste quantity factor value for the pathway from Table 2-6. Table 2-6 does not assign a pathway factor value for a source waste quantity of greater than zero so the lowest “non-zero” category value of 1 to 100 was examined. This category have h as footnote “a” which directs the scorer to assign use a source waste quantity of 1ifthe estimate is greater than zero but less that 1. A waste quanity value of 1 corresponds to an assigned value of 1 according to the table. However this assigned value has footnote b, which states: For the pathway, if hazardous constituent quantity is not adequately determined, assign a value as specified in the text, do not assign the value of 1. The relevant portion of the text for this site states:

• If none of the targets for that pathway is subject to Level I or Level II concentrations, assign a factor value as follows:

- If there has been no removal action, assign either the value from Table 2-6 or a value of 10, whichever is greater, as the hazardous waste quantity factor value for that pathway.

Page 27 of the HRS documentation re cord at proposal presents how hazardous waste quantity at Source No. 2 was established using an estimate of the area of the source. It states: Only one sample was collected from Source No. 2 in the vicinity of the former vapor degreaser (Refs. 16, pp. 14, 15, Exhibit 1; 49, Figure 3). As a result, it is not known whether contamination in Source No. 2 is continuous throughout and the extent of contamination is not defined. The area of S ource No. 2 is undetermined, but greater than zero (Ref. 1, Section 2.4.2.1.4).

Additionally, page 57 of the HRS documentation at proposal states: The hazardous constituent quantity for Source Nos. 1 and 2 is not adequately determined. Their HWQ is undetermined, but greater than zero. As specified in Reference 1, Section 2.4.2.2, a HWQ factor value of 10 was assigned.

As only one sample was available to document Sour ce No. 2, information establishing “with reasonable confidence,” the total mass of CERCLA hazardous subs tances in the source, releases from the source, and the dimensions of the soil this source is not available. Thus, Tier A, Hazardous Constituent Quantity, was not evaluated for the site source. Source No. 2 h azardous waste quantity was evaluated for Tier D, Area,

80General Dynamics Longwood NPL Listing Support Document September 2010

and was determined to be greater than zero based on the finding on the presence of hazardous substances in the single sample. 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 This Source 2 waste quantity factor value corresponds to a pathway hazardous waste quantity factor value 10 in the HRS evaluation based on the instruction pr esented in HRS section 2.4.2.2 above. Because the hazardous waste quantity estimate is greater than zer o, the assigned value comes from the text of HRS section 2.4.2.2, not from the table, as cited above. Since there are no actually contaminated targets for this site, the pathway waste quantity is assigned a fact or value of 10, the same as assigned at proposal

Section 3.19, Likelihood of Release – Attribution, of this support document further addresses the issue of whether contamination at the General Dynamics Longw ood site is attributable to General Dynamics.

This comment has no effect on the HRS site score or the decision to place this site on the NPL. 

### 3.21 Targets

Comment : Brown and Caldwell and General Dynamics asserted that the HRS evaluation incorrectly included targets associated with upgradient drinki ng water wells in determining the site score. 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 General Dynamics specifically commented that EPA failed to “properly account for the population potentially affected by contamination migrating from the Gould [General Dynamics Longwood] site.” Also, Brown and Caldwell asserted that “ [t]he Record incorrectly calculates the target population in the vicinity of the Gould Property [General Dynamics property] [emphasis in original comment] that could potentially be exposed to contaminated grou ndwater because EPA’s contractor did not consider only downgradient drinking water sources.”

Further, Brown and Caldwell indicated that the population factor value is overstate d. Referencing Section 3.3.2.4 of the HRS, Brown and Caldwell stated that: the population to be included in the eval uation are those persons served by drinking water from points of withdrawal subject to potential contamination . . . Based on field data and known conditions at the Gould [General Dynamics Longwood] and Sprague sites, groundwater in the vicinity of these sites flows to the northwest, north, and northeast. Clearly only a portion of the 37 wells are subject to potential contamination (i.e. those wells located hydraulically downgradient of the Gould Property [General Dynamics property]). Therefore, the distance-weighted population and corresponding potential contamination factor calculat ed by EPA’s contractor is incorrect [emphasis in original comment].

81General Dynamics Longwood NPL Listing Support Document September 2010

Brown and Caldwell also asserted that a modified population factor value should be used in the HRS evaluation, and that: 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 [t]o be consistent with the NCP and to ensu re that only ‘those persons served by drinking water from points of withdrawal subject to potential contamination’ are considered, the potential contamination population factor va lue was recalculated by Brown and Caldwell based on targets located downgradient of the site within the 4-mile target radius.

Brown and Caldwell provided a modified list of wells used in their population factor value analysis, and specified that: [t]he following drinking water wells were included in the evaluation based on their locations as depicted in Reference 30 of the Record: 1. Four (4) Seminole County (Greenwood Lakes and Country Club WTPs) wells located >1 to 2 miles from the site 2. Three (3) Seminole County (Greenwood Lak es WTP) wells located >2 to 3 miles from the site 3. Two (2) Seminole County (Heathrow WTP) wells located >3 to 4 miles from the site 4. Five (5) City of Lake Mary wells lo cated >3 to 4 miles from the site; and 5. Six (6) City of Sanford wells located >3 to 4 miles from the site.

Brown and Caldwell presented a table showing thei r modification to the distance-weighted population values from their modified list of wells (this information is summarized in Table 4 below).

Table 4. Distance-Weighted Population Values as Presented by Brown and Caldwell

Distance Category (Miles) Population Distance-Weighted Population (Ref. 1, Table 3-12) Greater than 0 to 1/4 0 0 Greater than 1/4 to 1/2 0 0 Greater than 1/2 to 1 0 0 Greater than 1 to 2 10,339.44 8,163 Greater than 2 to 3 7,754.58 2,607 Greater than 3 to 4 33,067.04 26,068 Sum of Distance-Weighted Population Values 36,838 Sum of Distance-Weighted Population Values ÷ 10 3,683.8 2664 Response : Consistent with the HRS, the water supply wells identified as upgradient of the site by Brown and Caldwell were correctly considered as eligible targets at the time of propo sal. While the removal of Source No. 1 from the HRS evaluation results in a redrawing of the TDL for the site, it does not result in a change in the HRS site score. 2665 2666 2667 2668 2669

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The HRS directs a scorer to first identify the extent of the aquifer being evaluated and to establish the TDL for the site. HRS Section 3.0.1.1, Ground water target distance limit , states: 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 The target distance limit defines the maximu m distance from the sources at the site over which targets are evaluated. Use a target distance limit of 4 miles for the ground water migration pathway, except when aquifer disc ontinuities apply (see section 3.0.1.2.2). Furthermore, consider any well with an observed release from a source at the site (see section 3.1.1) to lie within the target distan ce limit of the site, regardless of the well’s distance from the sources at the site.

Next, the scorer identifies what drinking water wells can be considered targets for HRS purposes. HRS Section 3.3, Targets , instructs the scorer to: [e]valuate the targets factor category for an aquifer based on four factors: nearest well, population, resources, and Wellhead Protection Area. Evaluate these four factors based on targets within the target distance limit specified in section 3.0.1.1 and the aquifer boundaries specified in section 3.0.1.2. De termine the targets to be included in evaluating these factors for an aquifer as specified in section 3.0.

HRS Section 3.3.2, Population , states: [i]n evaluating the population factor, include those persons served by drinking water wells within the target distance limit specifie d in section 3.0.1.1. For the aquifer being evaluated, count those persons served by wells in that aquifer and those persons served by wells in overlying aquifers as specified in section 3.0. Include residents, students, and workers who regularly use the water. Exclude transient populations such as customers and travelers passing through the area. Evaluate the population based on the location of the water supply wells, not on the location of the residences, work places, etc. When a standby well is maintained on a regular basis so that water can be withdrawn, include it in evaluating the population factor.

Then the HRS directs the scorer to identify which wells are c onsidered actually contaminated (e.g., level I or level II). All people drinki ng water from water supply wells not considered actually contaminated and within the TDL are considered as eligible potential targets.

HRS Section 3.3.2.4, Potential contamination , states: Determine the number of people served by dr inking water from points of withdrawal subject to potential contamination. Do not include those people already counted under the Level I and Level II concentrations factors. Assign distance-weighted population values from Table 3-12 to this population as follows:

• Use the “Karst” portion of Table 3-12 to assign values only for that portion of the population served by points of withdrawal that draw drinking water from a karst aquifer that underlies any portion of the sources at the site.

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- For this portion of the population, de termine the number of people included within each “Karst” distance category in Table 3-12. 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 Pages 58-59 of the HRS documentation record at pro posal identify the municipal water systems in the TDL for the site, as follows: Residents in the vicinity of the General Dynamics property are provided drinking water from one of seven municipal systems: Seminole County, Casselberry, Lake Mary, Longwood, Winter Springs, Sanford, and Sanlando Utilities.

Page 59 of the HRS documentation record at pro posal assigned the target populations to each water system and the distance categories for each well, stating: Municipal wells located within a 4-mile radius of the General Dynamics property provide drinking water to about 116,336.52 people. The population served by these wells per distance ring is distributed as follows: > 0 to 0.25 mile, 0 people; > 0.25 to 0.50 mile, 8,995.76 people; > 0.50 to 1 mile, 0 people; > 1 to 2 miles, 18,428.64 people; > 2 to 3 miles, 41,061.92 people; > 3 to 4 miles, 47,850.20 people (Refs. 30; 31, pp. 1 through 8; 32, pp. 1, 2; 33, pp. 1 through 8; 34; 35, pp. 1 through 8; 36, pp. 1, 2, 3; 37, pp. i through 11) (also see Table 17 of this HRS documentation record). All of the wells in the area are screened in the Upper Floridan aquifer at a maximum depth of 925 feet (Refs. 31, pp. 1, 2, 9; 32, p. 1; 33, pp. 1, 2; 34; 35, p. 1; 36, p. 1; 37, p. 1; 94; 97). Seminole County, Sanlando Utilities, and the cities of Lake Ma ry, Sanford, and Casselberry have wellhead protection areas (Refs. 31, p. 2; 32, p. 1; 33, p. 1; 34, p. 1; 35, p. 1; 36). Therefore, wellhead protection areas are located within the 4-mile radius of sources at General Dynamics (Ref. 30).

Page 63 of the HRS documentation record at proposal described the Floridan aquifer system as karstic, and identified distance-weighted population values, according to Table 3-12 of the HRS, for potential contamination ground water targets in the Floridan aquifer. It states that: [d]istance-weighted population values for potential contamination ground water targets for the Upper and Lower Floridan aquifer ar e presented in Table 18. Ground water flow in the Floridan aquifer system is mostly through porous limestone, and is enhanced by networks of small fractures or solution op enings that occur along joints or bedding planes. In some areas, flow may be thr ough large cavernous features of paleokarst, resulting in a dual-porosity flow system (Ref . 68, pp. 19, 21, 23). Karstic ground water flow occurs in the Floridan aquifer within the entire 4-mile radius of the General Dynamics property (Ref. 78).

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TABLE 18: Distance-Weighted Population Values - Karst

Distance Category (Miles) Population Distance-Weighted Population Value (Ref. 1, Table 3- 12) References Greater than 0 to 1⁄4 0 0 30 Greater than 1⁄4 to 1⁄2 8995.76 3,233 30; 37, pp. i through 11 Greater than 1⁄2 to 1 0 0 30; 37, pp. i through 11 Greater than 1 to 2 18,428.64 8,163 30; 31, pp. 1 through 8; 33, pp. 1 through 10 Greater than 2 to 3 41,061.92 26,068 30; 31, pp. 1 through 8; 33, pp. 1 through 10; 36, pp. 1, 2; 37, pp. i through 11 Greater than 3 to 4 47,850.20 26,068 30; 31, pp. 1 through 8; 32, pp. 1, 2; 34, pp. 1, 2, 3; 35, pp. 1 through 8 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 Brown and Caldwell is incorrect in its assertion that th e target score should not include targets associated with wells considered to be upgradient of the sour ce. The HRS does not specifically take into account such level of detail as ground water flow gradients in order to determine target populations (55 FR 51551, December 14, 1990). In responding to public comments on the proposed (original) HRS on July 16, 1982 (47 FR 31190), EPA explained that it is generally not practicable to determine the population actually exposed or threatened by using ground water flow inform ation. In many instances, the information is not available. Even where there is extensive knowledge of subsurface conditions, interpretation is nearly always subject to dispute. Requiring a precise measure of the affected population would add inordinately to the time and expense of applying the HRS. EPA decided not to use ground water flow information because of the need to develop a nationally unifo rm system for scoring a large number of sites expeditiously with commonly-available data. EPA r econsidered this issue when revising the HRS, and determined that the decision not to directly consider ground water flow direction in evaluating targets was still appropriate (55 FR 51551).

Instead, the HRS considers flow direction indirectly in the method used to evaluate target populations by weighting target populations based on actual and potential contaminati on of drinking water wells. The HRS uses a radius of 4 miles around the site when de termining the distance to the nearest well in the contaminated aquifer and the population at risk due to actual or potential contamination, provided there is no discontinuity that completely transects the aquife r of concern between the site and the well being scored for HRS purposes (55 FR 51595).

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2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 In addition, if wells have not been contaminated by the site, as would be typical of upgradient wells, the wells are considered potentially rather than actually contaminated, and the population drawing from those wells is distance weighted (55 FR 51603). Conversel y, if wells have been contaminated, a likelihood for downgradient wells, the wells are considered actually contaminated and given higher weight in scoring.

However, even if the distance weighted popula tion values presented by Brown and Caldwell were considered in the evaluation, the site would s till maximize the pathway score when the likelihood of release and waste char acteristics factor values remain. That is, the likelihood of release factor value of 550, multiplied by the waste characteristics factor valu e of 18, multiplied by the targets factor value of 3708.8 (which incorporates the nearest well factor value of 20, the wellhead protection area factor value of 5, and the population factor value given by Brown and Caldwell in Table 4 above) would result in a value of 36,717,120, which when divided by 82,5 00, equals 445.05. This value exceeds the maximum pathway score of 100, and results in the same site score of 50.00.

As Source No. 1 was removed from consideration in the HRS evaluation of the General Dynamics Longwood site, the 4-mile TDL was redrawn at promulgation to show only those wells within a 4-mile radius of Source No. 2 (see revised Reference 30 of the HRS documentation record at promulgation). The redrawing of the TDL has resulted in one City of Winter Springs well (Well No. 6) being recategorized from the “greater than 1/4 to 1/2 mile” distance category (as originally presented in Reference 30 of the HRS documentation record at pro posal) to the “greater than 1/2 to 1 mile” distance category. This recategorization resulted in the reevaluation of populations served in each distance category, as presented in Table 5 below. According to Reference 37 of the HRS documentation record at proposal, the 8 wells that serve the City of Winter Springs all mix together to serve a population of 35,983; none of which contributes more than 40% to the distribution system. This results in an apportioned population of 4, 497.88 to each City of Winter Springs well. Table 5 below presents the distance-weighted population values as established at promulgation, upon revision of the TDL.

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Table 5: Distance-Weighted Population Values as Established at Promulgation 2800 Distance Category Population Distance-Weighted Population Value (HRS Table 3-12) Greater than 0 to 1/4 0 0 Greater than 1/4 to 1/2 4,497.88 ( reduced from 8995.76 ) 3,233 (unchanged)

Greater than 1/2 to 1 4,497.88 ( increased from 0 ) 2,607 (increased from 0)

Greater than 1 to 2 18,428.64 8,163 Greater than 2 to 3 41,061.92 26,068 Greater than 3 to 4 47,850.20 26,068 Sum of Distance-Weighted Population Values 66,139 Sum of Distance-Weighted Population Values / 10 [Potential Contamination Factor Value] 6,613.9

2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 Compared to the distance-weighted population values as presented in the HRS documentation record at proposal, the distance-weighted population value of the “greater than 1/4 to 1/2 mile” distance category does not change, because the number of users of the wells in this category remain in the same range of values as at proposal; however, the well being located within the “greater than 1/2 to 1 mile” distancecategory at promulgation adds a distance-weighted population value of 2,607 to the sum of distanceweighted population values proposed.

The potential contamination factor value of 6,613.9 at promulgation is greater than the potential contamination factor value of 6,353.2 established in the HRS documentation record at proposal. This results in a pre-capped pathway score of 264.55. Since the pathway is capped at a score of 100.00 according to HRS rule, the redrawing of the TDL h as no impact on the ground water migration pathway score of 100.00, or the HRS site score of 50.00 as pro posed. See section 3.22, Revised Site Score, of this support document for a full presentation of the rescoring of the site.

This comment has no effect on the site score, or on the decision to place the site on the NPL.



### 3.22 Revised Site Score

Comment : General Dynamics stated that the HRS documentation record “contains numerous technical errors and invalid assumptions which, when corr ected, result in an HRS ranking score of zero.” 2819 2820 2821

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Response : As documented below, the HRS score is 50. 00 for the General Dynamics Longwood site after consideration of all comments received on the proposed NPL listing of the site, considering only Source No. 2 and an observed release to ground wate r in the eastern part of the site. 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 Two changes have been made to the HRS assessment at proposal based on the removal of Source 1 from the HRS documentation record at proposal. First, only 1,1-DCE is evaluated associated with the observed release to ground water in the vicinity of Source No. 2. Second, the TDL was redrawn to show only those wells within a 4-mile radius of Source No. 2. (See section 3.10, Source No. 1 and Associated Observed Releases, of this support document.) The effects of these changes on the site score are detailed below.

The following scoresheets detail the s ite score at promulgation. The rationale for this score is presented in the following sections.

[HRS] Table 3-1 --Ground Water Migration Pathway Scoresheet Aquifer Evaluated: Interconnected Surficial and Upper Floridan Aquifers

Factor Categories and Factors Maximum Value Value Assigned Likelihood of Release to an Aquifer: 1. Observed Release 550 550 2. Potential to Release:

2a. Containment 10 NS 2b. Net Precipitation 10 NS 2c. Depth to Aquifer 5 NS 2d. Travel Time 35 NS 2e. Potential to Release [lines 2a(2b + 2c + 2d)] 500 NS 3. Likelihood of Release (hi gher of lines 1 and 2e) 550 550 Waste Characteristics: 4. Toxicity/Mobility (a) 100 5. Hazardous Waste Quantity (a) 10 6. Waste Characteristics 100 6 Targets: 7. Nearest Well 50 20 8. Population:

8a. Level I Concentrations (b) 0.00 8b. Level II Concentrations (b) 0.00 8c. Potential Contamination (b) 6,613.9

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Factor Categories and Factors Maximum Value Value Assigned 8d. Population (lines 8a + 8b + 8c) (b) 6,613.9 9. Resources 5 0 10. Wellhead Protection Area 20 5.00 11. Targets (lines 7 + 8d + 9 + 10) (b) 6,638.9 Ground Water Migration Score for an Aquifer: 12. Aquifer Score [(lines 3 x 6 x 11)/82,500] c 100 100.00 Ground Water Migration Pathway Score: 13. Pathway Score (S gw ), (highest value from line 12 for all aquifers valuated) c 100 100.00

2837 Notes : 2838 2839 2840 2841 2842 2843 2844 2845 NS = Not scored

a = Maximum value applies to waste characteristics category b = Maximum value not applicable

c = Do not round to nearest integer

WORKSHEET FOR COMPUTING HRS SITE SCORE

S pathway S 2 pathway Ground Water Migration Pathway Score (S gw ) 100 10,000 Surface Water Migration Pathway Score (S sw ) NS NS Soil Exposure Pathway Score (S s ) NS NS Air Migration Score (S a ) NS NS S 2 gw + S 2 sw + S 2 s + S 2 a 10,000 (S 2 gw + S 2 sw + S 2 s + S 2 a )/4 2,500

/(S 2 gw + S 2 sw + S 2 s + S 2 a )/4 50.00 2846 Note : 2847 2848 2849 NS = Not scored

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Ground Water Migration Pathway Score 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 As explained in HRS Section 3.0, Ground Water Migration Pathway , this pathway score is the product of the likelihood of release, waste characteristics, and ta rgets category values divided by a scaling factor of 82,500.

Likelihood of Release As discussed in section 3.18, Likelihood of Release – Background, of this suppor t document, an observed release by chemical analysis was documented in the ground water underlying/downgradient of Source No. 2.

HRS Section 2.3, Likelihood of release , states: [t]he minimum standard to establish an ob served release by chemical analysis is analytical evidence of a hazardous substa nce in the media significantly above the background level.

This HRS section also refers to HRS Table 2-3 which identifies the observed release criteria for chemical analysis. This table requires that when the sample measurement (i.e., the chemical concentration of a hazardous substance in a candidate release sample) is greater than or equal to the sample quantitation limit, an observed release can be established: [i]f the background concentration is not detect ed (or is less than the detection limit), an observed release is established when the sample measurement equals or exceeds the sample quantitation limit . . . If the background concentration equals or ex ceeds the detection limit, an observed release is established when the sampl e measurement is 3 times or more above the background concentration.

HRS Section 3.1, Likelihood of release , states: [f]or an aquifer, evaluate the likelihood of release factor category in terms of an observed release factor or a potential to release factor.

HRS Section 3.1.1, Observed release , states: [e]stablish an observed release to an aquifer by demonstrating that the site has release a hazardous substance to the aquifer. Base this demonstration on either:

• Direct observation . . .

• Chemical analysis – an analysis of ground water samples from the aquifer indicates that the concentration of hazardous substa nces(s) has increased significantly above the background concentration for the site (see section 2.3). Some portion of the significant increase must be attributable to the site to establish the observed release,

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except: when the source itself consists of a ground water plume with no identified source, no separate attribution is required. 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 As presented in sections 3.18, Like lihood of Release – Background, and 3.19, Likelihood of Release – Attribution, of this support document, an observed release by chemical analysis was documented, as a significant increase of 1,1-DCE was documented in gr ound water in sample DPGW-34(22’) at levels significantly above (more than 3-fold) background sa mples. This significant increase of 1,1-DCE was attributed to the site because it was associated with a site source and was found not to be associated with other sources. Thus, a Likelihood of release fact or category value of 550 was assigned to the ground water migration pathway by evaluating only Source No. 2 and the observed release associated with the eastern portion of the General Dynamics property; th is factor category value is unchanged from that assigned in the HRS documentation record at proposal.

Waste Characteristics HRS Section 3.2, Waste Characteristics , states: [e]valuate the waste characteristics factor category for an aquifer based on two factors: toxicity/mobility and hazardous waste quantity. Evaluate only those hazardous substances available to migrate from the sour ces at the site to ground water. Such hazardous substances include:

• Hazardous substances that meet the criteria for an observed release to ground water.

• All hazardous substances associated with a source that has a ground water containment factor value greater than 0 ( see sections 2.2.2, 2.2.3, and 3.1.2.1).

Toxicity/Mobility 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 HRS Section 3.2.1, Toxicity/Mobility , states: [f]or each hazardous substance, assign a toxicity factor value, a mobility factor value, and a combined toxicity/mobility factor value as specified in the following sections. Select the toxicity/mobility factor value for the a quifer being evaluated as specified in section 3.2.1.3.

HRS Section 3.2.1.1, Toxicity , states: [a]ssign a toxicity factor value to each hazardous substance as specified in Section 2.4.1.1.

HRS Section 3.2.1.2, Mobility , states: [a]ssign a mobility factor value to each hazardous substance for the aquifer being evaluated as follows:

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• For any hazardous substance that meets th e criteria for an observed release by chemical analysis to one or more aquifers underlying the sources at the site, regardless of the aquifer being evaluated, assign a mobility factor value of 1.. . . 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 HRS Section 3.2.1.3, Calculation of toxicity/mobility factor value , states: Assign each hazardous substance a toxicity/mobility factor value from Table 3-9, based on the values assigned to the hazardous substance for the toxicity and mobility factors. Use the hazardous substance with the high est toxicity/mobility factor value for the aquifer being evaluated to assign the value to th e toxicity/mobility factor for that aquifer. Enter this value in Table 3-1.

Page 56 of the HRS documentation record at proposal lists 1,1-DCE as a hazardous substance detected in Source No. 2. It states that: The toxicity and mobility factor values fo r the hazardous substances detected in the source samples with containment factor values of greater than 0 are summarized in Table 15. The combined toxicity and mobility f actor values are assigned in accordance with Reference 1, Section 3.2.1. Hazardous substances detected in the observed release to ground water are assigned a mobility factor value of 1 (Ref. 1, Section 3.2.1.2).

As described above, a hazardous substance (1,1-DCE) was associated with Source No. 2, which has a containment factor value of greater than 0, and the toxicity/mobility factor of 1,1-DCE was correctly evaluated as described in section 3.20.1, Toxi city/Mobility, of this support document.

Hazardous Waste Quantity 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 Source No. 2 was established according to HRS crite ria. HRS Section 1.1, Definitions, the HRS defines source as: Any area where a hazardous substance has been deposited, stored, disposed, or placed, plus those soils that have become contamin ated from migration of a hazardous substance.

HRS Section 2.2.1, Identify sources , outlines the requirements to be fo llowed when identifying sources at a site. It states: For the three migration pathways, identify th e sources at the site that contain hazardous substances. Identify the migration pathway(s) to which each source applies.

HRS Section 2.2.2, Identify hazardous substances associated with a source , states: For each of the three migration pathways, consider those hazardous substances documented in a source (for example, by sampling, labels, manifests, oral or written statements) to be associated with that source when evaluating each pathway.

HRS Section 2.2.3, Identify hazardous substan ces available to a pathway , directs the scorer:

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In evaluating each migration pathway, co nsider the following hazardous substances available to migrate from the sources at the site to the pathway: 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 • Ground water migration.

- Hazardous substances that meet the criteria for an observed release (see section 2.3) to ground water.

- All hazardous substances associated with a source with a ground water containment factor value greater than 0 (see section 3.1.2.1).

HRS Section 3.1.2.1, Containment , specifies that for containment considerations, the scorer is to: Assign a containment factor value from Table 3-2 to each source at the site. Select the highest containment factor value assigned to those sources with a source hazardous waste quantity value of 0.5 or more (see section 2.4. 2.1.5). (Do not include this minimum size requirement in evaluating any other factor of this pathway.) Assign this highest value as the containment factor value for the aquifer be ing evaluated. Enter this value in Table 3- 1.

The HRS documentation record at proposal appropr iately associated a hazardous substance (1,1-DCE) with Source No. 2 (see section 3.12, Identification of a Source and Origin of Contamination, of this support document). Comparing the contaminant levels to background levels demonstrated that the soil came to be contaminated due to migration. Additio nally, a ground water containment factor value of 10 was documented as associated with the source. Thus , Source No. 2 was established as a contaminated soil source according to HRS criteria.

HRS Section 2.4.2, Hazardous waste quantity , states: Evaluate the hazardous waste quantity factor by first assigning each source (or area of observed contamination) a source hazardous waste quantity value as specified below. Sum these values to obtain th e hazardous waste quantity factor value for the pathway being evaluated.

HRS Section 2.4.2.1, Source hazardous waste quantity , states:

[f]or each of the three migration pathways, assign a source hazardous waste quantity value to each source (including the unallocated source) having a containment factor value greater than 0 for the pathway being evaluated . . . For all pathways, evaluate source hazardous waste quantity using the following four measures in the following hierarchy:

• Hazardous constituent quantity.

• Hazardous wastestream quantity.

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• Volume. 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 • Area.

HRS Section 2.4.2.1.4, Area , states: Evaluate the area measure using the area of the source (or area of the area of the observed contamination). Based on this area, designated as A, assign a value to the area measure as follows:

• For the migration pathways, assign the source a value for area using the appropriate Tier D equation of Table 2-5.

•

. . . The relevant portions of HRS Section 2.4.2.2, Calculation of hazardous waste quantity factor value , state: [s]um the source hazardous waste quantity values assigned to all sources (including the unallocated source) or areas of observed cont amination for the pathway being evaluated and round this sum to the nearest integer, ex cept: if the sum is greater than 0, but less than 1, round it to 1. Based on this value, select a hazardous waste quantity factor value for the pathway from Table 2-6.

. . .

• If none of the targets for that migration pa thway is subject to Level I or Level II concentrations, assign a factor value as follows:

- If there has been no removal action, assign either the value from Table 2-6 or a value of 10, whichever is greater, as the hazardous waste quantity factor value for that pathway.

Page 27 of the HRS documentation re cord at proposal discusses how hazardous waste quantity at Source No. 2 was established. It states: Only one sample was collected from Source No. 2 in the vicinity of the former vapor degreaser (Refs. 16, pp. 14, 15, Exhibit 1; 49, Figure 3). As a result, it is not known whether contamination in Source No. 2 is continuous throughout and the extent of contamination is not defined. The area of S ource No. 2 is undetermined, but greater than zero (Ref. 1, Section 2.4.2.1.4)

Additionally, page 57 of the HRS documentation at proposal states: The hazardous constituent quantity for Source Nos. 1 and 2 is not adequately determined. Their HWQ is undetermined, but greater than zero. As specified in Reference 1, Section 2.4.2.2, a HWQ factor value of 10 was assigned.

Source No. 2 was determined to have a hazardous wast e quantity of greater than zero, which corresponds to a hazardous waste quantity factor value of 10 in the HRS evaluation. The removal of Source No. 1 from the HRS evaluation does not change the hazardous waste quantity factor value assigned to the site,

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because the source hazardous waste quantity value from Source No. 2 is sufficient to assign a hazardous waste quantity factor value of 10 for the site, as cited above. 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 The toxicity/mobility value of 100 multiplied by the hazar dous waste quantity factor value of 10 results in a waste characteristics product of 1,000; which corre sponds to a waste characteristics category factor value of 6 according to HRS Table 2-7. Although the waste characteristics category factor value of 6 is less than value of 18 within the HRS documentation r ecord at proposal, the waste characteristics scoring change does not change the site score of 50.00 as proposed.

Targets The targets factor value was correctly established in the HRS evaluation according to HRS criteria (see section 3.21, Targets, of this support document).

HRS Section 3.3, Targets , states: Evaluate the targets factor category for an aquifer based on four factors: nearest well, population, resources, and Wellhead Protection Area. Evaluate these four factors based on targets within the target distance limit specified in section 3.0.1.1 and the aquifer boundaries specified in section 3.0.1.2. De termine the targets to be included in evaluating these factors for an aquifer as specified in section 3.0.

Nearest Well 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 HRS Section 3.3.1, Nearest well , states: In evaluating the nearest well factor, include both the drinking water wells drawing from the aquifer being evaluated and those drawi ng from overlying aquifers as specified in section 3.0. Include standby wells in evaluating this factor only if they are used for drinking water supply at least once per year.

. . . . Assign a value for the nearest well factor as follows:

•

. . . . • If none of the drinking water wells is subject to Level I or Level II concentrations, assign a value as follows:

- If one of the target aquifers is a karst aquifer that underlies any portion of the sources at the site and any well draws drinking water from this karst aquifer within the target distance limit, assign a value of 20.

Population 3097 3098 HRS Section 3.3.2, Population , states:

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In evaluating the population factor, include those persons served by drinking water wells within the target distance limit specified in section 3.0.1.1. For the aquifer being evaluated, count those persons served by wells in that aquifer and those persons served by wells in overlying aquifers as specified in section 3.0. Include residents, students, and workers who regularly use the water. Exclude transient populations such as customers and travelers passing through the area. Evaluate the population based on the location of the water supply wells, not on the location of the residences, work places, etc. When a standby well is maintained on a regular basis so that water can be withdrawn, include it in evaluating the population factor. 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 Resources 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 HRS Section 3.3.3, Resources , states: To evaluate the resources factor, select the hi ghest value specified below that applies for the aquifer being evaluated. Assign this value as the resources factor value for the aquifer. Enter this value in Table 3-1. Assign a resources value of 5 if water drawn from any target well for the aquifer being evaluated or overlying aquifers (as specified in section 3.0) is used for one or more of the following purposes:

• Irrigation . . . .

• Watering of commercial livestock.

• Ingredient in commercial food preparation.

• Supply for commercial aquaculture.

• Supply for a major or designated water recreation area . . .

Assign a resources value of 5 if no drinking water wells are within the target distance limit, but the water in the aquifer being evaluated or any overlying aquifers (as specified in section 3.0) is usable for drinking water purposes. Assign a resources value of 0 if none of the above applies.

Wellhead Protection Area 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 HRS Section 3.3.4, Wellhead Protection Area , states: Evaluate the Wellhead Protection Area factor based on Wellhead Protection Areas designated according to section 1428 of the Safe Drinking Water Act, as amended. Consider only those Wellhead Protection Areas a pplicable to the aquifer being evaluated or overlying aquifers (as specified in section 3.0). Select the highest value below that applies. Assign it as the value for the Wellh ead Protection Area factor for the aquifer being evaluated. Enter this value in Table 3-1.

. . . . If neither criterion applies, assign a value of 5, if , within the target distance limit, there is a designated Wellhead Protection Area applicab le to the aquifer being evaluated or overlying aquifers.

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Regarding the municipal water systems within th e 4-mile TDL, Page 58 of the HRS documentation record at proposal states that: 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 Residents in the vicinity of the General Dynamics property are provided drinking water from one of seven municipal systems: Seminole County, Casselberry, Lake Mary, Longwood, Winter Springs, Sanford, and Sanlando Utilities (Ref. 30).

Page 59 of the HRS documentation record at proposal states that: Municipal wells located within a 4-mile radius of the General Dynamics property provide drinking water to about 116,336.52 people. The population served by these wells per distance ring is distributed as follows: > 0 to 0.25 mile, 0 people; > 0.25 to 0.50 mile, 8,995.76 people; > 0.50 to 1 mile, 0 people; > 1 to 2 miles, 18,428.64 people; > 2 to 3 miles, 41,061.92 people; > 3 to 4 miles, 47,850.20 people (Refs. 30; 31, pp. 1 through 8; 32, pp. 1, 2; 33, pp. 1 through 8; 34; 35, pp. 1 through 8; 36, pp. 1, 2, 3; 37, pp. i through 11) (also see Table 17 of this HRS documentation record). All of the wells in the area are screened in the Upper Floridan aquifer at a maximum depth of 925 feet (Refs. 31, pp. 1, 2, 9; 32, p. 1; 33, pp. 1, 2; 34; 35, p. 1; 36, p. 1; 37, p. 1; 94; 97). Seminole County, Sanlando Utilities, and the cities of Lake Ma ry, Sanford, and Casselberry have wellhead protection areas (Refs. 31, p. 2; 32, p. 1; 33, p. 1; 34, p. 1; 35, p. 1; 36). Therefore, wellhead protection areas are located within the 4-mile radius of sources at General Dynamics (Ref. 30).

Page 63 of the HRS documentation record describes the Floridan aquifer system as karstic, and identifies distance-weighted population values for potential contamination ground water targets in the Floridan aquifer. It states that: Distance-weighted population values for potential contamination ground water targets for the Upper and Lower Floridan aquifer are presented in Table 18. Ground water flow in the Floridan aquifer system is mostly th rough porous limestone, and is enhanced by networks of small fractures or solution op enings that occur along joints or bedding planes. In some areas, flow may be thr ough large cavernous features of paleokarst, resulting in a dual-porosity flow system (Ref . 68, pp. 19, 21, 23). Karstic ground water flow occurs in the Floridan aquifer within the entire 4-mile radius of the General Dynamics property (Ref. 78).

The sum of the distance-weighted population value of 63,532 as presented on page 63 of the HRS documentation record at proposal has increased to 66,139 as a result of redrawing the TDL to only account for those wells within a 4-mile radius of S ource No. 2 (see section 3.21, Targets, of this support document). As directed by the formula in HRS Section 3.3.2.4, Population , the new distance-weighted population established by HRS Table 3-12 (66,139), is divided by 10, resulting in a potential contamination factor value of 6,613.9.

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A value of 20 was established for the nearest well factor value as explained on page 62 of the HRS documentation record at proposal, which states that “[t]he nearest well value is also based on karst ground water flow documented in Section 3.0.1 of this HRS documentation record.” 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 For resources, a value of 0 was assigned as explaine d on page 63 of the HRS documentation record at proposal, which states, “[w]ells used for resources we re not identified within a 4-mile radius of the General Dynamics property.”

For Wellhead Protection Areas, a factor value of 5.00 was assigned, as explained on page 63 of the HRS documentation record at proposal which states that: Seminole County, Sanlando Utilities, and th e cities of Lake Mary, Sanford, and Casselberry have wellhead protection areas (Refs. 31, p. 2.; 32, p. 1; 33, p. 1; 34, p. 1; 35, p. 1; 36, pp. 1, 2). Therefore wellhead pr otection areas are located within the 4-mile radius of sources at General Dynamics (Ref. 30).

The targets factor category was established as directed by HRS Section 3.3.5, Calculation of targets factor category value: the factor values for nearest well, popu lation, resources, and Wellhead Protection Area are summed. Therefore, by evaluating only targets related to Source No. 2 and the observed release associated with the eastern portion of the General Dyna mics property: the factor value for nearest well (20) added to the factor value for population (6,613.9 ) added to the factor value for resources (0) added to the factor value for Wellhead Protection Area (5.00) resu lts in a targets factor category value of 6,638.9; this is slightly elevated from the targets factor category value assigned in the HRS documentation record at proposal.

Ground Water Migration Score for an Aquifer As directed by HRS Section 3.4, Ground water migration score for an aquifer , the factor category values for likelihood of release, waste characteristics, and targets are multiplied together and rounded to the nearest integer (550 x 6 x 6,638.9 = 21,908,370). This value is then divided by 82,500 (21,908,370 / 82,500 = 265.55). The resulting value is subject to a maximum value of 100; thus, the ground water migration pathway score for the aquifer is 100.00.

Calculation of HRS Site Score As directed by HRS Section 2.1.1, Calculation of HRS site score , the root-mean-square formula is applied to the relevant pathway scores (the ground water migration pathway score in this case). The square root

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99 3220 3221 3222 3223

3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 is taken of the value of the squared grou nd water migration pathway divided by 4 ( √ 100 2 / 4 = 50.00). Therefore, the HRS site score at promulgation is 50.00.



## 4. Conclusion The original HRS score for this site was 50.00. Based on the above response to comments and the modifications detailed in section 3.22, Revised Site Score, of this support document, the score remains unchanged. The final scores for the General Dynamics Longwood site are:

Ground Water 100.00 Surface Water Not Scored Soil Exposure Not Scored Air Not Scored HRS Site Score 50.00