Superfund Record of Decision Ohio River Park Site OU 3 Neville Island PA


                                    EPA/ROD/R03-98/046
                                    1998
EPA Superfund
     Record of Decision:
     OHIO RIVER PARK
     EPA ID: PAD980508816
     OU03
     NEVILLE ISLAND, PA
     09/17/1998

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EPA 541-R98-046


SUPERFUND PROGRAM
RECORD OF DECISION

Ohio River Park Site

Operable Unit Three
Neville Island
Allegheny County, Pennsylvania

                                      September 1998
                                      TABLE OF CONTENTS

 PART I - DECLARATION	  1

 I.    SITE NAME AND LOCATION 	  1

 II.   STATEMENT OF BASIS AND PURPOSE	  1

 III. ASSESSMENT OF THE SITE	  1

 IV.   DESCRIPTION OF THE SELECTED REMEDY	  1

 V.    STATUTORY DETERMINATIONS	  2

 PART II - DECISION SUMMARY	  3

 I.    SITE NAME, LOCATION, AND DESCRIPTION	  3

 II.   SCOPE AND ROLE OF THE RESPONSE ACTION 	  5

 III.  SITE HISTORY AND ENFORCEMENT ACTIVITIES	  5

 IV.    HIGHLIGHTS OF COMMUNITY PARTICIPATION	  9

 V.    SUMMARY OFSITE CHARACTERISTICS	  9
        A.  Surface Features 	  9
        B.  Geology	  11
        C.  Hydrology 	  11
        D.  Climate	  12

 VI.   NATURE AND EXTENT OF CONTAMINATION	  12
        A.  Groundwater Contamination in RI Report	  12
        B.  Groundwater Contamination in Intrinsic Remediation Demonstration Study	  18
              1. Aguifer Characteristics 	  18
              2. Extent of the Plume	  19
              3. Natural Attenuation of the Plume  	  23

 VII. SUMMARY OF SITE RISKS	  32
        A.  Human Health Risks	  32
              1. Data Collection and Evaluation	  34
              2. Exposure Assessment	  36

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             3 . Toxicity Assessment	 38
             4. Human Health Effects	 39
             5. Risk Characterization  	 47
       B.  Ecological Risk Assessment	 48

VIII.  DESCRIPTION OF ALTERNATIVES 	 49

VIII.  COMPARATIVE EVALUATION OF ALTERNATIVES  	 52
       A.  Overall Protection of Human Health and the Environment	 53
       B.  Compliance with Applicable or Relevant and Appropriate Requirements
  ( "ARARS" )	 53
       C.  Reduction of Toxicity, Mobility, or Volume through Treatment	 55
       D.  Implementability	 55
       E.  Short-Term Effectiveness	 55
       F.  Long-term Effectiveness and Permanence	 56
       G.  Cost	 56
       H.  State Acceptance 	 57
       I.  Community Acceptance	 57

IX.  SELECTED REMEDY AND PERFORMANCE STANDARDS	 57
       A.  Natural Attenuation Requirements	 58
       B.  Monitoring Requirements 	 58
       C.  Institutional Controls 	 59

X.   STATUTORY DETERMINATIONS 	 59
       A.  Overall Protection of Human Health and the Environment	 59
       B.  Compliance with ARARS	 59
       C.  Cost Effectiveness	 59
       D.  Utilization of Permanent Solutions and Alternative Treatment  (or Resource
           Recovery) Technologies to the Maximum Extent Practicable	 60
       E.  Preference for Treatment as a Principal Element	 60

XII.   DOCUMENTATION OF SIGNIFICANT CHANGES 	 60

PART III - RESPONSIVENESS SUMMARY	 61

I. BACKGROUND	 61

II. MAJOR ISSUES AND CONCERNS	 62
       A.  OU-1 Remedial Action  	 62
       B.  Natural Attenuation 	 63
       C.  Risk Evaluation	 64
       D.  Groundwater Monitoring Program  	 65
       E.  Decision Process 	 66
       F.  Property Acquisition  	 67
       G.  Positive Responses	 67

III. TECHNICAL AND LEGAL ISSUES	 67
       A.  General Groundwater Monitoring	 68
       B.  Groundwater Monitoring Parameters  	 68

       C.  Intrinsic Remediation Demonstration Study	 71
       D.  Other	 72

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                                         TABLES

Table 1 - Volatile Organic Compounds in Groundwater                                       15
Table 2 - Semi-Volatile Organic Compounds in Groundwater                                  16
Table 3 - Metals in Groundwater                                                           17
Table 4 - Comparison of VOC Concentrations in RI and OU3 Study                            24
Table 5 - Comparison of SVOC Concentrations in RI and OU3 Study                           25
Table 6 - Reasonable Maximum Exposure Point Concentrations                                34
Table 7 - Exposure Assessment Factors                                                     37
Table 8 - Slope Factors and Reference Doses                                               40
Table 9 - Human Health Risks at the Site                                                  49
Table 10 - Estimated Cost of Alternatives                                                 57

                                         FIGURES

Figure 1 - Site Location                                                                   4
Figure 2 - Location of Buried Wastes                                                       6
Figure 3 - Types of Waste Disposed by Location                                             7
Figure 4 - Site Features                                                                  10
Figure 5A - Groundwater Monitoring Well Locations                                         13
Figure 5B - Back Channel Sampling Locations                                               20
Figure 6 - Distribution of Benzene in Mid-Depth Groundwater                               21
Figure 7 - Distribution of Benzene in Deep Groundwater                                    22
Figure 8 - 1993 Distribution of Benzene in Groundwater                                    26
Figure 9 - 1987 Distribution of Benzene in Groundwater                                    27
Figure 10 - 1984 Distribution of Benzene in Groundwater                                   29
Figure 11 - 1981 Distribution of Benzene in Groundwater                                   29
Figure 12 - Relationship of Historic Benzene Detection in Groundwater,  1981-1996          30
Figure 13 - Current and Historical Distribution 2,4,6-Trichlorophenol in Groundwater      31
Figure 14 - Distribution of Dissolved Oxygen in Shallow Groundwater                       33

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RECORD OF DECISION

OHIO RIVER PARK SUPERFUND SITE

DECLARATION

I. SITE NAME AND LOCATION

Ohio River Park Superfund Site
Neville Township
Allegheny County, Pennsylvania

II. STATEMENT OF BASIS AND PURPOSE

This Record of Decision (ROD) presents the selected remedial action plan for the Ohio River
Park Superfund Site (the "Site") in Allegheny County, Pennsylvania which was chosen in
accordance with the Comprehensive Environmental Response, Compensation, and Liability Act of
1980 ("CERCLA"), as amended by the Superfund Amendments and Reauthorization act of 1986, 42
U.S.C. ° 9601 ("SARA"), and to the extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan ("NCP"),40 C.F.R. Part 300. This decision is based upon and
documented in the contents of the Administrative Record. The attached index identifies the items
which comprise the Administrative Record.

The Commonwealth of Pennsylvania concurs with the selected remedy.

III. ASSESSMENT OF THE SITE

Pursuant to my duly delegated authority, I hereby determine, pursuant to Section 106 of
CERCLA, 42 U.S.C. ° 9606, that actual or threatened releases of hazardous substances from this
Site, as specified in Section VII, Summary of Site Risks, in the ROD, if not addressed by
implementing the response action selected, may present an imminent and substantial endangerment
to the public health, welfare, or the environment.

IV. DESCRIPTION OF THE SELECTED REMEDY

The remedial action plan in this document is presented as the permanent remedy for
controlling the groundwater at the Site. This remedy is comprised of the following components:

Monitoring of natural attenuation processes to measure changes in contaminant
concentrations in groundwater plume at the Site until the cleanup levels are achieved.

D Deed restriction preventing residential use of groundwater at the Site.

V. STATUTORY DETERMINATIONS

Pursuant to duly delegated authority, I hereby determine that the selected remedy is
protective of human health and the environment, complies with Federal and State reguirements
that legally are applicable or relevant and appropriate to the remedial action, and is
cost-effective. The selected remedy utilizes permanent solutions and alternative treatment
technologies to the maximum extent practicable, and satisfies the statutory preference for
remedial actions in which treatment that reduces toxicity, mobility, or volume is a principal
element.

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

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levels, a review will be conducted within five (5) years after the commencement of the remedial
action to ensure that human health and the envirorunent continue to be adequately protected by
the remedy.

RECORD OF DECISION
OHIO RIVER PARK SITE

PART II - DECISION SUMMARY

I. SITE NAME, LOCATION, AND DESCRIPTION

The Ohio River Park Site ("Site") includes appromimately 32 acres on the western end of
Neville Island, approximately 10 miles downstream of the City of Pittsburgh (see Figure 1). The
Main Channel of the Ohio River borders the 32-acre area to the north and the Back Channel of the
Ohio River borders it to the south. The Site is accessible from the mainland via the new
Coraopolis Bridge, linking the Town of Coraopolis with Neville Island. The Ohio River Park
Site has been identified in some documents, mostly preceding EPA involvement, as Neville Island.
This Record of Decision will refer to the Site as the "Ohio River Park Site" or "the Site."

The Ohio River Park Site is defined as all areas found presently, or in the future, to be
impacted by contamination that resulted from waste disposal operations previously conducted at
this 32-acre area on Neville Island. This ROD addresses the potential impact and fate of a plume
of contaminated groundwater which originates at the Site and enters the Back Channel of the
Ohio River and the impact of this plume on surface water and sediment.

Land use on Neville Wand is generally industrial/commercial, although some residential
areas are present. The middle section of the island east of the Site and west of highway 1-79 is
mostly residential and commercial while the eastern end of the island is heavily industrialized.
Most of Neville Island's 930 residents live in the area between the Coraopolis Bridge and
highway 1-79. The nearest residence is located approximately 450 feet from the Site.
According to the 1990 census, the population within an approximately four-mile radius of the
Site is 18,058. The eastern end of the island, approximately two miles east of the Site, is
occupied by petrochemical facilities, coal coking facilities and abandoned steel facilities.

The Site consists primarily of open fields surrounded by trees and underbrush that form a
perimeter adjacent to the river. The major structures on the Site in the Spring of 1998 included
a maintenance building, asphalt-covered parking lots, roadways and walkways, concrete
foundations, a pipeline, underground utilities, and an abandoned oil well derrick. These
structures were demolished and replaced with the foundations for the Island Sports Center during
the Spring/Summer of 1999.

The Site is located almost completely within the 100-year floodplain but above the
ordinary high water elevation.

II. SCOPE AND ROLE OF THE RESPONSE ACTION

EPA has divided the Site into three areas or Operable Units. The first operable unit
includes approximately 31 acres owned by the Neville Land Company ("NLC"), and located

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north of Grand Avenue and west of the Coraopolis Bridge. This operable unit is referred to as
Operable Unit 1 ("OU-1") of the Site. Buried waste and soil contamination is present in this
portion of the Site. EPA determined in a Record of Decision issued on September 30, 1996, that
the required remedial action for OU-1 includes capping, surface water runoff controls,
monitoring, and institutional controls.

The second operable unit ("OU-2") is an approximately one-acre area on the southeast comer
of the Site that includes an approach roadway for the Coraopolis Bridge and a meadow along the
Back Channel of the Ohio River. This area is also referred to as "the Bridge Portion of the
Site" and is owned by Allegheny County. EPA determined that no cleanup action is required for
OU-2 in a Record of Decision signed on March 31, 1993.

Operable Unit 3 ("OU-3") of the Site, the subject of this Record of Decision, addresses
groundwater contamination for the entire Site. EPA initially planned to address these areas of
concern as part of OU-1. After issuing the Proposed Plan for OU-1 and receiving public comments
on the Agency's cleanup recommendations, EPA limited the scope of OU-1 to remediation of
contamination in the buried waste and soil at the Site. Additional data were needed to select a
final remedy to address contamination in the groundwater, surface water, and sediment at the
Site. This Record of Decision identifies the required remedial action to address groundwater,
surface water, and sediment contamination at the Site based on the additional data collected and
information previously collected at the Site.

III. SITE HISTORY AND ENFORCEMENT ACTIVITIES

Prior to the 1940's, the predominant land use at the Site was agricultural. Beginning in the
Mid-1930's until the mid-1950's, a portion of the Site was used for municipal landfill
operations including the disposal of domestic trash and construction debris. Industrial waste
disposal activities were conducted at the Site from 1952 through the 1960's.

Available information indicates that Pittsburgh Coke and Chemical Company ("PC&C")
disposed of much of the industrial waste at the Site. PC&C began production of coke and pig iron
on the eastern end of the island in 1929, operated a cement products plant during the 1930's,
and produced coal coking by-products during the 1940's. Between 1949 and 1955, PC&C's
agricultural Chemicals Division manufactured pesticides. Two methods of waste disposal were
used by PC&C at the Site: wet wastes were placed into trenches and dry wastes were piled on the
surface. Fifty-four trenches have been identified as being used for disposal of tar acid, tar
decanter, and occasionally agricultural chemical wastes. Figures 2 and 3 show theapproximate
disposal locations of various wastes at the Site. PC&C operations ceased in 1965-66. PC&C
merged into Wilmington Securities, Inc., the parent corporation of the Neville Land Company
("NLC").

In 1977, Neville Land Company donated the Site area to Allegheny County. Allegheny County
began construction of a park on the Site in 1977 and completed the construction in 1979, The
park was never opened to the public, however, and was subsequently dismantled. During the course
of the work, approximately 13,000 cubic yards of various wastes were discovered at the Site.
Mile most of these materials were excavated and removed from the Site, some materials were
reburied. After this discovery, Allegheny County transferred the title to the land back to NLC.
A small portion of the property, which was acquired from another source to complete the park,
was not transferred to NLC. Subsequently, by deed dated May 12, 1997, Allegheny County
transferred this property to NLC.

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    Based on information and data collected from 1977 through 1989 by Allegheny County, EPA,
NLC, and the Pennsylvania Department of Environmental Resources  (("PADER"), now the Pennsylvania
Department of Environmental Protection  ("PADEP")), EPA proposed to include the Site on the
National Priorities List of Superfund sites on October 16, 1999. The analytical data collected
were used to evaluate the relative hazards posed by the Site using EPA' s Hazard Ranking System
("HRS"). EPA uses the HRS to calculate a score for hazardous waste sites based upon the presence
of potential and observed hazards. If the final HRS score exceeds 28.5, the Site may be placed
on the National Priorities List, making it eligible to receive Superfund monies for remedial
cleanup. This Site scored 42.24, and was placed on the list on August 30, 1990.

    In October 1991, EPA and NLC, the owner of the Site, entered into an Administrative Order on
Consent in which the NLC agreed to conduct a Remedial Investigation/Feasibility Study of the
Site with EPA and State oversight. Field sampling was performed in 1992 and 1993, and the
Remedial Investigation  ("RI") Report for the Site was approved by EPA in June 1994. The
Ecological Risk Assessment was completed in November 1994 and the Baseline Human Health Risk
Assessment was completed in January 1995. Based on these documents, NLC submitted a Feasibility
Study  ("FS") in April 1995 describing the remedial action objectives and comparing cleanup
alternatives for the Site. EPA issued the Record of Decision reguiring remedial action for OU-1
on September 30, 1996. Through a Consent Decree entered on December 31, 1997, NLC and its
parent, Wilmington Securities, Inc., agreed to Implement the remedy, which includes, capping,
surface water runoff controls, monitoring, and institutional controls.

    During the Spring of 1996, NLC proposed to submit additional data showing that reliance on
natural attenuation processes would be an appropriate measure to address contaminants in the
groundwater plume at the Site. EPA agreed to allow NLC to collect and submit the additional
data as part of an intrinsic remediation demonstration study. Based on this study, NLC evaluated
the results of groundwater sampling collected on and off the Site, including locations beneath
the Back Channel and the sentinel well located across the Back Channel. The evaluation projected
the fate and transport of contaminants in the groundwater plume by modeling of the biological,
physical, and chemical mechanisms that can naturally lead to a reduction of the total mass of
contaminants dissolved in groundwater.

    IV. HIGHLIGHTS OF COMMUNITY PARTICIPATION

    The documents which EPA used to develop, evaluate, and select a remedy for OU-3 of the Site
are maintained at the Coraopolis Memorial Library, State and School Streets, Coraopolis, PA, and
at the EPA Region 3, Philadelphia Office.

    The Proposed Plan and supporting documents for OU-3 of the Site were released to the public
for comment through a notice of availability published in the Tribune Review and Pittsburgh
Post-Gazette on February 25, 1998. The 30-day public comment period ended on March 26, 1998.

    EPA conducted a briefing for the Board of County Supervisors and a public meeting on March
17, 1998. EPA answered guestions about the Site and the remedial alternatives under
consideration during the public meeting. Approximately 100 people attended, including
residents from the local community, local government officials, and news media representatives.
A summary of comments received during the public comment period and EPA' s responses are
contained in Part III of this document.

    V. SUMMARY OF SITE CHARACTERISTICS

    A. Surface Features

    Aerial photography and Remedial Investigation sampling revealed locations of dumping areas

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and the types of wastes that were disposed at the Site (see Figures 2 and 3). Two methods of
waste disposal were used: wet wastes were placed into 54 trenches and dry wastes were piled on
the surface and/or incinerated at the Site. Most of the manufacturing and municipal wastes were
disposed at the south-central portion of the Site beneath the currently existing parking lot,
in the meadows, and along the Back Channel river banks. Steep river ledges at the western part
of the Site were created by piles of foundry sand and demolition debris. From the mid-1960's
until 1977, the Site was an abandoned landfill, Between 1977 and 1979, the Site was altered
during the construction and then dismantling of a recreational park. Approximately 13,000 cubic
yards of waste materials were excavated and the area was leveled and covered with soil. Natural
revegetation occurred at the Site resulting in a cover of grass, shrubs and sporadic trees.
Currently, the surface of the Site is being disturbed to implement the OU-1 remedy.

The Site is encircled by a metal fence with a gate at the entrance on Grand Avenue. An
asphalt entry road (see Figure 4) leads to a portion of the Site where NLC started construction
of the Island Sports Center in the Spring of 1998. The area was not used for waste disposal. The
surfaces of the road, parking lots, and walking paths have not been maintained and are cracked
in many places with several visible depressions and holes. The road goes further to a small
parking lot where a former park administration building existed. This building was demolished in
May 1998. NLC plans to build most of the Island Sports Center on the area between this parking
lot and the Ohio River. The trees along the river banks have not been cleared during
construction to protect steep slopes against erosion. The central portion of the Site includes
open meadows and fragments of an old asphalt biking path. Along the river banks and at the
western end of the island, trees and brush become denser and woods gradually replace the meadow.
An abandoned oil well derrick, formerly located along the Ohio River bank in the north-central
part of the Site, has been dismantled. The western portion of the Site, including the steep
terraces on the river bank, is densely covered with trees.

B. Geology

The Ohio River Park Site flies within the Allegheny Plateau section of the Appalachian
Plateau Physiographic Province. The Allegheny Plateau is characterized by gently folded,
parallel, northeast-southwest trending folds. At the Site, the bedrock is identified as the
Glenshaw and Casselman Formations of the Pennsylvanian Age Connemaugh Group. These formations
are primarily composed of interbedded shale, siltstone and sandstone with thin beds of limestone
and coal. The Glenshaw Formation, which is the lower member of the Connemaugh Group, and the
Casselman Formation, which is the upper member of the Connemaugh Group, are separated by the
Ames Limestone in Western Pennsylvania.

Like most stream valleys in Western Pennsylvania, the Ohio River consists of unconsolidated
sediments overlying bedrock. Neville Island is a portion of a dissected river terrace that was
deposited by the ancestral Ohio River. The unconsolidated sediments at the Site are
approximately 60 feet thick and in the Ohio River Channel 20 feet thick. At the Site, the upper
portion of the unconsolidated sediments consists of approximately 25 feet of fill, and
Quarternary fluvial deposits of clay, silt and sand. The lower 35 feet consists of glaciofluvial
deposits of sand and gravel with minor amounts of silt and clay that were deposited from glacial
meltwaters during the Pleistocene interglacial stages. The top of bedrock at the Site appears to
gently slope toward the south-southwest.

Fill is found throughout the Site, with the exception of the eastern boundary where it is
absent. Former trenches in the south-central portion of the Site extend to a maximum depth of
12 feet. Foundry sand disposed in the western part of the Site is up to 27 feet deep.

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C. Hydrology

The Site is bounded by the Back Channel of the Ohio River to the south and by the Main
Channel of the Ohio River to the north. The flow rate in the river has varied from 108,000 cubic
feet per minute (measured at Sewickley in 1957) to 4,440,000 cubic feet per minute (measured
at Sewickley in 1935). Since approximately 90 percent of the flow occurs in the Main Channel,
the minimum and maximum flow in the Back Channel are approximately 10,800 and 44,400
cubic feet per minute, respectively. The Ohio River is navigable and chemicals, coal, and coke
are routinely transported on the river by barges.

The Site terrace deposits, consisting of sand, gravel, and sediments, constitute an
unconfined surficial aguifer that extends beneath the Ohio River and is interconnected to the
river. Bedrock, consisting of shale, siltstone and fine-grained, micaceous sandstone, underlies
these sediments. The groundwater in the sand/gravel aguifer beneath the Site discharges
primarily to the Main and Back Channels of the Ohio River. However, this aguifer interconnects
with groundwater beneath the river and on the shores. Groundwater is used as a source of
drinking water by several municipalities which flank the Ohio River. The nearest one is the
municipality of Coraopolis. The Coraopolis well field is located approximately 750 feet
southwest from the western boundary of the Site, along the Back Channel. The well field
consists of seven wells that produce an average of 127 cubic feet per minute from the sand and
gravel aguifer.

D. Climate

The climate of Megheny County is classified as humid continental. The annual average
precipitation is 37 inches, and it is evenly distributed throughout the year. The mean annual
temperature is approximately 50 degrees Fahrenheit.

VI. NATURE AND EXTENT OF CONTAMINATION

The primary objective of the Remedial Investigation was to characterize the nature and
extent of hazardous substances present at the Ohio River Park Site. As part of this effort, the
RI identified and evaluated Site-related contaminants, their potential migration routes, and
exposure pathways for human and ecological receptors. The results of groundwater presented in
the RI indicated that natural attenuation processes could play an important role in changing the
distribution and concentration of Site-related contaminants. To provide more information on
natural attenuation, the intrinsic remediation demonstration study was completed using
additional methods of investigation including water level monitoring, a pumping test, computer
models of water flow, evaluation of geochemical indicators of natural attenuation, and plume
evaluation. The predicted configuration of the plume was further modified by the data collected
from additional sampling beneath the Ohio River Back Channel.

A. Groundwater Contamination in RI Report

During the RI, 17 new groundwater monitoring wells were installed at the Site to
complement 19 existing on-site monitoring wells (see Figure 5A). One well from the Coraopolis
Municipal Well Field was also sampled during the RI. The analytical data collected from these
wells suggest benzene and phenolics are contaminants of concern in groundwater at the Site.

Pesticides and herbicides are not of concern based on the analytical data. Five pesticides
were detected at five groundwater sampling locations, however, the concentrations detected were
less than 0.02 parts per billion ("ppb"), This level is an order of magnitude (i.e., ten times)
lower than the Safe Drinking Water Act Maximum Contaminant Level ("MCL") for the pesticides
detected. Three herbicides were detected at the Site, however, only two samples detected an

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herbicide (2,4-D) at a concentration exceeding its MCL (70 ppb).

The inorganic data indicate that several metals were detected at levels of concern. Cadmium
concentrations were greater than its MCL (5 ppb) at three monitoring well locations. Antimony
was sporadically detected at concentrations greater than its MCL (6 ppb) at six monitoring
wells. Antimony was not detected in the same monitoring wells during both groundwater sampling
rounds and antimony was also detected in the laboratory blank samples, therefore, antimony was
not considered a constituent of interest. Nickel was detected at concentrations greater than its
MCL (100 ppb) at four monitoring well locations during both groundwater sampling rounds. Three
of these monitoring well locations were in the areas of foundry sand disposal near the western
end of the island.

Benzene is the volatile organic compound ("VOC") considered to be the primary contaminant of
concern at the Site. Benzene was detected at concentrations ranging from 3 to 50,000 ppb in 22
of 36 samples analyzed. Benzene was detected primarily in 14 monitoring wells located in the
southcentral portion of the Site.

Although an MCL has not been established for the phenolics, concentrations detected in the
groundwater at the Site (>10 parts per million ("ppm")) indicate former disposal activities
have impacted the groundwater guality in the south central portion of the Site. Phenolic
compounds were detected at high concentrations near the southern portion of the large parking
lot. The highest concentration of 2,4,6-Trichlorophenol was 210,000 ppb. Trace guantities of
phenolics (generally <10 ppb) were detected in three of the five Back Channel monitoring wells.
The high levels of 2,4,6-trichlorophenol suggest source material (ie., dense nonageous phase
liguid ("DNAPL")), is present within the sand and gravel aguifer. The concentration of 2,4,6-
trichlorophenol is approximately 20 percent of its reported solubility level in water. The
highest concentranons of benzene occur in the southcentral portion of the Site west of the large
parking lot, while the highest concentrations of 2,4,6-trichlorophenol occur near the southern
portion of the large parking lot.

The groundwater analytical data suggest groundwater guality east of the Coraopolis Bridge
has not been affected by previous disposal activities at the Site. No analytes exceeded MCL in
groundwater east of the Coraopolis Bridge. Groundwater guality in the western and northern
portions of the Site generally does not appear to have been adversely affected by previous
disposal activities. Certain metals concentrations (e.g., nickel), however, exceed the MCL in
areas where surface disposal of foundry sand occurred.

Groundwater monitoring data collected at the Site are summarized in Table 1 (Volatile
Organic Compounds in Groundwater), Table 2 (Semi-volatile Organic Compounds in Groundwater), and
Table 3 (Metals in Groundwater).

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                  Table 1 - Volatile Organic Compounds in Groundwater
Detection
Frequency
out of 80
samples)
6
9
1
1
1
5
1
2
7
2
2
25
4

2
Minimum
Detected
Concentration
(ppb)
0.85
6
-
-
-
0.86
-
1.9
0.27
7
4
3
3

7
Maximum
Detected
Concentration
(ppb)
5
220
38
10
4.4
110
1.2
4.3
18
10
7
50,000
7

7.2

Level of
Concern
(ppb)*
4.1
370
3.6
35
55
12
5 (MCL)
200 (MCL)
1.6
190
100
5 (MCL)
1000
(MCL)
10000
          voc

Methylene Chloride
Acetone
Chloroethane
Chlorobenzene
1,2-Dichloroethene
1,2-Dichloroethane
Tetrachloroethane
1,1,1-Trichloroethane

Trichloroethene
2-Butanone  (MEK)
Carbon Disulfide
Benzene

Toluene

Xylenes
                                                                                     (MCL)

  Level of Concern represents either drinking water standards  (with connotation "MCL") or
  EPA Region III Risk-Based Concentrations. The latter ones are provided for the chemicals
  which do not have MCLs.  The Risk Based Concentrations for carcinogenic chemicals  (based on
  the concentration slope factor) represent a cancer risk of 10 -6. The Risk Based
  Concentrations for non-carcinogenic chemicals (based on the reference dose) represent a
  hazard quotient of 0.1.  These numbers represent the threshold of risk and are provided for
  screening the contaminants historically detected at the Site.

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             Table 2 - Semivolatile Organic Compounds in Groundwater
         SVOC
Detection
Frequency
(Out of 73
Samples)*
Phenol                     12
2-Methylphenol             15
4-Methylphenol             21
2-Nitrophenol               1
2,4-Dimethylphenol          7
2-Chlorophenol             14
2,4-Dichlorophenol         16
2, 4, 6-Trichlorophenol      13
Di-n-butylphthalate         1
Di-n-octylphthalate         4
Bis(2-ethylhexyl)            9
phthalate
Naphthalene                 1
  Minimum
  Detected
Concentration
   (ppb)

      3
      1
      2

     17
      1
      1
      1

      1
      1
  Maximum
  Detected
Concentration
   (ppb)

    85,000
    58,000
    76,000
       1
     6,700
    36,000
    19,000
   210,000
       1
      12
     170
Level of
 Concern
(ppb)**

  2200
   180
   18

   73
   18
   11
   6.1
   370
   73
  0.48

   150
* Excluding field blank samples

** Level of Concern represents either drinking water standards (with connotation "MCL")  or
   EPA Region III Risk-Based Concentrations. The latter ones are provided for the chemicals
   which do not have MCLs. The Risk Based Concentrations for carcinogenic chemicals (based
   on the concentration slope factor) represent a cancer risk of 10 -6. The Risk Based
   Concentrations for non-carcinogenic chemicals (based on the reference dose)  represent a
   hazard quotient of 0.1. These numbers represent the threshold of risk and are provided
   for screening site contaminants historically detected at the Site.

-------
                     Table  3  -  Metals in Groundwater
                    Detected
                 Frequency  (out
                  of 71  samples
                                           Minimum Detected
                                          Concentration  (ppb)
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Selenium
Silver
Sodium
Thallium
Vanadium
Zinc
Cyanide
                        41
                        13
                        71
                                                                                              1.1
Level of Concern represents  either  drinking water standards  (with connotation  "SMCL")  or EPA Region III
Risk-Based Concentrations. The  latter ones are provided for the chemicals which  do  not have MCLs.  The
Risk Based Concentrations  for carcinogenic chemicals (based on the concentration slope factor)
represent a cancer risk of 10 -6. The Risk Based Concentrations for non-cardnogenie  chemicals  (based
on the reference dose) represent  a  hazard quotient of 0.1. These numbers represent  the threshold of
risk and are provided  for  screening site contaminants historically detected  at the  Site.

-------
B. Groundwater Contamination in Intrinsic Remediation Demonstration Study

NLC submitted its Intrinsic Remediation Demonstration Study (IRD) proposal to EPA in
October 1996. The purpose of the study was to collect data to evaluate natural attenuation
processes that may be occurring at the Site. EPA, in consultation with PADEP, commented on the
proposal and revisions were incorporated as the study progressed. The revised proposal and
EPA's comment letters have been included in the Administrative Record. A supplemental study to
evaluate the guality of the groundwater beneath the Back Channel of the Ohio River was also
performed and the final report is included in the Administrative Record. All this documentation
is referred to collectively in this Record of Decision as the OU3 study. The OU3 study
demonstrates that natural attenuation is occurring at rates sufficient to be protective of human
health and the environment. The study pinpoints the extent and fate of the plume by sampling,
evaluating, and modeling biological, physical and chemical aspects of the natural attenuation
processes.

The OU3 study is divided into two separate, but related components: (1) the evaluation of
the extent and stability of the plume, and (2) the evaluation of the fate and transport of the
plume in relationship to the Coraopolis public drinking water well field. The tasks performed
for the first component of the study include:

D Evaluation of existing monitoring well operability and initial (May 1996)
sampling;
D Drilling and installation of nine new monitoring wells;
D Groundwater sampling and analysis of 37 monitoring wells;
D Assessment of past and present plume configuration;
D Analysis of redox reactions based on electron acceptor relationships.

The tasks performed for the second component of the OU3 study were the following:

D Analysis of aguifer parameters;
D Water level monitoring;
D Flow net analysis;
D Pumping test at Coraopolis well field;
D Development of a three-dimensional groundwater flow model;
D Solute transport modeling;
D Evaluation of mass balance;
D Evaluation of mass loading to surface water;
D Sampling aguifer beneath the Back Channel.

The nature and the extent of groundwater contamination at the Site based on the OU3 study is
summarized below.

1. Aguifer Characteristics

To characterize the relationship between the aguifer at the Site and the aguifer at the
Coraopolis well field, a pumping and recovery test was conducted using the Coraopolis
production wells. The Coraopolis well field consists of three primary supply wells (Wells 2, 6,
and 8) and four backup wells. The annual average production rate for the system is
approximately 850,000 gallons per day ("gpd"). Above average pumping rates were used to
evaluate whether the contaminated plume at the Site could potentially influence the municipal
wells. The test results indicate that the aguifer at the Coraopolis well field exhibits the
characteristics of a partially confined or leaky confined alluvial aguifer with a low storage
capacity and low transmissivity. No measurable hydraulic connection between the Coraopolis well
field and the Site was observed with the increased rate of pumping. Groundwater fluctuations in

-------
the Site wells closely matched fluctuations in the Ohio River, indicating a high degree of
hydraulic interconnection and the river's domination over groundwater flow in the aguifer.

To further evaluate whether the groundwater pumping at the Coraopolis well field has the
potential to capture groundwater originating at the Site, the OU3 study includes a three-
dimensional groundwater flow model called the FTWORK model. The FTWORK model shows that the Ohio
River is the source of virtually all of the water captured by the Coraopolis well field.
Although sensitivity analysis shows that groundwater could theoretically flow from the Site to
the Coraopolis well field, the estimated contribution of water from the Site would be less than
0.2 percent of the total groundwater flow.

2. Extent of the Plume

To determine the southern extent of the plume of contaminated groundwater at the Site, NLC
collected 13 groundwater samples in August 1997 at nine locations south of the western tip of
Neville Island beneath the Ohio River Back Channel (see Figure 5B). The sampling locations were
approved by EPA after consultation with PADEP. Because benzene and phenolics are the most
prevalent compounds in the plume, benzene and 2,4,6-trichlorophenol were used as indicator
parameters for defining the extent of the plume. Benzene was detected in samples from one
location at concentrations of 6.7 ppb and 1.0 ppb. Other VOCs detected were toluene (four
samples), xylenes (one sample), carbon disulfide (one sample), and 22-hexanone (one sample), all
at concentrations below MCLs. Two phenolic compounds were detected at concentrations below the
level that can be measured with certainty. Their concentrations were estimated to be l/10th of
the analytical detection limit. 4-Methylphenol was detected in one sample and 2,4-dimethyl
phenol was detected in three samples. No other phenolic compounds were detected.

The distribution of the benzene concentrations in the Back Channel in the mid-depth
portion of the aguifer (see Figure 6) and the deeper portion of aguifer (see Figure 7) confirms
that the plume is limited to the southern shore of Neville Island with little contamination

migrating to the south. The concentrations and distribution of xylenes, toluene, and phenolics
are also limited to beneath the former disposal areas, as defined in the RI and OU3 study,

The results of the OU3 study indicated that both the size of the plume and the
concentrations of its main contaminants are being stabilized or reduced in time. The OU3 study
focused on two Site-related contaminants of concern in the plume: benzene and 2,4,6-
trichlorophenol. To allow comparison with historical data, the OU3 groundwater sampling also
includes analysis for the same VOCs and semi-volatile organic compounds ("SVOCs") as the RI
Report. A comparison of RI and OU3 study results is presented in Tables 4 and 5. The tables show
virtually no change in the plume character based on the number and type of constituents detected
between 1993 and 1996.

The benzene plume, located beneath the trench area, is elliptical in shape and oriented
southeast-northwest in the shallow, mid-depth, and deep groundwater. The plume area has
decreased steadily over time. The current plume is smaller than the benzene plumes observed
in 1981, 1984, 1987, and 1993 (see Figures 8, 9, 10 and 11). The coal coking sludge that was
disposed at the Site is considered to be the main source of benzene. The boundary of the 1996
benzene plume (see Figure 12) coincides with the area where sludge disposal occurred and
confirms that the plume has remained stable. The concentration and distribution of VOCs and
phenolics (see Figure 13), showed a pattern similar to the results of the RI Report.

-------
3. Natural Attenuation of the Plume

A major task of the OU3 study was to demonstrate the presence and extent of active
biodegradation processes within the plume, the effectiveness of biodegradation in controlling
the development of the plume, and establishing rates of biodegradation. The primary objective of
the study was to develop a predictive model for the fate and transport of contaminants that
could be used to demonstrate the long-term effectiveness of natural attenuation processes
occurring at the Site. Natural attenuation processes were evaluated by (1) sampling the
groundwater for key contaminants and their degradation products to assess how the plume has
changed over time, and (2) comparing the analytical data with specific geochemicad indicators to
verify whether active biodegradation is occurring within and at the boundaries of the plume.

Biodegradation processes rely on naturally occurring microbes that use chemical compounds as
a source of energy. Biodegradation is accomplished by a series of chemical reactions taking
place in very slowly flowing groundwater. The order of these reactions depends mostly upon the
amount of energy that they produce; those reactions that produce the greatest amount of energy
occur first. As the higher energy reactions are completed, the reactions generating the next
lowest amount of energy will occur. The first reactions use oxygen (aerobic reaction) and occur
as long as enough dissolved oxygen is present. After the dissolved oxygen is depleted, a series
of anaerobic reactions occur using nitrate, manganese, ferric iron, sulfate, and carbon dioxide
seguentially in place of oxygen. As a result of these microbially mediated reactions, the
substances in the groundwater that can be used as sources

-------
    Table 4 - Comparison of VOC Concentrations in RI and OU3 Study
    VOC

    2-Butanone

    Acetone

    Benzene
 Detection  Frequency
 RI              IRD
(n =  80)      (n  =  39)
                                                  Minimum Detected      Maximum Detected
                                                Concentration (ug/L)  Concentration (ug/L)
                                                   RI        IRD           RI        IRD
   2

   9

  25
    Carbon disulfide      2

    Chlorobenzene         1

    Chloroethane          1

    1,2-Dichloroethane    5

    1,2-Dichloroethene    1

    Ethylbenzene          0

    Methylene chloride    6

    Tetrachloroethene     1

    Toluene               4

    1,1,1-Trichloroethane 2

    Trichloroethene       7

    Xylenes               2
 3

 2

16

 2

 3

 1

 0

 0

 2

 2

 0

 5

 0

 0

 3
7 J       5.4

6 J       330 E

3 J       9.8
 101       2.200

 220      1.500 E

50.000    210.000
                            4  J       4.2  J        7  J        17

                                      3.5           10 J       14

                                                   38        29

                           0.86        -            110 J

                                                   4.4

                                      120             -        170

                           0.85 B      3.8           5.1       4.3

                                                   1.2

                            3  J       3.6           7 J       18.000

                            1.9        -            4.3

                           0.27        -              18        -

                            7  J       5.6           7.2 J    1.600  E
E = Quantification beyond calibration range
J = Estimated concentration

-------
     Table,  5 - Comparison of SVOC Concentrations  in RI  and OU3  Study

                            Detection Frequency

2-Chlorophenol
2, 4-Dichlorophenol
2, 4-Dimethylphenol
2-Methylphenol
4-Methylphenol
2-Nitrophenol
Phenol
2,4, 6-Trichlorophenol
RI
(n = 73)
14
16
7
15
21
1
12
13
IRD
(n = 7)
4
5
5
5
5
0
7
5
Concentration
RI
1
1
17
1
2

3
1
J
J
J
J
J
-
J
J
(ug/L)
IRD
6.4
13
3.7
1
2.9
-
34
1.2
Concentration
RI
36,
19,
6,
58
76

85
000 J
000 J
700 J
,000
,000
1 J
,000
210,000
(ug/L)
IRD
6,
25,
21,
32,
37,

14,
130,
000
000
000
000
000
-
000
000
J = Estimated concentration

-------
of energy are depleted and the concentrations of the natural attenuation by-products increase.

The OU3 study analyzed the following parameters to track the progression of the natural
attenuation processes: dissolved oxygen, nitrate, sulfate, dissolved manganese, dissolved iron,
methane, and carbon dioxide. The study found that along the margins of the plume, a zone of the
depleted dissolved oxygen is present (see Figure 14). The existence of this zone indicates that
aerobic degradation is occurring along the margins of the plume, The depletion of dissolved
oxygen to concentrations to less than 0.5 milligrams per liter ("mg/1") within the the plume
indicates that biodegradation is also occurring in the plume interior. The accumulation of
metabolic by-products in the vicinity of the plume also provides evidence of anaerobic
processes. These by-products include dissolved manganese, dissolved iron, carbon dioxide, and
alkalinity. Modeling performed by NLC and independently by the EPA Robert S. Kerr Environmental
Research Laboratory in Ada, Oklahoma, agrees that sulfate makes an excellent tracer of the plume
location and natural attenuation reactions taking place within the plume. The leading edge of
elevated sulfate and natural attenuation by-products (e.g., dissolved manganese and iron)
extends 300-400 feet beyond the leagding edge of the benzene plume and is a measurable
demonstration that biodegradation is constraining migration of the plume by destruction of
organic constituents.

While the intrinsic remediation demonstration focused on the natural attenuation of
benzene, other organic constituents present in the groundwater at the Site (e.g., 2,4,6-
trichlorophenol, toluene, ethylbenzene, and xylenes) also biodegrade in a same or similar
manner as benzene. The selection of benzene as the primary focus of the study was appropriate
given the limited occurrence of these other compounds in the plume.

VII. SUMMARY OF SITE RISKS

As part of the RI/FS performed for the Site, analyses were conducted to estimate the
human health and environmental hazards that could result if contamination at the Site is not
cleaned up. These analyses are commonly referred to as Risk Assessments and identify existing
and future risks that could occur if conditions at the Site do not change. The Baseline Human
Health Risk Assessment ("BLRA") evaluated human health risks and the Ecological Risk Assessment
("ERA") evaluated environmental impacts from the Site.

A. Human Health Risks

The BLRA assesses the toxicity, or degree of hazard, posed by contaminants, related to the
Site, and involves describing the routes by which humans and the ecological receptors could
come into contact with these substances. Separate calculations are made for those substances
that can cause cancer (carcinogenic) and for those that can cause non-carcinogenic, but adverse,
health effects. In general, a baseline risk assessment is performed in four steps: (1) data
collection and evaluation, (2) exposure assessment (3) toxicity assessment, and (4) risk
characterization. Each of these steps is explained further below.

1. Data Collection and Evaluation

The data collected during the RI were evaluated for use in the BLRA, This evaluation
involved reviewing the guality of the data to determine which are appropriate to use to
guantitatively estimate the risks associated with Site soil, sediment, surface water, and
groundwater. The concentrations used to determine human health risks are derived by averaging
the data for each media and then calculating the upper 95th percentile confidence limit. By
using this upper confidence limit, EPA can be 95% certain that the true average concentration

-------
does not exceed this level. This concentration is referred to as the reasonable maximum
exposure ("RME")  concentration because an individual would not reasonably be expected to be
exposed to a higher concentration. The RME values calculated based on the Site data are
summarized in Table 6.

-------
       Table 6 - Reasonable Maximum Exposure Point Concentrations
Contaminant





2,4-D





alpha-BHC





beta-BHC





delta-BHC





gamma-BHC





Aldrin





Dieldrin





Endosulfan sulfate





gamma-chlordane





Arochlor-1254





Arochlor-1260





Phenol





2-Chlorophenol





2-Methylphenol





4-Methylphenol





2,4-Dichlorophenol





2,4,6-Trichlorophenol
Sub-
Surface surface Ground- Surface
Soil Soil water Water
(mg/kg) (mg/kg) (mg/L) (mg/L)
7.24E-02
2.32E-01 3.78E+00
1.95E-01 3.22F+00
1.54E-03
2.69E-01
5.35E-02
5.59E-02 3.09E-09
Sediment Fish
(mg/kg) (mg/kg)







L78E-02
5.21E-01
             3.16E-01
                                       2.51E-05
                                                                3.51E-01
                                                    1.52E-01
             1.77E+00
                         5.26E+01





                         5.23E+00





                         4.01E+01





                         5.37E+01





                         2.47E+01





                         1.08E+02

-------
       Table 6 - Reasonable Maximum Exposure Point Concentrations
Contaminant

Carbon disulfide
1,2-Dichloroethane
Trichloroethene
1,1,2-Trichloroethane
Benzene
Chlorobenzene
Naphthalene
Benzo(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Indeno(1,2,3-cd)pyrene
Dibenz(a,h)anthracene
Benzo(g,h,i)perylene
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Copper
Cyanide
Manganese

Surface
Soil
(mg/kg)






2.39E+01
6.36E+00
5.55E+01
8.32E+00
2.98E+00
5.10E+00
3.82E+00
1.84E+00
3.53E+00
1.55E+04

1.18E+01
2.31E+02
1.67E+00
Sub-
surface
Soil
(mg/kg)







2.03E+00

2.54E+00

1.37E+00
l.OOE+00
9.53E-01

1.78E+04



2.45E+00

Ground-
water
(mg/L)
1.45E+00
1.44E+00
1.45E+00
1.45E+00
2.19E+01
1.45E+00









1.77E+01
1.32E-02
4.19E-03
3.67E-01
3.54E-03
2.80E+01

6.72E+01
1.84E+01
1.95E+03
             1.58E+03
7.46E-03
9.44E-03 9.85E-03
2.20E-01
                           7.82E+01
                                                           Surface
                                                          Water
                                                           (mg/L)
2.25E+00



1.48E+01

2.91E+00

7.57+01



2.62E+03
                                             Sediment
                                              (mg/kg)
                          Fish
                         (mg/kg)
 1.55E-02
8.80E-02

9.50E-03

1.58E-01
 3.50E-03
                                                                         1.80E+01

-------
Table 6 - Reasonable Maximum Exposure Point Concentrations



Contaminant
Mercury
Nickel
Thallium
Silver
Vanadium
Zinc
Sub-
Surface surface
Soil Soil
(mg/kg) (mg/kg)
8.27E-01

8.62E-01

3.88E+01


Ground-
water
(mg/L)

1.56E-01

1025E-02

3.32E+00

Surface
Water
(mg/L)
3.49E-04







Sediment Fish
(mg/kg) (mg/kg)
1.92E+00




1.77E+03

-------
2. Exposure Assessment

An exposure assessment involves three basic steps: 1) identifying the potentially exposed
populations, both current and future; 2) determining the pathways by which these populations
could be exposed; and 3) guantifying the exposure. Under Site conditions prior to cleanup, the
BLRA identified the following populations as having the potential for exposure to Site-related
contaminants, either currently and/or in the future:

6 future residents living on the Site;
6 current and/or future off-site residents;
6 current and/or future recreational users of the Site;
6 future commercial or industrial workers at the Site; and
6 trespassers.

Future residents living on the Site have the potential for exposure to Site-related
contaminants through (1) ingestion of soil, sediments, surface water, groundwater, and fish, (2)
direct contact with surface water; and (3) inhalation of water vapor during showering. If the
future residents obtain drinking water through a public drinking water supply, the groundwater
ingestion and inhalation pathways would be eliminated. For off-site residents, similar exposure
pathways exist, however, the overall potential for exposure is less. Off-site residents would
only be exposed to Site soils during recreational use of the Site and their exposure to
Site-related contaminants in drinking water supplies would be substantially reduced.

Recreational users of the Site have the potential for exposure to Site-related contaminants
through ingestion of fish, surface water, soil, and sediment as well as through direct contact
with surface water. Workers at the Site could be exposed to contaminants through ingestion of
Site soil and by drinking groundwater unless drinking water is provided through a public water
supply. Trespassers have potential for exposure through ingestion and direct contact with Site
surface water and through ingestion of Site soil.

In order to guantify the potential exposure associated with each pathway, assumptions must
be made for the various factors used in the calculations. Table 7 summarizes the values used in
the BLRA.

-------
                Table 7 - Exposure Assessment Factors
Exposure
Factors
Soil
Sediment
Surface
Water
                                                                  Groundwater
Fish
INGESTION EXPOSURE PATHWAY

Ingestion Rate:
 Adult         100 mg/day       100 mg/day
 Child         200 mg/day       200 mg/day
 Adult Worker   50 mg/day
 Adolescent    100 mg/day

Exposure Fre-
quency  (EF) :
 Resident     350 days/year
 Recreational  20 days/year     20 days/year
 Worker       250 days/year
 Trespasser    50 days/year

DERMAL CONTACT EXPOSURE PATHWAY

Skin Surface
Area:
 Adult
 Child
 Adolescent

EF:
 Recreational
 Trespasser
 Child Bathing

Bath Duration:

INHALATION EXPOSURE PATHWAY
                              2 liters/day
                              1 liter/day

                             0.5 liters/day
                                2 liters/day
                                1 liter/day
                                2 liters/day
                                 54 g/day
                                 20 g/day
                              350 days/year   350 days/year
                               7 days/year                  350 days/year
                                              250 days/year
                               7 days/year
                               18,000 cm 3
                               7,200 cm 3
                               16,000 cm 3
                              7 days/year
                              7 days/year
                             350 days/year

                            0.33 hours/day
                                7,200 cm 3
                                350 days/year

                                0.33 hours/day
Inhalation
Rate: Adult

EF:

Shower
 Duration:
                            0.0139 m 3/min     0.0139 m/min

                             350 days/year     350 days/year
                              12 min/day
                                12 min/day

-------
               Table 7 - Exposure Assessment Factors
Exposure
Factors
Soil
Sediment
Surface
 Water
                                                              Groundwater
Fish
EXPOSURE ASSESSMENT CONSTANTS
Exposure
Duration:
  Adult resident
  Adult worker
  Child resident
  Adolescent
   trespasser
24 years
25 years
 6 years

 6 years
24 years
 1 year
 6 years
               24 years
               25 years
                6 years
Body Weight:
  Adult
  Child
  Adolescent
70 kg
15 kg
55 kg
Averaging
Time:
 Adult resident
 Child resident
 Adult worker
 Trespasser
Carcinogens:
70 years
70 years
70 years
70 years
         Noncarcinogens:
         24 years
         6 years
         25 years
         6 years

-------
3. Toxicity Assessment

The purpose of the toxicity assessment is to weigh available evidence regarding the
potential for particular contaminants to cause adverse effects in exposed individuals. Where
possible, the assessment provides a quantitative estimate of the relationship between the extent
of exposure to a contaminant and the increased likelihood and/or severity of adverse effects.

A toxicity assessment for contaminants found at a Superfund site is generally accomplished
in two steps: 1) hazard identification, and 2) dose-response assessment. Hazard identification
is the process of determining whether exposure to an agent can cause an increase in the
incidence of a particular adverse health effect (e.g., cancer or birth defects) and whether the
adverse health effect is likely to occur in humans. It involves characterizing the nature and
strength of the evidence of causation. Dose-response evaluation is the process of quantitatively
evaluating the toxicity information and characterizing the relationship between the dose of the
contaminant administered or received and the incidence of adverse health effects in the
administered population.

From this quantitative dose-response relationship, toxicity values (e.g., reference doses
and slope factors) are derived that can be used to estimate the incidence or potential for
adverse effects as a function of human exposure to the agent. These toxicity values are used in
the risk characterization step to estimate the likelihood of adverse effects occurring in humans
at different exposure levels.

For the purpose of the risk assessment, contaminants were classified into two groups:
potential carcinogens and noncarcinogens. The risks posed by these two types of compounds are
assessed differently because noncarcinogens generally exhibit a threshold dose below which no
adverse effects occur, while no such threshold can be proven to exist for carcinogens. As used
here, the term carcinogen means any chemical for which there is sufficient evidence that
exposure may result in continuing uncontrolled cell division (cancer) in humans and/or animals.
Conversely, the term noncarcinogen means any chermical for which the carcinogenic evidence is
negative or insufficient.

Slope factors have been developed by EPA's Carcinogenic Assessment Group for estimating
excess lifetime cancer risks associated with exposure to potentially carcinogenic contaminants
of concern. Slope factors, which are expressed in units of (kgod/mg) are multiplied by the
estimated intake of a potential carcinogen, in mg/kg/day, to provide an upper-bound estimate of
the excess lifetime cancer risk associated with exposure at that intake level. The term
"upper-bound" reflects the conservative estimate of the risks calculated from the slope
factor. Use of this approach makes underestimation of the actual cancer risk highly unlikely.
Slope factors are derived from the results of human epidemiological studies or chronic animal
bioassays to which animal-to-human extrapolation and uncertainty factors have been applied to
account for the use of animal data to predict effects on humans. Slope factors used in the
baseline risk assessment are presented in Table 8.

Reference doses ("RfDs") have been developed by EPA to indicate the potential for adverse
health effects from exposure to contaminants of concern exhibiting noncarcinogenic effects.
RfDs, which are expressed in units of mg/kg/day, are estimates of acceptable lifetime daily
exposure levels for humans, including sensitive individuals. Estimated intakes of contaminants
of concern from human epidermiological studies or animal studies to which uncertainty factors
have been applied account for the use of animal data to predict effects on humans. Reference
doses used in the baseline risk assessment are presented in Table 8.

4. Human Health Effects

-------
    The health effects of the Site contaminants that are most associated with the unacceptable
risk levels are summarized below. In most cases,  the information in the summaries is drawn from
the Public Health Statement in the Agency for Toxic Substances and Disease Registry's (ATSDR)
toxicological profile for the chemical.

    Aldrin & Dieldrin: The carbamate insecticide Aldrin exists as a colorless crystalline solid
at room temperature,  having a molecular weight of 365 and melting point of 104 C. It is highly
soluble in non-polar solvents but only slightly soluble in water. Aldrin is readily taken into
the body via inhalation,  dermal absorption,  ingestion or eye contact. EPA considers aldrin to be
a Class B2 carcinogen because it causes tumors in rats and mice. Aldrin also causes birth
defects and damage to the reproductive system, liver toxicity, and central nervous system
abnormalities following chronic exposure. It is also acutely toxic, with an oral LD50 (i.e.,
dose which is lethal to 50% of the test animals in research studies)  of about 50 mg/kg.  Aldrin
is highly toxic to

-------
6.30E+00
1.80E+00
1.80E+00
1.30E+00
1.70E+01
1.60E+01

1.30E+00
7.70E+00
7.70E+00




6.
1.
1.

1.
1.

1.






30E+00
80E+00
79E+00

72E+01
61E+01

30E+00









3.00E-04
3.00E-05
5.00E-05
6.00E-03
6.00E-05


6.00E-01
5.00E-03
5.00E-02
5.00E-03
                               1.10E-02
                           1.75E+00

                           4.30E+00
                                            1.09E-02
           Table 8 - Slope Factors and Reference Doses

                              Slope factors (kgod/mg)

Chemical                        Oral        Inhaled
2,4-D
alpha-BHC
beta-BHC
delta-BHC
gamma-BHC
Aldrin
Dieldrin
Endosulfan sulfate
gamma-chlordane
Arochlor-1254
Arochlor-1260
Phenol
2-Chlorophenol
2-Methylphenol
4-Methylphenol
2,4,-Dichlorophenol
2,4,6-Trichlorophenol
Carbon disulfide
1,2-Dichloroethane
Trichloroethene
1,1,2-Trichloroethane
Benzene
Chlorobenzene
Naphthalene
Benzo(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Indeno(1,2,3-cd)pyrene
Dibenz(a,h)anthracene
Benzo(g,h,i)perylene
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Copper
Cyanide
Manganese
Mercury
Nickel
Thallium
Silver
Vanadium
Zinc
                                                           Reference Doses  (mg/kg/d)

                                                           Oral          Inhaled

                                                           l.OOE-02
                                                           3.00E-03










7
7
7
7

9.10E-02
1.10E-02
5.70E-02
2.90E-02


7.30E-01
7.30E-03
7.30E-01
.30E-02
.30E+00
.30E-01
.30E+00

9.10E-02
6.00E-02
5.60E-02
2.91E-02


6.10E-01
6.10E-03
6.10E-01
6.10E-02
6.10E+00
6.10E-01
6.10E+00
l.OOE-01 2.86E-03
2.86E-03
6.00E-03
4.00E-03
1.43E-04
2.00E-02 5.71E-03
4.00E-02







1.51E+01

8.40E+00
6.30E+00
4.20E+01
2.90E+00
4.00E-04
3.00E-04
7.00E-02
5.00E-03
5.00E-04
5.00E-03
1.43E-04
                                                          .71E-02
                                                          .OOE-03
                                                          .OOE-03
                                                          .OOE-04
                                                          .OOE-02
                                                         8.00E-05
                                                         5.OOE-03
                                                         7.OOE-03
                                                         3.00E-01
                          1.14E-04
                          8.57E-05

-------
aquatic organisms, and has been associated with large-scale kills of terrestrial wildlife in
treated areas.

Antimony: Antimony can enter the body by absorption from the gastrointestinal tract
following ingestion of food or water containing antimony, or by absorption from the lungs after
inhalation. Ingestion of high doses of antimony can result in burning stomach pains, colic,
nausea, and vomiting. Long-term occupational inhalation exposure has caused heart problems,
stomach ulcers, and irritation of the lungs, eyes, and skin. The critical or most sensitive
noncarcinogenic effects of exposure to antimony are shortened life span, reduced blood glucose
levels, and altered cholesterol levels. Existing data suggest that antimony may be an animal
carcinogen but are not sufficient to justify a quantitative cancer potency estimate at this
time. In laboratory rats, inhalation of antimony dust can increase the risk of lung cancer.
However, there is no evidence of increased risk of cancer to animals from eating food or
drinking water containing antimony. It is not known whether antimony can cause cancer in humans.

Arsenic: Arsenic is a metal that is present in the environment as a constituent of many
organic and inorganic compounds. Arsenic is a known human carcinogen implicated in skin cancer
in humans. Inhalation of arsenic by workers is known to cause lung cancer. Arsenic compounds
cause chromosome damage in animals, and humans exposed to arsenic compounds have an increased
incidence of chromosomal aberrations. Arsenic compounds are reported to be teratogeruc,
fetotoxic, and embryotoxic in some animal species. Dermatitis and associated lesions are
attributable to arsenic coming into contact with the skin, with acute dermatitis being more
common than chronic. Chronic industrial exposures may be characterized by hyperkeratosis, and an
accompanying hyperhidrosis (excessive sweating usually of the palms and soles of the feet).

Benzene: Benzene is readily absorbed by inhalation and ingestion, but is absorbed to a
lesser extent through the skin. Most of what is known about the human health effects of benzene
exposure is based on studies of workers who were usually exposed for long periods to high
concentrations of benzene. Benzene is toxic to blood-forming organs and to the immune system.
Excessive exposure (inhalation of concentrations of 10 to 100 ppm) can result in anemia, a
weakened immune system, and headaches. Occupational exposure to benzene may be associated with
spontaneous abortions and miscarriages (supported by limited animal data), and certain
developmental abnormalities such as low birth weight, delayed bone formation, and bone marrow
toxicity. Benzene is classified as a Group A human carcinogen based on numerous studies
documenting excess leukemia mortality among occupationally exposed workers.

Beryllium: The respiratory tract is the major target of inhalation exposure to beryllium.
Short-term exposure can produce lung inflammation and pneumonia-like symptoms. Long-term
exposure can cause berylliosis, an immune reaction characterized by noncancerous growths on
the lungs. Sirmilar growths can appear on the skin of sensitive individuals exposed by dermal
contact. Epidemiological studies have found that an increased risk of lung cancer may result
from exposure to beryllium in industrial settings. In addition, laboratory studies have shown
that breathing beryllium causes lung cancer in animals. However, it is not clear what cancer
risk, if any, is associated with ingestion of beryllium. EPA has classified beryllium as a Group
B2 probable human carcinogen based on the limited human evidence and the animal data.

Chlordane: Chlordane can be absorbed by the body through dermal contact, inhalation of
particulates in ambient air, and ingestion of contaminated food or soils. It may remain stored
for months or years in the blood plasma or the body fat of the liver, spleen, brain, and
kidneys. Little data are avaialable on the adverse health effect of chlordane exposure in
humans. Symptoms associated with human overexposure to this compound include headache,
dizziness, lack of coordination, irritability, weakness, and convulsions. In humans, an acute
oral lethal dose of chlordane was estimated to be between 25 and 50 mg/kg. Experimental studies
exploring the health effects on animals exposed to various levels of chlordane showed an

-------
association between exposure and immunologic dysfunction, reproductive dysfunction, nervous
system damage, liver damage, convulsions, liver cancer, and death. The lethal dose of chlordane
in rats is estimated to be between 85 and 560 mg/kg. Some occupational epidenuiology research
suggests an increased cancer risk associated with human exposure to chlordane. Chronic oral
treatment with chlordane resulted in significant increases in hepatocellular carcinomas in mice.
The EPA has classified chlordane as belonging to Group B2 probable human carcinogens.

Chlorobenzene: Chlorobenzene is a colorless liguid with a mild aromatic odor. It is used in
the manufacture of aniline, phenol, and chloronitrobenzene and as an intermediate in the
manufacture of dyestuffs and many pesticides. Exposure to Chlorobenzene can occur through
inhalation, ingestion, eye and skin contact. Direct contact exposure can lead to eye, nose and
skin irritation. Long term exposure may cause liver damage. Chlorobenzene is not classifiable
as to carcinogenicity.

2-Chlorophenol: 2-Chlorophenol exists as a light amber liguid. It is used as an intermediate
in the manufacture of dyestuffs, higher chlorophenol, and preservatives. 2-Chlorophenol is toxic
by all routes (i.e., ingestion, inhalation, dermal contact). Effects from exposure include burns
to the skin and eyes, weakness, headache, dizziness, damage to the lung, liver, and kidneys, and
death from cardiac or pulmonary failure. Ingestion caused increase then decrease of respiration;
blood pressure; urinary output; fever; increased bowel action, motor weakness; collapse with
convulsions and death. Ingestion causes lung, liver, kidney damage and contact dermatitis. Acute
exposures by all routes may cause muscular weakness, gastroenteric disturbances, severe
depression and collapse. Although effects are primarily on the central nervous system, edema of
the lung and injury of pancreas and spleen also may occur. Oral exposure may produce rapid
circulatory collapse and death. Chronic poisoning from oral or percutaneous absorption may
produce digestive disturbances, nervous disorders with faintness, vertigo, mental changes, skin
eruptions, jaundice, oliguria, and uremia. 2-Chlorophenol has been shown to increase conception
rate, decrease litter sizes of exposed rats and to increase the percent of stillborn pups.

Cresols: Three types of closely related cresol exist: ortho-cresol (o-cresol), meta-cresol
(m- cresol), and para-cresol (p-cresol). Pure cresol are colorless chemicals, but they may be
found in brown mixtures such as creosote and cresylic acids (e.g., wood preservatives). Cresol
in air guickly change and break down into smaller chemicals, some of which irritate the eyes.
If you were to eat food or drink water contaminated with very high levels of cresol, you might
feel a burning in the mouth and throat as well as stomach pains. If your skin were in contact
with a substance containing high cresol levels, you might develop a rash or severe irritation.
In some cases, a severe chemical burn might result. If you came into contact with high enough
levels of cresol, for example, by drinking or spilling on your skin a substance containing large
amounts of cresol, you might become anemic, experience kidney problems, become
unconscious, or even die. Studies in animals have not found any additional effects that would
occur after long-term exposure to lower levels of cresol. It is possible that some of the
effects humans listed above, such as kidney problems and anemia, might occur at lower levels if
exposure occurs over a longer time period. Effects on the nervous system, such as loss of
coordination and twitching of muscles, are produced by low levels of cresol in animals, but we
do not know whether low levels also cause such effects in humans. Cresol may enhance the
ability of carcinogenic chemicals to produce tumors in animals, and they have some ability to
interact with mammalian genetic material in the test tube, but they have not been shown to
produce cancer in humans or animals. The EPA has determined that cresol are possible human
carcinogens. Animal studies suggest that cresol probably would not produce birth defects or
affect reproduction in humans.

1,2-Dichloroethane (1,2-DCA): The lungs, heart, liver, and kidneys are the organs primarily
affected in both humans and animals exposed to 1,2-DCA. Short-term exposure to 1,2-DCA in air
may result in an increased susceptibility to infection and liver, kidney, and/or blood

-------
disorders. Effects seen in animals after long-term exposure to 1,2-DCA included liver, kidney,
and/or heart disease, and death. 1,2-DCA has caused increased numbers of tumors in laboratory
animals when administered in high doses in the diet or on the skin, and is classified as a Group
B2 probable human carcinogen.

2,4-Dichlorophenol: 2,4-Dichlorophenol is a white solid, the form in which it is usually
sold and used. 2,4-Dichlorophenol evaporates slightly faster than water, which evaporates
slowly. It can also burn. Most of the 2,4-dichlorophenol made is used directly to make other
chemicals, especially chemicals that kill weeds and other plants. 2,4-dichlorophenol also is
used to kill germs. Reports describing possible 2,4-dichlorophenol poisoning of factory
workers suggest that if you breathe air containing 2,4-dichlorophenol for several years, you may
damage your liver, skin, and possibly your kidneys. Skin contact with it over a long period may
cause the same effects. Animals that have eaten large amounts of 2,4-dichloropbenol in food
immediately developed rapid breathing, muscle tremors, convulsions, weakness, hunched posture,
loss of consciousness, and some even died. Animals that took small amounts of it in food or
water over a long period of time had damaged livers, kidneys, spleens, bone marrow, and may also
have damaged their respiratory tracts (although this may have been from breathing in the
chemical rather than from swallowing it). Rats that drank water containing 2,4-dichlorophenol
had some changes in the immune system, but the effects of 2,4-dichlorophenol on the immune
system have not been fully studied. It is not known whether the same effects would happen in
people if they were exposed in the same way. Some pregnant animals that drank water containing
high levels of 2,4-dichlorophenol died, and those that drank enough to become sick had
spontaneous abortions or gave birth to offspring that had low birth weights. Therefore, pregnant
women who unknowingly eat or drink 2,4-dichlorophenol could harm themselves and their unborn
babies. The EPA has not classified 2,4-dichlorophenol as a carcinogen.

Hexachlorocyclohexane (HCH): Hexachlorocyclohexane (HCH), formerly known as benzene
hexachloride (BHC) and other common names, is a synthetic chemical that exists in eight chemical
forms (called isomers). One of these forms, gamma-HCH (or Y-HCK commonly known as lindane), was
once used as an insecticide on fruit, vegetable, and forest crops. It is still used in the
United States and in other countries as a human medicine to treat head and body lice and
scabies, a contagious skin disease caused by mites. It is a white solid that may evaporate into
the air. The effects of breathing gramma-HCH and/or alpha-, beta-, and delta-HCH seen in humans
are blood disorders, dizziness, headaches, and changes in the levels of sex hormones. These
effects have occurred in workers exposed to HCH vapors during pesticide manufacture. People who
have swallowed large amounts have had seizures and even died. A few people who have used very
large amounts of garnma-HCH on their skin have had blood disorders or even seizures. Animals
that have been fed gamma- and alpha-HCH have had convulsions, and animals fed beta-HCH have
become comatose. All isomers can produce liver and kidney disease. Reduced ability to
fight-infection was reported in animals fed gamma-HCK and injury to the ovaries and testes was
reported in animals fed gamma-HCH or beta-HCH. In animals, exposure by mouth to gamma HCH during
pregnancy may cause an increased number of fetuses with extra ribs. HCH isomers are changed by
the body into other chemical products, some of which may be responsible for the harmful effects.
Long-term oral administration of alpha-HCK beta HCH, gamma-HCK or technical-grade HCH to
laboratory rodents has been reported to result in liver cancer. The EPA has classified HCH as a
Group B2 probable human carcinogen.

Manganese: Following inhalation of manganese dust, absorption into the bloodstream occurs
only if particles are sufficiently small to penetrate deeply into the lungs. Long-term
inhalation of manganese dust may result in a neurological disorder characterized by imitability,
difficulty in walking, and speech disturbances. Short-term inhalation exposure has been
associated with respiratory disease. There are few reports of negative health effects in humans
exposed to manganese in drinking water or food. Laboratory studies of animals exposed to
manganese in water or food have demonstrated adverse health effects including changes in brain

-------
chemical levels, low birth weights in rats when mothers were exposed during pregnancy, slower
than usual testes development, decreased body weight gain, and weakness and muscle rigidity in
monkeys. There are no human carcinogenicity data for manganese exposure. The data from some
animal studies have shown increases in tumors in a small number of animals at high doses of
manganese, but the data are inadeguate to judge whether manganese can cause cancer. EPA has
judged manganese not classifiable as to human carcinogenicity (Group D).

Mercury: Human exposure to inorganic mercury is mainly through inhalation or ingestion. Most
dietary iorganic mercurials dissociate to divalent mercury in the gastrointestinal tract and are
poorly absorbed. Occupational studies have demonstrated that chronic exposure to metallic
mercury vapor via inhalation primarily affects the central nervous system and the kidneys.
Human exposure to organic (usually methyl) mercury is mainly through ingestion. Methyl mercury
compounds are known to be toxic via oral exposure, and fetuses and newborn infants are
particularly susceptible. Subchronic methyl mercury poisoning occurred in humans eating
contaminated fish from Minamata Bay, Japan, from 1953 to the 1960's. The medial level of total
mercury in fish in Minamata Bay was estimated to be about 11 mg/kg fresh weight. Methyl mercury
poisoning also occurred from eating bread produced from seed grain dressed with methyl mercury
fungicide. Nerve damage causing "pins and needles" sensations in the hands and feet occurred at
an estimated body burden of 25 mg of methyl mercury. No confirmed positive reports of methyl
mercury carcinogenicity in humans has appeared to date, and animal experiments have generally
yielded negative results.

Polycyclic Aromatic Hydrocarbons ("PAHs"): PAHs are a group of chemicals that are formed
by the incomplete burning of coal, oil, gas, garbage, tobacco, or almost any other organic
substance. Natural sources include forest fires and volcanoes. Conseguently, PAHs occur
naturally throughout the environment in the soil and other environmental media. Reproductive
effects have occurred in animals that were fed certain PAHs. Long-term ingestion of PAHs in
food has resulted in adverse effects on the liver and blood in mice. Those effects may also
occur in humans, but there is no exposure data to substantiate that adverse impacts in humans
have, in fact, occurred. No information is available from human studies to determine what
non-cancerous adverse health effects, if any, may result from exposure to specific levels of the
individual. PAHs, although inhalation and skin exposures to mixtures containing PAHs have been
associated with cancer in humans. The levels and lengths of exposure to the individual PAHs that
affect human health cannot be determined from the human studies available. Therefore, evaluation
of non-cancer adverse health effects that may result from exposure is somewhat uncertain.
EPA classifies a small group of PAHs as B2 probable human carcinogens. Benzo(a)pyrene is the
most potent of the carcinogenic PAHs. Serveral PAHs have caused cancer in laboratory animals
through ingestion, skin contact, and inhalation. Reports from human studies show that
individuals exposed to mixtures of other compounds and PAHs by breathing or through skin
contact for a long period of time can also develop cancer.

Polychlorinated Biphenyls ("PCBs"): PCBs can enter the body when fish, other foods, or water
containing PCBs are ingested, when air that contains PCBs is breathed, or when skin comes in
contact with PCBs. Skin irritations characterized by acne-like lesions and rashes and liver
effects were the only significant adverse health effects reported in PCB-exposed workers.
Epidemiological studies of workers occupationally exposed to PCBs thus far have not found any
conclusive evidence of an increased incidence of cancer in these groups. Effects of PCBs in
experimentally exposed animals include liver damage, skin irritations, death, low birth weights,
and other reproductive effects. Some strains of rats and mice that were fed PCB mixtures
throughout their lives showed increased incidence of cancer of the liver and other organs. Based
on these animal studies, the EPA has classified PCBs as Group B2 probable human carcinogens.

1,1,2-Trichloroethane (1,1,2-TCA): No case reports or epidemiological studies regarding
human occupational or environmental exposure are available. Studies with various animals,

-------
however, suggest that 1,1,2-TCA can enter the body following inhalation of contaminated air,
ingestion of or dermal contact with contaminated drinking water, or through dermal contact with
the solvent itself 1,1,2-TCA is a central nervous system depressant. It has narcotic properties
and can act as a local irritant to the eyes, nose, and lungs. Chronic exposure to 1,1,2-TCA is
also associated with both liver and kidney damage. It caused liver tumors in mice, but not rats.
No other studies have shown evidence of carcinogenicity, however. Further studies with rats
using higher concentrations, and other species would improve the knowledge of 1,1,2-TCA
carcinogenicity. Based upon the present evidence from animal studies, the EPA considers
1,1,2-TCA a Group C possible human carcinogen.

Trichloroethylene: Trichloroethylene is a colorless, nonflammable, noncorrosive liguid
primarily used as a solvent in vapor degreasing. It is also used as a dry-cleaning agent, and as
a chemical intermediate in the production of paints and varnishes and other chemicals.
Trichloroethylene has low acute toxicity. Chronic inhalation exposure to trichloroethylene has
been shown to cause liver, kidney, and nervous system disorders and skin irritation in animals.
The EPA has classified trichloroethylene as a Group B2-C carcinogen.

2,4,6-Trichlorophenol: 2,4,6-Trichlorophenol appears as a yellow solid. It has a strong,
sweet smell and does not burn easily. It does not occur naturally, In the past, the major uses
of 2,4,6-trichlorophenol were as an antiseptic and pesticide. Its uses also included preserving
wood, leather and glue, and preventing the buildup of mildew on fabric. In the environment,
2,4,6-trichlorophenol is found most freguently in water, especially near hazardous waste sites
contaminated with 2,4,6-trichlorophenol. 2,4,6-Trichlorophenol can evaporate into the air. The
human health effects of 2,4,6-trichlorophenol are not known. However, it is possible that
health effects observed in animals following exposure to 2,4,6-trichlorophenol could occur in
humans. No information was found on short-term animal studies. However, results of long- term
animal studies show that 2,4,6-trichlorophenol causes changes in liver and spleen cells, and
lowers body weight. Long-term exposure to high levels of 2,4,6-trichlorophenol causes death in
some animals. This suggests that high levels of 2,4,6-trichlorophenol may be life-threatening to
humans. Cancer occurs in animals after continued long-term oral exposure to
2,4,6-trichlorophenol. Whether or not 2,4,6-trichlorophenol causes cancer in humans has not been
adeguately studied. However, because 2,4,6-trichlorophenol causes cancer in animals, it is
possible that 2,4,6-trichlorophenol could cause cancer in humans. The EPA has classified
2,4,6-trichlorophenol as a Group B2 probable human carcinogen. 2,4,6-Trichlorophenol has not
been studied to determine if it causes birth defects, but 2,4,6-trichlorophenol has been shown
in animals to cause lowered body weight in newborns and a decrease in the number of offspring.
The higher the level of exposure and the longer the exposure to 2,4,6-trichlorophenol, the
greater the chance for adverse health effects.

5. Risk Characterization

The risk characterization process integrates the toxicity and exposure assessments into a
guantitative expression of risk. For carcinogens, the exposure point concentrations and exposure
factors discussed earlier are mathematically combined to generate a chronic daily intake value
that is averaged over a lifetime (i.e., 70 years). This intake value is then multiplied by the
toxicity value for the contaminant (i.e., the slope factor) to generate the incremental
probability of an individual developing cancer over a lifetime as a result of exposure to the
contaminant. The National Oil and Hazardous Substances Pollution Contingency Plan ("NCP")
established acceptable levels of carcinogenic risk for Superfund sites ranging from one excess
cancer case per 10,000 people exposed to one excess cancer case per one million people exposed.
Expressed as scientific notation, this risk range is between l.OE-04 and l.OE-06. Remedial
action is warranted at a site when the calculated cancer risk level exceeds l.OE-04. However,
since EPA's cleanup goal is generally to reduce the risk to l.OE-06 or less, EPA also may take
action where the risk is within the range between l.OE-04 and l.OE-06.

-------
The potential for noncarcinogenic effects is evaluated by comparing an exposure level over a
specified time period (i.e., the chronic daily intake) with the toxicity of the contaminant for
a similar time period (i.e., the reference dose). The ratio of exposure to toxicity is called a
hazard guotient. A Hazard Index ("HI") is generated by adding the appropriate hazard guotients
for contaminants to which a given population may reasonably be exposed. The NCP also states
that sites should not pose a health threat due to a non-carcinogenic, but otherwise hazardous,
chemical. If the HI exceeds one (1.0), there may be concern for the potential non-carcinogenic
health effects associated with exposure to the chemicals. The HI identifies the potential for
the most sensitive individuals to be adversely affected by the noncarcinogenic effects of
chemicals. As a rule, the greater the value of the HI above 1.0, the greater the level of
concern.

Table 9 summarizes the total risk levels from all appropriate exposure routes calculated
for each group of individuals.

B. Ecological Risk Assessment

NLC and EPA collectively evaluated the ecological risks associated with the Site. Based
on these evaluations, contamination in all media (i.e., surface water, sediment, soil, and
groundwater) have the potential to have significant adverse impacts on the aquatic ecosystem of
the river. In surface water, concentrations of mercury, copper, and chromium (VI) are
potentially harmful to the Main Channel of the Ohio River while chromium and copper present
an ecological risk in the Back Channel. Contaminants of ecological significance in the sediment
adjacent to the Site in both the Main Channel and the Back Channel include heavy metals,
pesticides, PCBs, and SVOCs, particularly phenols. In soil at the Site, metal contaminants
including arsenic, copper, lead, manganese, mercury and zinc are present at levels that have a
high potential to affect ecological receptors. Other soil contaminants, mostly PAHs and
pesticides, were found above background levels and could also result in adverse impacts.
Groundwater, which is a pathway by which soil contaminants reach the river, is contaminated by
several contaminants of ecological concern, particularly mercury, zinc, phenols and phthalates.
Pesticides and chlorocarbons are also of concern. Given the level of contamination in surface
water and sediment, soil contaminants from the Site are suspected to have contributed to
degradation of the river.

-------
                   Table 9 - Human Health Risks at the Site
Group of Individuals

On-Site Residents consuming groundwater

On-Site Residents on public water supply

Off-Site Residents consuming groundwater from    2.24E-04
the Site
Off-Site Residents consuming river water that    1.86E-04
came from the Site

Recreational Site Users

On-Site Workers consuming groundwater

On-Site Workers on public water supply

Trespassers
Cancer Risk
4.54E-02
3.00E-04
2.24E-04
1.86E-04
1.85E-04
1.48E-02
1.45E-05
3.35E-06
Hazard Index
10,000
26.3
1,710
25.3
25.0
732
0.0234
0.0294

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VIII. DESCRIPTION OF ALTERNATIVES

In the Feasibility Study ("FS"), engineering technologies that can be used to control the
contamination at the Site were screened according to their effectiveness and implementability.
Those technologies remaining after the screening process were then developed into remedial
alternatives. The alternatives in the FS address the following media: soil, groundwater, surface
water, and sediment. This Record of Decision focuses exclusively on groundwater; therefore,
only the FS alternatives dealing with groundwater are presented below.

Alternative 1: No Action

Present Worth Cost: $0
Time to Implement: 0

The NCP reguires that EPA consider a "No Action" alternative for every Superfund site
to establish a baseline or reference point against which each of the remedial action
alternatives are compared. In the event that the other identified alternatives do not offer
substantial benefits the reduction of toxicity, mobility, or volume of the constituents of
concern, the No Action alternative may be considered a feasible approach. This alternative
leaves the Site undisturbed and all current and potential future risks would remain.

Alternative 2: Groundwater Extraction and Treatment, Long-Term Monitoring,
and Institutional Controls

Total Present Worth Cost: $9,990,000
Time to Implement: 30 years

A groundwater extraction and treatment system would be designed and installed to contain
the contaminated groundwater at the Site and prevent off-site migration of contamination. The
groundwater extraction system would consist of five deep groundwater extraction wells, operating
with a total flow rate of 200 gallons per minute ("gpm"). The location of the extraction system
and wells would be determined during the remedial design. The groundwater treatment system would
include a metal precipitation unit to extract high concentrations of inorganic contanunants
followed by a 200 gpm air stripping system to remove the volatile organic contaminants. Before
being discharged to the Ohio River, the air stripper effluent would be passed through an
activated carbon bed to remove the residual organic contaminants, as well as pesticides and
herbicides. The system would be designed to achieve State surface water discharge reguirements.
Groundwater extraction and treatment would continue at the Site until benzene and 2,4,6-TCP
concentrations meet their MCLs for 12 consecutive guarters throughout the area of attainment.
The area of attainment encompasses the groundwater monitoring points located along the property
line on the shoreline. When the MCLs are met, the pump-and-treat operation would be suspended
and a long-term monitoring program would be implemented. If MCLs are again exceeded within the
area of attainment, groundwater extraction and treatment would be resumed until MCLs are
achieved for 12 consecutive guarters throughoufthe area of containment. The long-term monitoring
program would then resume. If MCLs are met consistently for a period of five years, the
extraction and treatment system could be permanently dismantled; however, monitoring would
continue.

A long-term monitoring program would be reguired to assess the effectiveness of the
groundwater extraction and treatment system in controlling off-site migration of contaminated
groundwater. The overall duration of the monitoring period is 30 years. This monitoring
program would consist of guarterly sampling for three years. The sampling freguency may be
reduced for some or all of the monitoring wells to semiannual or annual based on the data from
the first three years of sampling. A statistical analysis would be performed on the initial 12

-------
quarters of data to determine the appropriate monitoring frequency. The statistical approach
would be determined durinq the Remedial Desiqn. Althouqh the exact location and number of
qroundwater monitorinq points would be determined in the Remedial Desiqn, the followinq
number and qeneral locations were used for cost-estimatinq purposes:

     D     Eiqht on-site monitorinq points located alonq the property fine on the Back
           Channel side of the island;
     D     Three off-site monitorinq points located beneath the Back Channel to monitor the
           downqradient edqe of the benzene plume;
     D     One off-site monitorinq point located beneath the Main Channel; and

     D     the Coraopolis sentinel well.

     The analytical requirements include:

     D     Monitor the on-site wells and the Coraopolis sentinel well for SVOCs, VOCs,
           metals, and natural attenuation parameters  (i.e., specific conductivity, redox
           potential, dissolved oxyqen, ferrous iron); and
     D     Monitor the off-site wells for benzene, 2,4,6-trichlorophenol, sulfate, iron II,
           manqanese II and redox-potential.

     Water level measurements would also be required to evaluate the hydraulic performance
of the extraction system.

     Institutional controls would be implemented to restrict land and qroundwater use at the
Site and reduce the potential for human exposure to contamination. Deed restrictions would be
required to eliminate the future possibility of residential development and/or use of
qroundwater at the Site. Warninq siqns would be posted alonq the banks of the island to warn
fishermen aqainst eatinq fish. These siqns would be properly maintained as lonq as the fish in
the Ohio River are found to have hiqh levels of contaminants that can cause adverse human health
effects, The exact wordinq of these siqns would be aqreed upon durinq the Remedial Desiqn by
EPA, in consultation with PADEP.

Alternative 3:     Monitored Natural Attenuation and Institutional Controls

Total Present Worth Cost:  $1,010,000
Time to Implement:         30 years

     This alternative includes the lonq-term monitorinq proqram and institutional controls
described above in Alternative 2. If the natural attenuation processes continue to reduce the
plume with no evidence of miqration of benzene or 2,4,6-trichlorophenol durinq the first three
years of the lonq-term monitorinq proqram, EPA may reduce the samplinq frequency thereafter
to semi-annual or annual and the analytical requirements to the followinq:

     D     on-site wells for benzene, 2,4,6-trichlorophenol, sulfate, iron II, manqanese II,
           and redox potential;
     D     off-site wells for benzene, 2,4,6-trichlorophenol, specific conductivity, redox
           potential, dissolved oxyqen, ferrous iron; and
     D     the Coraopolis sentinel well for VOCs and metals.

     If the analytical data from the two consecutive monitorinq events indicates that the plume
has expanded and contaminants are miqratinq off-site at levels that pose an unacceptable risk to
human health or the environment, or that the natural attenuation processes are not protectinq
human health and the environment, a continqency measure includinq the installation of the

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groundwater extraction and treatment system described in Alternative 2 would be implemented.

The goal of the remediation process is to achieve MCLs in the groundwater at the
shoreline within 30 years. At any time during the remediation process, the determination that
MCLs have been achieved would be based on a statistical evaluation of groundwater data
collected for three consecutive years.

VIII. COMPARATIVE EVALUATION OF ALTERNATIVES

Each of the three remedial alternatives summarized above has been evaluated with
respect to the nine (9) evaluation criteria set forth in the NCP, 40 C.F.R. Section
300.430(e) (9). These nine criteria can be categorized into three groups: threshold criteria,
primary balancing criteria, and modifying criteria. A description of the evaluation criteria is
presented below:

Threshold Criteria:

1. Overall Protection of Human Health and the Environment addresses whether a remedy
provides adeguate protection and describes how risks are eliminated, reduced, or
controlled.
2. Compliance with Applicable or Relevant and Appropriate Reguirements ("ARARs")
addresses whether a remedy will meet all of the applicable, or relevant and appropriate
reguirements of environmental statutes.

Primary Balancing Criteria:

3. Long-term Effectiveness refers to the ability of a remedy to maintain reliable protection
of human health and the environment over time once cleanup goals are achieved.
4. Reduction o Toxicity, Mobility, or Volume through Treatment addresses the degree to
which alternatives employ recycling or treatment that reduces toxicity, mobility, or
volume of contaminants.
5. Short-term Effectiveness addresses the period of time needed to achieve protection and
any adverse impacts on human health and environment that may be posed during the
construction and implementation period until cleanup goals are achieved.
6. Implementability addresses the technical and administrative feasibility of a remedy,
including the availability of materials and services needed to implement a particular
option.
7. Cost includes estimated capital, operation and maintenance, and present worth costs.

Modifying Criteria:

8. State Acceptance indicates whether, based on its review of backup documents and the
Proposed Plan, the State concurs with, opposes, or has no comment on the preferred
alternative.
9. Community Acceptance is assessed in the Record of Decision following a review of
public comments received on the Proposed Plan and supporting documents included in
the Administrative Record. Significant public comments received, and responses to those
comments, are included in the Responsiveness Summary in Part III of this ROD.

A. Overall Protection of Human Health and the Environment

A primary reguirement of CERCLA is that the selected remedial alternative be protective
of human health and the environment. A remedy is protective if it reduces current and potential
risks to acceptable levels under the established risk range for each exposure pathway at the

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Site.

The remedy selected previously in the Record of Decision ("ROD") for OU-1 reduces the
current and potential risks associated with the buried waste and contaminated soil at the Site
by requiring the construction of either a multilayer cap or an erosion cap over the contaminated
areas. The multilayer cap will prevent rain water from coming in contact with the buried waste
and reduce the migration of contanimants to the groundwater. The OU-1 ROD requires
groundwater monitoring to evaluate the effectiveness of the multilayer cap in controlling the
source of the contamination.

Alternatives 2 and 3 in this ROD will both reduce the potential risks associated with
use of contaminated, groundwater at the Site and are protective of human health and the
environment. Both alternatives will immediately reduce the potential for exposure to the
contaminated groundwater by requiring institutional controls to prevent use of the groundwater
at the Site. These alternatives further protect human health and the environment by reducing the
contaminant levels in the groundwater over time. Alternative 2 does so through an active
extraction and treatment system while Alternative 3 relies on natural attenuation processes to
achieve acceptable levels. Alternative 3 requires implementation of an active extraction and
treatment system if the monitoring demonstrates that natural attenuation cannot achieve the
acceptable cleanup levels. Both alternatives require monitoring of the groundwater to ensure
that acceptable contaminant levels are achieved.

Alternative 1 (No Action) is not protective of human health and the environment because
this alternative does not require institutional controls to prevent the possibility of exposure
to the contaminated groundwater and does not require groundwater monitoring to ensure that the
contamination is reduced to acceptable levels. Because this alternative does not meet the
threshold criteria of protection of human health and the environment, it will not be considered
further in this analysis.

B. Compliance with Applicable or Relevant and Appropriate Requirements ("ARARS") 1

[1 Under Section 121(d) of CERCLA, 42 U.S.C. ° 9621(d), and EPA guidance, remedial actions
at CERCLA sites must attain legally applicable or relevant and appropriate federal and
promulgated state environmental standards, requirements, criteria and limitations which are
collectively reffered to as "ARARs, "unless such ARARs are waived under Section 121(d)(4) of
CERCLA, 42 U.S.C. ° 9621(d)(4).]

Any cleanup alternative considered by EPA must comply with all applicable or relevant
and appropriate federal and state environmental requirements. Applicable requirements are those
substantive environmental standards, requirements, criteria, or limitations promulgated under
federal or state law that are legally applicable to the remedial action to be implemented at the
Site. Relevant and appropriate requirements, while not being directly applicable, address
problems or situations sufficiently similar to those encountered at the Site that their use is
well-suited to the particular site.

Alternatives 2 and 3 would comply with the following ARARs, as appropriate:

Chemical-Specific ARARs

Groundwater Under the Safe Drinking Water Act, 42 U.S.C. °° 300 f to 300 j-26, and its
implementing regulations, 40 C.F.R. Part 141, MCLs are established for acceptable
concentrations of contaminants in public drinking water supplies. EPA considers the MCLs for
benzene, tetrachloroethane, 1,1,1-trichloroethane, toluene, xylenes (Table 1) and Secondary
MCLs for aluminum, cadmium, copper, iron, silver, zinc (Table 3) to be relevant and appropriate

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requirements for groundwater at the Site. The goal of Alternatives 2 and 3 is to achieve these
MCLs at the property line. The long-term monitoring program for Alternatives 2 and 3 will also
include monitoring the Coraopolis public water supply to ensure that contaminated groundwater
from the Site does not impact the water supply.

Under the Land Recycling and Environmental Remediation Standards Act of Pennsylvania, (Act
2), Medium-Specific Concentrations ("MSCs") for contaminants in groundwater are established
at 25 Pa.Code Chapter 250, Section 250.304. For any contaminants of concern for which an
MCL does not exist, the MSC would be applicable.

Surface Water: Water quality standards have been established for acceptable concentrations of
contaminants in Commonwealth waters and are set forth in 25 Pa. Code Chapter 93. In addition,
water quality criteria fore toxic substances are set forth in 25 Pa Code Chapter 16. The long-
term monitoring program for Alternatives 2 and 3 will include monitoring to ensure that the
river is not adversely impacted by migration of contaminants from the Site. On-site extraction
and treatment of groundwater under Alternative 2 and monitored natural attenuation under
Alternative 3 will reduce migration of contaminants to levels that achieve water quality
standards and water quality criteria for toxic substances.

Action-Specific ARARs

Discharge of Treated Groundwater The groundwater extraction and treatment component of
Alternative 2 involves discharging treated water from the groundwater treatment system into
surface water, namely the Ohio River. The more stringent of the substantive requirements of the
Clean Water Act and the Pennsylvania Clean Streams Law regarding discharges to surface
waters would be applicable to such discharges, including 40 C.F.R. Part 122 (National Pollutant
Discharge Elimination System), 40 C.F.R. Part 131 (Water Quality Standards), 25 Pa. Code
Chapter 92 (NPDES: regarding establishment of discharge limits and monitoring) and 25 Pa.
Code Chapters 16 and 93 (Water Quality Standards: regarding water quality criteria which must
be used in the development of the discharge limits).

Groundwater Storage: Temporary storage requirements set forth in 25 Pa. Code Sections
129.56-57 are relevant and appropriate to the temporary storage of pumped groundwater prior to
removal of VOCs by the air stripper under Alternative 2.

Hazardous Waste Generation: Alternative 2 may result in the generation of wastes that would
be regulated under current hazardous waste regulations. Any hazardous waste generated must be
handled consistent with the requirements of 25 Pa. Code Chapter 262 Subchapter A (relating to
hazardous waste determination and identification numbers), and 25 Pa. Code Chapter 264
subparts G, I and J (relating to storage of generated hazardous wastes in containers or tanks).

C. Reduction of Toxicity, Mobility, or Volume through Treatment

Section 121(b) of CERCLA, 42 U.S.C. Section 9621(b), establishes a preference for
remedial actions which include treatment that permanently and significantly reduces the
toxicity, mobility, or volume of contaminants, Alternative 2 requires groundwater extraction and
treatment to reduce die toxicity, mobility and volume of contaminants at the Site. Alternative 3
relies on natural attenuation processes to reduce the toxicity, mobility and volume of
contaminants in groundwater at the Site. Both alternatives are expected to require approximately
30 years to reduce concentrations to acceptable levels.

D. Implementability

This evaluation criterion addresses the difficulties and unknowns associated with

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implementing the cleanup technologies associated with each alternative, including the ability
and time necessary to obtain reguired permits and approvals, the availability of services and
materials, and the reliability and effectiveness of monitoring. The groundwater extraction and
treatment technologies reguired under Alternative 2 are readily available; however, the
hydrogeologic conditions at the Site may make it difficult to effectively contain the plume of
groundwater contamination. The ability to pump water from the contaminated plume beneath
Neville Island without pumping large volumes of water from the Ohio River is guestionable.
Additional studies to evaluate the ability to effectively extract groundwater at the Site would
be performed during the remedial design. Alternative 3 can be readily implemented because this
alternative relies an natural processes currently taking place at the Site to reduce the
groundwater contamination to acceptable levels.

E. Short-Term Effectiveness

Alternative 2 may potentially pose some short-term risks to workers and/or trespassers
during construction and operation of the extraction and treatment system and during monitoring
activities at the Site. Alternative 3 would pose fewer short-term risks because construction and
operation of an extraction and treatment system is not reguired. Short-term risks under either
alternative would be low and can be readily minimized using standard safety measures.

F. Long-term Effectiveness and Permanence

Alternatives 2 and 3 provide a permanent and effective long-term remedy, EPA assumes
that if groundwater from the contaminated plume can be pumped effectively at the Site,
Alternative 2 would attain the MCL for benzene along the shoreline of Neville Island within 30
years. Alternative 2 has the potential to achieve the benzene MCL in less time than Alternative
3 by actively pumping and treating the groundwater assuming that groundwater from the
contaminated plume can be effectively extracted.

To estimate the time reguired to attain the MCL for benzene under Alternative 3, the
data collected during the RI and the OU3 study were used in three-dimensional fate and
transport models to predict the rate of natural attenuation occurring at the Site. The
modeling results indicated that the benzene concentrations may be reduced to the MCL of 5
ppb at the shoreline (i.e., the point of compliance) within approximately 15 years. The
modeling further indicates that the benezene concentrations can achieve the MCL across the
entire Site in approximately 60 years. Based on this modeling, EPA estimates that benzene
levels will comply with the MCL at the shoreline in less than 30 years following capping of
the wastes. The mobility of the plume will be reduced by implementing the OU-1 ROD.
The multilayer cap will create an impermeable barrier to reduce the infiltration of surface
water through the concentrated pockets of waste buried at the Site. The OU-1 ROD reguires
monitoring to ensure that migration of contaminants from the source areas to the groundwater
is reduced. Alternative 3 in this ROD reguires additional monitoring to ensure that natural
attenuation process will effectively reduce the contaminant levels in the existing plume to
acceptable levels. If the contaminant concentrations do not decrease and levels remain that
pose an unacceptable risk to human health or the environment, active extraction and
treatment of the groundwater would be reguired under Alternative 3.

G. Cost

The cost of each alternative includes the calculation of direct and indirect capital costs
and the annual operation and maintenance ("O&M") costs, both calculated on a present
worth basis. The total present worth cost of Alternatives 2 and 3 has been calculated for
comparative purposes and is presented in Table 10. Alternative 2 is substantially more
expensive than Alternative 3.

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     Direct capital costs include costs of construction, equipment, building and services,
and waste disposal. Indirect capital costs include engineering expenses, start-up and
shutdown, and contingency allowances. Annual O&M costs include labor and material;
chemicals, energy, and fuel, administrative costs and purchased services; monitoring costs;
costs for periodic Site reviews  (every five years); and insurance, taxes, and license costs.
For cost estimation purposes, a period of 30 years has been used for O&M.

     The actual duration of operation for the groundwater extraction and treatment system
will depend on the system's ability to successfully limit off-site migration of Site-related
contaminants. The actual cost for each alternative is expected to be in a range from 50
percent  (50%) higher than the costs estimated to 25 percent  (25%)  lower than the costs
estimated. The evaluation was based on the FS cost estimates, as modified by EPA.

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                              Table 10
                    Estimated Cost of Alternatives

                              Total Present Worth Cost

Alternative
                   Years 1-3      Years 4-30           Total

2                  $1,700,000       $8,290,000          $9,990,000

3                   $200,000         $810,000           $1,010,000

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H. State Acceptance

PADEP has reviewed this Record of Decision and comments received from PADEP have been
incorporated as appropriate. PADEP has provided support to EPA throughout the Superfund process
at this Site. PADEP concurs with the remedy selected in this ROD.

I. Community Acceptance

EPA has considered the comments received during the public comment period on its
preferred remedial alternative presented in the Proposed Plan. These comments are summarized
and responses are provided in Part III (Responsiveness Summary) of this Record of Decision. In
general, the community and NLC support the preferred alternative.

IX. SELECTED REMEDY AND PERFORMANCE STANDARDS

Based on a comparison of the nine evaluation criteria for the alternatives considered in
this ROD, EPA has selected Alternative 3: Monitored Natural Attenuation and Institutional
Controls to address OU-3 at the Site. Alternative 3 meets the threshold criteria of overall
protection of human health and the environment and compliance with ARARs. In considering the
balancing criteria, EPA believes Alternative 3 can be readily implemented, achieves long-term
effectiveness and permanence at a reasonable cost, minimizes the short-term impacts, and
effectively reduces the mobility of Site contaminants. The reguirements for implementing
Alternative 3 are as follows:

A. Natural Attenuation Reguirements

1. Natural attenuation processes shall be allowed to reduce the concentrations of benzene
and 2,4,6-trichlorophenol in the groundwater plume at the Site to levels that protect
human health and the environment. EPA has determined that the appropriate cleanup
levels for benzene and 2,4,6-trichlorophenol are 5.0 and 61 ppb, respectively. The
cleanup level for benzene is based on the current Safe Drinking Water Act MCL for this
contaminant. The cleanup level for 2,4,6-trichlorophenol is based on EPA Region III
risk-based concentration for tap water presenting the cancer risk of 10 -5.

2. A statistical evaluation of the monitoring data shall be performed every three years,
unless EPA determines that more freguent analysis is reguired, to determine the rate at
which natural attenuation processes are reducing contaminant levels at this Site.

3. If EPA determines that (1) the natural attenuation processes are not reducing contaminant
concentrations at a rate that will achieve the cleanup levels in a reasonable time period
(approximately 30 years) and (2) the contaminant levels present pose an unacceptable
risk to human health and the environment, construction and operation of a groundwater
extraction and treatment system at the Site shall be reguired.

B. Monitoring Reguirements

1. Monitoring shall be performed to measure changes in contaminant concentrations in the
groundwater plume at the Site until the cleanup levels have been achieved. The exact
location and number of groundwater monitoring points shall be determined by EPA
during the Remedial Design process. Monitoring points shall be located along the
property line on the Back Channel side of Neville Island, beneath the Back Channel at
the downgradient edge of the benzene plume, beneath the Main Channel, and at the
Coraopolis public water supply well nearest to the Site.

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2. Samples shall be collected from the monitoring points on a quarterly basis. Samples
from the monitoring points located on Neville Island and the Coraopolis public water
supply well shall be analyzed for VOCs (Table 1) , SVOCs (Table 2), metals (Table 3)
and natural attenuation parameters including dissolved oxygen, nitrate, manganese II,
iron II, sulfate, methane, redox potential/Eh, alkalinity, and pH. Monitoring points
located beneath the Main and Back Channels shall be analyzed for, at a minimum,
benzene, 2,4,6-trichlorophenol and the natural attenuation parameters.

3. If EPA determines that a statistical evaluation of the groundwater data collected for the
first twelve quarters of the monitoring program demonstrates that natural attenuation
processes are reducing the contaminant concentration at a reasonable rate and the
contaminants are not migrating, EPA may reduce the frequency of sample collection and
may limit the scope of analysis required. If EPA determines that contaminant levels are
not decreasing at a reasonable rate or that contaminant migration is occurring, EPA may
increase the frequency of sample collection and may require additional analysis.

C. Institutional Controls

1. Deed restrictions shall be placed on Site property to prohibit use of the groundwater until
cleanup levels have been achieved.
2. Warning signs shall be posted along Site shoreline to warn fishermen not to eat fish
caught in the area. These signs shall be properly maintained as long as fish in the Ohio
River are found to have high levels of contaminants that can cause adverse human health
effects. The wording of these signs shall be approved by EPA, in consultation with
PADEP, during the Remedial Design.

X. STATUTORY DETERMINATIONS

This remedy satisfies the remedy selection requirements of CERCLA and the NCP. The
remedy is expected to be protective of human health and the environment, complies with ARARs, is
cost effective, and utilizes permanent solutions. The remedy does not include treatment as a
principal element of the remedy because natural attenuation processes can reduce contaminant
concentrations to levels that protect human health and the environment within a reasonable time
frame. Additionally, once the remedy (the cap) for OU-1 is completed there will be no risk of
direct exposure to the Site-related contaminants. The following is a discussion of how the
selected remedial action addresses the statutory requirements.

A. Overall Protection of Human Health and the Environment

The selected remedy will provide adequate protection of human health and the environment by
stabilizing the plume of contaminated groundwater beneath the multilayer/erosion cap. This
action will reduce the carcinogenic risk from exposure to contaminated groundwater to
commercial, industrial, and recreational Site users to within the acceptable EPA risk range of
10 -4 to 10 -6, and will reduce the Hazard Index to less than one for non-carcinogenic risks.
This remedy will also minimize further migration of contaminated groundwater into surface water
and sediment.

B. Compliance with Applicable or Relevant and Appropriate Requirements ("ARARS")

The selected remedy will comply with the Safe Drinking Water Act MCLs, and the Act 2
MSCs for any contaminant for which an MCL does not exist, and the Pennsylvania water quality
standards and water quality criteria for toxic substances.

C. Cost Effectiveness

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EPA has determined that the selected remedy most effectively addresses contaminated
waste/soils while minimizing costs. The estimated present worth cost is $1,010,000. Other
alternatives were either less expensive, but ineffective, or more expensive, but only marginally
more protective than the selected remedy.

D.   Utilization of Permanent Solutions and Alternative Treatment (or Resource Recovery)
Technologies to the Maximum Extent Practicable

     EPA has determined that the selected remedy represents the maximum extent to which
permanent solutions and alternative treatment technologies can be utilized in a cost-effective
manner at the Site. The selected remedy does not reguire treatment because the treatment
alternative considered  (groundwater extraction and treatment)  would achieve only marginal
additional protection for ten times the cost.

E.   Preference for Treatment as a Principal Element

     As stated above, the selected remedy does not reguire treatment because the treatment
alternative considered  (groundwater extraction and treatment)  would achieve only marginal
additional protection for ten times the cost.

XII. DOCUMENTATION OF SIGNIFICANT CHANGES

     This ROD did not change the preferred remedial alternative, Alternative 3, identified in
the Proposed Plan to address groundwater contamination at the Site.

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                               RECORD OF DECISION
                                 OHIO RIVER PARK

                          PART III -RESPONSIVENESS SUMMARY

     This responsiveness summary is divided into the following sections:

      D   A section on background information that provides a brief history of community
          involvement;
      D   A section on major issues and concerns that provides a summary of major
          concerns expressed by the local community during the public meeting and in
          several letters received by EPA during the public comment period;
      D   A section on technical and legal issues that responds to specific comments
          pertaining to technical and legal issues, which were raised during the public
          comment period.

I.    BACKGROUND

     On February 25, 1998, EPA announced the public comment period and published its
preferred alternative for Operable Unit 3 ("OU-3") of the Ohio River Park Site located on
Neville Island in Allegheny County, Pennsylvania. To obtain public input on the Proposed
Remedial Action Plan  ("Proposed Plan")  for OU-3, EPA held a public comment period from
February 25, 1998, to March 26, 1998. EPA nofified the public of the March 17, 1998, public
meeting and announced the public comment period in display ads placed in the February 25 and
March 11 editions of the Pittsburgh Tribune Review, the Coraopolis Record and the Pittsburgh
Post-Gazette. In addition, EPA has established a Site information repository at the Coraopolis
Memorial Library. The repository contains the Proposed Plan, the Remedial Investigation, the
Baseline Risk Assessment, the Ecological Risk Assessment, the Feasibility Study, the Intrinsic
Remediation Demonstration Study, and other relevant documents. EPA's Administrative Record
for the Site, which includes the key documents the Agency used in selecting the Site remedy,
also is housed at the repository. EPA also prepared a Site fact sheet and distributed it to
individuals on the Site mailing list and in attendance at the public meeting. The fact sheet
included a summary of the Proposed Plan.

     Those in attendance at the meeting included local area residents; state, county, and local
officials; news media representatives,  representatives from EPA; and representatives from
companies interested in the Site activities and cleanup decisions. EPA briefed local officials
prior to the public meeting. EPA carefully considered state and community acceptance of the
remedy prior to reaching the final decision regarding the remedy.

II.  MAJOR ISSUES AND CONCERNS

A.    OU-1 Remedial Action

1.    A resident asked whether any tests to detect radioactive material had ever been performed
     at the Site and inguired whether the cap was selected in response to radioactive
     contamination.

Response: No historical records were identified that indicate radioactive material was disposed
of at the Site. As a standard protocol, however, EPA contractors perform  radiation surveys as
part of their health and safety monitoring when conducting investigation activities at hazardous
waste sites. The cap was not selected to address radioactive contamination. The cap was selected
to (1)  stop surface water from infiltrating the contaminated soil below, and  (2) prevent direct
contact with the contaminated soil.

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2. Another resident wrote a letter stating that in 1979, when the construction for the
original park started, his family became sick from the fumes released during soil
excavation at the Site. The resident expressed concern that the current construction may
release fumes and make his family sick again.

Response: The contaminated soil and debris will not be excavated as part of the OU-1 remedial
action. Instead, a cap will be placed over the contaminated soil and debris to prevent any
direct contact with the contaminated soil at the Site. During cap installation and other onsite
construction projects, the ambient air will be monitored to ensure that contaminants are not
being released. Best management practices for dust suppression will also be implemented at the
Site.

3. A resident asked of what type of material the cap is made.

Response: The final design of the multilayer cap has not been submitted to EPA for approval.
However, the cap will consist of a RCRA cap overlain by an erosion control cover. RCRA caps are
typically constructed with multilayered geotextiles or clay soil. Erosion control covers are
made of approximately three feet of clean soil.

4. A resident asked how long it would take to install the cap.

Response: Neville Land Company plans to begin construction of the cap during the summer of 1999.
The cap remedial design documents were approved on September 8, 1998, and the cap may be
completed by October/November 1998.

5. A resident expressed concern about whether the multilayer cap was designed to withstand
the floods that occur on Neville Island.

Response: Neville Land Company designed the cap and the erosion control devices to withstand a
100-year flood event.

6. One resident asked whether the existing oil derrick is a significant source of
contamination at the Site.

Response: There is no evidence from past sampling activities that the existing oil derrick is
contributing to Site contamination, Neville Land Company is currently in the process of closing
the oil derrick. This will be accomplished in accordance with all applicable local, state, and
Federal regulations.

7. Several residents expressed concern over EPA's decision not to remove all the
contaminated soil and debris from the Site.

Response: A variety of factors were considered and investigated during the remedial
investigation phase of the project. The most important consideration is to protect human health
and the environment from the Site contamination. The capping alternative protects human health
and the environment by preventing exposure to the buried wastes and contaminated soil. Since
this alternative is protective, EPA weighed the criteria to determine which alternative was the
best overall solution for the Site. EPA analysis of these criteria are included in the Record of
Decision issued for OU-1. Excavating and removing the contaminated material would cost
approximately 40 million dollars compared to approximately 8 million dollars for capping and
monitoring. In addition, excavating and removing the contaminated soil from the Site could
potentially expose Site workers, surrounding residents and the environment to the Site
contaminants.

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B. Natural Attenuation

1. Several residents asked what happens to the contaminated material in the groundwater
during the natural attenuation process.

Response: Natural attenuation is defined as naturally occurring processes in soil and
groundwater that act, without human intervention, to reduce the mass, toxicity, mobility,
volume, or concentration of contaminants present. In other words, the contaminated material in
the groundwater will degrade naturally over time. Studies performed by Neville Land Company, and
reviewed by EPA and the State, demonstrated that natural attenuation is occurring in the
groundwater at the Site.

2. A resident asked whether the cap would prevent any degradation of the contaminated soil
beneath it by not allowing any surface water to percolate through the contaminated
material.

Response: The cap may affect the rate at which the contaminants degrade. However, the cap will
prevent direct human contact with the contaminated soil and will eliminate the source of
groundwater contamination by preventing rain water from percolating through the contaminated
soil.

3. A resident asked why dissolved oxygen levels in the groundwater are higher offsite than
onsite.

Response: The dissolved oxygen values are not contamination values. The dissolved oxygen values
indicate that natural attenuation is occurring. The values onsite are lower because the
reactions that degrade the contaminants utilize the available dissolved oxygen in the
groundwater. The higher dissolved oxygen levels detected offsite represent naturally
occurring or background levels of dissolved oxygen in the groundwater.

C. Risk Evaluation

1 A resident asked why the Site is being cleaned up if, through natural attenuation, it will
clean itself in 30 years.

Response: Natural attenuation will only be able to reduce the contaminant levels in the
groundwater over time if no additional contamination is allowed to reach the aguifer. The
multilayer cap is needed at the Site to prevent further migration of contaminants that remain in
the buried waste and contaminated soil. Institutional controls are also needed to ensure that
the Site is not used improperly for residential development and that use of the groundwater is
prohibited. Finally, a monitoring program is necessary to ensure that natural attenuation
actually occurs in the manner predicted.

2. Several residents were concerned about the cancer risk posed by the contaminated material
at the Site and asked if a study had been performed to determine if there was a higher
incidence of cancer to residents living near the Site.

Response: No cancer study has been performed for the Site. However, a Baseline Human Health Risk
Assessment was conducted as part of the remedial investigation to determine the cancer and
noncancer risks posed to current and future users of the Site in the absence of Site
remediation. The Baseline Human Health Risk Assessment evaluated contaminated soil, sediment,
groundwater, and surface water exposure routes. Results showed that without the comtruction of a
cap, the cancer risk levels exceeded the acceptable levels specified in the National Oil and
Hazardous Substances Pollution Contingency Plan. However, the actions reguired by the OU-1

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Record of Decision and those required in this Record of Decision will reduce the cancer risk
levels associated with the Site to acceptable levels for daily recreational Site users, workers,
and trespassers.

3. Another resident agreed with EPA that the preferred alternative, Alternative 3, is
appropriate to clean up the Site, but felt that the Site is not the best place for a
recreational facility because of the risk of being exposed to Site contamination.

Response: After the cap, erosion cover, and institutional controls are in place, the risk to
human health and the environment from the Site contamination will be reduced to acceptable
levels specified in the National Oil and Substances Pollution Contingency Plan. A Baseline Human
Health Risk Assessment was performed for the Site to determine these risk levels, which are
reported in the Proposed Plan. According to the Risk Assessment report, the workers and
residents who use the new recreational facility will not be exposed to elevated risk levels
after the remedial acton is implemented.

D. Groundwater Monitoring Program

1. A local official inquired if the groundwater monitoring locations were close enough to the
Coraopolis water supply well field to provide adequate information on contaminant
migration to the Borough's drinking water supply.

Response: The groundwater monitoring program required in this Record of Decision was designed to
ensure that the Coraopolis public water supply is protected from Site contamination. The
monitoring program includes analysis of samples collected from monitoring points along the Back
Channel side of the island, beneath the Main and Back Channels of the Ohio River, and at the
Coraopolis public water supply well closest to the Site. This monitoring program will continue
until contaminants in the Site groundwater plume reach the required cleanup levels. The results
obtained from the monitoring program will allow EPA to determine whether contaminants are
migrating from the Site before the contamination could reach the Coraopolis well field.

2. A local official inquired what would happen if contamination from the Site was identified
in the Coraopolis water supply wells and who would be responsible for cleaning up the
contamination.

Response: If contaminants from the Ohio River Park Site are detected in the Coraopolis water
supply wells, the Record of Decision requires that an active groundwater extraction and
treatment system be installed at the Site to contain the contaminated groundwater and prevent
further migration of contamination from the Site. If Neville Land Company agrees in a consent
decree to implement the ROD for OU-3, they will be responsible for any further requirements. EPA
could issue a unilateral order requiring them to implement this ROD, or EPA could undertake the
required actions and seek to recover costs from the Site owner/operators.

3. A local official asked whether the contaminated groundwater could be avoided if new
Coraopolis water supply wells were installed upriver from the existing Coraopolis well
field.

Response: The groundwater modeling performed for OU-3 investigated increased pumping rates and
draw down from the existing Coraopolis well field. The modeling did not investigate alternate
well locations.

4. A resident asked who will be responsible for sampling the monitoring wells and what
laboratories will be used to analyze the samples.

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Response: EPA anticipates that Neville Land Company will agree to collect the water samples from
the monitoring wells. EPA representatives will also collect samples at a certain percentage of
the monitoring points to ensure that good guality data are being generated. An EPA-approved
laboratory will analyze the samples.

5.  A resident asked if contamination had been detected on residential property adjacent to the
    Site.

Response: No contamination has been detected on adjacent residential property.

6.  A resident inguired if the groundwater monitoring program proposed under Alternative 3
    includes an assessment of the drinking water pumped from the Coraopolis well field and
    whether such moruitoning is reguired to operate a public water supply system.

Response: Public water suppliers are reguired to routinely monitor the guality of water
provided to consumers under the Safe Drinking Water Act. The monitoring program reguired in this
Record of Decision will provide additional information to allow evaluation of whether
contaminants from the Ohio River Park Site are migrating toward the Coraopolis public water
supply well field. The drinking water sampling results collected from the Coraopolis wells will
be reviewed along with the data collected from the groundwater monitoring wells. This
information will be made available to Coraopolis to meet any public water supply system
reguirements.

7.  Residents from Coraopolis and Moon Township reguested copies of the groundwater
    monitoring data generated as part of the implementation of Alternative 3.

Response: The groundwater sampling results collected as part of the reguired monitoring
program will be made available to the public upon reguest from EPA.

E.  Decision Process

1.  A resident asked whether EPA had made a decision about the cleanup of OU-3 or if a
    decision would be made during the public meeting.

Response: EPA does not make a final decision on the appropriate remedy for a Site until after
the public has had an opportunity to comment on its recommendation. A public comment period on
the OU-3 Proposed Plan was held from February 25, 1998 to March 26,1998. EPA held a public
meeting on March 17, 1998 to provide the public an opportunity to comment on the Proposed Plan
directly to EPA. After these comments were received and reviewed, EPA, in consultation with
PADEP, made a decision on the appropriate cleanup alternative for OU-3. That decision is
documented in this Record of Decision.

2.  A resident asked whether EPA would allow the Neville Island residents to select the
    cleanup option that will best protect human health and the environment.

Response: According to the Superfund law, EPA must consider community acceptance as part of the
process for selecting a cleanup alternative. In order to reach as many local residents as
possible to comment on the OU-3 Proposed Plan, EPA advertised the public meeting in the
Coraopolis Record, the Pittsburgh Post-Gazette, and the Pittsburgh Tribune Review. EPA also
mailed over 250 fact sheets on the Proposed Plan to local residents. While community acceptance
is an important factor, it is only one of nine criteria that EPA must consider in selecting an
appropriate remedy. EPA makes the final remedy selection decision.

3.  A resident asked why construction is proceeding at the Site if all decisions have not yet

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    been made.

Response: The construction that is currently underway at the Site is for the new recreational
facility being built on an uncontaminated portion of the Site. Work is also beginning on the
multilayer cap installation reguired as part of the remedy selected in the OU-1 Record of
Decision issued on September 30, 1996. The OU-1 remedy includes a multilayer cap, surface water
runoff controls, monitoring, and institutional controls.

F.  Property Acguisition

1.  A resident asked whether Neville Land Company has purchased or plans to purchase any
    private or commercial property adjacent to the Site.

Response: EPA does not currently anticipate that Neville Land Company will need to purchase any
property to implement the cleanup at the Site.

G.  Positive Responses

1.  Two state representatives expressed in writing their support for EPA's Proposed Plan and
    the redevelopment of the Site as a recreational facility. During the public meeting, several
    local officials from Neville Township stated their appreciation for EPA's and PADEP's
    efforts and dedication to ensure proper site cleanup and reutilization. The Cornell School
    District stated their support for EPA's Proposed Plan and appreciation of EPA's attention
    to the ongoing development of the Neville Island Sports Center.

Response: No response reguired.

III. TECHNICAL AND LEGAL ISSUES

     This section provides responses to guestions reguiring a higher level of technical detail.
Some of these guestions were asked at the March 17, 1998 public meeting, however, most of them
were received by mail, e-mail, or telephone during the public comment period.

A.   General Groundwater Monitoring

1.   PADEP reguested that EPA's Proposed Plan include a thorough monitoring plan with
     specific triggers for contingency measures to determine whether natural attenuation will
     effectively protect human health and the environment.

Response: The remedy reguirements identified in Section IX of this Record of Decision provide an
appropriate level of detail to establish how successful implementation will be measured. The
exact location and number of monitoring points will be determined during the remedial design
process, however, the Record of Decision states which areas will be monitored. EPA Will provide
the State with the opportunity to review and comment on the remedial design documents prior to
EPA' s approval.

2.   PADEP expressed concern over the proposed number and location of the monitoring wells
     identified for Alternatives 2 and 3 in the Proposed Plan. PADEP feels that monitoring only
     the Back Channel will not adeguately evaluate the effectiveness of the cap, changes in the
     water level and flow direction following installation of the cap, or the effectiveness of
     natural attenuation in eliminating groundwater contamination at the Site.

Response: EPA agrees with PADEP that additional monitoring points would provide more accurate
data on the natural attenuation processes occurring at the Site and the effectiveness of the

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remedy. EPA believes, however, that the monitoring program described in the Proposed Plan would
provide information sufficient to identify general trends in contaminant levels in the
groundwater plume and warn of potential threats to human health and the environment. Monitoring
is not limited to the Back Channel, but includes a monitoring point beneath the Main Channel and
at the Coraopolis well field. The Record of Decision does not establish the exact number and
location of monitoring points. This information will be determined during the remedial design.
EPA will provide PADEP with the oppontunity to review and comment on the remedial design
documents prior to EPA's approval.

B. Groundwater Monitoring Parameters

1. Neville Land Company would prefer not to use the analytical detection limits for
contaminants that are not detected during analysis when evaluating the monitoring results.
NLC believes that using the analytical detection limits in the statistical analyses will
lead to erroneous results, NLC suggests allowing a competent statistician to select the
appropriate statistical tests and establish their data input needs.

Response: EPA Region Ill's Guidance on Handling Chemical Concentration Data Near the Detection
Limit in Risk Assessments, dated November 4, 1991, will be used in determining how to handle
sampling results that are below the detection limit. In general, a value of one-half the
analytical detection limit is recommended. EPA has adopted this conservative approach to ensure
that actions taken are protective of human health and the environment. Allowing a "competent"
statistician to select the "appropriate" statistical test would create inconsistency in data
analysis and lead to a complicated and prolonged remedial design review process as NLC, EPA, and
PADEP statisticians debate the merits of different approaches.

2. Neville Land Company recommended defining the analytical parameters for the monitoring
program identified in Alternative 3 during the final design process.

Response: While EPA agrees that additional information may be needed to appropriately
determine the exact number and location of monitoring points, EPA had determined that the
studies performed during the intinsic remediation demonstration study have adeguately
documented the analytical parameters that should be monitored to evaluate the ongoing natural
attenuation processes at the Site. Therefore, this Record of Decision does identify the
analytical parameters reguired in the monitoring program. Note, however, that EPA is willing to
reevaluate both the freguency of sample collection and the analytical parameters reguired after
the first three years of data collection.

3. Neville Land Company recommended that future monitoring program modifications for
Alternative 3 be based on actual needs at the time that they are made.

Response: See previous response.

4. PADEP recommended that the monitoring list of parameters for Alternative 3 include all
contaminants of concern. This includes semi-volatile organic compounds and dissolved
metals. PADEP believes the list of parameters should be identical for a monitoring wells
for statistical evaluation. After three years of monitoring, Neville Land Company could
then petition EPA to remove certain parameters if warranted by statistical evaluation.

Response: EPA has determined that samples collected from monitoring points on the Site
shoreline along the Back Channel should be analyzed for the full range of potential contaminants
(i.e., VOCs, SVOCs, and metals) as well as the natural attenuation parameters. EPA will consider
reducing the analytical parameters reguired at these monitoring points after the first three
years of sample collection. At monitoring locations not currently impacted by the Site

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groundwater plume, EPA has determined that a reduced set of parameters is appropriate. If
conditions at the Site change, EPA can reguire that additional analytical parameters be added to
the monitoring program.
5. PADEP noted that the contaminants of ecological concern in the groundwater, which are
identified on page 11 of the Proposed Plan, should correspond with the list of parameters
that will be monitored.

Response: Samples collected from the Site shoreline along the Back Channel will be analyzed for
VOCs, SVOCs, and metals, Analyses for pesticides and PCBs are not reguired because these
parameters were not identified as contaminants of concern in the groundwater.

6. PADEP expressed concern about the overall duration of the monitoring period.
Specifically, PADEP feels that the overall duration should be clearly defined for each
alternative of the Proposed Plan.

Response: The selected remedy identified in Section IX of the Record of Decision reguires that
monitoring be performed until the groundwater cleanup levels for the Site are achieved.

7. PADEP reguested that all natural attenuation indicator parameters (dissolved oxygen,
nitrate, manganese II, iron II, sulfate, methane, redox potential/Eh, alkalinity, and pH)
be included in the monitoring parameters for Alternative 3. PADEP recommended that the
list of natural attenuation parameters for Alternative 3 be constant throughout the entire
monitoring period. Natural attenuation is a continuing process and various natural
attenuation parameters may be depleted or increased in different areas of the
groundwater plume at different times. For statistical comparisons and evaluations of
natural attenuation, it is important to have a uniform list of natural attenuation
parameters.

Response: EPA included the list of natural attenuation parameters reguested by PADEP. EPA will
consider changes to the list of parameters following the first three years of sample collection
at the Site. The impact on statistical comparisons of datasets will be a factor considered in
determining whether to change the list of reguired natural attenuation parameters.

8. PADEP expressed concern over the use of sulfate as a tracer and a natural attenuation
indicator for Alternative 3. Sulfate has been historically related to wastes dumped at the
Site, which should be taken into consideration.

Response: PADEP's concerns over the historical presence of sulfur wastes at the Site will be
taken into account during future monitoring. Presence of sulfur wastes at the Site, however, is
considered by EPA as a modifying factor, which should not exclude sulfate from the list of
natural attenuation parameters. EPA was aware of the distribution of sulfur wastes at the Site
during its review of the intrinsic remediation demonstration study. Nevertheless, EPA considers
sulfate an important parameter in the evaluation of natural attenuation at the Site.

C. Intrinsic Remediation Demonstration Study

1. PADEP expressed concern that the intrinsic remediation demonstration study did not
adeguately determine the actual mass loading of the contaminants of concern to the Ohio
River and the Back Channel. The actual mass loading should be computed in
accordance with PADEP reguirements for surface water instream criteria set forth at 25
Pa. Code 250.309.

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Response: More thorough evaluation of mass loading is presented in the Feasibility Study. This
study provides the data that water guality in the Ohio River is not impaired by the additional
contaminants of concern. EPA agrees that the intrinsic remediation demonstration study
selectively addresses some aspects of the mass loading. This approach is, however, sufficient to
issue the ROD pertaining to natural attenuation of the groundwater.

2. PADEP expressed concern over the aguifer narrative in the Proposed Plan and believes
that the inference that contaminated Site groundwater is not moving towards the
Coraopolis well field, but rather follows the gradient of the Ohio River, is not
substantiated by the intrinsic remediation demonstration study potentiometric maps or the
concentration contour maps. PADEP asserts that the gradient of the Ohio River is not
the only influence on groundwater movement at the Site. PADEP agrees that
groundwater appears to be discharged to the Back Channel and/or is naturally attenuated
or diluted before it contacts the well field. However, PADEP believes that the intrinsic
remediation demonstration study did not address the degree to which discharge/dilution
versus biodegradation/natural attenuation is acting as the predominant factor in
protecting the well field.

EPA Response:

EPA based its decision on the intrinsic remediation study, submitted by Neville Land Company,
which was verified by EPA expert, John Wilson, Ph.D. of the Robert S. Kerr Environmental
Research Laboratory in Ada, Oklahoma. Dr. Wilson used his own modeling program to check the pace
of natural attenuation at the Site and concurred with the conclusions of the intrinsic
demonstration study.

3. PADEP guestioned the validity of statements in the Proposed Plan which indicate that
the contaminant plume will be stabilized through capping and natural attenuation.
PADEP feels that the implied message is that the plume will be stabilized and
contaminant discharge to the river will stop. Since the intrinsic remediation
demonstration study did not include an analysis of what the Site is discharging to the
river, PADEP contends that any definitive statements on the reduction or elimination of
contaminant discharge to the river cannot be supported.

Response: EPA does not consider the statement in the Proposed Plan to be "definitive". The
entire issue of natural attenuation is based on historical data, selective sampling, modeling,
and experts opinions. It is therefore possible that the results of long-term monitoring may
differ from scientific predictions. Further sampling and evaluations would narrow the margin of
error; however, EPA considers the existing data to be adeguate to make the decision expressed in
the ROD.

D. Other

1. Neville Land Company recommended removing the discussion concerning the need to
include a warning sign to fisherman. A reguirement relating to such signage has already
been incorporated into the Record of Decision for OU-1, and available data does not
confirm or suggest that the Site has had any actual impacts upon fish within the Ohio
River. Therefore, Neville Land Company believes it is inappropriate for the warning
sign to be a reguirement in the Record of Decision for OU-3.

EPA Response: EPA agrees that the institutional control reguirements in Section IX.C of the
Record of Decision are the same as those reguired under Section X.H. of the OU-1 Record of
Decision. However, EPA has included these reguirements in this Record of Decision as well to
ensure that these controls are maintained throughout the duration of the actions reguired in

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both Records of Decision.

2. PADEP recommended that the Commonwealth's Act 2, The Land Recycling and
Environmental Remediation Standards Act, and 25 Pa. Code Chapter 250, Section
250.304 (Regulations for Administration of the Land Recycling Program (Act 2)) be
included as chemical-specific ARARs.

EPA Response: EPA included the Act 2 medium-Specific concentrations ("MSCs") for groundwater as
Chemical Specific ARARs for any contaminant of concern for which an MCL under the Safe Drinking
Water Act does not exist.

3. PADEP disagrees with figures in the Proposed Plan which show that the benzene plume
is shrinking. PADEP asserts that these figures are based on analytical results from 1981,
1984, 1987, and 1993, and represent benzene concentrations in different wells and
different zones from various monitoring events. PADEP does not, therefore, believe that
the figures should not be portrayed as definitive depictions of the benzene plume.

Response: The figures presented in the Proposed Plan and in this Record of Decision include the
compilation of currently available data. The monitoring results presented in these figures serve
general investigation purposes and the figures were generated to evaluate the natural
attenuation processes occurring at the Site, The phenomenon of natural attenuation had not yet
been recognized when these data were collected. EPA does not consider this data as the
definitive presentation of the historical limits of the benzene plume but rather as one of many
documents supporting a finding that natural attenuation is occurring at the Site.

4. PADEP indicated that the Commonwealth's reguirements at 25 Pa. Code Chapter 16,
Water Quality Toxics Management Strategy, and 25 Pa. Code Chapter 93, Water Quality
Standards, should be included as chemical-specific ARARs for the Site.

EPA Response: EPA included these ARARs as identified in the ROD.

5. PADEP guestioned the ownership of the property as stated in the Proposed Plan.
Similarly, PADEP is not convinced that a portion of the property that was never owned
by Neville Land Company could be transferred to Neville Land Company.

Response: The Neville Land Company did not recommend any changes to the discussion of their
ownership of the Site presented in the Proposed Plan. Therefore, EPA did not alter this language
in this Record of Decision. During EPA's investigation of the Site, EPA perfonned a title search
to determine the ownership of the Site. On August 21, 1997, NLC forwarded to EPA a copy of the
deed from Allegheny County, dated May 12, 1997, transferring title for the remaining parcel to
NLC.

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