STATE OF ARKANSAS

DEPARTMENT OF POLLUTION CONTROL AND ECOLOGY

8001 NATIONAL DRIVE, P.O. BOX 8913

LITTLE ROCK, ARKANSAS 72219-8913

RECORD OF DECISION

MONROE AUTO PIT

(Finch Road Landfill)

SEPTEMBER 1996
RECORD OF DECISION

CONCURRENCE DOCUMENTATION

FOR THE

MONROE AUTO PIT SUPERPUND SITE

(FINCH ROAD LANDFILL)

. ^ ^ «r—————————^————————————————————————————^————

Sice Remedial Project Manaefer

_ ^T^y^^^y__

Site Attorney

Wren Stenger, 1-Chief

Arkansas/Oklahoma Section

William Honker, Chief

Arkansas/Oklahoma/Texas Branch

Litigation and Enforcement Branch

^W^. ——y.————y G /^^JL '<"—————

Myron Knudson, Director

Superfund Division
DECLARATION FOR THE RECORD OF DECISION (ROD)

SITE NAME AND LOCATION

Monroe Auto Pit

Raragould, Arkansas

STATEMENT OF BASIS AND PURPOSE

This decision document presents the selected remedial action for the Monroe Auto Pit

Superfund site, in Paragould, Arkansas, which was chosen in accordance with the

Comprehensive Environmental Response, Compensation and Liability Act of 1980, as

amended, (CERCLA),42 U.S.C. §9601 et.seq. and, to the extent practicable, the National

Oil and Hazardous Substances Pollution Contingency Plan (NCP) 40 CFR Part 300. This

decision is based on the Administrative Record for this site.

ASSESSMENT OF THE SITE

Actual or threatened releases of hazardous substances from this site, if not addressed by

implementing the response action selected in this ROD, may present an imminent and

substantial endangerment to public health, welfare, or the environment.

DESCRIPTION OF THE. RKMEDY

This is a ROD for Monroe Auto Pit, which consists of two major elements. The function

of the soil and sludge remedy is to reduce the risks associated with exposure to contaminated

materials and prevent potential ground water and surface water contamination. The second

element of the selected remedy will address the contaminated ground water plume.

The major components of the selected remedy include:

Soil and Sludge

• Capping the sludge disposal area in accordance with RCRA Subtitle C requirements.

• Installing a french drain around the area of sludge deposits. The french drain would

intercept perched ground water before it enters the contaminated area. The captured

ground water would be transported via buried piping to a discharge point located in

the intermittent stream southwest of the site.

• Prohibiting future development of the site.

• Conducting environmental monitoring to ensure eflFectiveness of the remedial action.

ii
• Conducting environmental monitoring to ensure effectiveness of the remedial action.

Ground water

• Reducing contaminant concentrations through naturally attenuating processes such as

biological/chemical/physical degradation, adsorption and dispersion.

• Placing ground water use restrictions on the site property.

• Conducting ground water monitoring of on- and near-site monitoring wells and

residential wells.

• Implementing immediate and secondary contingency actions if necessary to protect

human health and the en ironment.

STATUTORY DETERMINATIONS

The selected remedy for soil/sludge and ground water is protective of human health and the

environment, complies with Federal and State requirements that are legally applicable or

relevant and appropriate to the remedial action, and is cost-effective. The selected remedy

utilizes permanent solutions and alternative treatment to the maximum extent practicable for this

site. However, because treatment of the principal threats at the site was not found to be

practicable, this remedy does not satisfy the statutory preference for treatment as the principal

element.

Because this remedy will result in hazardous substances remaining on-site above health-based

levels, a review will be conducted within five years after commencement of remedial action to

ensure that the remedy continues to provide adequate protection of human health and the

environment.

/r^e^

Regional Administrator

DATE: September 26, 1996

/ */ j ; ,, „ (X^/J^f .

Randall E. Mathis

Arkansas Department of Pollution

Control and Ecology

111
TABLE OF CONTENTS

1.0 SITE NAME, LOCATION AND DESCRIPTION ............... . 1

1.1 NAME AND LOCATION ........................ . 1

1.2 DESCRIPTION .............................. . 1

2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES ............. . 1

2.1 SITE HISTORY .............................. . 1

2.2 ENFORCEMENT ACTIVITIES ..................... . 4

3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION .............. . 4

4.0 SCOPE AND ROLE OF RESPONSE ACTION ................ . 5

5.0 SUMMARY OF SITE CHARACTERIZATION ................. . 6

5.1 LAND USE/POPULATION ....................... . 6

5.2 CLIMATE ................................. . 6

5.3 SURFACE TOPOGRAPHY ........................ . 7

5.4 SURFACE HYDROLOGY ........................ . 7

5.5 GEOLOGY ................................ . 9

5.6 HYDROGEOLOGY ............................ . 9

5.6.1 Perched Ground Water Zones ................... . 9

5.6.2 Upper Wilcox Aquifer ....................... . 13

5.6.3 Lower Wilcox Aquifer ....................... . 17

5.7 NATURE AND EXTENT OF CONTAMINATION IN THE SLUDGE

AND SOIL ............... . .............. . 17

5.8 NATURE AND EXTENT OF CONTAMINATION IN THE GROUND

WATER ................................ . 22

5.9 RESIDENTIAL WATER SUPPLIES ................... . 28

6.0 SUMMARY OF SITE RISKS .......................... . 32

6.1 HUMAN HEALTH RISK ASSESSMENT ................ . 33

6.1.1 Ground water ............................ . 33

6.1.1.1 Current Exposures - Residential Wells Off Site ..... . 34

6.1.1.2 Hypothetical Future Exposures - Monitoring Wells On

Site ............................. . 34

6.1.1.3 Hypothetical Future Exposures - Modeled Ground Water

Concentrations Off Site .................. . 34

6.1.2 Sediment .............................. . 35

6.1.3 Soils/Sludge ............................ . 35

6.1.4 Summary of Human Health Risk ................. . 36

6.2 Ecological Risk Assessment ....................... . 36

iv
7.0 DESCRIPTION OF ALTERNATIVES ...................... . 37

7.1 Soil and Sludge Remedial Alternatives .................. . 37

7.1.1 Alternative No. 1: No Action .................. . 38

7.1.2 Alternative No. 2: Access and Deed Restrictions ........ . 39

7.1.3 Alternative No. 3: Soil and Vegetative Cover; Access ?nd Deed

Restrictions ............................ . 39

7.1.4 Alternative No. 4A: Cap; Slurry Wall; Access and Deed

Restrictions ............................ . 39

7.1.5 Alternative No. 4B: Cap; French Drain; Access and Deed

Restrictions ............................ . 40

7.1.6 Alternative No. 5: Solidification/Stabilization; On-site Landfill;

Access and Deed Restrictions ................... . 41

7.1.7 Alternative No. 6: Excavation; Vapor Extraction;

Solidification/Stabilization on-site Landfill; Access and Deed

Restriction ............................. . 42

7.1.8 Alternative No. 7: Excavation; Off-Site Transport and Disposal

in Subtitle C or D Landfill .................... . 43

7.2 GROUND WATER REMEDIAL ALTERNATIVES ........... . 43

7.2.1 Alternative No. 1: No Action .................. . 43

7.2.2 Alternative No. 2: Natural Attenuation and Degradation; Ground

Water Use Restrictions; Ground Water Monitoring and

Residential Water Supply Monitoring ............... . 45

7.2.3 Alternative No. 3: Ground Water Extraction; Carbon

Adsorption; Reinjection ...................... . 46

7.3 ARARS .................................. . 46

7.3.1 Action-Specific ARARs for Soil/Sludge ............. . 48

7.3.2 Action-Specific ARARs for Ground Water ............ . 49

8.0 COMPARATIVE ANALYSIS OF ALTERNATIVES .............. . 50

8.1 NINE CRITERIA ............................. . 51

8.2 COMPARATIVE ANALYSIS ....................... . 52

8.2.1 Sludge Pit Area .......................... . 52

8.2.2 Ground Water ........................... . 53

9.0 THE SELECTED REMEDY ........................... . 55

9.1 SOIL AND SLUDGE REMEDIATION ................. . 55

9.2 GROUND WATER REMEDIATION ................... . 57

10.0 STATUTORY DETERMINATIONS ....................... . 58

10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT . . 58

10.1.1 Soil and Sludge .......................... . 58

10.1.2 Ground Water ........................... . 58

10.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND

APPROPRIATE REQUIREMENTS ................... . 59
10.2.1 Soil and Sludge .......................... . 59

10.2.2 Ground Water ........................... . 61

10.2.3 Action-Specific ARARs for Ground Water ........... . 61

10.3 COST EFFECTIVENESS ........................ . 62

10.3.1 Soil and Sludge .......................... . 62

10.3.2 Ground Water ........................... . 62

10.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE

TREATMENT TECHNOLOGIES TO THE MAXIMUM EXTENT

PRACTICABLE .............................. . 63

10.4.1 Soil and Sludge .......................... . 63

10.4.2 Ground Water ........................... . 63

10.5 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT . . 63

11.0 DOCUMENTATION OF SIG-JIFICANT CHANGES ............. . 64

12.0 RESPONSIVENESS SUMMARY ........................ . 64

VI
LIST OF FIGURES

Title Page

SITE LOCATION MAP. ........................ . 2

SITE TOPOGRAPHIC MAP. ..................... . 3

SITE SURFACE WATER FEATURES. .............. . 8

LOCATION OF CROSS-SECTION THROUGH THE

SLUDGE DISPOSAL AREA. ..................... . 10

CROSS SECTION THROUGH THE SLUDGE DISPOSAL

AREA. .................................... . 11

REGIONAL GEOLOGIC CROSS SECTION ALONG AND

ADJACENT TO CROWLEY'S RIDGE. ............... . 12

GROUNDWATER POTENTIOMETRIC SURFACE IN THE

PERCHED GROUND WATER ZONE - JUNE 1992. ....... . 14

NORTH-SOUTH HYDROGEOLOGIC CROSS-SECTION

IN THE SITE VICINITY (A-A'). .................... . 15

GROUNDWATER POTENTIOMETRIC SURFACE IN THE

WILCOX AQUIFER UPPER ZONE - MARCH 1993. ...... . 16

GROUNDWATER POTENTIOMETRIC SURFACE IN THE

WILCOX AQUIFER LOWER ZONE - MARCH 1993. ..... . 18

ESTIMATED EXTENT OF SLUDGE DEPOSITS. ...... . 21

ORGANIC CONCENTRATIONS IN GROUNDWATER IN

THE WILCOX AQUIFER. ...................... . 25

INORGANIC CONCENTRATIONS IN GROUNDWATER

IN THE WILCOX AQUIFER. .................... . 29

ORGANIC AND INORGANIC CONCENTRATIONS IN

RESIDENTIAL WELLS. ....................... . 31

vu
LIST OF TABLES

Title Page

MAXIMUM CONCENTRATIONS DETECTED IN

SURFACE SOIL SAMPLES. ..................... . 19

\

MAXIMUM CONCENTRATIONS DETECTED IN

SUBSURFACE SOIL AND SLUDGE SAMPLES. ....... . 20

SURFACE WATER ANALYTICAL DATA. .......... . 23

RANGES OF CONTAMINANTS DETECTED IN UPPER

WILCOX GROUNDWATER MONITORING WELLS. ... . 24

ORGANIC CONSTITUENTS IN THE GROUND WATER OF

THE WILCOX AQUIFER UPPER ZONE OVER TIME .... . 26

WILCOX AQUIFER LOWER ZONE GROUNDWATER ANALYTICAL DATA

SUMMARY. ................ . 30

HEALTH RISKS. ............................. . 36

REMEDIAL ACTION GOALS. ................... . 37

SOIL/SLUDGE ALTERNATIVE COST SUMMARY. ..... . 38

GROUNDWATER ALTERNATIVE COST SUMMARY. ... . 44

VlU
THE DECISION SUMMARY

MONROE AUTO PIT

1.0 SITE NAME, LOCATION AND DESCRIPTION

1.1 NAME AND LOCATION

The Monroe Auto Pit Superfund site, also known as the Monroe Finch Road Landfill, is

located in northeastern Arkansas in unincorporated Greene County, approximately three miles

southwest of Paragould, as shown on Figure 1. The site lies immediately west of Arkansas

Highway 358, approximr/sly three miles west of its intersection with U.S. Highway 49. The

site lies in the Northwest Quarter of the Northeast Quarter of Section 17, Township 16

North, Range 5 East, in the Paragould West P^-minute quadrangle. The southwestern

comer of the site is at latitude 36° 01" 0' and longitude 90° 34" 30'.

1.2 DESCRIPTION

The site is owned by Monroe Auto Equipment Company, One International Drive, Monroe,

Michigan. The property is identified as parcel no. 4071-1 in the Greene County Tax

Assessor's office. The legal description provided in the property deed is "all that part of the

South Half of the Northwest Quarter of the Northeast Quarter of Section 17, Township 16

North, Range 5 East lying West of the Highway No. 358" (Warranty Deed 1973). The site

layout is shown on the topographic map provided as Figure 2. Approximately four acres of

the Monroe property, including the sludge disposal area that covers less than one acre of the

site, is currently surrounded by a six-foot tall chain-link fence topped with barbed wire.

Most of the site is cleared of trees and is covered with native vegetation.

2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES

2.1 SITE HISTORY

In 1973, Monroe purchased a seven-acre tract of land in Greene County, Arkansas. The site

included an inactive sand and gravel borrow pit which was subsequently approved by the

Arkansas Department of Pollution Control and Ecology (ADPC&E) in 1973 for use as a

landfill. Approximately 15,400 cubic yards of alum and lime electroplating sludge/slurry

from the waste water treatment lagoons at Monroe's Paragould manufacturing plant was

deposited in the borrow pit between 1973 and 1978. The sludge contained approximately
Figure 1

2

85% liquid. The present dewatered volume is about 10,800 cubic yards of sludge and

contaminated soil.

Based on boring samples, the sludge extends to an estimated maximum depth of 30 feet.

The greatest contaminant concentrations and the majority of the sludge occur in an

approximate interval of 5 to 25 feet below the surface.

Approximately four acres of the Monroe property, including the sludge disposal area that

covers less than one acre of the site, are currently surrounded by a six-foot tall chain-link

fence topped with barbed wire. The sludge is covered with approximately three to five feet

of soil and the site is vegetated. The site has remained inactive since 1978 and access is

controlled by the fence and a locked gate. The remaining three acres within the fence are,

for the most part, cleared of trees and covered with native vegetation.

Under ADPC&E review, Monroe conducted a series of investigations at the site between

1979 and 1990. These included the installation of ground water monitoring wells, sampling

and analysis of ground water, soil, surface water, and sediment, and geological surveys.

Analysis of the samples collected from monitoring wells at the landfill indicated the presence

of 1,1-dichloroethane [100/zg/L (1989)] and 1,2-dichloroethylene [750/Ag/L (1988)].

Furthermore, a residential well (Gann well) located near the site also showed 1,1-

dichloroethane [10/Ag/L (1987)] and 1,2-dichloroethylene [145^g/L (1987)].

The Environmental Protection Agency (ERA) proposed that the site be added to the National

Priorities List (NPL) in 1989. In August 1990, the site was added to the NPL.

2.2 ENFORCEMENT ACTIVITIES

A Potentially Responsible Party (PRP) search conducted i" 1990 under CERCLA Section

104(e), indicated that Monroe Auto Equipment was the only PRP for this site. On March

14, 1991, EPA issued notice of an impending Remedial Investigation and Feasibility Study

( RI/FS) to the PRP. Monroe Auto Equipment responded to the notice with a good faith

offer to perform the RI/FS. On June 28, 1991, EPA and Monroe Auto Equipment entered

into an Administrative Order on Consent for Monroe to perform a RI/FS.

3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION

A Community Relations Plan for the Monroe Auto Pit site was completed in June 1991. This

Plan lists contacts and interested parties throughout government and the local community. It

also establishes communication pathways to ensure timely dissemination of pertinent

information, and emphasizes the need for community involvement. A public work shop was

4
held on February 24, 1992 to discuss the progress of field work at the site and to inform

the public of the availability of a Technical Assistance Grant (TAG) for the site.

In May 1995 ADPC&E assumed the role of lead agency for the Monroe Auto Pit site. The

Proposed Plan was released to the public by ADPC&E on July 17, 1995. All of the site

related documents are available at the Northeast Arkansas Regional Library, located at 120

North 12th Street, Paragould, Arkansas. A public comment period on the Proposed Plan was

held from July 17 to August 17, 1995 with an extension granted until October 16, 1995. In

addition, a public meeting was held on August 8, 1995 to present the results of the Remedial

Investigation/Feasibility Study and the Proposed Plan. Another open house was held

September 12, 1995 to answer any new questions and to explain the details of the plan. All

comments received by ADPC&E prior to the end of the comment period, including those

expressed verbally at the public meeting, are addressed in the Responsiveness Summary

section of this Record of Decision.

4.0 SCOPE AND ROLE OF RESPONSE ACTION

This ROD addresses the entire site as one operable unit. The remedial objective that is

addressed in this ROD is the reduction or elimination of the actual and/or potential risk

associated with the sludge pit and the contaminants in the ground water.

The objectives of this remedy are three fold, to prevent contact with the buried sludge and

contaminated soil, to prevent infiltration of precipitation or ground water in the sludge deposit

area, and to prevent the contamination of the residential well water supply.

The buried sludge was originally 15,400 cubic yards of alum and lime sludge from the waste

water treatment lagoons. Processes related to shock absorber production contributed to the

waste water. The sludge was approximately 85% water. The present dewatered volume is

about 10,800 cubic yards of sludge and contaminated soil. Dermal contact with, or ingestion

of the sludge and contaminated soil must be prevented because contact with the sludge poses

a carcinogenic and non-carcinogenic risk level above that recommended by EPA.

The sludge was periodically covered with soil which absorbed some of the water, but was

not an effective barrier to precipitation. Infiltration of precipitation and perched ground water

through the sludge adds to the contaminant levels produced by the initial dewatering of the

sludge. Future infiltration into the sludge area should be prevented, thus cutting off the

source of ground water contamination.

The exact production zones of all of the private wells are not known, but most are assumed

to produce from the lower Wilcox aquifer. Because this is only an assumption, the potential
ingestion or dermal contact of contaminated ground water from the upper Wilcox aquifer

from a residential well or from a well placed on the site in the future must be prevented.

Monitoring of the on and near site monitoring wells (88 samples) shows a decrease in the

contaminant levels away from the sludge area. Levels of volatile organic compounds have

decreased over time (first monitoring 1988) and this trend should continue. Recent (1995)

residential well water samples do not show contamination by volatile organics above

analytical detection levels. Although modeling of contaminant movement has been done,

monitoring should be continued.

The remedies evaluated in this ROD are measured against these objectives. Those remedies

meeting these objectives are evaluated further to determine the best remedy for this site. The

ultimate objective is the protection of human health and the environment.

5.0 SUMMARY OF SITE CHARACTERIZATION

5.1 LAND USE/POPULATION

The most predominant land use near the site is single-family residences. Based on a field

survey conducted in 1992, there are 52 single-family residences and six mobile homes within

a one-mile radius of the site. Many of these are associated with small farms and related

agricultural pursuits. Agricultural uses include crop farming and livestock production. The

field survey identified four commercial land uses. These land uses were individual enterprises

and included antique sales, convenience stores, and automobile repair establishments.

Industrial land uses are limited to gravel quarries and an overhead electrical power line.

There are no schools, nursing homes, churches, hospitals, or recreational facilities within a

one-mile radius of the site.

In 1992, the estimated population within a one-mile radius of the Finch Road Landfill site

was 159 persons, residing in 58 households. Assuming the rate of population increase (from

1984, till 1992) remains constant there will be an estimated total of 69 residences and 190

persons within a one-mile radius of the site by the year 2000.

5.2 CLIMATE

Greene County has hot summers, mild winters, high humidity and abundant rainfall. The

mean annual temperature is 60 °F with temperatures infrequently exceeding 100°F in the

summer or railing below 10 °F in the winter . Precipitation averages 49 inches per year with

a fairly even distribution throughout the year. In a typical year, April is the wettest month

and October is the driest. Only minor amounts of snowfall contribute to the yearly

precipitation. In the average year, thunderstorms occur on 55 days; however, damaging

winds seldom accompany these storms. The most intense storm each year averages 1.4

inches of rain in an hour; the average yearly 24 hour maximum rainfall is between 3.0 and

6
3.5 inches. Approximately 110 days in the year will have a total precipitation greater than

0.01 inches. The mean annual wind speed averaged through the afternoon mixing layer is

approximately 6 miles per hour.

5.3 SURFACE TOPOGRAPHY

The land surface near the site is very irregular. The site topographic map, Figure 2, shows

that the ground surface slopes downward from Highway 358 on the eastern site boundary,

and that the land is relatively flat over the sludge disposal area. Two ravines, sloping

southwesterly, lie west of the sludge disposal area and within ihe fenced area. An

intermittent spring is present in each of the ravines. A shallow seasonal pond is also present

within the fenced area, and is found northwest of the sludge disposal area. Site elevations

range from approximately 413 to 460 feet above mean sea level (MSL).

5.4 SURFACE HYDROLOGY

Surface water is intermittently present at three locations on the site (Figure 3). A depression

on the western edge of the site, approximately 25 feet in diameter, forms a pond from storm

water runoff during periods of heavy rainfall. The depression dries during periods of low

rainfall.

Two intermittent springs in the southwestern comer of the site discharge to a small stream.

The springs may be discharge points for the perched ground water zone. Flow rates from

the springs have been observed to be greatest immediately following prolonged periods of

heavy precipitation, and quickly decrease after precipitation ends.

Precipitation that does not run off either infiltrates, evaporates, or is absorbed by the

vegetation on the site. Surface water at the site can easily infiltrate the sandy loess and

gravel deposits and migrate to the perched water zones. In a few areas of the site, clay near

the surface prevents rapid infiltration and puddles can stand for several days in these perched

zones. In summer months, evaporation can reach a third of an inch per day.

Surface water runoff leaves the site through two ravines, as shown on Figure 3. Surface

water in the ravines enters an intermittent creek that joins Village Creek nearly a mile

southwest of the site. The water of Village Creek enters the St. Francis river at it's

confluence with Straight Slough, over 25 miles southeast of where surface water runoff from

the site would enter Village Creek. Secondary contact recreation, and domestic, industrial,

and agricultural water supplies are uses of waters near the site.

Due to the intermittent nature of the pond and springs, the surface water exposure pathway

is incomplete. The only exposure possible would be by persons coming into contact with

surface water on site.

7
Figures
5.5 GEOLOGY

Pliocene sand and gravel (Crowley's Ridge deposits) from braided and meandering stream

environments overlie Eocene clay, silt, sand and lignite deposits. In the site area, the

Crowley's Ridge deposits unconformably overlie the Eocene Wilcox Group. The Jackson and

Claibome Groups have been eroded away on the northern sections of the Ridge. Figure 4

shows a regional cross-section of this area.

At the site, the Crowley's Ridge deposits characteristically contain cobbles up to two inches

in diameter, mixed with sand, clayey sand, and silty sand. The deposits are up to 70 feet

in thickness east of the site, where the deposits have not been excavated. These deposits are

10 to 15 feet thick on the site where sand and gravel excavation occurred during quarry

operations. In some gravel pits surrounding the site, these sands and gravels were excavated

to the top of the Wilcox Group. A cross section through the sludge disposal area (Figure

5) at the location shown on Figure 6, shows the extent of sludge deposits and cover material

in relation to the site lithology.

At the site, individual thicknesses of sand and clay layers in the Wilcox Group vary from

less than one inch to several feet. However, a consistent, very stiff clay layer in the Wilcox

Group correlates between boreholes across the site. The clay layer has an estimated

thickness of 40 to almost 70 feet. Several lignite deposits were also encountered in this clay,

which is typical of the Wilcox in this area. Fine to medium-grained sands underlie the thick

clay at all monitoring well locations. Other cross-sections are included in the RI report.

5.6 HYDROGEOLOGY

Two primary ground water zones have been identified at the site: The upper zone of the

Wilcox aquifer and the lower zone of the Wilcox aquifer. Perched ground water has also

been identified in some locations near the sludge disposal area. The following subsections

discuss the occurrence and hydraulic characteristics of these three zones.

5.6.1 Perched Ground Water Zones

Perched ground water intermittently occurs across the site. Thin layers of stiff clay, up to

several inches in thickness, were observed at depths between five feet and 50 feet. After

periods of precipitation, the soil above these clay layers has been found to be saturated,

creating localized zones of perched ground water. During these high water periods (water

levels can change by as much as 10 feet), water discharges from the springs. Five monitoring

wells arc installed in the perched ground water zone at the site. Water level measurements

were taken monthly for one year to document the seasonal fluctuations. These measurements

indicate that perched ground water is seasonal and intermittent. The presence and amount

of perched ground water arc dependent upon precipitation.

Subsurface field investigations have shown that one localized perched ground water zone may
REGIONAL GEOLOGIC CROSS SECTION

ALONG AND ADJACENT TO CROWLEY'S RIDGE

APPROXIMATE LOCATION OF THE MONROE AUTO PTT SUPERFUND SfTE
Figures

11
Figur

e 6

12
be continuous beneath the area of sludge/soil contamination. The elevation of the perched

ground water surface has been recorded at approximately 416 to 427 feet above MSL (13

to 26 feet below land surface [bis]) when present in the monitoring wells. The perched

ground water gradient slopes in the general direction of the ravines south-southwest of the

sludge disposal area.

The perched ground water flow pattern, assuming that the perched zone is continuous across

the site, is shown on Figure 7. It is believed that this water may discharge through the

springs in the two ravines. Perched ground water is also likely to percolate into the

underlying Wilcox aquifer through discontinuities in the underlying low-permeability zone.

A deeper perched zone has been identified on the northern portion of the site. The ground

water surface elevation in this zone was measured at approximately 381 feet above MSL

(approximately 70 feet bis) in February 1992. This perched zone is likely formed from a

clay lens that was encountered at a depth of approximately 80 feet bis. Multiple perched

water zones are typical of alluvial formations such as the Wilcox Group and in areas where

local infiltration is the major form of recharge for the aquifer.

5.6.2 Upper Wilcox Aquifer

Two ground water zones were encountered in the Wilcox aquifer through the total depth of

the subsurface investigation (Figure 8). The upper zone behaves as an unconfined aquifer

composed of interbedded sand and clay. Five monitoring well clusters and six single wells

monitor the upper Wilcox aquifer. These wells are designated as ESW ft -1 (lower part of

the upper aquifer) and ESW if -3 or A (upper part of the upper aquifer). Exceptions to

these labels are ESW 1A- intermediate perched zone, ESW 8 and 9- lower part of the upper

aquifer, and ESW 6- the lower Wilcox aquifer. Approximately 10 to 70 feet of Crowley's

Ridge deposits overlie the Wilcox aquifer upper zone in the site area. A clay layer greater

than 40 feet in thickness forms the base of the Wilcox aquifer upper zone. At the southern

boundary of the site, the surface of the clay layer was encountered at approximately 266 feet

above MSL (174 feet bis).

The ground water flow pattern in the upper zone of the Wilcox aquifer is shown on Figure

9. The flow pattern is seen to radiate from the western portion of the site toward the

northeast and southeast quadrants. Water levels fluctuate by a few inches up to one foot

seasonally. The hydraulic gradient in the SE direction (Mar '93) is 0.005 ft/foot and in the

NE direction, 0.006 ft/foot. The saturated thickness of the upper Wilcox aquifer is

approximately 50 feet. A downward gradient may exist in the upper zone of the Wilcox

aquifer. This vertical gradient is due in part to the low hydraulic conductivity of the clay

and recharge from the overlying Crowley's Ridge deposits to the upper zone of the Wilcox

aquifer. The hydraulic conductivity in the vicinity of ESW-13-1 is approximately 420 gallons

per day per square foot (gpd/ft2) or 2.0 x 102 centimeters per second (cm/s). The aquifer

is composed of silty sand, with lenses of sandy, silty clay.

13
14
15
Figur

e 9

16
5.6.3 Lower Wilcox Aquifer

A confined ground water aquifer, the Wilcox aquifer lower zone, has been identified below

the Wilcox aquifer upper zone. The lower zone of the Wilcox aquifer is separated from the

upper zone by a clay confining layer more than 40 feet thick. Hydraulic conductivity tests

performed on samples of this clay yielded vertical hydraulic conductivity values on the order

of 10'9 cm/sec.

Five monitoring wells monitor the lower Wilcox aquifer. These wells are designated by

ESW ff -2, except for well ESW- 6. The lower Wilcox aquifer is composed of fine to

medium-grained sand and fine gravel, which coarsens with depth. At the southern site

boundary, this zone is approximately 36 feet thick, extending from 226 feet above MSL to

190 feet above MSL.

The ground water flow pattern in the lower aquifer is shown on Figure 10. The ground

water flow is primarily t: the east and southeast from the site, and the gradient appears to

be relatively smooth across the monitored area. Based on aquifer pump tests (May '92) the

hydraulic gradient near ESW 13-2 averages 0.002 ft/foot. The hydraulic gradient was

calculated at 56 ft/day (2.0 X 10-2 cm/sec).

5.7 NATURE AND EXTENT OF CONTAMINATION IN THE SLUDGE AND

SOIL

Twenty one soil borings were placed over the sludge disposal area. Samples of surface soil,

shallow subsurface soil near the inferred interface between the soil/sludge and the overlying

fill material, and samples of deep subsurface sludge and soil were analyzed for volatile

organic compounds (VOCs), semivolatile organics, and inorganics.

Three VOCs, eight semivolatile organics, and four inorganics were detected in surface soil

samples (less than 2.5 feet below the surface) at concentrations greater than twice their

background concentrations. Maximum concentrations detected in the surface soil are shown

on Table 1.

Thirteen VOCs, seven semivolatile organics, and eighteen inoiganics were detected in shallow

subsurface soil (a depth of 2.5-7.5 feet) at concentrations greater than twice their background

levels.

Fifteen VOCs, eight semivolatile organic compounds, and eighteen inorganics were detected

in deep subsurface soil/sludge samples (greater than 7.5 feet deep) at concentrations greater

than twice their background concentrations. Maximum concentrations detected in the

subsurface soil/sludge samples are shown on Table 2.

Analyte concentrations are randomly distributed across the site, and the detected

concentrations do not show the existence of any spatial pattern. The estimated horizontal

extent of sludge deposits is shown on Figure 11. The horizontal extent covers approximately

17
18
TABLE 1

MAXIMUM CONCENTRATIONS DETECTED IN

SURFACE SOIL SAMPLESi

Monroe Auto Pit Superfund Site

(Finch Road Landfill)

Parameter Maximum Concentration

VOCs

TCE

Ethylbenzene

Total Xylenes

14 J ug/Kg

1.0 Jug/Kg

7.0 J ug/Kg

Semivolatile Organics

2-Chlorophenol

1,2,4-Trichlorobenzene

Naphthalene

4-Chloro-3-methylphenol

2,4-Dinitrophenol

Fluoranthene

Pyrene

di-n-Octylphthalate

Inorganics

Chromium

Lead

Manganese

12 J ug/Kg

10 J ug/Kg

14 J ug/Kg

14 J ug/Kg

27 J ug/Kg

5.0 Jug/Kg

5.0 Jug/Kg

10 J ug/Kg

60.6 J mg/Kg

586 J mg/Kg

1440 J mg/Kg

J - Estimated Value

1-0-2.5 feet below surface

Samples taken 1992-1993

Complete data tables that include quantitation limits for all analytes are provided in Appendix H of the Remedial

Investigation (RI)

19
TABLE 2

MAXIMUM CONCENTRATIONS DETECTED IN

SUBSURFACE SOIL AND SLUDGE SAMPLESi

Monroe Auto Pit Su^rfund Site

(Finch Road Landfill)

Parameter Maximum Concentration

VOLATILE ORGANICS

Vinyl Chloride

1.1-Dichloroethane

1.2-Dichloroethylene

1,1,1 -Trichloroethane

Trichloroethyle" e

Benzene

Tetrachloroethylene

Toluene

Ethylbenzene

Total Xylenes

SEMIVOLATILE ORGANICS

bis(2-Ethylhexyl)phthalate

Naphthalene

di-n-Octylphthalate

Phenol

Phenanthrene

INORGANICS

Antimony

Arsenic

Beryllium

Cadmium

Chromium

Lead

Manganese

Mercury

Nickel

Zinc

Cyanide

31,OOOJug/Kg

66,000 ug/Kg

60.000J ug/Kg

210J ug/Kg

91J ug/Kg

15J ug/Kg

310J ug/Kg

16.000J ug/Kg

220J ug/Kg

6,700 ug/Kg

96,OOOJ ug/Kg

6400J ug/Kg

550J ug/Kg

16.000J ug/Kg

42,OOOJ ug/Kg

63.1 mg/Kg

19.6J mg/Kg

0.88J mg/Kg

1.2 mg/Kg

4.030J mg/Kg

3.240J mg/Kg

319J mg/Kg

0.12J mg/Kg

23.8J mg/Kg

508 mg/Kg

15.7 mg/Kg

Complete data tables that include quantitation limits for all analytes are provided in Appendix H of the Remedial

Investigation (RI)

20
Figure 1

1

21
30,000 square feet, or approximately 0.7 acres. The sludge extends to an estimated

maximum depth of 30 feet, although the greatest contaminant concentrations, and the majority

of the sludge deposits, were identified through an approximate interval of 5 to 25 feet. The

depth of the sludge deposits' bottom surface is erratic. Both the total depth and thickness

vary greatly between boring locations. The total volume of sludge and contaminated soil is

estimated to be approximately 10,800 cubic yards. Variations in the total sludge depth and

thickness are to be expected because the sludge was deposited in an abandoned quarry. An

examination of other quarries in the area shows that great variations in excavation depths are

common, as excavation appears to cease upon encountering clay lenses in the Wilcox

deposits.

5.8 NATURE AND EXTENT OF CONTAMINATION IN THE GROUND WATER

Contaminants in the ground water move with the water. In the perched zone, this would be

out through the springs or downward into the upper Wilcox aquifer. In the upper Wilcox

aquifer, the contaminants move in a northeasterly and a southeasterly direction. The metals

have a greater affinity for the fine grained sediments and will move slower than the organics,

but in the same direction.

A volume of perched water sufficient for sampling was present at only one monitoring well

location (ESW-2P, 1992). No VOCs or semivolatile organics were detected in a ground

water sample collected from this well. Inorganic concentrations were generally less than

those in samples from the Wilcox aquifer. Eight inorganics were detected in unfiltered

samples and six in filtered samples. It must be noted, however, that this monitoring well

is located on a side-gradient from the sludge disposal area, if a continuous perched zone is

assumed to exist across the site.

Some of the perched water appears to discharge through the springs following a significant

rain event. Surface water representative of the springs in the ravines southwest of the sludge

disposal area was also sampled. Four volatiles organics, three semivolatile organics and nine

inorganics were detected (Table 3). Sediment samples from the creek showed a marked

decrease in contamination away from the site. The perched water is seasonal and its flow

has a limited extent.

The maximum concentrations of contaminants detected in the Wilcox aquifer upper zone in

1992 and 1993 arc listed in Table 4. The presence of 1,1-DCA and 1,2-DCE arc taken as

indicators of ground water contamination because these two compounds arc consistently

detected across the site in the upper Wilcox aquifer. The detected concentrations decrease

away from the sludge disposal area (Figure 12). A comparison of April 1992 data to

previous data (1988-1990, 66 samples total) show a general decrease in volatile organic

concentrations (Table 5). Data from wells installed in 1992 is insufficient to establish a

trend.

Samples containing elevated VOC and semivolatile organic concentrations, as compared to

22
TABLES

SURFACE WATER ANALYTICAL DATA

Monroe Auto Pit Superfund Site

(Finch Road Landfill)

Sample ID________________SW1-1 SW2-1 SW3-1 SW4-1

Pond Ravine Ravine Ravine

Volatile Organic Compounds (ug/L)

Dilution Factor 1.0 1.0 1.0 1.0

Carbon Disulfide

1,1 -Dichloroethane

2-Butanone

Trichloroethylene

l.OU l.OU 0.3J 0.03J

l.OU l.OU l.OU 1.3

10U 10U 10J 10U

l.OU 0.2J l.OU l.OU

Semivolatile Organic Compounds (ug/L)

Dilution Factor 1.0 1.0 1.0 1.0

Diethylphthalate 10UJ 0.1J 0.1J 0.2J

di-n-butylphthalate 0.1J 0.1J 0.1J 0.3J

bis(2-Ethylhexyl)phthalate 10U 10U 10U 15J

Inorganics (ug/L)

Arsenic

Barium

Chromium

Manganese

6.6J 2.0UJ 2.0UJ 2.0U

49.6UJ 60.4J 71. U 120J

16.7: 10.0U 10.CU 10.0U

98.6UJ 18.5 24.9 353

NOTES:

U - Undetected; quantity shown is the detection limit.

J - Estimated quantity.

UJ - Undetected; quantity shown is estimated detection limit.

na - Not analyzed.

Only the analytes detected in deep surface water samples are shown.

Complete data tables that include quantitation limits for all analytes are provided in appendix H of the

Remedial Investigation (RI)

Data 1992-1993

23
TABLE 4

RANGES OF CONTAMINANTS DETECTED IN

UPPER WILCOX GROUNDWATER MONITORING WELLS

Constituent MaximumConcentration

Volatile Organic Compounds (ug/L)

Chlorethane

1,1-Dichloroethene

1.1-Dichloroethane

1.2-Dichloroethene (total; cis & trans)

1,2-Dichloroethane

Chlorofonn

2-Butanonc

1,1.1-Trichloroethane

cis-1,3-Dichloropropcnc

Carbon Tetrachloridc

Trichloroethylene

Semivolatile Compounds (ug/L)

Nitrobeazene

Isophorone

Benzyl alcohol

Benzoic acid

4-Chloro-3-methylphenol

Diethylphthalate

Dimethylphthalate

Di-n-butylphthalate

bis(2-Ethylhexyl)phthalate

Total (Unfutered) Inorganics (ug/L)

Arsenic

Barium

Beryllium

Chromium

Lead

Manganese

Mercury

Zinc

Dissolved (Filtered) Inorganics (ug/L)

Arsenic

Barium

Chromium

Manganese

Zinc

l.OJ

4.0

42

\SO

2.0 J

0.5 N

32 NJ

2.0

3.0

0.3 J

J.4 J

78

0.2 J

0.8 J

5.0 J

0.4 J

0.5 J

0.1 J

0.4 J

44J

122

1.290

12.0

1,090

235

2,450

0.4

4,220

5.7

51.3

14.4

69.3

221

Notes:

J - Estimated quantity. N - Presumptive evidence; presence of compound not confirmed.

NJ - Presumptive evidence; presence of compound not confirmed. Quantity is estimated

Only the analytes detected in Wilcox groundwater samples are shown.

Complete data tables that include quantitation limits for all analytes are aprovided in Appendix H

Danata 1992 - 1993

24
Figure 12
TABLES

Organic Constituents In the Ground Water of the Wilcox Aquifer Upper Zone Over Time

Monroe Auto Pit Superfund Site

Paramet

1,1-Did

Mar-88

Dec-88

Nov-89

Feb-90

Apr-92

Apr-93

Aug-93

1,2-Dichloroethylene (^g/1)

Mar-88

Dec-88

Nov-89

Feb-90

Apr-92

Apr-93

Aug-93

er

ilorocthane (^g/1)

(cis-)

(cis-)

(cis- & trans-)

(cis- & trans-)

(cis- & trans-)

(cis- & trans-)

(cis- & trans-)

ESW-2A

97

77

100

93

42

na

41

750

490

(5.0

<5.0

180

na

170

ESW-3A

6.0

8.2

10

6.7

7.0 N

na

6.0

7.8

11

<5.0

17

23

na

18

ESW-4A

17

21

23

140

4.0 N

na

11.0

110

120

(5.0

(5.0

26

na

39

ESW-8

ni

ni

(5.0

<5.0

(1.0

na

(1.0

ni

ni

(5.0

<5.0

(1.0

na

0.2 J

ESW-9

ni

ni

(5.0

(5.0

<1.0

na

(1.0

ni

ni

(5.0

(5.0

(1.0

na

(2.0

ESW-10-1

ni

ni

(5.0

(5.0

(1.0

na

(1.0

ni

ni

<5.0

(5.0

(1.0

na

(1.0

ESW-11-1

ni

ni

ni

ni

1.0 N

na

0.4 J

ni

ni

ni

ni

6.0

na

1.8

ESW-H-3

ni

ni

ni

ni

(1.0

na

(1.0

ni

ni

ni

ni

<1.0

na

(1.0

ni - Well not installed na - Not analyzed J - Estimated value N - Presumptive evidence R - Rejected data

26
TABLES

Organic Constituents in the Ground Water of the Wilcox Aquifer Upper Zone Over Time

Monroe Auto Pit Superfund Site

continued

1-Dich

ar-88

ec-88

ov-89

sb-90

pr-92

pr-93

2-Dichloroethylene (^g/1)

[ar-88

ec-88

ov-89

eb-90

pr-92

pr-93

er

iloroethane (/^g/1)

(cis-)

(cis-)

(cis- & trans-)

(cis- & trans-)

(cis- & trans-)

(cis- & trans-)

ESW-12-

ni

m

ni

ni

2.0

na

1.4

m

ni

ni

m

5.0

na

5.6

1 ESW-12-2

ni

ni

ni

ni

4.0

na

2.0

ni

ni

ni

ni

10.0

na

5.5

ESW-13-1

ni

ni

ni

ni

(1.0

na

(1.0

ni

ni

ni

ni

(1.0

na

(1.0

ESW-13-3

m

ni

ni

ni

(1.0

na

(1.0

ni

ni

ni

ni

(1.0

na

(1.0

$ ESW-14-1

ni

ni

ni

ni

ni

25 J

7.0

ni

ni

ni

ni

ni

<1.0

49.0

ESW-14-3

ni

ni

ni

ni

ni

50

3.0

r'

ni

ni

ni

ni

29.0 J

16.0

ESW-15-1

ni

ni

ni

ni

ni

<1.0

(1.0

ni

ni

ni

ni

ni

(1.0

<i.o

ESW-15-3

ni

ni

ni

ni

ni

(1.0

(1.0

ni

ni

ni

ni

ni

(1.0

(1.0

ESW-16

ni

ni

ni

ni

ni

12.0

13.0

ni

ni

ni

ni

ni

59.0 J

94.0

ni - Well not installed

na - Not analyzed J - Estimated value N - Presumptive evidence R - Rejected data

27
background concentrations, did not contain corresponding elevated concentrations of

inorganics. The inorganic concentrations detected in ground water samples (1992-93) showed

no pattern across the site, and did not always decrease in a down gradient direction (Figure

13). However, greater inorganic concentrations did correspond to higher levels of total

dissolved solids measured in the samples. This fact, along with the much lower inorganic

concentrations in filtered samples as compared to unfiltered samples, indicates that a large

proportion of the total inorganic mass in the ground water samples is due to soil particles

in the samples. The lack of a spatial pattern is probably due to natural variability of the

Wilcox aquifer. Contamination appears to be confined to the upper Wilcox aquifer. The

best water production and the depths of the private wells indicate that most of the wells draw

water from the lower Wilcox aquifer. The upper Wilcox aquifer is considered the most

likely exposure route, but private wells are not believed to produce from this zone. This

is the only potential exposure pathway.

Ground water samples fnm the Wilcox aquifer lower zone were not found to contain

detectable concentrations of VOCs or inorganics. Only one sample contained detectable

concentrations of semivolatile organics (Table 6). The lower Wilcox aquifer is separated

from the upper Wilcox aquifer by approximately 40 feet of low permeability clay. The lower

Wilcox aquifer is not contaminated and this exposure pathway is not considered further.

5.9 RESIDENTIAL WATER SUPPLIES

Residential water supplies are obtained from the Wilcox aquifer. The production zones are

uncertain because few drilling logs or well construction records were found, and well

owners had little or no knowledge of the well depths. It is likely that most wells are

completed in the lower zone because monitoring wells at the site show that this zone provides

greater well yields than the upper zone. Well records that could be found indicated that

production from 40 to 100 feet bis. in wells south of the site and 150 to 210 feet bis. in

wells north of the site. Given the topography and the high yields of the wells south of the

site, all of these wells could potentially be in the same aquifer, the lower Wilcox aquifer.

Four VOCs, three semivolatile organic compounds (SVOCs), and seven inorganics were

detected in residential water supply samples in 1992. The VOC and SVOC levels are

estimated as indicated by the J qualifiers. Concentrations of these contaminants are below

the Safe Drinking Water Act Maximum Contaminant Levels (MCLs). Concentrations of

organics and inorganics in residential water supply samples (1992) are shown on Figure 14.

The wide dispersal pattern (up and down gradient of the site) and the lack of organic

contamination concurrent with the metals indicates that the contamination is not site related.

Residential well sampling since the RI indicate that organics are below the detection limit if

they are present and inorganic concentrations, when detected, remain at about the same level.

A comparison of the April 1992 data with previous (1989) data collected prior to the

CERCLA activities indicates that the concentrations of VOCs and semivolatile organics have

generally remained stable over the monitoring period. The majority of the wells show

concentrations of

28
-N100 (eel

SCALE

INORGANIC CONCENTRATIONS IN GROUNDWATER IN THE WILCOX AQUIFER

MONROE AUTO PIT SUPERFUND SITE (FINCH ROAD LANDFILL)

ES ENGINEERING-SCIENCE

LEGEND

ESW-8 ^ Monitoring Well Location and Number

Notes:

1. All concentrations are provided In ug/L (ppb).

2. When a duplicate sample was collected, the greatest value Is shown.

3. J-estimated value.

4. nd-not detected.

5. Samples from monitoring wells with prefixes ESW-14, ESW-15. and ESW-16 were

collected In 1993. All other samples were collected In 1992.
TABLE 6

WILCOX AQUIFER LOWER ZONE

GROUNDWATER ANALYTICAL DATA SUMMARY

Monroe Auto Pit Superfund Site

(Finch Road Landfill)

Sample ID_________ESW-6 ESW-10-2 ESW-11-2 ESW-12-2

Volatile Organic Compounds (ug/L)

No VOCs Detected

Semivolatile Organic Compounds (ug/L)

Phenol 29 10UJ 10U 10U

2-Methylphenol 17 10UJ 10U 10U

4-Methylphenol 36 10UJ 10U 10U

2,4-Dimethylphenol 5.0J 10UJ 10U 10U

Di-n-butylphthalate 0.2J 10UJ 10U 10U

Total (Unfiltered) Inorganics (ug/L)

No Inorganics Detected

Dissolved (Filtered) Inorganics (ug/L)

No Inorganics Detected

NOTES:

U - Undetected; quantity shown is the detection limit.

J - Estimated quantity.

UJ - Undetected; quantity shown is estimated detection limit.

Only the analytes detected in deep surface water samples are shown

Complete data tables that include quantitation limits for all analytes are provided in appendix H of the

Remedial Investigation (RI)

Data 1992 - 1993

30
ORGANIC AND INORGANIC CONCENTRATIONS

IN RESIDENTIAL WELLS

MONROE AUTO PIT SUPERfUND SITE '

(FWCH ROAD LANDFILL)

PW-S5

•-. . 1.::::::.•:

TCE

bis(2-Ethylhcxyl)phthal»le

PW-S16~>| W

O.IJ,

l.OJ,

/^

N1 -(

N2 -1

N3 -

N4 -

N5 -

N6 -

N7 -

m •

N9 -

N10-

N11 • N12

N13

N14

Figure 14

Ml——

3'Ncil

Faulkner

Halcomb

Thompson. J

Duncan

Chafftn

Merfdiih

Henry

• McAliSter

MeCullT

• Springsion

•Gunn

-Fahr

• She] ion

WWW*

N15 •lohnson.G

Nl6-H*mp»n

N17-L*dcey

Nll-Johnson.M

Sl •Clcvcl*n<i

-S2 -Kennedy

S3 - Templcton

S4 -Hale

S5 .Tolcr

S6 -Bcrodt

S7 -

S8 -

S9 •

SIOSllS12-

S13.

S14.

S15 •Thompson, A

S16

Robinson

Hodse

Dowlcr

Wonh»m

KJOSP

El«m

Not Assigned

• Andcraon, D

• Hill, W

LEGEND

NOTES:

i 1992 samples

All units in u-f/L (ppb)

J Estimated quantity

31

Q

Paved Highway

Gravel Road

or Drive

Monroe Auto

Property

Fence

PW-S1

Residence and

Private-well

Location

Stream

Lake
volatile organics below the detection limits or not detected at all. The concentrations exhibit

variations that can be considered normal under the sampling and analytical protocols that

were used. Variations in the inorganic concentrations and their distribution can be attributed

to natural variation within the Wilcox aquifer. No increasing or decreasing trends are

observed in the data over time (1989-1995). Residential wells within one-half mile of the site

are sampled semi-annually at this time. They will continue to be monitored, but the

frequency may change in the future. Because the volatile organic compounds move faster

than the metals and because they move with the ground water flow, one would expect to see

the VOCs arrive at the wells ahead of the metals. Because this relationship is not seen, the

contaminants are probably not site related.

6.0 SUMMARY OF SITE RISKS

An evaluation of the potential risks to human health and the environment from site

contaminants was conducted in accordance with OSWER Directive 9285, Risk Assessment

Guidance for Superfund, Volume 1, Human Health Evaluation Manual (Part A), as part of

the baseline risk assessment. The results of all the sampling conducted at the site during the

RI were used to evaluate the risk that the site poses to human health and the environment.

The objectives of the baseline risk assessment were to (1) help determine whether additional

response actions are necessary at the site; (2) provide a basis for determining remedial

action goals that are adequately protective of human health and the environment; and (3)

provide a basis for comparing potential health impacts of various remedial alternatives.

The baseline risk assessment was divided into two parts: 1) the human health evaluation and

2) the ecological evaluation. Human health risks are determined by evaluating chemical

exposure limits and actual concentrations of contaminants present at a site. The contaminant

concentrations are compared to the exposure concentration known or suspected to have a

potential adverse impact. In the risk assessment, carcinogenic and non-carcinogenic risks arc

calculated. Conservative assumptions that weigh in favor of protecting human health are used

in calculating risks. The environmental or ecological risk assessment is conducted to

determine if there are any current or potential impacts on ecological receptors (such as birds

or mammals) attributable to the unremediated site.

The national risk, or probability, that an individual may develop some form of cancer from

everyday sources, over a 70-year life span, is estimated at three in ten. Activities such as

too much exposure to sun, occupational exposures, or dietary or smoking habits contribute

to this high risk. The three in ten probability is considered the "natural incidence" of cancer

in the United States.

32
To protect human health, a risk range of one in ten thousand to one in one million excess

cancer risk has been set as a goal for Superfund sites. This range may be expressed as 10^

to 10'6. For example, a risk of 10'6 means that 1 person out of one million could develop

cancer as a result of a lifetime exposure to a site. The level of concern for non-carcinogenic

contaminants is determined by calculating a Hazard Index (HI). There may be concern for

potential exposure to a site where the HI values are greater than 1.0 for human populations

who may reasonably be expected to be exposed.

The baseline risk assessment assumes a no-action alternative at the site. Baseline exposure

estimates were based on future unrestricted access. Four acres of the site, including the pit

and seasonal pond, are currently surrounded by a locked chain-link fence. However, it was

assumed that the site is currently accessible to trespassers. Also, off-site residential well

water was evaluated for risks associated with current domestic use.

The future land use is a^umea to be residential. Estimates were based on the assumption

that development of the Monroe site would result in unrestricted public access and full use

of local resources by persons living on or near the site. An on site occupational scenario

was also evaluated as an alternative future case.

Although the risks from both the average (AVG) and reasonable maximum exposure (RME)

scenarios were calculated in the risk assessment, the RME risks were used to evaluate threats

at the site because the current EPA policy mandates the use of the RME when evaluating the

need for response actions at Superfund sites. The difference between the AVG and RME risk

results from using different assumptions in the equations utilized to perform the risk

calculations. For example, the exposure frequency for AVG is 275 days per year as opposed

to 350 days per year for RME, and the exposure durations is 9 years for AVG as opposed

to 30 years for RME. RME risks are greater, and thus more conservative, than average

risks.

The highly toxic or highly mobile source materials that would present a significant risk to

human health or the environment should exposure occur are considered principal threat

wastes. On the other hand, source materials that generally can be reliably contained and that

would present only a low risk in the event of release are considered low level threat wastes.

The National Oil and Hazardous Substances Pollution Contingency Plan (NCP), Section

300.430, recommends treatment to address the principal threats posed by a site whenever

practicable, and engineering controls, such as containment, for waste that poses a relatively

low long-term threat.

6.1 HUMAN HEALTH RISK ASSESSMENT

6.1.1 Ground water

Human health risks from ground water were calculated for three basic scenarios: current

residential, future on site residential, and future off site residential use. Monitoring well and

residential well results from 1992 were used for current risks. Ground water models for

33
transport (MULTIMED, 1990) and infiltration of the landfill cover (HELP, 1989) were used

for future scenarios. Cancer slope factors were from IRIS, 1992 and HEAST, 1992.

6.1.1.1 Current Exposures - Residential Wells Off Site

Current exposure risk was calculated assuming that the residential wells are connected to the

upper Wilcox aquifer. The maximum detected levels of contaminants found in samples of

eleven monitoring wells were used. Noncancer risk from exposures to residential well water

is not significant (less than 0.01). Cancer risk from residential well water exposure (1X10"8

for average and IX 107 for RME) is below the target risk range of 1X10^ to 1X10-6. No

environmental threats from residential water supplies have been identified.

6.1.1.2 Hypothetical Future Exposures - Monitoring Wells On Site

This scenario assumes an on site residence with a well in the contaminated aquifer. It is

also assumed that the concentration of contaminants do not decrease over time. Th^, life time

excess cancer risk from monitoring well water exposure is within the target risk range of

IXIO" to 1X10-6 at 1X10^ to 1X10 -

5

. Noncancer risk is above the target level of ffl =

1 at 30 based on unfiltered monitoring well samples. The greatest contribution to total risk

is from ingestion of drinking water and inhalation of vapors while showering. The greatest

contributor to the ingestion risk is manganese; the greatest contributors to the inhalation risk

are chlorobenzene and nitrobenzene. There is slightly less risk from filtered ground water

than from unfiltered ground water (Table 7).

6.1.1.3 Hypothetical Future Exposures - Modeled Ground Water Concentrations Off Site

This third scenario is for a hypothetical residence 400 feet down gradient of the site with a

well in the upper Wilcox aquifer. The HELP model was used to calculate the percolation

rate through three types of landfill caps. These three scenarios result in percolation rates of

0.0018, 0.0181 and 10.0967 inches per year through the sludge. Results of the first two

scenarios indicated no contaminant release from sludge to the ground water for 30 years.

Results of the third scenario, which had the highest percolation rate through the cap and

therefore the highest potential for leaching, contaminant transport, and exposure, indicated

that benzene, 1,2-dichloroethene, and vinyl chloride would leach into the ground water,

resulting in estimated modeled concentrations of 23.7 jug/L, 28.5 ^g/L and 57.8 /-ig/L,

respectively. The resultant risk indicates a noncancer risk of 4X102 and a cancer risk of

1X10-3 for the RME. The source of the noncancer risk is 1,2-dichloroethene, and the

driving force of the cancer risk is vinyl chloride.

Engineering Science also modeled the transport of 1,1-DCA and 1,2-DCE in the upper

Wilcox aquifer to a receptor 700 feet down gradient using the PLUME 2D model. It is

assumed that biodegradation does not occur. Monitoring well values (1992) were used for

the contaminant concentrations. Modeled concentrations were predicted to level off at 7 ppb

and 55 ppb respectively. Monitoring results of residential wells in 1992 did not show these

contaminants at concentrations above the detection limits.

34
6.1.2 Sediment

Risks of cancer and noncancer resulting from exposure of a potential trespasser to sediments

arc within acceptable ranges. The total RME cancer risk is 1X106, and the total RME HI

is 1X10'1. Residential risk to sediment exposure also has a cancer risk below the acceptable

range (total cancer risk = 1X105).

6.1.3 Soils/Sludge

The soil exposure pathway is not likely to be significant under current conditions since the

contaminants are buried beneath 5 feet of clean fill that is stabilized with vegetation. Future

exposure risk was calculated assuming that erosion may bring the contaminants to the surface.

?'tf;Mt Lwd "iai '& iles^ •i&'SffBftA to 'iyfc "R^AKrforfi 'ccrii '(At "iWi ''aeituis^ ^ammig ^rrii

 lave^toL'&

production. Risk estimates are based on the assumption that development of the Monroe site

would result in unrestricted public access and full use of local resources by persons living

on or near the site. The potenti

 \ exposure pathways, as a result of on-site residents, include

(1) ingestion of soil and ground water, (2) ingestion of contaminated home grown vegetables,

meat, and milk, (3) dermal absorption of chemicals in the soil, sediments, and ground water,

(4) inhalation of VOC emissions from ground water, and (5) inhalation of VOC emissions

and dust particulates from the soil.

The noncancer risk from potential future residential exposure to soils is greater than the

target limit value of HI=1. The total adult HI is 5, resulting mostly from dermal exposure.

The chemical contaminant in soil that is most responsible for this risk is antimony. Cancer

risk for adults is within the target risk range, but it is at the limit of that range. The

greatest risks are from dermal absorption of contaminants in soil; the greatest contributor to

this risk is vinyl chloride.

Risks to children are comparable to risks to adults, although they are higher for the soil

ingestion pathway because of the greater ingestion rate assumed for children. Soil ingestion,

however, was not the significant pathway for soil exposures. Risks for workers on the site

and a potential trespasser who climbs the fence and is exposed to site soils would be less

than that of a resident. The risks for these potential receptors are less than the residential

risks presented here.

Soil and sludge data were combined to obtain the total risk from all soils to which future

residents at the site may be exposed. For the ingestion pathway, the noncancer risk from

sludge alone is four times greater than that from soil mixed with sludge; the cancer risk is

10 times greater. The higher concentrations of contaminants in the sludge are responsible

for this difference. Consequently, assuming the same exposure parameters for exposure to

sludge as were used for exposure to soil, the total noncancer and cancer risks for all

pathways associated with sludge can also be assumed to be 4 and 10 times greater,

respectively.

35
6.1.4 Summary of Human Health Risk

The cumulative carcinogenic risks for the three media based on reasonable maximum

exposure concentration are shown in Table 7.

Soil/sludge and unfiltered ground water exhibited cumulative carcinogenic risks greater than

10^, and non-carcinogenic HI greater than 1. Therefore, in accordance with EPA's Risk

Assessment Guidance for Superfund, only soil/sludge and ground water are considered to

present a concern to human health.

Media

Soil/Sludge

Ground water -unfiltered

Ground water - filtered

Sediment

Table 7

Cumulative

Carcinogenic

Risk

3 x 10-3

1 x 10-4

8 x 10-5

1 x 10-5

Cumulative

Non-carcinogenic

Risk

50

30

1

0.1

Combining the contaminants and media of concern, the exposure pathways and receptors and

the target goals for the contaminants of concern, remedial action goals were established

(Table 8).

Actual or threatened releases of hazardous substances from this site, if not addressed by

implementing the response action selected in this ROD, may present an imminent and

substantial endangerment to public health, welfare, or, the environment.

6.2 Ecological Risk Assessment

An ecological risk assessment was conducted to evaluate the threats the site poses to the

environment. Based upon this study, EPA determined that it is unlikely that there are any

significant impacts on surrounding ecosystems at the Monroe Auto Pit site. However, there

may be some localized impacts on the site.

Several contaminants of concern - iron, chromium, lead and mercury - actually or potentially

exceed either sediment or water quality criteria and, therefore, pose an ecological risk to the

amphibians using the ponds or seeps. The release of chemical stressors from the landfill may

have a chronic impact on the seeps and any wildlife that may use them.

36
Table 8 REMEDIAL ACTION GOALS

Contaminant of Concern

Soil/Sludge

Triehloroethylene

Vinyl chloride

Antimony

Arsenic

Beryllium

Chromium VI

Lead

Ground water

cis-1,2-Dichloroethylene

trans-1,2-Dichloroethylene

bis(2-Ethylhexyl)phthalate

Beryllium

Chromium

Lead

Manganese

Target Goal Basis

0.1-10 mg/Kg Carcinogenic Risk

20-2,000 mg/Kg Carcinogenic Risk

6 mg/Kg Noncarcinogenic Effects

0.02-2 mg/Kg Carcinogenic Risk

0.07-7 mg/Kg Carcinogenic Risk

3-300 mg/Kg Carcinogenic Risk

500 mg/Kg EPA Guidance

70 ftg/L MCL

100 ^g/L MCL

6 (ig/L MCL

4 ^g/L MCL

50 ^ig/L MCL

15 ^g/L SDWA Action Level

200 (xg/L MCL

7.0 DESCRIPTION OF ALTERNATIVES

7.1 Soil and Sludge Remedial Alternatives

Alternative 1:

Alternative 2:

Alternative 3:

Alternative 4A:

Alternative 4B:

Alternative 5:

Alternative 6:

Alternative 7:

Soil/sludge Alternatives

No action

Access and deed restrictions

Soil and vegetative cover; access and deed restrictions

Cap; slurry wall; access and deed restrictions

Cap; french drain; access and deed restrictions

Solidification/stabilization; on-site cap; access and deed restrictions

Excavation; vapor extraction; solidification/stabilization; on-site cap; access

and deed restrictions

Excavation; off-site transport and disposal in Subtitle C or D landfill.

37
7.1.1 Alternative No. 1: No Action

No remedial actions will be conducted under this alternative, and no limitations will be

placed on future uses of the site. All contaminated soil/sludge is within the site boundaries

and access is physically restricted through an existing chain link fence. The sludge is

covered by three to five feet of fill, currently preventing direct contact. Implementing no

remedial activities at the site allows the existing contaminant source to remain in place. The

potential for exposure to contaminants is not reduced in this alternative.

The present worth cost estimates for this and other alternatives are summarized in Table 9.

TABLE 9

SOIL/SLUDGE ALTERNATIVE COST SUMMARY

Alternative 2 3 4a 4b 5 6 7

Access and ;>oil and Multi-layer Multi-layer Solidification/ V a p o r Off-sit e

Dee d Vegetative Cap; Slurry Cap ; stabilization extraction ; disposa l

Restriction Cover Wall Frenc h solidification/ ( R C R A

Drain stabilization landfill)

0 ff - s i t e

disposa l

(sanitary/

industria l

landfill)

Capital

Low Estimate 0.00 276 588 733 3,037 3,339 4,600 1,900

High Estimate 0.00 330 817 1,460 7,879 8,418 10,000 3,700

0&M

Low Estimate 107 13 4 4 13 4 134 13 4 13

High Estimate 117 134 134 134 134 134

Total Cost

Low Estimate 106 410 722 867 3,171 3,473

High Estimate 117 465 951 1,594 8,013 8,552

Notes: I. Costs are in thousands of dollars

2. No costs are incurred for Alternative 1 - No Action

3. N/A - Not applicable

38

N/A N/A

N/A N/A

4,600 1,900

10,000 3,700
7.1.2 Alternative No. 2: Access and Deed Restrictions

Under this alternative, the current coyer will remain in place. Periodic inspections will be

conducted and maintenance would be performed to help ensure that the cover remains intact.

Maintenance, as needed, will consist of semi-annual mowing and repair of damaged fencing.

Minor draining modifications may be conducted as needed to prevent ponding and promote

surface water runoff.

Limitations will be placed on future uses of the site. A survey plat indicating the location

of the waste disposal area with respect to permanently surveyed benchmarks will be prepared

and filed with the local zoning authority. The plat will contain a note, prominently

displayed, which states the owner's obligation to restrict disturbance of the waste.

7.1.3 Alternative No. 3: Soil and Vegetative Cover; Access and Deed Restrictions

The existing cover will be augmented by the addition of clean soil. The soil will be

obtained locally and used to create a uniform slope across the site to promote drainage off

of the sludge disposal area. After the cover has been improved to provide adequate drainage,

a minimum six-inch layer of topsoil will be added to promote vegetative growth. The cover

will be seeded with native grasses to reduce future erosion.

Periodic inspections will be conducted and repairs performed to ensure that the cover remains

intact. Repairs, as needed, will consist of replacing eroded topsoil, reseeding bare areas,

semi-annual mowing, and repair of damaged fencing.

The improved cover will be maintained. Limitations will be placed on future uses of the

site. A survey plat indicating the location of the waste disposal area with respect to

permanently surveyed benchmarks will be prepared and filed with the local zoning authority.

The plat will contain a note, prominently displayed, which states the owner's obligation to

restrict disturbance of the waste.

7.1.4 Alternative No. 4A: Cap; Slurry Wall; Access and Deed Restrictions

A bentonite slurry wall will be constructed surrounding the area of sludge deposits. The

three-foot wide slurry wall will be installed to a depth of approximately 30 feet and will total

approximately 2100 feet in length. The bottom of the wall will be below the total depth of

the sludge deposits. However, slurry walls are most effective when they are tied into an

impermeable layer. At the Monroe Superfund site such an impermeable clay layer is about

150 feet below the surface.

Site soils displaced as a result of excavation of the trench will be spread over the sludge

area, and be covered by the cap. All excavation will be planned in uncontaminated areas.

If stained soils exhibiting possible contaminant characteristics are encountered, they will be

segregated and shipped for off-site disposal.

The slurry wall will be designed to provide a low-permeability barrier to restrict the

movement of perched ground water into the sludge. Normally a slurry wall is tied into a

39
low permeability layer at its base. Because the shallowest continuous clay layer is over 100

feet below the surface, this slurry wall will hang to a depth of 30 feet, which is below the

level of the sludge. This will mitigate to some extent perched water from entering the sludge

from below the wall.

A cap meeting the general design requirements of the Arkansas Hazardous Waste

Management Regulation 23 § 264.310 will be constructed. The cap evaluated under this

alternative includes a 24-inch thick uncompacted soil layer comprised of six inches of

uniformly distributed topsoil over 18 inches of sandy soil. The 24-inch soil layers will be

underlain by a 24-inch compacted clay layer. Components and thicknesses of the cap

specified here do not necessarily represent the final design parameters under this alternative.

If this alternative is implemented, a detailed design will be submitted and the capping

parameters will be further refined.

Deed restrictions will prohibit future development of the site. A survey plat ind"'ating the

location of the waste disposal area with respect to permanently surveyed benchmarks would

be prepared and filed with the local zoning authority. The plat will contain a note,

prominently displayed, which states the owner's obligation to restrict disturbance of the

waste.

In addition to the cap, these restrictions will eliminate the risk of long-term contact with

contaminated media. The baseline risk assessment assumed a future residential land use

scenario for the calculation of future risks. The cap and deed restrictions will eliminate the

possibility of residential land use at the site.

The multilayer cap will be periodically inspected for signs of erosion, subsidence, or damage

caused by frost or burrowing mammals. Damaged areas will be repaired to restore the cap.

The vegetation will be maintained through periodic mowing and reseeding of bare areas.

7.1.5 Alternative No. 4B: Cap; French Drain; Access and Deed Restrictions

A french drain will be constructed surrounding the area of sludge deposits. The three-foot

wide french drain will be installed to a depth of approximately 30 feet and will total

approximately 2100 feet in length. The bottom of the french drain will be below the total

depth of the sludge deposits, and will extend through the perched zone into the underlying

unsaturated zone. Site soils displaced as a result of excavation of the trench will be spread

over the sludge area and covered by the cap. All excavation will be planned in

uncontaminated areas, but if stained soils exhibiting possible contaminant characteristics are

encountered they will be segregated and shipped off-site for disposal.

The french drain will intercept perched ground water before it enters the contaminated area.

The captured ground water will be transported via buried piping to a discharge point located

in the intermittent stream southwest of the site.

A french drain suitable for this site will be constructed by excavating a 30-foot deep trench

40
and installing impermeable plastic sheeting along the sludge deposit side of the trench. A

one- to two-foot thick gravel base will be placed in the trench; slotted PVC piping will be

installed above the gravel base, and gravel fill will be installed to ground surface. The trench

parameters and its constmction method will be further refined in the detailed design process

to provide improved performance.

A cap meeting the general design requirements of the Arkansas Hazardous Waste

Management Regulation 23 § 264.310 will be constructed. The cap evaluated under this

alternative includes a 24-inch uncompacted soil layer comprised of six inches of uniformly

distributed topsoil over 18 inches of sandy soil. The 24-inch soil layer will be underlain by

a 24-inch compacted clay layer. Components and thicknesses of the cap specified here do not

necessarily represent the final design parameters under this alternative. If this alternative is

implemented, a detailed design will be performed and the capping parameters will be further

refined.

Deed restrictions will prohibit future development of the site. A survey plat indicating the

location of the waste disposal area with respect to permanently surveyed benchmarks will be

prepared and filed with the local zoning authority. The plat will contain a note, prominently

displayed, which states the owner's obligation to restrict disturbance of the waste.

In addition to the cap, these restrictions will eliminate the risk of long-term contact with

contaminated media. The baseline risk assessment assumed a future residential land use

scenario for the calculation of future risks. The cap and deed restrictions will eliminate the

possibility of residential land use at the site.

The multilayer cap and the french drain outlet will be periodically inspected for signs of

erosion, subsidence, or damage caused by frost or burrowing mammals. Damaged areas will

be repaired to restore the cap. The vegetation will be maintained through periodic mowing

and reseeding of bare areas.

7.1.6 Alternative No. 5: Solidification/Stabilization; On-site Landfill; Access and Deed

Restrictions

Solidification/Stabilization will involve excavation and removal of soil and sludge containing

contaminants that exceed remedial action goals. The total volume of soil and sludge

requiring excavation is estimated to be between 11,000 and 20,000 cubic yards. Temporary

erosion control measures will be implemented to isolate the disposal pit area and displaced

soil/sludge from the intermittent creek and springs. Impermeable tarps will be placed on the

ground surface prior to placement of the excavated material and similar tarps will also be

placed over the individual piles to avoid producing airborne particulates and contaminated

runoff. Other erosion control measures will be implemented as necessary.

Soil and sludge will be excavated from the disposal pit by backhoe or similar means. This

material will be staged in piles located in the northern fenced portion of the site pending

treatment. Soil sampling will be conducted within the excavation to confirm complete

excavation.

41
A hazardous waste landfill, meeting the general design requirements of the Arkansas

Hazardous Waste Management Regulation 23 §264 Subsection N, will be constructed in the

excavation area. Treated material will be placed into the landfill and a cap will be

constructed over the landfill. Periodic inspections of the cap and fence will be performed

to identify areas on the fence and cap that need maintenance. Maintenance will include fence

repairs, periodically mowing the cap, reseeding bare spots on the cap, and repairing erosion

areas.

Deed restrictions will also be placed on the parcel of land that will limit future development

of the site in the event Monroe relinquishes the site to another party. Access would continue

to be restricted by the existing fence. A survey plat indicating the location of the waste

disposal area with respect to permanently surveyed benchmarks will be prepared and filed

with the local zoning authority. The plat will contain a note, prominently displayed, which

states the owner's obligation to restrict disturbance of the waste.

7.1.7 Alternative No. 6: Excavation; Vapor Extraction; Solidification/Stabilization on-site

Landfill; Access and Deed Restriction

Alternative No. 6 will require excavation and removal of an estimated 11,000 to 20,000

cubic yards of soil and sludge containing contaminants that exceed remedial action goals.

Soil sampling will be conducted within the excavation to confirm required excavation depths

within the sludge pit. The excavated material will be staged in piles located in the northern

fenced portion of the site pending treatment.

Initial treatment will employ vapor extraction for organics removal. Excavated soil and

sludge will be placed in piles on an impermeable barrier. Perforated pipes will be placed

in the piles and vacuum pumps will pull ambient air through the contaminated soil/sludge,

volatilizing VOCs from the soil. Air pollution control requirements under this alternative arc

not anticipated to be necessary, but could be added if needed. Due to space limitations

onsite, excavated soils/sludge will be treated in batches.

Following the vapor extraction treatment, the soil/sludge will be solidified to immobilize the

inorganic contaminants. While one batch is being solidified, another batch will be excavated

and treated by vapor extraction. A hazardous waste landfill, meeting the general design

requirements of the Arkansas Hazardous Waste Management Regulation 23 §264 Subsection

N, will be constructed in the excavation area. Treated material will be placed into the landfill

and a cap will be constructed over the landfill.

Solidification/Stabilization of the soils and sludge will be conducted by mixing the soil/sludge

with Portland cement, resulting in a mixture that will physically immobilize the inorganic

contaminants. Solidification/Stabilization will be conducted as described in Alternative No

5. Excavation will be limited to soils/sludge containing inorganics in excess of remedial

action goals; the volume of soil/sludge to be treated is estimated to be between 11,000 and

20,000 cubic yards.

42
Maintenance of the cap and fence will be conducted through periodic inspections performed

to identify areas on the fence and cap that need maintenance. Maintenance will include fence

repairs, annual mowing of the vegetative cover, reseeding of bare spots on the cap, and

repairing eroded areas. Implementation of this alternative may require construction of

temporary erosion control structures, repair of eroded areas, and reseeding.

Deed restrictions will also be placed on the parcel of land that will limit future development

of the site in the event Monroe relinquishes the site to another party. Access will continue

to be restricted by the existing fence. A survey plat indicating the location of the waste

disposal area with respect to permanently surveyed benchmarks will be prepared and filed

with the local zoning authority. The plat will contain a note, prominently displayed, which

states the owner's obligation to restrict disturbance of the waste.

7.1.8 Alternative No. 7: Exca- ition; Off-Site Transport and Disposal in Subtitle C or

D Landfill

This alternative requires excavation, by backhoe or similar means, and removal of an

estimated 11,000 to 20,000 cubic yards of soil and sludge containing contaminants in excess

of remedial action goals. Soil sampling will be conducted in the excavation to confirm

removal of contaminated soil and sludge. The excavated material will be loaded without any

treatment into lined dump trucks and transported to either a regional sanitary landfill (such

as the Greene County landfill) or to a RCRA-permitted hazardous waste landfill.

Uncontaminated soils from local borrow pits will be used to backfill the excavation. The

site will subsequently be graded, covered with a 12-inch topsoil layer, and vegetated. No

access controls or deed restrictions will be necessary following completion of these actions.

If the delisting petition was approved by EPA, the delisted waste could then be disposed in

a sanitary or industrial landfill. If a delisting petition was not approved, pretreatment of the

waste might be necessary to meet Land Disposal Restrictions (LDRs) before the waste could

be disposed of in a hazardous waste landfill.

7.2 GROUND WATER REMEDIAL ALTERNATIVES

Alternative 1: No action

Alternative 2: Natural attenuation; ground water and residential water supply monitoring;

ground water use restrictions

Alternative 3: Ground water extraction; carbon adsorption; reinjection.

7.2.1 Alternative No. 1: No Action

Under this alternative, no action will be taken at the site and no ground water monitoring

of the existing wells will be performed. Reduction of the ground water contaminant levels

will occur through natural processes such as biological, chemical, and physical degradation,

adsorption and dispersion.

The present worth cost estimates for this and other alternatives are summarized in Table 10.

43
TABLE 10

GROUND WATER ALTERNATIVE COST SUMMARY

Alternative

No Action Natural Attenuation,

Monitoring, Use

Restrictions

Ground water

Extraction, Carbon

Adsorption,

Reinjection

Capital

Low Estimate

High Estimate

O&M

Low Estimate

High Estimate

Total Cost

Low Estimate

0

0

0

High Estimate 0

Notes: 1. Costs arc in thousand dollars.

70

71

686

1114

757

1186

472

608

2656

2830

3129

3438

44
7.2.2 Alternative No. 2: Natural Attenuation and Degradation; Ground Water Use

Restrictions; Ground Water Monitoring and Residential Water Supply Monitoring

Under this alternative, contaminant reduction will occur through natural processes such as

biological, chemical and physical degradation, adsorption, and dispersion. The use of

potentially contaminated ground water will be restricted by placing ground water use

restrictions on the site property. Ground water monitoring of on and near site wells and

residential wells will be conducted.

Initially, ground water use restrictions will be placed only on the site property.

Residential wells within one-half mile of the site will be sampled regularly for VOCs,

semivolatile organics, and inorganics, as currently conducted. Ground water from

monitoring wells on and near the site will be sampled regularly for VOCs, semivolatiles,

and inorganics. The sampling data will be reviewed to evaluate trends in ground water

quality and to determine the effectiveness of natural attenuation. Initially, residential

wells will be sampled semiannually. Monitoring wells will be sampled semiannuaiiy until

four rounds of sampling are accomplished. At that time, the data will be evaluated and

the monitoring frequency could be changed to annually. Existing wells that have

sampling data for four sampling rounds for VOCs, semivolatiles (including BEHP), and

inorganics will continue to be sampled annually. To better insure the possibility of

obtaining a sample, sampling should be scheduled during the "wet" season. Sampling

protocol will follow that in the Statement of Work. Once a trend has been defined,

sampling may be conducted on a less frequent basis. A Statement of Work, including a

Sampling and Analysis Plan will be submitted by Monroe and approved by ADPC&E.

Should monitoring indicate a degradation of residential water supplies due to site

contaminants, by an increase of five times the previous reading, or the occurrence of a

previously non-detected constituent above the MCL level, the affected residents will be

put on bottled water or a point of use water supply treatment, and the well(s) will be

immediately resampled. If a change in ground water quality in the monitoring wells is

indicated by an increase of two times for constituent levels at or above 10/xg/l and a five

times increase for constituent levels less than 10 ^g/1, the affected wells will immediately

be resampled. If any changes are verified, more frequent sampling should be performed.

If necessary, active remediation or physical/ hydraulic containment measures will be

evaluated. Should active remediation or containment measures become necessary, a ROD

amendment or explanation of significant differences will be issued.

A monitoring plan in the Statement of Work will address the monitoring criteria.

Sampling will most likely be conducted by Monroe, but could also be conducted by a

contractor to Monroe, a regulatory agency or agency contractor. In the past, residential

wells have been sampled by the Arkansas Department of Health, as well as Monroe

contractors.

Based on ground water modeling, it is assumed that the contaminant concentrations will

not exceed the Remedial Action Objectives (RAO) target goals or the MCLs at the

45
residential wells. Because all modeling is based on some assumptions about the aquifer,

contingency plans are included in this ROD. The performance standards will be met by

this alternative. Ground water use restrictions on the site will prevent future exposure to

on site water users (residents). Monitoring of the residential wells and monitoring wells

will prevent potential future threats to residential water supplies. Immediate and

secondary contingency actions are included to protect human health and the environment.

This alternative could be easily implemented as contractors, supplies, and equipment are

available locally or from regional vendors. The residential wells are currently being

sampled and the sampling could be expanded to include the site wells with a few months

notice. Cost for this alternative is included in Table 10. Maintenance will include well

upkeep, sampling analysis, data validation, and reporting.

The estimated present worth for this iltemative, including capital costs and 30 years of

O&M costs, ranges from $760,000 to $1.2 million.

7.2.3 Alternative No. 3: Ground Water Extraction; Carbon Adsorption; Reinjection

This alternative requires extraction of ground water from the Wilcox aquifer upper zone

by strategic placement of ground water recovery wells. The extracted ground water will

be passed through a treatment unit located onsite. If RAO target goals are exceeded offsite, temporary restrictions will be placed on ground water use. These restrictions will

remain in effect until target goals are met.

The extraction well locations and pumping rates will be determined during the design

phase. Collection of additional data during the design of a remediation system may be

necessary in order to further characterize the hydraulic nature of the aquifer in the area of

the recovery and injection wells.

Following treatment, ground water meeting RAO target goals will be reinjected into the

Wilcox aquifer up gradient of the contaminant plume. Monitoring of the treated effluent

will be conducted to assure that reinjected ground water complies with RAO target goals.

Maintenance will include system operation, sampling, analysis, data validation, and

reporting.

The estimated present worth for this alternative, including capital costs and 30 years of

O&M costs, ranges from $3.1 million to $3.4 million.

7.3 ARARS

CERCLA, Section 121, and the National Contingency Plan (NCP), 40 CFR Part 300,

(revised March 8, 1990) require an assessment of alternative site responses to determine

whether they attain applicable or relevant and appropriate federal and state environmental

and public health requirements (ARARs) or provide grounds for invoking one of the

identified waivers.

46
Identification of ARARs must be done on a site-specific basis. The NCP and CERCLA

do not provide across-the-board standards for determining whether a particular remedial

action will produce an adequate remedy at a particular site. Rather, the process

recognizes that each site will have unique characteristics that must be evaluated and

compared to those applicable and relevant requirements that apply under the given

circumstances. In accordance with the requirements of the NCP Section 300.400(g), the

remedial action selected must meet all ARARs unless a waiver from specific requirements

can be granted.

For remedial actions performed under CERCLA Section 121(e), permits for compliance

with the Resource Conservation and Recovery Act (RCRA), National Pollutant Discharge

Elimination System (NPDES), and the Clean Air Act (CAA) regulations for onsite

remedial actions are not required. However, CERCLA Section 121(d) requires that the

selected alternative meet relevant and appropriate regulatory standards or performance

levels where possible, even though a permit is not required. Relevant and appropriate

regulatory standards address problems or situations sufficiently similar to those

encountered at a CERCLA-regulated site; therefore, their use is well-suited to the

particular site of concern. ARARs are defined as follows:

• Applicable requirements are those cleanup standards, standards of control, and

other substantive environmental protection requirements, criteria, or limitations

promulgated under federal environmental, state environmental, or facility siting

law, that specifically address a hazardous substance, pollutant, contaminant,

remedial action location, or other circumstance found at a CERCLA site.

• Relevant and appropriate requirements are those cleanup standards, standards of

control, and other substantive environmental protection requirements, criteria, or

limitations promulgated under federal or state law that, while not "applicable"

to a hazardous substance, pollutant, contaminant, remedial action, location, or

other circumstance at a CERCLA site, address problems or situations

sufficiently similar to those encountered at a CERCLA site.

ARARs may be divided into the following categories:

• Chemical-specific requirements are health- or risk-based concentration limits or

ranges in various environmental media for specific hazardous substances, pollutants, or

contaminants. These limits may take the form of action levels or discharge levels.

• Location-specific requirements are restrictions on activities that are based on the

characteristics of a site or its immediate environment. An example would be

restrictions on wetlands development.

47
• Action-specific requirements are controls or restrictions on particular types of

activities in related areas such as hazardous waste management or waste water

treatment. An example would be RCRA incineration standards.

7.3.1 Action-Specific ARARs for Soil/Sludge

ADPC&E Regulation No. 23 §264.111 - requires that closure of the landfill must be

conducted in a manner that minimizes the need for further maintenance and controls,

minimizes or eliminates escape of hazardous waste.

\

ADPC&E Regulation No. 23 §264.114 - requires that contaminated equipment, structures,

and soils be properly disposed of or decontaminated.

ADPC&E Regulation No. 23 §264.251 - The waste piles should be constructed and

operated in a manner that complies with ADPC&E Regulation No. 23 §264.251, which

specifies waste pile design and operating requirements.

ADPC&E Regulation No. 23 §264.258 - The waste piles should be closed in compliance

with this regulation which provides requirements for the closure of waste piles.

ADPC&E Regulation No. 23 §268 - Monroe Auto Equipment disposed waste water

treatment sludge from electroplating operation (F006 waste) at the site between 1973 and

1978. Since the specific source of the sludge at the landfill is known, the time at which

the waste was disposed does not affect the waste listing and the waste would be subject to

land disposal restrictions, if excavated and treated.

ADPC&E Regulation No. 2 ARARs - State standards under Regulation No. 2, Regulation

Establishing Water Quality Standards for Surface Waters of the State of Arkansas, are

ARARs for remedial actions involving discharge of treated ground water. The standards

may be applicable if discharges are expected to affect surface waters addressed under this

regulation. If not applicable, portions of this regulation may be relevant and appropriate

if the regulation was intended to address conditions similar to those posed by some of the

remedial actions that are under consideration.

State standards under the Arkansas Underground Injection Control Code are ARARs if

treated ground water is reinjected to the aquifer. The standards may be applicable if

ground water is reinjected into ground waters addressed under these regulations. If not

applicable, portions of this regulation may be relevant and appropriate if the regulation

was intended to address conditions similar to those posed by some of the remedial actions

that are under consideration.

Clean Air Act (CAA)

40 CFR, Part 61 - National Emission Standards for Hazardous Air Pollutants (NESHAPs)

- provides standards for emissions of particular air pollutants from specific sources. Parts

of NESHAPs may be relevant and appropriate if treatment results in release of a

regulated pollutant.

48
Clean Water Act (CWA)

The Clean Water Act (CWA) requirements may be applicable because treatment may

generate fluids that need to be treated and discharged. The CWA applies to point-source

direct discharges into navigable waters and indirect discharges to a publicly owned

treatment works (POTW). In the case of indirect discharges to a POTW, the POTW sets

forth pretreatment standards.

Arkansas Water and Air Pollution Control Act

Arkansas air and water quality regulations resemble the national standards set forth by the

U.S. EPA under the Clean Air and Clean Water Acts, but require preconstruction review

by the state. In addition. Section 5 of the Arkansas Air Pollution Control Regulations

outlines specific limitations for paniculate emissions from new or modified sources.

These limits are based solely on the amount of material being processed (Ib/hr).

Arkansas Noncriteria A^ Pollutants Control Strategy

ADPC&E has implemented an evaluation of the emissions of noncriteria air pollutants

from all sources in order to determine if a permit should be issued or if an existing

source should be required to retrofit control equipment. The Noncriteria Air Pollutants

Control Strategy (NAPCS) is based upon Threshold Limit Values (TLVs) for chemical

substances adopted by the American Conference of Governmental Industrial Hygienists

(ACGIH). According to NAPCS, the predicted ambient air concentration of gases and

vapors is considered acceptable if it is less than 1/100 of the ACGIH TLV. The ambient

concentration is determined by using appropriate atmospheric dispersion models over a 24-

hour average. The spacing between receptors used in the model is 100 meters (in the

area of the highest concentration). The NAPCS may consider 8 and 24-hour averages,

first highs, as well as annual averages for use in assessing risk.

As stated in the NAPCS, when the substance emitted is a paniculate compound and

persistence in the environment is expected, the predicted annual average concentration is

considered acceptable if it does not exceed the dosage mass of the LD5o (lethal dose for

50%) expression divided by 10,000.

DOT ARARs

Department of Transportation requirements for the transportation of hazardous wastes on

public highways (49 CFR 171.1 - 172.558) are applicable to the off-site transport of

hazardous waste. State requirements for manifesting wastes and notifying the State of

out-of-state shipments of wastes are also applicable.

7.3.2 Action-Specific ARARs for Ground Water

CAA ARARs

National emission standards for hazardous air pollutants (NESHAPs) established under 40

CFR, Part 61, are not applicable because the site does not contain any of the source

categories regulated under this program. Parts of the NESHAPs may be relevant and

appropriate, however, if remediation such as ground water treatment, results in the

release of a substance regulated under the NESHAPs.

49
CWA ARARs

Discharges of treated ground water to the intermittent stream on the site may render

requirements of 40 CFR, Part 125, relevant and appropriate. These regulations address

criteria and standards for the national pollutant discharge elimination system (NPDES).

Although an NPDES permit would not be required for this discharge, parts of 40 CFR,

Part 125, may contain substantive requirements that could be relevant and appropriate

because the remedial action would be similar to the action that the requirements were

meant to address.

ADPC&E ARARs

State standards under Regulation No. 2, Regulation Establishing Water Quality Standards

for Surface Waters of the State of Arkansas, are ARARs for remedial actions involving

discharge of treated ground water. The standards may be applicable if discharges are

expected to affect surface waters addressed under this regulation. If not applicab's,

portions of this regulation may be relevant and appropriate if the regulation was intended

to address conditions similar to those posed by some of the remedial actions that are

under consideration.

State standards under the Arkansas Underground Injection Control Code are ARARs if

treated ground water is reinjected to the aquifer. The standards may be applicable if

ground water is reinjected into ground waters addressed under these regulations. If not

applicable, portions of this regulation may be relevant and appropriate if the regulation

was intended to address conditions similar to those posed by some of the remedial actions

that are under consideration.

Location Specific ARARs

ADPC&E Reg. 23§264.310, Closure and Post-Closure Care of a Landfill. The standards

may be applicable to the closed landfill. If not applicable, portions of this regulation may

be relevant and appropriate if the regulation was intended to address conditions similar to

those posed by some of the remedial actions that are under consideration.

8.0 COMPARATIVE ANALYSIS OF ALTERNATIVES

The state is required to use certain criteria to evaluate alternatives for addressing a

Superfund site. These nine criteria are categorized into three groups: threshold, primary

balancing, and modifying. The threshold criteria must be met in order for an alternative

to be eligible for selection. The primary balancing criteria are used to weigh major

tradeoffs among alternatives. The modifying criteria are taken into account after public

comment is received on the preferred alternative as identified and described in the

Proposed Plan of Action.

50
8.1 NINE CRITERIA

The nine criteria used in evaluating all of the alternatives are as follows:

Threshold Criteria

• Overall Protection of Human Health and the Environment addresses the way that an

alternative would reduce, eliminate, or control the risks posed by the site to human

health and the environment. Total elimination of risk is often impossible to achieve.

However, a remedy must minimize risks to assure that human health and the

environment are protected.

• Compliance with ARARs. or "applicable or relevant and appropriate requirements,"

assures that an a^ernative wi1! meet all related federal, state, and local requirements.

Primary Balancing Criteria

• Long-term Effectiveness and Permanence addresses the ability of an alternative to

reliably provide long-term protection for human health and the environment after the

remediation goals have been accomplished.

• Reduction of Toxicity. Mobility, or Volume of Contaminants through Treatment

assesses how effectively an alternative will address the contamination on a site.

Factors considered include the nature of the treatment process; the amount of

hazardous materials that will be destroyed by the treatment process; how effectively

the process reduces the toxicity, mobility, or volume of waste; and the type and

quantity of contamination that will remain after treatment.

• Short-term Effectiveness addresses the time it takes for remedy implementation.

Remedies often require several years for implementation. A potential remedy is

evaluated for the length of time required for implementation and the potential impact

on human health and the environment during implementation.

• Implementability addresses the ease with which an alternative can be accomplished.

Factors such as availability of materials and services and other obstacles are

considered.

• Cost (including capital costs and projected long-term operation and maintenance costs)

is considered and compared to the benefit that will result from implementing the

alternative.

Modifying Criteria

• EPA Acceptance addresses whether EPA agrees with, opposes, or has no comment on

the proposed remedy.

51
• Community Acceptance addresses comments and concerns raised by the community

and other members of the public during the public comment period for the Proposed

Plan and Administrative Record. The State considers these comments in making its

final remedy selection. The comments arc addressed in the responsiveness summary

that is part of this ROD.

8.2 COMPARATIVE ANALYSIS

8.2.1 Sludge Pit Area

Overall Protection of Human Health and the Environment • Alternative 1 (no action)

would result in exposure and an increase in contaminant migration as the existing cover

erodes or if the site is developed. Because the no action alternative is not protective of

human health and the environment, it will not be considered further in the evaluation

process.

Alternatives 2 through 6 offer the same level of protection to human health because each

alternative incorporates a cap or cover to prevent exposure, and because site access

restrictions and deed restrictions will prevent future development of the site. Alternative

7 offers additional protection even in the absence of maintenance and site access

restrictions.

Compliance With ARARs • All alternatives comply with all identified ARARs provided

they are properly implemented.

Long-term Effectiveness and Permanence • Alternative 7 provides the greatest long-term

protection because wastes are removed from the site. Alternatives 4 through 6 offer

greater reliability of protection against future migration of waste constituents through the

use of physical barriers or treatment of the waste. Of these, alternative 4B provides

greater reliability. The french drain provides a higher level of protection than a slurry

wall because ground water is less likely to contact contaminated soil and sludge. Both

alternatives 4A and 4B offer reliability in tlie form of an improved cap to hinder

infiltration. Alternatives 5 and 6 provide reliability in the control of contaminant

migration through the use of treatment. Alternatives 2 and 3 offer the least long-term

effectiveness. Under alternatives 2 and 3, the potential threat of leaching of the waste

constituents into the ground water would remain at the site.

Reduction of Toxicity. Mobility, or Volume Through Treatment • Only Alternatives 5 and

6 utilize treatment as a mechanism to achieve reduction in mobility. Alternative 6

utilizes treatment as a mechanism to achieve reduction in toxicity and mobility, but both

Alternatives 5 and 6, result in an increase in volume of contaminated material.

Short-term Effectiveness • Implementation of alternatives 2, 3, 4A, and 4B, pose no

threat of exposure to workers or to the community, and they pose no environmental

52
threat. Implementation of alternatives 5, 6, and 7, present threats of exposure to

workers, the community, and the environment because the waste would be excavated.

These alternatives would require worker protection and monitoring to ensure protection of

human health.

Implementability • No limitations have been identified for implementation of Alternatives

2 and 3. Alternatives 2 and 3 can be implemented with local or regional equipment,

personnel, and materials. Alternatives 4A, 4B, 5, and 6 may be more difficult to

implement because these services are offered by fewer contractors and are not available

locally. Alternative 7 requires acceptance of the waste by off-site disposal facilities. If

the material is disposed of as a hazardous waste, it would have to be transported out of

state for disposal.

Cost • Cost comparisons are shown in Table 9. It should be noted that costs associated

with Alternatives 5 and 6 assume that the waste is in compliance with RCRA land

disposal restrictions.

EPA Acceptance • EPAs comments on the draft proposed plan were incorporated into the

final proposed plan prior to the public comment period.

Community Acceptance • All comments received have been addressed in the

responsiveness summary, which is attached to this Record of Decision. The public, in

general, would prefer to see Alternative 7 implemented because a removal of the sludge

from the pit will permanently eliminate the human health and environmental threats from

the site. The site could then be developed into a residential setting and may result in an

increase of the neighboring property values. The residents believe that the french drain

would result in further migration of the contaminants from the site into surface water.

However, the french drain would capture ground water flow before it reaches the sludge

deposits. To ensure that no contaminated water is discharged to surface water, the water

from the french drain discharge point would be analyzed and, if necessary, treated to

meet the Arkansas surface water quality standards.

8.2.2 Ground Water

Overall Protection of Human Health and the Environment • All alternatives offer the

same immediate protection. Alternative No. 2 restricts the use of onsite ground water

and includes monitoring that would provide early detection of contaminant migration or

degradation in the quality of residential water supplies. Alternative No. 3 would

effectively reduce the total mass of contaminants. Alternative No. 3 would decrease the

time necessary for mass reduction as compared to that achieved under Alternative 1 or 2,

but may not significantly lessen the time for attainment of the ARAR for BEHP over the

time required for natural attenuation alone. Alternative No. 1 does not include

monitoring, so contaminant migration or attenuation cannot be evaluated.

Compliance With ARARs • All alternatives are expected to result in long-term compliance

53
with ARARs in the residential water supplies. Natural attenuation and degradation, which

would occur under all alternatives, are expected to result in ARAR compliance for 1,2-

DCE and for BEHP.

Long-term Effectiveness and Permanence • All alternatives are predicted to result in a

reduction in risk and are expected to result in compliance with ARARs in residential

water supplies. Alternative 2 offers the additional protection of restrictions on uses of

ground water at the site. Alternative 3 would reduce the total mass of contamination in

the aquifer in less time than Alternatives 1 and 2.

Reduction of Toxicity. Mobility, or Volume Through Treatment • Only Alternative 3

employs treatment. Under Alternative 3, the mass of contaminants in the aquifer would

be reduced. These contaminants would be transferred to activated carbon, which would

require regeneration or disposal at an off-site facility.

Short-term Effectiveness • None of the alternatives pose a threat to the local community.

Alternative 3 poses a potential threat to site workers who are exposed to contaminated

ground water, but these threats would be mitigated by the use of protective equipment.

Implementability • Alternative 1 requires no action. Alternative 2 is easily implementable

and services are available locally or regionally. Alternative 3 is easily implementable

with commercially available products and services. This alternative would, however,

require extensive O&M activities.

Cost • Cost comparisons are shown in Table 10. Alternative 2 would be the most cost

effective. Alternative 3 may result in a shortened remediation time, but the low

concentrations of the contaminants in ground water and the large volume of water

(estimated at 40 million gal./yr.) that would need to be treated, make alternative 3

inefficient. Alternative 3 would also require disposal or renewal of carbon filters at an

added cost. Alternative 1 is the least costly. The difference in time required for

remediation does not justify the additional cost of treatment.

EPA Acceptance • EPAs comments on the draft proposed plan were incorporated into the

final proposed plan prior to the public comment period.

Community Acceptance • Public comments and responses to those comments are included

in the responsiveness summary. The public would prefer alternative 3, treatment, or

being connected to the Raragould public water supply system. The residents believe that

their water is contaminated, when in fact, tests show that the water meets the criteria for

safe drinking water.

54
9.0 THE SELECTED REMEDY

Based upon consideration of the requirements of CERCLA, a detailed analysis of the

alternatives using the nine criteria, and public comment; both EPA and the State have

determined that a combination of alternative 4b for soil/sludge, a fnench drain and a cap,

and alternative 2 for ground water, natural attenuation and degradation with monitoring, is

the most appropriate remedy for the Monroe Auto Pit Superfund site in Raragould,

Arkansas.

9.1 SOIL AND SLUDGE REMEDIATION

The selected remedy for addressing the contaminated soil/sludge in the pit area is

Alternative 4b. The original waste contained a high volume of liquids, which is believed

to have been the primary source for ground water contamination at the site. Sludge

samples collected during the RI contained no free liquids. Analytical data from testing of

leachate produced by the toxicity characteristic leaching procedure (TCLP) show very low

leachability of the contaminants in the soil and sludge. (The TCLP data are presented in

Section 4 of the RI). In accordance with the NCP Section 300.430 and OSWER

Directives, the State has determined that the soil/sludge deposits in the pit area pose a

relatively low, long-term threat; and that through the use of engineering controls (such as

containment) and deed restrictions the soil/sludge material can be reliably contained.

A french drain will be constructed surrounding the area of sludge deposits. The threefoot wide french drain will be installed to a depth of approximately 30 feet and will total

approximately 2100 feet in length. The bottom of the french drain will be below the

total depth of the sludge deposits, and will extend through the perched zone into the

underlying unsaturated zone. Site soils displaced as a result of excavation of the trench

will be spread over the sludge area, and be covered by the cap. All excavation will be

planned in uncontaminated areas; but if stained soils exhibiting possible contaminant

characteristics are encountered they will be segregated and shipped off-site for disposal.

A french drain will restrict ground water movement into the area of contaminated soil and

sludge. The french drain will also intercept perched ground water before it enters the

contaminated area. The captured ground water will be transported via buried piping to a

discharge point located in the intermittent stream southwest of the site. Water from the

french drain will be tested to ensure the Arkansas surface water quality criteria are met.

A french drain suitable for this site will be constructed by excavating a 30-foot deep

trench and installing impermeable plastic sheeting along the sludge deposit side of the

trench. A one- to two-foot thick gravel base will be placed in the trench; slotted PVC

piping will be installed above the gravel base, and gravel fill will be installed to ground

surface. The trench parameters and its construction method will be further refined to

provide improved performance in the detailed design process.

55
The cap evaluated under this alternative includes a 24-inch uncompacted soil layer

comprised of six inches of uniformly distributed topsoil over 18 inches of sandy soil.

The 24-inch soil layer will be underlain by a 24-inch compacted clay layer. Components

and thicknesses of the cap specified here do not necessarily represent the final design

parameters under this alternative. If this alternative is implemented, a detailed design will

be provided and the capping parameters will be further refined.

Deed restrictions will prohibit future development of the site. A survey plat indicating

the location of the waste disposal area with respect to permanently surveyed benchmarks

would be prepared and filed with the local zoning authority. The plat will contain a

note, prominently displayed, which states the owner's obligation to restrict disturbance of

the waste.

In addition to the cap, these restrictions will eliminate the risk of long-term contact with

contaminated media. The baseline risk assessment assumed a future residential land use

scenario for the calculation of future risks. The cap and deed restrictions will eliminate

the possibility of residential land use at the site.

The multilayer cap and the french drain outlet will be periodically inspected for signs of

erosion, subsidence, or damage caused by frost or burrowing mammals. Damaged areas

will be repaired to restore the cap. The vegetation will be maintained through periodic

mowing and reseeding of bare areas.

ADPC&E believes that based on the current information the selected remedy will provide

the best balance among the alternatives with respect to the two threshold and five primary

balancing criteria. The alternative will: (1) prevent direct contact, ingestion and inhalation

of contaminants in the sludge and ancillary contaminated soil and debris; (2) prevent the

future migration of contaminants from the sludge area to the surface; and (3) prevent the

potential for future migration of contaminants to the ground water. The selected remedy

if implemented properly, will comply with all applicable and relevant or appropriate

requirements identified for the site.

The alternative will achieve long-term permanence and effectiveness. The cap combined

with the french drain will permanently isolate the contaminants in the sludge pit area from

surrounding media. There are no expected unmanageable short-term risks associated with

this alternative. The alternative is implementable and cost effective. Even though a

residential scenario was utilized to calculate the risks associated with the contaminants at

the site, none of the alternatives, with the exception of Alternative 7, will allow the

residential development of the site to occur.

The estimated capital cost to implement the selected remedy ranges from $730,000 to

$1.5 million. The capital cost includes engineering, equipment and materials, testing, and

site support. The annual O&M costs is estimated at $14,000 per year in 1993 dollars.

The estimated present worth for the selected remedy, including capital costs and 30 years

of O&M costs, ranges from $870,000 to $1.6 milFon.

56
9.2 GROUND WATER REMEDIATION

The selected remedy addresses the ground water contamination through natural attenuation,

degradation, and monitoring. The source of the contamination is the liquids that were

part of the original sludge deposited in the pit. When first deposited, the sludge was

about 85% liquid. These liquids migrated into the ground water where we find them

today. In this respect, the source of continuing contamination has been removed.

The levels of the contaminants of concern seen in the upper Wilcox aquifer on the site

decrease away from the sludge pit area. It is expected that this trend of decreasing

values will continue. Regular monitoring of the monitoring wells and the residential wells

will provide continuous evaluation of the effects of natural attenuation and degradation in

the ground water system. In the unlikely event that monitoring indicates a degradation of

residential well water, by an increase of five times the previous reading, or the

occurrence of a previously non-aetected constituent above the MCL level, the affected

residents will be put on bottled water or a point of use water supply treatment, and the

well(s) will be immediately resampled. If a change in ground water quality in the

monitoring wells is indicated by an increase of two times for constituent levels at or

above 10/xg/l and a five times increase for constituent levels less than 10 /zg/1, the

affected wells will immediately be resampled. If any changes are verified, more frequent

sampling should be performed. If necessary, active remediation or physical/ hydraulic

containment measures will be evaluated. Should these measures become necessary, a

ROD amendment or an explanation of significant differences will be issued.

Ground water use restrictions will be in place on the site until the contaminant levels are

below the remedial action goal levels. Monitoring wells to be sampled will be sufficient

in number and location to delineate the contaminant plume and to detect contaminant

migration. Contaminated ground water must be kept within the legal site boundaries.

The exact monitoring wells and their locations will be determined as part of the design

phase for the french drain. Monitoring shall be semi-annually for two years or until four

samples have been taken for volatiles, semi-volatiles (including BEHP), and metals for

statistical analysis. The statistical method used will be as specified in the Statement of

Work. Monitoring could be required for 30 years or more.

Capital costs for this alternative are estimated from $70,000 to $71,000. This would

include development of a sampling plan and abandonment of wells not kept in the

monitoring system. Operation and maintenance costs for this remedy include sampling,

analysis, data validation, and reporting. The cost is estimated at $73,000 to $120,000

per year in 1993 dollars. This figure assumes that the current monitoring plan does not

change. The estimated present worth including capital costs and 30 years of O&M costs is

from $760,000 to $1.2 million.

57
10.0 STATUTORY DETERMINATIONS

The primary responsibility at Superfund sites is to select remedial actions that are

protective of human health and the environment. Section 121 of CERCLA also requires

that the selected remedial action comply with applicable or relevant and appropriate

environmental standards established under federal and state environmental laws, unless a

waiver is granted. The selected remedy must be cost-effective and utilize permanent

solutions and alternative technologies or resource recovery technologies to the maximum

extent practicable. The Statute also contains a preference for remedies which employ

treatment that permanently and significantly reduce the volume, toxicity, or mobility of

hazardous wastes as a principal element. The following sections discuss how the selected

remedy meets the statutory requirements.

10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT

10.1.1 Soil and Sludge

The soil/sludge selected remedy meets all of the soil and sludge remedial action objectives

through limitations on site development and inadvertent access, and by eliminating the

potential for long-term direct contact with contaminated soil/ sludge. Contaminant mobility

will be minimized or prevented because the french drain will isolate the contaminated

soil/sludge from the perched ground water table and the cap will minimize infiltration and

erosion. Deed restrictions and site access restrictions will prohibit any use of the site that

would result in contact with contaminated media, and will limit any human or

environmental contact with contaminated media.

Short term risks associated with the selected remedy can be controlled by proper design

and implementation. No adverse cross media impacts are expected from implementation

of the selected remedy.

10.1.2 Ground Water

Because the onsite contamination is in the upper Wilcox aquifer and the private wells are

believed to produce from the lower Wilcox aquifer, a complete exposure pathway does

not exist at this time. A cap on the sludge deposit area and a french drain will prevent

infiltration of precipitation and perched ground water into the sludge. The selected

remedy will protect human health and the environment by natural attenuation and

degradation of the contaminants of concern. Ground water use restrictions for the on site

ground water will prevent contact with contaminated ground water. Monitoring of the

residential wells will provide continuous assessment of the effects of natural attenuation

and in this way protect human health and the environment. There are no short-term

threats associated with the selected remedy for ground water that cannot be readily

controlled. In addition, no adverse cross-media impacts are expected from the remedy.

58
10.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND

APPROPRIATE REQUIREMENTS

The selected remedy of cap, French drain, access and deed restrictions for soil and sludge

and natural attenuation and degradation, ground water use restrictions, and ground water

monitoring for ground water remediation will comply with all applicable or relevant and

appropriate requirements (ARARs), if properly designed and implemented. The ARARs

for the selected remedy are presented below.

10.2.1 SoU and Sludge

Action-Specific ARARs

ADPC&E Regulation No. 23 §264.111 - closure of the landfill, must be conducted in a

manner that minimizes the need for further maintenance and controls, and minimizes or

eliminates escape of hazardous v'aste.

ADPC&E Regulation No. 23 §264.114 - requires that contaminated equipment, structures,

and soils be properly disposed of or decontaminated.

ADPC&E Regulation No. 23 §264.251 - The waste piles should be constructed and

operated in a manner that complies with ADPC&E Regulation No. 23 §264.251, which

specifies waste pile design and operating requirements.

ADPC&E Regulation No. 23 §264.258 - The waste pile should be closed in compliance

with this regulation which provides requirements for the closure of a waste pile.

Regulation No. 23 §268 - Monroe Auto Equipment disposed of waste water treatment

sludge from electroplating operations (F006 waste) at the site between 1973 and 1978.

Since the specific source of the sludge at the landfill is known, the time at which the

waste was disposed does not affect the waste listing and the waste would be subject to

land disposal restrictions, if excavated and treated.

Clean Air Act (CAA)

40 CFR, Part 61 - National Emission Standards for Hazardous Air Pollutants (NESHAPs)

- provides standards for emissions of particular air pollutants from specific sources. Parts

of NESHAPs may be relevant and appropriate if treatment results in release of a

regulated pollutant.

Clean Water Act (CWA)

The Clean Water Act (CWA) requirements may be applicable because treatment may

generate fluids that need to be treated and discharged. The CWA applies to point-source

direct discharges into navigable waters and indirect discharges to a publicly owned

treatment works (POTW). In the case of indirect discharges to a POTW, the POTW sets

forth pretreatment standards.

59
Arkansas Water and Air Pollution Control Act

Arkansas air and water quality regulations resemble the national standards set forth by the

U.S. EPA under the Clean Air and Clean Water Acts, but require preconstruction review

by the state. In addition, Section 5 of the Arkansas Air Pollution Control Regulations

outlines specific limitations for particulate emissions from new or modified sources.

These limits are based solely on the amount of material being processed (Ib/hr).

ADPC&E ARARs

State standards under Regulation No. 2, Regulation Establishing Water Quality Standards

for Surface Waters of the State of Arkansas, are ARARs for remedial actions involving

discharge of ground water. The standards may be applicable if discharges are expected to

affect surface waters addressed under this regulation. If not applicable, portions of this

regulation are relevant and appropriate to address conditions similar to those posed by

some of the remedial actions that are under consideration.

Arkansas Noncriteria Air Pollutants Control Strategy

ADPC&E has also implemented an evaluation of the emissions of proposed emission of

noncriteria air pollutants from all sources in order to determine if a permit should be

issued or if an existing source should be required to retrofit control equipment. The

Noncriteria Air Pollutants Control Strategy (NAPCS) is based upon Threshold Limit

Values (TLVs) for chemical substances adopted by the American Conference of

Governmental Industrial Hygienists (ACGIH).

According to NAPCS, the predicted ambient air concentration of gases and vapors is

considered acceptable if it is less than 1/100 of the ACGIH TLV. The ambient

concentration is determined by using the spacing between receptors used in the model of

100 meters (in the area of the highest concentration). The NAPCS may consider 8 and

24-hour averages, first highs, as well as annual averages for use in assessing risk.

As stated in the NAPCS, when the substance emitted is a particulate compound and

persistence in the environment is expected, the predicted annual average concentration is

considered acceptable if it does not exceed the dosage mass of the U^o (lethal dose for

50%) expression divided by 10,000.

DOT ARARs

Department of Transportation requirements for the transportation of hazardous wastes on

public highways (49 CFR 171.1 - 172.558) are applicable to the off-site transport of

hazardous waste. State requirements for manifesting wastes and notifying the State of

out-of-state shipments of wastes are also applicable.

60
ADPC&E ARARs

State standards under Regulation No. 2, Regulation Establishing Water Quality Standards

for Surface Waters of the State of Arkansas, are ARARs for remedial actions involving

discharge of treated ground water. The standards may be applicable if discharges are

expected to affect surface waters addressed under this regulation. If not applicable,

portions of this regulation may be relevant and appropriate if the regulation was intended

to address conditions similar to those posed by some of the remedial actions that are

under consideration.

State standards under the Arkansas Underground Injection Control Code are ARARs if

treated ground water is reinjected to the aquifer. The standards may be applicable if

ground water is reinjected into ground waters addressed under these regulations. If not

applicable, portions of this regulation may be relevant and appropriate if the regulation

was intended to address conditions sinrlar to those posed by some of the remedial actions

that are under consideration.

10.2.2 Ground Water

The selected remedy meets all action and location specific ARARs. Chemical specific

ARARs would not be immediately met under this remedy. Groundwater modeling

predicts that for 1,2-DCE concentrations ARARs would be attained within one year.

ARARs for BEHP will be met in the future, possibly within 30 years. ARARs are not

expected to be exceeded in residential water supplies at any time.

10.2.3 Action-Specific ARARs for Ground Water

CAA ARARs

National emission standards for hazardous air pollutants (NESHAPs) established under 40

CFR, Part 61, are not applicable because the site does not contain any of the source

categories regulated under this program. Parts of the NESHAPs may be relevant and

appropriate, however, if remediation such as with ground water treatment, results in the

release of a substance regulated under the NESHAPs.

CWA ARARs

Discharges of treated ground water to the intermittent stream on the site may render

requirements of 40 CFR, Part 125, relevant and appropriate. These regulations address

criteria and standards for the national pollutant discharge elimination system (NPDES).

Although an NPDES permit would not be required for this discharge, parts of 40 CFR,

Part 125, may contain substantive requirements that could be relevant and appropriate

because the remedial action would be similar to the action that the requirements were

meant to address.

ADPC&E ARARs

State standards under Regulation No. 2, Regulation Establishing Water Quality Standards

for Surface Waters of the State of Arkansas, are ARARs for remedial actions involving

discharge of treated ground water. The standards may be applicable if discharges are

61
expected to affect surface waters addressed under this regulation. If not applicable,

portions of this regulation may be relevant and appropriate if the regulation was intended

to address conditions similar to those posed by some of the remedial actions that are

under consideration.

State standards under the Arkansas Underground Injection Control Code are ARARs if

treated ground water is reinjected to the aquifer. The standards may be applicable if

ground water is reinjected into ground waters addressed under these regulations. If not

applicable, portions of this regulation may be relevant and appropriate if the regulation

was intended to address conditions similar to those posed by some of the remedial actions

that are under consideration.

Location Specific ARARs

ADPC&E Reg. 23§264.3JO, Closure ind Post-Closure Care of a Landfill. The standards

may be applicable to the closed landfill. If not applicable, portions of this regulation may

be relevant and appropriate if the regulation was intended to address conditions similar to

those posed by some of the remedial actions that are under consideration.

10.3 COST EFFECTIVENESS

10.3.1 SoU and Sludge

ADPC&E believes that the selected remedy for soil and sludge will eliminate the risks to

human health at an estimated cost of $870,000 to $1.6 million. Even though the selected

remedy does not provide for a reduction in the toxicity or volume of contaminants in the

soil and sludge, the capping and the french drain will substantially reduce the mobility of

the contaminants. The selected remedy provides an overall effectiveness proportionate to

its costs, such that it represents a reasonable value for the money that will be spent.

10.3.2 Ground Water

The low concentrations of contaminants in the upper Wilcox aquifer and the lack of a

complete contaminant pathway make the selected remedy the most cost effective remedy

for ground water. ADPC&E believes this remedy will eliminate the risks to human

health and the environment at an estimated cost of $760,000 to $1.2 million, therefore the

selected remedy provides an overall effectiveness proportionate to its cost, such that it

represents a reasonable value for the money that will be spent. The difference in time

required for remediation does not justify the additional cost of treatment.

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10.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE

TREATMENT TECHNOLOGIES TO THE MAXIMUM EXTENT

PRACTICABLE

10.4.1 Soil and Sludge

ADPC&E has determined that the selected remedy represents the maximum extent to

which permanent solutions and treatment technologies can be utilized in a cost-effective

manner for contaminated soil and sludge. Of those alternatives that are protective of

human health and the environment and comply with ARARs, ADPC&E has determined

that the selected remedy provides the best balance in terms of long-tsrm effectiveness and

permanence; reduction in toxicity, mobility, or volume achieved through treatment; shortterm effectiveness; implementability; and cost while also considering the statutory

preference for treatment as a principal element and considering EPA and community

acceptance.

10.4.2 Ground Water

All of the ground water alternatives are equal with respect to long-term effectiveness and

permanence, short-term effectiveness and Implementability. AH of the alternatives will

meet the action and chemical ARARs at some future date. Alternative 3 is the only

alternative to employ treatment of the ground water. Balancing cost effectiveness against

treatment, alternative 2 achieves the same goals with less cost and a minimal increase in

time. Because a complete contaminant pathway may or may not exist at this time,

ADPC&E believes alternative 2 is the appropriate remedy for this site.

10.5 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT

The selected remedy for soil/sludge and ground water is protective of human health and

the environment, complies with federal and state requirements that are legally applicable

or relevant and appropriate to the remedial action, and is cost-effective. The selected

remedy utilizes permanent solutions and alternative treatment to the maximum extent

practicable for this site. However, because treatment of the principal threats of the site

was not found to be practicable, this remedy does not satisfy the statutory preference for

treatment as the principal element.

Because this remedy will result in hazardous substances remaining on-site above healthbased levels, a review will be conducted within five years after commencement of

remedial action to ensure that the remedy continues to provide adequate protection of

human health and the environment.

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11.0 DOCUMENTATION OF SIGNIFICANT CHANGES

The Proposed Plan for the Monroe Auto Pit site was released for public comment in July

1995. The Proposed Plan identified alternative 4b, cap, french drain, access and deed

restrictions, as the preferred alternative for soil and sludge remediation and alternative 2,

natural attenuation, ground water and residential water supply monitoring, and ground

water use restriction as the preferred alternative for the ground water remediation.

ADPC&E reviewed all written and verbal comments submitted during the public comment

period. Upon review of these comments, it was determined that no significant changes to

the remedy, as originally identified in the Proposed Plan, were necessary.

12.0 RESPONSIVENESS SUMMARY

This Responsiveness Summary has been prepared to provide written responses to

comments received at the public meeting and during the Public Comment Period for the

Proposed Plan of Action for the Monroe Superfund Site. One public meeting was

conducted on August 8, 1995 during the Public Comment Period. The transcript of this

meeting is included in the Administrative Record. Written comments on the Proposed

Plan were submitted by Monroe Auto Equipment Incorporated, McMath Law Firm, P.A.,

and a few concerned citizens.

Comment ffl

Everyone I know in this area is having to use bottled water for drinking and cooking

now. The recommended action will do nothing to improve this situation except wait and

hope it goes away.

Response ff 1

The private wells within a l / ^ mile radius of the site have been and will continue to be

tested. All results obtained to date indicate that the concentration of contaminants in

these wells are below MCLs. This means that the water from private wells is safe to

drink. In addition, this Record of Decision provides the means by which to ensure the

safety of the drinking water in the future. The decision by area residents to use bottled

water to cook and drink is voluntary. Ground water models indicate that the

contaminants will degrade naturally to safe levels before they could possibly reach any of

the residential wells.

Comment ffl

Environmental laws/processes focus on environmental and health issues. In doing this,

64
economic issues (such as property values) may be indirectly impacted, but these types of

economic issues do not directly influence the decision making process.

I saw several references to cost benefits. It would seem that if you determine that the

cost is too high to do anymore than outlined, you would specify that some of the savings

be directed toward rectifying damages.

Response ff2

The cost of a remedy is just one of the nine criteria considered in the remedy selection

process. The two threshold criteria 1) overall protection of human health and the

environment, and 2) compliance with ARARs (applicable or relevant and appropriate

requirements of federal and state environmental statutes), must be met prior to other

considerations. ADPC&E believes that the selected remedy for the Monroe Auto Pit

provides the best balance among the alternatives with respect to the threshold and primary

balancing criteria. Therefore it is not justifiable to choose a more expensive remedy

when a less expensive remedy can meet all the objectives.

Comment ff3

It is difficult to understand how this French Drain option is going to do anything except

catch all the pollution and put it in the creek. I certainly would not allow this to happen

to my property.

Response #3

The purpose of placing a french drain around the sludge pit is to intercept the perched

ground water before it enters the contaminated area. The perched ground water collected

at the french drain is expected to be "clean." However, the water will be tested and, if

necessary, treated to ensure that the State's surface water quality criteria are met.

Comment #4

As I understand the action that you intend to take, no solidification of the contaminated

material will take place and no effort to filter the hydrocarbons out of the aquifer will

take place. I do not think this is good enough.

Response # 4

As part of the Remedial Investigation/Feasibility Study (RI/FS), Monroe conducted a

Treatability Study on several treatment technologies. Solidification/Stabilization was one

of the technologies investigated in that study.

In general, solidification is used to reduce/eliminate the rate at which contaminants leach

65
from a contaminated matrix. One way to measure the performance of

solidification/stabilization is for the solidified matrix to pass the TCLP test. In Monroe's

case, however, the study indicated that prior to any treatment, sludge/soil present at the

pit would pass the TCLP tests.

The chlorinated hydrocarbons present in the on-site ground water will degrade by natural

processes. Based on ground water modeling and the analytical data from the monitoring

wells and private wells to date, it appears that the contaminant levels will degrade

naturally within a reasonable time period without endangering human health or the

environment. Filtering contaminants out (pump and treat) may reduce the time necessary

to meet Target RAOs. The levels of contamination that we see at the site can easily

degrade before they reach any off site well locations. This short time decrease does not

warrant the extra expense.

Comment #5

I had nothing to do with the illegal dumping of the chlorinated hydrocarbons in the pit

and do not understand why we must still have this problem.

Response ff5

At the time, when Monroe disposed of its sludge into the pit, most of the environmental

laws that are in-place today were nonexistent. Thus, Monroe did not dispose of the

sludge into the pit illegally. The selected remedy specified in this ROD, if designed and

implemented properly, will provide adequate protection of the human health and the

environment.

Comment ff6

I formally request at least a six month delay before a final action decision is made.

Response ff6

The Superfund Program emphasizes the importance of community involvement.

Therefore, prior to the release of the Proposed Plan, EPA had conducted an ongoing

community relations program to ensure that the citizens had ample opportunity to voice

opinions, receive answers to their questions, and provide meaningful input into the

decision making process.

Based on a number of requests, a two month extension of the comment period on the

Proposed Plan of Action was granted. This made the comment period on the Proposed

Plan a total of three (3) months. ADPC&E believes three months was sufficient for the

comment period.

66
Comment #7

I am sending this written comment since it was requested, but I have no confidence that

any change in the planned action will take place; I hope I am wrong.

Response ff7

After careful consideration of all public comments on the Proposed Plan, ADPC&E

determined that no significant changes to the preferred remedy are necessary.

Comment ffS

When I moved here this area was a premier home site, now it is practically worthless. I

was expecting some help from ^e government; I do not see it yet.

Response ff8

Various elements could affect the property value at a given location. One such element is

nearness to a Superfund site. Even though a Superfund site may not physically affect a

given neighboring community in any way or fashion, the bad perception of living close to

a Superfund site is one which cannot be easily altered. In this particular situation, as

soon as all remedial objectives are met, the State will make efforts to delete the site from

the National Priorities List (NPL) in an expedited manner. We hope that this action will

provide some relief to property values surrounding the site.

Comment ff9

When we would get results on our well water, and a letter from Monroe, saying

everything checks out "fine". We trusted Monroe. We had no idea what the results

showed. But after we received a copy of the Proposed Plan of Action, we got all our

results out and started comparing them. There is none of them the same, and if there was

a higher amount found from one time to the next. The limits go up, from what we

understand by comparing them, we have question about the limits?

For example:

Surrogate % Recovery Q.C. Limits

12/6/94

Bromo-1-chloropropane 81 50 125

Flurobenzene 104 50 125

6/30/94

l,4,Dichlorobutane 68 50 125

Flurobenzene 102 50 125

Does this mean we are in the limits? If it does, we sure are close to over going the

limits.

67
Response ff9

Above is an example of laboratory QA/QC information. Laboratory QA/QC samples are

measures of instrument and laboratory performance. They provide data that is necessary

to determine the quality of sample analyses. In this instance, laboratory grade water is

spiked with the analyte of interest to monitor the accuracy of analysis of the laboratory

performance method used.

The concentration of contaminants shown on your reports provide the necessary

information in relation to quality of the water and, therefore, would be of significance to

the well owners.

Comment fflO

My husband never could drink our well water. It always made him sick. We never

realized taking a shower may be harmful to my family. We still wouldn't have known if

we hadn't went to the library and looked up all these words, and they all mean the same.

They are all, very much a danger to human health. So taking all this and more into

consideration, we feel we really need more time to really look at all this with our eyes

open.

Response fflO

The concentration of contaminants in private well waters are below MCLs and therefore

the water from the private wells is safe to drink. This also implies that the water is not

harmful to human health when taking a shower, washing dishes, or for any other

domestic use.

Comment ffll

Alternative No. 2 is not aggressive enough at cleaning up this site and protecting human

health and the environment. It would seem much more appropriate to implement a

combination of ground water Alternatives No. 2 and No. 3 and remove and treat ground

water from all contaminated zones at least in the source area and immediately

downgradient. Wells placed strategically downgradient of the site could be operated

periodically to remove as much contaminants as possible, prevent contaminant migration

and result in much better protection of human health and the environment at a reasonable

cost.

Response ffll

The upper Wilcox aquifer and the perched aquifer are the only zones to show

contamination. The perched water zone has not produced enough water to sufficiently

test, but because of its contact with the sludge when it was deposited, and because it

appears to be linked hydraulically to the upper Wilcox aquifer, we have assumed that it

68
has been contaminated as well. The levels of contamination that we see at the site can

easily degrade before they reach any off site well locations. The private wells produce

from the lower Wilcox aquifer which is not contaminated by the Monroe site. Ground

water models have shown that with a cap of low permeability soil, that after 30 years the

concentration of contaminants of concern 400 feet from the site are equal to zero. The

RCRA type cap that is recommended for this site would allow even less infiltration than

that of the model.

Based on the ground water modeling and the analytical data from the monitoring wells

and private wells to date, it appears that the contaminant levels will degrade naturally

within a reasonable time period without endangering human health or the environment.

Pumping of the contaminated water may decrease the amount of time necessary to reduce

the contaminant levels for volatile organics, but only by one year as compared to two

years for natural degradation. This short time decrease does not warrant the extra

expense.

Comment ftll

The planned capping of Alternative 4-B will not prevent leaking into the sludge and, as a

result, there will be significant pressure against the liner in the french drain. All caps

leak to some degree. It will be nearly, if not totally, impossible to construct a watertight

"plastic sheeting" at such depths, so the hydrostatic pressure from sludge areas can

migrate into the French drain. In addition, Alternative 4-B will not relieve the ground

water leading to deeper aquifers which show some contamination. The design of

Alternative 4-B will actually serve as a system to confine more pressure in a column over

the sludge area and into the lower units since no cap is impervious.

For the reasons presented here, the ground water must be removed and treated.

Otherwise, low levels of contaminants can continue to leach out and, once discovered in

private deep wells, the plume of unacceptable contaminant levels could be very large, and

very expensive to clean up.

Response ffl2

ADPC&E disagrees that implementation of Alternative 4b would result in continued

leaching of contaminants into the ground water.

The cap intended for the Monroe Auto Pit shall be designed and constructed to meet the

requirements of Arkansas Hazardous Waste Management Regulation 23 § 246.310. This

low permeability cap minimizes infiltration of surface precipitation into the sludge pit and

directs surface water away from the pit area. Thus, infiltration through the cap and into

the sludge is insignificant.

69
In addition, gravitational force would direct the effluent from the french drain to a surface

discharge point. Such a discharge must meet the Arkansas Surface Water Quality

Standards.

Also, it is important to remember that the analytical data from testing of leachate

produced by the toxicity characteristic leaching procedure (TCLP) show very low

leachability of the contaminants from the sludge and that the sludge even in its present

condition is no longer a primary source of ground water contamination.

Comment #13

I am very disappointed with this plan and I feel it should be taken out of the area

completely and all wells (residential) should be replaced by Monroe and/or a rural water

system placed in the area and Monro^ pays for all expense.

Response #13

A complete removal of the sludge from the site has a number of advantages that other

alternatives do not provide. The removal alternative offers additional overall protection of

human health and the environment, provides the greatest long-term protection, and is the

only alternative that, if implemented, would not require site access restrictions (fence) and

site maintenance. The site could actually become a residential area. However, the

relatively low long-term threat posed by the soil/sludge deposits in the pit area, combined

with the agency's preference for on-site remedies are among the main factors that hamper

selection of a treatment/removal remedy.

The State would certainly entertain the removal option if Monroe volunteers to do so. In

the absence of this voluntary action, the State cannot justify the recommendation that

removal be the preferred remedial action.

Residential well water meets the safe drinking water standards. Replacement of

residential wells and/ or an extension of the rural water system to the areas near the site

by Monroe is neither necessary nor justified.

Comment #14

I have a slime that forms in our bathroom everyday and you can not tell me where is it

coming from! Please help us in this matter! We need suitable drinking water, now!

Response #14

The Arkansas Department of Health investigated the slime issue and found no bacteria in

the well water. The slime in the bathroom must have another source. The residential

well water is a suitable source of drinking water.

70
Comment #15

We can not sell our homes and move - because the mortgage companies will not loan

money on this area. Homes and properties will not sell in this area.

Response ffl5

The State can only provide information regarding the status of the site to the mortgage

company. The impact of the site information on mortgage company decisions is out of the

control of ADPC&E. Please see Response #2.

Comment #16

We own 40 acres of land joining S-9 Dowler and S-11 Krosp property. We arc very

much interested in having the creek water and pond water on our property tested. There

has been an incident with a layer of oily residue showing up on top of the ground as we

tried to plant a tree on our property. Please let us know how to get the water tested and

soil samples taken.

Response #16

Water has been observed to flow from a spring located in the ravines on the southwestern

portion of the site for 12 to 24 hours following heavy or extended precipitation. Water

from this spring and runoff from the sludge pit area enters the ravines and flows into an

intermittent stream that leaves the site at the southwestern site boundary and joins Village

Creek nearly a mile southwest of the site. During the site investigation, in general, the

greatest surface water and sediment contaminant concentrations were observed near the

site. These concentrations decreased downstream of the site. In addition, the above

property appears to be at least 1000 feet east of this intermittent stream. Therefore, the

suspected contaminants on the said property are not site related. ADPC&E does not plan

to perform sampling at this time. If you wish, you may contact a certified laboratory in

your area for sampling information.

Comment #17

Some of our property is within the one half mile radius of the Monroe Auto Superfund

site, but we have never been contacted by Monroe, EPA, or ADPC&E. We would

appreciate receiving any previous correspondence as well as any future correspondence.

Also, we would like to request our water be tested as quickly as possible.

Response #17

Based on provisions set forth in this Record of Decision, all residential wells that are

located within one half mile radius of the site will be periodically tested.

71
All future correspondence will be mailed to persons who are on the site's mailing list.

Previous information on the site can be accessed at Northeast Arkansas Regional Library

in Paragould, Arkansas.

Comment #18

We feel that the proposed solution to this problem is unsatisfactory because it leaves the

Monroe Auto Pit intact.

s

Response ffU

Analytical data from testing of leachate produced by the toxicity characteristic leaching

procedure (TCLP) show very low leachability of the contaminants in the sludge.

Therefore, the sludge/soil deposits in the pit pose a low long-term threat. This low longterm threat can be reliably contained by the engineering controls, namely, constn""tion ur

a french drain and placement of an impermeable cap over the sludge deposit area.

ADPC&E is committed to safeguarding human health and the environment against any

possible adverse effect from this site and believes that the selected remedy will fully

satisfy the above objective.

Comment #19

As long as the fence and the signs remain our property we be devalued. Please see

Response #2.

Response ffl9

ADPC&E agrees that the fence and signs could adversely impact the property values.

Despite this acknowledgment, site restriction will remain as part of the selected remedy.

Comment #20

We request an extension to the August 17 deadline, since we have not previously been

aware of the seriousness of this problem. We need more time to study the proposals.

Response #20

A two month extension to the August 17 deadline was granted. Please see Response ff6.

Comment #21

I'm really disappointed that no action is really being taken to solve the drinking water

problem. Real or imaginary, everybody in the area feels like we've got problems with

the water. Most everybody is drinking bottled water. We are really concerned about the

health of our children and our families.

72
Response ff21

ADPC&E disagrees. The residential wells within a half mile radius of the site will

continue to be analyzed to ensure that residential wells meet the drinking water standards.

In addition, in the unlikely event that monitoring indicates a degradation of residential

water well quality due to site contaminants, proper contingency actions will be

implemented.

Analytical results from residential wells near the site meet the safe drinking water

standards. Therefore, consumption of water from these wells should not cause any

adverse health effect to children or adults.

Comment #22

I believe that failure to remove or solidify that sludge is going to end up being a stigma

on the community and remain to be a drain on property values in the area for ages.

Please see Response ff2.

Response ff22

The impact of an alternative on the property values is not one of the criteria which would

directly influence selection of a remedial alternative. The State agrees with the

respondent that the removal alternative would help to improve the property values in this

area.

The solidification/stabilization alternative would enlarge the size of the landfill and it is

unlikely that it would impact the property values any differently than the selected remedy.

As to why a removal alternative was not chosen, please refer to comment ^13.

Comment ff23

This is an earthquake area. It has a very destabilizing effect on some of these drains and

caps and so forth and I'm real concerned that really hasn't been taken into consideration

carefully enough.

Response ff23

The Arkansas Hazardous Waste Management, Regulation 23, Section 264.18(a) states: (a)

Seismic consideration. (1) portions of new facilities where treatment, storage, or disposal

of hazardous waste will be conducted must not be located within 61 meters (200 feet) of

a fault which had displacement in Holocene time.

Such a fault does not exist within the specified area of the site. Therefore, seismic

considerations are not applicable to this site.

73
Comment ff24

The idea of draining a french drain into the creek just sounds ridiculous to me. I don't

see how the contaminants in that french drain is not just going to get into the creek and

be a bigger hazard than we have right now.

Response ff24

As an added precaution, a cap and french drain will be placed around the sludge pit.

The cap will prevent infiltration of rainfall and run off. The french drain will direct the

perched water away from the sludge. The perched water will be intercepted before it

comes in contact with the sludge and will therefore be "clean" when it is discharged to

the stream.

Comment #25

At Times Beach, Missouri, because of throwing out just plain old oil, they bought the

town out. The sludge in Monroe Auto Pit came from paint booths, contaminants from

there, plus some other waste water. Waste water means it came from wherever Monroe

had grinding. And being a machinist and everything, you don't know what materials you

have in alloys. Whatever Monroe does to this property is not going to eliminate

contamination in the future. The health effect of contaminants are not fully known. At

one time the Ocean Spray Cranberry Sauce was considered safe to eat, later it became

known that it could cause cancer. So, the number one concern is health.

Response ff25

The sludge at the pit contains a number of organic and inorganic contaminants. The

remedial investigation report provides information to the extent and amount of these

contaminants. At Times Beach the oil contained some of the most toxic substances

known to humans (dioxin). Moreover, because it was spread on roads and streets to

suppress dust, the public was in direct contact with these contaminants. At Monroe Auto

Pit, however, the public has not been directly exposed to the contaminants. Addition of

the cap and French drain, as it is specified under the preferred remedy, will isolate the

sludge pit. This isolation will eliminate any possible mingling of contaminants in the

sludge with other media (soil, water, and air). Protection of the public health and the

environment throughout the state of Arkansas is also a concern of ADPC&E. ADPC&E

believes that the selected remedy will provide adequate protection against any adverse

health effect which may be caused by the site.

Comment ff26

We are in the earthquake area and the New Madrid Fault is not too far away from

Greene County. So whatever Monroe does to this property out there is not going to

eliminate contamination in the future for that.

74
Response #26

See response #23.

Comment #27

It makes a difference if you are in an area that has been contaminated with a contaminant

that was just freely thrown out because it was accounting by a big manufacturing firm

that employs a lot of people. We don't like things thrown out and not taken care of.

What are we going to do about it? According to this report, we're going to let it drain

off into our water naturally.

Response #27

The contaminants present in the on site monitoring wells are in the upper Wilcox aquifer.

These contaminants were originally in the sludge that was deposited in the pit by Monroe

Auto Plant in Paragould. Over time the liquids in the sludge leached out and traveled

down to the water table and into the water of the upper Wilcox aquifer. The monitoring

wells on the site and those surrounding the site have been used to monitor the movement

of contaminants in the ground water. From these analyses, the contamination is confined

to the Monroe property at this time.

Using this data and information about how water moves in the aquifer, models of the

expected movement of contaminants and how the contaminants change over time were

developed. Using these models, contaminants are expected to degrade (change) and the

levels lower naturally over time before they become a threat to residential wells.

Comment #28

What else can you do, other than try to lift every bit of it (sludge) out of there (pit) and

carry it off?

Response #28

Please see response #18.

Comment #29

What is going to happen to our property value in this area? What type compensation are

the land owners going to get out of this or their property in the future because you have

none.

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Response #29

Contaminants released to media outside the site boundary are below the federal and state

regulatory action levels.

CERCLA does not authorize compensation foor a reduction in property value, based on

stigma of its nearness to a Superfund site. Please see response ft2.

Comment ff3Q

Now, most streams that you'll see has got clear water, you know, but now I've got two

or three places that stuff runs out and it's a milky looking and oily looking stuff that's

coming out of there. That's not clear water. I don't know what it is and hadn't nobody

told me anything and I hadn't really knew who exactly to ask, but I just kind of Like to

wonder what it is, how dangerous it is, and if it could be cleaned up. What could be

done to it?

Response ff30

Surface water studies on the site show that any contamination that could be carried by run

off would enter the intermittent creek southwest of the site and that the level of

contamination found in creek sediment decreases rapidly away from the site. Given this

information, the site is probably not causing the cloudy or oily effects in your streams.

Comment ff31

...this pamphlet it says "The majority of the liquids migrated into the ground water

during the 1970's when the landfill was active and is believed to be a major source of

ground water contamination at this site. The primary source of ground water

contamination no longer exists at the site." Well, my next question is, where did this

contamination go to? If it's not on the site, it looks to me like it's had to went

somewhere. It's had to drain down, and that's why I think it's probably on this place of

mine and maybe on surrounding areas.

Response #31

Presently, the contamination is in the ground water. The contaminants that were

leachable from the sludge have left the sludge and are now in the ground water. The

contaminated ground water is still within the site boundaries as indicated by the sample

results from the monitoring wells. Monitoring wells have been placed around the site

perimeter and in all three aquifers to monitor the movement of the contamination plume.

This monitoring will continue to keep us up to date on how degradation of the

contaminants is progressing.

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Comment #32

I have several concerns. First is surface water contamination and I have asked for testing

and whatever and haven't had any results or any satisfaction about what studies have been

made about surface water contamination and any results of that. And I have, I guess the

major creek that runs north of the dump site and it drains quite a bit of acreage west and

some south toward the dump site through my property.

Response #32

From looking at a topographic map, the creek that you mentioned drains an area north of

the site. The topography at the site is such that surface run off travels to the southwest

and south from the sludge area. The site drainage area and the drainage area of your

stream are separate and do not run together.

Comment #33

...What do you plan to do in the Remedial Action Plan that may involve extraction of

any water from the site and where you propose to put that.

Response #33

The selected remedy would involve a french drain that would capture perched water and

release it to the intermittent stream that flows southwest of the site. If a pump and treat

method is implemented for the ground water remediation, the water would be treated and

put back into the aquifer by wells to enhance the remediation.

Comment #34

...I feel like we need more time to evaluate what we're looking at and what the solutions

are. ...And I don't know what's available through EPA, if the consultant route is still

available to us.

Response #34

A two month extension of the public comment period was granted. By "consultant route",

if it means a TAG grant, such a grant is not available at this stage of the remediation.

Comment #35

Monroe has not been very responsive to the property owners in this area. I've seen no

studies to evaluate property values. All we can see is property values being devalued.

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Response #35

The Superfund remediation process does not authorize studies on property values. The

impact of the superfund remediation on the property values is not controlled by the State.

Please see Response ff2.

Comment ff36

...after looking at that (report) it looks like something around thirteen out of twenty-six

wells have shown signs of the contaminants that are on the site are now in the ground

water in the surrounding area. We were originally told that the Gaim well was the only

well that was contaminated.

Response ft36

The figure you are referring to shows the concentrations of organics and inorganics

(metals) that were found in the residential samples taken in April 1992. Many metals are

naturally occurring. The organic values are quantified as estimated values, which means

that the actual values could be lower. The contamination in the Gann well showed levels

that were 10 to 100 times greater. The monitoring wells that were placed adjacent to the

Gann well continue to show levels of the same contaminants, but at lower levels. The

contamination is confined to the upper Wilcox aquifer. The Gann well remains the only

residential well that has shown signs of contamination.

Comment ^37

The solution, as I mentioned, is unacceptable for fair people and we'd like to ask that we

have additional time to study this report, to get some technical expertise to explain to us,

collectively and individually, what our, the impact of this site has on us.

Response ff37

The selected remedy if designed and implemented properly will provide protection of the

human health and the environment. A two month extension of the public comment period

was granted.

Comment ff3S

People won't fish in my pond that I built. They won't eat the fish.

Response ff3S

Surface water drainage into your pond does not appear to come from the site. Village

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Creek is the surface water connection from the site to your pond; however, your pond

drains into Village Creek. No contamination from the site should be in your pond.

Comment #39

So I think we need a little more time to investigate this because this stuff is coming out

through everybody's water, I know it is, and I think there should be more wells checked

to see how much contamination there actually is.

Response #39

Sampling to date indicates that trace amounts of contaminants occur in some wells. The

distribution of contaminants does not indicate if the contamination is from the site or not

from the sites. The highest concentrations of contaminants of concern occur on the site.

In general, contaminants will move from areas of high concentration to areas of lower

concentration. The highest readings will be near the source of contamination and

decrease away from the source of contamination. Monitoring wells have been placed

around the border of the site to monitor any increases in contaminant levels. Continued

monitoring will be a part of the remediation plan.

Comment #40

...I object to leaving this pit to be a continuing problem for no telling how long.

Eliminate the problem. Eliminate the problem. Cost should not be even considered.

Monroe put it there, Monroe can remove it.

Response #40

The State is required to use nine criteria to evaluate alternatives for addressing a

Super-fund site. Since cost is one of the nine criteria, it cannot be ignored as the

respondent has suggested. The rationale for not choosing a removal option is explained in

response to comment #13. Also, please note that even a complete removal of the sludge

will not eliminate the problems with the ground water immediately.

Comment #41

I'd like to know why I haven't received no paperwork on this stuff?

Response #41

The mailing list is compiled from attendance sheets at previous meetings, those persons

submitting comments, and those persons who have requested to be placed on the mailing

list either through Monroe, the State Department of Pollution Control and Ecology, or

through EPA. As a result of attending this meeting your name will be placed on the

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mailing list. All of the public records arc accessible at the Northeast Arkansas Regional

Library in Paragould, Arkansas or in our central files in Little Rock, Arkansas.

Comment ^42

...there's one thing I haven't heard mentioned tonight is people that is getting sick from

the well water. People that take a shower break out in rashes. They get fumes that

makes them sick. And that is getting farther away from that all the time, and you're not

going to make anybody in here believe it's not coming out of those wells, because,it is.

Response #42

The only recorded incident of rashes from water use or fumes from the water are related

to the Gann well. As stated earlier, the lab results from private well sampling indicate

that the water is safe for drinking and other domestic uses.

Comment ff43

...my concern is, I have two small children and I want to know if that water out there's

going to kill them like it did the frogs?

Response ff43

The frogs you saw at the site were in the decontamination tank. The chemicals used to

decontaminate the drilling equipment would be toxic to frogs. The decontamination water

is siphoned from this temporary tank into a holding tank at the site for proper disposal.

Comment ^44

They (residents) have a fear of the unknown. They have a real concern about the health,

not only acute but also chronic.

Response ff44

The state understands the concerns of the local residents. The protection of human health

is the top priority of the State.

Comment ff45

And another thing surfaces, maybe not as strong as the rest of it but certainly a

diminution in their property value over a period of time.

Response ff45

The impact of a Super-fund site on property values is not controlled by the State or the

EPA. Please see Response ftl.

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Comment #46

They (the residents) have asked that I ask you folks to give them an extension of time on

the comment period to consider either, hopefully, under the TAG program, hiring a

consultant ...to come in and help them through this process.

Response ff46

A two months extension period was granted. The TAG program is not available at this

stage of the remediation process. Please see Response ff6.

Comment From Monroe Auto Equipment

Monroe believes that the proposed plan will adequately protect human health and the

environment. Monroe agrees that it is appropriate to leave the contaminated sludge/soil in

place at the site. The installation of a cap will minimize infiltration and erosion while

the French drain will isolate the contaminated soil/sludge from the perched ground water.

Periodic maintenance of the cap will assure the long-term integrity of the cap. Deed

restrictions and site access restrictions will further limit any potential contact with

contaminated media. Because the primary source of ground water contamination no

longer exists at the site, the concentrations of contaminants in the ground water will

decrease through natural attenuation and degradation. Ground water use restrictions on

the site and periodic monitoring of residential wells and monitoring wells will further

protect public health. Although off-site migration of contaminants is not expected, the

periodic monitoring would provide notice of migrations should it occur.

Response

The State agrees.

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