RECORD OF DECISION (RODS) - Records Collections · Record of Decision for Surface Media at RSA-196,...

Final

Record of Decision for Surface Media at

RSA-196, Test Stand and Cleaning Building Operable Unit 10

Redstone Arsenal Madison County, Alabama

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

Prepared for:

u.s. Army Corps of Engineers, Savannah District P.O. Box 889

Savannah, Georgia 31402-0889

Prepared by:

Shaw Environmental, Inc. 312 Directors Drive Knoxville, TN 37923

Delivery Order 0029 Contract No. DACA21-96-D-0018

Shaw Project No. 121008

August 2009

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Table of Contents_________________

Page

List of Tables ................................................................................................................................. iii

List of Figures ................................................................................................................................ iii

List of Exhibits ............................................................................................................................... iii

List of Acronyms ........................................................................................................................... iv

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 .......................................................................... 1-1

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 ofInvestigative Activities ................................................................. 2-3

2.2.3 History of CERCLA or RCRA Enforcement Activities ................................ 2-5

2.3 Community Participation ........................................................................................... 2-5

2.4 Scope and Role of Operable Unit or Response Action .............................................. 2-7

2.4.1 Overall Remedial Strategy for Redstone Arsenal and RSA-196 ................... 2-7

2.4.2 Scope of Problems Addressed by RSA-196 Response Action ...................... 2-8

2.4.3 Relationship of Selected Remedy to Response Action or Other Operable Units ............................................................................................... 2-8

2.5 Site Characteristics ..................................................................................................... 2-8

2.5.1 Conceptual Site Model ................................................................................... 2-9

2.5.2 Nature and Extent of Contamination ........................................................... 2-11

2.5.2.1 Nature and Extent of Soil Contamination ..................................... 2-12

2.5.2.2 Nature and Extent of Groundwater Contamination ...................... 2-14

2.5.3 Fate and Transport ....................................................................................... 2-14

2.6 Current and Potential Future Land and Resources Use ........................................... 2-14

2.6.1 Current and Future Land Use ....................................................................... 2-15

2.6.2 Current and Future Groundwater Use .......................................................... 2-15


Table of Contents (Continued) _______________

Page

2.7 Site Risks ................................................................................................................. 2-16

2.7.1 Baseline Human Health Risk Assessment ................................................... 2-16

2.7.1.1 Step 1 - Identify Chemicals of Potential Concern ........................ 2-17

2.7.1.2 Step 2 - Conduct an Exposure Assessment ................................... 2-17

2.7.1.3 Step 3 - Conduct a Toxicity Assessment ...................................... 2-19

2.7.1.4 Step 4 - Characterize the Ri sks ..................................................... 2-19

2.7.1.5 Summary of the Baseline Human Health Risk Assessment ......... 2-22

2.7.2 Screening-Level Ecological Risk Assessment ............................................. 2-22

2.7.2.1 Step 1 - Screening-Level Problem Formulation and Toxicity

Assessment. ................................................................................... 2-22

2.7.2.2 Step 2 - Screening-Level Exposure Estimate and Risk Calculation .................................................................................... 2-22

2.7.2.3 Step 3 - Problem Formulation Refinement ................................... 2-23

2.7.3 Sourcing to Groundwater Summary ............................................................ 2-23

2.7.4 Risk Summary .............................................................................................. 2-24

2.7.5 Basis for Action ........................................................................................... 2-25

2.8 Documentation of Significant Changes ................................................................... 2-25

3.0 Responsiveness Summary ................................................................................................... 3-1

4.0 References ........................................................................................................................... 4-1

Appendix A - Glossary of Terms

Tables

Figures

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L~tafTables____________________________________

Table Title Follows Text

1 Historical Building Use

2 Soil Data Summary for Perchlorate

3 Total Cancer Risks and Noncancer Hazards for Receptors Without BackgroundRelated Metals

4 Results of the Vapor Intrusion Evaluation

5 Summary of Screening-Level Ecological Risk Evaluation Results

ListafFigures______________________________________

Figure Title Follows Text

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

2 RSA-196 Site Location Map

3 RSA-196 Conceptual Site Model Summary

4 RSA-196 Sample Locations

List af Exhibits......__________________________________ _

Exhibit Title Page

1 Administrative Record File and Information Repository Locations 2-6

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ListofAcronyrns __________________________________ __

ADEM

Army

bgs

BHHRA

BSV

CalEPA

CD

CERCLA

CERCLIS

COC

COPC

COPEC

CSM

DAF

DWEL

EBS

EPA

FS HAL

HI

HQ

IROD

IRP

LUC

MCL

11gIL

NCP

OU

PCB

PP

PRG

PSA

RARE

Alabama Department of Environmental Management

U.S. Army Garrison - Redstone

below ground surface

baseline human health risk assessment

background screening value

California Environmental Protection Agency

compact disk

Comprehensive Environmental Response, Compensation, and Liability Act

Comprehensive Environmental Response, Compensation, and Liability

Information System

chemical of concern

chemical of potential concern

chemical of potential ecological concern

conceptual site model

dilution attenuation factor

drinking water equivalent level

environmental baseline survey

U. S. Environmental Protection Agency

feasibility study

health advisory level

hazard index

hazard quotient

interim record of decision

Installation Restoration Program

land-use control

maximum contaminant level

micrograms per liter

National Oil and Hazardous Substances Pollution Contingency Plan

Operable Unit

polychlorinated biphenyl

Proposed Plan

preliminary remediation goal

potential source area

Redstone Arsenal Rocket Engine

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List ofAcronyms (Continued)________________

RCRA

RDX

RID

RI

ROD

RSA-196

SARA

SB

Shaw

SLERA

SPLP

SSL

SVOC

TAL

TCA

TCE

VOC

Resource Conservation and Recovery Act

cyc10trimethylenetrinitramine or hexahydro-l ,3,5-trinitro-1 ,3,5-triazine

reference dose

remedial investigation

Record of Decision

Test Stand and Cleaning Building

Superfund Amendments and Reauthorization Act

Statement of Basis

Shaw Environmental, Inc.

screening-level ecological risk assessment

synthetic precipitation leaching procedure

soil screening level

semivolatile organic compound

target analyte list

trichloroethane

trichIoroethene

volatile organic compound

KN9!RSA1196!RODlFinallF-196 ROD.doc/S/5/2009 1245 PM v

1.0 The Declaration

1.1 Site Name and Location

Test Stand and Cleaning Building (RSA-196) Operable Unit (OU) 10 Redstone Arsenal Madison County, Alabama

Comprehensive Environmental Response, Compensation, and Liability Information System (CERCLIS) Identification Number: AL7210020742

U.S. Army Garrison - Redstone (Army)

1.2 Statement of Basis and Purpose

This Record of Decision (ROD) presents the Selected Remedy of No Action for the surface

media (defined as surface soil, subsurface soil, and soil vapor) at RSA-196 at Redstone Arsenal

in Madison County, Alabama. The remedy was chosen in accordance with the Comprehensive

Environmental Response, Compensation, and Liability Act (CERCLA) as amended by the

Superfund Amendments and Reauthorization Act (SARA) of 1986, and, to the extent practicable,

the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 Code of

Federal Regulations, Part 300. The remedy is designed to meet CERCLA requirements and

address the substantive requirements under the Resource Conservation and Recovery Act

(RCRA), where applicable. The goal was to select a remedy that is acceptable under both

programs and one which limits duplication of closure efforts.

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

RSA-196, which has been developed in accordance with Section 113 (k) ofCERCLA and which

is available for review at the information repositories presented in Exhibit 1 on Page 2-6.

The Army and the U.S. Environmental Protection Agency (EPA) have selected the final remedy

of No Action for RSA-196. The Alabama Department of Environmental Management (ADEM)

concurs with the Selected Remedy.

A glossary of terms used in this ROD is presented in Appendix A.

1.3 Description of the Selected Remedy

The Army and EPA, with concurrence from ADEM, have determined that a No-Action remedy

is required for surface media at RSA-196 to ensure protection of human health and the

environment. The groundwater beneath RSA-196 is not part of the scope of this surface media

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ROD; any further groundwater investigation/cleanup under RSA-196 will be conducted with the

RSA-146 groundwater site.

1.4 Statutory Determinations

No remedial action is necessary to protect human health and the environment at RSA-196. The

No-Action remedy allows for unrestricted use and unlimited exposure to surface media at RSA

196. Because no contaminants remain at the site in the surface media at concentrations of

concern to human health and the environment, CERCLA Five-Year Reviews of this site are not

required. Therefore, none of the CERCLA §121 statutory determinations need to be addressed.


Franklin E. Hill, Director

1.5 Authorizing Signatures

'i(20((J1 Robert M. Pastorelli Date Colonel, US Army Superfund Division Garrison Commander U.S. Environmental Protection Agency,

Region 4

Concurrence:

Wm. Gerald Hardy, Land Division Alabama Department of Environmental Management

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2.0 Decision Summary

2.1 Site Name, Location, and Description

Test Stand and Cleaning Building (RSA-196) OU-10 Redstone Arsenal Madison County, Alabama

CERCLIS Identification Number: AL7 210 020 742

This ROD is issued by the Army, the lead agency for conducting remedial actions at CERCLA

sites at Redstone Arsenal. EPA and ADEM are the regulatory agencies providing oversight of

the Army's CERCLA cleanup program at Redstone Arsenal. The Army is funding the

investigation and close-out ofRSA-196.

Redstone Arsenal is located in the southwestern portion of Madison County, which is in the

northern portion of Alabama (Figure 1). Redstone Arsenal 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 1).

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

all of which are either owned or controlled by the Army (Figures 1 and 2). Development within

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

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

rockets. Chemical wastes have resulted from these processes since operations began in the early

1940s. Redstone Arsenal is composed of the U. S. Fish and Wildlife Service's Wheeler National

Wildlife Refuge in the central and southern portions of Redstone Arsenal; industrial areas in the

southeastern portion; facilities at the National Aeronautics and Space Administration's George

C. Marshall Space Flight Center for space flight support in the central portion; and training areas,

family housing, and commercial, recreational, and medical centers in the northern portion.

Missile/rocket test ranges, along with the associated range fans, test area safety fans, and

explosive safety-quantity distance arcs, are present in the western and southern portions of

Redstone Arsenal. Other mission-related land use in the southern portion of Redstone Arsenal

includes munitions storage.

RSA-196 is approximately 4.2 acres in size and is located in the north-central portion of

groundwater site RSA-146 (Figure 2). The groundwater site covers the southeast quadrant of

Redstone Arsenal between Huntsville Spring Branch and the Tennessee River. Topographic KN9!RSA1196!RODlFinallF-196 ROD.doc/S/5/2009 1245 PM 2-1

relief in this portion of Redstone Arsenal is minimal, due in part to leveling during construction

of this industrialized area of the Arsenal. Maximum relief between RSA-196 and the Tennessee

River and other surface water bodies is about 10 to 25 feet. An unlined drainage ditch west of

Building 7373/7374 (south side of Blue Jay Road) received discharge from the industrial drain

and sump at the building. Much of the site is covered in buildings or pavement (Figure 2). The

remainder is vegetated primarily by mowed grass and fast-growing pine trees.

Facilities at RSA-196 were used for rocket motor testing including development of propellants.

This site lies in the midst of several former Thiokol Corporation facilities where rocket motors

were also tested or produced. RSA-196 and most of the nearby sites are known or suspected

sources of perchlorate and/or trichloroethene (TCE) in shallow groundwater (Shaw

Environmental, Inc [Shaw], 2009a, 2008).

2.2 Site History and Enforcement Activities

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

RCRA enforcement activities at RSA-196.

2.2.1 History of Site Activities

The current RSA-196 site boundary was established in 2006 following a potential source area

(PSA) investigation within the RSA-146 groundwater site. The PSA investigation recommended

further investigation of the RSA-196 area to determine whether it represented a source of

contamination to groundwater (Shaw, 2005a). RSA-196 was subsequently established as a

CERCLA site. RSA-196 encompasses suspected contaminant sources and migration pathways

associated with historical operations at Building 7373/7374. The site as currently configured

contains two existing buildings: Building 7346 and Building 7373/7374. The current RSA-196

boundary includes two environmental sites: RCRA site RSA-161 (Case Prep Building, former

Building 7346A) and CERCLA site RSA-098 (Chlorinated Solvent Distillation Unit 5, Building

7346). Figure 2 shows the boundary ofRSA-196 relative to adjacent and inclusive sites. The

Army completed a remedial investigation (RI) at RSA-196 in 2007; a detailed history of previous

investigations is presented in the RI report (Shaw, 2009a). The following paragraphs present a

brief history of the site.

Building 7373fl374. The original Building 7373, the primary historical structure associated

with RSA-196, was built in 1945 to serve as a tetryl screening facility, although it may have

never operated for that purpose given that World War II was ending. The building was known to

have been used as a static test stand for small rocket motors in the 1950s. Finished rocket motors

were mounted to large steel-covered concrete thrust blocks and test fired to measure the bum rate


and the efficiency of propellants. The building also served as a parts cleaning facility.

Propellant mixing and casting tools were brought to this location for cleaning using spatulas,

hoes, and brushes to manually scrape off the remaining propellant. The tools were then washed

with water. Later, a high-pressure spray method was used containing a solution of water,

detergent, and a caustic which minimized the exposure of personnel to the propellant. Building

7374 (built in 1951) was a control room to monitor rocket motor testing activities at Building

7373 while protecting personnel and equipment. Buildings 7373 and 7374 were connected under

one roof in 1984 and are referred to as Building 737317374. Because of the research and

development nature of the testing, it is likely that rocket motor explosions ejected material into

the open field north of Building 737317374 before Building 7346 was built in 1987. The static

testing in Building 737317374 was phased out in the late 1950s and the testing was transferred to

Building 7620. Testing continued at 737317374 as a backup facility and the building was once

again used for parts cleaning in the mid- to late 1980s. Parts were cleaned in a large tank using

various solvents. Three 350-gallon TCE storage tanks were used in degreasing operations in the

building. Table 1 presents the historical building use for Buildings 737317374, 7346, and 7346A.

Building 7346. Building 7346, north of Building 737317374, was built in 1987 and was

included within the RSA-196 site boundary because it was constructed within the northern area

suspected to be impacted by historical releases of perchlorate and/or explosives from historical

testing activities at Building 737317374. Building 7346, a former solvent distillation unit, was

investigated under CERCLA as RSA-098 and was not directly targeted for additional evaluation

under the RSA-196 RI. An RI report for RSA-098 recommended no further investigative or

remedial action for surface media (Shaw, 2004). Closure for RSA-098 will occur concurrently

with RSA-196. ADEM has agreed with this approach for addressing closure at RSA-098, as

stated in their September 2007 concurrence letter to the Army. Building 7346 is currently

occupied by industrial and administrative staff.

Building 7346A. Building 7346A (built in the mid- to late 1980s and demolished in 2003) was

a concrete pad (7.25 by 12.25 feet) with a steel shed cover. The facility was used for temporary

staging of waste materials containing perchlorate, solvents, and wastewater (Shaw, 2009a). The

building was investigated and closed out under RCRA as RSA-161 (case preparation building)

(Shaw, 2006a).

2.2.2 History of Investigative Activities

Since RSA-196 is designated as a surface media site, investigations at this site were primarily

focused on soils and other surface media such as soil vapor. Surface water and sediment are also

surface media but were not present on RSA-196. Groundwater samples were collected primarily


to locate potential contaminant source areas in soil and to determine whether chemicals present

in soil are currently leaching to groundwater. Groundwater under RSA-196 will be further

investigated as part of groundwater site RSA-146 (Figure 2). The sampling results are discussed

in Section 2.5.2 of this document.

A number of assessments/investigations have been conducted at sites in the Redstone Arsenal

Rocket Engine (RARE) North Plant area, including RSA-196. These include the following:

• A Phase I environmental baseline survey (EBS) was conducted in 1996 for the RARE North Plant area to identify conditions that may pose environmental concerns and past or present activities that may result in potential hazardous, toxic, and radiological waste liability for the Army (Conestoga-Rovers and Associates, 1996). The EBS recommended further evaluation of Building 7373/7374.

• A Phase II EBS was conducted at the RARE North Plant area in 1997 based on the initial findings of the Phase I EBS (CH2M Hill, 1998). Soil and groundwater samples were collected near Building 7373/7374.

• An RI was conducted from 1996 to 2003 at RSA-098 (Building 7346) which concluded that operations at Building 7373/7374 were the most likely sources of perchlorate detected around Building 7346 (Shaw, 2004). No action is recommended for RSA-098 and it is planned that this site will be closed with RSA-196.

• An OU-10/RSA-146 Phase I RI was conducted from 1999 to 2003 (Shaw, 2008). Soil and groundwater samples were collected to locate source areas impacting groundwater and to determine the nature and extent of groundwater contamination within RSA-146.

• A PSA investigation was conducted within RSA-146 in 2004 (Shaw, 2005a). Further investigation of the RSA-196 area was recommended to determine whether it represented a significant source of perchlorate contamination to groundwater. The historical rocket motor testing operation at Building 7373/7374 was identified as a likely source for perchlorate detected in soil around Building 7346. RSA-196 was subsequently established as a CERCLA site.

• An RI was conducted in two stages at RSA-196 in 2007 to determine the nature and extent of contamination in soil (Shaw, 2009a). Additionally, soil vapor sampling was conducted to evaluate concentrations of volatile organic compounds (VOC) in soil vapor that may pose risks via the vapor intrusion exposure pathway at RSA-196.


2.2.3 History of CERCLA or RCRA Enforcement Activities

No CERCLA or RCRA removal, remedial, or enforcement activities have been conducted to

date at RSA-196.

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 periodically sent to community members and are

made available to the public at public meetings. A mailing list of community members and

individuals that have requested information is maintained by the Army. 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, 2006b) 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.

The Army periodically holds a public meeting to inform the interested public about ongoing

environmental activities and to solicit interest in forming a restoration advisory board for

Redstone Arsenal. A meeting was held on November 1, 2007 to present an update of the Army's

baseline realignment and closure expansion plans at Redstone Arsenal and progress on

environmental investigation and clean up activities, including an interim record of decision

(IROD) for groundwater land-use controls (LUC) at the Arsenal (Shaw, 2007a). The last public

meeting was held on October 6,2008 to provide an update on the progress of the RSA-146

groundwater site RI. Another public meeting is planned for fall 2009.

A complete set of documents (hard copy and compact disk [CD]) used to make decisions about

the cleanup efforts at RSA-196 is available in the Administrative Record file managed on post by

the Army's Environmental Office. Electronic copies on CD are also located at local libraries.

Exhibit 1 on Page 2-6 presents a listing of repository locations and phone numbers for more

information.


Documents covering the investigation and close-out ofRSA-196 can also be obtained on line by

going to the archived documents under the Restoration Branch of the Army's public Web site

www.environmental.redstone.army.mil or by emailing the request to

[email protected]. This ROD will become part of the Administrative

Record file [NCP 300.825(a)(2)].

Exhibit 1: Administrative Record File and Information Repository Locations

Administrative Record File:

U.S. Army Garrison, Redstone Arsenal

Contact: Ms. Salee Sloan (256) 842-0314 Location: Environmental Management Division, 7741 Sandpiper Road Business Hours: Monday - Friday, 7:00 a.m. - 4:30 p.m. Central Time

Informati on Reposi tori es:

Triana Public Library (Triana Youth Center)

Contact: Ms. Blanche Orr (256) 772-3677 Location: 280 Zierdt Road, Triana, Alabama Business Hours: Monday - Thursday, 4 p.m. - 7 p.m. and Friday 2 p.m. - 5 p.m. Central Time

Huntsville-Madison County Public Library

Contact: Ms. Annwhite Fuller (256) 532-5969 Location: Heritage Room, 915 Monroe Street, Huntsville, Alabama Business Hours: Monday - Thursday, 9 a.m. - 9 p.m.; Friday - Saturday, 9 a.m. - 5 p.m.; and

Sunday, 1 p.m. - 5 p.m. Central Time

Public participation requirements in CERCLA and the NCP have been met in the remedy

selection process for RSA-196. The final RI report was released to the Administrative Record

file and made available to the public in July 2009 (Shaw, 2009a). The final Statement of Basis

(SB)lProposed Plan (PP) was released to the public on July 1,2009 (Shaw, 2009b). A 30-day

comment period was announced for July 2 to August 1, 2009. A notice of availability of the

RSA-196 RI report, the SBIPP, and other related documents in the Administrative Record file

was published in the local newspapers, including The Huntsville Times, Speakin' Out News, and

Redstone Rocket. The RSA-196 documents are available at the locations specified in the

information repositories listed in Exhibit 1 above. The SBIPP stated that a public meeting would

be held if there was sufficient interest from the public in having a meeting. No comments were

received during the 30-day public comment period that began on July 2,2009 and ended on


August 1, 2009. A meeting to discuss the remedial alternatives for RSA-196 was not requested

by the public.

2.4 Scope and Role of Operable Unit or Response Action

This section includes the scope and role of the response action for RSA-196 within the cleanup

strategy for Redstone Arsenal, the scope of the problems addressed by the response action for

RSA-196, and a discussion of the relationship of the Selected Remedy at RSA-196 to the

response action or other OUs.

2.4.1 Overall Remedial Strategy for Redstone Arsenal and RSA-196

The environmental concerns at Redstone Arsenal are extremely complex. As a result,

investigative work at over 200 sites in the Installation Restoration Program (IRP) at Redstone

Arsenal has been underway, and the sites have been organized into OUs. These OUs have been

defined based on similarities in historical processes or functions which have resulted in site

releases of a similar nature (Shaw, 2007b). Surface media sites are included in OU s 1 through

18; RSA-196 is part ofOU-IO. All 13 groundwater sites are included in OU-19. OU-20 is

reserved for the Wetland Integrator Operable Unit. Investigations and remedial decisions for

groundwater are being managed on the basis of the groundwater site. Surface soil, subsurface

soil, and soil vapor (and surface water/sediment, if applicable) are being investigated and

evaluated for discrete, location-bounded surface media sites.

Final RODs for surface media have been approved at OU-5, RSA-049; OU-6, RSA-057; OU-IO,

RSA-OII; OU-2, RSA-047; OU-IO, RSA-099; and OU-18, MSFC-002/087. A groundwater

IROD has been approved which selected LUCs for all groundwater sites in OU-19 (Shaw,

2007a). Numerous investigations are underway at the remaining IRP sites. This ROD selected

No Action as the final remedy for surface media at OU-IO, RSA-196.

The Selected No Action Remedy for RSA-196 considered risks from contaminants in surface

media, which include surface soil, subsurface soil, and soil vapor located within the site

boundary as well as risks from surface media evaluated on a cumulative basis with hypothetical

risks from groundwater. Surface media do not include groundwater beneath the site, which is

being investigated as part of the larger RSA-146 groundwater site (Figure 2). The groundwater

contamination under RSA-196, like many of the CERCLA sites at Redstone Arsenal,

encompasses contaminant contributions from more than one surface media site. The final

remedy for groundwater site RSA-146 will be selected following completion of an RIIfeasibility

study (FS), and any actions to address groundwater located under RSA-196 will be included as

part of the RSA-146 groundwater site remedy.


RSA-196 was included in the RCRA Part B permit as a solid waste management unit. Redstone

Arsenal was named to the National Priorities List on June 30, 1994. As a result, restoration

activities must meet CERCLA requirements. As per EPA policy, the Army coordinates with

EPA and ADEM to integrate CERCLA and RCRA requirements, respectively, for site cleanup

activities at this federal facility (EPA, 1995). It is Redstone Arsenal's goal to select a remedy

that is compliant with CERCLA and RCRA regulations and one which limits duplication of

closure efforts. The Army and EPA select the remedial action with concurrence from ADEM

and after consideration of public acceptance of the remedial action in accordance with CERCLA

and the NCP.

2.4.2 Scope of Problems Addressed by RSA-196 Response Action

The action or scope covered by the response action at RSA-196 is surface media. No problems

have been identified in soil or in soil vapor at RSA-196 that require remedial action under

present and planned future industrial land uses or under hypothetical future residential uses. The

remedial action selected for RSA-196 surface media is intended as the final remedial action.

2.4.3 Relationship of Selected Remedy to Response Action or Other Operable Units

Several CERCLA and RCRA sites are located within and south, west, and north ofRSA-196 in

the southeastern quadrant of Redstone Arsenal; 25 CERCLA and RCRA sites lie within 1,000

feet of the RSA-196 boundary (Figure 2). The vast majority of nearby sites are known or

suspected sources of perchlorate and/or VOC contamination. Commingled perchlorate and VOC

contaminant plumes are present in groundwater under much of the southeastern quadrant of the

Arsenal, including under RSA-196. The RI report for RSA-196 concluded that the source of

TCE appears to be mostly from historical surface media sites outside of the RSA-196 boundary.

These surface media contaminant sources are currently being investigated under separate

RIsfFSs for other surface media sites. RSA-196, however, has likely been a historical source of

perchlorate contamination to groundwater, particularly in the area of Building 737317374 and its

associated ejecta cones from site rocket motor and propellant detonation testing (Shaw, 2009a).

Groundwater under RSA-196 and the rest of the southeastern quadrant of Redstone Arsenal will

be investigated and evaluated as part of the RIfFS effort for groundwater site RSA-146.

2.5 Site Characteristics

The 4.2-acre site is located within an industrialized portion of Redstone Arsenal that was most

recently used for the production of rocket motors. The site is not fenced. Two buildings

(Building 737317374 and Building 7346) lie within the site boundary. The site is accessed by

Blue Jay Road or Sandpiper Road. The site occupies a relatively flat, slightly elevated area


between the Huntsville Spring Branch and the Tennessee River. The site has no permanent

surface water or aquatic habitats within the site boundary. RSA-196 does not fall within the 100

year floodplain.

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 3 shows the geologic and

hydrogeologic setting ofRSA-196. The CSM shows these areas relative to major surface and

subsurface features at the site.

The main components of the CSM presented on Figure 3 include the following:

• The site originated from rocket motor testing activities (rocket motor and propellant detonation testing) and was used as a cleaning facility for propellant mixing and casting tools. Based on the site history, the area was suspected to be impacted by VOCs, perchlorate, and nitroaromatic compounds. Explosions during rocket motor testing blew particles of perchlorate and aluminum into the field on the north end of the site.

• The southern boundary ofRSA-196 is generally defined by the crest ofa tall earthen blast berm, which was designated to confine materials released during testing activities on the large concrete pad east of Building 7373/7374. South of Blue Jay Road, the eastern boundary includes the former waste storage pad at the demolished Building 7346A (RCRA site RSA-161); the western boundary includes a drainage ditch which receives discharge from the industrial drain and sump at Building 7373/7374.

• Site-related contaminants, including VOCs, nitroaromatics, and perchlorate, were detected in surface and subsurface soil at RSA-196. The highest concentrations of perchlorate in soil fit with the projected "ejecta" cones for the rocket motor testing conducted north of Building 7373/7374.

• No principal threat waste or low-level threat waste (EPA, 1991a) is present at RSA-196.

• Sampling for potential VOCs in soil vapor was conducted beneath Building 7373/7374. TCE concentrations exceeded the soil vapor screening value, but the risk assessment concluded that TCE vapor posed no unacceptable health risks to the current or future receptors.


• Depth to groundwater ranges from approximately 12 to 30 feet below ground surface (bgs). Like the topography, the groundwater surface is relatively flat at RSA-196. Shallow groundwater flow direction varies seasonally, but perchlorate distribution in groundwater indicates that flow is generally northward from Building 7373/7374.

• Groundwater under the site is contaminated with VOCs and perchlorate in commingled contaminant plumes. RSA-196 was a historical source of perchlorate to soil and groundwater. Many of the nearby sites are known or suspected sources of TCE and perchlorate contamination.

• Both the risk assessment and the fate and transport evaluation concluded that no contaminants present at the site pose an unacceptable risk or threat to human health or the environment.

Current and future potential human receptors evaluated for RSA-196 include groundskeepers,

construction workers, sportsmen, and trespassers, any of which might, under specific

circumstances, be exposed to site-related contamination. Additionally, a hypothetical residential

receptor has been evaluated for a future scenario. The hypothetical residential evaluation

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 LUCs would be

incurred.

• The site is maintained on a regular basis; the groundskeeper serves as a conservative surrogate for all site workers who might be exposed to surface soil. The groundskeeper, who typically cuts the grass, could be exposed to soil through incidental dermal contact, inhalation of soil particulates, or incidental ingestion. The soil at the site is covered by grass such that there would be minimal direct exposure to soils.

• A construction worker was included as a plausible receptor for evaluating subsurface soil and total soil (the combination of surface and subsurface soil data sets with starting depths of 10 feet bgs or less).

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

• The site is currently restricted from hunting, although hunting could be allowed at RSA-196 in 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 these reasons, a future sportsman was considered to be as a plausible receptor for this site.


• Groundwater exposure pathways are incomplete under current conditions because groundwater is not utilized as a potable water supply on Redstone Arsenal (Army, 2008; Shaw, 2009c, 2007a). Exposure to groundwater was evaluated in the risk assessment to meet requirements for assessing risks from multiple media cumulatively, as specified under the NCP. This assessment is needed since the current remedy in place for groundwater is only an interim remedy (EPA, 1991b).

The flora at the site is turf grasses and associated lawn weeds; however, the areas surrounding

the site are cultivated woodlands and natural wetlands. Sites at Redstone Arsenal, including

RSA-196, support a variety of terrestrial vertebrates and invertebrates. Seasonally, various

species of birds and mammals may use portions of the site as part of their larger habitat. No

areas of archeological or historical importance are present at RSA-196. The site risks are

discussed in Section 2.7.

2.5.2 Nature and Extent of Contamination

Surface soil, subsurface soil, soil vapor, and groundwater have been sampled at RSA-196 as part

of the RI and earlier studies. Sampling at RSA-196 began in 1996 and was completed in 2007.

Figure 4 shows the sample locations from the investigations conducted at the site to date.

Potential release points were sampled to determine the nature and extent of contamination at

RSA-196. The RI report (Shaw, 2009a) contains the detailed sample information, analytical

data, the screening criteria for data evaluation, and maps for the investigations conducted at

RSA-196.

EPA has published studies that estimate health and environmental risks associated with many of

the organic and inorganic compounds found in the environment at Redstone Arsenal. Analytical

data from RSA-196 were compared to EPA Region 9 preliminary remediation goals (PRG)

(EPA, 2004) to help determine the extent and magnitude of contamination at this site. PRGs

combine current human health toxicity values with standard exposure factors to estimate

contaminant concentrations in environmental media (soil, air, and water) that are considered by

EPA to be health protective of human exposures (including sensitive groups) over a lifetime. For

the purpose of visualizing contaminant distribution only, surface soil data were compared to

residential PRGs, in case the site can be released for unlimited use; and subsurface soil data were

compared to industrial PRGs because the anticipated reuse of the site is industrial. When a

contaminant exceeds its PRG, further evaluation of the potential risks posed by that contaminant

may be appropriate. Other screening criteria used to identify and determine the severity of the

contamination at Redstone Arsenal environmental sites includes the EPA soil screening levels

(SSL) (EPA, 1996), EPA Region 9 tap water PRGs or maximum contaminant levels (MCL) in


groundwater (EPA, 2004), and background screening values (BSV) specific to a site-wide data

set for metals at Redstone Arsenal (Shaw, 2003).

The following subsections summarize, by medium, the characterization of the nature and extent

of contamination encountered at RSA-I96. Details are available in the RI report (Shaw, 2009a).

2.5.2.1 Nature and Extent of Soil Contamination

Soil sample locations (surface and subsurface) were selected to target potential contamination

from rocket motor and propellant detonation testing as well as potential releases from historical

tool-cl eaning operati ons.

Surface Soil. To evaluate surface soil at RSA-I96, samples were collected from the interval

beginning at the ground surface to approximately 1 foot bgs, although a few surface soil samples

were collected from 0 to O.S feet or 0 to 1.S feet bgs. Surface soil samples were analyzed for

target analyte list (TAL) metals, VOCs, perchlorate, nitroaromatics, semivolatile organic

compounds (SVOC), cyanide, pesticides, and polychlorinated biphenyls (PCB). Figure 4 shows

the sample locations. The contaminants detected in surface soil are summarized below.

Consistent with knowledge of historical activities at RSA-I96, metals detected in site surface soil

were detected at concentrations consistent with the natural range of concentrations in soil at

Redstone Arsenal.

VOCs, including TCE and 1,1, I-trichloroethane (TCA), were detected infrequently and at very

low concentrations in surface soil. No VOCs exceeded the residential PRGs or dilution

attenuation factor (DAF) 4 SSLs.

Perchlorate was detected in 10 surface soil samples at RSA-I96. Table 2 presents a data

summary for perchlorate in surface soil. Concentrations detected in two of these samples (KI96-

HP03 and K98-SBOI) slightly exceed the DAF4 SSL (Shaw, 200Sb). However, the two

locations are separated by other locations where perchlorate was not detected or was detected at

a lower concentration. No samples exceeded the PRG for perchlorate.

Cyclotrimethylenetrinitramine or hexahydro-I,3,S-trinitro-I,3,S-triazine (RDX), a nitramine

compound, was detected in surface soil but at concentrations well below the PRG.

No SVOCs, pesticides, PCBs, or cyanide were detected in surface soil.


Subsurface Soil. To evaluate subsurface soil at RSA-196, samples were collected from 2 feet

to approximately 26 feet bgs; however, only samples collected above the water table were used

in the evaluation of nature and extent of contamination in vadose zone soils. Samples were

analyzed for TAL metals, VOCs, perchlorate, nitroaromatics, SVOCs, cyanide, PCBs, and

pesticides. Figure 4 shows the sample locations. The contaminants detected in subsurface soil

are summarized below.

As in surface soils, metals detected in subsurface soil were determined to be naturally occurring.

No VOCs exceeded screening criteria. Specifically, TCE was detected at concentrations below

the industrial soil PRG and DAF4 SSL from locations along the earthen berm southeast of

Building 7373/7374.

The observed releases of perchlorate are consistent with the CSM for this site where explosive

ejection of perchlorate-based propellants would have resulted in perchlorate in site soils.

Perchlorate was detected in subsurface soil at concentrations slightly exceeding the DAF4 SSL.

Sample locations where concentrations of perchlorate slightly exceeded the DAF4 SSL were

found to be both widely scattered and separated by other locations where perchlorate was

detected at concentrations lower than the DAF4 SSL. No subsurface soil samples exceeded the

industrial soil PRG for perchlorate.

RDX was detected at concentrations below the industrial soil PRG in samples collected 4 to 20

feet bgs at locations along the earthen berm southeast of Building 7373/7374. The observed

releases are consistent with the CSM for this site where explosion ejection of perchlorate-based

propellants would have resulted in perchlorate and RDX in site soil.

No SVOCs, pesticides, PCBs, or cyanide were detected in subsurface soil.

Soil Vapor. Vapor trapped in soil beneath Building 7373/7374 was sampled to determine

whether vapor migration of VOCs from subsurface media into overlying buildings posed

unacceptable risks to building occupants at RSA-196 currently or in the future. TCE in soil

vapor exceeded the soil vapor screening value and was further evaluated in the risk assessment.

Risk assessment results are presented in Section 2.7 of this ROD and in Section 7.2 and

Appendix J in the RI report (Shaw, 2009a).


2.5.2.2 Nature and Extent of Groundwater Contamination

Contaminant plumes ofTCE and perchlorate were observed beneath RSA-196. TCE and

perchlorate were present in small, defined areas of higher concentrations (1,100 micrograms per

liter [llglL] for perchlorate and 570 IlglL for TCE) beneath RSA-196 (Shaw, 2009a). The TCE

concentrations exceeded the MCL and the perchlorate concentrations exceeded the drinking

water equivalent level (DWEL) and health advisory level (HAL). RDX and other nitroaromatic

compounds were detected in groundwater beneath RSA-196 at concentrations above their tap

water PRGs. Metals were detected at concentrations consistent with the natural background of

metals in groundwater. The final Phase I RI for RSA-146 determined that TCE and perchlorate

have formed extensive and overlapping plumes in groundwater throughout the former Thiokol

RARE North Plant area, including under RSA-196 (Shaw, 2008). Groundwater under RSA-196

will be further investigated as part of groundwater site RSA-146 (Figure 2).

2.5.3 Fate and Transport

Potential release mechanisms and migration routes for contaminants were identified and

evaluated at RSA-196 in the RI report (Shaw, 2009a). Potential points of release include

scattered perchlorate and explosives from the rocket motor and propellant testing, as well as

leaks and spills of solvents used to clean propellant-contaminated tools and equipment. Runoff

from the exterior industrial drain could occur after storms, and the runoff could enter the unlined

ditch just south of Blue Jay Road. Because of the flat land surface, most contaminant movement

would have been downward through the soil column. The conclusions of this evaluation for

VOCs, nitroaromatic compounds, and perchlorate are as follows:

• No concentrations ofVOCs, including TCE, at RSA-196 exceed DAF4 SSLs and do not pose a threat to groundwater.

• It is believed that RSA-196 was the source ofRDX and nitroaromatic compounds detected in groundwater at the site. However, no concentrations of nitroaromatic compounds remain in soils that would continue sourcing to groundwater.

• Perchlorate is present in surface and subsurface soils and in the past RSA-196 has likely been a source of perchlorate to groundwater. Further evaluation through leachability tests and modeling has determined that there is insufficient perchlorate mass existing in site soil to pose an ongoing threat of sourcing to groundwater (see Section 2.7.3 in this document for further discussion of perchlorate sourcing to groundwater) .

2.6 Current and Potential Future Land and Resources Use

This section presents current and future land and groundwater uses for this site.


2.6.1 Current and Future Land Use

Current Land Use. The current land use for RSA-196 is industrial, which is designated as

manufacturing and production (Army, 2006). Building 737317374 is currently empty. Building

7346 is used for offices for industrial and administrative staff at Northrop Grumman.

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

RSA-196. Recreational hunters are authorized entry onto 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 (e.g., RSA-196) are noted on the maps. Game wardens and other security personnel

routinely enforce the recreational use regulations on Redstone Arsenal. Where practical, the

Army has restricted entry into environmental sites by fencing them and/or by placing warning

signs at key entry points per the Site Access Control program (Army, 2008). The area within the

RSA-196 boundary is not fenced; Building 737317374 and the surrounding land are physically

accessible to anyone authorized to be at Redstone Arsenal.

Future Land Use. Future land use in the area ofRSA-196 is designated as research,

development, testing, and evaluation (Army, 2006). 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-196 in the future.

2.6.2 Current and Future Groundwater Use

Current Groundwater Use. Groundwater under RSA-196 is not currently used for human

consumption or for any nonpotable uses. The Tennessee River is the source of potable water for

both consumption and the majority of nonpotable uses on Redstone Arsenal. Local residents and

Arsenal workers receive their potable water from the Huntsville Utilities, where water is derived

from the Tennessee River. The Tennessee River is more than two miles to the south ofRSA

196. Redstone Arsenal's installation-wide groundwater IROD prevents the current use of

groundwater under the Arsenal for potable water purposes and ensures that any nonpotable uses

of groundwater are reviewed and evaluated by the Army prior to being permitted (Shaw, 2007a).

An installation-wide groundwater LUC remedial design document has been prepared to

document the LUCs to be implemented for groundwater (Shaw, 2009c).


Future Groundwater Use. Under the provisions of the Army's groundwater IROD, future

groundwater resources beneath RSA-196 or elsewhere on Redstone Arsenal may not be

developed for potable purposes and groundwater withdrawals for nonpotable uses must be

managed as previously discussed. The LUCs will remain in effect until remedies are selected in

the final RODs for the various groundwater sites (e.g., RSA-146 groundwater site) within

Redstone Arsenal. Thus, the IROD (Shaw, 2007a) and the LUC remedial design document

(Shaw, 2009c) apply to any groundwater site for which the final remedy has not been selected in

a ROD.

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-196 (Shaw, 2009a). These risk assessments support the need for No Action at this site. A

summary of the aspects of the BHHRA and SLERA that support the determination that no

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

presented in Sections 2.7.1 and 2.7.2, respectively, of this document. The complete BHHRA and

SLERA can be found in Appendices J and K, respectively, of the RI report for RSA-196 (Shaw,

2009a).

2.7.1 Baseline Human Health Risk Assessment

The BHHRA evaluated human health exposure to soils from ground surface to 10 feet bgs. The

BHHRA did not identify unacceptable risks for any receptor from exposure to surface media at

RSA-196. To reach this conclusion, the BHHRA calculated the likelihood of health problems

occurring if no cleanup actions are taken at this site. The BHHRA followed a four-step process

to estimate the baseline risk for human health: 1) 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 risks and noncarcinogenic hazards and a discussion

of the uncertainty in the risk estimates.

A summary of these steps of the BHHRA follows.


2.7.1.1 Step 1 - Identify Chemicals of Potential Concern

A total of 6 of the 42 chemicals detected in site soil 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. A hypothetical medium called total soil was created by

combining the surface and subsurface soil sample data from samples with starting depths of 10

feet bgs or less into one data set to evaluate the potential for subsurface soil to be brought to the

surface during construction or excavation so that direct contact is plausible. COPCs for surface

soil, subsurface soil, and total soil can be found in the RI report in Table 7-1 and in Appendix J,

Tables J-3 as through J-5, respectively (Shaw, 2009a). Estimates of the exposure point

concentrations used for all COPCs can be found in Appendix J, Table J-7 of the RI report (Shaw,

2009a).

As presented in Attachment 2 of Appendix J of the RI report, the maximum detected

concentrations of VOCs in soil vapor samples were used to evaluate whether soil vapors

originating from soil or groundwater contamination could potentially pose unacceptable risks to

an indoor worker exposed in Building 737317374 or a resident if residential buildings were

constructed on RSA-196 in the future (Shaw, 2009a).

2.7.1.2 Step 2 - Conduct an 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 ofRSA-196.

The current land use ofRSA-196 is manufacturing and production. Its future industrial land use

has been designated as research, development, testing, and evaluation (Army, 2006). Because

there is currently no administrative control prohibiting site development for residential purposes,

risks to hypothetical residential receptors were evaluated. The future hypothetical residential

evaluation can be used to demonstrate that unrestricted land use is appropriate as part of site

closure. This evaluation also 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 LUCs would be incurred.

The following paragraphs present a brief summary of the exposure pathways evaluated in the

BHHRA. A more thorough description of exposure pathways evaluated can be found in

Appendix J, Section J4.2.2 of the RI report (Shaw, 2009a).


Five types of human receptors were quantitatively evaluated in the exposure assessment that was

performed as part of the quantitative risk assessment for RSA-196. 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 considered

recreational receptors. The sportsman is considered to be a future receptor only, since hunting is

not currently allowed at the site. A hypothetical residential receptor was evaluated under a

potential future site use which assumes that houses are built on RSA-196. An additional

receptor, a future hypothetical indoor commercial worker, was used in the evaluation of potential

risks posed by indoor air, contaminated via the vapor intrusion transport pathway. Indoor air

contamination may occur when VOCs found in soil and groundwater volatize and are transported

into buildings.

Intake of chemicals from potential exposure to surface soil was determined for all human health

receptors except the hypothetical indoor commercial worker. Additionally, the intake of

chemicals found in subsurface soil was determined for the construction worker possibly exposed

during excavation or trenching operations. It was also assumed that the future groundskeeper,

construction worker, and hypothetical on-site residential receptor would be exposed to

overburden groundwater developed as a source of potable water in the future and to total soils.

The intake of chemicals found in the total-soils medium was determined for the future

groundskeeper, future construction worker, and future hypothetical residential receptors.

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

contacting (touching), ingesting (eating), or inhaling (breathing in) site media. For exposure to

soil, all three exposure routes were evaluated for the construction worker, groundskeeper,

sportsman, and trespasser receptors. Hypothetical future residential adults and children were

assumed to only come in contact with soil through ingestion and dermal contact because, in a

residential setting, soil 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 residents were assumed to contact

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

residents may inhale VOCs in groundwater while showering. The VOCs in soil vapors which

have been transported into indoor air, future indoor commercial workers and future hypothetical

residential receptors were evaluated for inhalation exposure.

The VOCs TCE, benzene, carbon tetrachloride, and chloroform were identified as COPCs 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 vapor


samples collected from one location above the highest groundwater concentration found onsite.

A three-tiered screening-level vapor intrusion evaluation was performed. The Johnson and

Ettinger vapor intrusion model was used to calculate indoor air concentrations based on soil

vapor sample results (Johnson and Ettinger, 1991). Indoor air concentrations were calculated for

a worker in Building 737317374 and for a hypothetical future residential on-site house.

2.7.1.3 Step 3 - Conduct a 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 classified as

carcinogens may also elicit noncarcinogenic adverse health effects; these effects are evaluated 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 J, Chapter J5.0, and presented in Tables J-I0,

J-ll, and J-12 of the RI report (Shaw, 2009a).

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 (RID) for noncarcinogen compounds have been developed by EPA and

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

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

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

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

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

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

EPA's National Center for Environmental Assessment evaluation ofTCE (EPA, 2001) and

California Environmental Protection Agency's (CalEPA) guidelines for describing cancer

potency factors (CalEPA, 2002). Attachment 2 of Appendix J of the RI report (Shaw, 2009a)

presents the toxicity assessment performed for the vapor intrusion evaluation.

2.7.1.4 Step 4 - Characterize the Risks

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

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

exposure pathway by multiplying 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 1 x 10-4 to 1 X 10-6 (between a 1-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 1-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 Tier 1 Risk Managers may decide is acceptable on a case-by-case

basis. ADEM considers a cumulative cancer risk of 1 x 10-5 (1 in 100,000) to be a level which

triggers identification of chemicals of concern (COC) (ADEM, 2007).

For noncarcinogens, the potential 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 RID (e.g., oral RID 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.

For risk management purposes under CERCLA, a total cancer risk of 1 x 10-6 (1 in 1,000,000) is

a point of departure below which cancer risks are considered to be insignificant (EPA, 1990).

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

risks exceeding 1 x 10-6 (or an excess lifetime cancer risk of 1 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

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, Redstone Arsenal Tier 1 Risk Managers may refine the list of COCs selected for

action based on site-specific considerations. Final identification of COCs may occur during a

removal action or as part of the evaluations performed during the FS for a site.

Following the quantitative calculation of risk during the evaluation of problems potentially

warranting action for soil, the metals aluminum, arsenic, chromium, manganese, and vanadium

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 background-related metals were removed from the risk

assessment. These results are presented in Table 3.


As shown in Table 3, potential risks from surface soil and subsurface soil exposure under the

current land-use scenarios were well below EPA's risk management range for carcinogens

because no carcinogenic chemicals were selected as COPCs at this site once background-related

metals were removed. The HIs for noncarcinogens did not exceed EPA's target of 1 for any

target organ.

Risks calculated for future receptors based on exposure to surface soil, subsurface soil, or total

soil were also below EPA's risk management range for carcinogens. The HIs for noncarcinogens

for future receptors also did not exceed EPA's target of 1 for any target organ. As a result, no

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

Risks from exposure to groundwater were also characterized in this BHHRA to ensure that

cumulative risk requirements of the NCP were met. The risks to a groundskeeper and future

hypothetical residential receptor from exposure to groundwater alone, and from exposure to soil

and groundwater on a cumulative basis, were found to exceed 1 x 10-5, the risk threshold

established by ADEM. Noncancer HIs exceeded 1 for all future receptors from exposure to

groundwater alone, and from exposure to soil and groundwater on a cumulative basis. However,

RSA-196 is considered a surface media site, and potential risks from exposure to groundwater

from this site will be addressed with groundwater site RSA-146. In the meantime, LUCs

selected in the final installation-wide groundwater IROD preclude the use of the installation's

groundwater as a potable water source and ensure that the nonpotable uses of groundwater are

managed to protect public health (Shaw, 2007a).

Results of the vapor intrusion evaluation are presented in Table 4. Risks from VOCs present in

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

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

structure were assessed. In Table 4, risks from exposure to modeled concentrations of benzene,

carbon tetrachloride, chloroform, or 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 slope factors for VOCs were used.

As can be seen in Table 3, all cumulative risk estimates for all current and future receptors

exposed to soil fell below EPA's risk management range and below the ADEM trigger level of 1

x 10-5 (1 in 100,000) (ADEM, 2007), which is interpreted to mean that there are no chemicals in

soil contributing to unacceptable risk for any receptor at RSA-196.


2.7.1.5 Summary of the Baseline Human Health Risk Assessment

The BHHRA concluded that no unacceptable risk to human health is posed by the contaminants

in the surface media at RSA-196. No contaminants in surface soil, subsurface soil, or total soil

have been identified as COCs warranting action based on the results of the conservative exposure

scenarios in the BHHRA. Chemicals in groundwater (primarily TCE and perchlorate) do pose a

human health threat if ingested, an activity precluded by LUCs implemented in accordance with

Redstone Arsenal's installation-wide groundwater IROD (Shaw, 2007a) and LUC remedial

design document (Shaw, 2009c). These chemicals are being addressed with the RSA-146

groundwater site RI. Risks to an indoor worker in Building 737317374 and a hypothetical future

residential receptor from the vapor intrusion pathway do not exceed acceptable levels. No COCs

were selected for RSA-196, based on the results of the BHHRA.

2.7.2 Screening-Level Ecological Risk Assessment

The SLERA for RSA-196 evaluated threats to ecological receptors from exposure to surface soil

from 0 to approximately 1 foot bgs. The SLERA did not identify any contaminants in surface

soil warranting action for ecological receptors. To reach this conclusion, the SLERA was

completed in three steps, which are discussed below.

2.7.2.1 Step 1 - Screening-Level Problem Formulation and Toxicity Assessment

The primary 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 adversely impacted when exposed to site-related chemicals at RSA-196.

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, and other animals.

No special-status species were found to occur at this site, though it is possible that the peregrine

falcon could be an occasional visitor. Similar to the BHHRA, chemicals found in site surface

soil at concentrations above federal and state risk-screening levels (and BSVs for metals) were

identified as chemicals of potential ecological concern (COPEC).

2.7.2.2 Step 2 - Screening-Level Exposure Estimate and Risk Calculation

Chemicals initially selected as COPECs in surface soil included 18 metals, perchlorate, and

RDX. Tables K-2 and K-3 of Appendix K of the RI report (Shaw, 2009a) present the results of

the selection of COPECs for surface soil.


2.7.2.3 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: exposure assessment, toxicity assessment, and

risk characterization. The exposure assessment was based on measured concentrations of

COPECs in site surface soil. These concentrations were used directly to assess the potential for

adverse impacts to plants and soil invertebrates. Food-chain dose calculations were performed

using appropriate bioaccumulation factors for mammals and birds which feed in the terrestrial

area. Metals that did not exceed BSVs were excluded from these analyses. For food-chain

receptors, doses of chemicals were developed 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 a 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, a potential adverse impact may occur for particular receptors. HQ values over 1 were

further evaluated using weight-of-evidence criteria such as spatial distribution of contaminants.

Additionally, the small size of this site minimizes any potential for impacts to populations of

ecological receptors. The details of this weight-of-evidence evaluation are presented in Chapter

7.0 and Appendix K of the RI report (Shaw, 2009a). Based on this analysis, no chemicals were

identified having the potential for posing adverse impacts to populations of non-special-status

species that use this site. As such, no chemicals in surface soil were determined to warrant

further evaluation for ecological receptors (Table 5).

2.7.3 Sourcing to Groundwater Summary

The fate and transport evaluation presented in Chapter 6.0 of the RI report concluded that no

chemicals present in site soil, including perchlorate and TCE, pose an unacceptable threat to

groundwater from the soil-to-groundwater migration pathway (Shaw, 2009a). TCE and other

VOCs were detected in soil at concentrations below their DAF4 SSLs and were determined not to

pose an ongoing threat to groundwater. Perchlorate was initially identified as a chemical

requiring further evaluation for potential ongoing sourcing to groundwater based on conservative

screening by comparing the maximum detected concentration of perchlorate from individual

samples to the DAF4 SSL. Further evaluation of the soil-to-groundwater transport pathway for

perchlorate was conducted following this initial screening. This evaluation included performing

site-specific measurements of perchlorate leachability from site soil using EPA's synthetic

precipitation leaching procedure (SPLP) and secondly, conducting modeling for leachability


using the VLEACH model coupled with a numerical analysis of plume attenuation. The results

are summarized below and details can be found in the RI report (Shaw, 2009a).

• Soil samples for SPLP analysis were collected from the soil boring where perchlorate concentrations exceeded the DAF4 SSL in the greatest number of samples (depth intervals). The leachate results from the SPLP analysis did not exceed the target soil leachate concentration of 60 IlglL. Therefore, the current site soil concentrations of perchlorate are not sufficient to form a plume of perchlorate in groundwater greater than the DWEL (24.5 IlglL) or HAL (15 IlglL).

• VLEACH modeling (Harter, 2006) indicated that leaching from the one-half acre area where perchlorate was detected in soil at concentrations above the DAF4 SSL would not result in groundwater concentrations greater than the HAL.

• Attenuation modeling using the Buscheck and Alcantar (1995) equation was performed to determine whether the mass of residual perchlorate in soil was sufficient to appreciably prolong a groundwater remedy for RSA-146. Based on the results, the perchlorate mass remaining in soil at RSA-196 will not prolong the recovery ofRSA-146 groundwater to the HAL (15 IlglL) beyond a timeframe which is reasonable for groundwater restoration at Redstone Arsenal.

The fate and transport evaluation concluded that no chemicals present in RSA-196 soil pose an

unacceptable threat to groundwater from the soil-to-groundwater migration pathway.

2.7.4 Risk Summary

The BHHRA and SLERA concluded that no unacceptable risk to human health or the

environment is posed by surface media at this site. No contaminants in surface media 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, an activity

precluded by LUCs in the Redstone Arsenal groundwater IROD (Shaw, 2007a) and the LUC

remedial design document (Shaw, 2009c). Risks posed by chemicals present in groundwater will

be addressed as part of the RI for the RSA-146 groundwater site. No contaminants in site soil

pose an ongoing threat of sourcing to groundwater at RSA -196.

Surface media at RSA-196 have been found to pose no unacceptable risks to human health or the

environment. Based on these results, it is the Army's current judgment that no remedial action is

necessary at RSA-196 to ensure protection of public health or welfare or the environment from

actual or threatened releases of hazardous substances into the environment.


2.7.5 Basis for Action

A No-Action remedy has been selected for RSA-196 surface media. Groundwater will be further

investigated during the RSA-146 groundwater site RI. The characterization that was performed

at this site supports this remedy selection (see Section 2.5, 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 2.5.3, Fate and Transport and Section 2.7.3, Sourcing

to Groundwater Summary). This ROD documents that the RSA-196 surface media do not pose

unacceptable risks to human health or the environment under current or future industrial or future

unrestricted exposure scenarios (see Section 2.7, Site Risks). Current guidelines from EPA and

ADEM state that "unrestricted use," including residential land use, must be considered in a No

Action remedy decision. The risk assessments performed support the finding that surface media

at RSA-196 are available for unrestricted use.

Several rounds of sampling have been performed at this site for all media, including the

overburden groundwater. Evaluation of groundwater does indicate that the groundwater beneath

RSA-196 is contaminated, and exposure to contaminants in groundwater was determined to pose

a human health threat. However, the installation-wide groundwater IROD precludes the use of

the installation's groundwater as a potable water source and ensures that the nonpotable uses of

groundwater are managed to ensure protection of public health (Shaw, 2007a). Because

groundwater contamination has been identified at RSA-196 and elsewhere within the RARE

North Plant area, groundwater will be more fully characterized and addressed with groundwater

site RSA-146.

In summary, a No-Action remedy has been selected as the final remedy for surface media at

RSA-196. No Action (CERCLA or RCRA) is required for the surface media at the site,

including long-term monitoring or LUCs, because the site poses no unacceptable risks to human

health or the environment. No additional evaluation of remedial alternatives is required when a

No-Action remedy is selected for a site. A separate ROD for the RSA-146 groundwater remedy

will present the remedial actions selected for groundwater.

2.8 Documentation of Significant Changes

No significant change has been made to the Preferred Alternative presented in the SBIPP (Shaw,

2009b).


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 SBIPP (Shaw, 2009b). 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-196

SBIPP (Shaw, 2009b) and the Army's responses to the comments. However, no comments were

received during the 30-day public comment period that began on July 2,2009 and ended on

August 1, 2009. A meeting to discuss the remedial alternatives for RSA-196 was not requested

by the public.

No Action for surface media at RSA-196, which was presented as the Preferred Alternative in

the SBIPP (Shaw, 2009b), is the Selected Remedy for RSA-196 surface media. This decision is

based on the Administrative Record file for RSA-196, including the site characterization

documents, risk assessments, 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. The Army and EPA have selected the No Action remedy, and ADEM

has concurred with this remedy.


4.0 References

Alabama Department of Environmental Management (ADEM), 2007, Alabama Risk-Based Corrective Action Guidance Manuel, June.

Buscheck, T. E. and C.M. Alcantar, 1995, Regression Techniques and Analytical Solutions to Demonstrate Intrinsic Biodegradation, in Intrinsic Bioremediation, Hinchee, RE., Wilson, IT., and Downey, D.C., eds., Battelle Press, Columbus, Ohio.

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

CH2M Hill, 1998, Draft-Final Report ofFindings, RARE North Plant Phase II EBS, prepared for US. Army Corps of Engineers, Mobile District, April.

Conestoga-Rovers and Associates, 1996, Phase I Environmental Baseline Study, Redstone Arsenal Rocket Engine Facility North Plant, Madison County, Alabama, prepared for Thiokol Corporation, November.

Harter, T., 2006, Vadose Zone Leaching Model, Version 2.2c, May, University of California, Davis, http://groundwater. ucdavis. edu/vadose zone98/readme. txt.

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

Shaw Environmental, Inc. (Shaw), 2009a, Final Remedial Investigation Report, RSA-196, Test Stand and Cleaning Building, Operable Unit 10, Redstone Arsenal, Madison County, Alabama, Revision 1, prepared for the US. Army Corps of Engineers, Savannah District, June.

Shaw Environmental, Inc. (Shaw), 2009b, Final Statement ofBasis/Proposed Plan for Surface Media at RSA-196, Test Stand and Cleaning Building, Operable Unit 10, Redstone Arsenal, Madison County, Alabama, prepared for the US. Army Corps of Engineers, Savannah District, June.

Shaw Environmental, Inc. (Shaw), 2009c, Final Installation-Wide Groundwater Land-Use Control Remedial Design, Redstone Arsenal, Madison County, Alabama, Revision 1, prepared for the US. Army Corps of Engineers, Savannah District, May.

Shaw Environmental, Inc. (Shaw), 2008, Final RSA-146 Phase I Remedial Investigation Report, Redstone Arsenal, Madison County, Alabama, prepared for the US. Army Corps of Engineers, Savannah District, April.

Shaw Environmental, Inc. (Shaw), 2007a, Final Interim Record ofDecision, Interim Remedial Action for Installation- Wide Groundwater, Redstone Arsenal, Madison County, Alabama, prepared for the US. Army Corps of Engineers, Savannah District, September.


Shaw Environmental, Inc. (Shaw), 2007b, Redstone Arsenal Fact Sheet 25, Regrouping of Redstone Arsenal Installation Restoration Program Sites for Streamlining Site Cleanup, Environmental Management Division, prepared for the US. Army Corps of Engineers, Savannah District, October.

Shaw Environmental, Inc. (Shaw), 2006a, RSA-196 Historical Summary, Operable Unit 10, Redstone Arsenal, Madison County, Alabama, submitted and presented to Redstone Arsenal Tier 1 Team, October.

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

Shaw Environmental, Inc. (Shaw), 2005a, Draft RSA-146 Potential Source Area Investigation, Redstone Arsenal, Madison County, Alabama, prepared for the US. Army Corps of Engineers, Savannah District, January.

Shaw Environmental, Inc. (Shaw), 2005b, Preliminary Remediation Goals for Perchlorate: Revision 1, prepared for the US. Army Corps of Engineers, Savannah District, March.

Shaw Environmental, Inc. (Shaw), 2004, Draft Remedial Investigation Report, RSA-098, Solvent Degreaser Distiller at Building 7346, Operable Unit 10, Redstone Arsenal, Madison County, Alabama, prepared for the US. Army Corps of Engineers, Savannah District, November.

Shaw Environmental, Inc. (Shaw), 2003, Methodology for the Comparison ofSite and Background Data, Redstone Arsenal, Madison County, Alabama, prepared for the US. Army Corps of Engineers, Savannah District, March.

US. Army Garrison - Redstone (Army), 2008, Redstone Arsenal Environmental Site Access Control Program, June.

US. Army Garrison - Redstone (Army), 2006, Real Property Master Plan Digest.

US. Environmental Protection Agency (EPA), 2004, Preliminary Remediation Goals Table, EPA Region 9 PRG, San Francisco, California, online.

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

US. Environmental Protection Agency (EPA), 1996, Soil Screening Guidance, Technical Background Document, Office of Solid Waste and Emergency Response, EP A/540IR-951128, May.

US. Environmental Protection Agency (EPA), 1995, Improving RCRAICERCLA Coordination at Federal Facilities, OSWER Directive 9272.0-22, December.


US. Environmental Protection Agency (EPA), 1991 a, A Guide to Principal Threat and Low Level Threat Wastes, 9380.3-06FS, Office of Solid Waste and Emergency Response, November.

US. Environmental Protection Agency (EPA), 1991b, Role ofthe Baseline Risk Assessment in Superfund Remedy Selection Decisions, Directive 9355.0-30, Office of Solid Waste and Emergency Response, April.

US. Environmental Protection Agency (EPA), 1990, 40 CFR Part 300, "National Oil and Hazardous Substances Pollution Contingency Plan, Final Rule," Federal Register 55(46):86668865.


o Sump Sample

Monitoring Well

Hydropunch

Figure 4

RSA-196 Sample Locations

u.s. Army Corps of Engineers Redstone Arsenal Madison County, Alabama Contract No. OACA21-96-0-0018 ~

~ StiaW'" Shaw Environmental, Inc.

APPENDIX A

GLOSSARY OF TERMS


GLOSSARY OF TERMS

Administrative Record file - The body of reports, official correspondence, and other documents that establish the official record of analysis, cleanup, and final closure of a CERCLA or RCRA site.

Background Screening Values - Naturally occurring concentrations of inorganic elements (metals) that are present in the environment and have not been altered by human activity.

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

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

Chemicals of Concern (COC) - 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 1 in 1,000,000) or an HI = 0.1 may be selected as COCs. These are chemicals that significantly contribute to unacceptable risks for a pathway in an exposure model for a hypothetical receptor (e.g., a child that resides on the site).

Chemicals of Potential Concern (COPC) - Chemicals of potential concern are chemicals found at the site at concentrations above federal and state risk-based screening levels for human health (and background screening values for metals). Chemicals with concentrations above these levels are further evaluated in the BHHRA.

Chemicals of Potential Ecological Concern (COPEC) - Chemicals of potential ecological concern are chemicals found at the site at concentrations above ecological chemical- and mediaspecific generic effect levels. Chemicals with concentrations above these levels are further evaluated in the ecological risk assessment.

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), 1980 - A federal law passed in 1980 and modified in 1986 by the Superfund Amendments and Reauthorization Act. The Acts created a special tax that goes into a Trust Fund, commonly known as Superfund, to investigate and cleanup abandoned or uncontrolled hazardous waste sites. The Army is funding the investigation and cleanup ofRSA-196.

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

Dilution Attenuation Factor 4 (DAF4) Soil Screening Levels (SSL) - DAF4 SSLs are soil threshold concentrations calculated using methodology developed by EPA below which there is not a concern for migration of residual contaminants in soil to groundwater at concentrations above maximum contaminant levels or risk-based screening concentrations. Dilution attenuation factors represent the reduction in the contaminant concentrations through soil. A DAF 1 means there is no dilution or attenuation through the soil column. A high DAF value means there is a

KN9!RSA1196!RODlFinallF-196 ROD.doc/S/5/2009 1245 PM A-I

high degree of dilution or attenuation. The Army in conjunction with EPA and ADEM has determined that a DAF 4 is appropriate for initial screening for protection of groundwater from contamination in soil at Redstone Arsenal.

Drinking Water Equivalent Level (DWEL) - A lifetime exposure concentration protective of adverse, non-cancer health effects. The DWEL assumes all of the exposure to a contaminant is from drinking water.

Exposure - Contact of an organism with a chemical or physical agent. Exposure is quantified as the 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 of saturation. Groundwater is often used as a source of drinking water via municipal or domestic wells. Groundwater that comes to the earth's surface, such as streams and springs, is considered surface water. At Redstone Arsenal, the groundwater is not a source of drinking water and is currently protected from consumption by an installation-wide groundwater IROD.

Groundwater Site - Constitutes a sub-watershed defined at Redstone Arsenal from a site-wide hydrogeologic investigation. Thirteen groundwater sites have been defined at Redstone Arsenal. Each groundwater site will proceed through a separate CERCLA investigation to get to closure of the site.

Health Advisory Level (HAL) - EPA issued an interim health advisory in January 2009 to help state and local authorities in addressing local contamination by perchlorate in drinking water. The level set for perchlorate (15 IlglL) is based on the reference dose recommended by the National Research Council of the National Academy of Sciences.

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

Low-Level Threat Waste - Source materials that can be reliably contained or present only a low risk to human health or the environment should exposure occur. These waste materials have low toxicity, low mobility, and are near health-based risk levels.

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

National Oil and Hazardous Substances Pollution Contingency Plan (NCP) - The Federal government's blue print for responding to oil spills and hazardous substance releases.

Nonpotable Water - Water deemed unsafe for human consumption or is of questionable potability. Nonpotable water has other uses such as irrigation, firefighting, controlling dust, filling for ponds and fountains, making concrete, drilling fluids, etc.

KN9!RSA1196!RODlFinallF-196 ROD.doc/S/5/2009 1245 PM A-2

Operable Unit (OU) - A discrete portion of a remedial response that comprises an incremental step toward addressing site problems. It can be a geographic area and can address an environmental medium at the site (e.g., groundwater). At Redstone Arsenal, OUs are defined based on similarities in historical processes or functions which have resulted in site releases of a similar nature. Twenty OUs have been designated at Redstone Arsenal.

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

Potable Water - Water of sufficient quality to serve as drinking water even though it may not be used for such purposes. Meets stringent requirements for sanitation and chlorination.

Preliminary Remediation Goals (PRG) - Preliminary remediation goals combine current human health toxicity values with standard exposure factors to estimate contaminant concentrations in environmental media (soil, air, and water) that are considered by EPA to be health protective of human exposures (including sensitive groups) over a lifetime. When a contaminant exceeds its PRG, further evaluation of the potential risks posed by that contaminant may be appropriate.

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

Proposed Plan (PP) - A public document that provides a brief analysis of remedial alternatives under consideration for the site/operable unit and presents the Preferred Alternative. Public review and comment are actively sought on the PP.

Record of Decision (ROD) - A legal document that presents the selected remedial action for the site. The ROD is based on information and technical analysis generated during the remedial investigation, risk assessments, feasibility study, and consideration of public comments and community concerns.

Remedial Investigation (RI) - A study designed to gather data needed to determine the nature and extent of contamination at a Superfund site. The RIs at Redstone Arsenal include BHHRAs and SLERAs.

Resource Conservation and Recovery Act (RCRA), 1976 - A federal law that established a regulatory system to track hazardous substances from their generation to disposal. The law requires safe and secure procedures to be used in treating, transporting, storing, and disposing of hazardous substances. RCRA is designed to prevent the creation of new, uncontrolled hazardous waste sites.

Responsiveness Summary - A summary of oral and/or written comments received during the SBIPP 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 baseline ecological risk assessment in which conservative concentrations of site chemicals are quantitatively compared to chemical- and media-specific generic effect levels. Those chemicals


selected as COPECs are further refined through quantitative comparison to chemical- and species-specific effect doses, as well as qualitative examination. Those chemicals identified as COCs may be investigated further, remediated, or left in place per the decision of the risk managers.

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

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

Subsurface Soil - Soil that is 1 foot below ground surface to the water table. Only subsurface soil to 10 feet below ground surface is included in the BHHRA.

Surface Media - The surface media at RSA-196 includes surface soil, subsurface soil, and soil vapor.

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

Trichloroethene (TeE) - TCE is a colorless or blue liquid with an odor similar to ether. It is man-made and does not occur naturally in the environment. TCE was once commonly used to remove oils and grease from metal parts.


TABLES


Table 1

Historical Building Use RSA-196, Operable Unit 10

Redstone Arsenal, Madison County, Alabama

Current Building

Historical Building

Built Status HISTORICAL USE 1 CURRENT USE 2

(post-1957) (pre-1957) (year) (2006) 1945 1950s - 1976 1983 1986 1988 - 1991 2001 2007

7373 8-520 1945 Existing Static Testing Parts Cleaning

Static Testing Test Bay Static Testing Parts Cleaning

Fix & Clean Test Bay Vacant, Unused

7374 8-520-1 1951 Existing Did Not Exist Static Test Control Control Static Test Control Inactive Control Building 1 Vacant, Unused

7346 3 Did Not Exist

1987 Existing Did Not Exist Did Not Exist Did Not Exist Did Not Exist Case Filling/Preparation Chlorinated Solvent Distillation

Case Filling/Preparation Chlorinated Solvent Distillation

Administrative Offices Northrop Grumman

7346A Did Not

Exist 1988 Demolished Did Not Exist Did Not Exist Did Not Exist Did Not Exist

Waste Storage Shed Did Not Exist Does Not Exist

1 Historical use documented in Army building indices.

2 Current use per verbal communications with the Army and field observations.

3 Building 7346 was built in 1987 and is unrelated to historical activities at Buildings 7373 and 7374. The RSA-196 site boundary encompasses Building 7346 because the remedial investigation tested the hypothesis that perchlorate detected in soil during the RSA-098 remedial investigation is derived from historical activities at Building 7373.

KN9\RSA\ 1 96\RCO\Fin a ~196 RCOTab1.xlsm\8uilding Use\8/5/2009\220 PM

Table 2

Soil Data Summary for Perchlorate RSA-196, Operable Unit 10


Frequency Detected Concentrations Exposure Basis of of Minimum Maximum Arithmetic 95% Point Exposure Point

Chemical Unit Detection Value VQ Value VQ Average UCL Concentration Concentration Surface Soil Perchlorate mg/kg 10 /34 0.00031 J 0.043 8.55E-03 Not a COPC in Surface soil

I I Total Soil Perchlorate mg/kg 45 /95 0.00029 J 0.27 1.84E-02

I . I. Not a COPC In Total sOil

I I

J - The compound/analyte was positively identified; the reported result is the estimated concentration of the compound/analyte detected in the sample analyzed. 95% UCL - 95 Percent upper confidence limit. VQ - Validation qualifier. COPC - Chemical of potential concern. mg/kg - Milligrams per kilogram.

KN91RSAI1961ROOIFinal1196 ROD Tab2.3.4.5xlsmITab 218/5/20091158 PM

Table 3

Total Cancer Risks and Noncancer Hazards for Receptors

Without Background-Related Metals 1

RSA-196, Operable Unit 10 Redstone Arsenal, Madison County, Alabama

Current Site Use a Future Site Use b

Receptors Soil Soil Groundwater Total Risk Vapor Intrusion

CANCER RISK

Industrial Receptors: Groundskeeper (Conventional) C NQ NQ 2.20 x 10-5 2.20 X 10-5

Groundskeeper (Alternative) d NE NQ 2.20 x 10-5 2.20 X 10-5

Construction Worker (Conventional) C 4.79E-10 4.79E-10 9.80 x 10-7 9.80 X 10-7

Construction Worker (Alternative) d NE 2.95E-09 9.80 x 10-7 9.83 X 10-7

Recreational Receptors: Sportsman e NE NQ NE NA Trespasser e NQ NQ NE NA Hypothetical Residential Receptor: Resident (Conventional) C NE NQ 7.07 x 10-5 7.07 X 10-5

Resident (Alternative) d NE NQ 7.07 x 10-5 7.07 X 10-5

Vapor Intrusion Receptors: f

Indoor Worker NA NA NA NA <1.00 x 10-69

Future Hypothetical Resident NA NA NA NA <1.00 x 10-69

NONCANCER HAZARD

Industrial Receptors: Groundskeeper (Conventional) C 0.00123 0.00123 8.16 8.16 Groundskeeper (Alternative) d NE 0.000757 8.16 8.16 Construction Worker (Conventional) C 0.000550 0.000550 9.07 9.07 Construction Worker (Alternative) d NE 0.00339 9.07 9.07 Recreational Receptors: Sportsman e NE 0.000144 NE NE Trespasser e 0.000173 0.000173 NE NE Hypothetical Residential Receptor: Resident, Child (Conventional) C NE 0.00344 29.73 29.73 Resident, Child (Alternative) d NE 0.00212 29.73 29.73 Vapor Intrusion Receptors: f

Indoor Worker NA NA NA NA <1 9

Future Hypothetical Resident NA NA NA NA <1 9

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

a Includes only exposure to soil. b Includes exposure to both soil and groundwater. It must be noted that risks from exposure to groundwater are not considered actionable for this site. 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.

f An indoor commercial worker and a future hypothetical resident's exposure to indoor air vapors based on VOCs present in soil vapor.

9 The cancer risk was shown to fall below the trigger level of 1 E-6 and an noncancer hazard of 1 and also below the cancer risk of 1 E-6 for trichloroethene using the California EPA target indoor air concentration. The cumulative cancer risk was shown to fall below the level of 1 E-5 and a noncancer hazard of 1. Risks for these chemicals by this pathway are not quantified or included in cumulative estimates.

< - Less than. NA - Not applicable. NE - Not evaluated. NQ - Not quantified. Carcinogenic risks for cadmium in soil are quantified for the inhalation pathway only. The construction worker is the only receptor evaluated for this exposure pathway.

VOC - Volatile organic compounds. Cancer risk is expressed as an incremental lifetime cancer risk. Noncancer hazard is expressed as a hazard index.

KN91RSAI1 961RODlFinal11 96 ROD Tab2.3.4.5.xlsmITab 318/51200911 :58 PM

Table 4

Results of the Vapor Intrusion Evaluation RSA-196, Operable Unit 10


Structure

Evaluated Receptor

Detected

VOCs'

Soil Gas

Concentration b

(~g/m3)

Modeled

Indoor Air

Concentration (~g/m3)

Modeled Indoor Air Results Compared to Target Indoor Air Concentrations

EPA Target Indoor Air Concentrations:' CalEPA Target Indoor Air Concentrations:'

At

1 x 10~ (~g/m3)

Exceeds

1 x 10~

(Yes I No

At

1 x 10~ (~g/m3)

Exceeds

1 x 10~

(Yes I No

At

1 X 104

(~g/m3)

Exceeds

1 X 104

(Yes I No

At

1 x 10~ (~g/m3)

Exceeds

1 x 10~

(Yes I No)

At

1 x 10~ (~g/m3)

Exceeds

1 x 10~

(Yes I No

At

1 X 104

(~g/m3)

Exceeds

1 X 104

(Yes I No

Building 7373/7374

Indoor Commercial

Worker

Benzene 1.95E+01 600E-04 3.10E-01 No 3.10E+00 No 3.10E+01 No NA NA NA NA NA NA Carbon tetrachloride 1.64E+00 5.01E-05 1.60E-01 No 1.60E+00 No 1.60E+01 No NA NA NA NA NA NA Chloroform 2.SSE+01 S.93E-04 1.10E-01 No 1.10E+00 No 1.10E+01 No NA NA NA NA NA NA Trichloroethene (TCE) 2.79E+00 S.56E-05 2.20E-02 No 2.20E-01 No 2.20E+00 No 1.30E+00 No 1.30E+01 No 1.30E+02 No

Hypothetical Future

Residential Building

Hypothetical Future

Resident

Benzene 1.95E+01 S.6SE-04 3.10E-01 No 3.10E+00 No 3.10E+01 No NA NA NA NA NA NA Carbon tetrachloride 1.64E+00 7.26E-05 1.60E-01 No 1.60E+00 No 1.60E+01 No NA NA NA NA NA NA Chloroform 2.SSE+01 1.29E-03 1.10E-01 No 1.10E+00 No 1.10E+01 No NA NA NA NA NA NA Trichloroethene TCE 2.79E+00 1.24E-04 2.20E-02 No 2.20E-01 No 2.20E+00 No 1.30E+00 No 1.30E+01 No 1.30E+02 No

, The maximum concentration of VOCs detected in a single soil vapor sample exceeded the initial screening concentration and were carried forward for further evaluation.

Maximum detected soil vapor concentration from one soil vapor sampling point at RSA-196.

C Residential target indoor air concentrations of 1 x 106, 1 X 10-5

, and 1 x 10-4 (from Tables 2c, 2b, and 2a, respectively [EPA, 2002]).

California-modified PRG for trichloroethene in ambient air from EPA Region 9 PRG table (EPA, 2004) using the inhalation slope factor from Cal EPA (CaIEPA, 2005).

The indoor air concentration of trichloroethene reflecting a cancer risk of 1 x 1 (j3 equals 1.30 ~g/m3

NA - Not applicable. PRG - Preliminary remediation goal. VOC - Volatile organic compound. ~g/m3 - Micrograms per cubic meter.

References:

California Environmental Protection Agency (CaIEPA), 2005, Air Toxics Hot Spots Program Risk Assessment Guidelines, Part II, Technical Support for Describing Available Cancer Potency Factors Office of Environmental Health Hazard Assessment (OEHHA), May, http://wwwoehha.ca.gov/air/hot_spotsJpdf/May2005Hotspots.pdf.

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

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

KN9\RSA\196\ROD\Final\196 ROD Tab2,3,4,5.xlsm\Tab 4\8/512009\1:58 PM

Table 5

Summary of Screening-Level Ecological Risk Evaluation Results RSA-196, Operable Unit 10


Step 3a COPEC

Inorganic Analytes Aluminum Arsenic Cadmium Chromium III Chromium VI Cobalt Copper Iron Lead Mercury Nickel Silver Selenium Vanadium Zinc Perchlorate Compound Perchlorate

Results of Food Chain Modeling

Max-NOAEL Max-NOAEL Mean-NOAEL HQ greater HQ greater HQ greater than 1 and than 1 and than 1 and

Max-LOAEL Max-LOAEL Mean-LOAEL HQ less than 1 HQ over 1 HQ less than 1

X X X

X X X X X

X X

X X

X X X X

Mean-LOAEL HQ over 1

X

X

Results of Plant

& Earthworm Community Analysis--

Mean HQ over 1

X X

X X

NSV

X

X X

NSV

Retain as a COC?

N N N N N N N N N N N N N N N

N

Rationale Code

BKG BKG

LOWHQs BKG BKG

LOWHQs LOWHQs

WOE BKG

LOWHQs LOWHQs LOWHQs LOWHQs

BKG LOWHQs

LOWHQs

Notes: X - Range of HQ based on the results of the screening-level ecological risk assessment. HQ - Hazard quotient based on mean or maximum concentration compared to toxicity reference value. COC - Chemical of concern. COPEC - Chemical of potential ecological concern. LOAEL - Lowest-observed-adverse-effect level. NOAEL - No-observed-adverse-effect level. Max - Maximum detected value. Mean - Arithmetic average concentration. N - COPEC is not retained as a COCo NSV - No screening value available. mglkg - Milligrams per kilogram. Analytes in italics were deteremined to be naturally occurring.

Rationale Codes: BKG - Aluminum, arsenic, chromium, lead, and vanadium were determined to be background related and are not site-related. LOW HQs - HQs were less than 1 for most receptors, or had slightly elevated HQs above 1 which were determined to not pose a potential risk for adverse impacts to populations of ecological receptors. WOE - Weight of evidence; iron was determined to not be bioavailable in soils at this site.

KN9\RSA\196\ROD\Final\196 ROD Tab2,3,4,S.xlsm\Tab 5\8/5/2009\1 :58 PM

FIGURES


Madison•

Morgan County I

I I I I I

I I I

I

Marshall County

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

Tennessee

}-Madisonr County

N Tennessee

Mississippi l r "'" )1'/ \ 0' J ; '( 1 'r hG'",,"

(h"li.. Alabama ~-, r \

({ J

(5"I V'r,L

Florida

Limestone County

Madison County

•Huntsville Jackson County

u.s. Army Corps of Engineers Redstone Arsenal Madison County, Alabama

~Contract No. OACA21-96-0-0018

I0.___•.2 5===::::JI5_______.10 (

. Miles Sliaw· Shaw Environmental, Inc.

X:IRedstoneIGIS_DocumentsIProject_mapsIMiscellaneousIRSA_Madison_Co_Alabama.mxd

N

, , , , , , , , , , ,, , ,, , ,, , , , , , , , , ,

Figure 2 Legend

RSA-196 Site Location Map r·_·-I I RSA-196 Site Boundary i.._..J Redstone Arsenal Installation Boundary

I I Site Boundaries --- Roads

c:::J Groundwater Site Boundaries ~ Fences

c:::J RSA-146 --- Surface Water Drainage Features (some ephemeral)

c::::::::J Water Bodies Topographic Contour (1 O-ft interval) u.s. Army Corps of Engineers

NWI Classified Wetlands Topographic Contour (2-ft interval) II"M"II Redstone Arsenal : ' . , : Madison County, Alabama

c::::::::J Existing Structures Contract No. DACA21-96-D-0018

~ Stiaw® Shaw Environmental, Inc.

564

200 400

X:IRedstoneIGIS_DocumentsIProject_mapsIRSA_196Irsa_196_siteJocation_map.mxd

RSA-196

RSA-098 (Building 7346 not present during the time Building 7373/7374 was used as a test stand.)

S Possible Perchlorate Debris/Projectiles from Card-Gap Testing

Possible Perchlorate Debris/Projectiles

N

Bldg. 7373/7374

\

\

\

I

- 1'

\

Bldg. 7346

* |^| (0.033J) " i

\

X

\

\

\

\

Overburden

Concrete Pad

Relatively flat GW gradient \7

Industrial Drain/Sump

I- 7' (ND)

|- 12' (ND)

I - 19.5' (0.06)—!

U

Q_

I- 6' (0.025J)

I- 12' (0.024J)

I 19.5' (0.021J) —I

z ? U

Q_

Seasonal depths to water range from ~ 12' to 30'

86 ug/L TCE 77.7 ug/L Perchlorate

-32'

12 ug/L TCE 776 ug/L Perchlorate

-33'

Tuscumbia Limestone

/

n ̂2 - Water Level

I 1 Primary Source Area

I 1 - Secondary Source Area J

- Surface Soil Pathway

Q i i h c i i r f a ^ o Qnil Pafh\A#a\/

- Groundwater Pathway

1

Summary of Site Conditions

• Based on the RSA-196 characterization data and risk assessments, no action is warranted for surface media at this site.

• The results of the human health and ecological risk assessments indicate that no unacceptable risk to human health or the environment is posed by site-related contaminants in the surface media at the site, even when evaluated under the most conservative land-use scenario.

• The results of the fate and transport evaluation indicate that no site-related chemical has the potential to act as an ongoing source to groundwater. The groundwater beneath RSA-196 is contaminated and unacceptable noncancer hazard and cancer risk may exist if the groundwater is used for drinking, irrigation, or other uses that result in exposure to human receptors; however, groundwater contamination is addressed under the RSA-146 groundwater site.

Figure 3

RSA-196 Conceptual Site Model Summary

U.S. Army Corps of Engineers Redstone Arsenal

NOTE: All VOCs, including TCE , were detected below the DAF4 SSLs and do not pose an ongoing threat to groundwater. **Not to Scale Madison County, Alabama Contract No. DACA21-96-D-0018

X:\Redstone\GIS_Documents\Output\RSA_196_Draft_SoB_PP_Apr2008\RSA_196_Cartoon_CSM.ai

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