Final

Record of Decision forSurface Media at

RSA-011, Former Sewage Treatment Plant No. 1Operable Unit 10

Redstone ArsenalMadison County, Alabama

U.S. EPA ID No. AL7 210 020 742

Prepared for:

U.S. Army Corps of Engineers, Savannah DistrictP.O. Box 889

Savannah, Georgia 31402-0889

Prepared by:

Shaw Environmental, Inc.312 Directors DriveKnoxville, TN 37923

Delivery Order 0020Contract No. DACA21-96-D-0018

Shaw Project No. 840891

August 2007

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10450095

Table of Contents.

Page

List of Tables iii

List of Figures iv

List of Acronyms v

1.0 The Declaration 1-1

1.1 Site Name and Location 1-1

1.2 Statement of Basis and Purpose 1-1

1.3 Description of the Selected Remedy 1-2

1.4 Statutory Determinations 1-2

1.5 Authorizing Signatures 1-3

2.0 Decision Summary 2-1

2.1 Site Name, Location, and Description 2-1

2.2 Site History and Enforcement Activities 2-2

2.2.1 History of Site Activities 2-2

2.2.2 History of Investigative Activities 2-3

2.2.3 History of CERCLA Enforcement Activities 2-3

2.3 Community Participation 2-4

2.4 Scope and Role of Operable Unit or Response Action 2-5

2.4.1 Overall Remedial Strategy for Redstone Arsenal and RSA-011 2-5

2.4.2 Scope of Problems Addressed by RSA-011 Response Action 2-6

2.4.3 Relationship of Proposed Action to Removal or Other Operable Units 2-6

2.5 Site Characteristics 2-7

2.5.1 Conceptual Site Model 2-7

2.5.2 Nature and Extent of Contamination 2-9

2.5.2.1 Nature and Extent of Soil Contamination 2-10

2.5.2.2 Nature and Extent of Groundwater Contamination 2-11

2.5.2.3 Fate and Transport 2-12

2.6 Current and Potential Future Land and Resources Use 2-12

2.6.1 Current and Future Land Use 2-12

2.6.2 Groundwater Use 2-13

2.6.3 Surface Water Use 2-14

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Table of Contents (Continued).

Page

2.7 Site Risks 2-14

2.7.1 Baseline Human Health Risk Assessment 2-14

2.7.1.1 Identification of Chemicals of Potential Concern 2-14

2.7.1.2 Exposure Assessment 2-15

2.7.1.3 Toxicity Assessment 2-16

2.7.1.4 Risk Characterization 2-17

2.7.1.5 Summary of the Baseline Human Health Risk Assessment 2-18

2.7.2 Screening-Level Ecological Risk Assessment 2-19

2.7.3 Risk Summary 2-20

2.7.4 Basis for Action 2-20

2.8 Documentation of Significant Change 2-21

3.0 Responsiveness Summary 3-1

4.0 References 4-1

Tables

Figures

Appendix A - Glossary of Terms

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List of Tables.

Table Title Follows Text

\ History of Investigative Activities, RSA-011

2 Surface Soil Data Summary, RSA-011

3 Subsurface Soil Data Summary, RSA-011

4 Soil Vapor Data Summary, RSA-011

5 Groundwater Data Summary, RSA-011

6 Total Cancer Risks and Noncancer Hazards for RSA-011 ReceptorsIncluding Background-Related Metals

7 Total Cancer Risks and Noncancer Hazards for RSA-011 Receptors WithoutBackground-Related Metals

8 Results of the Vapor Intrusion Evaluation for Trichloroethene at RSA-011

9 Summary of Screening-Level Ecological Risk Assessment Results for RSA-011

K.N7\RSA\RSA-01 I\ROD\D-F\OI l-DF-ROD.doc\8/M/2007\9:53:38 AM 111

List of Figures.

Figure Title Follows Text

1 Location of Redstone Arsenal and Surrounding Cities of Madison County, Alabama

2 RSA-011 Site Location Map

3 RSA-011 Site Photos Dated April 2, 2003

4 RSA-011 Conceptual Site Model

5 Human Health and Ecological Conceptual Site Exposure Model, RSA-011,Operable Unit 10

6 RSA-011 Existing Sample Locations

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List of Acronyms

ADEM Alabama Department of Environmental Management

Army U.S. Army Garrison - Redstone

bgs below ground surface

BHHRA baseline human health risk assessment

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

COC chemical of concern

COPC chemical of potential concern

COPEC chemical of potential ecological concern

CSM conceptual site model

DAF4 dilution attenuation factor 4

EPA U.S. Environmental Protection Agency

HI hazard index

HQ hazard quotient

[ROD interim record of decision

ug/L micrograms per liter

mg/kg milligrams per kilogram

OU operable unit

PCB polychlorinated biphenyl

PP Proposed Plan

RARE Redstone Arsenal Rocket Engine

RCRA Resource Conservation and Recovery Act

RfD reference dose

RI remedial investigation

ROD Record of Decision

RSA-011 Former Sewage Treatment Plant No. 1

SAC site access control

SAIC Science Applications International Corporation

SB Statement of Basis

Shaw Shaw Environmental, Inc.

SLERA screening-level ecological risk assessment

SSL soil screening level

SVOC semivolatile organic compound

TCE trichloroethene

VOC volatile organic compound

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1.0 The Declaration

1.1 Site Name and Location

Former Sewage Treatment Plant No. IRSA-011, Operable Unit (OU) 10Redstone ArsenalMadison County, Alabama

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)Identification Number: ALT 210 020 742

U.S. Army Garrison - Redstone

1.2 Statement of Basis and Purpose

This Record of Decision (ROD) presents the Selected Remedy for the surface media (surface

soil, subsurface soil, and soil vapor) at the Former Sewage Treatment Plant No. 1 (RSA-011) at

Redstone Arsenal in Madison County, Alabama. The remedy was chosen in accordance with

CERCLA as amended by the Superfund Amendments and Reauthorization Act of 1986, and, to

the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan,

40 Code of Federal Regulations Part 300. The remedy was also chosen to be in compliance with

the Resource Conservation and Recovery Act (RCRA).

The remedy selection was based on information contained in the Administrative Record for this

site, which has been developed in accordance with Section 113 (k) of CERCLA and which is

available for review at the locations presented in Section 2.3 of this ROD. Key documents in the

Administrative Record include the following:

• Site inspection report (Science Applications International Corporation [SAIC],1996)

• Remedial investigation (Rl) report (Shaw Environmental, Inc. [Shaw], 2007a)

. Statement of Basis (SB)TProposed Plan (PP) for RSA-011 (Shaw, 2007b).

This document is issued by the U.S. Army Garrison - Redstone (hereinafter referred to as the

Army), the lead agency for site activities under CERCLA at Redstone Arsenal. The U.S.

Environmental Protection Agency (EPA) Region 4 and the Alabama Department of

Environmental Management (ADEM) are the regulatory agencies providing oversight of the

Army's cleanup program at Redstone Arsenal. The Army and EPA Region 4 have selected the

final remedy for RSA-011, and ADEM concurs.

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1.3 Description of the Selected Remedy

Conditions at RSA-Ol I are such that a No Action remedy is appropriate for the surface media

(surface soil, subsurface soil, and soil vapor), as supported by the following:

• No chemicals were detected in surface media at concentrations that would meetEPA's definition of a principal threat waste.

• Residual concentrations of perchlorate do not pose a threat of continued leachingto ground water at RSA-Ol I. Perchlorate was analyzed for in 92 surface andsubsurface soil samples and detected in a very small percentage (9.8 percent) ofsamples, with a maximum concentration of only 0.044 J milligrams per kilograms(mg/kg). Perchlorate in 6 of the 92 samples collected (6.5 percent) hadconcentrations exceeding the dilution attenuation factor 4 (DAF<t) soil screeninglevel (SSL). These exceedances occurred at widely spaced locations separated bylocations where perchlorate was not detected or was detected at concentrations lessthan the DAF4 SSL. The average of all detected concentrations of perchlorate atRSA-Ol I (0.022 mg/kg) was found to be almost identical to the 0.021 mg/kgDA?4 SSL. No significant perchlorate mass remains in any location on RSA-Ol I.

• The results of the risk assessments for RSA-Ol I indicate no unacceptable risks tohuman health and the environment are posed by site-related contaminants in soil orsoil vapor.

• No action (CERCLA or RCRA) is necessary for RSA-Ol I surface media and nomonitoring or restrictions are necessary to ensure that no unacceptable exposure torisks is posed by the surface media in the future.

The groundwater cleanup under RSA-Ol I will proceed under a broader watershed approach (i.e.,

RSA-146 groundwater site) that is not part of this scope.

1.4 Statutory Determinations

No remedial action is necessary to ensure protection of human health and the environment at

RSA-Ol I. Therefore, none of the CERCLA I2l statutory determinations need to be addressed.

Because this No Action remedy wil l not result in hazardous substances, pollutants, or

contaminants remaining on site above levels that allow for unlimited use and unrestricted

exposure, a five-year review is not required.

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1.5 Authorizing Signatures

This ROD documents the Selected Remedy for surface media at RSA-Ol 1 in OU-10 at Redstone

Arsenal. The remedy was selected by the Army and EPA Region 4, with concurrence by

ADEM.

:'l

John A. OlshefskiColonel, US ArmyGarrison Commander

Date DateFranklin E. Hill, DirectofSuperfund DivisionU.S. Environmental Protection Agency,Region 4

Concurrence:

Wm. Gerald Hardy, <Land DivisionAlabama Department of Environmental Management

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2.0 Decision Summary

2.1 Site Name, Location, and Description

Former Sewage Treatment Plant No. IR S A - O l l , O U - l ORedstone ArsenalMadison County, Alabama

CERCLA Identification Number: AL7 210 020 742

Lead Agency: Army

Redstone Arsenal is located in Madison County in the northern portion of Alabama (Figure I).

Redstone Arsenal is in the southwestern portion of Madison County, Alabama, and is bounded

by the city of Huntsville on the north and east and the Tennessee River to the south. The city of

Madison and the town of Triana are northwest and southwest, respectively, of Redstone Arsenal

(Figure I).

Redstone Arsenal is a U.S. Army facility that encompasses approximately 38,300 acres of land,

all of which are either owned or controlled by the Army (Figures I and 2). Development within

Redstone Arsenal has largely revolved around the historical need to produce (and later dispose

of) conventional and chemical munitions and, more recently, to develop and test missiles and

rockets. Production of chemical wastes have been the result of these processes since operations

began in the early 1940s. Redstone Arsenal is composed of the Wheeler National Wildlife

Refuge to the south; industrial areas in the southeast; administrative facilities at the National

Aeronautics and Space Administration's George C. Marshall Space Flight Center in the central

portion; and family housing and commercial, recreational, and medical centers in the north

portion. Missile/rocket testing and munitions storage, along with the associated range fans, test

area safety fans, and explosive safety-quantity distance arcs, have been reserved for the southern

portion of Redstone Arsenal.

RSA-011 is located in the eastern section of the Redstone Arsenal Rocket Engine (RARE) North

Plant area in OU-10. The site measures approximately 3 acres (Figure 2). The plant was

constructed in the 1940s and was used for treatment of domestic sewage generated in the eastern

portion of Redstone Arsenal and wastewater from rocket propellent manufacturing operations

generated in the RARE North Plant area. In 1992, wastewater treatment was discontinued at

RSA-011, and the plant was removed from service. Types of waste managed at the plant

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included liquids and sludges contaminated with metals and organic constituents typically found

in municipal sludges. Influent from the RARE North Plant operations could have contained

volatile organic compounds (VOC), primarily trichloroethene (TCE), and perchlorate related to

the operations of the tenant at the time, the Thiokol Corporation, though surface media present at

RSA-011 no longer contain significant masses of either of these compounds.

The Sewage Treatment Plant consisted of two separate treatment units (1A and IB). The first

unit (1 A, to the south) was built in 1942 and the second (IB, north of 1 A) was constructed in

1946 (Figure 2). The combined treatment capacity of the two units was 0.395 million gallons per

day and provided primary and secondary treatment of incoming wastewater. Once treated, the

effluent streams from both units were combined, chlorinated, and released through a drain line

leading north/northwest to Huntsville Spring Branch. In approximately 1983, a lift (pumping)

station was installed at the treatment plant in conjunction with a major sewer outfall project that

placed all of the operating treatment plants on Redstone Arsenal (Plants 1, 3, and 4) into a

common outfall for discharging treated effluent to the river. When Sewage Treatment Plant No.

1 was removed from service in 1992, the lift station was converted to pump raw sewage to the

new Buxton Road treatment plant.

2.2 Site History and Enforcement Activities

This section presents a history of site activities and describes investigative and CERCLA

enforcement activities at RSA-011.

2.2.1 History of Site Activities

The Sewage Treatment Plant was in operation from the 1940s until 1992 for treatment of

domestic sewage generated in the eastern portion of Redstone Arsenal and wastewater from

propellant manufacturing operations generated in the RARE North Plant. The two treatment

units present at RSA-011 were involved in similar processes, but they differed in shape and size.

Raw sewage entered the treatment plant through underground lines along the southern boundary.

Raw sewage flowed through a mechanical bar screen into separate sumps for each treatment unit.

Building 7902 housed the main pump station. The sewage was pumped from the sumps to a

primary clarifier (1A: Bui ld ing 7904; IB: north part of 7909). After primary treatment, sewage

flowed via gravity-fed underground lines to a trickling filter (1 A: Building 7906; IB: Building

7910) and then to a secondary clarifier (1 A: Building 7913; IB: south portion of Building 7909).

The treated waste was chlorinated before discharging through a gravity drain line leading to the

north-northwest to Huntsville Spring Branch. Sludge from the primary and secondary clarifiers

passed through digesters (1 A: Building 7914; IB: Building 7911) before disposal in one of the

two sludge drying beds. Both sludge beds were shallow, unlined features equipped with a

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collection system to recycle filtrate to the aeration unit. Sludge from the drying beds was

periodically removed and disposed in the sanitary landfill at Redstone Arsenal (RSA-010, a

CERCLA site being investigated under separate scope). Figure 3 shows the inactive treatment

units that remain at the site.

A more detailed description of the site history can be found in Section 1.4 in the RI report (Shaw,

2007a).

2.2.2 History of Investigative Activities

A number of assessments/investigations have been conducted at RSA-011. These include the

following:

• RSA-011 was evaluated in an initial RCRA facility assessment conducted in 1988by EPA (A.T. Kearney, 1989). No samples were collected.

• A final RCRA facility assessment was conducted in 1989 by the Army (Geraghty& Miller, Inc., 1991). The RSA-011 site was revisited and photographed. Nosamples were collected.

• A site inspection was conducted in 1996 to determine the presence or absence ofcontamination in soil and groundwater (SAIC, 1996).

• A Phase I RI was conducted at RSA-011 in 1997-1998 to determine the nature andextent of contamination in soil and groundwater (Shaw, 2007a).

• Phase II RI activities were conducted in 2002 to further investigate surface andsubsurface soil contamination (Shaw, 2007a).

• A supplemental RI was conducted in 2004 to more completely define the natureand extent of soil contamination at the site where data gaps were noted (Shaw,2007a).

• Soil vapor sampling was conducted at the site in April 2007 to evaluateconcentrations of VOCs in soil vapor that may pose risks via the vapor intrusionexposure pathway at RSA-011 (Shaw, 2007a).

Table 1 presents more details of the investigative activities conducted at RSA-011.

2.2.3 History of CERCLA Enforcement Activities

No CERCLA removal or remedial enforcement activities have been conducted to date at RSA-

011.

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2.3 Community Participation

Throughout Redstone Arsenal's history, community concern and involvement have been low.

The Army has kept the community and other interested parties apprised of site activities through

the following:

• Informational materials and presentations• Press releases• Administrative Record file and information repositories• Public meetings and comment periods.

Informational materials, such as fact sheets, are sent to community members on an ongoing

basis. A mailing list of community members and individuals that have requested information is

maintained. Presentations and tours for community groups are aimed specifically for members

of the public and are also announced through mailings or by the media. A community relations

plan (Shaw, 2006) has been published to keep the community informed of cleanup progress at

Redstone Arsenal and to provide opportunities for the public to interact with the Army on

remedial activities.

Documents in the Administrative Record file for RSA-011 and other CERCLA sites at Redstone

Arsenal can be found at the information repositories maintained at the following locations:

U.S. Army Garrison, Redstone Arsenal

Contact: Ms. Salee Sloan (256) 842-0314Location: Environmental Management Division, Building 4488, Martin Road, Room

A327Business Hours: Monday - Friday 7:00 a.m. - 4:30 p.m. Central time zone

Triana Public Library (Triana Youth Center)

Contact: Ms. Wendy Quails (256) 532-5969Location: 280 Zierdt Road, Triana, Alabama 35758Business Hours: Monday - Friday 11:30 a.m. - 6 p.m. and First and Third Saturdays 12:00 p.m.

- 5 p.m. Central time zone

Huntsville/Madison County Public Library

Contact: Ms. Anne FullerLocation: Heritage Room, 915 Monroe Street, Huntsville, Alabama 35804Business Hours: Monday - Thursday 9 a.m. - 9 p.m., Friday - Saturday 9 a.m. - 5 p.m.,

Sunday 1 p.m. - 5 p.m. Central time zone

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Documents covering RSA-011 can also be obtained on line from the Redstone Arsenal website:

www.environmental.redstone.armv.mil.

The final RI report for RSA-011 (Shaw, 2007a) was released in June 2007 to the Administrative

Record file and made available to the public. The SB/PP (Shaw, 2007b) was released in July

2007 for public review and comment. A notice of availability of the RSA-011 RI report, the

SB/PP, and other related documents in the Administrative Record file was published in The

Huntsville Times on July 15, 2007 and July 18, 2007; in the Speakin' Out News on July 18, 2007;

and in the Redstone Rocket on July 18, 2007. A 30-day public comment period for the SB/PP

began on July 15, 2007. The SB/PP stated that a public meeting would be held if there was

sufficient interest from the public. A meeting was not requested and the public comment period

ended on August 13, 2007. No comments were received during the public comment period.

2.4 Scope and Role of Operable Unit or Response Action

2.4.1 Overall Remedial Strategy for Redstone Arsenal and RSA-011

Redstone Arsenal was originally divided up into 18 OUs for the purpose of facilitating groupings

for remediation and site closeout under CERCLA. These OUs were determined primarily from

topographic/watershed and ecological habitat/range standpoints. Two additional OUs (OU-19

and OU-20) were added to complete the assignment of all of Redstone Arsenal land to OUs.

Recognizing that groundwater flow, however, is not limited to these OU boundaries, the Army

has more recently divided Redstone Arsenal into 13 sub-watersheds based on groundwater

watershed boundaries from the basewide hydrogeologic study conducted in 2001 (IT

Corporation, 2003a). Using a watershed approach, each of the 13 sub-watersheds has been

designated as a groundwater site (RSA-145 through RSA-157).

The Selected Remedy in this ROD is for surface media at RSA-011, which include the surface

soil, subsurface soil, and soil vapor located within the site boundary. Surface media do not

include groundwater under the site, which is being investigated as part of the larger RSA-146

groundwater site. The groundwater contamination under RSA-011, like many of the CERCLA

sites at Redstone Arsenal, encompasses contributions from more than one surface media site in

the area. The final remedy for the RSA-146 groundwater site will be selected after completion

of an Rl/feasibility study, and any actions to address groundwater located under RSA-011 would

be included as part of this RSA-146 remedy.

There is no need for a response action for surface media at RSA-011, because there are no

unacceptable risks to human health or the environment. No ongoing sources of groundwater

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contamination are present in surface soils or vadose zone subsurface soils. If the surface media

had been sourcing to groundwater at RSA-011, the objective of the remedial action would have

been to contain, reduce, or eliminate existing sources prior to selecting final remedies for

groundwater.

A site access control (SAC) program is currently in place to control access to the CERCLA sites

at Redstone Arsenal to prevent inadvertent exposure to contamination in the interim until

remediation, as required, is accomplished (Army, 2006a). Controls through the SAC program

for groundwater include prevention of installation of wells for drinking water, industrial

purposes, or agricultural processes on Redstone Arsenal. This restriction prevents exposure of

any person to groundwater contamination until final remedies are selected for the groundwater

sites. Additionally, a PP (Shaw, 2007c) was finalized, and an interim record of decision (IROD)

is in preparation by the Army for installation-wide groundwater at Redstone Arsenal. These

decision documents contain land-use controls as an interim remedy to prevent potable water use

and provide management control over nonpotable water uses of groundwater beneath Redstone

Arsenal. The finalized IROD wil l support the No Action remedy for surface media at RSA-011

by controlling the groundwater use under RSA-011 until a final remedy has been selected in the

RSA-146 groundwater ROD.

2.4.2 Scope of Problems Addressed by RSA-011 Response Action

The action or scope covered by the response action at RSA-Ol I consists of the surface media,

which include the surface soil, subsurface soil, and soil vapor. There is no surface water or

sediment within the site boundary. No problems have been identified in soils or in soil vapor at

RSA-Ol I that require remedial action under present and planned future industrial land uses or

under hypothetical future residential uses. The remedial action for RSA-Ol I surface media isintended as the final remedial action.

2.4.3 Relationship of Proposed Action to Removal or Other Operable Units

Several CERCLA and RCRA sites are located east-southeast of RSA-Ol I in OU-IO (Figure 2).

Commingled perchlorate and TCE contaminant plumes are present in groundwater under much

of OU-10, including RSA-0II. The RI report for RSA-011 concluded that the site may

historically have been a source of perchlorate contamination to groundwater, namely the sludge

drying beds (Shaw, 2007a). However, the TCE and at least some of the perchlorate appear to be

related to sources outside of the RSA-011 boundary. These surface media sources are currently

being investigated under a separate scope. Groundwater under RSA-011 and the rest of OU-10

will be investigated as part of the groundwater site RI effort for RSA-146.

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2.5 Site Characteristics

RSA-011 is located in a very industrialized portion of Redstone Arsenal. The site is adjacent to

and northwest of several other environmental sites that were involved in former degreasing

operations using TCE or in propellant grinding, mixing, and fil l ing operations (Figure 2). The

eastern boundary of Redstone Arsenal is approximately 1 mile east of RSA-011. The site is

located on approximately 3 acres and is enclosed by a security fence with a gated entrance.

Access to the site is via Sparrow Road from the southeast. Several of the inactive treatment plant

structures are located atop raised soil mounds at the site that look to have been engineered for the

treatment plant.

The site is grass covered and is on a very gentle topographic rise bounded by a low, wooded

wetland to the west and north and a grassy, gently sloping depression to the east. The inactive

treatment structures remain in place at RSA-011, but the wastes were removed from the

clarifiers, sludge drying beds, and other structures during the deactivation of the plant in 1992.

Figure 3 shows site photographs of the inactive structures at RSA-011. The Army plans to

demolish the current inactive structures at the site, but the action will be conducted outside of

this ROD.

The lift station at Building 7907 currently moves incoming waste to an active treatment plant on

Buxton Road, located south of RSA-011. Up to several times a day, Redstone Arsenal workers

may enter the lift station pit to check the system operation. This station is monitored for natural

sewer gases, and the workers spend minimal time in the station.

The site has no permanent surface water or aquatic habitats within the site boundary. Local

topography controls the surface runoff from the site. There are no observed surface drainage

features within the site boundary. The nearest surface water feature to RSA-011 is a small creek

that lies approximately 400 feet west of the site boundary and flows to the north within the

swampy wetland area. Hunting is not currently permitted at the fenced RSA-011 site, but

hunting is permitted just north of the site.

The significant findings of the RI with respect to known or suspected sources of contamination,

types of contamination, and affected media are summarized in the following sections.

2.5.1 Conceptual Site Model

A conceptual site model (CSM) is a three-dimensional "picture" of site conditions that illustrates

contaminant sources, release mechanisms, exposure pathways, migration routes, and potential

human and ecological receptors. The CSM presented on Figure 4 shows the geologic and

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hydrogeologic setting of RSA-011. The CSM shows these areas relative to major surface and

subsurface features at or near the site. To complete the CSM for RSA-011, a conceptual site

exposure model is presented on Figure 5. Figure 5 illustrates the potential migration routes,

exposure routes, and human and ecological receptors present at RSA-011.

The main components of the CSM presented on Figure 4 include the following:

• The site originated from the processing and disposal of sewage treatment sludgefrom the 1940s unt i l 1992. The wastes were released to surface sludge dryingbeds. The wastes included VOCs, metals, and perchlorate. The total volume ofwaste treated is unknown.

• No principal threat source material or low-level threat waste is present at RSA-011.

• Minor contamination (metals and perchlorate) is present in soil around thetreatment structures and disposal features at the site. No chemicals of concern(COC) were identified in soil.

• Elevated levels of VOCs (primarily TCE) and perchlorate are present in thegroundwater, largely due to the migration of contaminant plumes from nearbyCERCLAsitesinOU-10.

• There are no surface water features or aquatic habitats within the site boundaries,although there are wetlands directly west and north of the site.

• Depth to groundwater at RSA-011 can be very shallow, ranging from about 2 toabout 14 feet below ground surface (bgs). The groundwater flow is predominantlyto the north-northwest in the vicinity of the site, although flow appears to be radialfrom the higher topographic areas within the site where the treatment plantfeatures are located. The shallowest water table occurs near the perimeter of thesite, where the lowest topography is present. Because of the nature of theprocesses (waste moving through treatment systems and disposal in sludge dryingbeds) at the treatment plant, contaminants have historically leaked to soil andleached to groundwater.

The conceptual site exposure model presented on Figure 5 documents current and future site

conditions and shows what is known about human and ecological exposure through contaminant

release and migration to potential receptors. The human health and ecological risk assessments

are based on this exposure model. Current and future potential human receptors are presented

below and include groundskeepers, construction workers, sportsmen, and trespassers, any of

which might, under specific circumstances, be exposed to site-related contamination.

Additionally, an on-site resident has been evaluated for a future scenario even though this

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scenario is unlikely. Evaluation of this residential receptor provides the basis for establishing

some remedial responses, including justification for the selection of land-use controls if required

by EPA.

• The site is currently maintained, with the groundskeeper serving as a conservativesurrogate for all site workers who might be exposed to surface soil. Thegroundskeeper, who maintains the fencing and cuts the grass, could be exposed tosoil through incidental dermal contact, inhalation of dust, and incidental ingestion.The soil at the site is covered by grass such that there would be minimal directexposure to soils.

• A construction worker was included as a plausible receptor for evaluatingsubsurface soil.

• A trespasser was included as a plausible receptor to evaluate recurring exposure ofa youthful, unauthorized entrant to the surface soil at the site.

• Hunting is currently restricted at the site, although it could be allowed at RSA-011in the future. In addition, the site is adjacent to land that is used for hunting and,thus, could support deer that could be consumed by current hunters. For thesereasons, a future sportsman was considered to be as a plausible receptor for thissite.

Most of RSA-011 is currently covered with grass. There are no wetlands or aquatic habitat areas

present within RSA-011. As listed in Redstone Arsenal's Endangered Species Management

Plan (Army, 2005), no threatened or endangered species or special status species are present at

RSA-011. Ecological receptors may be exposed to contaminants present in surface soil at this

site or to contaminants that have been accumulated in site vegetation or soil invertebrates, or

been distributed further within the food web present at this site. No areas of archeological or

historical importance are present at RSA-011.

Potential groundwater exposure pathways are incomplete under current conditions because

groundwater is not utilized as a potable water supply on Redstone Arsenal (Army, 2006a; Shaw,

2007c). The site risks are discussed in Section 2.7.

2.5.2 Nature and Extent of ContaminationSurface soil, subsurface soil, soil vapor, and groundwater sampling at RSA-011 in and around

the treatment structures and disposal sludge beds began in the early 1990s and concluded by

2007. Figure 6 shows the sample locations from the various investigations conducted at the site.

The site inspection report (SA1C, 1996) and RI report (Shaw, 2007a) contain the detailed sample

information, analytical data, and maps for all the investigations conducted at the site.

KN7\RSA\RSA-OI I\ROD\D-F\OI l-DF-ROD.doc\8/!4/2007\9:53:38 AM 2-9

2.5.2.1 Nature and Extent of Soil Contamination

Soil. Concentrations in surface and subsurface soils of several metals, including arsenic,

vanadium, iron, and aluminum, were shown to be background related in weight-of-evidence

evaluations performed using cross plots of trace metals to major metals (Shaw, 2007a; IT

Corporation, 2003b).

Perchlorate was detected in a very small percentage (9.8 percent) of the 92 surface and

subsurface soil samples analyzed for perchlorate. The maximum concentration detected was

only 0.044 J mg/kg. Only 6.5 percent of the samples had concentrations exceeding the DAF4

SSL. These exceedances occurred at widely spaced locations separated by locations where

perchlorate was either not detected or detected at concentrations less than the DAF4 SSL. The

average of all detected concentrations of perchlorate at RSA-Ol I (0.022 mg/kg) was found to be

almost identical to the 0.021 mg/kg DAF4 SSL. No significant perchlorate mass remains in any

location on RSA-Ol I, and residual concentrations do not pose a threat of continued leaching to

groundwater at RSA-Ol I.

Surface Soil. Surface soil samples were collected in and around the treatment structures and

disposal features at RSA-Ol I and analyzed for a number of constituents, including VOCs,

semivolatile organic compounds (SVOC), pesticides/polychlorinated biphenyls (PCB), metals,

perchlorate, and cyanide. Table 2 presents a summary of the surface soil data for lead, mercury,

and perchlorate. Most metals were within the range of background, but mercury and lead are

believed to be site-related contaminants present near a few of the treatment plant structures,

probably representing spills or leaks. The samples collected from the two sludge drying beds did

not exhibit elevated levels of any metals; however, this was probably because the metals are

fairly immobile and the sludge was periodically removed. Perchlorate was detected only at low

estimated concentrations in the northernmost sludge drying bed. Several pesticides were

detected in and around the sludge drying beds, likely the result of past legal use of the chemicals

to suppress pests. A PCB, Aroclor 1254, was detected in two surface soil samples, one just north

of the trickling filter at Building 7906 and the other south of the northernmost sludge drying bed

near the fenceline (SS08 and SSIO) (Figures 2 and 6). Efforts to delineate the extent of this

contamination resulted in no further detections of PCBs in surface or subsurface soil at RSA-

Ol I. No site-related chemicals detected in surface soil, including metals, perchlorate, pesticides,

and PCBs, were found to pose ongoing concerns for leaching to groundwater.

KN7\RSA\RSA-OI l\ROD\D-F\Ol l-DF-ROD.doc\8/!4/2007\9:53:38 AM 2-10

Subsurface Soil. Subsurface soil samples were collected in and around the treatment

structures and disposal features at RSA-011 and analyzed for a number of constituents, including

VOCs, SVOCs, pesticides/PCBs, metals, and perchlorate. Table 3 presents a summary of the

subsurface soil data for lead, mercury, and perchlorate. Minor subsurface soil contamination was

detected, including trace levels of VOCs, perchlorate, and metals. The VOC detections,

including TCE, were sporadic across the site. TCE was detected at low estimated concentrations

to a depth of 9 feet bgs in soil in a few locations under the site. Perchlorate was detected beneath

Sludge Drying Bed 7912 for Unit IB and adjacent to the influent line that carried untreated

wastes to the treatment plant (just south of the pump station and southwest of Sludge Drying Bed

7915). Perchlorate was detected in only 4 (SB07, SB08, SB23, and SB34) of 44 subsurface soil

samples analyzed for perchlorate, 3 of which slightly exceeded the DAF4 SSL (Figure 6). Three

detected values occurred at 4 to 6 feet bgs and the fourth detected value occurred at 7 to 9 feet

bgs. Numerous samples with nondetect results for perchlorate were interspersed among the three

sample locations with concentrations slightly above the DAF4 SSL. Metals, including lead and

mercury, were detected in subsurface soil but were found to be either less than the background

screening value or the industrial preliminary remediation goal. Low concentrations of pesticides

were also detected in subsurface soil at RSA-011. The pesticides were found primarily at the

sludge drying beds and at other treatment plant structures, consistent with past legal spraying to

suppress pests. No site-related chemicals detected in subsurface soil, including VOCs,

perchlorate, pesticides, and metals, were found to pose ongoing concerns for leaching to

groundwater.

So/7 Vapor. Vapor trapped in the soil at RSA-011 was sampled at two on-site locations at 5.5

feet bgs in April 2007. Very low concentrations of VOCs were detected. Table 4 presents a

summary of soil vapor data for TCE. These data were used in vapor intrusion modeling to

develop indoor air concentrations for the three existing site structures and for a hypothetical

future residential house (Shaw, 2007a).

2.5.2.2 Nature and Extent of Groundwater Contamination

Groundwater was investigated at RSA-011 to delineate the lateral and vertical nature and extent

of local groundwater contamination and to assess whether or not site soils are contributing to that

contamination. Elevated levels of perchlorate, TCE, and other VOCs were detected in the

overburden groundwater and are from historical releases from either RSA-011 or other nearby

sources. Perchlorate concentrations exceeded the EPA drinking water equivalency level (24.5

micrograms per liter [ug/L]) used to determine a safe level for drinking water. TCE

concentrations exceeded the federal maximum contaminant level of 5 (ig/L for safe drinking

water. Table 5 presents a summary of the groundwater data for TCE and perchlorate. Mapped

KN7\RSA\RSA-OI I\ROD\D-F\OI l-DF-RODdoc\8/!4/2007\9:53:38 AM 2-11

groundwater plumes for the greater OU-10 area indicate adjacent sources of TCE and perchlorate

groundwater contamination and commingled plumes. Some portion of these plumes extends

beneath the RSA-011 site, following overall flow paths to the northwest toward Huntsville

Spring Branch. However, from the soil profiling conducted at RSA-011, it appears that releases

of perchlorate to groundwater occurred historically at the site. Concentrations of TCE,

perchlorate, and other contaminants remaining in soil at RSA-011 are not principal threat waste

or source material and do not pose ongoing concerns for leaching to groundwater. Further

investigation of the groundwater contamination wil l be conducted during the RSA-146

groundwater Rl.

2.5.2.3 Fate and Transport

Formation of leachate and vertical transport in soils to groundwater is the only viable or active

transport mechanism at RSA-011. Most contaminants are present in soil at concentrations that

would be naturally occurring and for which the DAF4 SSL is not exceeded. As discussed in

Section 2.5.2.1, perchlorate remaining in surface media does not pose a threat of continued

leaching to groundwater at RSA-011.

Three mercury subsurface samples exceeded the DAF4 SSL (Table 3), but mercury is not

expected to impact groundwater under current conditions. Migration of this metal is driven by

the natural infiltration rate, which is calculated at nearly 4,000 years for mercury, and thus,

mercury is nearly immobile in soil at RSA-011 (Shaw, 2007a).

2.6 Current and Potential Future Land and Resources Use

This section describes current and future use of land, groundwater, and surface water at RSA-

011.

2.6.1 Current and Future Land Use

Current Land Use. The current land use is classified as industrial for manufacturing and

production (Army, 2006b). The immediate area of RSA-011 is grass covered, with inactive

treatment structures still present. The site area is fenced, locked, and inactive except for the lift

station, which is still in use. Immediately to the north and west are wetlands, and to the east are

facilities used in various industrial operations in the RARE North Plant (Figure 2).

No recreational activities (e.g., hunting, fishing, camping, hiking) are currently permitted at

RSA-Ol I, which is fenced, with a locked gate to control access. However, the land immediately

north of RSA-Ol I is permitted for hunting. Recreational hunters are authorized to enter

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Redstone Arsenal through staffed security gates at the facility boundaries. Individuals accessing

Redstone Arsenal for any recreational purposes are directed to the outdoor recreation office for

maps. These maps identify all approved hunting areas as well as other recreational areas.

Prohibited areas such as CERCLA sites (i.e., RSA-011) are noted on the maps. Game wardens

and other security personnel routinely enforce the recreational use regulations on Redstone

Arsenal. Where practical, the Army restricts entry into environmental sites by fencing them

(such as at RSA-011) and/or by placing warning signs at key entry points per the SAC program

(Army, 2006a).

Future Land Use. Future land use in the area of RSA-011 is planned as research,

development, testing, and evaluation (Army, 2006b). The Army plans to demolish the current

buildings/structures at the site except for the l i f t station. This demolition work will be performed

as part of base operations and maintenance and is not related to this ROD. It is anticipated that

the land use to the east of RSA-011 will remain industrial into the foreseeable future. The

wetland areas to the west and north of the site are anticipated to remain as open space. Although

future land use of this site for hunting or recreation activities is possible, no residential or day

care facilities are planned or anticipated for RSA-011 in the future.

2.6.2 Groundwater Use

Current Groundwater Use. The groundwater is not used for human consumption within

RSA-011, OU-10, or Redstone Arsenal as a whole. The SAC program (Army, 2006a) requires

that all well requests on Redstone Arsenal be reviewed, and installation of wells for drinking

water, industrial purposes, or agricultural processes are prohibited. The Tennessee River is the

source of potable water on Redstone Arsenal, so groundwater is not currently a source of

drinking water or used locally for industrial purposes.

Future Groundwater Use. It is not anticipated that groundwater resources at RSA-011 or

elsewhere on Redstone Arsenal will be developed in the future, and the Army is unlikely to

change the current mission of Redstone Arsenal. However, in the unlikely event that a change in

the Army mission could prompt the need for the groundwater resources under Redstone Arsenal,

a PP has been finalized (Shaw, 2007c) and an IROD is being developed for installation-wide

groundwater to control/manage its use. The IROD is a legal document that will prevent use of

the installation's groundwater as a potable water source and will manage nonpotable

groundwater withdrawals for other purposes until remedies are selected in the final RODs for the

various groundwater sites within Redstone Arsenal.

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2.6.3 Surface Water Use

Surface water is not present at RSA-011.

2.7 Site Risks

A baseline human health risk assessment (BHHRA) and screening-level ecological risk

assessment (SLERA) were performed to estimate the probability and magnitude of potential

adverse human health and environmental effects from exposure to contaminants associated with

RSA-011, assuming no remedial action was taken (Shaw, 2007a). These risk assessments

provide the basis for taking an action at RSA-011 or support the need for No Action at this site.

A summary of the aspects of the BHHRA which support the determination that no remedial

action is necessary to ensure the protection of human health and the environment is presented

below, followed by a summary of the SLERA. The complete BHHRA and SLERA can be found

in Appendices G and H, respectively, of the final RI report for RSA-011 (Shaw, 2007a).

2.7.1 Baseline Human Health Risk Assessment

The BHHRA did not identify unacceptable risks from surface media at RSA-011. To reach this

conclusion, the BHHRA followed a four step process: I) hazard identification which identified

those hazardous substances which, given the specifics of the site, were of significant concern; 2)

exposure assessment which identified actual or potential exposure pathways, characterized the

potentially exposed populations, and determined the extent of possible exposure; 3) toxicity

assessment which considered the types and magnitude of adverse health effects associated with

exposure to hazardous substances, and 4) risk characterization and uncertainty analysis which

integrated the three previous steps to estimate the potential and actual risks posed by hazardous

substances at the site, including carcinogenic and noncarcinogenic risks and a discussion of the

uncertainty in the risk estimates.

A summary of these steps of the human health risk assessment is presented below.

2.7.1.1 Identification of Chemicals of Potential Concern

Of the more than 70 chemicals detected at the site, 23 were selected for evaluation in the

BHHRA as chemicals of potential concern (COPC). The COPCs were selected to represent

potential site-related hazards based on toxicity, concentration, frequency of detection, and

mobility and persistence in the environment. COPCs for surface soil, subsurface soil, total soil,

and groundwater can be found in Tables G-2 through G-5, respectively, of the BHHRA

presented in the final RI report for RSA-Ol I (Shaw, 2007a). Estimates of the exposure point

concentrations used for all COPCs can be found in Appendix G, Table G-6 of the final RI report

KN7\RSA\RSA-OI I\ROD\D-F\OI I-DF-ROD doc\8/!4/2007\9:53:38 AM 2-14

for RSA-011 (Shaw, 2007a). Only TCE was identified as a COPC in soil vapor, as presented in

Attachment 2 of Appendix G of the BHHRA (Shaw, 2007a).

2.7.1.2 Exposure Assessment

Potential human health effects associated with exposure to COPCs were estimated quantitatively

through the development of several hypothetical receptor scenarios and exposure pathways.

These pathways were developed to reflect the potential for receptor exposure to hazardous

substances based on the present site uses, potential future site uses, and location of RSA-Ol I.

The current and expected future land use at RSA-Ol I is industrial; however, there is no current

administrative control prohibiting site development for residential purposes in the future.

Therefore, risks to a hypothetical residential receptor were evaluated which provides a basis for

cost comparisons between cleanup options that would allow for unrestricted site use versus other

cleanup options where life cycle costs for maintaining land-use controls would be incurred.

The following is a brief summary of the exposure pathways evaluated in the BHHRA. A more

thorough description of exposure pathways evaluated can be found in Appendix G, Section G4.0

of the final RI report for RSA-Ol I (Shaw, 2007a).

Five human receptors were quantitatively evaluated in the exposure assessment. The

groundskeeper and construction worker are considered industrial receptors; these receptors were

evaluated under current and future land-use assumptions. The sportsman and trespasser are

termed recreational receptors and the sportsman is considered to be a future receptor only,

because hunting is not presently allowed at the site and the site is currently fully fenced. A

hypothetical residential receptor was evaluated under a potential future site use which assumes

that houses are built on RSA-Ol I.

Receptors could potentially come in contact with contaminants in site media by dermally

contacting, ingesting, or inhaling site media. For exposure to soils, all three exposure routes

were evaluated for the construction worker. The groundskeeper, sportsman, and trespasser

receptors were evaluated for exposure to soils through ingestion and dermal contact and for

inhalation of chromium. The sportsman is assumed to consume venison from deer that have

browsed on potentially contaminated soil as well. Hypothetical future residential adults and

children were assumed to only come in contact with soils through ingestion and dermal contact

because in a residential setting, soils would be covered by lawns, gardens, or pavement, reducing

dust emissions from wind erosion to insignificant levels. For exposure to groundwater, the

future groundskeeper, construction worker, and hypothetical future resident were assumed to

KN7\RSA\RSA-OI I\ROD\D-F\OI l-DF-ROD.doc\8/H/2007\9:53:38 AM 2- I 5

contact contaminants through ingestion and dermal contact. In addition, an adult hypothetical

future resident may inhale VOCs in groundwater while showering.

A hypothetical future indoor commercial worker was evaluated for exposure to soil vapors which

might have accumulated inside the three existing onsite structures. There are no indoor workers

using these structures currently. In addition, a hypothetical resident was evaluated for exposure

to soil vapors which may intrude into a hypothetical future residential building.

TCE was identified as a COPC in soil vapor. To determine the exposure point concentration

used to evaluate the vapor intrusion migration exposure pathway, indoor air concentrations were

calculated based on soil gas samples collected from two locations above the highest groundwater

concentrations found on site. The Johnson and Ettinger vapor intrusion model was used to

calculate indoor air concentrations based on soil gas sample results for TCE (Johnson and

Ettinger, 1991). Indoor air concentrations of TCE were calculated for the three existing on-site

structures and for a hypothetical future residential on-site house.

For TCE in soil vapors which have been transported into indoor air, future indoor commercial

workers and a future hypothetical residential receptor were evaluated based on inhalation

exposure. Attachment 2 to Appendix G of the final RI report for RSA-011 (Shaw, 2007a)

presents the exposure assessment performed for the vapor intrusion evaluation.

2.7.1.3 Toxicity Assessment

The possible harmful effects to humans from the COPCs were evaluated. These chemicals were

separated into two groups: carcinogens (COPCs that may cause cancer) and noncarcinogens

(COPCs that may cause adverse health effects other than cancer). Chemicals that are considered

to be carcinogens may cause noncancer adverse health effects as well. Both cancer and

noncancer adverse health effects were evaluated for carcinogens, where applicable. Toxicity

values used for quantitative evaluation of risks via the oral, dermal, and inhalation pathways are

discussed in Appendix G, Section G5.0, and presented in Tables G-7, G-9, and G-IO of the final

RI report for RSA-Ol I (Shaw, 2007a).

Cancer potency factors have been developed by EPA from epidemiological or animal studies to

reflect a conservative "upper bound" of the risk posed by potentially carcinogenic compounds.

Reference doses (RfD) for noncarcinogen compounds have been developed by EPA and they

represent a level to which an individual may be exposed that is not expected to result in any

deleterious effect. RfDs are derived from epidemiological or animal studies and incorporate

uncertainty factors to help ensure that adverse health effects wil l not occur.

KN7\RSA\RSA-01 I\ROD\D-TO1 l-DF-ROD.doc\8/U/2007\9:53:38 AM 2-16

There is ongoing uncertainty in the regulatory community over the most scientifically valid

inhalation slope factor to use for estimating risks from inhalation TCE vapors. Inhalation slope

factors for TCE used in the vapor intrusion evaluation were based on two different sources.

These sources included EPA's National Center for Environmental Assessment evaluation of

TCE (EPA, 2001) and the California Environmental Protection Agency's guidelines for

describing cancer potency factors (California Environmental Protection Agency, 2002).

Attachment 2 of Appendix G of the final RI report for RSA-011 (Shaw, 2007a) presents the

toxicity assessment performed for the vapor intrusion evaluation.

2.7.1.4 Risk Characterization

The results from the exposure and toxicity assessment were combined to calculate the overall

risks from exposure to site COPCs. Excess lifetime cancer risks were determined for each

exposure pathway by mult iplying a daily intake level with the chemical-specific cancer potency

factor.

For potential carcinogens, the risk to human health is expressed in terms of the probability of the

chemical causing cancer over an estimated lifetime of 70 years. All risks estimated represent an

"excess lifetime cancer risk" or the additional cancer risk on top of that which occurs from other

causes. EPA's risk management range for carcinogens is I x IO"4 to I x IO"6 (between a I -in-

10,000 and a 1-in-1,000,000 chance of developing cancer as a result of site-related exposure). In

other words, if exposure to a particular carcinogenic chemical creates a l-in-100,000 chance of

causing cancer, then this would be expressed as 1 x 10"5. In general, calculated risks greater than

1 x 10"4 require consideration of engineering-oriented cleanup alternatives. Cancer risks between

1 x 10"4 and 1 x 10"6 (between 1-in-10,000 and 1-in-1,000,000) fall within a risk management

range that Redstone Arsenal risk managers may decide is acceptable on a case-by-case basis.

For noncarcinogens, the risk to human health is expressed as a hazard quotient (HQ) for each

exposure pathway. The HQ is calculated by dividing the daily intake level by the appropriate

exposure pathway RfD (e.g., oral RfD for ingestion pathway). The hazard index (HI) is the sum

of all the HQs for all COPCs that affect the same target organ (e.g., liver) within or across those

media to which the same individual may reasonably be exposed. An HI greater than 1 suggests

that adverse health effects are possible.

Where cumulative risks have been found to exceed designated risk thresholds, chemicals with

risks exceeding Ix 10'6 (or an excess lifetime cancer risk of l-in-1,000,000) or an HI of 0.1 may

be selected as COCs. These are chemicals that significantly contribute to unacceptable risks for

KN7\RSA\RSA-OI I\ROD\D-FM)I I-DF-ROD doc\8/l4/2007\9:53:38 AM 2-17

a pathway in an exposure model for a hypothetical receptor (e.g., a child that resides on the site).

Typically, these selected chemicals represent chemicals which may require a response action.

However, risk managers may refine the list of COCs selected for action based on site-specific

considerations.

Risks presented in the RI report (Shaw, 2007a) from exposure to each medium and cumulative

risk for each receptor are shown in Table 6. Following the quantitative calculation of risk during

the evaluation of problems potentially warranting action, the metals aluminum, arsenic, and

vanadium, which were evaluated as COPCs, were determined to be present at concentrations

within the range of naturally occurring background. Therefore, to identify COCs, cumulative

risk results for each receptor were calculated after the risk estimates associated with background-

related metals were excluded from the overall risk estimates. These results are presented in

Table 7. As shown in Table 7, when the risk estimates from the background-related metals were

excluded from the quantitative analysis of total risk, no receptors were found to have

unacceptable risks from exposure to surface soil, subsurface soil, or total soil. As a result, no

COCs were identified for surface soil, subsurface soil, or total soil.

The risks to a groundskeeper and future hypothetical residential receptor from exposure to

groundwater were found to exceed 1 x 10~4 (or a excess lifetime cancer risk of 1-in-10,000) in the

BHHRA. Noncancer His exceeded 1 for exposure to groundwater by the groundskeeper,

construction worker, and hypothetical residential receptor. However, RSA-011 is considered to

be a surface media site, and potential risks from exposure to groundwater from this site wil l be

addressed in the groundwater site RSA-146. In the interim, an installation-wide PP has been

finalized (Shaw, 2007c) and an IROD is being developed for groundwater to prevent use of the

installation's groundwater as a potable water source and to manage nonpotable groundwater

withdrawals until final remedies for the groundwater sites are selected.

Results of the vapor intrusion evaluation are presented in Table 8. Risks from TCE present in

soil gas that might migrate into indoor air and come in contact with a hypothetical future

residential receptor or future indoor commercial worker receptors working in the existing site

structures were assessed. As shown in Table 8, risks from exposure to modeled concentrations

of TCE in indoor air did not exceed 1 x 10"6 (1-in-1,000,000) for any receptor regardless of

which of the two possible inhalation slope factors for TCE were used.

2.7.7.5 Summary of the Baseline Human Health Risk Assessment

No contaminants in surface soil, subsurface soil, and total soil have been identified as COCs

warranting action based on the results of the BHHRA. Chemicals (primarily TCE and

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perchlorate) in groundwater pose a substantial human health threat if ingested, but these

chemicals are being addressed during the RSA-146 groundwater site investigation. Risks to a

current or future indoor commercial worker receptor and a hypothetical future residential

receptor from the vapor intrusion pathway did not exceed acceptable levels. No COCs were

selected for RSA-011 based on the results of the BHRRA.

2.7.2 Screening-Level Ecological Risk Assessment

The SLERA conducted for RSA-011 did not identify any contaminants in surface soil warranting

action for ecological receptors. To reach this conclusion, the SLERA for RSA-011 was

completed in three steps, which are discussed below.

Step 1 - Screening-Level Problem Formulation and Toxicity Assessment. Theprimary objective of the ecological risk assessment is to evaluate whether individuals of species

designated as having a special administrative status or populations of non-special-status species

are potentially at risk when exposed to site-related chemicals at RSA-Ol I. The ecological

receptors evaluated for this assessment included the following:

• Terrestrial plant and soil invertebrate communities

• Populations of mammals and birds which feed on soil invertebrates, plants, andother animals.

No special-status species were found to exist at this site. Similar to the BHHRA, chemicals

found in site soils at concentrations above federal and state risk screening levels as well as

background screening levels for metals were identified as chemicals of potential ecological

concern (COPEC).

Step 2 - Screening-Level Exposure Estimate and Risk Calculation. Chemicals

initially selected as COPECs included several metals, cyanide, perchlorate, PCBs, two VOCs,

several SVOCs, and several pesticides. Table H-3 of Appendix H of the RI report for RSA-Ol I

(Shaw, 2007a) presents the results of the selection of COPECs.

Step 3 - Problem Formulation Refinement. Further evaluations were performed during

the problem formulation refinement step to determine whether adverse impacts to populations of

non-special-status species present at this site would be anticipated. This step consisted of three

parts: an assessment of exposure, toxicity, and risk characterization. The exposure assessment

was based on measured concentrations of COPECs in site surface soils. These concentrations

were used directly to assess whether literature-derived toxicity threshold concentrations of

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chemicals in soil were exceeded for plants and soil invertebrates. Food-chain dose calculations

were performed using appropriate bioaccumulation factors for birds and mammals. Metals that

did not exceed background screening concentrations were excluded from these analyses.

Toxicity endpoints were literature-based soil concentrations found to impact plant and soil

invertebrates, or for food-chain receptors, doses of chemicals on a per-body mass basis. Toxicity

reference values used in the SLERA were based on studies where both no observable adverse

effects levels and lowest observable adverse effects levels were determined. The risk

characterization was performed by calculating an HQ. The HQ is defined as the exposure (either

soil concentration or dose) divided by the toxicity endpoint concentration. If the HQ is greater

than 1.0, there is a potential that a particular receptor may experience an adverse health effect.

Table H-17 in Appendix H of the RJ report for RSA-011 presents the results of the comparison

to literature-based toxicity values for plants/soil invertebrates, while Table H-20 presents the

summary of HQs for food chain receptors (Shaw, 2007a). These results are summarized and

presented in Table 9.

Based on the analysis of the presence of the potential for adverse effects to ecological receptors

presented in the SLERA, no chemicals were identified as COCs for populations of non-special-

status species that use this site.

2.7.3 Risk Summary

No contaminants in surface soil, subsurface soil, total soil, or soil vapor have been identified as

COCs or COPECs warranting action based on the results of the conservative exposure scenarios

in the BHHRA and SLERA, respectively. Chemicals (primarily TCE and perchlorate) in

groundwater pose a substantial human health threat if ingested, but risks from chemicals present

in groundwater will be addressed as part of the RSA-146 groundwater site.

It is the Army's current judgment that no remedial action is necessary at this site to ensure

protection of public health or welfare or the environment from actual or threatened releases of

hazardous substances into the environment.

2.7.4 Basis for Action

A No Action remedy has been selected for RSA-011 surface media. The characterization that

was performed at this site supports this selection (see Section 2.5 for site characteristics). Based

on the results of the fate and transport analysis, no chemicals detected on site were found to pose

a leaching threat to groundwater (see Section 2.5.2.3 for fate and transport). This ROD

documents that RSA-011 surface media do not pose unacceptable risks to human health or the

environment under current or future industrial or future unrestricted exposure scenarios (see

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Section 2.7 for site risks). Current guidelines from EPA and ADEM state that "unrestricted use,"

including residential land use, must be considered in a No Action decision. The risk assessments

performed for RSA-011 support the finding that surface media at RSA-011 are available for

unrestricted use.

There have been several rounds of sampling performed at this site for all media, and although

there is groundwater contamination beneath the site, it is part of a more widespread contaminant

plume from other sources. Additional investigation and remediation of the groundwater is

deferred to a larger groundwater site (RSA-146) (see Section 2.4 for scope and role of OU or

response action).

The selected alternative of No Action is protective of human health and the environment and

complies with applicable requirements, including requirements under CERCLA and corrective

action requirements under RCRA. It is the Army's current judgment that no remedial action is

necessary at this site to ensure protection of public health or welfare or the environment from

actual or threatened releases of hazardous substances into the environment.

2.8 Documentation of Significant Change

No significant change has been made to the Preferred Alternative presented in the SB/PP for

RSA-011 (Shaw, 2007b).

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3.0 Responsiveness Summary

The Responsiveness Summary serves three primary purposes. First, it provides the Army, EPA,

and ADEM with information about community concerns with the site and preferences about the

Preferred Alternative presented in the SB/PP (Shaw, 2007b). Second, it shows how the public 's

comments were factored into the decision-making process for selection of the final remedy.

Third, it provides a formal mechanism for the Army to respond to public comments.

This Responsiveness Summary documents the formal public comments received on the RSA-011

SB/PP (Shaw, 2007b) and the Army's responses to the comments. However, no comments were

submitted during the 30-day public comment period that began on July 15, 2007 and ended on

August 13,2007.

No Action, which was presented as the Preferred Alternative in the SB/PP (Shaw, 2007b), is the

Selected Remedy for RSA-011 surface media. This decision is based on the Administrative

Record file for RSA-011, including the RI report, the SB/PP, and other related documents

contained in the file for this site, as well as on the fact that no public comments were received on

the Preferred Alternative during the public comment period. EPA and ADEM have expressed

concurrence with the Selected Remedy.

KN7\RSA\RSA-OI 1 \ROD\D-FMJ11-DF-ROD doc\8/l4/2007\9:53:38 AM 3-1

4.0 References

A.T. Kearney, 1989, Interim RCRA Facility Assessment of the RSA, Huntsville, Alabama,prepared for the U.S. Environmental Protection Agency, September.

California Environmental Protection Agency, 20Q2,Air Toxics Hot Spot Program RiskAssessment Guidelines. Part II. Technical Support for Describing Available Cancer PotencyFactors, December.

Geraghty & Miller, Inc., 1991, Final Identification and Evaluation of Potential Solid WasteManagement Units and Areas of Concern, prepared for the U.S. Army Corps of Engineers,February.

IT Corporation, 2003a, Final Sitewide Karst Hydrogeologic Investigation, Phase I Report ofFindings, Redstone Arsenal, Madison County, Alabama, Volumes 1 and 2, prepared for theU.S. Army Corps of Engineers, Savannah District, Savannah, Georgia, May.

IT Corporation, 2003b, Final Methodology for the Comparison of Site and Background Data,Redstone Arsenal, Madison County, Alabama, prepared for the U.S. Army Corps of Engineers,Savannah District, November.

Johnson, P.C. and R. A. Ettinger, 1991, Heuristic Model for Predicting the Intrusion Rate ofContaminant Vapors in Buildings, Environ. Sci. Technol. 25: 1445-1452.

Science Applications International Corporation (SAIC), 1996, Site Inspection Report for theRedstone Arsenal Site Inspections Project, Solid Waste Management Units, RSA-8, -9, -11(Group Cl), RSA-45 (Group L8), andRSA-82 (Group LI4), Redstone Arsenal, Alabama,prepared for the U.S. Army Corps of Engineers, October.

Shaw Environmental, Inc. (Shaw), 2007a, Final Remedial Investigation, Baseline HumanHealth Risk Assessment, and Screening-Level Ecological Risk Assessment, RSA-011,Operable Unit 10, Former Sewage Treatment Plant No. 1, Redstone Arsenal, Madison County,Alabama, prepared for the U.S. Army Corps of Engineers, June.

Shaw Environmental, Inc. (Shaw), 2007b, Final Statement of Basis/Proposed Plan for SurfaceMedia at RSA-011, Former Sewage Treatment Plant No. 1, Operable Unit 10, RedstoneArsenal, Madison County, Alabama, Revision 0, prepared for the U.S. Army Corps ofEngineers, July.

Shaw Environmental, Inc. (Shaw), 2007c, Final Proposed Plan, Interim Remedial Action forInstallation-Wide Groundwater, Redstone Arsenal, Madison County, Alabama, Revision 0,prepared for the U.S. Army Corps of Engineers, July.

Shaw Environmental, Inc. (Shaw), 2006, Community Relations Plan, Redstone Arsenal,Madison County, Alabama, prepared for the U.S. Army Corps of Engineers, March.

KN7\RSA\RSA-011\ROD\D-F\011-DF-ROD doc\8/!4/2007\9:53:38 AM 4- 1

U.S. Army Garrison - Redstone (Army), 2006a, Redstone Arsenal Environmental Site AccessControl Program, June.

U.S. Army Garrison - Redstone (Army), 2006b, Real Property Master Plan Digest.

U.S. Army Garrison - Redstone (Army), 2005, Endangered Species Management Plan.

U.S. Environmental Protection Agency (EPA), 2001, Trichloroethylene Health RiskAssessment: Synthesis and Characterization (External Review Draft, Office of Research andDevelopment, National Center for Environmental Assessment (NCEA), Washington Office,Washington DC, EPA/600/P-01/002A.

KN7\RSA\RSA-OI I\ROD\D-F\OI l-DF-ROD.doc\8/14/2007\9:53:38 AM 4-2

TABLES

KN7\RSA\RSA-OI l\ROD\D-rai I-DF-ROD doc\8/!4/2007\9:53:38 AM

Table 1

History of Investigative ActivitiesRSA-011

Redstone Arsenal, Madison County, Alabama

Investigation/Dates

Initial Site InspectionsA. T. Kearney- 1988Geraghty & Miller, Inc. -1989Site Inspection(Science ApplicationsInternational Corporation)1996

Property Assessment /Environmental BaselineSurvey (CH2M Hill)1997Phase I Rl (IT Corporation)1997-1998

OU-10-Wide GroundwaterInvestigation (IT Corpora-tion/Shaw)2000-2001,2003

Phase II Rl (IT Corporation)2002

Supplemental Rl (Shaw)2004

Supplemental Sampling(Shaw) 2007

Media Sampled orActivity

None

Surface andSubsurface SoilGroundwater

Groundwater

Surface andSubsurface SoilGroundwater

Groundwater

Surface andSubsurface Soil

Surface andSubsurface SoilGroundwater

Soil Vapor

Description

Visual site inspections only, no samples werecollected. No visual evidence that contaminantshad been released to the environment.Drilled 4 borings, collecting a surface soil sample,one subsurface soil sample, and a groundwatergrab sample at each boring. The soils andgroundwater samples were analyzed for VOCsand metals.Installed and sampled 3 monitoring wells acrossthe soil/bedrock interface. Groundwater sampleswere analyzed for VOCs, SVOCs, PCBs,explosives, cyanide, and metals.Surface soils were sampled from 10 locations andsubsurface soil samples were collected from 4borings. Four permanent monitoring wells andone temporary well were,installed and sampledalong with 4 existing wells. All samples wereanalyzed for VOCs and metals; select sampleswere also analyzed for SVOCs, pesticides/PCBs,explosives, and cyanide.Select RSA-1 1 monitoring wells were sampled in2 separate rounds in 2000 - 2001 and analyzedfor VOCs and perchlorate (a select number ofsamples were also analyzed for metals). Fourgroundwater grab samples were collected usingdirect-push techniques and analyzed for VOCsand perchlorate. Additional sampling rounds wereconducted in 2003 with samples analyzed forVOCs and perchlorate.13 surface soil and 25 subsurface soil sampleswere collected and analyzed for VOCs, SVOCs,perchlorate, pesticides/PCBs, metals, explosives,and cyanide. No groundwater samples werecollected.45 surface and subsurface soil samples werecollected and analyzed for VOCs, perchlorate,metals, and pesticides/PCBs. Two groundwatergrab samples were analyzed for VOCs andperchlorate and 1 monitoring well was alsosampled for VOCs and perchlorate.Two vapor monitoring points were installed atRSA-01 1 and analyzed for VOCs.

PCB - Polychlorinated biphenyl.Shaw - Shaw Environmental, Inc.SVOC - Semivolatile organic compound.VOC - Volatile organic compound.

KN7\RSA\RSA-OI l\ROD\Final\Tabl.doc\8/l4/2007\9:52:04 AM

Table 2

Surface Soil Data SummaryRSA-011

Redstone Arsenal, Madison County, Alabama

Chemical

LeadMercuryPerchlorate

Units

mg/kg

mg/kgmg/kg

TotalSamplesAnalyzed

626248

Detections

Number ofDetections

62625

MinimumValue

14.2

0.0230.016 J

MaximumValue

44452.7

0.044 J

BackgroundScreening

Value

99.5

0.09NA

DAF4

SSL

NA0.4

0.021

Background Screening Value from IT Corporation, 20036.DAF4 SSL - Dilution attenuation factor 4, soil screening level (EPA, 1996). Not applicable if no DAF4SSL

available.mg/kg - Milligrams per kilogram.J - value is estimated.

KN7WSA\RSA-OU\ROD\Fmal\Tab2 5.doctt/l4/Z007\9:5l:24 AM

Table 3

Subsurface Soil Data SummaryRSA-011

Redstone Arsenal, Madison County, Alabama

Chemical

LeadMercury

Perchlorate

Units

mg/kgmg/kgmg/kg

TotalSamplesAnalyzed

484844

Detections

Number ofDetections

48484

MinimumValue

14.50.03

0.018

MaximumValue

2283.2

0.032

BackgroundScreening

Value

45.10.1NA

DAF<SSL

NA0.4

0.021

Background Screening Value from IT Corporation, 2003b.DAF< SSL - Dilution attenuation factor 4, soil screening level (EPA, 1996).mg/kg - Milligrams per kilogram.

KN7\RSA\RSA-OI l\ROD\Final\Tab2 5.doc\8/l4/2007\9:5 1:24 AM

Table 4

Soil Vapor Data SummaryRSA-011

Redstone Arsenal, Madison County, Alabama

Chemical

TCE

Units

ug/m3

TotalSamplesAnalyzed

3a

Detections

Number ofDetections

1 .

MinimumValue

ND

MaximumValue

2.47

ScreeningValue

0.22b

Includes one field duplicate sample.b At a risk level of 1 x 10"6 from the target shallow gas concentration on Table 2c (EPA, 2002)ND-Nondetect.ug/m3 - Micrograms per cubic meter.

KN7\RSA\RSA-01 l\ROD\Final\Tab2_5.doc\8/l4/2007\9:5l:24 AM

Table 5

Groundwater Data SummaryRSA-011

Redstone Arsenal, Madison County, Alabama

Chemical

Perchlorate8

TCE

Units

ua/Lug/L

TotalSamplesAnalysed

1835

Detections

Number ofDetections

1733

MinimumValue

0.450.17

MaximumValue

18001500

BackgroundScreening

Value

NANA

MCL

24.5b

5- Micrograms per liter.

MCL - Maximum Contaminant Level."EPA 314 Method was used for analysis of perchlorate. There is a possibility of false positives with this

method. The data have been validated and reported as is. Further evaluation will be conducted forperchlorate in groundwater with the RSA-146 remedial investigation.

bEPA drinking water equivalency level for perchlorate.

KN7\RSA\RSA-OI l\ROD\Final\Tab2_5.doc\8/!4/2007\9:5l:24 AM

Table 6

Total Cancer Risks and Noncancer HazardsforRSA-011 Receptors

Including Background-Related Metals1

Redstone Arsenal, Madison County, Alabama

Receptors

Current SiteUse3

Soil

Future Site Use"

Soil Groundwater Total Risk

CANCER RISK

Industrial Receptors:

Groundskeeper (Conventional) c

Groundskeeper (Alternative) d

Construction Worker (Conventional) c

Construction Worker (Alternative) "

Recreational Receptors:

Sportsman e

Trespasser °

Hypothetical Residential Receptors:

Resident (Conventional) c

Resident (Alternative) d

5.72 xlO"6

NE

LOOxlO.-6

NE

NE

3.22 x1Q-7

NE

NE

5.72 X10"6

5.98 xlQ-6

1.00X1Q-6

3.13 x1Q-6

8.03 x10'7

3.22 x10'7

3.10 x1Q-5

3.07 x10'5

4.10 xlO"1

4.10 xKT4

1.82x10'5

1.82x 10'5

NENE

1.37 xKT3

1.37 xKT3

4.16x10"

4.16x10"

1.92x1Q-5

2.14 x1Q- 5

8.03 x10'7

3.22 x10'7

1.40 xlO"3

1.40X10'3

NONCANCER HAZARDIndustrial Receptors:

Groundskeeper (Conventional) c

Groundskeeper (Alternative) d

Construction Worker (Conventional) c

Construction Worker (Alternative) "

Recreational Receptors:

Sportsman *

Trespasser e

Hypothetical Residential Receptors:

Resident, child (Conventional) c

Resident, child (Alternative) d

0.258

NE

0.674

NE

NE

0.036

NE

NE

0.258

0.2630.674

2.04

0.030

0.036

3.87

3.87

20.620.622.822.8

NE

NE

78.0

78.0

20.820.823.524.9

0.0300.036

81.8

81.8

NE - Not evaluated.Bold font entries represent cancer risk values that exceed the 1 x 10"4 to 1 x 10"* risk management range ornon-cancer hazard values that exceed the threshold level of 1 and are unacceptable.

1 Includes the cancer risks and noncancer hazards from the background-related metals aluminum, arsenic, andvanadium.

a Includes only exposure to soil.b Includes exposure to both soil and groundwater.c Conventional - Exposure to surface soil except for construction worker, where exposure is to surface soil and

subsurface soil.d Alternative - Total soils. Total soil hypothetically assumes surface and subsurface soil are mixed during future

development.e Includes only exposure to surface soil.

KN7\RSA\RSA-011 \ROD\Final\Tabs 6,7,8.9.doc\8/14/2007\9:54:31 AM

Table 7

Total Cancer Risks and Noncancer Hazardsfor RSA-011 Receptors

Without Background-Related Metals1

Redstone Arsenal, Madison County, Alabama

Receptors

Current SiteUse3

Soil

Future Site-Use"

Soil Groundwater Total Risk

CANCER RISK

Industrial Receptors:

Groundskeeper (Conventional) c

Groundskeeper (Alternative) d

Construction Worker (Conventional) c

Construction Worker (Alternative) d

Recreational Receptors:Sportsman e

Trespasser e

Hypothetical Residential Receptors:

Resident (Conventional) c

Resident (Alternative) d

5.20 x10'7

NE3.04 x10'8

NE

NE3.06xJCr"

NE

NE

5.20 x10"7

5.37 x10'7

3.04x10'8

2.23x 10"6

7.45x10'"

3.06x10'"

3.20 x10'6

1.57x10'6

4.10x10"

4.10x10"

1.82x10'5

1.82x10'5

NE

NE

1.37 X10"1

1.37 xlO"3

4.11x10"

4.11x10"

1.83x10'5

2.05 x10'5

7.45 x 10'8

_3_.06_x :J Cf"_

1.38 xlO"3

1.37 xlO"3

NONCANCER HAZARD

Industrial Receptors:Groundskeeper (Conventional) c

Groundskeeper (Alternative) d

Construction Worker (Conventional) c

Construction Worker (Alternative) d

Recreational Receptors:Sportsman e

Trespasser *

Hypothetical Residential Receptors:Resident, child (Conventional) c

Resident, child (Alternative) "

0.104

NE

0.041

NE

NE

0.015

NE

NE

0.104

0.100

0.041

0.496

0.012

0.015

1.61 d

1.49d

20.6

20.6

22.8

22.8

NE

NE

78.0

78.0

20.7

20.7

22.9

23.3

0.012

0.015

79.6

79.4

NE - Not evaluated.Bold font entries represent cancer risk values that exceed the 1 x 10"* to 1 x 10"* risk management range ornon-cancer hazard values that exceed the threshold level of 1 and are unacceptable.

1 Does not include the cancer risks and noncancer hazards from the background-related metals aluminum, arsenic,and vanadium.

a Includes only exposure to soil.b Includes exposure to both soil and groundwater.c Conventional - Exposure to surface soil except for construction worker, where exposure is to surface soil and

subsurface soil.d Alternative - Total soils. Total soil hypothetically assumes surface and subsurface soil are mixed during future

development.8 Includes only exposure to surface soil.

KN7\RSA\RSA-011 \ROD\Rnal\Tabs 6.7.8,9.doc\8/14/2007\9:54:31 AM

Table 8

Results of the Vapor Intrusion Evaluationfor Trichloroethene at RSA-011

Redstone Arsenal, Madison County, Alabama

StructureEvaluated

HypotheticalFuture ResidentialBuilding

Building 7901

Building 7902

Building 7908

Receptor

HypotheticalFuture Resident

Future IndoorCommercial

Worker

Soil GasConcentration *

(ug/m3)

2.47E+00

2.47E+00

2.47E+00

2.47E+00

Modeled Indoor AirConcentrations

(ug/m3)

1.07E-04

2.23E-04

1.82E-04

3.21E-04

Modeled Indoor AirResults Compared

to EPA (2002)Screening Values "

Result is less than1 x 1 Devalue

Result is less than1 x tO* value

Result is less than1 x 1 Devalue

Result is less than1 x1 Devalue

Modeled Indoor AirResults Compared

to California-Modified PRG(EPA Region 9

2004) c

Result is less than1 x 1 Devalue

Result is less than1 x1 Devalue

Result is less than1 x 1 Devalue

Result is less than1 x1 Devalue

ug/m3 - Micrograms per cubic meter.

' Maximum detected soil gas concentration from two soil vapor sampling points." Residential indoor air concentrations from Tables 2a, 2b and 2c (EPA, 2002) using inhalation slope factor from EPA (2001):TCE indoor air concentration at 1 x 10"6 = 0.022 pg/m3.TCE indoor air concentration at 1 x 10"5 = 0.22 ug/m3.TCE indoor air concentration at 1 x 10"1 = 2.20 ug/m3.

c California-modified PRG for TCE in ambient air concentration from EPA Region 9 PRG table (EPA Region 9. 2004) usinginhalation slope factor from Cal EPA (2002):TCE indoor air concentration at 1 x 10"6 = 0.961 ug/m3.TCE indoor air concentration at 1 x 10"5 = 9.61 ug/m3.TCE indoor air concentration at 1 x 10""1 = 96.1 ug/m3.

ug/m3 - Micrograms per cubic meter.PRG - Preliminary remediation goal.TCE - Trichloroethene.

References:

California Environmental Protection Agency (Cal EPA), 2002, Air Toxics Hot Spot Program Risk Assessment Guidelines, Part II.Technical Support for Describing Available Cancer Potency Factors, December.

U.S. Environmental Protection Agency (EPA), 2001, Trichloroethylene Health Risk Assessment: Synthesis and Characterization(External Review Draft). Office of Research and Development, National Center for Environmental Assessment (NCEA), WashingtonOffice, Washington DC, EPA/600/P-01/002A.

U.S. Environmental Protection Agency (EPA), 2002, Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway fromGroundwater and Soils Subsurface Vapor Intrusion Guidance, Office of Solid Waste, EPA530-F-02-052, November.

U.S. Environmental Protection Agency (EPA), 2004, Region 9 2004 Preliminary Remediation Goals Table, EPA Region 9, SanFrancisco, California, October, on-line.

KN7\RSA\RSA-011 \ROD\Final\Tabs 6.7.8,9.doc\8/14/2007\9:54:31 AM

Table 9

Summary of Screening-Level Ecological Risk Evaluation ResultsforRSA-011

Redstone Arsenal, Madison County, Alabama

Step 3aCOPEC

Aluminum

Antimony

Arsenic

Cadmium

Chromium (III or VI)

Lead

Mercury-Inorganic

Silver

Thallium

Vanadium

Zinc

Cyanide

bis(2-Ethylhexyl)phthalate

Total PAHs

Dieldrin

4,4'-DDD

4.4'-DDE

4.4'-DDT

Results of Food Chain Modeling

Max-NOAELHQ greaterthan 1 and

Max-LOAELHQ less than

1

X

X

X

X

X

X

X

X

X

Max-NOAELHQ greaterthan 1 and

Max-LOAELHQ over 1

X

X

X

X

X

X

X

X

X

X

Mean-NOAELHQ greaterthan 1 and

Mean-LOAELHQ less than

1

X

X

X

X

X

X

X

X

X

X

Mean-LOAELHQ over 1

X

X

X

Results ofPlant &

EarthwormCommunityAnalysis-

Mean HQ over1

X

X

X

X

X

X

X

X

X

NSV

NSV

NSV

NSV

NSV

NSV

NSV

Retain as aCOC?

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

RationaleCode

BKG

BKG

BKG

MAX ONLY

LOW HQs

LOCAL

MAX ONLY

MAX ONLY

ANAL

BKG

LOW HQs

NOT BIO

MAX ONLY

MAX ONLY

MAX ONLY

OTHER

OTHER

OTHER

Notes:X - Range of HQ based on the results of the screening-level ecological risk assessment.HO - Hazard quotient based on mean or maximum concentration compared to toxiaty reference value.LOAEL - Lowest-observed-adverse-effect level.NOAEL - No-observed-adverse-effed level.Max - Maximum detected value.Mean - Arithmetic average concentration.COPEC - Chemical of potential ecological concern.COC • Chemical of concern.NSV - No screening value available.N - COPEC is not retained as a COC.

Rationale Codes:BKG - Background related.ANAL - Current data indicate that elevated values in historical samples cannot be confirmed.MAX ONLY - Maximum but not average exposure point concentrations resulted in HQs over 1 for food chain receptors. Elevated concentrations werenot sufficiently wide-spread to result in population-level impacts.LOW HQs - HQs were less than 1 for most receptors and did not exceed 10 for any receptor.LOCAL - Elevated concentrations localized to 0.16 acre area around one sludge bed.NOT BIO - Chemical is not listed as being bioaccumulative. Food chain modeling is likely to have over estimated potential hazards.OTHER - The only receptor with HQs greater than 1 is the American Robin. RSA-011 can only support 2 individuals based on site size. Therefore, nopopulation level impacts would be possible.

KN7\RSA\RSA-011 \ROD\Final\Tabs 6,7.8,9.doc\8/14/2007\9:54:31 AM

FIGURES

KN7\RSA\RSA-OI I\ROD\D-F\01 l-DF-ROD.doc\8/l4/2007\9:53:38 AM

^Limestone

County

. • ',• ...I,-

JcioksonCounty

Redstone Arsenal

Location of Redstone Arsenaland Surrounding Cities ofMadison County, Alabama

__^ U.S. Army Corps of Engineers7jiij7i| Redstone ArsenalilJj Madison County, Alabama

, , Contract No. DACA21 96-D-0018

ShaMV* Sfew Envicmicnlal, 're

X:\Redstone\GIS_Documems\Project_maps\Miscenaneous\RSA_Madison_Co_Alabama.mxd

Legend

I I RSA-011 Site Boundary

I | Operable Unit Boundaries

I I Site Boundaries

|'. • • , - ; • ! RSA-146

IH'.VJ Water Bodies

—— Former Sludge Drying Bed

Tanks

;V:>' NWI Classified Wetlands

| | Existing Structures

Roads

Surface Water Drainage Features (some ephemeral) * l • Fences

Figure 2

RSA-011 Site Location Map

U.S. Army Corps of Engineers.... .. Redstone Arsenal

I!. |. Jl Madison County, AlabamaContract No. DACA21-96-D-0018

ShaW Shaw Environmenital, Inc.

X-\Redstone\GIS_Documents\Project_maps\RSA_011 \rsa_011_site_location_map.mxd9/20Y2006 4:35:41 PM

RSA-01 1, looking north. Main pump station(Bldg 7902) and Plant 1A Digester (Bldg 7914)shown on right. Lift Station (Bldg 7907/7916)on left side of photograph.

RSA-011, looking northeast. Plant 1A SludgeDrying Bed (Bldg 7915) In foreground, Plant 1ADigester (Bldg 7914) and Secondary Clarifler(Bldg 7913) back left. Plant 1B Digester (Bldg 7911)center right of photograph.

RSA-011,looking northeast. Plant IB SludgeDrying Beds (Bldg 7912) In foreground withPlant 16 Digester (Bldg 79111; Primary/Secondarydanders (Bldg 7901/7909) center left side ofphotograph.

Figure 3

RSA-011 Site PhotosDated April 2. 2003

U.S. Army Corpi of EngineersRedstone Arsenal

| i 11111| Madison County. Alabama1 ComractNumberOACA2l-96-D-0018

Shaw' Shaw Environmental, he

JtlR«drtin.\GIS_Doc<jn»n»tolJtpuWSA_Ol1_DF_ROD_JulyZ007\RSA_Oll_«il«_ptiolD..U

InactiveEffluent Line

(To Huntaville Spring Branch)

WoodedWetland

InactiveTreatment System Components

(Generalized)

jfk.ij i- ,;.-: i;i. -£\ -jj •2L);!Sv? *- *• TT JI:

::.-: • ; . " ' : ' • : /' : ' Perc*iloBte and TCE rngroundwater "'• ' ';.: ...

'Depth to groundwaterranges from approx: :

.2-14 fee! below surface

Perchlorate, TCE. and other potential contaminants may have leaked to soils frombreaks or cracks in treatment system piping or other components, but no contaminantremains in soil at sufficient concentrations or mass to leach to groundwatar.

Pesticides have been detected In soils as a result of the legal application to controlpests in and around the sewage treatment plant. Pesticides are essentially immobile inthe sol] system and do not leach to groundwater.

Lead and mercury were detected In soils above their background values and atlocations that would seem to be process-related. However, these metals are essentiallyImmobile In the soil system; migration of these metals will occur at rates driven bynatural infiltration. Travel times to reach groundwater ere estimated at 3.983 years formercury and 3.903.000 years for lead.

Exposure to soils alone (without Including exposure to groundwater) poses nounacceptable health threat to any receptor from site-related chemicals.

Several organic chemicals, perchlorate, and several metals In groundwater were Identifiedas COCs for all exposed receptors. These chemicals will pose a threat to human health only ifgroundwater underlying RSA-011 Is developed as a potable water source.

VOCs were detected In SOU gas samples. Based on concentrations of VOCs In soil gassamples, modeled indoor air concentrations of TCE originating from groundwater and/orsoil contamination at RSA-011 poses no unacceptable health threat to any receptor.

No adverse impacts to populations of non-spedal status spades that reside at or use thissite are anticipated. Exposure to site-related metals may have the potential to impactindividuals within the plant and soil communities. DDT, DDE, and DDD may have thepotential to impact individual birds feeding at RSA-011.

Figure 4

RSA-011 Conceptual Site Model

U.S. Army Corps of EngineersRedstone ArsenalMadison County, AlabmaContract No. DACA21 96-O-001B

X:\bdiioni\GIS_Documfntt\Outpvt\RSA_01 1_PP_J Jy2»7\RSA_01 l_tonceptu>l_dTt_inodcLBl

ContaminationSource

Releases fromSewage &

WastewaterProcesses

1 = Comp2 = Incom

pathw3 = Althou

vegete4 = Resid5 = Althou

pathw' Subsurfc" Ground1.-remedial

c Househc

SourceMedium

Surface

• ' Cg

c "-2.g>CD E

lli

L-*•

-Hr"l

SubsurfaceSoil —*

Primary Secondary Secondary Exposure ExposureRelease Medium Release Medium Route

Receptors

Gro

unds

keep

er (

Cur

rent

)

1

Gro

unds

keep

er (

Fut

ure)

14

Con

stru

ctio

n W

orke

r (C

urre

nt)

1

Con

stru

ctio

n W

orke

r (F

utur

e)

11

Spo

rtsm

an (

Fut

ure)

1•i

Tre

spas

ser (

Cur

rent

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1

Hyp

othe

tical

Res

iden

t (F

utur

e)

I

1t

Indo

or W

orke

r (F

utur

e)

2O

Dust Emissions. A:, | 1 1 1 1 1 1 1 1 >Vnlatiltratinn * IlllialdllUII

. a| Browsing by Deer H Venison | H Ingestion

Pla"tUptake H Ve9etaU°n HFoodchainuptake^l^^l "I **«*™ \Vnlatili7atinn > Indoor Air" | ^ Inhalation

<5oil ^ Ingestion"" Dermal Contact

12

2

2

22

1

2

2

2

11

1

2

2

2

22

1

2

2

2

1

1

1

1

2

2

22

1

2

2

2

22

3 2

4

1

1

11

2

Ter

rest

rial

Eco

logi

cal R

ecep

tors

1

2

2

1 Ih1

2

2

EL

22

Volatilization ' Inhalation 2

22

1

11

2

22

1

1

1

2

22

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APPENDIX A

GLOSSARY OF TERMS

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GLOSSARY OF TERMS

Administrative Record -The body of reports, official correspondence, and other documentsthat establish the official record of analysis, cleanup, and final closure of a CERCLA or RCRAsite.

Background Levels - Ambient concentrations of inorganic elements (metals) that are present inthe environment and have not been altered by human activity.

Baseline Human Health Risk Assessment (BHHRA) - Analysis of the potential adversehuman health effects (current or future) caused by hazardous substance release from a site in theabsence of any actions to control or mitigate these releases.

Characterization - The compilation of all available data about the waste unit to determine therate and extent of contaminant migration resulting from the waste site, and the concentration ofany contaminants that may be present.

Chemicals of Concern (COC) - Where cumulative risks have been found to exceed designatedrisk thresholds, chemicals with risks exceeding Ix 10"6 (or an excess lifetime cancer risk of 1 in1,000,000) or an HI = 0.1 may be selected as COCs. These are chemicals that significantlycontribute to unacceptable risks for a pathway in an exposure model for a hypothetical receptor(e.g., a child that resides on the site).

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA),1980 - CERCLA was enacted by Congress in 1980 and was amended by the SuperfundAmendments and Reauthorization Act in 1986. CERCLA provides federal authority to responddirectly to releases or threatened releases of hazardous substances that may endanger publichealth or the environment. CERCLA established prohibitions and requirements concerningclosed and abandoned hazardous waste sites and established the Superfund Trust Fund.

Contaminant Plume - A column of contamination with measurable horizontal and verticaldimensions that is suspended and moves with groundwater.

Dilution Attenuation Factor 4 (DAF4) Soil Screening Levels (SSL) - DAF4 SSLs are soilthreshold concentrations calculated using methodology developed by EPA below which there isnot a concern for migration of residual contaminants in soil to groundwater at concentrationsabove MCLs or risk-based screening concentrations. Dilution attenuation factors represent thereduction in the contaminant concentrations through soil. A DAFi means there is no dilution orattenuation through the soil column. A high DAF value means there is a high degree of dilutionor attenuation. The Army in conjunction with EPA and ADEM have determined that a DAF4

best matches the site-specific fate and transport processes at RSA-011.

Exposure - Contact of an organism with a chemical or physical agent. Exposure is quantified asthe amount of agent available at the exchange boundaries of the organism (e.g., skin, lungs, gut)and available for absorption.

Groundwater - Underground water that fills pores in soil or openings in rocks to the point ofsaturation. Groundwater is often used as a source of drinking water via municipal or domestic

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wells. Groundwater that comes to the earth's surface, such as streams and springs, is consideredsurface water. At Redstone Arsenal, the groundwater is not a source of drinking water.

Groundwater Site - Sub-watersheds defined at Redstone Arsenal from a site-widehydrogeologic investigation. Each groundwater site will proceed through a separate CERCLAinvestigation to get to closure of the site.

Interim Record of Decision (TROD) - Document prepared when a quick action is needed toprotect human health and the environment or when a temporary measure to stabilize the site/andor prevent contamination migration is needed. A final ROD must follow an IROD.

Maximum Contaminant Level (MCL) - National standards for acceptable concentrations indrinking water in treatment plants producing potable water. These standards are legallyenforceable standards set by the EPA under the Safe Drinking Water Act.

National Priorities List (NPL) - The EPA's list of the most serious uncontrolled or abandonedwaste sites identified for possible long-term remedial response action under Superfund. EPA isrequired to update the NPL at least once a year. A site must be on the NPL to receive moneyfrom the Trust Fund for remedial action. The Army funds the cleanup of RSA-011.

Operable Unit (OU) - A discrete portion of a remedial response that comprises an incrementalstep toward addressing site problems. It can be a geographic area and can address anenvironmental medium at the site (e.g., groundwater). At Redstone Arsenal, OUs aredistinguished primarily from a topographic/watershed and ecological habitat/range standpoint.

Perchlorate - Salts used in solid rocket fuel for rockets and missiles at Redstone Arsenal.

Principal Threat Waste - Source materials considered to be highly toxic or highly mobile thatgenerally cannot be reliably contained or would present a significant risk to human health or theenvironment should exposure occur.

Proposed Plan (PP) - A legal document that provides a brief analysis of remedial alternativesunder consideration for the site/operable unit and proposes the Preferred Alternative. It activelysolicits public review and comment on all alternatives under consideration.

Record of Decision (ROD) - A legal document that explains to the public which remedial cleanup alternative will be used at a site. The ROD is based on information and technical analysisgenerated during the remedial investigation, risk assessments, feasibility study, and considerationof public comments and community concerns.

Remedial Investigation (RI) - A study designed to gather data needed to determine the natureand extent of contamination at a Superfund site. The RI at Redstone Arsenal includes a baselinehuman health risk assessment and a screening-level ecological risk assessment.

Resource Conservation and Recovery Act (RCRA), 1976 - A Federal law that gives EPA theauthority to control the generation, transportation, treatment, storage, and disposal of hazardouswaste. RCRA focuses only on active and future facilities and does not address abandoned orhistorical sites.

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Responsiveness Summary - A summary of oral and/or written comments received during thestatement of basis/proposed plan comment period and includes responses to those comments.The Responsiveness Summary is a key part of the ROD, highlighting community concerns.

Screening-Level Ecological Risk Assessment (SLERA) - The initial phase of a baselineecological risk assessment in which conservative concentrations of site chemicals arequantitatively compared to chemical- and media-specific generic effect levels. Those chemicalsselected as chemicals of potential ecological concern are further refined through quantitativecomparison to chemical- and species-specific effect does, as well as qualitative examination.Those chemicals identified as chemicals of concern may be investigated further, remediated, orleft in place per the decision of the risk managers.

Soil Vapor - Vapor that resides in the interstitial pores between soil particles.

Solid Waste Management Unit (SWMU) - Site at which solid wastes have been placed at anytime, regardless of whether the uni t was intended for the management of solid or hazardouswaste and from which contaminants may migrate.

Statement of Basis (SB) - A report describing the corrective measures/remedial actions beingconducted pursuant to the Alabama Hazardous Waste Management Regulations, as amended.

Subsurface Soil - Soil that is below 1 foot from the ground surface.

Superfund Amendments and Reauthorization Act (SARA) - A plan for a site cleanup thatproposes a recommended or preferred remedial alternative. The Statement of Basis/ProposedPlan is available to the public for review and comment and the Preferred Alternative may changebased on public and other stakeholder input .

Surface Media-The soil (surface and subsurface) and soil vapor at RSA-011.

Surface Soil - Soil that is 0 to 1 feet below ground surface.

Trichloroethene (TCE) - TCE is a colorless or blue liquid with an odor similar to ether. It isman-made and does not occur naturally in the environment. TCE was once commonly used toremove oils and grease from metal parts and has been used in the dry cleaning industry.

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