remedial action work plan for groundwater former timex...

REMEDIAL ACTION WORK PLAN FOR GROUNDWATER

FORMER TIMEX FACILITY LITTLE ROCK, ARKANSAS

Prepared for:

Timex Group USA Middlebury, Connecticut

Prepared by:

Weston Solutions, Inc. 45 Constitution Avenue, Suite 100 Concord, New Hampshire 03301

June 10, 2015

Work Order No. 13568.004.002

G:\PROJECTS\13568004\Planning Documents\Groundwater RAWP\Timex Groundwater RAWP 06-9-15.doc 10 June 2015

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TABLE OF CONTENTS

Section Page

1. INTRODUCTION.......................................................................................................... 1-1

2. SITE DESCRIPTION AND BACKGROUND ............................................................ 2-1

2.1 HYDROGEOLOGIC SETTING ......................................................................... 2-2

2.1.1 Geology ................................................................................................. 2-3 2.1.2 Hydrogeology ....................................................................................... 2-3

2.2 NATURE AND EXTENT OF GROUNDWATER CONTAMINATION .......... 2-5

2.3 SELECTED REMEDIAL ALTERNATIVE FOR GROUNDWATER .............. 2-6

3. BASIS OF DESIGN ....................................................................................................... 3-1

3.1 TREATMENT AREA ......................................................................................... 3-1

3.2 TREATMENT DEPTH ....................................................................................... 3-2

3.3 OXIDANT SELECTION ..................................................................................... 3-3

3.4 OXIDANT DOSAGE AND VOLUME .............................................................. 3-4

3.5 INJECTION METHOD ....................................................................................... 3-5

3.6 INJECTION SPACING ....................................................................................... 3-6

3.7 INJECTION SEQUENCING ............................................................................... 3-7

4. REMEDIAL ACTION IMPLEMENTATION ........................................................... 4-1

4.1 SITE ACCESS ..................................................................................................... 4-1

4.2 PERMITS ............................................................................................................. 4-2

4.3 SUBSURFACE UTILITIES ................................................................................ 4-2

4.4 SITE CONTROL ................................................................................................. 4-2

4.5 INJECTION POINT INSTALLATION .............................................................. 4-3

4.6 ISCO INJECTIONS ............................................................................................. 4-4

4.6.1 Permanganate Solution ......................................................................... 4-4 4.6.2 Permanganate Storage ........................................................................... 4-4 4.6.3 Utility Water ......................................................................................... 4-5 4.6.4 Mixing and Injection System ................................................................ 4-5 4.6.5 Spill Control Measures ......................................................................... 4-6 4.6.6 Neutralization Solution ......................................................................... 4-7

4.7 HEALTH AND SAFETY .................................................................................... 4-7

4.8 REPORTING ....................................................................................................... 4-8


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TABLE OF CONTENTS (Continued)

Section Page

5. SCHEDULE.................................................................................................................... 5-1

6. REFERENCES ............................................................................................................... 6-1

APPENDIX A MATERIAL SAFETY DATA SHEET


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LIST OF FIGURES

Title

Figure 1 Site Location Map

Figure 2 Site Plan

Figure 3 Distribution of TCE in Shallow Sand Aquifer

Figure 4 Distribution of TCE in Deep Sand Aquifer

Figure 5 Injection Locations

Figure 6 Cross Section Schematic of Injection System

Figure 7 Injection Well Construction

Figure 8 Direct Push Injection Boring Schematic

Figure 9 Sodium Permanganate Injection System Schematics

Figure 10 Groundwater Remediation Implementation Schedule

LIST OF TABLES

Title

Table 1 Sodium Permanganate Injection Design: Source Area Treatment

Table 2 Sodium Permanganate Injection Design: Downgradient Plume Treatment


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LIST OF ACRONYMS

1,1-DCE 1,1-Dichloroethene

1,1,1-TCA 1,1,1-Trichloroethane

ADEQ Arkansas Department of Environmental Quality

Airport Little Rock National Airport

CAO Consent Administrative Order

COPCs contaminants of potential concern

ft feet/foot

ft/day feet per day

ft/year feet per year

FTN FTN Associates, Ltd.

g/kg grams per kilogram

Groundater RAWP Remedial Action Work Plan for Groundwater

ISCO in situ chemical oxidation

MCL Maximum Contaminant Levels

mg/kg milligrams per kilogram

mg/L milligrams per liter

MNA monitored natural attenuation

PCE Tetrachloroethylene

psi pounds per square inch

PVC polyvinyl chloride

RAA Remedial Alternative Analysis

RADD Remedial Action Decision Document

RAL Remedial Action Level

TCE trichloroethylene

Timex Timex Group USA

UIC Underground Injection Control

VOC volatile organic compound

WESTON® Weston Solutions, Inc.

SECTION 1

INTRODUCTION


1-1

1. INTRODUCTION

Weston Solutions, Inc. (WESTON®) has prepared this Remedial Action Work Plan for

Groundwater (Groundwater RAWP) on behalf of Timex Group USA, Inc. (Timex) for the former

Timex facility previously located at 2215 Crisp Drive in Little Rock, Arkansas. This Work Plan

was prepared to satisfy the requirements of the First Amendment to Consent Administrative

Order (CAO) LIS-04-206 between Timex and the Arkansas Department of Environmental

Quality (ADEQ or Department).

In August 2011, Timex completed a Remedial Alternative Analysis (RAA) (WESTON, 2011)

that evaluated various remediation technologies to address soil and groundwater contamination

associated with the Site. The RAA recommended excavation and off-site disposal of source area

soils and treatment of shallow groundwater using in situ chemical oxidation (ISCO). These

technologies would be combined with institutional controls and monitored natural attenuation

(MNA) to mitigate potential future exposures and ultimately return the groundwater to

productive use, respectively. The RAA was accepted by ADEQ and the Department

subsequently issued a Remedial Action Decision Document (RADD) that described the approved

remedy. The RADD was issued for public comment on 20 January 2014 and finalized on

27 February 2014 (ADEQ, 2014). Contemporaneously, Timex and ADEQ agreed upon on an

Amendment to the CAO that specified the selected remedy and listed required milestones. The

CAO amendment requires that a Remedial Action Work Plan be submitted that provides for

ISCO treatment via injection of an appropriate oxidant into the shallow groundwater to treat

groundwater exceeding 1.96 milligrams per liter (mg/L) of trichloroethylene (TCE).

This Groundwater RAWP builds on the results of a Treatment Technology Pilot Study that

evaluated various oxidants and injection technologies and describes the tasks that will be performed

to inject the selected oxidant into the shallow groundwater. A schedule for implementing the work

is also included. Performance monitoring for the groundwater remedy is described in the approved

Revised Groundwater Monitoring Plan dated September 2014 (WESTON, 2014a).

SECTION 2

SITE DESCRIPTION AND BACKGROUND


2-1

2. SITE DESCRIPTION AND BACKGROUND

For the purposes of the remedial action, the “Site” is considered to be the former Timex facility

located at 2215 Crisp Drive in Little Rock, Arkansas, as well as all contiguous property owned

by the Little Rock National Airport Authority (Airport). Figure 1 shows the approximate location

of the Site. The 9-acre former Timex parcel is zoned as light industrial (I-2) and is currently a

fenced vacant lot partially covered by aged asphalt and grassy vegetation (Figure 2). Land uses

in the vicinity of the Site include vacant land, Civil Air Patrol and Army Reserve facilities,

aircraft support services, and light industrial operations. A residential neighborhood of small

single-family homes is located about 700 feet (ft) north of the former Timex parcel.

The subject property is owned by the Airport and was formerly leased to Timex. Timex

historically manufactured watches, clocks, and cameras at the property between 1947 and August

2000, when operations ceased and all products were removed. The Airport demolished the

vacant 225,000 square-foot historical split-level manufacturing building in January 2005. Prior to

1947, the property had been used for the storage and assembly of aircraft engines and for cotton

storage.

Manufacturing processes formerly conducted by Timex at the property included cutting,

stamping, grinding, sanding, and plating metal and aluminum watch bezels and case backs, as

well as injection molding of plastic watch cases. Various metals including copper, chromium,

nickel, and gold were used in the metal plating processes. Oils and industrial solvents were used

in the various metal working processes.

Prior to discontinuation of manufacturing operations, the Airport conducted a Phase I

Environmental Site Assessment. A Phase II investigation conducted jointly by Timex and the

Airport discovered that past operations involving chlorinated solvents had affected groundwater

quality beneath the property and recommended that further investigation be conducted to define

the source and extent of the impact. As a result, Timex entered into a CAO for voluntary action

with ADEQ on 28 December 2004. The CAO required that Timex submit a Site Investigation

Report and a RAA. The Site Investigation Report was submitted on 23 August 2007 by

FTN Associates Ltd. (FTN), and was conditionally approved by ADEQ in a letter dated

2 December 2008. Additional documents detailing subsequent investigations conducted in an


2-2

effort to respond to the ADEQ conditions presented in the approval letter have since been

submitted.

Following completion of the site investigation, a RAA was performed to evaluate remedial

options in accordance with the second requirement of the CAO. The RAA recommended a

remedial approach that consisted of a combination of active remediation, institutional controls,

and MNA. The active remediation would consist of excavation and off-site disposal of source

area soils and ISCO treatment of TCE in the shallow aquifer. The RAA describes the remedy

that formed the basis of the RADD that was issued on 27 February 2014.

Following issuance of the RADD and signing of the Amendment to the CAO, Timex

submitted the required planning documents including a Revised Groundwater Monitoring Plan

(WESTON, 2014a), Revised Treatment Technology Pilot Study Work Plan (WESTON, 2014b),

and a Revised Soil Remedial Action Work Plan (WESTON, 2014c). The baseline groundwater

monitoring round specified in the Revised Groundwater Monitoring Plan was conducted in

December 2014, and the results were reported in a Baseline Groundwater Sampling Report dated

February 2015 (WESTON, 2015a). Similarly, the ISCO pilot test was conducted in accordance

with the Revised Treatment Technology Pilot Study Work Plan, and the results were presented in

the Treatment Technology Pilot Study Report dated March 2015 (WESTON, 2015b). The results

of the baseline groundwater sampling and the ISCO pilot test were integral to the design of the

groundwater remedy.

2.1 HYDROGEOLOGIC SETTING

The Site is relatively flat and located about 255 ft above mean sea level. Surface/storm water

drainage is primarily to the west through shallow, unlined storm drains, and ditches that

discharge to a larger ditch along Bond Avenue that is part of the City of Little Rock drainage

system. Flow within the larger ditch continues south for approximately 1 mile and enters

Fourche Creek, which discharges to the Arkansas River approximately 0.9 mile north of the

former Timex property (FTN, 2007a).


2-3

2.1.1 Geology

Regional geology is characterized by 75 to 100 ft of Quaternary alluvium overlying older, more

consolidated, Tertiary deposits of the Wilcox and Midway Groups. The Quaternary alluvium is a

relatively thick sequence of fluvial deposits from the Arkansas and Mississippi Rivers and their

tributaries that is composed primarily of sand, silt, and clay. These deposits make up the Surficial

Alluvial Aquifer System.

Based on information gathered during previous investigations (FTN, 2007b), site geology is

characterized by a surficial silt and clay unit overlying two predominate sand layers separated by

a confining clay unit. The units are summarized below in descending order from the ground

surface.

Surficial Silt and Clay: A sequence of interbedded sandy silts and clays extending from approximately 2 to 13 ft below the ground surface. Thin discontinuous silty sand lenses are also present and may be associated with paleo channels. A silty clay or clay layer 2 to 4 ft thick typically marks the base of this unit (also sometimes referred to as the “upper clay”).

Shallow Sand: This unit ranges in thickness from 3 to 14 ft and consists of reddish brown to brown silty sands and sandy silts.

Confining Clay: The shallow sand unit is underlain by a reddish-brown to brown clay that is approximately 14 to 22 ft thick.

Intermediate Sand: The intermediate sand layer, which has a thickness ranging from 3.5 to 6 ft, is located within the confining clay unit described above and consists of silt, silty sand, and poorly sorted sands. This layer is discontinuous across the Site and may represent a paleo channel deposit.

Deep Sand: The deep sand unit is poorly graded fine to medium-grained, loose sand with a silty sand interval directly below the overlying clay stratum. This unit is about 35 ft thick and extends to a depth of roughly 60 or 65 ft below grade, where it rests unconformably on the more consolidated Tertiary age deposits.

2.1.2 Hydrogeology

Two distinct hydrostratigraphic zones have been identified at the Site; the shallow sand aquifer

and the deep sand aquifer.


2-4

The shallow sand aquifer corresponds to the shallow sand unit described above. Hydrogeologic

conditions within the shallow sand aquifer in and around the Site vary from being completely

saturated and partially confined (south) to unsaturated (north). Groundwater flow within this unit

is predominantly north and northeast toward the Arkansas River, although there is a minor

westward component towards Bond Avenue that is likely related to a paleo stream channel.

Groundwater level measurements indicate that groundwater in the vicinity of the Site is present

at depths ranging from between 5 to 17 ft below grade. An average site-wide hydraulic gradient

of 0.0087 was measured for the shallow sand aquifer during the Baseline Groundwater Sampling

round. Hydraulic conductivity estimates for the shallow sand, based on slug tests performed on

monitoring wells, average 2 to 4 feet per day (ft/day). The calculated seepage velocity for the

shallow sand aquifer was about 30 feet per year (ft/year). Based on the limited saturated

thickness and hydraulic conductivity of this zone, it is not considered a viable source of

groundwater for economic uses. A well search conducted by FTN did not document any current

use of the shallow groundwater.

The deep sand aquifer corresponds to the deep sand layer and is confined in all areas of the Site.

Groundwater flow in the deep sand aquifer is to the northeast towards the Arkansas River, which

is the regional groundwater discharge point. Potentiometric surface levels in the deep sand

aquifer rise to within about 14 to 18 ft of the ground surface. An average hydraulic gradient of

0.0011 was measured for the deep sand aquifer in the vicinity of the former Timex property

during the Baseline Groundwater Sampling round. Hydraulic conductivity estimates for the deep

sand, based on slug tests performed on monitoring wells, average 115 to 175 ft/day. The

calculated seepage velocity for the deep sand aquifer was about 165 ft/year. The greater saturated

thickness (35 ft) and hydraulic conductivity of this zone suggests that it could be used as a water

source, although municipal water is available at the Site and all surrounding areas. A well search

performed by FTN confirmed two nearby industrial supply wells (Little Rock Crate and Basket

and the former Northwest Hardwoods) are screened in the deep sand, but four other wells listed

in online databases could not be located and are presumed to no longer be in operation.

Groundwater elevation monitoring has suggested that there is some hydraulic communication

between the two groundwater zones. Vertical hydraulic gradients between the shallow and deep

sand aquifer are strongly downward, with groundwater potentiometric surface elevation


2-5

differences between the two units ranging from about 6 to 9 ft in the vicinity of the Site. The

vertical gradient remains downward northeast (downgradient) of the former Timex property; but

the differences in potentiometric elevations between the two aquifers decreases as you move

away from the Site (FTN, 2007b).

2.2 NATURE AND EXTENT OF GROUNDWATER CONTAMINATION

Investigation of environmental conditions has been ongoing at the Site for the last 10 years.

Hundreds of samples of various environmental media (including soil, groundwater, surface

water, sediment, and indoor air) have been collected and analyzed for potential site

contaminants. The investigations have shown that some industrial solvents and their breakdown

products are present in the environment as a result of manufacturing operations at the facility.

Some of these compounds have migrated downgradient and extend off the former Timex

property to the west, north, and east. Two suspected source areas were identified: a former

plating room/effluent treatment plant area within the footprint of the former manufacturing

building, and a storm drain located near the northwest corner of the former building. Removal of

contaminated soils exceeding the RADD cleanup goal of 0.78 milligrams per kilogram (mg/kg)

TCE from the two source areas was completed in May 2015, thereby addressing the source of the

groundwater contamination.

The RADD identified the chemicals of potential concern (COPCs) for groundwater at the Site as:

1,1,1-Trichloroethane (1,1,1-TCA) 1,1,2-Trichloroethane 1,1-Dichloroethane 1,2-Dichloroethane 1,1-Dichloroethene (1,1-DCE) Cis-1,2-dichloroethene 1,4-Dioxane Freon 113 Tetrachloroethylene (PCE) TCE Vinyl Chloride Manganese

The COPCs for groundwater were identified based largely on exceedances of the United States

Environmental Protection Agency Maximum Contaminant Levels (MCLs). For those compounds


2-6

that did not have MCLs, the Regional Screening Levels for Tapwater were used. Manganese was

not specifically named as a chemical of concern in the Site Investigation Report (FTN, 2007b)

because it was not released into the environment as a result of former manufacturing operations,

but rather is a naturally-occurring compound that can be mobilized by biodegradation of the

chlorinated solvents that were a result of historical releases at the Site. However, ADEQ has

required that manganese be included as a COPC for groundwater and that concentrations in

groundwater be evaluated during the MNA portion of the remedy.

The most pervasive COPC for groundwater is the industrial solvent TCE and its breakdown

products, including 1,1-DCE. Concentrations of TCE as high as 32 mg/L have been historically

observed in groundwater beneath the Site, although more recent data show that the maximum

TCE concentration has decreased to 12 mg/L as of December 2014 (WESTON, 2015a).

Remediation of impacted soils associated with the western end of the storm drain on the north

side of the former building identified several pipes entering the catch basins near MW-18S from

within the footprint of the former building and these are believed to be the release point for the

TCE contamination into the storm drain. The pipes, catch basins, and impacted portion of the

storm drain were removed in April-May 2015. Figures 3 and 4 show the estimated extent of

volatile organic compound (VOC) contamination in the shallow and deep aquifers, respectively,

based on the results of the baseline groundwater sampling round completed in December 2014.

A small area of 1,1,1-TCA contamination formerly existed in shallow groundwater in the

vicinity of monitoring well MW-10S that was believed to be related to the former plating

room/effluent treatment plant located in the south central portion of the former manufacturing

building. However, since removal of the former Timex building in 2005, 1,1,1-TCA

concentrations in groundwater have decreased and no longer exceed the cleanup criteria

(WESTON, 2015a).

2.3 SELECTED REMEDIAL ALTERNATIVE FOR GROUNDWATER

As mentioned above, Timex completed a comprehensive RAA that screened 24 different

remedial technologies, of which 10 were determined to be potentially applicable to the Site. The

ten applicable technologies were used to develop four remedial action alternatives, which were


2-7

then evaluated against nine performance criteria. Based on this evaluation, ADEQ selected the

approved remedy for the Site that is described in the RADD.

The approved remedy includes the application of institutional controls that will limit use of

properties that lie within the area of the shallow groundwater plume to industrial activities (as

defined therein) and prevent the use of groundwater on-site and off-site within the area affected

by the deep groundwater contamination. Deed restrictions already have been obtained from the

Airport to limit site use to industrial activities and to prevent the use of deep groundwater

on-site. Similarly, an ordinance has been obtained from the City of Little Rock covering the

United States Army Reserve Center adjacent to the Site and limiting its use to industrial

activities and prohibiting the use of groundwater. Deed restrictions also have been obtained

restricting groundwater use for many off-site properties within the area affected by the deep

groundwater contamination, and work is ongoing to obtain either deed restrictions or an

ordinance regarding the remaining properties.

Active groundwater remediation consisting of ISCO treatment of shallow groundwater exceeding

the Remedial Action Level (RAL) of 1.96 mg/L of TCE will be performed to mitigate potential

vapor intrusion risk to on-site future industrial workers.

SECTION 3

BASIS OF DESIGN


3-1

3. BASIS OF DESIGN

The groundwater remedial action will consist of ISCO treatment of shallow groundwater that

exceeds the RAL of 1.96 mg/L of TCE, and MNA for the remaining areas. The MNA monitoring

program was provided in the Revised Groundwater Monitoring Plan (WESTON, 2014a) and

approved by ADEQ. This section provides the engineering design basis for the ISCO treatment.

3.1 TREATMENT AREA

A comprehensive groundwater sampling round was conducted in December 2014 to provide a

baseline condition for design of the ISCO treatment and also for comparison during post-

treatment performance monitoring for the ISCO and MNA remedies (WESTON, 2015a). The

baseline groundwater sampling included all existing monitoring wells at the Site. The TCE

results were plotted on a site map and isoconcentration contours were developed to estimate the

extent of shallow groundwater exceeding the RAL of 1.96 mg/L (see Figure 3). The extent of the

shallow groundwater requiring treatment with ISCO is shown on Figure 5 and corresponds with

the 2,000 micrograms per liter isoconcentration contour shown on Figure 3.

The treatment area has been divided into two zones for the purposes of the ISCO treatment;

source area and downgradient plume. The source area relates to the zone around the former

storm drain where it is believed that TCE may have been released. During removal of the storm

drain, confirmation samples from the bottom of the excavation showed TCE concentrations as

high as 360 mg/kg in the surficial silt and clay layer. These TCE concentrations are related to the

release of TCE to the storm drain (2 to 3 ft below grade) and migration of the TCE downward

through the surficial silt and clay layer to the shallow sand aquifer. The unsaturated soil was

removed during the soil remediation but residual contamination remains in the saturated soil

above the shallow sand aquifer. This residual contamination could act as a continuing source to

groundwater contamination in the underlying shallow sand aquifer. Therefore, ISCO treatment in

the source area will include this layer.

The downgradient plume includes the shallow sand aquifer downgradient of the source area

where TCE exceeds the cleanup goal of 1.96 mg/L. In that zone, TCE is restricted largely to the

shallow sand aquifer itself with only minor penetration of the TCE into the overlying silt and


3-2

clay surficial layer and the underlying confining clay layer via diffusion. Under those conditions,

ISCO treatment of the shallow sand aquifer will be sufficient to treat all of the TCE because the

high permanganate dosage will drive the permanganate into the underlying and overlying

material via diffusion similar to the TCE.

3.2 TREATMENT DEPTH

The RADD requires that the ISCO treatment be conducted on the shallow groundwater aquifer.

Extensive mapping of the various groundwater zones was performed by FTN between 2004 and

2008 (FTN, 2007a,b). Geologic cross-sections were developed based on over 130 soil borings

and 60 monitoring wells, depicting the depth and thickness of the shallow sand aquifer. Those

cross-sections were used to design the depth of the ISCO injection points. The shallow sand is

approximately 7 to 8 ft thick in the vicinity of the former Timex property and is encountered at a

depth of approximately 11 to 12 ft below grade. The shallow sand aquifer thins to the north and

is only 3 to 4 ft thick at the northern end of the treatment area near MW-29S, where it is

encountered at a depth of about 12 to 13 ft.

Because there is some variation in the depth and thickness of the shallow sand across the

treatment area, a conservative thickness of 10 ft was selected for the ISCO treatment. The depth

of the ISCO treatment will vary based on location (see Figure 5). Treatment points east of the

alley between the former Timex property and the Civil Air Patrol will be approximately 2 ft

shallower than those to the west of the alley. This is to take into account a change in grade

between the two areas that is related to a short concrete retaining wall at the edge of the parking

lot, west of the alley. The injection points east of the parking lot will target the 8- to 18-ft

interval while the injection points west and north of the parking lot will target the 10- to 20-ft

interval. Figure 6 is a schematic cross-section of the injection system showing the relative depths

of the injection points in relation to the shallow sand aquifer.

For the ISCO injection wells that will be used to treat the downgradient portion of the plume, a

10-foot (ft) screened section will be used to straddle the shallow sand aquifer. The injected

oxidant will preferentially flow into the sandy material providing maximum treatment of the

target zone via convection but still providing some treatment to the overlying and underlying

finer-grained material via diffusion.


3-3

For the direct-push ISCO borings used to treat the source area, oxidant will be injected into three

different 2-ft intervals. This will facilitate convective flow of oxidant into the overlying and

underlying finer-grained material to provide greater treatment for those soils in the source area

where higher TCE concentrations are present. The injection volumes will be varied such that the

middle zone gets a larger percentage of the total amount for each injection point to offset the

higher permeability in that zone.

3.3 OXIDANT SELECTION

The oxidant selected for this Site is sodium permanganate. Sodium permanganate has the

greatest persistence of all of the common oxidants, often persisting in the subsurface for 1 to

2 years after injection. This is a great advantage because it allows the oxidant more time to

diffuse into finer-grained material and react with the contaminants, which provides more

complete treatment with less chance for rebound. Sodium permanganate is preferred over

potassium permanganate because it is over 10 times more soluble in water, which enables a

stronger solution to be used and minimizes the volume of fluid injected. Sodium permanganate is

very effective at treating chlorinated ethenes such as PCE, TCE, and their breakdown products.

The results of the laboratory treatability test (WESTON, 2015b) showed that TCE was

completely destroyed by the sodium permanganate, even at the lowest dose tested.

A 20% sodium permanganate solution will be used for the injections in the source area and a

10% solution will be used in the downgradient plume. Sodium permanganate is typically

delivered as a 40% solution (which is close to its maximum solubility) to reduce shipping costs.

However, 40% sodium permanganate is slightly viscous and more problematic to handle so it is

routinely diluted on-site with water to create less dilute solutions for injection. Aside from being

easier to handle and less of a safety concern, the density of 20% sodium permanganate is nearly

identical to that of TCE. That means that the 20% solution will tend to follow the same pathways

as the TCE when it was released. This is why 20% is proposed for the source area, where it is

believed the TCE was released. A 10% sodium permanganate solution will be used for the

downgradient plume because it will result in a larger injection volume and mix more fully with

the groundwater, thereby providing better distribution of permanganate between the wider-

spaced injection points in this area.


3-4

3.4 OXIDANT DOSAGE AND VOLUME

The results of the treatability test (WESTON, 2015b) showed that the TCE was fully destroyed

by the lowest dose [2.0 grams per kilogram (g/kg)] evaluated. The treatability test was conducted

using soil and groundwater from the most highly-contaminated area of the Site (vicinity of MW-

18S). This area was confirmed to be the primary release point for TCE during the soil

remediation when a pipe was discovered leading from the former Timex building into the catch

basin located just east of MW-18S. Further, MW-18S has consistently had the highest observed

TCE concentrations in the shallow sand aquifer, up to 17.3 mg/L. Because the treatability test

was conducted using the worst-case soil and groundwater conditions, and the lowest dose of

sodium permanganate tested (2.0 g/kg) fully destroyed the TCE, that dose represents the upper

bound that would be required to achieve the cleanup goal. It is likely that a much lower dose

would be required in downgradient areas where the TCE concentrations are significantly less. To

account for this conservancy, the ISCO injections will be performed as a series of injections

based on a percentage of the upper bound dose.

The dosage calculations are shown in Tables 1 and 2 for the source area and downgradient

plume, respectively. The calculations use the upper bound of 2.0 g/kg as a conservative

assumption for the source area treatment due to the higher TCE concentrations there and a more

reasonable value of 1.0 g/kg for the downgradient plume. It should be noted that both sets of

dosage calculations use a treatment thickness of 10 ft, which is another conservative assumption

given the mapped thickness of the shallow sand aquifer (3 to 8 ft thick) as discussed above. This

is especially true for the downgradient plume area where the advective flow zone is estimated to

be only 3 to 4 ft, and further justifies using the lower dose rate of 1.0 g/kg. Based on the

calculations in Tables 1 and 2, the total estimated volume of sodium permanganate solution

required for maximum treatment would be approximately 420 gallons of 20% solution for each

source area direct push injection boring and approximately 2,580 gallons of 10% solution for

each downgradient injection well. The volume is greater for the downgradient points because a

more dilute solution is being applied and the injection points are spaced further apart and

therefore each point must treat a larger area of the aquifer.

Because the injection volume calculations are based on several conservative assumptions,

including treatment zone thickness, TCE concentration, and unit dose rate; it is most likely that a


3-5

smaller amount of sodium permanganate will be required to achieve the cleanup goals. To

account for this unknown, the ISCO treatment will be performed as a series of smaller injections

rather than a single injection of the full amount. This will allow Timex to customize the amount

of permanganate needed in each area; thereby minimizing the amount of residual permanganate

remaining after treatment is complete. Note that unused permanganate will auto-degrade over

time, but it is a slow process often requiring more than 3 years and adds more manganese to the

aquifer than is necessary.

The initial injection would be 50% of the total estimated volume, so approximately 210 gallons

of 20% solution per source area injection boring and 1,290 gallons of 10% solution per

downgradient injection well. Post-injection monitoring of permanganate concentrations in

groundwater per the Revised Groundwater Monitoring Plan will be used to determine where and

when the second injection would be performed. The volume of permanganate used for the

second injection would be adjusted based on the results of the monitoring, but it is anticipated

that it would be approximately 25% of the total estimated volume. The third injection would be

the final 25%. WESTON’s experience at similar sites is that the area of each subsequent

injection round is smaller than the previous one. The initial 50% volume is typically sufficient to

fully attain the cleanup goal around the edges of the plume, leaving only the center of the plume

requiring additional treatment. Similarly, after the second injection, more of the plume attains the

cleanup goal leaving only a small source area requiring final treatment with a third injection.

Occasionally, a fourth or even fifth injection round is needed to treat recalcitrant locations,

typically right at the release point. But because there is no way to conclusively determine where

those areas are before beginning the treatment, this is the most efficient way to achieve the

cleanup goal without needlessly overdosing the aquifer.

3.5 INJECTION METHOD

A field pilot test was conducted to evaluate three different ISCO injection methods: direct push

drilling equipment, small-diameter injection wells, and standard 2-inch-diameter monitoring

wells (WESTON, 2015b). In general, all three injection methods performed well and were able

to attain favorable injection rates (approximately 7 gallons per minute) with only moderate

backpressure [<75 pounds per square inch (psi)]. The direct push method was found to be more


3-6

capable of injecting oxidant into lower-permeability layers than either the injection wells or the

monitoring wells due to the shorter screen length. As a result, the direct push method provides

more control with regard to injecting the oxidant into specific zones and therefore can provide

better vertical distribution of the oxidant. This is particularly useful for source area treatment

where TCE contamination is more likely to have penetrated into the overlying and underlying

finer-grained material.

The use of longer-screen injection wells is applicable for downgradient applications at this Site

where the TCE is largely confined to the shallow sand aquifer, with only minimal diffusion into

the overlying and underlying finer-grained material. The injection wells and monitoring wells

performed similarly, with no real advantage for one over the other. Both hydraulic and thermal

responses to the test injections were consistently observed at distances of 15 to 20 ft in the more

permeable zones. These observations were based on injection of approximately 70 gallons of

water, so injection of the larger volumes associated with the full-scale remediation would result

in a proportionally larger radius of influence.

A combined approach to oxidant injection will be used at this Site. Direct push injection borings

with three 2-ft-long injection intervals per boring would be used to treat the source area to

provide the best horizontal and vertical distribution of the oxidant. Small-diameter injection

wells (10-ft screen) will be used to create injection barriers to treat downgradient portions of the

plume. These injection wells will be used to apply a larger volume of oxidant into the shallow

sand aquifer and allow the natural groundwater flow to distribute the oxidant downgradient. The

injection wells more easily facilitate future injections than the direct push borings and also

provide additional monitoring points to assess the distribution of oxidant within the aquifer and

VOC monitoring to verify the effectiveness.

3.6 INJECTION SPACING

The direct push injection borings will be installed on a 20-ft grid within the source area. The grid

lines will be off-set by 10 ft to provide better distribution of the oxidant. Subsequent injection

borings will be off-set from the initial borings by 10 ft to provide an even finer spacing in areas

requiring further treatment. The results of the pilot study (WESTON, 2015b) showed excellent

hydraulic and thermal tracer response at a distance of 20 ft based on an injection volume of


3-7

approximately 70 gallons depth interval per location. This compares favorably with the planned

injection volume of 210 gallons per point for the first injection. The fact that subsequent

injections will be off-set from the initial injection will provide a 10-ft effective spacing. Figure 5

shows the layout of the initial injection grid; subsequent grids will be off-set from the one shown

by 10 ft.

For the downgradient plume, existing infrastructure prevents injection on a finely-spaced grid as

is proposed for the source area. The Civil Air Patrol building and Crisp Drive occupy a

significant portion of the downgradient plume. As a result, the approach is to use the small

diameter injection wells to inject a large volume of oxidant and rely on convective groundwater

flow to distribute the oxidant downgradient, beneath the surface infrastructure. The injection

wells will be installed as a series of treatment barriers perpendicular to the main axis of the

plume (see Figure 5). The spacing of points within the barriers is 30 ft, based on the results of the

pilot study that show good hydraulic and thermal response at a minimum of 20 ft for an injection

volume of 70 gallons. The planned initial injection volume for the barrier wells is more than

18 times greater at 1,290 gallons. The injection barriers will be spaced at 60-ft intervals, based

on a conservative seepage velocity of 30 ft per year and an assumed oxidant persistence of

2 years. The 30 ft per year seepage velocity was calculated using the measured hydraulic

gradient (0.0087) and the lowest measured hydraulic conductivity of 2 ft/day. It is likely that the

actual hydraulic conductivity for the shallow sand aquifer in the downgradient area is closer to

the higher end of the range because the thickness of the aquifer is known to be less, yet the

hydraulic gradient does not change. Therefore, the seepage velocity is expected to be at least

60 ft/yr. Oxidant monitoring in accordance with the Revised Groundwater Monitoring Plan will

be used to verify the performance of the injection barriers. Additional oxidant injections or

injection points will be added, if necessary, to achieve the cleanup goal of 1.96 mg/L TCE.

3.7 INJECTION SEQUENCING

The sequence of ISCO injections must be performed properly to avoid pushing contaminated

groundwater out of the treatment zone. Injections in the source area via the direct-push borings

will be performed around the perimeter of the treatment area and working inward. This will

create a barrier of oxidant around the edges of the treatment zone and ensure that contaminated


3-8

groundwater above the RAL cannot be pushed outside the treatment zone without coming into

contact with the oxidant.

For the downgradient plume, the small diameter injection wells will all be installed before

injections in this area are initiated. As with the source area, injections will be conducted into the

perimeter injection wells first, and then working inward. The injections will be performed

starting downgradient and moving southward towards the source area.

SECTION 4

REMEDIAL ACTION IMPLEMENTATION


4-1

4. REMEDIAL ACTION IMPLEMENTATION

The remedy selected for groundwater at the Timex Site is the injection of a chemical oxidant in

shallow groundwater to attain the RAL of 1.96 mg/L TCE. As detailed in the Basis of Design,

the oxidant selected for this Site is sodium permanganate. The estimated maximum dosage

required to treat the groundwater is roughly 167,900 pounds of sodium permanganate. Because

the maximum dosage was calculated using a series of conservative assumptions, the actual

amount of sodium permanganate that will be injected is likely much less than that. To account

for this, the treatment will be conducted in a phased approach consisting of multiple injections.

The initial injection will be 50% of the estimated maximum dose (23,750 gallons of 20% sodium

permanganate in the source area injection borings and approximately 47,700 gallons of 10%

solution in the downgradient plume injection wells). Permanganate and VOC monitoring will

then be conducted in accordance with the approved Revised Groundwater Monitoring Plan

(WESTON, 2014a) and that data will be used to determine the scope and timing of subsequent

injections. It is believed that three injections will be required to achieve the RAL in all areas of

the Site, but it could be fewer or more than that.

The sodium permanganate will be injected into the subsurface using a combination of small

diameter injection wells (in downgradient areas) and direct push injection borings (in the source

area) as show on Figure 5. A total of 150 injection points are planned. The sodium permanganate

will be delivered as a 40% solution and diluted on-site to 20% and 10% solutions using potable

water from a fire hydrant. A trailer-mounted injection pumping system will be used to inject the

permanganate solutions into each injection point. For the initial injection event, approximately

210 gallons of 20% sodium permanganate will be injected into each direct push injection boring

and 1,290 gallons of 10% solution will be injected into each small diameter injection well. The

amount of sodium permanganate needed for subsequent injections and the locations requiring

injections will be determined based on the permanganate and VOC monitoring results.

4.1 SITE ACCESS

All areas where ISCO injections will be performed are located on property owned by the Airport.

Timex has a signed Access Agreement in place with the Airport that includes performance of


4-2

this groundwater remediation work. Timex will coordinate closely with the Airport during all

phases of the groundwater remediation.

4.2 PERMITS

The ISCO injection points are considered Class V injection wells and authorization is required

under the Underground Injection Control (UIC) Permit by Rule to perform the injections.

Authorization under the UIC program was obtained from ADEQ for the pilot study injection of

potable water. Timex will submit a request to modify that authorization to include the full-scale

injections of sodium permanganate once this Groundwater RAWP is approved.

Timex will also notify the City of Little Rock and coordinate with the local fire and police

precincts with regard to the type and amount of chemical that will be stored on-site during the

injections.

4.3 SUBSURFACE UTILITIES

Prior to beginning installation of the small-diameter injection wells or direct-push injection

borings, the planned drilling locations will be marked in the field and Arkansas One Call will be

contacted to mark subsurface utilities. The Airport, Central Arkansas Water, and City of Little

Rock will also be directly contacted and asked to mark out any subsurface utilities that they are

aware of that might not be covered by Arkansas One Call. Further, locations of previously

unknown utilities discovered during the soil remediation work (water and gas lines) will also be

marked in the field.

4.4 SITE CONTROL

The former Timex property is fully contained by a 6-ft security fence. Similarly, the area to the

north of Crisp Drive is fenced. However, the area west of the former Timex property and south

of Crisp Drive, encompassing the Civil Air Patrol building and associated parking lot, are not

fenced. Temporary construction fencing will be employed during injection events to extend the

existing permanent fence across the alley west of the former Timex property and around the

work area to restrict off-hours access.


4-3

It is anticipated that the alley that extends southward from Crisp Drive along the western

boundary of the former Timex property will be closed to public traffic during injections in that

area. Because this is a dead-end alley that is controlled by the Airport and receives almost no

daily traffic, this temporary closure will not adversely impact any local businesses or residents.

The alley was closed for several weeks during the soil remediation without any known impact.

4.5 INJECTION POINT INSTALLATION

The sodium permanganate will be injected into the subsurface using a combination of small

diameter injection wells (in downgradient areas) and direct push injection borings (in the source

area) as shown on Figure 5.

The small diameter injection wells will be constructed as shown on Figure 7 and will be installed

using direct push methods. A total of 37 small diameter injection wells will be installed

(Figure 5). The 2.5-inch-diameter direct-push casing will be pushed to the design depth based on

location (between 18 and 20 ft below grade). A removable steel plug will be deployed on the

drilling rods to keep the casing free of soil as the casing is advanced. Each well point will consist

of 10 ft of 1-inch-diameter, 10-slot polyvinyl chloride (PVC) screen and an appropriate length of

1-inch-diameter riser pipe. The well points will be installed by inserting the 1-inch-diameter

PVC well casing into the direct-push casing and retracting the casing. Filter sand will be added

to a depth of 2 ft above the top of the screen as the casing is removed. A 3-ft-thick layer of fine-

grained bentonite pellets (‘crumble’) will be placed in the borehole annulus above the sand pack

and hydrated in place with potable water. The remainder of the borehole annulus will be filled

with medium bentonite chips. This will help to reduce the potential for daylighting of the

injection water. An appropriate size road box will be installed at the surface to protect the

injection wells. Figure 7 shows a schematic of the small diameter injection wells.

The direct push injection borings will be performed using a 2-ft-long injection tip attached to the

direct-push drilling rods. The injection tip will be advanced to the target depth. Once the target

depth has been reached, a threaded fitting will be attached to the top of the casing such that the

water injection system (pump, flow meter, pressure gauge, flow control valve, etc.) can be

connected. The 20% sodium permanganate solution will then be pumped into the drilling rods

and the rate and back pressure monitored and recorded until the desired volume of oxidant has


4-4

been delivered. The injection system will be disconnected and the injection tip will then be

pushed to the next injection interval. The injection system will be reconnected and the second

interval will be treated. This process will be repeated for the third treatment interval. Figure 8

shows a schematic of the direct push injection borings. Approximately 113 direct push injection

borings will be installed.

4.6 ISCO INJECTIONS

A single location will be used for the storage, mixing, and distribution of the sodium

permanganate for all injection points (direct push injection borings and small diameter injection

wells). The system is described below.

4.6.1 Permanganate Solution

Sodium permanganate solution (40% by weight) will be delivered to the Site in bulk shipments

of 5,000 to 10,000 gallons via tanker truck. Approximately 18,400 gallons of 40% sodium

permanganate will be needed to complete the initial injection round at this Site. In order to

provide a solution with the proper density and viscosity for injection, the permanganate will be

diluted with water to either a 10% or 20% solution prior to injection into the subsurface.

4.6.2 Permanganate Storage

The 40% sodium permanganate solution will be stored in two 8,000-gallon temporary storage

tanks located in the paved parking area at the north end of the former Timex property as shown

on Figure 5. Spill containment consisting of 10-mil polyethylene sheeting with bermed sides, or

equivalent pre-manufactured spill containment devices will be used around both tanks and an

adjacent mixing area where smaller 300-gallon totes will be filled with either 10% or 20%

sodium permanganate solution. The bermed sides will be constructed by wrapping the edges of

the sheeting around and under sandbags or similar to create a berm of at least 1 ft in height. The

containment area will be constructed with a volume at least 10% greater than the volume of the

stored permanganate solution.


4-5

4.6.3 Utility Water

Potable water will be obtained from a fire hydrant located on-site near the permanganate storage

and mixing area. This is the same hydrant that was used to supply water during the Treatment

Technology Pilot Study (WESTON, 2015a). This water will be used for dilution of the

permanganate prior to injection and for equipment decontamination purposes.

4.6.4 Mixing and Injection System

The diluted sodium permanganate solution will be delivered to each injection point using

300-gallon totes. These totes consist of a polyethylene tank contained in a metal framework that

is suitable for transport. The totes will be placed within the designated solution mixing area using

a fork lift, filled, and then transported to each injection location. The solution mixing area will be

within the fixed containment structure around the two 40% sodium permanganate storage tanks

(Figure 5). The containment area for the sodium permanganate solution mixing process will be

surrounded by caution tape during daytime working areas. The mixing area will be cleaned and

secured whenever authorized personnel are not on-site. Signs will be posted at the mixing area,

prohibiting access by unauthorized personnel.

To create the 20% sodium permanganate solution needed for source area injections, 175 gallons

of water from the fire hydrant will be added to a 300-gallon tote inside the bermed permanganate

mixing area. Then, 125 gallons of 40% sodium permanganate will transferred from the

8,000-gallon storage tanks into the tote to create 300 gallons of 20% sodium permanganate

solution. Note that the dilution from 40% to 20% solution is calculated on a weight basis so the

volume of water and 40% solution that must be combined to create a 20% solution is not equal.

The 10% solution for the small-diameter injection wells will be created by adding 230 gallons of

water to a 300-gallon tote and then adding 50 gallons of 40% sodium permanganate for a total of

280 gallons of 10% solution.

The tote containing the dilute solution (10% or 20%) will then be removed from the mixing area

and placed in a portable secondary containment structure on a vehicle (trailer, pickup truck, box

truck, etc.) using the fork lift. The vehicle will then be used to transport the tote to the specific

injection location where the tote will be off-loaded into another portable containment structure.

The tote will be connected to the trailer-mounted injection system, as depicted on Figure 9.


4-6

Chemical absorbent mats will be placed around the base of each injection point and beneath all

fittings and valves to provide containment of any leaks or drips in the injection system.

The injection system will consist of a motor and pump as well as various pressure valves and

flow meters to allow measurement and control of the permanganate injection. The injection

system is depicted in Figure 9. A manifold system may be used to inject permanganate into

multiple injection points at one time.

Once the piping connections between the tote, pump, and injection point are tight, the injection

pump will be activated and permanganate will be pumped into the well. The solution will be

injected at pressures generally less than 75 psi (consistent with those observed during the pilot

study), at a rate specific to each injection point based on the yield of the point. After the correct

volume of sodium permanganate has been pumped into each injection point, the valve will be

closed to that injection point and the lines will be flushed with clean water prior to

disconnecting. The flush water (containing dilute concentrations of permanganate) will be

pumped into the injection point.

Once the tote is empty, a new full tote will be transported from the mixing area and the empty

tote will be returned to the mixing area to be refilled. This process will be repeated until all

injection points have received the prescribed volume of sodium permanganate

4.6.5 Spill Control Measures

As noted above, all handling of permanganate will be conducted in areas with secondary spill

containment. This will minimize the potential for releases of sodium permanganate and help to

ensure public safety during permanganate handling. All transport of sodium permanganate

between the storage/mixing area and the injection points will be in the transport-rated totes

within a vehicle-mounted containment structure. The totes are commonly used to provide safe

over-the-road transport of chemicals, and thus will provide safe containment for sodium

permanganate when it is transported the short distances between the storage/mixing areas to the

injection points. An emergency pump and hose will be maintained on-site to pump large spills

from the storage/mixing area back into the storage tanks or totes, if needed. Smaller spills will be


4-7

cleaned with chemical absorbent pads and/or diluted to less than 6% and neutralized with the

neutralization solution described below.

As a further precaution, the storm water catch basins located near the permanganate storage and

mixing area will be removed from service during the period when permanganate is stored

on-site. This will prevent permanganate from reaching any surface water body in the unlikely

event of a catastrophic failure of the storage tanks and secondary containment structure. Catch

basins will be opened and the permanganate storage area secured during periods of heavy rain to

prevent flooding of the area.

4.6.6 Neutralization Solution

A sodium thiosulfate neutralization solution will be prepared for use in the unlikely event of a

spill outside the containment areas. Prior to neutralization, any spills will be diluted with water to

a maximum of 6% permanganate in order to provide for a safe neutralization reaction. Garden-

type pump sprayers filled with the neutralization solution will be distributed around the areas of

the Site where work is being performed. A quantity of 100 gallons of this solution will be

maintained on-site for immediate use. Additional dry sodium thiosulfate will be maintained

on-site in the event that additional neutralization solution needs to be prepared. For small spills,

equipment cleaning, stain removal, etc., a solution of 30 parts 3% hydrogen peroxide, 40 parts

5% food grade white vinegar, and 30 parts water will be used.

4.7 HEALTH AND SAFETY

A Health and Safety Plan for this Site was developed in accordance with the federal

Occupational Safety and Health Administration under the Occupational Safety and Health Act of

1970, and 29 U.S.C. 651 as amended. A copy of the Health and Safety Plan, including the

Emergency Response and Contingency Plan and the Material Safety Data Sheets will be

maintained on-site.

Sodium permanganate is a strong oxidizer; it will react with acids, bases, reducing agents,

peroxides, combustible organics, metal powders, oil, grease, sulfites, oxalates, and all other

oxidizable inorganic chemicals. It can cause extreme burns to skin, eyes, and internal organs if

exposure occurs. It can also increase the flammability of combustible material and cause


4-8

spontaneous combustion of wood, cloth, and other flammable materials. The Material Safety

Data Sheet for sodium permanganate is included as Appendix A.

The sodium permanganate will be stored in a location away from contact with acids, peroxides,

combustible organics, metals powder, oil, grease, and other chemicals that react adversely. Also,

combustible material (including wood) will be kept separated from sodium permanganate.

Proper personal protective equipment will be used to mitigate exposure for workers handling the

sodium permanganate. This will include Saranex (coated Tyvek) or equivalent chemical-resistant

coveralls, apron as necessary, safety glasses or face shields, nitrile surgical inner gloves, nitrile

outer gloves, and chemical resistant boots or boot covers. An eye wash and emergency shower

will be maintained on-site when permanganate is present to allow immediate flushing of eyes or

skin that comes in contact with the permanganate.

Prior to injecting sodium permanganate or persulfate, all equipment will be inspected and all

couplings will be tested for leaks with a solution containing water only. All couplings will be

wire tied. Prior to disconnecting couplings, the head pressure within the system will be released

and allowed to dissipate.

4.8 REPORTING

The groundwater remediation activities associated with the first injection will be documented in

the Monthly Updates submitted to ADEQ each month. An annual Groundwater Summary Report

will be provided after 1 year of groundwater performance monitoring per the approved Revised

Groundwater Monitoring Plan (WESTON, 2014a). That report will include a description of the

groundwater remediation and monitoring activities, including the volume of permanganate

injected into each point, dates, and photographs. A surveyed site plan will be included that shows

the locations of all injection points. The report will also include groundwater contour maps for

the two hydrostratigraphic units as well as summary tables, trend graphs, and maps presenting

the analytical result. The results will be used to assess the effectiveness of the ISCO treatment

and recommendations for subsequent injections, if necessary, will be provided. The Groundwater

Summary Report will be submitted to ADEQ for review and approval.

SECTION 5

SCHEDULE


5-1

5. SCHEDULE

Once approval of the Groundwater RAWP is obtained from ADEQ and the modified UIC

authorization is received, the remediation activities will be implemented in a phased approach.

The injection and drilling equipment will be mobilized to the Site. The small diameter injection

wells will be installed first, then the initial oxidant injection round will be conducted. The direct-

push injection borings will be conducted first, starting around the perimeter of the treatment area

and working towards the center. Once the direct-push injections have been completed, the

injections into the small diameter injection wells will be conducted. Once all injections have

been completed, the drilling and injection equipment will be demobilized and the permanganate

monitoring will be initiated. The permanganate monitoring will continue in accordance with the

Revised Groundwater Monitoring Plan (WESTON, 2014a) until the data (permanganate levels

and TCE concentrations) suggest that the majority of the permanganate has reacted and a second

injection is warranted. At that time, the drilling and injection equipment will be remobilized to

the Site and the second injection will be performed in the same manner as the first injection. This

process will continue until the cleanup goal of 1.96 mg/L TCE is achieved in all areas of the

shallow sand aquifer. Monthly Updates and Annual Groundwater Summary Reports will be

provided to ADEQ in accordance with the approved Revised Groundwater Monitoring Plan.

The anticipated duration for each task once the remediation has been initiated is provided below:

Planning and Preparation 12 weeks Mobilization 3 weeks Injection Well Installation 3 weeks Direct Push Injections 4 weeks Injection Well Injections 4 weeks Demobilization 2 weeks Permanganate Monitoring 12-24 months Report Preparation 4 weeks

A graphic schedule is included as Figure 10. In total, the initial ISCO injection will be completed

within 8 months of ADEQ approval of this Groundwater RAWP.

SECTION 6

REFERENCES


6-1

6. REFERENCES

ADEQ (Arkansas Department of Environmental Quality). 2014. Response to Comments and Final Decision on the Remedial Action Decision Document (RADD), Former Timex Property, AFIN 60-00120, Little Rock, Pulaski County, Arkansas. February.

FTN (FTN Associates, Ltd). 2004. Field Sampling Plan, Former Timex Facility, Little Rock Arkansas. June.

FTN. 2007a. Additional Investigation Summary Memorandum, Former Timex Facility, Little Rock Arkansas. 6 March.

FTN. 2007b. Site Investigation Report, Former Timex Facility, Little Rock Arkansas. 23 August.

WESTON (Weston Solutions, Inc.). 2011. Remedial Alternatives Analysis, Former Timex Facility, Little Rock, Arkansas. August.

WESTON. 2014a. Revised Groundwater Monitoring Plan, Former Timex Facility, Little Rock, Arkansas. September.

WESTON. 2014b. Revised Treatment Technology Pilot Study Work Plan, Former Timex Facility, Little Rock, Arkansas. September.

WESTON. 2014c. Revised Soil Remedial Action Work Plan, Former Timex Facility, Little Rock, Arkansas. November.

WESTON. 2015a. Baseline Groundwater Sampling Report, Former Timex Facility, Little Rock, Arkansas. February.

WESTON. 2015b. Treatment Technology Pilot Study Report, Former Timex Facility, Little Rock, Arkansas. March.

FIGURES

Figure 10

Groundwater Remediation Implementation ScheduleFormer Timex Facility, Little Rock, Arkansas

A Groundwater Summary Report will be submitted to ADEQ at the end of each year of performance monitoring.

4 10 11 183 5 6 157 8 9 171413

Injection Well Installation

Procurement of Subcontractors and

Equipment, Permitting

Mobilization and Site Preparation

ADEQ Approval of Groundwater Remedial

Action Work Plan

161 2 12 Task

Weeks

36Weeks

19 20 21 22 23 24 25 26 32 33 34 3527 28 29 30

Demobilization

Injection Well Injections

Direct Push Injections

Performance Monitoring

Task31

6/8/2015

TABLES

Table 1Sodium Permanganate Injection Design

Source Area Treatment

Line Item Unit Value

1 Permanganate dose from pilot test g NaMnO4/1000g soil 2.0

2 Permanganate dose from pilot test lb NaMnO4/lb soil 0.002

3 Width of treatment zone ft 80

4 Length of treatment zone ft 512

5 Thickness of treatment zone ft 10

6 Volume of treatment zone ft3 409,600

7 Volume of treatment zone yd3 15,170

8 Unit weight of soil tons/yd3 1.50

9 Weight of soil in treatment zone tons 22,756

10 Weight of soil in treatment zone lb 45,511,111

11 Pounds of NaMnO4 per treatment zone lb 91,022

12 NaMnO4 solution strength % 40%

13 Pounds of 40% NaMnO4 solution needed lb 227,556

14 NaMnO4 density lb/gal 11.40

15 Total volume 40% NaMnO4 solution needed gal. 19,961.01

16 Water added to make 20% NaMnO4 solution gal. 27,546.20

17 Total volume 20% NaMnO4 solution to be injected gal. 47,507.21

18* Number of injection points (based on field pilot test) ea 113

19 40% solution needed for each well gal. 177


Notes: * The number of injection points is based on the results of the field pilot test which suggested that a spacing of 20 ft is conservative.

Table 2

Sodium Permanganate Injection Design

Downgradient Plume Treatment

Line Item Unit Value

1 Permanganate dose from pilot test g NaMnO4/1000g soil 1.0

2 Permanganate dose from pilot test lb NaMnO4/lb soil 0.001

3 Width of treatment zone ft 182

4 Length of treatment zone ft 380

5 Thickness of treatment zone ft 10

6 Volume of treatment zone ft3 691,600

7 Volume of treatment zone yd3 25,615

8 Unit weight of soil tons/yd3 1.50

9 Weight of soil in treatment zone tons 38,422

10 Weight of soil in treatment zone lb 76,844,444

11 Pounds of NaMnO4 per treatment zone lb 76,844

12 NaMnO4 solution strength % 40%

13 Pounds of 40% NaMnO4 solution needed lb 192,111

14 NaMnO4 density lb/gal 11.40

15 Total volume 40% NaMnO4 solution needed gal. 16,852

16 Water added to make 10% NaMnO4 solution gal. 78,530

17 Total volume 10% NaMnO4 solution to be injected gal. 95,381

18* Number of wells (based on groundwater velocity) ea 37


20 10% solution needed for each well gal. 2,578

Notes: * The number of injection wells is based on a groundwater seepage velocity of 30 ft/yr Assuming an oxidant persistence of 2 years, and a seepage velocity of 30 ft/yr, the downgradient injection lines were spaced 60 ft apart.

APPENDIX A

MATERIAL SAFETY DATA SHEET

LIQUOX® sodium permanganate is a liquid oxidant recommended

for use in Electronics and Fine Chemical Synthesis, that require a

concentrated permanganate solution.

Assay40% minimum as NaMnO

4

pH5.0-8.0

Specific Gravity≥ 1.37

Insolubles≤ 0.005%

Formula NaMnO4

Appearance Deep Purple Solution

Shelf Life This product should be used within one year

of the date of production.

Decomposition may start at 150 °C / 302 °F

• Desmearing/Etchback - Printed circuit board desmearing and etchback.

• Oxidation and Synthesis - Organic chemicals and intermediates manufacture. Oxidizes impurities in organic and inorganic chemicals.

• Concentrated liquid oxidant

• More precise dosing of chemical

• Feed equipment is simplified

• Consistent concentration

• Dust problems are eliminated

• High solubility at room temperature

• Can be used whenever potassium ion cannot be tolerated

PRODUCT SPECIFICATIONS

BENEFITS

SHIPPING CONTAINERS5 gallon (18.9L) Tight Head HDPE Jerrican (UN Specification: 3H1) made of High Density Polyethylene

(HDPE), weighs 3.5 lb (1.6 kg). The net weight is 57 lb (25.7 kg).

The jerrican stands approximately 15.33 in. tall, 10.2 in. wide and

11.4 in. long (38.94 cm tall, 25.91 cm wide, 28.96 cm long).55-gallon (208.2L) HDPE TightHead Drum(UN Specification: UN1H1/Y1.9/150) Made of high-density

polyethylene (HDPE). Weighs 22 lbs (10 kg). The net weight is

550 lbs (249.5 kg). The drum stands approximately 34.5 in. tall, has

an outside diameter of 23.4 in. (89.1 cm tall, OD 59.4 cm).275-gallon (1040-L) IBC (Intermediate Bulk Container)(UN Specification: UN31HA1/Y1.9/100) They are also marked “MX” for multi-trip. IBC weighs 139-lbs (65-kg). The net weight is 3000-lbs (1360-kg). The IBC contains 263-gallons (1000-L) of product. The IBC dimensions are 45.4 in. high, 48 in. long, and 40 in. wide. The IBC has a 2” butterfly valve with NPT threads in bottom sump. (Domestic)

Like any strong oxidant, LIQUOX sodium permanganate should be

handled with care. Protective equipment during handling should

include face shields and/or goggles, rubber or plastic gloves, rubber

or plastic apron. If clothing becomes spotted, wash off

immediately; spontaneous ignition can occur with cloth or paper.

In cases where significant exposure exists, use of the appropriate

NIOSH-MSHA dust or mist respirator or an air supplied respirator

is advised.

The product should be stored in a dry area in closed containers.

Product should be stored above 50°F. Concrete floors are

preferred. Avoid wooden decks. Spillage should be collected and

disposed of properly. Contain and dilute spillage to approximately

6% with water and reduce with sodium thiosulfate, a bisulfite, or

ferrous salt. The bisulfite or ferrous salt may require dilute sulfuric

acid to promote reduction. Neutralize any acid used with sodium

bicarbonate. Deposit sludge in an approved landfill or, where

permitted, drain into sewer with large quantities of water.

As an oxidant, the product itself is non-combustible, but will

accelerate the burning of combustible materials. Therefore,

contact with all combustible materials and/or chemicals must be

avoided. These include, but are not limited to: wood, cloth, organic

chemicals, and charcoal. Avoid contact with acids, peroxides,

sulfites, oxalates, and all other oxidizable inorganic chemicals.

With hydrochloric acid, chlorine is liberated.

HANDLING, STORAGE, AND INCOMPATIBILITYCHEMICAL/PHYSICAL DATA

I N D U S T R I A L®

APPLICATIONS

Copyright 2012rev. 11/13Form LX 1501

The information contained herein is accurate to the best of our knowledge. However, data, safety standards and government regulations are subject to change; and the conditions of handling, use or misuse of the product are beyond our control. Carus Chemical Company makes no warranty, either expressed or implied, including any warranties of merchantability and fitness for a particular purpose. Carus also disclaims all liability for reliance on the completeness or confirming accuracy of any information included herein. Users should satisfy themselves that they are aware of all current data relevant to their particular use(s).

D A T A S H E E T

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LIQUOX® sodium permanganate is compatible with many metals

and synthetic materials. Natural rubbers and fibers are often

incompatible. Solution pH and temperature are also important

factors. The material selected for use with sodium permanganate

must also be compatible with any acid or alkali being used.

In neutral and alkaline solutions, sodium permanganate is not

corrosive to carbon steel and 316 stainless steel. However,

chloride corrosion of metals may be accelerated when an oxidant

such as sodium permanganate is present in solution. Plastics such

as teflon, polypropylene, HDPE and EDPM are also compatible

with sodium permanganate.

Aluminum, zinc, copper, lead, and alloys containing these metals

may be slightly affected by sodium permanganate solutions.

Actual corrosion or compatibility studies should be made under

the conditions in which the permanganate will be used prior to

use.

LIQUOX sodium permanganate is classified as an oxidizer.

Sodium permanganate is shipped domestically as Class 70 and has

a Harmonized Code for export of 2841.69.0010

Proper Shipping Name: Permanganates, Inorganic, Aqueous

solution, n.o.s. (Contains Sodium

Permanganate)

Hazard Class: 5.1

Identification Number: UN 3214

Packaging Group: II

Label Requirements: Oxidizer, 5.1

Special Provisions: T8-Intermodal transportation in

IM 101 portable tanks

Packaging Requirement: 49 CFR Parts 171 to 180 Sections:

173.152, 173.202, 173.242

Quantity Limitations: 1 liter net for passenger aircraft

or railcar. 5 liters net for cargo

aircraft.

Vessel Stowage: D-material must be stowed “ondeck”

on a cargo vessel, but is prohibited on a passenger vessel. Other

provisions, stow “separated from” ammonium compounds,

hydrogen peroxide, peroxides and superperoxides, cyanide

compounds, and powdered metal.

COMPATIBILITY SHIPPING

CARUS VALUE ADDED

LABORATORY SUPPORTCarus Corporation has technical assistance available to answer questions, evaluate treatment alternatives, and perform laboratory

testing. Our laboratory capabilities include: Consulting, Treatability Studies, Feasibility Studies, and Analytical Services.

FIELD SERVICESAs an integral part of our technical support, Carus provides extensive on-site treatment assistance. We offer full application services,

including technical expertise, supervision, testing, and feed equipment design and installation in order to accomplish a successful

evaluation and/or application.

CARUS CORPORATIONDuring its 95-year history, Carus’ ongoing emphasis on research and development, technical support, and customer service has enabled the

company to become the world leader in permanganate, manganese, oxidation, and base-metal catalyst technologies.

Copyright 2012rev. 11/13Form LX 1501

The information contained herein is accurate to the best of our knowledge. However, data, safety standards and government regulations are subject to change; and the conditions of handling, use or misuse of the product are beyond our control. Carus Chemical Company makes no warranty, either expressed or implied, including any warranties of merchantability and fitness for a particular purpose. Carus also disclaims all liability for reliance on the completeness or confirming accuracy of any information included herein. Users should satisfy themselves that they are aware of all current data relevant to their particular use(s).

D A T A S H E E T

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