Roy F. Weston, Inc.1 Weston WayWest Chester, Pennsylvania 19380-1499610-701 -3000 • Fax 610-701-3186

12 September 1996

Mr. Phillip B. DellingerUSEPA1445 Ross AvenueSuite 1200 (6WQ-SG)Dallas, TX 75202-2733

Re: Transmittal of Final Request for Technical Impracticability Waiver for OU-3;Vertac Site, Jacksonville, Arkansas.

Dear Mr. Dellinger:

Enclosed please find two copies of the final Request for Technical ImpracticabilityWaiver for Operable Unit 3, Vertac Site, Jacksonville, Arkansas. These documents arebeing submitted on behalf of Hercules, Incorporated to support the OU-3 Record ofDecision (ROD) for the site.

If you have any questions concerning this matter please contact Mr. Doug Keilman at(302)594-6120 or me at (610)701-7284.

Very truly yours,

ROY F. WESTON, INC.

P } ' 1 / r•^^ • l^-i^Thomas R. Marks. P.G.Project ManagerGeosciences Department

TRM/kag

cc: Doug Keilman - Hercules0 -T! ' 'C

FINAL

REQUEST FORTECHNICAL IMPRACTICABILITY WAIVER

FOR OPERABLE UNIT 3

VERTAC SITEJACKSONVILLE, ARKANSAS

Prepared for:

Hercules IncorporatedHercules Plaza

Wilmington, Delaware 19894-0001

September 1996

Prepared by:

Roy F. Weston, Inc.Weston Way

West Chester Pennsylvania 19380-1449

0 \ECON_530\FOLDERS.G-L\HERC-VER\TWAIVE3DOC

TABLE OF CONTENTS

Section Title

1 INTRODUCTION

1.1 Overview1.2 Objectives

2 SITE CONCEPTUAL MODEL

2.1 Site Description and History2.2 Geology2.3 Hydrogeology

2.3.1 Water Bearing Zones2.3.2 Groundwater Flow

2.4 Contaminant Sources and Releases2.5 Contamination Distribution

2.5.1 Distribution of NAPL2.5.2 Distribution of Dissolved Contaminants

in Groundwater2.5.2.1 Plume Delineation Methodology2.5.2.2 Plume Delineation Concentrations

Based on Non-Carcinogenic Level2.5.2.3 Plume Delineation Concentrations

Based on Carcinogenic Level2.5.2.4 Plume Delineation

2.6 Contaminant Fate and Transport

3 RESTORATION POTENTIAL

3.1 Source Area Identification and Control3.2 Results of the Long-Term Pilot Extraction Test3.3 Spatial Extent of the Technical Impracticability Zone3.4 Applicable Technologies

3.4.1 Subsurface Drains3.4.2 Vertical Barriers3.4.3 Groundwater Extraction Wells and Product

Recovery Wells3.4.4 Enhanced Recovery Methods3.4.5 In Situ Biological Treatment3.4.6 Excavation3.4.7 Vapor Extraction3.4.8 Air Sparging3.4.9 Electrokinetics

OAECON 530\FOLDERS.G-L\HERC-VER\TWAIVE3.DOC

TABLE OF CONTENTS(Continued)

Section

4

Page inTitleooo

3-13 53.5 Remedial Alternativeso

APPLICABLE OR RELEVANT ANDAPPROPRIATE REQUIREMENTS (AREAS)FOR WHICH A TECHNICAL IMPRACTICABILITYWAIVER IS REQUIRED 4-1

4.1 Safe Drinking Water Act 4-14.1.1 National Primary Drinking Water Standards 4-14.1.2 Secondary Drinking Water Standards 4-3

4.2 Arkansas State Groundwater Quality Protection Strategy 4-3

CONCLUSIONS 5-1

REFERENCES 6-1

0\ECON 530'.FOLDERS.G-L\HERC-VER\TWAIVE3DOC 9/12/96

11

Figure No.

2-1

2-2

2-3

2-4

2-5

2-6

2-7

2-8

2-9

3-1

3-2

LIST OF FIGURES

Title Page

Site Location Map 2-2

Site Map 2-3

Conceptual Geologic Model 2-7

Piezometric Surface Map, Weathered Atoka Formation, 2-920 October 1992

Piezometric Surface Map, Weathered Atoka Formation, 2-1024 May 1993

Shallow Groundwater Flow Model 2-11

Groundwater Monitoring Points 2-12

Typical Groundwater Isopleth Map 2-15

Location of Observed NAPL Source Areas 2-18

Hydraulic Influence Zone during Pilot Groundwater ExtractionProgram 3-4

Spatial Extent of the Technical Impracticability Zone 3-7

LIST OF TABLES

Table No.

2-1

2-2

4-1

Title Page

NAPL Analytical Results, Vertac Site, Jacksonville, Arkansas 2-21

Groundwater Plume Delineation Concentrations 2-23

Safe Drinking Water Act Drinking Water Standards 4-2

OVECON 530\FOLDERSG-L\HERC-VER\TIWA1VE3DOC 9/12/96

111

SECTION 1INTRODUCTION

1.1 OVERVIEW

On 12 July 1989, Hercules Incorporated (Hercules) entered into an Administrative Order

on Consent (AO) with the United States Environmental Protection Agency (U.S. EPA).

The purpose of the AO, in part, is to provide for the characterization of the probable

nature and extent of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other selected

substances related to manufacturing and formulation activities performed at the Vertac

Chemical Corporation (Vertac) site (Site), Jacksonville, Arkansas. The characterization

of the Site was subdivided initially into two operable units. Operable Unit 1 and Operable

Unit 2. Operable Unit 1 (OU1) included a variety of above-ground media, such as:

contents of tanks and drums, shredded trash and pallets; process equipment; buildings and

other structures, and debris. The Remedial Investigation/Focused Feasibility Study

(RI/FFS) for OU1 was finalized in March 1991 (WESTON, 1991). A Record of Decision

(ROD) was issued for OU1 in 1993. (U.S. EPA, 1993a). Operable Unit 2 (OU2)

addressed below ground media, including: soil, subsurface soil, and groundwater. The

Remedial Investigation (RI) for OU2 was completed in two phases. The Phase I RI was

finalized in December 1992 and the Phase II RI was finalized in September 1995

(WESTON, 1995a). Subsequent to the Site Remedial Investigation/Feasibility Study

(RI/FS) Work Plan (WESTON, 1989), groundwater was separated into a third operable

unit for the purpose of preparing the FS.

The FS for OU3 was completed in September 1995 (WESTON, 1995b). This document

developed and evaluated three remedial alternatives for groundwater at the Site. These

alternatives include No Action (Alternative 1), Groundwater Pump and Treat (Alternative

2), and Groundwater Pump and Treat with Source Removal (Alternative 3). The OU3 FS

concluded that restoration of groundwater under much of the central process area to

0\ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC 1 1 9/12/96

concentrations below Safe Drinking Water Act (SDWA) maximum contaminant levels

(MCLs) is technically impracticable at the Site due to the presence of non-aqueous phase

liquids (NAPLs) and the hydrologic characteristics of the weathered and fresh bedrock.

1.2 OBJECTIVES

The purpose of this document is to demonstrate the technical impracticability (TI) of

groundwater restoration at the Site as described in the Office of Solid Waste and

Emergency Response (OSWER) Directive 9234.2-25, "Guidance for Evaluating the

Technical Impracticability of Groundwater Restoration" (USEPA, 1993b). This

document is intended to provide a summary of the information collected related to the

restoration potential of groundwater at the Site. More exhaustive discussion and analysis

of information can be found in the numerous documents that have been prepared as part

of the RI/FS process. These documents include:

• Remedial Investigation/Focused Feasibility Study (RI/FFS) for Operable Unit I(WESTON, 1991).

• Final Phase I Remedial Investigation Report for Operable Unit 2 (WESTON,1992).

• Long-Term Pilot Groundwater Extraction Test (WESTON, 1994).

• Phase II Remedial Investigation Report for Operable Unit 2 (WESTON, 1995a).

• Feasibility Study for Operable Unit 2 Media (WESTON, 1995c).

• Feasibility Study for Operable Unit 3 Media (WESTON, 1995b).

• Baseline Risk Assessment for Operable Unit 2 Media (WESTON, 1995d).

This document provides the basis for the TI determination, including the following

components:

0:\ECON_530\FOLDERSG-I,\HERC-VER\T[WAIVE3DOC i ^ 9/12/96

• Site conceptual model. o\oo

• Evaluation of Site restoration potential, o

• Determination of the spatial area over which the TI decision will apply.

• Estimates of the cost of proposed remedies.

• Applicable or Relevant and Appropriate Requirements (ARARs) for which TIwaivers are sought.

Each of these components is discussed in detail in the following sections.

0:\ECON_530\FOLDERSG-L\HERC-VER\TrWAlVE3DOC i i 9/12/96

SECTION 2SITE CONCEPTUAL MODEL

2.1 SITE DESCRIPTION AND HISTORY

The Site location is depicted on Figure 2-1. The property consists of two parcels (Parcel 1

and Parcel 2) that were acquired at different times (Figure 2-2). Parcel 1, which contains

the central process area and waste burial areas, is approximately 93 acres. It has been in

nearly continuous industrial use since the U.S. government constructed the former

munitions complex until it was abandoned in 1987 by the current owner, Vertac. Parcel 2,

which is approximately 100 additional acres on the northern side of the Site, was also part

of the former munitions complex and was purchased by Vertac in 1978. Parcel 2 does not

contain production facilities and is currently used by the U.S. EPA for drum storage. Most

of the Site is enclosed with a chainlink fence (see Figure 2-2).

The first facilities on the Site were constructed by the U.S. Government in the 1930s and

1940s. These facilities were part of a munitions complex that extended beyond the present

Site boundaries. Little is known about potential environmental impacts of government

operations that occurred on land that is now part of the Site. In 1948 the Reasor-Hill

Company purchased the property and converted the operations to manufacture insecticides

such as DDT, aldrin, dieldrin, and toxaphene. During the 1950s, Reasor-Hill manufactured

herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic

acid (2,4,5-T), and 2,4,5-trichlorophenoxypropionic acid (2,4,5-TP), which is also called

Silvex. Drums of organic material were stacked in an open field immediately southwest of

the production area, and untreated process water was discharged from the western end ofthe plant to Rocky Branch Creek through an unlined ditch during the 1950s.

0\ECON 530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC -) 1 9/12/96

FIGURE 2-1 SITE LOCATION MAP, VERTAC SITEJACKSONVILLE, ARKANSAS

2-2

Legend.......... Boundary Between

Parcels 1 and 2•"• — — • Central Process Area— •• i» Properly Line

- Rocky Branch CreekW//////A Buildings and FoundationsNllllll Railroad

—r— Fence

Souice Hercules Incoipoialed, Pmsonal Communiculion, 1989Base Map Adapted Ironi Milp by CH^M Hill Revised February 1993

FIGURE 2-2 SITE MAP, VERTAC SITEJACKSONVILLE, ARKANSAS

2-3

001812

Hercules Powder Company (Hercules Incorporated) purchased the Reasor-Hill property and

plant in 1961 and continued to manufacture and formulate herbicides. The drums in the

open area southwest of the central process area were buried in what is now referred to as ther<"i

Reasor-Hill landfill. During the period 1964 through 1969, United States Department of ooo

Defense (DOD) ordered Hercules, pursuant to presidential order under the Authority of the °

Defense Production Act, to manufacture a defoliant known as Agent Orange at the Hercules

Plant for use in the war effort in Vietnam. Agent Orange consisted of a mixture of equal

parts of the butyl esters of2,4,5-T and 2,4-D. Organic materials from these manufacturing

processes were buried by Hercules on the Site in what is now referred to as the north

landfill area. Hercules discontinued operations at the Site in 1970.

From 1971 to 1976 Hercules leased the plant Site to Transvaal, Inc. (Transvaal), a

predecessor company of Vertac. Transvaal purchased the property and plant from Hercules

in 1976. Transvaal resumed production of 2,4-D and intermittently produced 2,4,5-T.

Wastes continued to be buried onsite until approximately 1978. In 1978 Transvaal

underwent a Chapter XI bankruptcy reorganization, and ownership of the Site was

transferred from Transvaal to the new company, Vertac Chemical Corporation, which is the

present owner of the Site. Vertac operated the plant until 1986. On 31 January 1987,

Vertac abandoned the Site and later declared bankruptcy. The U.S. EPA and Hercules

took over management of the Site, which has included the maintenance and overpacking of

nearly 29,000 drums of organic material by U.S. EPA. Hercules has continued treatment

of surface water runoff collected in ditches that drain to sumps, and of groundwater

collected in french drains, which were constructed on the west and south sides of the

process area, downgradient of the landfills.

A court-ordered remedial action was performed on several areas of the Site. This court

order is referred to throughout this document as the "1984 Court Order". The areas where

remedial measures were taken included: the North Burial Area, the Reasor-Hill Burial Area,

the Equalization Basin, and the Cooling Pond. At the North Burial Area and the Reasor-

OAECON 530\FOLDERS.O-L\HERC-VER\TIWAIVE3DOC ^ f 9/12/96

Hill Burial Area additions were made to the clay caps which had been placed over the burial

areas in 1980. Vertical groundwater barriers (i.e., french drain and slurry wall) were

installed at the perimeter of the areas to intercept and collect shallow groundwater. The

vertical barriers were designed to be installed to the top ofrippable bedrock (D'Appolonia,

1984). It is estimated that the french drain and slurry wall were installed to a maximum

depth of approximately 23 feet below the ground surface (BGS). In some areas, the french 5

drain was installed to approximately six feet BGS due to a shallow bedrock surface.

Sediment from the Cooling Pond was excavated and consolidated into an aboveground

vault. The Cooling Pond was capped following excavations. The thickness of the cap at

the Equalization Basin was also increased. Other provisions of the 1984 Court Order

included installation of improved surface water collection systems, and operating and

maintenance requirements.

•t

00

Currently, there are no manufacturing operations at the Site. Continuing activities at the

Site include operation of the surface water and leachate collection and water treatment plant

by Hercules. The water treatment plant treats surface water runoff and groundwater by

phase separation followed by adsorption through granular activated carbon. A series of

drainage ditches and sumps, which surround the central process area, collect surface runoff

and pump it to the water treatment plant. A french drain system that runs along the western

and southern sides of the burial and process areas is designed to intercept the shallow

groundwater downgradient of the landfills and to transport the groundwater to the water

treatment plant.

2.2 GEOLOGY

The Phase I RI results revealed that the Atoka Formation is the primary geologic formation

at the Site and the only formation exhibiting the presence of site-related compounds

(WESTON, 1992). Across most of the Site, the Atoka Formation consists of 2 to 18 feet of

unconsolidated weathered bedrock, which is underlain by up to 35 feet of consolidated,

weathered bedrock that overlies consolidated fresh bedrock. The consolidated bedrock is

0\ECON_530\FOLDERSO-L\HERC-VER\TIWAIVE3DOC -i c W12/96

characterized by northward dipping (sloping) interbedded sandstones, siltstones, and shales

with open joints and fractures.

2.3 HYDROGEOLOGY

2.3.1 Water Bearing Zones

The hydrogeology at the Site is complex as a result of the varying lithologies of the Atoka

Formation, the variability in hydraulic conductivities of the water-bearing and semi-

confining units. A geologic conceptual model of the varying lithologies is presented on

Figure 2-3.

At the surface, the Site is covered with 2 to 18 feet of unconsolidated weathered bedrock

(i.e., overburden soil). Groundwater is first encountered at approximately 5 to 10 feet

below ground surface in this zone. Hydraulic conductivity in this zone ranges from

1.07xl0'5 cm/sec at MW-74 to 2.53xl0"3 cm/sec at MW-70. Throughout the Site, the

Atoka is the dominant hydrogeologic formation and is the only formation where site-related

contaminants were detected. The Wilcox and Midway Formations overlie the Atoka

Formation in non-contaminated Site areas north and east of the central process area.

Below the unconsolidated, weathered bedrock the geology changes to a highly fractured

bedrock (also known as the consolidated weathered bedrock) of the Atoka formation. The

interface between the unconsolidated and consolidated bedrock is not discrete. This zone is

characterized by weathered fractured rock with the competency of the bedrock increasing

with depth. Groundwater is present throughout this zone. Hydraulic conductivity in this

zone ranges from 1.85xl0'6 cm/sec at MW-61 to 6.97xl0"4 cm/sec at MW-84. The rock

type in this zone is consistent with typical interbedded sandstones, siltstones and shales of

the Atoka formation.

0\ECON_530\FOLDERSG-L\HERC.VER\TIWA1VE3DOC -) r 9/12/96

South North

NOTE: Not to Scale96P-3097

FIGURE 2-3 CONCEPTUAL GEOLOGIC MODELVERTAC SITE, JACKSONVILLE, AR

001816

Below the consolidated weathered bedrock, the Atoka Formation is composed of a series of

interbedded sandstone, siltstone, and shale units which exhibit a downward slope (dip) of

35° toward the northeast. This zone is referred to as the fresh bedrock or the unweathered

bedrock. Groundwater is encountered throughout this zone. The primary water-bearingr-

units in these layers are the sandstone beds, which are characterized by relatively effective oo

fracture porosity, and a low intergranular porosity. The potential for groundwater flow is §

higher in these units than in the surrounding stratigraphic units which are composed mostly

of shales. These shale beds are characterized by low effective porosity with fracturing at

lithologic boundaries. As a result, the shale beds tend to serve as semi-confining units.

Hydraulic conductivity in this zone ranges from 2.96x10' cm/sec at MW-86 to 2.05xl0"3

cm/sec at MW-95.

2.3.2 Groundwater Flow

The Site groundwater flow in the consolidated and unconsolidated weathered bedrock is

driven by recharge areas within the central process area resulting in lateral flow outward

toward the east, west, and to a lesser degree toward the south. The groundwater levels in

the weathered bedrock, as measured in the spring of 1993 and the fall of 1992, are presented

on Figures 2-4 and 2-5, respectively. Figure 2-6 shows the general direction of shallow

groundwater flow at the Site which is controlled by the recharge areas, central ditch, and a

groundwater divide that trends in a north/south direction, bisecting the central process area.

Although seasonal variations in groundwater elevations range from two to six feet (as

depicted on Figures 2-4 and 2-5), these variations do not affect the directions of

groundwater movement and the groundwater flow model presented on Figure 2-6 is valid

throughout the year. Based on the interconnected nature of the weathered bedrock and the

fresh bedrock, it appears that the groundwater divide is also present in the fresh bedrock.

Groundwater data have been collected from numerous monitoring wells installed at the Site.

The locations of these wells are depicted on Figure 2-7. The depths and construction details

of these well are presented on Table 2-7 of the Phase I RI and Table 2-4 of the Phase II RL

0:\ECON_530\FOLDERS.G-L\HERC-VER\TIWAIVE3.DOC ^ o 9/12/96

^ P2-I49 Pie?ometer Location and Number

i? MW84 Monitoring Well location and Number

_^^~ Groundwater Elevation Contour(Measured in Feel Above Mean Sea Level)Contour Interval' 2 feet;Contour Dashed Where Approximate

• I;HW Reasor Hill Well

• " French Drain• • Slurry Wall

Fence LineProperty Boundary

""• Central Process Area BoundaryCentral Ditch

W-

Scstte In Feet

Groundwater elevation data collected on20 October 1992 by Hercules site personnel.Map was constructed using wells completedin the wealhered Aroka Formation

Source: Vert/ic Site Boundary and PhologrammelricSurvey Prepared by Wesi rtnd Aswan's. Inc

Prcyeclioii Arkansas Coordinate System.North Zone (NAD 1 9 8 ^ )

FIGURE 2-4

PIEZOMETRIC SURFACE MAPWEATHERED ATOKA FORMATION

20 OCTOBER 1992VERTAC SITE, JACKSONVILLE, AR

2-9

Legend

<? P2-149 Piezometer Location and Number

t^ MW-84 Monitoring Welt Location and Number

-"~ Groundwater Elevation Contour(Measured in Feet Above Mean Sea Level}Contour Interval: 2 feet;Contour Dashed Where Approximate

• f;nw Rcasor-Hill Well

French DrainSlurry W.iHFence LifieProperty BoundaryCentral Process Area BoundaryCentral Ditch

W-

Gioundwatcr devritioti dritti collected on24 M<iy 1993 by Hercules Site peisonnciM-ip wdi construried Uiing wells cofnpleteclin the weathered Atoka Formfiliori

Source; Vertac Site Bounddry cirid PhorogrammeiricSurvey Prepaied by West and Associate's, Inc.

Projection Arkansas Coorclnwie System.North Zone (NAD t983|

FIGURE 2-5

PIEZOMETRIC SURFACE MAPWEATHERED ATOKA FORMATION

24 MAY 1993VERTAC SITE. JACKSONVILLE, AR

2-10

OZ8IOO Legend—— — Approximate Boundary of Recharge

Area (Vanes with Seasonal Water Level Change)

[~~ j Covered Area

Recharge Area

U Discharge Area

JL Seep/Spring Location

i"'1'" Area of Regularly Ponded Water

D Downward Component of HydiaulicGradient at Well Pafr

U Upward Component of HydraulicGradient at Well Pair

__ _ _ __ Property Boundary

^•——^ Direction of PotentialGroundwater Flow

N

W-

400

Scale In Feet

Note!' I Some small covered <weas may exiM within thecentral process a'ed but dre tiicldrii from viewand are too small to display,

2 SeepApnng locations were observed duringthe Rl investigdiion byWESiON persorinel

3 The occurences of seeps and springs varywith seasonal and other type! n( pii.'/omcinc

Source Vcrt^c Site Bounclaiy/ind Phnlogi^fninctricSurvey Prepared by West atld A<s<niatrY Inc

Projection' Arkansas Coordtricito System,NorTh Zone iriAD 1983)

FIGURE 2-6

SHALLOW GROUNDWATER FLOWMODEL

VERTAC SITEJACKSONVILLE. AR

2-11

1

')],r niya

IZ8100

.^..••i • • • • 1 1 ^ ' • • • " ; i , 1 ^, ,.• , .. r It '.¥" .'•-.- i ^ . II1

"'• , i. 'i -. ,",iu';"••/'/m w .'i! j |-... .,.>..," • ' (Si-,..- 1 - .i ;

• ^^T" \ 1 \ ! • 1 !r.,.,...^..,,^"" \ •...^ :

^.. "7 '1 —/ i.nv.-'.IAtf* 1 . r / i r,,,» ;•/•

/ . . ' r i . . . • 1 MVt.1 <> Irt ,^1..^——«.. ,,l'i.,-ii,

/ | '" — . ' • 1 MW.9?

. ,V -1 : \ MV,'/'1"""'";| i? r : ', i1 1 , 1 J' | | „» M\t, B? i

1 / - - ,-,.^.. ;-:••• 1 , ( <» l;L-.,,,,,H,ll..>.ell ^,,^

1 ..•;- • ' . . . . ^E———

i-. ,>^ n-,,.. ,•.,...„, m^T",• • • 1

1' -• * -.I1 ,•:11^r• :•.l"•l" ' - , : i •

! / ' 'i . . . • • • . .^-•'. \, , • • • • • • • • • ! •• . • L i : •;- • • •' i - \ •"'""" • ^^ , ^—J •' ' " „. . ,,„-...• , > • . . . ! • : , . ' • 1" MW.W,' ; >/•""•• "• • •

-I. , .., \ i I ' - MVl, 7.1^ ^M^:' \ ' | • '• '• ,L ' , ^l••'\>•l!/

, Y'^,:' \ ',„; :. 1 ! ' ! • 11..,/^ 1 : ,'.„•..,• 1 0 ^

^ \ | ' ! z1 \^^.. l.i ^^.-.i^l.^.l,^,^^ /

t ' V, \ : ! ''•'••"••''^ c-"^•-".'-- . • . , " ^ ' .-!

""" " • • • • • - . , , "—"~~7 \\ •11"' ; !" \ ^ • • • 1 ] 1 • ; : '^ri""^ i^.r,.„./.;.

/

! /(

(' l ' ;

. i / / !

: i ,', ,

—••CJ: • ' ;

m/-9'.i ' ; ; ! ' 1 ^ 'I'/ 1 •!:' ( ; •1

'1 • • '1. yr..n'1;// .."f-.lin

w :f ""v 1"\ ,f r-lW i i..

MM. - ', ^, M\t» •|)

\. ('-'"•'"•'^i.wo.•t'.•... 1 1 ,,''p/;ll,,;i l,,.,..., ,

/I;.,,,-;/ .^</' M'.».' i. / . '•

- - - . - - - ; i - - . . - - . - ,Ji ,

Legend

^\ '. \ \ '• ! MonitohtK) Well

,» , \ • PumpHig WrII

- — - - • French Dr.iin

— - . Slurry Wall

Fence Line

Property Boundary..- „ —. central Process Area Boundary

Central Ditch

N

^

-7^'

s

0 400 800

Scale In Feet

Source: Venae Sue Boundary and FhologrammelricSurvey Prepared by West and Associates, Inc.

Projeclion Arkansas Coordinate System.North Zone (NAD 198U

FIGURE 2-7

GROUNDWATER MONITORING POINTSVERTAC SITE

JACKSONVILLE, ARKANSAS

2-12

Shallow groundwater to the west of the groundwater divide flows downgradient toward

Rocky Branch Creek. Before reaching Rocky Branch Creek, shallow groundwater flowing

west from the central process area is intercepted and collected by the existing french drain

which was installed as prescribed by the 1984 Court Order. During seasonal periods of

high precipitation, a groundwater discharge to the closed cooling pond area was evidenced

by a seep along the eastern bank of the pond. This discharge is currently collect by a sump.

Overall, the french drain and Rocky Branch Creek appear to act as hydraulic barriers to <^iCN00

o0

western migration of shallow groundwater. The RI results also indicate that the central

ditch may exhibit some influence on shallow groundwater flow within the central process

area. The central ditch is a gunite-lined drainage ditch, approximately five feet below the

ground surface, that has shown persistent seepage of groundwater in the ditch through

cracks in the gunite. It has been determined, based on survey measurements, that the base of

the central ditch is below the adjacent groundwater level. The amount of seepage into the

central ditch has been estimated by Hercules plant personnel as less than one gallon per

minute. Due to the small volume of the discharge to the central ditch, the influence of this

feature on the water table is difficult to quantify.

Shallow groundwater flow to the east of the groundwater divide in the central process area

is southeastward toward Marshall Road. No points of groundwater discharge have been

identified in this part of the Site. It appears that the Midway Formation, which overlies the

Atoka Formation in the area near Marshall Road, may act as a confining unit precluding

upward flow of groundwater in this area. There are currently no french drains or other man-

made structures in place to intercept groundwater flowing eastward from the central process

area. As a result, potential migration of site-related compounds dissolved in this eastward

flowing groundwater is the primary concern at the Site. Shallow groundwater within the

central process area exhibits a downward vertical gradient.

Groundwater flow through the fresh bedrock is strongly influenced by the structure of the

Atoka formation. Groundwater flow through the fresh bedrock is primarily along strike,

within the sandstone; the shale units act as semi-confining layers that tend to limit the

O^COl^SiOWl-DERSG-LWRC-VERVrrWAIV^ DOC ^ i i 9/12/96

interconnection between adjacent sandstone units in the fresh bedrock. This effect is

evidenced by the results obtained during pump tests. During pump tests, drawdown was

observed at distances greater than 500 ft in observation points located within the same

sandstone unit (i.e., along strike, or down dip). The pumping tests also demonstrated that

the fresh bedrock is also hydraulically connected to the weathered bedrock. This would

allow pumping wells installed in fresh bedrock to exert hydraulic influence over water in

the weathered bedrock, and vice versa, provided the pumping rate is sufficient. oo00

As discussed above, shallow groundwater flowing in a southern direction from areas north

of the central ditch appears to be intercepted by the central ditch. From north to south

across the central ditch, a sharp gradient in the isoconcentration maps is observed for many

of the site-related compounds (WESTON, 1992). The isoconcentration map for a typical

Site contaminant (i.e., 2,4-dichlorophenol) is presented in Figure 2-8. Based on the

hydraulic influence exerted by the central ditch, it would appear that the central ditch is

helping to control the flow of groundwater contaminants to the southern part of the central

process area.

As previously discussed, in addition to horizontal groundwater flow, vertical components of

the hydraulic gradient were evaluated through the comparison of water level elevations

among nested monitoring wells. These measurements indicate that most of the Site exhibits

a downward (negative) vertical gradient and is a recharge area. Limited regions of upward

(positive) hydraulic gradient were observed on the west and east sides of the Site in areas

adjacent to Rocky Branch Creek and along Marshall Road, respectively.

In summary, groundwater flow at the Site occurs outward from the central process area

which serves as a recharge area. Within the central process area, a groundwater divide

separates flow to the east and west. Flow to the west of this divide flows toward Rocky

Branch Creek. The existing french drain was designed to intercept the shallow groundwater

and associated site-related compounds flowing in this westward direction before it reaches

the creek. Groundwater flow in the western central process area appears to be influenced by

0 \ECON_530\FOLDERS G-L\HERC-VER\TIWA1VE3 DOC ') 1 4 9/12/96

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Legend ,

®MU/B< Monilonng Well LoCtiliofi ttiid Number

Reasof-HitI Well, Not Contoured Dueto Uncertain Well CorisUuction

— 10 — 2.4 Dichlorophcnol Isopleth ContourLine (Dashed Where Approximate,Concentrations Inferred by Interpolation)

350 Reported 2.4-Dichloropheno) SampleConcentration in Milligrams per Liter|mg/L| or Parts per Million |ppm)

An<ilyti(al D.it.t Oii.ilifH.-is

ND Not Detected at SampleOuaniitaiion Limit

J - Quantiianon Estimated BelowOuanlitdtion LunK

R - Quantitation Limit Rejected

• ~ ~- " "" French Drain

————- Slurry Wall

Fence Line

Property Boundary

""" " ''"""' Central Process Area Boundary

• Central Ditch

N

W -^- 1=

-W-

s

0 400 800 1200

Scale In Feet

Notes: Curie cnlrationi shown or welliIn the weathered Atokri Formaiion

Sampling dates and sourcci of analytic^ dara1 , Welti 1 to 57: 10/9/89 - 1 0 / 1 1 / 8 9 Hercules Incorporated3. Wells 58 to 84: 8/31/90 - 1 1 /16 /90 WESTON Rl Data

Source: Vertac Site Bounddryand PhotogrammetficSurvey Prepared by West and Associates. Inc

ProJection: Arkansas Coordinate System,North Zone (NAD 1983)

FIGURE 2-8TYPICAL GROUNDWATER

ISOPLETH MAPWEATHERED ATOKA FORMATION

VERTAC SITEJACKSONVILLE, AR

2-15

001824

the central ditch; limiting flow to the southern direction. This is evidenced by perennial

seeps along the banks of the ditch and by deflections in the groundwater elevation contours

in areas adjacent to the ditch.

2.4 CONTAMINANT SOURCES AND RELEASES

Releases of raw materials, intermediate products, or waste to soil or groundwater within the

central process area may have occurred historically since the Site was constructed (about

1942). An accurate history for volumes and/or frequency of releases is not available. Based

on operations, releases may have occurred through the following mechanisms (Figure 4-3,

Weston, 1995a):

• Raw material releases, such as the tetrachlorobenzene spill along the railroadtracks.

• Intermediate product releases, such as through blow-outs from the reactor.

• Product releases, such as discharge of process wastewaters and off-specificationmaterials into the central ditch, leakage from the industrial sewer, or leakagefrom the wastewater equalization basin.

• Releases from past materials handling and previous production operations, suchas releases from valves, fittings, and releases during loading and unloadingoperations.

• Discrete release events, such as the few drums (e.g., 1 to 3 drums) of wasteliquids that were reportedly dumped into the Reasor-Hill well.

• Burial of waste materials.

2.5 CONTAMINATION DISTRIBUTION

The site-related compounds of concern in the groundwater at the Site include: toluene,

phenol, chlorinated phenols, chlorophenoxy herbicides, and 2,3,7,8-TCDD. These

0\ECON_530\I:OLDERSG-L\HERC•VER\TrWAlVE3 DOC -) 1 r 9/12/96

compounds are present in varying concentrations and exist as both dissolved-phase

contaminants and, in some areas, as NAPLs, particularly, north of the central ditch. The

origin of these compounds in groundwater is likely from past waste management and

disposal practices.

2.5.1 Distribution of NAPL 00

30

Assessments of the extent ofNAPL at the Site were conducted through the use of test pits

and monitoring well sampling. Samples collected from both test pits and monitoring wells

were first examined visually for the presence of NAPLs and then were subjected to a phase-

separation test using a non-volatile hydrophobic dye to indicate the presence of NAPLs.

The presence of NAPLs appears to occur primarily in the northern part of the central

process area. Specific Site locations where NAPLs were observed (Weston, 1995a) include

(see Figure 2-9):

• Reasor-Hill Well: This well is located north of the central ditch in the area ofthe chlorination plant sites. During the Phase I investigations, a 1 ft. thick light,non-aqueous phase liquid (LNAPL) was identified in this well which reportedlyhad been used one time to dispose of waste. Later, during Phase IIinvestigations, a disseminated NAPL of indeterminate thickness was identifiedat mid-water column, approximately 25 feet below the top of casing.

• Tetrachlorobenzene Spill Area: This area includes test pits TP-1 and TP-2,where patches of a pink-brown liquid were observed on the surface of the water.Dense, non-aqueous phase liquid (DNAPL) was also observed in the bedrock atstratigraphic boring XB-3 in this area.

• MW-23A: This monitoring well is located near the northern boundary of thecentral process area and just west of the groundwater divide. Assessments forNAPLs at this well indicated the presence of a three inch thick DNAPL. Thismaterial exhibited a toluene concentration of 2,300 ppm, a viscosity of 521.8centipoises, and a specific gravity of 1.443. A thin, organic liquid film was alsoobserved on top of samples collected from this well. It is possible that thisapparent LNAPL may have separated from the DNAPL during collection of thesample. It should be noted that this well is located west of and adjacent to theslurry wall previously constructed around a portion of the north burial area.

0:\ECON_530\FOLDERS G-L\HERC-VER\TIWAIVE3 DOC '? 1 7 9/12/96

001827

• MW-64: This monitoring well is located in the vicinity of thetetrachlorobenzene spill area. A sample collected from this well contained athin film which was undetectable prior to the hydrophobic dye test.

• XB-19: This is a stratigraphic boring which was collected at the location whereMW-78 and MW-79 were installed. It is located within the "blow-out" area in oothe vicinity of the recovery plant and 2,4,5-T production area. A tar-like. (Nnonflowable material was observed in a fracture in this boring. o

o• French drain system: This groundwater collection system is located in the

western and southern regions of the Site and intercepts shallow groundwatermigrating westward toward Rocky Branch Creek and southward to the extentthat it could occur from the central process area. NAPLs have been observedduring the treatment of collected groundwater.

• MW-71: This monitoring well is located in the eastern portion of the centralprocess area near the east drum storage area. A disseminated, mid-watercolumn NAPL was discovered in this well at an indeterminate depth. Theappearance of the NAPL at mid depth in the water column suggests that it maybe of an intermediate density between an LNAPL and a DNAPL. The thicknessof this NAPL was also indeterminate, but not of sufficient thickness to berecoverable.

• MW-62,MW-63: These two monitoring wells are located near the center of thecentral process area just north of the eastern edge of the central ditch. Samplescollected from these wells exhibited a thin, iridescent coating on the interior ofthe sample bottle which did not react with the hydrophobic dye; therefore, thepresence of NAPL at this location is uncertain, and if present, it is notrecoverable.

• Various Test Pits: Test pits TP-6, TP-9, TP-10, TP-11, TP-12, TP-13, and TP-14 were excavated throughout the central process area in areas where thedissolved-phase concentrations of the site-related compounds were the highest.At each of these test pits, thin, oily films (sheens) were evident on the surface ofthe water in the pits. These films were much less than 0.5 inches in thickness.

Of the above-listed Site locations, NAPLs were visually observed in potentially recoverable

quantities (i.e., at a thickness greater than approximately one inch in the well) at only three

locations. Selection of a recoverable thickness of 1 -inch in the well recognizes the practical

limitations of available product recovery technologies. The locations, where potentially

0\ECON_530\FOLDERSG-L\HERC-VER\TIWA1VE3 DOC ") 1 Q 9/12/962-19

recoverable amounts of product were observed, are shown in Figure 2-9, and include the

Reasor-Hill well, where an LNAPL was observed, and stratigraphic boring XB-3, and MW-

23A where DNAPLs were observed. At the other locations on-site, only trace quantities of

NAPLs were present as evidenced by either slight, oily sheens or by the hydrophobic dye

tests. This appears to indicate that throughout much of the northern portion of the central

process area, the NAPLs, if present, are heterogeneously distributed within the saturatedCT\soils and bedrock. The NAPLs at the Site do not generally appear as distinct floating (N

LNAPL or pools of DNAPL. Instead, residual product is trapped within the pore spaces of °

the soil and fractured bedrock by capillar forces at variable levels within the groundwater

system.

The appearance of the NAPLs as an LNAPL or DNAPL indicates differences in NAPL

density from location to location, due to differences in chemical composition. The chemical

characterization of the NAPL has been difficult due to its presence in insufficient quantities

for sampling at most locations. Two NAPL samples which have been collected for analysis

include the DNAPL from MW-23A and the NAPL separated from the french drain

leachate. The analytical results of the NAPL samples are presented on Table 2-1. The

french drain leachate sample contained high levels of toluene, chlorophenols,

chlorobenzene, and chlorophenoxy herbicides.

2.5.2 Distribution of Dissolved Contaminants in Groundwater

2.5.2.1 Plume Delineation Methodology

The extent of the dissolved-phase groundv/ater plume for the site-related compounds was

determined by comparing concentrations in groundwater with available sources of

information including regulations and the baseline risk assessment. Regulation-based

concentrations were taken from the Safe Drinking Water Act Maximum Contaminant

Levels (MCLs) for those site-related compounds for which MCLs have been promulgated

(Subsection 4.1.1). In addition, risk-based concentrations were calculated based on

0\ECON_530\FOLDERSG-L\HERC-VER\TrWAlVE3DOC ^ -511 9/12/96

TABLE 2-1NAPL Analytical Results, Vertac Site

Jacksonville, Arkansas

French DrainNormal Duplicate

VOCs mg/kg mg/kgChloroform 8.8 J 5 JTrichloroethene 3.6 2.8 JBenzene 33 J 19 JTetrachloroethene 45 27Toluene 100000 110000Chlorobenzene 84 52Ethylbenzene 190 1 1 0Xylenes 310 190

BNAs mg/kg mg/kg2,4-dichlorophenol 22000 220001,2,4-trichlorobenzene 8100 U 7100 J2,4,6-trichlorophenol 8100 U 95002,4,5-trichlorophenol 40000 U 40000 J

PESTICIDES/PCBs ND ND

HERBICIDES mg/kg mg/kg2,4-D 6400 72002,4,5-TP 1100 14002,4,5-T 3300 4000

DIOXIN ng/g ng/g2,3,7,8-TCDD 21 1200

METALS mg/kg mg/kgBarium 74.8 J 67.4 JBeryllium 0.26 J 0.26 JCalcium 524 J 281 JChromium 73.1 J 69.6 JMagnesium 37.2 J 43.2 JPotassium 305 J 522 JSodium 536 J 521 J

PHYSICAL PARAMETERSSpecific gravity NA NAViscosity (cp) NA NAUltimate analysis (Wt %)

-Carbon 56.2 56.5-Hydrogen 4.03 3.98-Oxygen 39.5 39.2-Nitrogen 0.13 0.15-Sulfur 0.18 0.21

Melting point (F) NA NAPercent ash (Wt %) 1.8 1.2Percent moisture (Wt %) 2 - 4 2 - 4Heating value (Btu/lb) 10500 10800Total chlorides (mg/kg) 280000 290000

-Inorganic chlorides 200 300-Organic chlorides 280000 290000

MW-23Amg/L

NANANANA

2300NANANA

NANANANA

NA

NANANA

NA

NANANANANANANA

1.443521.8

NANANANANANANANANANANANA

Solubilitymg/L @ °C

9300 @ 251100 @ 251280 @ 20

150 @ 25515 @ 20488 @ 25

1520 @ 20175-200 @ 20-25

4500 @ 2519 @ 22

800 @ 251190 @ 25

890 @ 25140 @ 25278 @ 25

1.93E-05

HydrolyzesInsolubleReacts

InsolubleReactsReactsReacts

Notes:NA -.Not analyzed. 2-21TAB2 1 XLS-NAPL Data

potential carcinogenic and non-carcinogenic effects of site-related compounds. The

concentrations derived from each of these sources were then compared, and the most

restrictive concentration for each site-related compound was selected to delineate the

groundwater plume. These concentrations, which are presented in Table 2-2. define the

boundary of the groundwater plume requiring remediation. The location, size, shape, and

mobility of the plume was then used as a guide for development of remedial action

alternatives.

2.5.2.2 Plume Delineation Concentrations Based on Non-Carcinogenic Level

Several exposure scenarios were considered in developing the non-carcinogenic plume

delineation concentrations for groundwater. Using the scenario of a future worker, as

presented in the baseline risk assessment (WESTON, 1995d), the plume delineation

concentrations (PDCs) for each site-related compound were calculated based on a hazard

index of 1 using the following equation:

PDCm-^'HI,ril

Where:

PDCm = Plume delineation concentration based on the hazard index from

groundwater as calculated in the baseline risk assessment.

^Actual = Concentration of the site-related compounds in groundwater used in

the baseline risk assessment.

HI = Calculated groundwater hazard index for compound as calculated in

the baseline risk assessment.

HI) = Hazard index equal to 1.

0\ECON_530\FOLDERSG-L\HERC-VER\TIWA1VE3DOC -\ f\ 9/12/96

TABLE 2-2

Groundwater Plume Delineation Concentrations (PDCs)Vertac Site. Jacksonville. Arkansas

Site-RelatedCompound

2-Chlorophenol

4-Chlorophenol

2.4-Dichlorophenol

2.6-Dichlorophenol

2.4.5-Trichlorophenol

2.4.6-Trichlorophenol

Toluene

Tetrachlorobenzene

2.4-D

2.6-D

Silve\

2.4.5-T

2.4.6-T

2.3.7.8-TCDD'

Basis of PIui

SDWAMaximum

ContaminantLevel (MCL)

(mg/L)

—

—

.--

—

—

—

1.0

—

0.07

—

0.05

—

—

0.033

me Delineation Cor

Non-Carcinogenic

Level(mg/L)

0.5

0.5

0.3

0.3

10.2

—

20.5

0.03

1.0

1.0

0.8

1.0

1.0

0.1

icentration

10-'Carcinogenic

Level(mg/L)

—

—

—

—

—

2.6

—

—

—

—

—

—

—

0.2

Selected PDC2

(mg/L)

0.5

0.5

0.3

0.3

10.2

2.6

1.0

0.03

0.07

1.0

0.05

1.0

1.0

0.03

NOTES:

' Values for 2.3.7,8-TCDD are presented in ng/L.: Selected PDCs are selected from the lowest value presented for each compound.3 Selected PDC for TCDD was below analytical detection limits. In cases where TCDD was not detected.it was assumed that the concentration was less than the PDC. The boundary of the plume for 2.3.7.8-TCDD will be confirmed by sampling during remedial design and during implementation of themonitoring plan using higher resolution analytical methods.

Q FOLDERS G.L HERC.VER'TAB:,: DOC

2-23

2.5.2.3 Plume Delineation Concentrations Based on Carcinogenic Level

A similar procedure was used to determine the plume delineation concentrations based on a

carcinogenic goal level of 1 X 10 . The equation used for this calculation is:

PDCcarc- CAC"'a' •"LeVelooalLevelcare

Where:

PDCcan^ Plume delineation concentration based on carcinogenic risk from

groundwater as calculated in the baseline risk assessment.

^Actual = Concentration of the site-related compounds in groundwater used in

the baseline risk assessment.

Leveled Calculated carcinogenic risk for compound as calculated in the

baseline risk assessment.

Leveled Carcinogenic level goal equal to 1 X 10"*.

2.5.2.4 Plume Delineation

Based on the Site characterization performed during the Phase I and Phase II RI, shallow

groundwater contamination at the Site is limited to the Atoka Formation and concentrations

of potential concern are believed to be contained within the Site boundary. Some site-

related compounds were detected at low levels in monitoring wells MW-89 and MW-94,

which are located outside the central process area in the eastern side of the Site. The data

0 \ECON_S30\FOLDERSG-L\HERC-VER\TrWAIVE3.DOC -5 ^ ) A 9/12/96

indicate that the most significant shallow groundwater contamination within the central

process area is located north of the central ditch.

The majority of the affected groundwater contains only dissolved-phase compounds, and' -

the potential for offsite migration of these dissolved compounds is the primary oo

environmental concern. No NAPLs were found near the Site boundaries. Specific areas of o

elevated concentrations of dissolved-phase compounds within the central process area

include:

• MW-80/MW-81 near the chemical (industrial) sewer and down dip from thecentral ditch.

• South of the north landfill north of the existing chlorination plant (near MW-64)and west of the product storage building, where a suspected burial area wasreported.

• MW-71/MW-72, in the area downgradient of the east drum field.

• MW-78/MW-79 area within the blow out area and along strike anddowngradient from the recycle liquor basin.

• Reasor-Hill well area where one to three drums of waste were reportedlydisposed in the well.

These well locations are shown in Figure 2-9. In addition. Figure 2-9 shows the estimated

areal extent of the shallow groundwater plume which contains concentrations of one or

more site-related compounds in excess of the PDCs presented previously in Table 2-1.

When comparing groundwater concentrations in wells completed at depths of greater than

30 feet to the PDCs, wells exceeding the PDCs are located in the following areas:

• Adjacent to the North Burial Area (MW-23A).

• Beneath the Blowout Area (MW-79).

• Along the sandstone bedding units that intersect weathered bedrock in thenorthern portions of the central process area.

0:\ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC P-?^ 9/12/96

The vertical profile of site-related compounds indicates that the concentrations are generally

lower (typically by an order of magnitude) at increasing depth. As would be expected, the

more mobile compounds, such as 4-chlorophenol, have been measured above PDCs while

less mobile compounds such as 2,4-D, and 2,4,5-T, are detected above PDCs less ^m

frequently. The concentration of site-related compounds have been measured above PDCs 22o0at MW-92 (completed to a depth of 126 feet), and have been measured slightly above PDCs

at MW-93 (completed to a depth of 242 ft). This is the most down-dip well in the water-

bearing unit; therefore, the extent of contamination appears to extend beyond this well. A

decision was made to do no further drilling during the RJ because: (1) the toxicity of 4-

chlorophenol is relatively low; (2) few other site-related compounds were found; (3)

groundwater in the area is not used; (4) further delineation would be unlikely to alter the

course of the OU3 FS; and (5) the source of the contamination is most likely related to

burial in the north landfill area. The north landfill area was remediated as part of the 1984

Court Order and is outside of the scope of the RI/FSs for Operable Units 1, 2 and 3.

Because the impact ofNAPL or dissolved-phase contamination from the north landfill area

was addressed by the court action, it was not included in the subsequent studies.

2.6 CONTAMINANT FATE AND TRANSPORT

As discussed in Section 2.5.1, NAPLs are present primarily in the central process area,

north of the central ditch. In fractured bedrock, movement of DNAPL in a downdip

direction (north) within bedding planes, may occur. There is also the potential for some

lateral movement of DNAPL along bedding strike, due to the heterogeneity of the fracture

system in the bedrock.

Concentrations of dissolved phase contaminants are generally relatively high in the area of a

NAPL, due to the tendency of a NAPL to act as a source. Contaminant concentrations

decrease away from a NAPL source, due to natural attenuation within the aquifer. This

decrease in dissolved phase contaminant concentrations, away from the NAPL source area,

0;\ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC -y ^r 9/12/9*

is observed at the site and graphically presented on the isoconcentration maps for Site-

related compounds (Figures 3-42 to 3-49, WESTON, 1992; Figures 3-16 to 3-39,

WESTON, 1995a). The groundwater analytical results from the Phase I and Phase II OU-2

RIs are summarized in Table 3-13 of the respective reports.

Migration of dissolved phase Site compounds is occurring away from source areas in the

direction of groundwater flow. Lateral flow of shallow groundwater occurs in the bedrock.

Under existing conditions these compounds in the eastern part of the Site have the potential

to migrate toward offsite areas. In the western part of the Site. shallow groundwater is

intercepted by the french drain prior to reaching Rocky Branch Creek. This shallow

groundwater from the fractured bedrock can also move vertically along the sandstone

bedding planes and fractures.

Shallow groundwater flow to the west from within the central process area flows toward

Rocky Branch Creek but is intercepted by the existing french drain. Shallow groundwater

flow to the south from areas in the northern portion of the central process area appears to be

impeded and intercepted by the central ditch as evidence by periodic seepage of

groundwater into the central ditch, although the degree to which the central ditch affects

contaminant migration is difficult to quantify. Consistent with these observations, there is

no evidence to indicate that offsite migration of site-related compounds in groundwater has

occurred to the west or south from the central process area.

In the eastern portion of the central process area, groundwater to the east of the groundwater

divide is flowing southeastward toward Marshall Road. Some site-related compounds

originating from sources within the central process area are migrating eastward toward

offsite areas. This assertion is evidenced by the shape of the isoconcentration lines for 2,4-

dichlorophenol presented in Figure 2-8, which is typical of the dissolved-phase compounds

at the Site. Isoconcentration contours for all Site-related compounds are depicted on

Figures 3-42 to 3-49 of the Phase I RI and on Figures 3-16 to 3-39 of the Phase II RI.

0\£CON_530\FOLDERSO-L\HERC-VER\TIWAIVE3DOC ^ -J-J 9/12/96

Site-related compounds were detected to the east of the central process area in samples

collected from MW-89 and MW-94. Although the concentrations in these samples were

much lower than the concentrations reported inside the central process area, the presence of

the site-related compounds at these wells indicates eastward migration.

i~-mooVertically, the migration of dissolved compounds is influenced by the vertical hydraulic ^

ogroundwater gradients with migration potential within the sandstone beds. As previously

discussed in Subsection 2.3.2, the downward hydraulic gradient within the central process

area has facilitated the downward migration of site-related compounds originating in the

northeastern portion of the central process area.

The current usage of groundwater in the vicinity of the Site was evaluated during the 1982

environmental assessment (DISC, 1982) and during the Phase I RI. It was concluded in

Subsection 2.4.2.2 of the Phase I RI report that the nearest water supply wells to the Site

were approximately one mile from the Site boundary. The Phase II RI (as described in

Subsection 4.4.9) concluded that the potential for water supply wells to be impacted by

Site-related compounds was very low (WESTON, 1995a). Concentrations of Site-related

compounds above MCLs or above the PDCs are confined within the Site boundary. The

implementation of pump and treat at the Site will ensure that the migration of Site-related

compounds is controlled.

The rate of the dissolved compound migration depends on the organic carbon sorption

coefficients, molecular weights, solubility in water, and other compound-specific

parameters. The compound concentrations measured in MW-89 and MW-94 are

significantly lower than the concentrations measured in the nearby central process area. For

example, the concentrations for herbicides, tetrachlorobenzene, and 2,3,7,8-TCDD decrease

by more than two orders of magnitude between the wells in the central process area and

those near the eastern boundary; tetrachlorobenzene and 2,3,7,8-TCDD were not detected

near the eastern boundary. The decrease in concentrations appears to be systematic such

that the concentrations are most attenuated for the compounds with the highest molecular

0\ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC - ^p 9/12/96

weights and lowest solubilities. As a result, the migration of chlorophenoxyherbicides.

tetrachlorobenzene, and 2.3,7,8-TCDD appears to be occurring slower than the migration of

the more mobile compounds such as the chlorinated phenols. Overall, the data collected

during the RI indicate that horizontal contaminant migration occurs at a low rate and that

the concentration gradient near the migration front is sharp (WESTON, 1995a).

0\ECON_530\roi-DERSG-l-\HERC-VER\TIWAIVE3DOC -^ ^Q 9/12/96

SECTION 3RESTORATION POTENTIAL

3.1 SOURCE AREA IDENTIFICATION AND CONTROL

As previously discussed, releases of raw materials, intermediate products, or waste, to soilo\

or groundwater within the central process area, may have occurred historically since the Site oo

was constructed. Many remedial measures have been implemented or proposed to control o

these sources, and are discussed in the following paragraphs.

As part of the 1984 Court Order, the following remedial measures were implemented:

• Additions were made to the clay caps at the North Burial Area and the Reasor-Hill Burial Area.

• Vertical groundwater barriers and collection systems (i.e., french drain andslurry wall) were installed at the perimeter of the North Burial Area and theReasor-Hill Burial Area to intercept and collect shallow groundwater. Herculesbelieves that the french drain is performing as designed based on the continuousflow of groundwater captured by the french drain, a decrease in the amount ofNAPL collected by the french drain and the elimination of a former seepage areaon the west side of the north landfill (D. Kielman, pers. comm., Sept. 1996).

• Sediment from the Cooling Pond was excavated and consolidated into anaboveground vault. The Cooling Pond was capped following excavations.

• The thickness of the cap at the Equalization Basin was increased.

• Improved surface water collection systems were installed.

As part of the remedial actions resulting from the Record of Decision (ROD) for OU1 and

Proposed Plan of Action (PPA) for OU2, many of the sources for continued groundwater

contamination will be addressed. For OU1 media, the remedial action consists of the

following major components (U.S. EPA, 1993):

OAECON 530\FOLDERSG-L\HERC-VER\TWA[VE3DOC i i 9/12/96

• Incineration of F-listed process vessel contents, miscellaneous drummed wastes.contents ofPCB transformers, and shredded trash and pallets.

• Incineration and/or reactivation and resuse of spent carbon.

• Treatment, disposal, or resuse of non-F-listed process vessel contents, or onsite ^ooincineration. 00

• Recycle/reuse of decontaminated process equipment, where practicable.

• Consolidation/containment of debris from the demolition of buildings, andprocess equipment.

• Incineration of used solvents, filter spools, etc.

• Treatment and discharge of contaminated water.

For OU2 media, the remedial action is likely to consist of the following major components:

• Excavation and onsite consolidation of soils with TCDD concentrations greaterthan 5 ppb.

• Excavation and offsite incineration of the crystalline tetrachlorobenzene (TCB)and associated spill soils with concentration exceeding 500 ppm.

• Onsite consolidation/containment of containerized soil.

• Removal of the remaining fuel from the underground storage tanks, vacuumcleaning, filling with sand, and sealing.

• Cleaning of the chemical sewer, followed by plugging the sewer access andconstruction of cut-off barriers.

• Cleaning of foundations and curb, including a sealing of foundations and curbswith persistent staining.

3.2 RESULTS OF THE LONG-TERM PILOT EXTRACTION TEST

A long-term pilot groundwater extraction test was performed to collect information to

support design of a potential future groundwater extraction system for onsite containment.

0 \ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC •; ^ 9/12/96

Since site-related compounds had been previously detected in samples collected from MW-

94 near the eastern boundary of the Site. the decision was made to test the water-bearing

unit in which this monitoring well is completed. Accordingly, monitoring well MW-92 was

selected as the pumping well for the test. During the test, groundwater was extracted from

MW-92 at a rate of 4 gallons per minute (gpm) and water level measurements were made at oo

surrounding monitoring wells and piezometers. Several monitoring wells, including MW- o

94, were periodically sampled for phenols, chlorophenols, and chloride to assess changes in

groundwater quality.

Monitoring well MW-92 was selected as the pilot test extraction well based on its high

yield and connection to the local fracture system which made it a likely well where

pumping could improve the groundwater quality near the eastern Site boundary. This

monitoring well is completed within one of the fractured sandstone water-bearing units.

During the pump test, groundwater elevations were monitored at surrounding piezometers

and monitoring wells completed within the same water-bearing unit and in other water-

bearing units. Periodically, groundwater samples were collected from surrounding wells

and analyzed for specific conductance, temperature, phenol, chlorophenols, and chloride to

assess concentration trends for target compounds.

The results of the extended pump test indicated that pumping MW-92 at a rate of 4 gpm

was a sufficient and effective means of achieving hydraulic influence along a part of the

eastern Site boundary. This influence was measured both horizontally and vertically.

Monitoring of drawdown at surrounding wells and piezometers indicated that the lateral

area of hydraulic influence was at least 1020 feet long (measured between MW-24A and

MW-94) and 355 feet wide (measured between MW-93 and MW-72). Down dip hydraulic

influence was measured in MW-93 which has a total depth of 242 feet. MW-93 is

completed 100 feet deeper than MW-92, and is approximately 400 feet north of MW-92.

Figure 3-1 illustrates the minimum areal extent of hydraulic influence as projected onto the

surface established during the pilot groundwater extraction test. The elliptical shape of this

area of influence indicates that during the pumping test, groundwater showed preferential

0 \ECON S50\FOLDERSG-L\HERC-VER\TIWA1VE3DOC -y -^ 9/12/96

®M\X/9S

' I ' :' , MW26»;-®MW-25 , ! '

'^,' ®MW-19 I . ^^

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' " 1 1 ' " " L' ®MW;92

1 \ ' • , i MW-91 ®»M^1 • MW-64® »MW-82 |

1 . - (BMWi PZ-143ei WMW1 1 PZ-147 (C

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Legend

®M\X/-92 PiifiipinqU/cl

^ MW-S7 Observalion Well. Water Levels wereMeasured Manually Using a Wtfleilevel Probe

— - - - - Slurry WallFence LineProperty Boundary

».» - .».. „ Central Process Area Boundary• • Central Ditch

'> Minimal Areal Extent of HydraulicInfluence During Pump Test

N

^

7

s

0 400 800

Scale In Feet

Source: Venae Site Boundary and PhotogrtimmelricSurvey Prepared by West and Associates, Inc

ProJection: Arkansas Coordinate System,Norrh Zone (NAD 1983)

FIGURE 3-1

HYDRAULIC INFLUENCE ZONE DURINGPILOT GROUNDWATER EXTRACTION PROGRAM

VERTAC SITEJACKSONVILLE, AR

3-4

001842

flow along bedding strike within the water- bearing unit. Additionally, drawdown occurred

in wells monitoring up- and down-dip from the pumping well. Some nearby wells

completed at similar depths, but in different strata, did not respond to the pumping at MW-

92, indicating that the area of hydraulic influence created by this pumping was confined to

the strata being tested. The area of hydraulic influence does not define the capture zone for

a pumping system. The capture zone for the final pumping system will be determined rn^

during testing and initial operational phases. 00

The groundwater quality data collected during the pumping test also showed evidence of

the confinement between water-bearing units. The specific conductance measurements

taken at MW-89, which is completed in a separate bedding plane from MW-92, remained

relatively constant over the course of the pump test. In contrast, specific conductance

measurements made at monitoring wells completed in the same bedding plane as MW-92

decreased over the course of the study. A more comprehensive presentation of the data

attained from the pumping test is available in the long-term pilot groundwater extraction

test report (WESTON, 1994).

3.3 SPATIAL EXTENT OF THE TECHNICAL IMPRACTICABILITY ZONE

There are portions of the Site where groundwater may be restored, and other parts where

restoration is unlikely. The characteristics of groundwater contamination are variable, and

account for differences in restoration potential. The three areas of differing restoration

potential are:

• Groundwater located beneath the northern part of the central process area (northof the central ditch), the north landfill and reasor hill landfill. The TI zoneincludes areas north and west of the known and suspected NAPL areas in orderto account for the potential for DNAPL to migrate down dip and along strikewithin the fractured bedrock. The area east of the central process area is notincluded in the TI zone because the groundwater analytical data from this areado not indicate that DNAPL have migrated to the east from the central process

0:\ECON_530\FOLDERS.G-L\HERC-VER\TIWAIVE3.DOC 1 c 9/12/96

area. This zone is depicted on Figure 3-2 and represents the zone where a TIwaiver is warranted (TI Zone).

• Shallow groundwater to the east of the central process area, and deepergroundwater to the north and east of the central process area. It may be possibleto restore groundwater in this area.

• Groundwater to the south of the central ditch. It is expected that groundwaterrestoration is feasible in this area. •• i-

-^-oo

The restoration potential of these three areas are discussed in the paragraphs that follow. §

Primary sources affecting shallow groundwater in the northern portion of the central process

area are NAPLs, some of which are present as residual product trapped interstitially in the

weathered bedrock. Free-phase NAPLs were observed in potentially recoverable quantities

(greater than 1 inch thick layer) at only three locations. At these locations, source recovery

could be implemented to collect groundwater and mobile, recoverable NAPL, if possible,

from areas of higher contaminant concentrations. Within the localized area of recovery, this

will prevent the NAPL from further dissolution into the groundwater and subsequent

migration of contaminants. Recovery of these localized NAPLs, if feasible, would not

result in an overall cleanup of the groundwater system, because non-recoverable residual

NAPLs would remain in the weathered bedrock.

Throughout the northern part of the central process area residual NAPLs are present in

limited quantities or are trapped interstitially such that direct recovery is not possible. There

are no available remediation technologies that could effectively remove the residual product

in the fractured bedrock. In these locations, the NAPL and residual product will continue to

contribute to dissolved-phase concentrations as long as pure product remains in contact with

the groundwater.

Shallow groundwater to the east of the central process area, and deeper groundwater to the

north and east of the central process area exhibit a higher potential for groundwater

0\£CON_530\FOLDERSG-L\HERC-VER\TIWA[VE3.DOC 1 r 9/12/963-6

001845

restoration. In these areas, groundwater concentrations are typically above PDCs for the

more mobile site-related compounds. Residual product, although possibly present, is not

expected to be present to the same degree as noted for the northern central process area.

Restoration may be possible using conventional pump and treat methods in this area.

Performance monitoring will be used to track the progress of remediation efforts in this

area, and will be used to evaluate the practicability of restoration.^otoor—<

Groundwater within the central process area south of the central ditch (except for the §

Reasor-Hill Burial Area and Boiler House Area) does not contain contaminants above the

PDCs. This situation may be primarily due to the effect of the central ditch and the fact that

production and storage activities were less common in this area. This area is a candidate for

restoration of groundwater quality.

3.4 APPLICABLE TECHNOLOGIES

As part of the OU3 FS, technologies were identified and screened to determine their

potential application to groundwater remediation. Screening criteria included

effectiveness, implementability and relative cost. The subsections that follow give a

concise synopsis of the screening presented in the OU3 FS, focusing on the ability of

these technologies to achieve groundwater remediation within the Tl Zone.

3.4.1 Subsurface Drains

A subsurface drain, such as the existing french drain, is a permeability trench designed to

intercept and collect lateral groundwater flow. These drains are typically constructed of

perforated section of pipe that lies horizontally below the static water level. The trench is

backfllled with a high permeability material and the covered with low permeability

material. These systems can remove a mobile NAPL as demonstrated by the existing

french drain. In most of the areas within the TI Zone, however, the NAPL is not mobile,

0:\ECON_530\FOLDERSG-L\HERC-VER\TrWAlVE3.DOC •? o 9/12/96

rather it is trapped interstitially in the weathered bedrock. Therefore, this technology is

not expected to be capable of restoring groundwater within a reasonable time frame.

3.4.2 Vertical Barriers

Vertical barriers are technologies that are used to passively direct groundwater flow

around a waste or contaminated soils. Examples of vertical barrier technologies include r--i-

slurry walls, sheet piling, and injection grouting. Since these technologies do not employ 2o

a groundwater collection technique, they are typically paired with a groundwater °

collection technology.

3.4.3 Groundwater Extraction Wells and Product Recovery Wells

These similar technologies employ an active withdrawal mechanism, and transport the

collected liquids for treatment. Groundwater extraction wells typically extract

groundwater at a moderate to high volume (greater the 1 gpm). Groundwater extraction

wells are most effective at removing dissolved phase contamination, but can remove

NAPL that is entrained in groundwater or NAPL that flows into the extraction well.

Groundwater extraction wells are also effectively used to contain groundwater by

inducing hydraulic control. Product recovery wells are generally low volume (less that 1

gpm) and are designed to target the zone where the LNAPL or DNAPL is present.

Technologies employed in product recovery wells include low volume product recovery

pumps, hand-bailing, and the use of enhanced recovery methods. Enhance recovery

methods are further discussed in Subsection 3.3.4. In the TI Zone, their effectiveness in

groundwater restoration would be very limited because of the residual non-recoverable

NAPL that is trapped interstitially in the weathered bedrock.

0\ECON_530\TOLDERSG-L\HERC-VER\TrWAIVE3DOC -} Q 9/12/96

3.4.4 Enhanced Recovery Methods

In addition to or in combination with product recovery wells, enhanced recovery methods

may facilitate the recovery of NAPLs under certain situations. The primary objective of

these techniques is to increase NAPL mobility through the injection of selected fluids.

chemical agents, and heat. The techniques can be subdivided into three main categories: ooi-

induced gradient/water flooding, chemically enhanced recovery, and thermally enhanced °2oorecovery.

Induced gradient/water flooding techniques involve the installation of water injection wells

to provide increased hydraulic gradients and groundwater flow rates. Chemically enhanced

recovery could be implemented in association with water flooding techniques and involves

the injection of surfactants, cosolvents, or alkaline agents into the NAPL regions of the

groundwater system. These agents are designed to increase the solubility of NAPL; thereby

increasing their dissolved concentrations in the groundwater and increasing the

effectiveness of conventional groundwater extraction wells for recovering this material.

Certain chemical additives, particularly the surfactants, may lower the interracial tension

between the NAPL and the groundwater. This would result in higher mobility of the NAPL

with improved recovery attained by downgradient extraction wells. Similarly, polymers

could be added to groundwater to increase its viscosity. This increased viscosity of the

groundwater is designed to increase the effectiveness of the "sweeping" effect of water

flooding, particularly when used in combination with the chemical agents.

Thermally enhanced recovery would involve the injection of steam or hot water into the

contamination zone creating a flood of hot water that is designed to more effectively drive

the NAPL toward the recovery well. This enhanced mobility results from a decrease in

NAPL viscosity upon heating, and increased NAPL solubility with increased temperature.

In some situations, the heating of the NAPL by this process reduces its density to less than

0 \ECON_530\FOLDERSG-L\HERC-VER\T1WAIVE3DOC •} i (\ 9/12/96

that of the groundwater. This technique could be used to convert a DNAPL to LNAPL

causing it to rise to the top of the saturated zone where it may be more easily recovered.

There is a significant risk involved in even testing these technologies. Increasing the

mobility of the NAPL, as these technologies are designed to do. may result in uncontrolled

migration that is not captured by groundwater extraction wells. Further, these technologies

are not proven effective in subsurface restoration to MCLs. Overall, although enhanced l-

recovery methods may increase the effectiveness of DNAPL recovery, the use of these ^

technologies in the complex fractured Site geology carries the risk of greatly deteriorating

groundwater quality, and causing offsite migration of contaminants.

3.4.5 In Situ Biological Treatment

In situ biological treatment is a technique for treating contaminated groundwater in place

though controlled microbial degradation. Typically, oxygen and nutrients are added to

the groundwater through injection wells to enhance the natural biodegradation of organic

compounds. This technology has only recently been attempted to degrade chlorinated

organics similar to those that exist at the Site. Some of the Site related compounds my be

amenable to biodegradation, however there was no evidence that TCDD can be

biodegraded in groundwater. Even if the Site related compounds can be biodegraded. the

technology is not proven to be effective on NAPLs. Because they are virtually pure

product, the NAPLs will impose a significant demand for oxygen and nutrients. The

delivery of these reagents will be limited by the physical and chemical properties of the

Site soils and groundwater system.

3.4.6 Excavation

Excavation as means to remediate groundwater would involve the physical removal of all

materials where the NAPL is present. When residual NAPL contamination is limited to

shallow soils and the extent of contamination is localized and well-defined, excavation of

0\ECON_S30\FOLDERSG-L\HERC-VER\TrWAlVE3DOC 1 1 1 9/12/96

the affected soils can be an effective solution. Discrete spill areas that do not penetration

the consolidated weathered bedrock are examples where this technique would have a

positive impact on local groundwater quality. Because NAPLs at the Site are discontinuous

(as depicted on Figure 2-9), excavation of all unconsolidated soils in the northern portion of

the central process area would be required. This excavation would not be effective because

the NAPLs are trapped in both the consolidated and unconsolidated weathered bedrock, andt_^

excavation could not be implemented in consolidated rock. Thus there would be no ^0

r—<

improvement in groundwater quality associated with excavation. §

3.4.7 Vapor Extraction

Soil vapor extraction (SVE) is a physical method for removing volatile compounds from the

unsaturated zones of soils. SVE is only applicable to unsaturated materials and is not

effective in the saturated zone. This technology could be applicable to NAPLs when they

are volatile and present above the water table. In some instances, steam or hot air could be

injected to allow volatilization of lower volatility compounds, although the effectiveness of

this has not been extensively demonstrated. The water table is relatively shallow which

results in a thin vadose zone where SVE could be applied. Lowering of the water table by

pumping is sometimes implemented in an effort to increase the unsaturated zone, however,

this can result in unwanted mobilization and sinking of DNAPL. The technology has not

been demonstrated for removal of non-volatile compounds or NAPL treatment. Due to the

non-volatile nature of some of the contaminants, the heterogeneous geology of the Site, and

groundwater flow within fractured bedrock, it does not appear that vapor extraction could

be easily implemented, nor is it likely to be effective.

3.4.8 Air Sparging

Air sparging is an in-sim separation process in which air is injected into groundwater to

facilitate volatilization of the target compounds; the stripped gases are collected using SVE.

The process is similar to air stripping, but is performed in-situ. Air sparging can be

0\ECON_S30\FOLDERS.G-L\HERC-VER\TIWA1VE3.DOC -, 1 9/I2/96

particularly effective for remediation of groundwater containing volatile organic

compounds which are easily stripped from the groundwater. Some semi-volatile organic

compounds and certain fuels have also been shown to be effectively removed by this

technology. Most of the compounds of concern at the Site. however, are not volatile and

will not be effectively stripped by an air sparging system. The geological conditions and

physical characteristics of the contaminants at the Site would make air sparging difficult to ^>n

implement. The fractured bedrock at the Site would make uniform dispersion of the oc

oinjected air difficult to achieve. Instead, the sparged air is likely to short-circuit along larger

fractures and leave much of the groundwater untreated. Additionally, air sparging may

complicate the groundwater remediation by mobilizing or spreading the NAPLs present in

the fractured bedrock.

3.4.9 Electrokinetics

Electrokinetic remediation is an emerging technology that is currently being tested on a

bench- and pilot-scale basis. It is designed to be an in-situ separation and removal

technique for heavy metals and some organic compounds in soils and groundwater. The

process involves placing an anode and a cathode in boreholes located opposite each other in

the area to be treated. When an electrical current is applied, an acid front is generated at the

anode eventually migrates through the pore conditioning fluid to the cathode. Pore

conditioning fluid is removed at the boreholes and treated before reinjection. Although the

technology has shown some success in removing phenols, the effectiveness on TCDD has

not been determined. In addition, uncontrolled mobilization of the NAPLs due to the

injection of fluids is also an important consideration, especially when considering the

complex geology where the NAPLs are present.

3.5 Remedial Alternatives

The OU3 FS identified three alternatives to remediate groundwater. These alternatives

recognized the impracticability of groundwater restoration within the TI Zone, but also

0:\ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3 DOC 1 1 1 9/12/96

provided varying strategies to affect source removal where possible. The actions

identified in these alternatives are as follows:

Alternative 1: No Action - This alternative was included as required by the National

Contingency Plan (NCP). Under this alternative, no additional measures would be

undertaken. Continued operation and maintenance of the french drain and water treatment

system would continue as specified in the 1984 Court Order, until the year 2014. No ^oo

further active remedial actions would be implemented to remove the site-related 3o

groundwater contaminants or to prevent migration of these contaminants. There are no

additional costs associated with this alternative above continued operation of the existing

groundwater containment and treatment system, and monitoring program.

Alternative 2: Groundwater Pump and Treat - Under this alternative the following actions

would be taken:

• Installation of groundwater extraction wells (or use of existing wells) in theeastern part of the central process area to control eastward movement ofgroundwater and to draw the dissolved-phase toward the extraction wells forremoval and treatment.

• Reconditioning, of the Reasor-Hill Well to remove recoverable NAPLs.Reconditioning of the Reasor-Hill Well may involve flushing the well to removeaccumulated sediments, redrilling the well to remove obstructions, or inserting anew screened casing within the well, depending on conditions encountered.Phase separation would be used prior to aqueous phase treatment in the existingwater treatment system.

• Implementation of deed restrictions to limit future use of groundwater fromcontaminated parts of the Vertac property.

• Groundwater monitoring to demonstrate the effectiveness of the remedialactions being implemented under this alternative.

• Operation and maintenance (O&M) activities associated with the remedialactions being implemented under this alternative.

0 \ECON530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC -, , A 9/12/96

The estimated 30 year present worth cost of this alternative is $2.525,000.

Alternative 3: Ground-water Pump and Treat with Source Recovery - Under this

alternative the following actions would be taken:

*« i• Installation of groundwater extraction wells (or use of existing wells) in the °°

eastern portion of the central process area to control eastward movement of §groundwater.

• Reconditioning the Reasor-Hill Well to remove recoverable NAPLs.

• Installation of source recovery for the removal of NAPL and/or highconcentration dissolved-phase contaminants at locations within the northernportion of the central process area where the highest concentration dissolved-phase contaminants and/or recoverable NAPL are identified (i.e., in the vicinityof the northwest railroad track). Pre-design field testing would be used todetermine the best removal technique (i.e., hand-bailing, product recoverypumps, low rate recovery pumps) for the source recovery.

• Implementation of deed restrictions to limit future use of the Vertac propertyand prevent usage of groundwater.

• Groundwater monitoring to demonstrate the effectiveness of the remedialactions being implemented under this alternative.

• Operation and maintenance (O&M) activities associated with the remedialactions being implemented under this alternative.

The estimated 30 year present worth cost of this alternative is $3,550,000.

0\ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3.DOC -3 i r 9/12/96

SECTION 4APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS

(ARARS) FOR WHICH A TECHNICAL IMPRACTICABILITYWAIVER IS REQUIRED

4.1 SAFE DRINKING WATER ACT

The Safe Drinking Water Act (SDWA) (42 USC 300f et seq.) mandated U.S. EPA to

establish regulations to protect public health from contaminants in drinking water. Under

this act, U.S. EPA has promulgated primary and secondary drinking water standards that are

applicable to public water systems. Public water systems are defined as systems for the

provision of piped water for human consumption the serve at least 25 persons. Primary

drinking water standards are enforceable standards that are not to be exceeded in public

water supplies. Secondary drinking water standards are nonenforceable (at the Federal

level) standards that are intended to serve as guidelines for use by states in regulating water

supplies.

4.1.1 National Primary Drinking Water Standards

National Primary Drinking Water Standards are established in 40 CFR 141 and are

expressed as maximum contaminant limits (MCLs). MCLs for 30 toxic compounds,

including the 14 compounds adopted as RCRA MCLs, have been adopted as enforceable

standards for public drinking water systems (40 CFR 141.11-141.16). An MCL is required

to reflect the technical and economic feasibility of removing the contaminant from the water

supply. The MCLs applicable to groundwater at the Site are identified on Table 4-1.

The SDWA (40 CFR 142.4 and 142.5) allows public water suppliers to obtain exemptions

and variances from complying with MCLs under certain situations. However, it must be

shown that noncompliance will not result in an unreasonable risk to human health.

0\ECON_530\FOLDERSG-L\HERC-VER\TIWAIVE3DOC A i 9/I2/96

Table 4-1

Safe Drinking Water Act Drinking Water StandardsVertac Site. Jacksonville, Arkansas

Site-RelatedCompound

MCL(mg/1)

SMCL(mg/1)

Chloride2-Chlorophenol4-Chlorophenol2,4-Dichlorophenol2,6-Dichlorophenol2.4.5-Trichlorophenol2.4.6-TrichlorophenolToluene 1Tetrachlorobenzene2,6-D2,4-D 0.072,4,6-T2,4,5-T2,4,5-TP (Silvex) 0.052,3,7,8-TCDD (Dioxin) 3.00E-07

250

NOTES:MCL = Maximum contaminant limit.SMCL = Secondary maximum contaminant limit.- = No level has been established.

U ECON HO'FOLDERS G-L HERC.VER'.TAB.) I DCX"

4-2

4.1.2 Secondary Drinking Water Standards

Secondary Drinking Water Standards are established for 13 parameters in 40 CFR 143 and

are expressed as Secondary Maximum Contaminant Levels (SMCLs). The SMCLs

applicable to the Site are identified on Table 4-1. The SMCLs non-enforceable (at the's0

Federal level) aesthetic-based guidelines (e.g., taste and odor) that consider available ^o

treatment technologies and cost of treatment. §

4.2 ARKANSAS STATE GROUNDWATER QUALITY PROTECTION

STRATEGY

The objective of Arkansas' groundwater strategy is to formulate and recommend a

management program to protect the quality of groundwater resources. The Arkansas

Groundwater Quality Protection Strategy outlines water quality criteria for groundwater

(drinking water) within the state. Arkansas has adopted the recommended standards for

drinking water set by the Safe Drinking Water Act. The Arkansas Department of Health

uses the National Primary Drinking Water Standards (MCLs) in setting the criteria to which

public water supplies must adhere.

0 \ECON530\FOI-DERS.G-L\HERC-VER\TIWA1VE3 DOC A -} 9/12/96

SECTION 5CONCLUSIONS

Previous releases of raw materials, intermediate products, and waste have impacted

groundwater at the Site. The nature of the impact to groundwater is variable, with the

majority of the impact located within the central process area, north of the central ditch.m

The groundwater constituents are present both in the NAPL and dissolved phases. The °°o

NAPL has been observed in the unconsolidated and consolidate weathered bedrock, while °

the dissolved-phase constituents have been observed in the unconsolidated and

consolidated weathered, and the fresh bedrock.

A TI waiver from federal and state MCLs is warranted for groundwater located beneath the

central process area, north of the central ditch and beneath the north landfill and reasor hill

landfill, extending to include an area 250 feet to the north (see Figure 3-2). In this area,

groundwater restoration is not achievable because NAPLs are present as residual product

trapped interstitially in the weathered bedrock. Free-phase NAPLs were observed in

potentially recoverable quantities (greater than 1 inch thick layer) at only three locations.

Recovery of NAPL in these areas would prevent further dissolution into the groundwater

but would not result in an overall cleanup of the groundwater system, because residual

NAPLs would remain in the weathered bedrock even if the mobile phase was recovered. At

many other locations in the northern part of the central process area, NAPLs are present in

limited quantities or are trapped interstitially such that direct recovery is not possible.

There are no available remediation technologies that could effectively remove the residual

product in the bedrock. NAPL and residual product will continue to contribute to

dissolved-phase concentrations as long as pure product remains in contact with the

groundwater. Since some of these contaminants, particularly 2,3,7,8-TCDD, have relatively

low solubilities and will biodegrade slowly. They will persist in the soil and rock matrices

for many decades.

0:\ECON_530\FOLDERSG-L\HERC-VER\TIWA1VE3DOC c 1 9/I2/96

SECTION 6REFERENCES

D'Appolonia, 1984. Remediation Construction Plan Package, Proposed OnsiteEnvironmental Remediation, Vertac Chemical Corporation, Plant Site, Jacksonville,Arkansas.

00t l

DISC (Developers International Services Corporation), 1982. Final Report for °2Environmental Assessment Study, Vertac Chemical Corporation Site, Jacksonville, §Arkansas, Developers International Services Corporation.

U.S. EPA, 1993a. Record of Decision, Vertac Onsite Operable Unit 1, June 1993.

U.S. EPA, 1993b. Guidance for Evaluation the Technical Impracticability of Ground-Water Restoration. EPA/540-R-93-080, September 1993.

WESTON, 1989. Work Plan Remedial Investigation/Feasibility Study; Vertac Site,Jacksonville, Arkansas, July 1989.

WESTON, 1991. Remedial Investigation/Focused Feasibility Study (RI/FFS) forOperable Unit I; Vertac Site, Jacksonville, Arkansas, January 1991.

WESTON, 1992. Final Phase I RI Report for Operable Unit 2, Vertac Site, Jacksonville,Arkansas, December 1992.

WESTON, 1994. Long-Term Pilot Groundwater Extraction Test, Vertac Site,Jacksonville, Arkansas, June 1994.

WESTON, 1995a. Phase II RI Report for Operable Unit 2, Vertac Site, Jacksonville,Arkansas, September 1995.

WESTON, 1995b. Feasibility Study for Operable Unit 3 Media, Vertac Site,Jacksonville, Arkansas, September 1995.

WESTON, 1995c. Feasibility Study for Operable Unit 2 Media, Vertac Site,Jacksonville, Arkansas, April 1995.

WESTON, 1995d. Baseline Risk Assessment for Operable Unit 2 Media, Vertac Site,Jacksonville. Arkansas. April 1995.

OAECON_530\FOLDERS G-L\HERC-VER\T[WAIVE3DOC f. 1 9/I2/96