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 Remedy Decisions Branch 

Office of Superfund Remediation and Technology Innovation 

Office of Solid Waste and Emergency Response 

U.S. Environmental Protection Agency 

Washington, DC 20460
Table of Contents

Executive Summary ...................................................................................................................................iv

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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

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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 

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General 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 releases of hazardous substances, pollutants, or 

contaminants throughout the United States. An original National Priorities List (NPL) was promulgated 

on September 8, 1983 (48 FR 40658). CERCLA requires 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 added 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. 

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General 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 listing 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 Environmental 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 Pollution 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 guidelines and procedures needed to respond under 

CERCLA to releases and threatened releases of hazardous substances, pollutants, or contaminants. On 

March 8, 1990 (55 FR 8666), EPA further revised the NCP in response to SARA. 

Section 105(a)(8)(A) of CERCLA, as amended by SARA, requires that the NCP include 

criteria for determining priorities among releases or threatened releases throughout the 

United States for the purpose of taking remedial action and, to the extent practicable, take 

into account the potential urgency of such action, for the purpose of taking removal 

action. 

Removal action involves cleanup or other actions that are taken in response to emergency conditions or 

on a short-term or temporary basis (CERCLA Section 101). 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 the known releases or threatened releases of hazardous 

substances, pollutants, or contaminants throughout the United States. The list, which is Appendix B of 

the NCP, is the NPL. 

An original NPL of 406 sites was promulgated on September 8, 1983 (48 FR 40658). At that time, an 

HRS score of 28.5 was established as the cutoff for listing because it yielded an initial NPL of at least 400 

sites, as suggested by CERCLA. The NPL has been expanded several times since then, most recently on 

March 4, 2010 (75 FR 9790). The Agency also has published a number of proposed rulemakings to add 

sites to the NPL. The most recent proposal was on March 4, 2010 (75 FR 9843). 

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General Dynamics Longwood NPL Listing Support Document September 2010 

Development of the NPL 

The primary purpose of the NPL is stated in the legislative history of CERCLA (Report of the Committee 

on Environment and Public Works, Senate Report No. 96-848, 96th Cong., 2d Sess. 60 [1980]). 

The priority list serves primarily informational purposes, identifying for the States and 

the public those facilities and sites or other releases which appear to warrant remedial 

actions. Inclusion of a facility or site on the list does not in itself reflect a judgment of the 

activities of its owner or operator, it does not require those persons to undertake any 

action, nor does it assign liability to any person. Subsequent government actions will be 

necessary in order to do so, and these actions will be attended by all appropriate 

procedural safeguards. 

The NPL, therefore, is primarily an informational and management tool. The identification of a site for 

the NPL is intended primarily to guide EPA in determining which sites warrant further investigation to 

assess the nature and extent of the human health and environmental risks associated with the site and to 

determine what CERCLA-financed remedial action(s), if any, may be appropriate. The NPL also serves 

to notify the public of sites EPA believes warrant further investigation. Finally, listing a site may, to the 

extent potentially responsible parties are identifiable at the time of listing, serve as notice to such parties 

that the Agency may initiate CERCLA-financed remedial action. 

CERCLA Section 105(a)(8)(B) directs EPA to list priority sites among the known releases or threatened 

release of hazardous substances, pollutants, or contaminants, and Section 105(a)(8)(A) directs EPA to 

consider certain enumerated and other appropriate factors in doing so. Thus, as a matter of policy, EPA 

has the discretion not to use CERCLA to respond to certain types of releases. Where other authorities 

exist, placing sites on the NPL for possible remedial action under CERCLA may not be appropriate. 

Therefore, EPA has chosen not to place certain types of sites on the NPL even though CERCLA does not 

exclude such action. If, however, the Agency later determines that sites not listed as a matter of policy 

are not being properly responded to, the Agency may consider placing them on the NPL. 

Hazard Ranking System 

The HRS is the principle mechanism EPA uses to place uncontrolled waste sites on the NPL. It is a 

numerically based screening system that uses information from initial, limited investigations -- the 

preliminary assessment and site inspection -- to assess the relative potential of sites to pose a threat to 

human health or the environment. HRS scores, however, do not determine the sequence in which EPA 

funds remedial response actions, because the information collected to develop HRS scores is not 

sufficient in itself to determine either the extent of contamination or the appropriate response for a 

particular site. Moreover, the sites with the highest scores do not necessarily come to the Agency's 

attention first, so that addressing sites strictly on the basis of ranking would in some cases require 

stopping work at sites where it was already underway. Thus, EPA relies on further, more detailed studies 

in the remedial investigation/feasibility study that typically follows listing. 

The HRS uses a structured value analysis approach to scoring sites. This approach assigns numerical 

values to factors that relate to or indicate risk, based on conditions at the site. The factors are grouped 

into three categories. Each category has a maximum value. The categories are: 

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

environment; 

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General 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 (Sgw) 

- drinking water 

• Surface Water Migration (Ssw) 

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 (Ss) 

- resident population 

- nearby population 

- sensitive environments 

• Air Migration (Sa) 

- population 

- sensitive environments 

After scores are calculated for one or more pathways according to prescribed guidelines, they are 

combined using the following root-mean-square equation to determine the overall site score (S), which 

ranges from 0 to 100: 

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S + S + S + S = S

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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 which 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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General Dynamics Longwood NPL Listing Support Document September 2010 

• 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 site-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 

μg/kg Microgram per kilogram 

μg/L Microgram per liter 

NCP National Oil and Hazardous Substances Pollution Contingency Plan, 40 C.F.R. 

Part 300 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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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 compounds 
General Dynamics Longwood NPL Listing Support Document September 2010 

1 1. List of Commenters and Correspondence 

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EPA-HQ-SFUND-2009-0067-0004 Correspondence, 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 contamination 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.

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General Dynamics Longwood NPL Listing Support Document 

Figure 1: General Site Area 

Note: The General Dynamics facility area and the SEC facility area are shown here as bounded by property boundaries. 

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27 Geology/Hydrology 

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Ground water in the Seminole County, Florida area exists in two distinct units: the surficial aquifer and 

the deeper Floridan aquifer. These aquifers are separated 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 immediately to the south divide the surficial aquifer into 

two water bearing zones, A-zone and B-zone. The A-zone (upper surficial aquifer) and B-zone (lower 

surficial aquifer), are separated by a discontinuous clay layer (A/B clay). The A/B clay layer ranges in 

depth from 13.5 feet below land surface (bls) to 32 feet bls across the General Dynamics property and is 

believed to be absent in the northwestern portion of the property. The ground water flow direction in the 

A and B-zones is north to northeast across the General Dynamics property. Figure 2 below characterizes 

the general subsurface structures below the General Dynamics Longwood site.

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General Dynamics Longwood NPL Listing Support Document 

Figure 2: General Subsurface Structures at the General Dynamics Longwood Site 

SURFICIAL 

AQUIFER 

HAWTHORNE 

GROUP 

(DISCONTINUOUS)

FLORIDAN 

AQUIFER

DISCONTINUOUS CLAY LAYER SEPARATING SURFICIAL AQUIFER INTO UPPER SURFICIAL (A-ZONE) AND LOWER SURFICIAL (B-ZONE) 

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Note: Subsurface layers shown represent the general stratigraphic layers below the General Dynamics Longwood 

layers are documented as discontinuous below the site, such as the Hawthorne Group and the surficial aquifer clay 

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General Dynamics Longwood NPL Listing Support Document September 2010 

67 Site History 

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Tenants at the General Dynamics property included Dynatronics (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 Dynamics 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 property 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. Structures 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, trichloroethylene1

 (TCE) was stored in an above ground storage tank located outside 

Building 3 near the vapor degreaser. Additional vapor degreasers were located throughout the facility; 

however, the location of these degreasers as well as the 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 containers of TCE. Painting and plating 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 generally used in the industry for the cleaning process 

include chlorinated solvents such as TCE, 1,1,1-trichloroethane (1,1,1-TCA), perchloroethylene2

 (PCE), 

and 1,1,2-trichloro-1,2,2-trifluorethane (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 Dearborn manufactured film capacitors at the SEC 

property. Film capacitors were assembled and then cleaned in a vapor degreaser; the chemicals TCA and 

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 Trichloroethylene is also known as TCE and trichloroethene. 

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 Perchloroethylene is also known as PCE and tetrachloroethlyene 

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General Dynamics Longwood NPL Listing Support Document September 2010 

TCE were used as cleaning agents in the vapor degreaser. 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). 

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In July 1997 a ground water recovery/treatment system was initiated by Great American Financial 

Resources, Inc. (GAFRI: legal successor to SEC) to minimize the amount of ground 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 approved and monitored by the FDEP). The system 

consisted of three horizontal wells in the surficial aquifer A-zone and one vertical well in the surficial 

aquifer B-zone; the A-zone wells were meant to capture and treat contaminants in the A-zone, and the Bzone well was meant primarily to limit the possibility 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 property 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 transferred 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 migrating northward with ground water flow from under 

the SEC property to under the General Dynamics property, this AOC originally included the General 

Dynamics property. The SEC site is currently being addressed under the Superfund Alternative Approach 

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General Dynamics Longwood NPL Listing Support Document September 2010 

(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. 

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However, during several investigations from 2001 through 2007, it became clear that sources of 

chlorinated ethenes were present on the General Dynamics property that were not associated with the 

SEC site, and that some portion of the ground water 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 proposal, 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 ground water samples contained hazardous substances 

significantly greater than background levels. In selecting background and contaminated samples used to 

substantiate observed releases, various 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 samples 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 observed 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 nearby drinking water wells as targets subject to 

potential contamination by the observed releases attributed to the site. Drinking water wells within a 4-

mile radius of the site are considered subject to potential contamination. Finally, a wellhead protection 

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General Dynamics Longwood NPL Listing Support Document September 2010 

area factor value was assigned to take into account the presence of a wellhead protection area within a 4-

mile radius of the site. 

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3. Summary of Comments 

Michael W. Sole submitted a comment on behalf of the 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 party (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 been 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 upgradient SEC site, and yet EPA inexplicably shifted 

focus to investigation of releases at the General 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 solvent 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 indication PCE was used at the site. Citing historical 

information and employee depositions regarding facility operations, General Dynamics concluded that 

“there is no evidence of actual releases of TCE (or any other solvent) to the soil or groundwater” at the 

site. 

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General 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: 

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• impermissibly concluding that the contaminants 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 caused 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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General Dynamics Longwood NPL Listing Support Document September 2010 

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. 

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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 contamination 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-treat 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 identified. Brown and Caldwell specifically questioned 

the dimensions assigned to Source No. 1. 

• Background samples have been incorrectly identified. Brown and Caldwell asserted that 

background and contaminated samples are in “the middle portions of groundwater contaminant 

plumes that originated on the Sprague property;” 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 both 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 contaminants—that previous septic system analyses 

near Source No. 1 did not find contaminants, and 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 documentation 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 General Dynamics Longwood site; the toxicity/mobility factor 

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General Dynamics Longwood NPL Listing Support Document September 2010 

used in HRS scoring for TCE is therefore incorrect 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. 

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Brown and Caldwell stated that, because only a fraction 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. 

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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 investigation 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. 

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Comment: Both General Dynamics and Brown and Caldwell imply that the site name should include 

“Gould” instead of “General Dynamics.” Both stated 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 notes that this was EPA’s previous terminology used 

in reports prior to the HRS documentation record. 

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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 the site General Dynamics Longwood. Since the primary purpose of an 

NPL listing is to inform the public that EPA has determined that the site warrants further investigation, 

EPA attempts to select the name that most clearly informs 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. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

EPA also attempts to select names that do not offend local sensitivities (see OSWER Directive 9345.1-08, 

Regional Quality Control Guidance for NPL Candidate Sites, 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. 

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EPA considers that the General Dynamics Longwood site’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 proposal 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-listing investigation activities.

318 3.3 Extent of the General Dynamics Longwood Site 

Comment: In several comments, General Dynamics and 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 been 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.” General 

Dynamics claimed that EPA “agreed that the contamination 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 onto the Gould [General Dynamics Longwood] site.” 

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General 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 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. 

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Response: The General Dynamics Longwood site is a separate site from the SEC site. However, because 

the commenters raised the issue of contamination from 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 believes 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 itself, 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 decision 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 preliminary 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 Longwood site, independent from the SEC site. As 

EPA explained on page 2 of a letter to General Dynamics on August 27, 2008 (attached to the General 

Dynamics comment letter as Reference I), remedial investigations conducted for the Sprague site 

indicated: 

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an additional source or sources of contamination to the groundwater plume under 

investigation, as well as another, entirely distinct 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 boundaries 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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

or threatened release of hazardous substances, pollutants, or contaminants. However, the fact that EPA 

initially identifies and lists the release 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. 

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CERCLA Section 105(a)(8)(A) requires EPA to list 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) defines a “facility” as the “site” where a hazardous 

substance has been “deposited, stored, placed, or otherwise come to be located.” The “come to be 

located” language gives EPA broad authority to clean up contamination when it has spread from the 

original source. 

 

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 may 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 purpose 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 therefore the boundaries of the release need not be 

exactly defined. Moreover, it generally is impossible 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 completed 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 previously estimated, and the site definition may be 

correspondingly expanded. In addition, if another, unrelated area of contamination is discovered 

elsewhere on the property, EPA may decide to evaluate that release for the NPL. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

406 3.4 Liability 

Comment: General Dynamics indicated that it was not responsible 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 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.” 

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Response: In as much as this comment concerns liability for the contamination at this site, whether any 

party may be liable for response costs is not considered when evaluating a site under the HRS. The NPL 

serves primarily as an informational and management tool. The identification of a site for the NPL is 

intended primarily to guide EPA in determining which sites warrant further investigation to assess the 

nature and extent of the human health and environmental risks associated with the site and to determine 

what CERCLA-financed remedial action(s), if any, may be appropriate. Identification of a site for the 

NPL does not reflect a judgment on the activities of the owner(s) or operator(s) of a site. It does not 

require those persons to undertake any action, nor does it assign any liability to any person. Subsequent 

government actions will be necessary in order to do so, and these actions will be attended by all 

appropriate procedural safeguards. This position, stated 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). 

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Implications of this comment on attribution of the release being evaluated at the General Dynamics 

Longwood site are addressed in section 3.12, Origin of Source Contamination, 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 intent and core purpose of the NPL.” General Dynamics 

stated that the purpose of the NPL is to: 

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• determine which sites warrant further investigation to assess the nature and extent of 

the human health and environmental risks associated with the site 

• identify when CERCLA-financed remedial 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. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

General Dynamics asserted “[l]isting the Gould [General Dynamics Longwood] site on the NPL serves 

none of these purposes.” 

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Response: The primary purpose of the NPL is stated in the 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: 

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The priority list serves primarily informational purposes, identifying for the States and 

the public those facilities and sites or other releases which appear to warrant remedial 

actions. Inclusion of a facility or site on the list does not in itself reflect a judgment of the 

activities of its owner or operator, it does not require those persons to undertake any 

action, nor does it assign liability to any person. Subsequent government actions will be 

necessary in order to do so, and these actions will be attended by all appropriate 

procedural safeguards. 

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 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. 

Specific related comments are addressed in the 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 offered to perform remedial investigation at the 

site, and therefore, this purpose of the NPL is already 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 that it “offered (and remains willing) to investigate 

environmental conditions at the Gould [General Dynamics Longwood] site in an effort to obtain further 

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General 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 the 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.” 

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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, although contamination from the two facilities may have 

comingled under a portion of the General Dynamics 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 Dynamics Longwood site under the SEC site SAA; NPL listing 

of the General Dynamics Longwood site is therefore necessary to achieve adequate evaluation of this site. 

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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, Associating 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 potential 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 further 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 not further the goal of identifying when a CERCLA 

financed remedial action is appropriate.” 

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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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

section 3.3, Extent of the General Dynamics Longwood Site, of this support document). Therefore, 

GAFRI is not obligated to address releases originating solely at the General Dynamics Longwood site. 

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Furthermore, inasmuch as this comment addresses responsibilities for remedial activities, it is not relevant 

to the listing decision. Listing a site only identifies 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 separate 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 activities already provide 

ample opportunity for public participation and involvement. 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 investigation since that was already accomplished when 

the SEC Site was enrolled in the Superfund Alternative Program.” 

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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. 

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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 FDEP 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 historical releases on the Gould [General Dynamics 

Longwood] site or migration from the SEC Site.” General Dynamics concluded that “listing the site will 

not further the goal of notifying potential PRPs that a CERCLA-financed remedial action may be 

necessary.” 

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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 any party (see section 3.4, Liability, of this support 

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General 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. 

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Comment: In several comments General Dynamics implied that, in decisions leading to the proposed 

listing of the General Dynamics Longwood site on the NPL, EPA had been arbitrary and capricious. 

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General Dynamics claimed that EPA “agreed that the contamination 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 onto the Gould [General Dynamics Longwood] site.” 

General Dynamics continued to state “[h]owever, for reasons that are not clear, in 2007, U.S. EPA 

reversed direction and began to focus on trying to prove that historical releases of chlorinated solvents 

had occurred on the Gould [General Dynamics Longwood] site.” General 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 letter 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 General 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, 2009, signature of an AOC by January 30, 2009, to 

perform an “unbounded” Remedial Investigation/Feasibility 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 abused 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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

site score, although some modifications to the evaluation 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 selected for use in the evaluation. 

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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 General Dynamics comment letter as Reference I), that 

remedial investigations conducted after the 2004 AOC with GAFRI indicated: 

an additional source or sources of contamination to the groundwater plume under 

investigation, as well as another, entirely distinct groundwater plume. This new source 

area was located on the property owned by Gould Publications [previously the General 

Dynamics property] and was contributing a different 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 not 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 notified of the previous investigations of the site, 

and that: 

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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 letter 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 advised 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. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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Response: All required CERCLA and Administrative Procedure Act notice requirements have been met 

regarding the promulgation of this site 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 

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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 final 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 solicited. 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. 

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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.” 

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Response: General Dynamics has not demonstrated the information 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 HRS evaluation of the General Dynamics Longwood site 

has been reviewed based on the comments submitted following the proposal of the site to the NPL. After 

this review, the site score remains unchanged. 

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647 3.9 Scoring Other Pathways 

Comment: Brown and Caldwell stated that EPA did not score the surface water migration pathway, soil 

exposure pathway, and air migration pathway, and stated that “Brown and Caldwell agrees that these 

pathways do not contribute to the site score and therefore need not be evaluated.” 

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General 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 determine 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. 

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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 include a brief qualitative discussion to present a more 

complete picture of the conditions and hazards at the 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 generally will not score additional pathways upon receiving 

new data as long as the site still meets the HRS cutoff score. However, any additional data characterizing 

site conditions could provide useful 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 completely 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 presented by Brown and Caldwell include: 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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• the background conditions used to establish Source 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. 

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Figure 3 details the eastern portion of the General Dynamics property which contains Source No. 2 and an 

observed release to ground water. 
General Dynamics Longwood NPL Listing Support Document 

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Figure 3: Eastern Portion of the General Dynamics Longwood Site 

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Note: Dotted red line presents the SEC SAA site. The general location of the General Dynamics Longwood site shline. Note that property boundaries are not depicted. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

The removal of Source No. 1 from the evaluation has resulted 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 established 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 consideration in the HRS evaluation at promulgation. 

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As Source No. 1 was removed from consideration from the General Dynamics Longwood site, the 4-mile 

target distance limit (TDL) was redrawn 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). 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 the 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 hydrogeologic conditions and groundwater 

flow patterns [emphasis in original comment] in the development of the HRS documentation record at 

proposal.” 

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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 consideration to the temporal impact from 

operation of the existing groundwater pump-and-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 significantly altered groundwater flow patterns 

between the Gould and Sprague properties from those originally depicted in 1992 by 

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General 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]. 

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Brown and Caldwell argued that the HRS evaluation did 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 flawed. 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 information from an April 2009 subsurface investigation at 

the General Dynamics Longwood site, and asserted that the presence and orientation of a clay layer in the 

surficial aquifer was not considered in developing the 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 increases 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-contaminated 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 comment]. 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 transported contaminants to the base of the A 

Zone where they were funneled by the clay topography northward to Source No. 2. 

Response: Subsurface geological and hydrogeological conditions 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, including 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 the HRS documentation record at proposal. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

To evaluate the HRS ground water pathway of a site, the scorer needs to delineate the aquifer being 

evaluated, including the existence of any interconnections with other water-bearing strata within 2 miles 

of the site source(s) and any discontinuities within the 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 evaluation 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 – Background, of this support 

document). This background contamination level is usually established by analyzing samples from 

upgradient of the site sources 

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Page 30 of the HRS documentation record at proposal describes the general regional geological strata and 

depositional formations in the subsurface 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 Coastal 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 undifferentiated deposits of the Holocene, Pleistocene, 

and Pliocene age; the Hawthorn Group of the 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, Florida area exists in two distinct units: the 

surficial aquifer and the Floridan aquifer. These aquifers are separated by a 

discontinuous intermediate confining unit (Hawthorn 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 divided into two aquifers of relatively high 

permeability, the Upper Floridan and the Lower 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 undifferentiated sediments of the Holocene, Pleistocene, 

and Pliocene ages; the intermediate confining 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 Oldsmar 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; 

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General 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). 

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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 top 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 Pliocene 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 record 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 Dynamics 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 surficial 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 depth 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 subsections of this support document. The aquifers 

being evaluated were properly delineated in the HRS 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 aquifer 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. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

851 3.11.1 Consideration of Pump-and-Treat System 

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. 

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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. 

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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 Source No. 2 or associated releases. 

Section 3.18.3, Effects of Pump and Treat, of this 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 eastern (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. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

882 3.11.2 Surficial Aquifer Clay Layer 

Comment: Brown and Caldwell presented information from an April 2009 subsurface investigation at the 

General Dynamics Longwood site, and asserted that the geometry of the surficial aquifer clay layer (A/B 

clay layer) between the upper and lower surficial aquifer acts as a mechanism for the transport of VOC 

(volatile organic compound)-contaminated ground water from the SEC site to the General Dynamics 

Longwood site. Brown and Caldwell stated that: 

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Lithologic profiling by Brown and Caldwell provides a much better understanding of 

hydrostratigraphy in the region of the sites 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 soil 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 underlying 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 products) 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 Brown 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 water 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 documentation 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 regarding the location of the clay layer provided by Brown 

and Caldwell, while potentially increasing the delineation of the clay layer, does not change the 

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General Dynamics Longwood NPL Listing Support Document September 2010 

delineation of the surficial aquifer or the identification 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 information 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 information obtained from this subsurface investigation at the 

General Dynamics Longwood site are not adequately documented. 

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The HRS does not contain specific instruction on how to delineate subsurface clay layers, except in 

establishing interconnection, where confining units are 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, combine the aquifers having interconnections in 

scoring the site. In addition, if observed ground 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 delineated 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 section 3.11, Description of Pathway, of this support 

document.) 

 

The HRS documentation record at proposal documents the existence of the A/B clay layer and that it was 

discontinuous in the vicinity of the site. Specifically, 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 data 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 

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General 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. 

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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 upgradient 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 release 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 and Origin of Source Contamination 

Comment: General Dynamics and Brown and Caldwell asserted that contamination associated with 

Source No. 2 was improperly linked to General Dynamics’ operations; they argued that Source No. 2 in 

the HRS documentation record was the result of operations 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 Longwood 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 sample 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 the capillary fringe of the upper water bearing 

zone. 

 32 
General 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 there 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 contaminated from migration of a hazardous substance. 

HRS Section 2.2.1, Identify sources, outlines the requirements to be followed when identifying sources at 

a site. It states: 

For the three migration pathways, identify the 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 substances 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, consider 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: 

 33 
General 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 being 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 contained the information necessary to establish Source 2 to 

be a contaminated soil source with a ground water containment value greater than 0. Page 23 of the HRS 

documentation record at proposal stated that “Source 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 method 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 southeastern 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. (Refs. 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 sampling event, and in accordance with the same 

sampling procedures. 

As cited above, three subsurface soil samples were 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, was 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 proposal, and Figure 4 presents the soil sample locations 

used to document the contaminated soil source. 

 34 
General Dynamics Longwood NPL Listing Support Document September 2010 

 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 

1075 Notes: 

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 limit 
General Dynamics Longwood NPL Listing Support Document 

1084 

Figure 4: Source Soil Sample Locations 

 36 
General Dynamics Longwood NPL Listing Support Document September 2010 

Regarding the ground water migration 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 consists of an area of contaminated soil 

located in the southeastern portion of Building 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 hazardous 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 appropriately associated a hazardous substance (1,1-DCE) 

with Source No. 2 through sampling, and by comparing 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 associated 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 substances 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 documented 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 discussion 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 the 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. 

 37 
General Dynamics Longwood NPL Listing Support Document September 2010 

1119 3.12.1 Evidence of Contamination 

Comment: Brown and Caldwell stated that “VOC concentrations in shallow soil beneath Source No. 2 

showed only minute concentrations of 1,1-dichloroethylene (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 commented 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 continued to state that “[c]arbon disulfide is not a 

breakdown product of TCE,” and “[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” concentrations 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 specify a minimum concentration of contaminants in a 

soil source, only that the soils came to be contaminated 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 present and came there due to migration. The other 

compounds mentioned by the commenter (PCE, TCE, and 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 evidence that there was not a release at this 

location. Brown and Caldwell’s April 2009 subsurface investigation evaluated 

environmental conditions at the Gould Property [General Dynamics property]. The 

investigation included advancing ten borings inside Building 3 (at AOC [area of 

concern]-A) to evaluate VOC concentrations in groundwater in the SAS. 

 38 
General 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 beneath 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 shown by photographs 

taken during Brown and Caldwell’s direct observations 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 borings 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 Building 3, Brown and Caldwell asserted that previous 

inspections at the General Dynamics property have shown 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 commented 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 the 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 VOC 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 within 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 contaminated 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 TCE 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 

 39 
General 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. This suggests the possible use of 1,1,1-TCA at the 

General Dynamics Longwood site. As noted by the 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 substance 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 technically 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 saturated zone or, at worst, in the capillary fringe 

atop the aquifer. Detection of 1,1-DCE reflects soil pore water that has migrated from 

the upgradient Sprague property. The capillary 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 the “[r]elatively high concentrations of VOCs” 

detected in ground water between 20 to 24 feet below 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 plume(s) originating at the Sprague site 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 sample6 [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 the subsurface conditions as pointed out by Brown and Caldwell in its comments and in 

Exhibit D of its comments. 

 40 
General 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 chlorinated 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 fashion 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 water into soil in the unsaturated zone. Thus, 

solvents detected at the General Dynamics property in the vicinity of Source 2 and the associated 

observed release are the result of a release at that property, 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 contractor 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. 

 41 
General Dynamics Longwood NPL Listing Support Document September 2010 

Response: Source No. 2 was established and included in the 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 Contamination, of this support document). The 

commenter appears to have confused the identification 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 substances available to a pathway, states: 

In evaluating each migration pathway, consider 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 record 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 consists of an area of contaminated soil 

located in the southeastern portion of Building 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 hazardous 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 appropriately assigns to Source No. 2 a ground water 

containment factor value of 10, which is greater than 0; thus, Source No. 2 is properly included in the 

 42 
General 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 accordance with its instructions, MACTEC identified two 

potential sources of contamination on the Gould [General Dynamics Longwood] site. . . . The second 

potential source was an alleged release from a vapor degreaser located in the southeast corner of Building 

3 at the Gould [General Dynamics Longwood] site, which is referred to in the HRS Record as ‘Source 

2.’” 

1306 

1307 

1308 

1309 

1310 

1311 

1312 

1313 Response: Source No. 2 was identified at proposal as a contaminated soil source. 

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 contaminated 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 source 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: 

1328 Number of source: 2 

Name of source: Contaminated soil in the southeastern corner of Building 3 (vicinity of 

the former vapor degreaser) 

1329 

1330 

1331 

1332 Source Type: Contaminated soil 

1333 

 43 
General 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 being 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 contamination 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 contamination, as explained in section 3.12, 

Origin of Source Contamination, of this support document, 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 “soils” are actually “saturated aquifer materials or, at 

the very worst, in one case, within the capillary fringe of the upper water-bearing zone.” 

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Response The source type for Source 2was correctly identified 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.” (

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1364 Webster’s New International 

1365 Dictionary, 3d ed., s.v. “soil.”) 

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 44 
General 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 under the heading Hazardous Substances Available to a 

Pathway, states that: 

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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 consists of an area of contaminated soil 

located in the southeastern portion of Building 3 on the General Dynamics property (Ref. 

16, pp. 14, 15, Exhibit 1). 

Based on the common interpretation of soil, as supported by the definition above, earth materials in the 

capillary fringe4

 of the ground water are still considered soils 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 this 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 Caldwell 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.” 

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Response: The background samples used to document that the Source 2 soil came to be contaminated due 

to migration were appropriate for this purpose. 

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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 Environment: Glossary, Abbreviations 

and Acronyms, available at http://www.epa.gov/OCEPAterms/cterms.html). 

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General Dynamics Longwood NPL Listing Support Document September 2010 

1400 The HRS Section 1.1, Definitions, defines source as: 

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Any area where a hazardous substance has been deposited, stored, disposed, or placed, 

plus those soils that have become contaminated 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 documented in the HRS documentation record at proposal by 

demonstrating the contaminant levels in the soil are greater 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 southeastern 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. (Refs. 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 sampling event, and in accordance with the same 

sampling procedures. 

Table 1 in section 3.12, Identification of a Source and 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 documented 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 increases in hazardous substances 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 migration 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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

significant increase of 1,1-DCE in the ground water underlying 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: 

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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 highest concentrations of 1,1-DCE detected 

during ground water investigations conducted 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 samples 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 Substances with Source No. 2 

Comment: General Dynamics and Brown and Caldwell questioned 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.” 

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1475 General Dynamics stated that: 

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General Dynamics Longwood NPL Listing Support Document September 2010 

in the Record describing the operational and 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. 

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General Dynamics asserted that: 

This is consistent with the 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 releases 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 General Dynamics facility, Brown and Caldwell asserted 

that “[p]rinted circuit board fabrication by General 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. 

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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 demonstrating it was in a source soil sample above background 

levels, as soil sample SB-038-03 was documented to contain 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 manufacturing cleaning processes. Although these other 

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General 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. 

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The discussion of other solvents within the HRS documentation record at proposal is intended to illustrate 

the general usage of solvents at the site, and no specific 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 other 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) 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 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 use at the General Dynamics facility was indicated. 

Regarding Brown and Caldwell’s assertion that former employees 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 considerable 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. 

 49 
General Dynamics Longwood NPL Listing Support Document September 2010 

1549 3.18 Likelihood of Release - Background 

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: 

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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 concentration trends and plume geometries over time as 

well as the presence and spatial distributions of both abiotic and biotic degradation 

products, and aquifer characteristics relative to groundwater velocity. 

Brown and Caldwell stated that their analysis: 

bolsters other elements of Brown and Caldwell’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]. Attributing 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 adequately established for the identification of an 

observed release to ground water by chemical analysis. 

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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 media 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 hazardous 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 exceeds the detection limit, an observed release 

is established when the sample measurement is 3 times or more above the background 

concentration. 

HRS Section 3.1, Likelihood of release, states: 

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General Dynamics Longwood NPL Listing Support Document September 2010 

For an aquifer, evaluate the likelihood of release factor category in terms of an observed 

release factor or a potential to release factor. 

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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 substances(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 support 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 observed 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 results for samples DPGW-23(22’) and DPGW-26(22’)5

, the 

background samples used in establishing observed release, are presented on Table 12 of the HRS 

documentation record at proposal. The hazardous substance 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 presents 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). 

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General Dynamics Longwood NPL Listing Support Document September 2010 

1622 Table 2: Samples Used in Establishing Observed Release by Chemical Analysis 

Background Samples Used in Establishing 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. 

33 

DPGW26(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 Site 

DPGW34(22') 1,1-DCE 26,500a μg/L 1.0 μg/L 28, pp. 1-

3; 51, pp. 2 

through 6; 

77, pp. 

9,10 

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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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

1643 3.18.1 Effects of Pump-and-Treat System 

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: 

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EPA’s contractor provides absolutely no consideration to the temporal impact from 

operation of the existing groundwater pump-an-treat system that was installed by GARFI 

along the northern border of the Sprague site. 

Brown and Caldwell remarked that “the pump and treat 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 water movement in the vicinity of the site has caused 

hazardous substances and their degradation products released on the Sprague site to migrate beneath the 

General Dynamics Longwood site, and “human manipulation 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 and 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 compared 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 surficial aquifer in the eastern portion of the site. 

(This trend is supported by Exhibit J of Brown and Caldwell’s comments [docket ID EPA-HQ-SFUND1669 

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General Dynamics Longwood NPL Listing Support Document September 2010 

2009-0067-0006.1], which documents a generally northward ground water flow during various time 

periods). 

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Additionally, using the commenter’s assertions regarding 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 theoretical 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 General Dynamics property, and did not affect the overall 

lateral flow direction except in the immediate vicinity of the pump-and-treat system. 

Since the pump-and-treat system did not significantly 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 locations, citing as an example, a contaminated 

sample under the SEC property. 

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Brown and Caldwell asserted that an “upgradient background sample on the Sprague property that was 

not considered in the Record is the 25,100 μg/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 well 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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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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 DPGW-28, the sample referenced by the commenter, 

contained high levels of TCE at 42 feet bls, whereas, 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 have 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 sample 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 sample 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 Document 

1735 Figure 5: Depiction of DPGW-28 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 

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General 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, the 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 documented at the observed release location. 

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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 ground water flow rate at the site was not 

accounted for in establishing background contamination levels. Brown and Caldwell asserted 

that: 

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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 means 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 property] 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 downward vertical gradient between the ‘A’ and 

the ‘B’ zones, which would tend to increase the 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 have 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. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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The HRS does not identify that flow rate should be considered in choosing a background location or in 

establishing background levels. However, since for HRS 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 eastern portion of the General Dynamics property, page 

44 of the HRS documentation record at proposal identifies 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 proposal 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. However, 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 General 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 support 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 principal 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 release 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 Document 

 59 

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Figure 6: Reviewed Upgradient Sample Locations 
General Dynamics Longwood NPL Listing Support Document September 2010 

Thus, while the commenter raised a theoretical possibility that the background well locations and the 

timing of the sampling could possibly have resulted 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. 

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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 documented that the ground water contamination 

under the General Dynamics property can be attributed to releases associated with General Dynamics 

operations and not attributed to releases attributable to SEC operations. General Dynamics alleged that: 

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No evidence has been presented to show that 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 Dynamics facility, Brown and Caldwell stated that: 

[p]rinted circuit board fabrication by General 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 present when operations were conducted at the 

Gould Property [General Dynamics property] also does not support a conclusion that 

there was an observed release. Depositions have been taken of a number of former 

employees and none have testified 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

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General 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. 

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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 vinyl 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). 

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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 media 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 exceeds the detection limit, an observed release 

is established when the sample 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 release 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 concentration for the site (see section 2.3). 

Some portion of the significant increase must be attributable to the site to 

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General 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. 

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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 – Background, of this support 

document.) 

That the significant increase in 1,1 DCE is attributable 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 elevated 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 conducted 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 and 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 attributed to the site, based on the finding that 1,1-DCE 

was associated with a site source, and that upgradient background concentrations of DCE found at the 

SEC site indicated that releases from the SEC site did 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 the range of feet per day, EPA has reviewed past 

sampling and analysis data from sample locations upgradient of the release sample location (see section 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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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 the 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 reviewed 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 review 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 appear 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 section 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 ground water flow direction maps provided in the 

references to the HRS documentation record at proposal. As discussed in previous sections of this 

support document, a generally northern flow direction of ground water has been documented from various 

investigations at the site.
General Dynamics Longwood NPL Listing Support Document 

 64 

Figure 7: Area Considered Hydraulically Upgradient of Observed Release Location 

Note: The hatch-marked area represents the area hydraulically upgradient of the observed release sample. Information 

taken from this area is presented in Attachment 3 to this support document. 
General Dynamics Longwood NPL Listing Support Document September 2010 

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Analytical data from ground water samples in this area determined to be upgradient of the observed 

release sample are presented in Attachment 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 Detection of Either PCE, TCE, 1,1-DCE, or 1,1,1-TCA in 

Ground Water Samples1 

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 2022 Direct-push or monitoring well ground water samples 

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The highest 1,1-DCE concentration found at any sample location upgradient of the release sample 

location was 1,700 μg/L; using this as a background level would still result in a more than 3-fold increase 

in 1,1-DCE levels in the observed release sample (which 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-DCE in the release sample, as Brown and Caldwell have 

argued that 1,1-DCE is a minor degradation product 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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

2038 • 3.19.2 Ground Water Flow Direction 

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• 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 primary breakdown product of 1,1,1-TCA”. 

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Brown and Caldwell stated that “[t]he Record uses incorrect HRS scoring factors [emphasis in original 

comment] because EPA’s contractor incorrectly identifies 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 attributable 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 the fact is well documented that 1,1,1-TCA 

breaks down to 1,1-DCE and 1,1-DCA depending 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 and 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-TCA was confirmed at the Sprague site many 

years ago. . . . Mischaracterizing the byproducts from TCE degradation is a 

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General 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]. 

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Brown and Caldwell concluded 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 Gould Property [General Dynamics property]. 

Brown and Caldwell also commented that “[t]o state that 1,1-DCE is anything other than a minor 

breakdown product of TCE is intentionally 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 present 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 degradation product of any particular substance, or even its presence being 

a result of degradation of another substance. The release 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 Contamination, 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 significant increase in 1,1-DCE found in the release sample (see section 3.19, 

Likelihood of Release – Attribution, of this support document). 

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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 assumption 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 the 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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General Dynamics Longwood NPL Listing Support Document September 2010 

(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 and through soil, the ratio of the individual constituents 

at any given location will vary as the contaminants migrate further from their point of origin. 

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Also, the rate of degradation and the 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 buildings 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 parent solvents (such as 1,1,1-TCA) were used at 

the SEC property and not at the General Dynamics property, this has not been completely demonstrated. 

The HRS documentation record at proposal describes 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, Identification 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 Longwood 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 General 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 substance documented at the General Dynamics Longwood site indicate 

that the 1,1-DCE found in the observed release was associated 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 rationale for attributing the increased ground water 

contamination levels to releases from General Dynamics operations was flawed. 

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General 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: 

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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 HRS 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 historic 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). 

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Ground water flow direction information is not specifically 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 information is often used to establish a background contaminant 

level to show a significant increase in a hazardous substance 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 samples 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 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 appear to have a significant 

impact on the overall flow direction between the background and release wells used to establish the 

observed release in the eastern part of the General Dynamics Longwood site. (See section 3.11, 

Description of Pathway, of this support document.) 

An observed release by chemical analysis was documented 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 establish the significant increase in 1,1-DCE levels were 

from upgradient sample locations, ruling out the possibility of contamination migration from the SEC site 

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General Dynamics Longwood NPL Listing Support Document September 2010 

to the release location, and thus the significant increase 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 water flow patterns at the site were identified, and the subsurface 

geological conditions were properly evaluated for HRS purposes, the evaluation of observed release 

background, and thus the likelihood of release factor of the HRS score for this site was properly 

established. 

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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 dense solvent contamination would migrate along this clay 

layer from under the Sprague site to under the General Dynamics site. 

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Brown and Caldwell stated: 

The geometry of this impermeable layer represents a transport mechanism for the 

northward migration of VOC-contaminated 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 comment]. 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 funneled by the clay topography northward to 

Source No. 2. 

Additionally, Brown and Caldwell alleged that the results 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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General Dynamics Longwood NPL Listing Support Document September 2010 

These VOCs (TCE and 1,1,1,-TCA and their breakdown products) appear to have been 

confined by the topography of the unit. This configuration suggests that northwardmigrating 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. 

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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. 

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Chlorinated solvents moving through the subsurface 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, samples 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 have caused the significant increase in 1,1-DCE in the 

release sample in the eastern portion of the General 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 Release – Attribution, and, and Attachment 3 of this 

support document). There is, therefore, no evidence that 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 under the Sprague property had migrated to under the 

General Dynamics property. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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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 contamination 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 upgradient 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 investigations, 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 2005 (see analytical results for background and 

release samples in pp. 39-52 of the HRS documentation record at proposal). This release has 

been correctly attributed to the General Dynamics Longwood site (see section 3.19, Likelihood of 

Release – Attribution, of this support document). Conclusions from previous studies which 

identified the potential origin of hazardous substances represent conclusions made at that 

particular time using available environmental and analytical information; they do not disprove the 

establishment of the observed release. 

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Since these earlier conclusions or assumptions, further sampling and analysis has taken place—

including the 2005 investigation used to establish the observed release in the HRS documentation 

record at proposal—which have advanced the understanding 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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General Dynamics Longwood NPL Listing Support Document September 2010 

comment letter as Reference I) that remedial investigations, conducted after the 2004 AOC with 

GAFRI, indicated the presence of: 

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an additional source or sources of contamination to the groundwater plume under 

investigation, as well as another, entirely distinct groundwater plume. This new source 

area was located on the property owned by Gould Publications [previously the General 

Dynamics property] and was contributing a different contaminant from those found to be 

emanating from the Sprague Site. 

Thus, although early findings suggested that the contaminants under the General Dynamics Longwood 

site could have originated under the SEC site, this previous understanding 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: 

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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 upgradient 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 the 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]. 

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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 contamination 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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

SEC property. The chlorinated solvents just as likely moved downward through the soil and dissolved or 

moved as free product into the ground water, since their high density causes them to sink. 

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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 previously 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 indicates there must be another source or “origin” of 

the 1,1 DCE or of its parent substance. The source type for Source No. 2 is identified as contaminated 

soil, which, as stated in the HRS definition of source (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 solvents, 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 support document). These findings, and the lack of any 

evidence from 18 years of sampling of upgradient contamination 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 Release – Background, and above in section 3.19, 

Likelihood of Release – Attribution, of this support document). 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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

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3.20 Waste Characteristics 

General Dynamics and Brown and Caldwell challenged the HRS documentation record evaluation of 

waste characteristics. Specific comments are addressed 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. 

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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 the 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 TCE 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 changes 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 release, but also to substances associated with a 

source with a containment value greater than zero. Source 2 is such a source. 

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HRS Section 3.2, Waste Characteristics, states: 

Evaluate the waste characteristics factor category for an aquifer based on two factors: 

toxicity/mobility and hazardous waste quantity. Evaluate only those hazardous 

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General Dynamics Longwood NPL Listing Support Document September 2010 

substances available to migrate from the sources at the site to ground water. Such 

hazardous substances include: 

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• 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 aquifer 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 the 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 highest toxicity/mobility factor value for the 

aquifer being evaluated to assign the value to the 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 being evaluated. Enter this value in Table 

3-1. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

The HRS documentation record at proposal explained 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 Source No. 2 and in the observed release in the eastern 

portion of the site. Below is a discussion of the assignment of the combined toxicity/mobility factor value 

based only on 1,1-DCE using information contained in the HRS documentation record at proposal. 

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Page 26 of the HRS documentation record at proposal 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 consists of an area of contaminated soil 

located in the southeastern portion of Building 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 hazardous 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). 

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 for 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 factor 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 for 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 for 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 mobility 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 

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General Dynamics Longwood NPL Listing Support Document September 2010 

Longwood site is 100. Using this toxicity/mobility value 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). 

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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 challenged 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 Dynamics Longwood site. Brown and Caldwell stated that: 

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there is no observed evidence of a solvent release to soil on the Gould Property [General 

Dynamics property] and, based on prior sampling 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 site 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 noted 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. 

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General Dynamics Longwood NPL Listing Support Document September 2010 

2516 HRS Section 2.4.2, Hazardous waste quantity, states: 

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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 the 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 contamination) 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 mass 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 adequately 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: 

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General 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. . . . 

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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 contamination for the pathway being evaluated 

and round this sum to the nearest integer, except: 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 has 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 record 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 Source 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 Source No. 2, information establishing “with reasonable 

confidence,” the total mass of CERCLA hazardous substances 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 hazardous waste quantity was evaluated for Tier D, Area, 

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General 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. 

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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 presented in HRS section 2.4.2.2 above. Because the 

hazardous waste quantity estimate is greater than zero, 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 factor 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 Longwood 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 drinking water wells in determining the site score. 

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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 groundwater because EPA’s contractor did not consider 

only downgradient drinking water sources.” 

Further, Brown and Caldwell indicated that the population factor value is overstated. Referencing Section 

3.3.2.4 of the HRS, Brown and Caldwell stated that: 

the population to be included in the evaluation 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 calculated by EPA’s contractor is incorrect [emphasis 

in original comment]. 

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General 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: 

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[t]o be consistent with the NCP and to ensure that only ‘those persons served by drinking 

water from points of withdrawal subject to potential contamination’ are considered, the 

potential contamination population factor value 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 Lakes 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 located >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 their 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 proposal. 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 

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2667 

2668 

2669 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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: 

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The target distance limit defines the maximum 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 discontinuities 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 distance 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. Determine 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 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. 

Then the HRS directs the scorer to identify which wells are considered actually contaminated 

(e.g., level I or level II). All people drinking 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 drinking 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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General Dynamics Longwood NPL Listing Support Document September 2010 

- For this portion of the population, determine the number of people included 

within each “Karst” distance category in Table 3-12. 

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Pages 58-59 of the HRS documentation record at proposal 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 proposal 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 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). 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 are 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 openings that occur along joints or bedding 

planes. In some areas, flow may be through 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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General Dynamics Longwood NPL Listing Support Document September 2010 

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 

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Brown and Caldwell is incorrect in its assertion that the target score should not include targets associated 

with wells considered to be upgradient of the source. 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 information. 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 uniform system for scoring a large number of sites 

expeditiously with commonly-available data. EPA reconsidered 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 contamination of drinking water wells. The 

HRS uses a radius of 4 miles around the site when determining 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 aquifer of concern between the site and the well being 

scored for HRS purposes (55 FR 51595). 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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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). Conversely, 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 population values presented by Brown and Caldwell were 

considered in the evaluation, the site would still maximize the pathway score when the likelihood of 

release and waste characteristics factor values remain. That is, the likelihood of release factor value of 

550, multiplied by the waste characteristics factor value 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 82,500, 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 proposal) 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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General Dynamics Longwood NPL Listing Support Document September 2010 

2800 Table 5: Distance-Weighted Population Values as Established at Promulgation 

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 

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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” distance 

category 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 has no impact on the ground water migration pathway 

score of 100.00, or the HRS site score of 50.00 as proposed. 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 corrected, result in an HRS ranking score of zero.” 

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General Dynamics Longwood NPL Listing Support Document September 2010 

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 water in the eastern part of the site. 

2822 

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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 site 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 (higher 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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General Dynamics Longwood NPL Listing Support Document September 2010 

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 (Sgw), (highest value from line 12 for all 

aquifers valuated)c

100 100.00 

2837 

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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 S2

 pathway 

Ground Water Migration Pathway Score (Sgw) 100 10,000 

Surface Water Migration Pathway Score (Ssw) NS NS 

Soil Exposure Pathway Score (Ss) NS NS 

Air Migration Score (Sa) NS NS 

S2

gw + S2sw + S2s + S2a 10,000 

(S2

gw + S2sw + S2s + S2a)/4 2,500 

 / (S2

gw + S2sw + S2s + S2a)/4 50.00 

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2847 Note: 

2848 

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NS = Not scored 

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General Dynamics Longwood NPL Listing Support Document September 2010 

2850 Ground Water Migration Pathway Score 

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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 targets 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 support 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 observed release by chemical analysis is 

analytical evidence of a hazardous substance 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 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 exceeds the detection limit, an observed release 

is established when the sample 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 substances(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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General Dynamics Longwood NPL Listing Support Document September 2010 

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, Likelihood 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 ground water in sample DPGW-34(22’) at levels 

significantly above (more than 3-fold) background samples. 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 factor 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; this 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 sources 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). 

2916 Toxicity/Mobility

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 aquifer 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: 

 91 
General Dynamics Longwood NPL Listing Support Document September 2010 

• For any hazardous substance that meets the 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 highest toxicity/mobility factor value for the 

aquifer being evaluated to assign the value to the 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 for 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 factor 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, Toxicity/Mobility, of this support document. 

2954 Hazardous Waste Quantity

2955 

2956 

2957 

2958 

2959 

2960 

2961 

2962 

2963 

2964 

2965 

2966 

2967 

2968 

2969 

2970 

Source No. 2 was established according to HRS criteria. 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 contaminated from migration of a hazardous substance. 

HRS Section 2.2.1, Identify sources, outlines the requirements to be followed when identifying sources at 

a site. It states: 

For the three migration pathways, identify the 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 substances available to a pathway, directs the scorer: 

 92 
General Dynamics Longwood NPL Listing Support Document September 2010 

In evaluating each migration pathway, consider 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 being evaluated. Enter this value in Table 3-

1. 

The HRS documentation record at proposal appropriately 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. Additionally, 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 the 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. 

 93 
General Dynamics Longwood NPL Listing Support Document September 2010 

3014 • Volume. 

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 contamination for the pathway being evaluated 

and round this sum to the nearest integer, except: 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 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 record 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 Source 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 waste 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, 

 94 
General Dynamics Longwood NPL Listing Support Document September 2010 

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 hazardous waste quantity factor value of 10 results in 

a waste characteristics product of 1,000; which corresponds 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 record 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. Determine the targets to be included in 

evaluating these factors for an aquifer as specified in section 3.0. 

3078 Nearest Well

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 drawing 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. 

3097 Population

3098 HRS Section 3.3.2, Population, states: 

 95 
General Dynamics Longwood NPL Listing Support Document September 2010 

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 

3109 Resources

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 highest 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. 

3131 Wellhead Protection Area

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 applicable 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 Wellhead 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 applicable to the aquifer being evaluated or 

overlying aquifers. 

 96 
General Dynamics Longwood NPL Listing Support Document September 2010 

Regarding the municipal water systems within the 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 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). 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 through porous limestone, and is enhanced by 

networks of small fractures or solution openings that occur along joints or bedding 

planes. In some areas, flow may be through 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 Source 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. 

 97 
General Dynamics Longwood NPL Listing Support Document September 2010 

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 explained on page 63 of the HRS documentation record at 

proposal, which states, “[w]ells used for resources were 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 the 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 protection 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, population, 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 Dynamics 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) results 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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General Dynamics Longwood NPL Listing Support Document September 2010 

 99 

3220 

3221 

3222 

3223 

3224 

3225 

3226 

3227 

3228 

3229 

3230 

3231 

3232 

3233 

3234 

is taken of the value of the squared ground water migration pathway divided by 4 (√1002

 / 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