PB94-964010
EPA/ROD/R04-94/176
July 1994
EPA Superfund
Record of Decision:
Diamond Shamrock Landfill
Site, Cedartown, GA
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RECORD OF DECISION
SUMMARY OF REMEDIAL AL TERNATWE SELECTION
DIAMOND SHAMROCK LANDFILL SITE
CEDARTOWN, POLK COUNTY, GEORGIA
PREPARED BY
u. S. ENVIRONMENTAL PROTEC110N AGENCY
REGION IV
ATLANTA, GEORGIA
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DECLARATION
of the
RECORD, OF DECISION
SITE NAME AND LOCATION
Diamond Shamrock Landfill Site
Cedartown, Polk County, Georgia
STATEMENT OF BASIS AND PURPOSE
This decision document (Record of Decision), presents the selected
remedy for the Diamond Shamrock Landfili "Site, Cedartown, Georgia,
developed 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 (SARA), 42 U.S.C.
S 9601 et seq., and to the extent practicable, the National
Contingency Plan (NCP), 40 CFR Part 300.
This decision is based on the administrative record for the Diamond
Shamrock Landfill Site.
The State of Georgia concurs with the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from the Diamond
Shamrock Landfill Site, if not addressed by implementing the response
action selected in this Record of" Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, or
the environment. "
DESCRIPTION OF THE SELECTED REMEDY
This action is the final action planned for the Site. This
alternative calls for implementation of response measures which
protect human health and the environment. The action addresses
and ground water contamination at the Site.
will
source
The major components of the selected remedy include:
.
Implementation of deed restriction(s) or restrictive covenant(s)
to prevent ground water usage and drilling resulting in exposure
to ground water contaminants;
.
Completion and maintenance of Site access restrictions (fencing
and signage);
.
Ground and syrface water monit.oring program to confirm that
natural attenuation processes are effective and that contaminants
would not migrate;
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1-
.
Performance of five year reviews in accordance with Section 121(c)
of CERCLA to assure that human health and the environment continue
to be protected b¥ the remedy, that natural attenuation continues
to be effective, and whether ground water performance standards
continue to be appropriate; and,
.
Continued ground water monitoring upon attainment of the
performance standards at sampling" intervals to be approved by EPA.
The ground water monitoring program would continue until EPA
approves a five-year review concluding that the alternative has
achieved continued attainment of the performance standards and
remains protective of human health and the environment.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment,
complies with Federal and State requirements that are legally
applicable or relevant and appropriate, and is cost-effective.
Because the treatment of ground water was not found to be practicable
nor cost effective, this remedy does not satisfy the statutory
preference for remedies that employ treatment that reduces toxicity,
mobility, or volume as a principal element. Finally, it is determined
that this remedy utilizes a permanent solution and treatment
technology to the maximum extent practicable.
Because this remedy may result in hazardous substances remaining on-
site above health-based levels, a review will be conducted within five
years after commencement of the remedy to ensure that the remedy
continue to provide adequate protection of human health and the
environment. "
9riJkk; h1~ ~
JOHN H. HANKINSON, Jr., REGIONAL ADMINISTRATOR
S"-3-94
DATE
.
. .
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1.0
2.0
3.0
4.0
5.0
5.1
5.2
5.3
5.4
5.5
5.6
5.7
6.0
6.1
6.2
6.3
7.0
7.1
7.2
7.3
7.4
7.5
TABLE OJ! CON'l'BN'l'S
SITE LOCATION AND DESCRIPTION
. . . . .
. . . . . .
SITE H:I:STORY AND ENPORCEHEN'1' ACT:IV:I:TIES
. . . . . .
HIGHLIGHTS OF COMMUNITY PARTICIPATION
.......
SCOPE AND ROLB OF ACTION. . .
. . . . . .
. . . . .
SUMMARY OJ! S:I:TE CHARACTERISTICS. . . . . . . . . .
M:BTBOROLOGY . . . . . . . . . . . . . . . . . .
PHYSIOGRAPHY. . . . . . . . . . . . . . . . . . .
GBOLOGY . . . . . . . . . . . . . . . . . . . .
SOILS AND OVERBURDEN. . . . . . . . . . .
SURFACB HYDROLOGY.. . . . . . . . . . . . . .
HYDROGBOLOGY . . . . . . . . . . . . . . . . . .
SUMMARY OF SITE CONTAMINATION. . . . . . . . .
5. 7 .1 GROmm WATBR CHARAC'l'BRIZAT:rON . . . .
5 . 7 .2 SOIL CHARACTERIZATION'. . . . . . . .
5.7.2.1 SURFACB SO:rLS . . . . . . . . . . . .
5.7.2.2 'SUBSURFACB SOIL. . . . . . . .
5.7.3 SURFACB WATER CHARACTERIZATION
5 . 7 . 3 . 1 SEBP S'l'tJDY OJ! CEDAR CREEK. . . . . .
5.5.4 SEDIM:BNTS CHARACTERIZATION. . . . .
SUMMARY OF S:rTB !t:rSK . . . . . . . . . . . . . . . .
HUKAH HEALTH R:rSKS . . . . . . . . . . . . . . .
6 . 1 . 1 CONTAM:rNANTS OJ! CONCBRH (COCa)
6.1.1.1 COCa:rN GROUND WATER' . . . . . . . .
6. 1 .2 EXPOSURE ASSESSMENT. . . . . . . . .
6 . 1. 2 . 1 C1JRRBN'1' EXPOSURE' '.......
6 . 1. 2 . 2 FO'l'tJRB EXPOSURE. . . . . . . . . . .
6 . 1 .2 . 3 EXPOSURE POINT CONCBNTRAT:rONS . . . .
6 . 1 . 3 TOX:rCITY ASSBSSMENT . . . . . . . . .
6.1.4 R:rSK CHARAC'l'ERIZAT:rON. . . . . . . .
6.1.5 IDBNTIP:rCA'1'ION OP ONCBRTA:rNT:rBS
BNV:rRONMBN'1'AL ASSBSSMENT . .'. .. . . . . . . .
6 . 2 . 1 TERRESTRIAL. . .. . . . . . . . . .
6 . 2 . 2 AQtJATIC . . . . . . . . . . . . . . .
CONTAMINANTS OP CONCERN & PBRP'ORMANCB
STANDARDS. . . . . . . . . . . . . . . . . . .
DESca:rPTION OF ALTBRHAT:rvBS ............
ALTBRHAT:rvB GW-l :NO AC'l':rON . . . . . . .
ALTBRHAT:rvB GW-2: :rNSTI'1'tJT:rONAL CONTROLS AND
GROUND WATER HON:r'1'OR:rNG .... . . . . . .
AL'l'BRHAT:rvB GW-3: GROmm WATER COLLBCT:rON
WB~LS . . .. . . . . . . . . . . . . . . . . . .
AL'l'BRHA'1':rvB GW-4: GROUNDWATER COLLECT:rON
'l'RBNCRBS . . . . . . . . . . . . . . .
. . . . .
APPL:I:CABLE OR RELEVANT AND APPROPR1:ATB
REOtJ:rRBHBNTS (ARARa) . .' '. . . .. .
. . . .
i
1
4
5
5
7
7
7
8
9
10
11
12
14
18
18
20
27
27
27
30
31
31
32
33
34
35
36
37
39
42
46
46
48
49
50
50
50
51
53
54
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8.0
8.1
8.2
8.3
9.0
10.0
10.1
.10.2
10.3
10.4
10.5
11.0
SUMMARY OF THB COMPARATIVE ANALYSIS OF
ALTERNATIVES. . . . . . . . . . . . . . . . . . . .
THRESHOLD CRITERIA. . . . . . . . . . . . . . .
8 . 1 .1 OVERALL PROTECTION OF HOMAN HEALTH
AND THE ENVIRONMENT. . . . . . . . .
8 . 1 .2 COMPLIANCB WITH ARARS . . . . .
PRIMARY BALANCING CRITERIA.. . . . . . . .
8.2.1 LONG-'1'BRH BFFECTIVENESS AND
PERKANBNCB ..........
REDUCTION OF TOXI:CITY, MOBILITY, OR
VOLtJHB THROUGH 'l'RBATMBNT ......
8 .2 .3 SHORT-'l'BRH BFPBCTIVBNBSS ......
8 .2 .4 IHPLBHBNTABILITY. . . . . . . . . .
8 . 2 . 5 COST .............
MODIFYING CRITERIA. . . . . . . . . . . .
8 . 3 .1 STATE ACCEPTANCB ....
8 . 3 . 2 COHMUNITY ACCBPTANCB .....
8.2.2
SUMMARY OF SELBCTED REMEDY
. . . . .
. . . . .
STATUTORY DETERMINATION ...........
PROTECTION OF RUHAN HEALTH AND THE ENVIRONMENT .
ATTAINMENT OF THB APPLICABLB OR RELEVANT AND .
APPROPRIATB REOUIRBHBN'l'S CARDS).. . . . .
COST BFFECTIVENESS . . . . . . . . . . . . . . .
UTILIZATION OF PERHANEH'l" SOLUTIONS "1'0 "1'HB
HAXIHUH EXTENT PRACTICABLB . . . . . . . .
PREFERENCE FOR 'l'REA'l'MENT AS A PRINCIPAL
ELEHEN'l' . . . . . . . . . . . . . . . . . . . .
DOCOHEN'l'ATION OF SIGNIFICANT CHANGES
. . . . .
APPENDIX A: RESPONSIVENESS SOMMARY . . . . . . .
. . . .
. . . .
APPENDIX B: STATE OF GEORGIA CONCURRENCE LBTTBR
. . . .
. . . .
ii
59
61
61
62
62
62
63
63
63
64
65
65
65
65
68
69
69
70
70
71
71
72
76
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TABLE 5-1
TABLE 5-2
TABLB 5-3
TABLB 5-4
TABLB 6-1
TABLB 6-2
TABLB 6-3
TABLB 6-4
TABLB 7-1
TABLE 7-2
TABLE 7-3
TABLE 8-1
TABLB 9-1
LIST OF TABLES
StJHHARy OF SUBSTANCES DE'l'BC'l'BD IN GROmm WATER . . . . 15
StJHHARy OF SUBSTANCES DE'l'BCTBD IN SURFACE SOILS . . . . 19
StJHHARy OF SUBSTANCBS DETEC'l'BD IN SURFACB WATERS 28
StJHHARy OF SUBSTANCBS DBTBC'l'BD IN SBDIKBHTS . . . . . . 29
CON'l'AKJ:NAHTS OF CONCBRH &: BXPosmm POIH'l'
CONCENTRATIONS .. . . . . . . . . . . . . .
. . . . .
CON'l'AHINAHTS OJ' CONCB1\H TOXICITY ASSBSSKBH'l' .
. . . . .
StJHHARy OF UNACCEPTABLE RISK -- GROtJND WATER
%NG2S'l'IOR . . . . . . . . . . . . . . . . . . .
. . . .
StJHHARy OJ' REMEDY PBRP'ORHANCE STAHDARDS (GROtJND
WATER) ........................
POTENTIAL LOCATION SPECIFIC ARARs .
.....
. . . . .
POTENTIAL ACTION-SPBCIFIC ARAR,s . .
. . . . .
. . . . .
POTENTIAL CHEMICAL-SPECIFIC ARARS .
. . . . .
. . . . .
COMPARISON OF COSTS. . . . . . . . . .
. . . . .
StJHHARy OF HONI'1'ORING PBRP'ORHANCE STANDARDS
(GROtJHD WATER) ..............
. . . . . .
iii
33
39
41
50
55
56
58
64
68
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FJ:GURB 1-1
FJ:GtJRB 1-2
FJ:GtJRB 5-1
FJ:GURB 5-2
LOCA'1'ION HAP .
SI'1'B HAP . .
L:IST OF F:IG'ORBS
. . .
. . . . . .
. . . .
. . . . . .
. . . .
SI'1'B SAKPLING PLAN .
..........
TRENCH CLOStJRB AND SUBStJRFACB SAHPLING PLAN
iv
. . . .
. . . . .
. . . .
. . . . .
2
3
13
21
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FINAL
Record of Decision
Diamond ShaDU'OCk Landfill Site
Page 1
1.0
SITE LOCATION AND DESCRIPTION
The Diamond Shamrock Site comprises approximately 8 acres of land near the
northwest margin of the town of Cedar town, in Polk County, Georgia. The site is
located north of West Girard Avenue, adjacent to and east of Cedar Creek and is
owned by Henkel Corporation as shown in Figures 1-1 and 1-2.
The areas immediately surrounding the site include the Cedartown Wastewater
Treatment Plant approximately 300 yards north of the site and Henkel's wastewater
treatment plant (Henkel WWTP) to the east (south of the access road and
biotreatment cell areas). Beyond Henkel's WWTP to the east the land is primarily
residential with the closest residences about 700 feet away from the site. Land to the
south and east is largely residential with some commercial business and light
industry. Much of the area to the north and northwest is rural, although the
Cedartown wastewater treatment plant is located 300 yards to the north. The land
immediately to the west is Undeveloped and leads into predominately agricultural
and industrial areas. The nearest residence to the west is approximately 1,000 feet
from the site.
The property is primarily a meadow, becoming forested to the north and to the west
along Cedar Creek. While the site is predominantly vegetated, a few small bare spots
exist in the field. The property is relatively flat, ranging from 762 to 768 feet above
sea level, with a broad swale bisecting the area and running from east to west.
The property is surrounded on three sides by a chain-link fence. Some gaps exist in
the fence which can potentially allow access onto the site. The fourth side, to the
west, is bounded by dense vegetation and Cedar Creek. The vegetation and a steep
bank between the creek and the former trench areas make access to the site from the
creek difficult though not impossible. Currently, workers visit the site periodically to
cut the grass. Other than the grounds maintenance, no other activities occur at the
site.
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Record of Decision
Diamond ShamrocK Land611 Site
Page 2
FIGURE 1-1: LOCATION MAP
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SITE
,
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SCALE IN MILES
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, .......
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FINAL
Record of Decision
Diamond Shamrock Landfill Site
Page 3
FIGURE 1-2: SITE MAP
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FINAL
Record of Dec:isjon
Diamond Sha1lU"OCk Landfill Site
Page 4
2.0
SITE HISTORY AND ENFORCEMENT ACTMTIES
Prior to 1968, the land use of the Site area included agricultural activities. In 1972,
approximately 1,500 gallons of oil pitch and 600 to 800 drums containing reportedly
obsolete, off-specification products and raw materials from chemical plant
manufacturing operations were buried in unlined disposal trenches at the Diamond
Shamrock Site.
On June 27, 1980, the Diamond Shamrock Corporation (DSC) which was the
owner / operator reported to Georgia Environmental Protection Division (EPD) of the
Department of Natural Resources the results of an internal investigation concerning
waste material buried on Site. DSC reported that between 600 and 800 drums and
approximately 1,500 gallons of material were buried at the Site.
Henkel Corporation acquired the property in 1987.
During March 1988, USEP A performed soil sampling, geophysical studies and an
environmental assessment at the site. Four trench areas were approximately defined
with a ground magnetometer survey, and soil samples were collected and split with
Henkel.
In July of 1989, Henkel conducted a test excavation/waste characterization study
which identified five drum/waste disposal areas. These disposal areas comprised
less than one tenth of an acre and consisted of five trenches that were about 6 feet
wide and from 6 to 14 feet in depth. The test excavation program identified that
migration of waste into adjacent soils was limited to approximately 1 to 3 feet.
During September and October 1989, Henkel performed initial hydrogeologic
investigations. Field work included the decommisSioning of four old monitoring
wells, the drilling of seven continuously sampled soil test borings, and the installation
of six groundwater monitoring wells. .
Under the direction of U.S. EP A Region IV, an interim waste removal project was
completed in the fall of 1990, in which trench waste materials were removed for
treatment/disposal under EP A oversight. The trenches were then backfilled with
compacted clay-rich soils. Post-closure and surface soil samples were collected
around the trench and soil/waste holding areas.
Henkel performed additional site characterization investigations during the RI/FS
field work in the summer of 1992 to supplement the previous investigations. Two
subsurface soil samples were collected to supplement the trench closure samples, one
near the entrance to the access road to characterize background levels. Four more
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FINAL
Record of Decision
DiamoIld Shamrock Landfill Site
Page 5
monitoring wells were installed and sampled along with the original six wells.
Surface soil samples were collected around the trench and holding areas. Six surface
water and sediment samples were collected from Cedar Creek to characterize current
conditions in these media.
3.0
IDGHUGHTSOFCOMNrnNnYPARTIOPATION
All basic requirements for public participation under CERCLA sections
113(k)(2)(B)(i-v) and 117, were met in the remedy selection process. Because the local
community has been interested and involved in the Cedartown Superfund Sites
including Diamond Shamrock Landfill Site during the remedial activities at this Site,
community relations activities remained an important aspect throughout the remedial
process. The community relations program at the Site was designed to maintain
communication between the residents in the affected community and the government
agencies conducting remedial activities at the Diamond Shamrock Landfill Site.
Frequent communication with nearby residents and local officials has been
maintained as a priority. Special attention has been directed toward keeping the
community informed of all study results. EP A officials attended a local Chamber of
Commerce public forum and a Kiwanis Oub meeting in 1991. In addition, a meeting
was held with the community at an availability session in the Winter of 1991 to
inform residents of EPA's intentions for the RIfFS.
On March 22, 1994, after the finalization of the Remedial Investigation (RI) Report
and the completion of the Feasibility Study (FS), EP A presented its preferred remedy
for the Diamond Shamrock Landfill Site during a public meeting on March 22, 1994,
at the Cedartown Public library, 245 East Avenue, Cedartown, Georgia. The 3O-day
public comment period was held March 4, through April 4, 1994. A copy of the
Administrative Record, upon which the remedy was based, is located at the
Cedar town Public Library, 245 East Avenue, Cedartown, Georgia 31701. EPA's
responses to the comments received during the comment period are contained in
Appendix A.
4.0
SCOPE AND ROLE OF ACTION
This selected remedy is the fust and final remedial action for the Site. The function
of this remedy is to reduce the risks associated with exposure to contaminated
ground water. .
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Record of Decisjon
Diamond Shamrock Landfill Site
Page 6
The selected remedial alternative will address the following condition which poses a
threat to human health and the environment:
.
Contaminated ground water (may potentially impact drinking water
supplies).
The pathway of exposure is the ingestion of contaminated ground water.
The major components of the remedy are:
.
Implementation of deed restriction(s) or restrictive covenant(s) to
prevent ground water usage and drilling resulting in exposure to
ground water contaminants;
.
Completion and maintenance of Site access restrictions (fencing and
signage);
.
Ground and surface water monitoring program to confirm that natural
attenuation processes are effective and that contaminants would not
migrate;
.
Performance of five year reviews in accordance with Section 121(c) of.
CERCLA to assure that human health and the environment continue to
be protected by the remedy, that natural attenuation continues to be
effective, and whether ground water performance standards continue to
be appropriate; and,
Continued ground water monitoring upon attainment of the
performance standards at sampling intervals to be approved by EP A.
The ground water monitoring program would continue until EP A
approves a five-year review concluding that the alternative has achieved
continued attainment of the performance standards and remains
protective of human health and the environment.
.
This remedy is the first and final cleanup action planned for the Site. The ground
water present beneath the Site contains elevated levels of contaminants. Although
this water bearing zone is affected, the contamination is not affecting the public
drinking water supply (Cedartown Springs). The purpose of this proposed action is
to prevent future exposure to contaminated ground water.
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FINAL
Record of Decision
Diamond Shamrock Landfill Site
Page 1
5.0
SUMMARY OF SITE CHARACTERISTICS
5.1
METEOROLOGY
Mean monthly temperatures for Cedartown, Georgia range from 42 degrees
Fahrenheit rF> for January to 79"F during July and August. Record extreme
temperatures range between 106"F to -S"'F (NOAA, 1978). The mean annual rainfall
in the area is approximately 52 inches. The wettest months of the year are normally
from December to April (averaging 4.6 inches to 5.9 inches per month) with the driest
months of the year typically from August to November (averaging 2.9 inches to 3.9
inches per month). Snowfall occurs occasionally during winter months with
maximum accumulations between 6 inches to 8.3 inches. The 24-hour rainfall
intensity for the 10o-year storm is approximately 8 inches.
5.2
PHYSIOGRAPHY
The Diamond Shamrock Site is located in the Southeastern Mixed Forest Province
ecoregion. Forests of the region are characterized by broadleaf deciduous and
needleleaf evergreens. The former waste trench area is predominately a meadow,
intermingled with some deciduous trees and a few large coniferous trees. Forests
occur to the west along Cedar Creek and north towards the Cedartown waste
treatment plant.
The Site area is relatively flat, with elevations ranging from approximately 768 feet
above mean sea level (MSL) along the east margin of the Site to 762 feet MSL along
the west margin of the Site, near Cedar Creek. A broad relatively flat swale bisects
the Site, running approximately east to west.
Most of the Site is fenced; however, there are gaps between the northern fence and
the eastern fence, the southern fence and Cedar Creek, and the northern fence and
Cedar Creek. Thus, movement of trespassers and wildlife into and out of the area is
possible.
Cedar Creek, which forms the western border of the site, is surrounded by dense
vegetation on both sides. It is approximately 10 meters wide with an average depth
of 1 to 2 meters, and is a potential swimming site. The Cedartown area is also
drained by Cedar Creek and its tributaries.
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FINAL
Record of Decision
Diamond ShaI1U'OCk Landfill Site
Page 8
5.3
GEOLOGY
REGIONAL
The Cedartown area is located in the Valley and Ridge Physiographic Province of the
southern Appalachians. Cedartown lies near the margin of the province that is
demarcated by the Cartersville vault (Cressler, 1970), located approximately seven
miles south and southeast of Cedartown. The Valley and Ridge province is
characterized by numerous elongated ridges and intervening valleys, that trend in a
general northeast-southwest direction, as a result of folding and vaulting.
The Newala Limestone formation, which is part of the Knox Group, is the
predominant bedrock geologic stratum in the Cedartown area. Bedding within the
Newal,a is generally thick to massive, with some beds containing sandy zones.
The Site area is located near the axis of a broad north-trending syncline, which
explains why the younger Newala Limestone is surrounded by older rocks of the
Knox Group. The Knox Group, including the Newala Limestone, is prone to karst
solutioning. Many of the small lakes and ponds in the area are expressions of
sinkhole features. .
Bedrock in the area is typically covered by residual soils that generally range in
thickness from 8 feet to 14 feet. However, solutioning/weathering of the limestone
bedrock results in localized thickness variations, with soils being absent at isolated
rock outcrops to being over-35 feet thick near solution features.
Residual soils derived from the in-place weathering of Newala Limestone generally
. consist of silty-elays, or clays with variable amounts of sand and sill Alluvial soils
may be found in the area, but are primarily restricted to streambanks or the
floodplains of streams and rivers. Alluvial soils generally consist of fine sand and
clayey sill
SITE
Structural geologic mapping within a 2-mile radius of the site was conducted on May
29, 1992. The two units which primarily underlie the area mapped, Knox Group and
Newala Limestone, are generally deeply weathered, consequently a paucity of
outcrops was available for measuremenl Significant discontinuities were measured
in nine fresh to saprolitic outcrops. The dominant types of fractures characterized
were joints. Joint sets typically displayed spacing of a few inches to several feet
along an outcrop and commonly showed evidence of water flow, as indicated by
surface stains or staining haloes parallel to the fracture. The joints are commonly
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FINAL
Record of Dec:isjon
Diamond Shamrock Landfill Site
Page 9
infilled with clay; however, locally dilated joints have remained open.
Sparse bedding and cleavage measurements were obtained during field mapping.
Where measured, cleavage is oriented N300E to N400E with a wide distribution in
dip. Bedding measured in one outcrop was oriented N40oE, 640SE. The dip of
bedding is most likely highly variable near this area due to proximity of the site to
two major structural features, the Cartersville vault to the south and a related
synclinal structure near the site.
Evidence of karstic features was observed during field mapping. These features are
characterized as broad-based, shallow sink holes. As described above, the joint sets
were dominantly near-vertically oriented near the Site. In lithologies where
solutioning is controlled primarily by vertical joints, steep-walled, narrow sink holes
typically develop. Based on the morphology of the sink holes observed near the site,
beddIDg-controlled karstic solutioning may be more active than joint-controlled
solutioning. Solution features are controlled by the distribution of joints or open
fractures. The degree of solutioning within the limestone is likely to increase toward
Cedar Creek. This phenomenon commonly occurs in limestone terrains as a result of
the rise and fall of the creek levels, which cause fluctuations in groundwater levels
and, thus, enhance the degree of solutioning.
Samples of Newala Limestone were retrieved. The Newala observed in core samples
is gray to light gray, moderately hard to very hard, massive, finely crystalline
(sparry) limestone, and is prone to karst solutioning.
Test borings and excavation data indicate that the contact between the limestone and
residual soils occurs within a transition zone that is relatively thin (generally less than
one foot), and contains small voids, cobbles and gray silty clay. This weathered
transition zone between the rock and soil appears to be more permeable than the
overlying clays. Groundwater is generally encountered near this transition zone.
5.4
SOILS AND OVERBURDEN
Overburden soils encountered at the Site consisted primarily of residual silty clays.
These soils were derived from the in-place weathering of the Newala Limestone.
Thin lenses of silty clayey sands have been encountered at the southern end of the
site near the Henkel wastewater treatment plant and at the northern end of the site.
The thickness of overburden soils on the Site range from zero feet to over 65 feet.
Grain size distribution data and laboratory permeability test results on overburden
silty clay soils (Golder Associates, 1990b) demonstrate that residual soils have a low
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saturated hydraulic conductivity of approximately 7x1o-B centimeters per second
(em/s), and are, thus, relatively low permeable materials. These fine-grained,
cohesive soils would tend to minimize the migration of site waste constituents in soil.
In-situ permeability testing generally confirms the relatively low PeI'II\eability of the
overburden soils, although hydraulic conductivity values derived using grain size
distribution and laboratory permeability testing are lower. The methodology utilized
to test the overburden permeability produced an average value for the hydraulic
conductivity of the material intercepted by the borehole. The average hydraulic
conductivity values for the materials intercepted ranged from 4 x 1cr em/s to
1 x 1o..c an/s (B-104). The relatively high average hydraulic conductivity shown in
B-104 is probably the result of the occurrence of the fine to medium sand intercepted
near the bottom of this boring.
5.5
SURFACE HYDROLOGY
The Cedartown area is drained by Cedar Creek and its tributaries, which are part of
the Mobile River basin (USGS, 1988). Cedar Creek flows north along the west margin
of the site and eventually flows into the Coosa River approximately 14 miles from the
site. Measured creek flows vary considerably, indicating substantial run-off and
probable discharge through solutioned limestone. Ground water elevations measured
at the Site are higher than the water level in ~e stream (except during Periods of
heavy precipitation), indicating that Cedar Creek is a gaining stream in the reach
bounded by the Site. The bedrock under the Site is karstic, so significant discharge
from the limestone into the stream should be expected. Water level data and stream
reconnaissance support this evaluation. A stream gaging station for Cedar Creek is
located at the Georgia Avenue bridge, approximately 1.5 miles upstream of the site.
For the period of record from May 1981 to 1988, extreme flows in Cedar Creek have
ranged from a low of 10 cubic feet per second (ds) in August 1986 and 1988 to a high
of 5,050 ds in February 1982 (USGS, 1988). The drainage area associated with the
gaging station at the Georgia Avenue bridge is 66.9 square miles.
The majority of the Site lies within the 100-year flood plain. Computed water level
profiles indicate that the majority of the Site is also inundated by the 5O-year flood,
and a substantial portion of the Site is inundated by the lO-year flood.
Substantial surface water run-off occurs at the Site due to the low ~abi1ity of
clay-rich overburden soils. Overland flow of runoff is toward localized shallow
depressions and drainage features that ultimately direct flow to Cedar Creek. Sheet
flow and intermittent shallow concentrated flow in drainage swales has been
observed following major precipitation events. Intermittent flow in small, shallow
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drainage features is generally short in duration, ending within a few hours after
major rainfall events. The Site is covered by perennial vegetation, and erosion
potential is limited. Further, during numerous Site visits for investigation and
maintenance, no evidence of erosion (such as ditch or gully formation) has been
observed.
5.6
HYDROGEOLOGY
Groundwater flow in the area is expected to be toward Cedar Creek, the principal
discharge area, although it may take an indirect (tortuous) path along solution
features before discharging into the creek. The occurrence of significant quantities of
groundwater in the area is primarily dependent upon the degree of secondary
permeability caused by fractures and solutioning within the rock. Major springs and
high yield wells in the Cedartown area are typically associated with major karst
solution features. Springs in the Newala limestone can discharge between 0.5
million gallons per day (mgd) and 15 mgd (Cressler, 1970).
The uppermost aquifer on Site is the Newala Limestone, as groundwater is generally
encountered at or below the top of rock. Karst solution features encountered in the
limestone during the drilling of Site monitoring wells indicate that the aquifer is
nonhomogeneous and anisotropic, such that flow will be controlled by solution and
joint features. Solution features or voids were encountered in many of the borings
during the RI. Solution features vary in size, orientation, and in their degree of
hydraulic connection, causing groundwater flow to take an indirect or tortuous path.
Water level data was obtained to help define the relationship of the water surface to
the geology. Based on potentiometric maps developed from the water level data, the
general direction of groundwater flow on site is to the west, toward Cedar Creek.
However, a groundwater flow component very near the creek may have a north-
northwest trend as creek flow is toward the north. The water level data and geologic
data show higher potentiometric levels than the creek swface elevation, indicating
flow to the creek. Therefore, Cedar Creek acts as a groundwater discharge zone.
Significant fluctuations in groundwater levels are expected due to the close proximity
of the Site to Cedar Creek. The creek is a principal groundwater discharge area for
the N ewala limestone, and this shallow bedrock aquifer is hydraulically connected
with the creek. Previous water level measurements from Site monitoring wells have
been used to document fluctuations of more than 6.5 feet; however, fluctuations of
more than 10 feet are likely to occur during larger storms.
Groundwater underlying the Diamond Shamrock Site was encountered at or below
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the top of the Newala Limestone. Karst solution features encountered in this
limestone indicate that the aquifer is nonhomogeneous and that groundwater flow
will be controlled by solution and joint features. Groundwater flow velocities within
the limestone aquifer will vary, depending upon the presence or absence of solution
features and the degree of interconnected solution features.
The current water supply for the city of Cedartown is a spring located near the center
of the town. This spring is upgradient and upstream of the Site and approximately
one mile southeast of the Site and has a flow range of approximately 3 million
gallons per day (mgd) to 5 mgd. No private or domestic drinking water wells are
believed to exist within a 2,000 foot radius of the Site, as residences in the area are
reportedly served by municipal water supplies (i.e., the Cedartown Water
Department or the Polk County Water Authority). Water sources for the municipal
water supplies are located approximately one mile from the site. One of the Polk
CountY Water Authority's production wells is located within a tluee mile radius of
the Site. One ~ther major groundwater user in the area is the Henkel Plant, which
pumps an estimated 2 mgd from a shallow solutioned zone within the Newala
Limestone. This well is located approximately 1/2 mile southeast of the Site. Water
from the plant well is reportedly used only for plant processes, such as cooling.
5.7
SUMMARY OF SITE CONTAMINATION
Sampling and analysis of various media has been performed to evaluate site
conditions. In addition to the initial work performed by Henkel before the RIIFS
program, verification samples were collected specifically for the RI/FS. The
groundwater summarization includes data collected prior to removal of the waste.
The media considered include surface soil, subsurface soil, groundwater, surface
water, and stream sediment from Cedar Creek. Surface soil conditions are
characterized by 12 surface soil samples collected on the Site during the summer of
1992, and three background surface soil samples that were collected off-site.
Subsurface conditions are characterized by closure verification samples collected from
the foot of the former waste disposal trenches after excavation was completed during
the removal action, plus one subsurface background sample collected from the boring
at monitoring well MW-10, and another subsurface soil sample collected near
monitoring well MW-7. Groundwater conditions are characterized by samples
collected during eight periodic sampling events conducted since October 1989.
Surface water conditions are characterized by samples collected at six locations
sampled during June 1992. Stream sediment conditions are represented by six
sediment samples collected near the surface water sampling stations during June
1992. Sampling locations are presented on Figure 5-1.
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FIGURE 5-1
SITE SAMPLING PLAN
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. .
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5.7.1
GROUND WATER CHARAcrERlZATION
Ground water sampling and analysis was performed according to procedures
prescribed in the Sampling and Analysis Plan (Golder Associates Ine., 1992). The ten
monitoring wells installed at the Site were sampled on July 21 and July 22, 1992, on
January 26 and January 27, 1993, on June 29 and June 30, 1993, and again in January
1994. Prior to July 1992, only the six monitoring wells that existed were sampled
Four additional monitoring wells were installed during July 1992. A summary of
contaminants detected in ground water since periodic monitoring was begun in
October 1989 are summarized in Table 5-1.
ORGANICS
Detect~d concentrations of organic chemicals were found in MW-1, MW-4, and MW-9
and included acetone, bis(2-ethylhexyl)phthalate, toluene, and trichloroethene.
While there have been sporadic detections of volatile and semivolatile compounds in
wells downgradient of the waste disposal areas, only three out of nine wells
(excluding background) have had parameters sporadically detected above the
Maximum Contaminant Levels (MCL).
l,2-Dichloroethane, with an MCL of 5.0 pg/L, was detected in the sample from MW-
4 at 7.2 pg/L and in the duplicate sample at 8.1pg/L during January 1990. This
detection was reported before source removal, and has not been reported since in
that well. 1,2-Dichloroetharie was reported in the sample from well MW-9 at 6.5
pg/L during June 1993 and at 6.1pg/L in the sample from background well MW-IO
during the same sampling event. l,2-Dichloroethane has been reported in the
samples from background well MW-10 twice since its installation. 1,2-Dichloroethane
has been reported only twice at low concentrations in any samples from
downgradient wells in four years of sampling, and that was in two separate wells.
Toluene, with an MCL of 1000 pg/L, was reported in well MW-4 samples one time
above the MCL, at a concentration of 2300 pg/L. MW-4 was resampled on October
29, 1993, and all wells during the January 1994 sampling event. The analytical results
indicates toluene levels were below the detection limit.
Trichloroethene was reported in the MW-1 for four consecutive sampling events,
from July 1990 to January 1992, then again in June 1993 (ranges from ND - 13 pg/l).
Trichloroethene was not reported in MW-1 during the July 1992, January 1993, or
January 1994 sampling events.
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TABLE 5-1
SUMMARY OF SUBSTANCES DETECTED IN GROUND WATER
ORGANICS
..
...: :P~~TI?~.::.:::>J1ANGE . .
: :.€REOUENC.Y:: :..... .
. .
:AF~~r .;.:.,;. :.S,!:~:(j0:.;::::
PARAMETER
..
. .
Acetone
1,2-Dichloroethane
Toluene
Trichlqroethene
Benzyl alcohol
bi6-2(Ethylhexyl)phthalate
2-Chlorophenol
O-Cresol
Phenol
beta-SHC
gamma-BHC
Heptachlor
Xylene6
3/72 9JB-1SO" .. MW-4,MW-9,MW-5 NA
6/72 6.0B-59 MW-4,MW-9,MW-10 5
4n2 6.5-2,300 MW-4 1,000
7f72 4J-13 MW-1,MW-4,MW-7 5
2/72 24-42 MW-4 NA
2/72 3J-42 MW-S.MW-9 6
1n2 72 MW-4 NA
1n2 110 MW-4 NA
2/72 18-220 MW-4 NA
4n2 0.17-.<>.87 MW-1,MW-4,MW-5 NA
MW-3
1n2 0.012 MW-S 0.2
2/72 0.013-0.059 MW-4,MW-5 0.4
1n2 10 MW-5 10,000
Notes:
Unit is ug/L.
Standard refers 10 MCL.
MCL for bis-2(Ethythexyl)phthalate effective 1/17/94.
J '" Estimated Concentration
B '" Parameter detected in blank
"
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TABLE 5-1 (continued) .
SUMMARY OF SUBSTANCES DETECTED TN GROUND WATER
TOTAL METALS
PARAMETER OETECTIOt(, ,',RANGE, ',' AFFECTED ' STANDARD:
FREOUENCY,. '"" " ,,:WElLS "
" ..... ,, " ' ,,'
... .
Aluminum 55171 0.10-11 All Wells NA .
Antimony 1171 0.52 ~,' MW~ 0.000
Arsenic 1171 0.013 MW-10 0.05
Barium 70/71 0.02-0.16 All Wells 2
Cadmiu(l1 1/71 0.0058 MW-e '0.005
Calcium 71171 0.11-240 All Wells NA
Chromium 16171 0.010-0.052 MW-3.MW4.MW-5.MW~ 0.1
MW-7.MW-8.MW-Q.MW-10
MW-1
Cobalt 1171 0.012 MW-10 NA
Copper 3fT 1 0.010-0.012 MW-3.MW-5.MW4 1.3
Iron 70/71 0.040-10.8 All Wells NA
Lead 10171 0.005-0.017 MW-3.MW4.MW-e.MW-10 0.015
MW-9
Magnesium 70171 8.8-57 All Wells NA
Manganese 70171 0.017-2.5 All Wells NA
Nickel 4171 0.010-0.020 MW-1.MW-2.MW-5 0.1
MW-4
Potassium 54171 1.0-13 All Wells NA
Sodium 70171 6.7-140 All Wells NA
r~d;um 3171 0.011-0.019 MW-4.MW~.MW-Q NA
60171 '0.013-0.17 All Wells NA
Zinc
Notes:
Unit is mgll.
Star.dard refers to MCL, except for the Lead and Copper Standards. which are USEPA Action Level6.
J.'oi:timonyarid nickel MCLs effective 1/17194.
. -. . - - ... I .,
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METALS
Metal concentrations have varied somewhat between sampling events for any
particular well. Manganese has been reported at elevated concentrations in some
downgradient wells during some sampling events, but has also been reported in the
background well MW-10. There is evidence that manganese concentrations may be
influenced by variability of groundwater quality at the Site. Manganese
concentrations have been reported in upgradient wells, and there is wide variability
of results within a given well during different sampling events. Sample results have
. been reported on several occasions that varied by more than an order of magnitude
for a particular well.
Statistically significant differences have been reported for total aluminum, barium,
iron, lead, and manganese for groundwater samples collected from downgradient
wells when compared to the upgradient well MW-1 during sampling events
conducted prior to January 1991. No TAL metal concentrations have exceeded
existing National Primary Drinking Water Standards for any groundwater sample.
BACKGROUND UNCERTAINTIES
The general groundwater flow in the vicinity is to the west, trending to the north
near Cedar Creek. MW-10 is east of the former disposal trenches, making it
upgradient. This interpretation is substantiated by the higher water level in MW-10,
which is typically at least 0.5 foot higher than MW-1. This groundwater gradient
prevails even during periods of historically high water levels in Cedar Creek, as
demonstrated during the January 1993 sampling event. This sampling event was
conducted during a high flow event in Cedar Creek, immediately following a flood
which partially inundated the Site.
The are concerns that the high levels of manganese (Mn) found on Site may be a
result of high background concentrations of Mn based on the June 1993, MW-10
sample results. When comparlI\g the filtered versus non-filtered data, it is evident
that there is a significant difference in this data which is not apparent in any of the
other samples. The non-filtered detected concentration of Mn was 1800 ug/l and the
filtered concentration was non-detect «10 ug/l). This is not the case in any of the
previous samples in this monitoring well or any other monitoring well. Secondly, in
samples analyzed both prior to and after the June 93 sampling events, Mn was
detected at substantially lower concentrations than the 1800 ug/l. The maximum .
detected concentration in all of the other samples from the two background wells was
39('fug/1. Therefore, the 1800 ug/l detection of Mn in MW-10 in June 1993 is not
. acceptable for a background comparison. The average background value for Mn
(based on MW-10 data, excluding the 1800 pg/l as discussed above) is 145 pg/l,
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which is well within the human health risk-based performance standard.
Mter reviewing this information, EPA has concluded that the June 1993, MW-10
sample was probably not representative of background ground water concentrations
(EPA letter dated January 20, 1994, acceptance of the Diamond Shamrock RI). The
average background concentrations currently indicates that manganese is likely a site
related contaminant and a risk-based performance standard for manganese is
appropriate and attainable. However, future sampling analysis would be required to
confirm background water quality and evaluate if the ground water performance
standard remains appropriate. H, based on future sampling analysis, the background
concentration for a contaminant exceeds the MCL or established acceptable risk-based
standard, amending the performance standards to background groundwater
contaminant concentrations would be evaluated.
5.7.2
SOIL CHARACfERIZATION
A total of 29 on-site surface soil samples (from a depth of 0 to 6 inches) were
collected from various locations on-site, 17 just after closure of the excavated trenches
(in 1991) and 12 in June of 1992. Two of the samples collected in 1992 were collected
from the same locations as samples from the earlier round of sampling. For these
locations, only the more recent data were used. Thus data from a total of 27
sampling locations were used for this assessment.
A total of 26 on-site subsurface soil samples were collected, 25 from the trenches as
post-closure samples and one in 1992 from near the eastern fenceline at soU boring
location B-101B. The post-closure samples were collected from the bottoms of
trenches at depths ranging from 4 to 12 feet.
5.7.2.1
SURFACE SOILS
Surface soil sample .locations are shown on Figure 5-1. The surface soil samples
considered to be most representative of current site conditions were those collected
during the additional site characterization conducted during June 1992. The
analytical results are presented in Table 5-2 for all surface soil samples collected.
Surface soil samples collected during June 1992 indicated no unacceptable risks to
human health and the environment. Since the additional surface soU samples were
located in areas that were most likely to have residual contamination, these soil
samples present the most accurate presentation of potential surface soil
contamination.
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TABLE 5-2
SUMMARY OF SUBSTANCES DETECfED IN SURFACE SOILS (a)
(Organics: ug/kg, InorganlCS: mg/Kg)
Range of Detected
Mean Range of Range of Site-specific Range of Regio!
Frequency of S~le Arithmetic Detection Detected On-site Background Background
Chemi ca 1 Detection (b) Size (c) Mean Li mi ts Concentrations Concentrations (d) Concentrations
Organi cs: -"
.. Acetone 1 / 27 27 21.1 10 - 120 110 NO «10) NA
.. Bromoform 1 / 27 27 3 5 - 12 6.3 ND «5) NA
.. Io,Io'-OOE 1 / 10 (f) 10 2.7 1..3 - 5.1 5.2 NA NA
.. 1,2-Dichloroethane 1 / 27 27 3 5 - 12 6.7 ND «5) NA
.. Methylene Chloride 1 / 27 27 3.3 5 - 12 11. ND «5) NA
.. I.-Methyl phenol 1 / 27 25 189 330 - 1.20 370 ND «330) NA
.. Naphthalene 1 / 27 25 191 330 . 1.20 1.40 ND «330) NA
.. N-nitrosodiphenylamine/
diphenylamine, 1 / 27 25 208 330 - 1.20 860 ND «330) NA
.. Pheno 1 5 / 27 27 3,530 330 - 2,000 380 - 47,000 ND «330) NA
.. Trichloroethene 4 / 27 27 9.1 5 - 12 7.1 . 110 ND «5) NA
lnorganics: (g)
Alumin~ 12 / 12 12 5,060 NU 3,500 . 8,500 3,600 . 8,800 10,000 - >100,0'
Arsenic 7 / 12 12 2.1 2 2.1 - 1..7 2.7 - 4.9 1.1. - 29.0
Bar-ium 10 / 12 12 57.3 "1.0 27.7 - 120 79 - 80 200 - 700
Beryl I h.m 1 / 12 12 0.5 0.2 - 1 1.2 NO «1) 1.0
Calcium 2 / 12 12 653 1 ,000 1 ,21.0 - 1 ,600 1,300 - 21,000 1.00 - 6,000
Chromil.m 12 / 12 12 12.5 NU 5.1 . 21 8.2 . 26 7.0 - 70.0
Cabal t 6 / 12 12 8.8 10 1..7 - 21. 10 3 - 20
Copper 8 / 12 12 6.1 4 4.1. - 11. 5.1. - 13 3 . 50
Iron 12 / 12 12 18,200 NU 6,600 . 60,000 1.,100 - 32,000 10,000 - 70,000
lead 12 / 12 12 17.7 NU 5 - 35 11 - 30 10 - 300
t1agnes i um 1 / 12 1 1.1.5 NU 1.1.5 NO «1,000) 1,500 . 3,000
t1anganese 12 / 12 12 71.3 NU 72 - 2,100 250 - 1,900 100 . 3,000
Nickel 5 / 12 12 9.9 8 5.7 - 33 NO «8) 5 - 50
Potassium 1 / 12 1 - 302 NU 302 NO «1,000) 3,300 - 16,000
Sodium 1 / 12 1 278 NU 278 NO «1,000) 1 ,000 - 10,000
Vanadium 11 / 12 12 19.5 10 13.6 - 36 17. - 52 30 - 70
Zinc 12 / 12 12 62.3 NU 12 . 250 20 - 31. 15 - 1.00
NU = Not used. No detection limits were used to calculate the arithmetic mean, either because the chemical
was detected in all the samples or the detection limit was greater than 2 times the maximum detected
concentration.
NA = Not analyzed.
.. = Chemical of potential concern.
(a) Data from surface soil samples Surface-1 through Surface-10, Surface-11A, Surface-12, Surface-13, Surface-15,
and Surface-16 from the 1991 post-closure samples; and DSCLS-101S through DSClS-107S and OSClS-111S through
DSClS-115S from the June 1992 samples.
(b) The number of samples in which the contaminant was detected divided by the total nutber of samples analyzed.
(c) The number of samples used to calculate the mean. This nutber may be less than the denominator of the frequency
of detection because non-detect samples with high detection I imits were not included in calculating the mean.
(d) Site-specific background data from samples DSCLS-108S. DSCLS-109S. and DSClS.110S.
(e) Regional background data based on s.les taken by Boerngen and Shacklette (1981) from within 50 miles of the site
(Bartow, Cobb~Floyd and Haralson Counties in Georgia and DeKalb County in Alabama).
(1) Only 10 of the 1991 samples (and no 1992 samples) were analyzed for pesticides.
(g) Only the 1992 samples were analyzed for inorganics.
. "
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ORGANICS
Ten organic chemicals were detected in Pre-RI (removal) and RI surface soil samples.
Phenol and trichloroethene were detected at the greatest frequency (5/27 and 4/27,
respectively) and phenol was detected at the highest concentrations (e.g., 47,000
ug/kg). Neither of these chemicals was detected in any of the 1992 surface soil
samples. The rest of the organic chemicals (acetone, bromoform, 4,4' -DOE, 1,2-
dichloroethane, methylene chloride, 4-methylphenol, naphthalene, and N-
nitrosodiphenylamine/diphenylamine) were each detected only once. Methylene
chloride was the only chemical detected in any of the 1992 surface soil samples.
Acetone was reported in an equipment rinse blank, which was prepared during the
soil sampling event. Resampling was not considered to be necessary due to the low
concentrations.
.
INORGANICS
Only the 1992 surface soil samples were analyzed for inorganic chemicals. These
inorganic chemical concentrations were compared to site-specific and regional
background concentrations. Regional background data were used to supplement site-
specific background in order to provide more information about chemicals that were
not detected at elevated detection limits (e.g., magnesium, potassium, and sodium).
Based on this comparison, all 17 of the inorganic chemicals detected in surface soil
were statistically within background ranges.
5.7.2.2
SUBSURFACE SOIL
27 on-site subsurface soil samples (excluding background) were collected and are
grouped and summarized as follows:
1)
Removal and Trench Post-Closure: 4 areas: (1) Trenches 1,2,3 with 17 samples;
(2) Trench 4 with 4 samples; (3) Trench 5 with 4 samples; and,
2)
RI Subsurface Samples: Two additional subsurface soil samples were
analyzed, one background sample collected from east of the Site from the
boring at monitoring well MW-10 (sample DSCLS-501S), and another at boring
B-I01B (sample DSCLS-502S), which was collected near the top of bedrock at a
location identified as an area of possible contamination during the soil gas
survey.
The,locations of subsurface soil samples are shown on Figures 5-1 (p.13) & 5-2.
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FIGURE 5-2
TRENCH CLOSURE AND SUBSURFACE SAMPUNG PLAN
TRENCH 1
1C-' ..
II.
TRENCH 2
2C-t
.
(0'
:lC-2.
eta)
APPRO"- SCALE IN FEET
o 20 40
TRENCH 3
TRENCH 4
TRENCH 5
, .
..c.,
.
c,,)
. .C-2/"C.~1
(0) 4C-f
LEGEND
..
.c-. CLOSURE VERIFICATION SAMPLE
LOC" TlON & IDEN TIFICA TION NUMBER
(0)
S"MPLE DEPTN (BELOW ORIGIN"L
L"ND SURFACE. APPROX.MUE.)
MOre SAMPLES 4C-4. .c-T. ~ 5C-T. sc.e. 5C-9. AND 5C-10
WERE COUECTED AFTER NTIAL \'ERI'ICATIOH SAWUHG AND TRE1JMENT.
~
j
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Subsurface soil samples collected during 1992 indicated no W\acceptable risks to
human health and the environment. Residual subsurface soil contamination
produced by former waste disposal practices has been determined to be in isolated
areas and at low concentrations. Waste constituents are mainly confined to the foot
of the former waste disposal trenches, which varied in depth from eight to fourteen
feet.
REMOVAL AND TRENCH CLOSURE SAMPLE RESULTS
During the removal, closure verification samples were collected from trench floors
using a systematic random sampling strategy, as outlined in SW 846, third edition,
September 1986 (hereafter referred to as SW 846). A starting point was established
for each trench by choosing a random number between one and ten. This
dete~ed the initial sample point, in feet from the northern end of that particular
trench. From that point sample locations were distributed along the length of the
trench at pre-determined intervals depending on the length of the particular trench.
The sample locations were further randomized by choosing random numbers for the
distances from a trench wall (perpendicular to the long dimension of the trench). At
least four closure sample locations were selected for each trench, with the number of
samples proportional to the length of the trench.
TCL pesticides, PCBs and cyanide were not detected in any of the closure verification
samples; therefore, these parameters will not be discussed further.
Organics
Each disposal trench was excavated and sampled for closure as individual waste
units, as they often contained different proportions of various waste materials.
Therefore, the following presents a summary of organic constituents detected within
each waste trench unit.
Trench 1 - A total of seven samples were collected from Trench 1 on October 24, .
1990, to evaluate residual soil conditions prior to closure. No TCL semi-volatile
organic compounds were detected in Trench 1 closure samples. The following is a
summary of volatile organic constituents detected in Trench 1 samples:
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TRENCH 1
Acetone
1,2-Dichloroethane
.m9 0.99
<0.0057 o.m
<0.0057 0.054
<0.032
<0.0064
0.22
<0.0059
0.23
<0.0061
0.25
<0.0062
031
0.60
031
0.11
Trid1Joroethylene
<0.0064
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Xylenes -dUXJ63 <0.0064 0.014 <0.83 <0.0063 <0.0059 o.oos
bis(2. 17 <0.42 <8.60 <8.60 <8.10
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However, additional soil could not be removed from the bottom of the trench using
available excavating equipment. Therefore, the trench was left open, and the
remaining soil was treated in-situ, using a proprietary bact~rial consortium and
nutrients. On August 19, 1991, the trench was resampled. Detected TCL organic
parameters are summarized below.
TRENCH 5
Phenol
<0.110
4.9
6.0
30.0
<0.120
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Barium 23-310 38-220 69-650 1.~130 25-'n 44-82
Beryllium ND-1.5 ND-2.0 ~1.3 ND-1.2 ND-4.o ND-1.5
Calcium 3:m.1700 38(}.ISOO 3~910 400-1300 170-4900 47O-3SOO
Chromium 8.4-32 1&31 1649 11-23 8.6-28 17-24
Cobalt ND-42 6.2-16 9.9-19 7.5-32.2 2.8-15 5.2-U
Copper ND-19 12-28 14-23 13-32 7.0-20 5.7-17
Iron 12000.4800O 2()00().45()00 31(XX).65(JOO 34000-73100 18CXJ0.41000 1~
~ 3.7-51 4.3-6S 12-33 12-36 14-29 9~12.3
Magnesium 52G-1800 55M700 63().3000 450-1100 140-1700 ~740
Manganese 89-4800 74-1500 1~1800 88-1090 89-390 290380
Mercury ND-O.08O O.()5.fi 11 0.081-0.14 0.Q86.0.18 0.052-0.18 0.04-0.23
Nickel 4.4-26 12-31 9.8-35 8.s.36.7 ND-27 5~12.1
Potassium 24-1400 S8().34OO 1300-6500 UOO..22OO ~1600 32G8SO
Sodium ND-96 ND-2000 ~O ~loo ND ND
Vanadium ND-48 21-57 35-87 29-0.2 15-37 17-31
Zinc: ND-73 40-71 66-120 36-90.7 34-8S 41-510
ND - Non Detected
RISUBSURFACES~LES
There were no TCL organic parameters detected in sample DSCLS-501S. Acetone
was reported in sample DSCLS-502S at a concentration of 240 pg/kg. Sample
DSCLS.S02S was collected near the eastern fence1ine in an attempt to determine the
source of trich1oroethene in a nearby monitoring well (MW-l). For this reason the
sample was only analyzed for volatile organic chemicals. The only Vex: detected in
this sample was acetone at 240 ug/kg.
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5.7.3
SURFACE WATER CHARAcrERIZATION
Surface water samples were collected from locations illustrated in Figure 5-1.
Surface water data are presented in Table 5-3. Surface water samples indicated no
unacceptable risks to human health and the environment.
ORGANICS
Some organic chemicals (acetone, 2-butanone, bis(2-ethylhexyl)phthalate, 4-methyl-2-
pentanone, toluene, and xylenes) were detected at low levels in surface water
samples collected in January and June of 1991. Also, these chemicals were all also
detected in subsurface closure samples from the trenches (collected in the fall of
1990). However, no organic chemicals were detected in surface water in the most
recent. sampling events.
INORGANICS
Inorganic chemical concentrations in surface water were compared to background
concentrations. Based on this comparison, all detected inorganic chemicals except
manganese were statistically within background ranges. However, the detected
concentrations of manganese in the downstream samples were all only slightly higher
than Oess than 2 times) the maximum concentration detected in the upstream
samples. Based on both comparisons to background concentrations, no chemicals
were selected as chemicals of potential concern for surface water.
5.7.3.1
SEEP STUDY OF CEDAR CREEK
A survey of the eastern bank and the bed of Cedar Creek was performed on June 9,
1992 to identify seeps that may discharge groundwater flowing under the Site.
Visual inspection of the stream bed and bank was accomplished by walking within
the stream bed. The stream bed and eastern bank were inspected under the water
surface using Self Contained Underwater Breathing Apparatus (SCUBA) equipment.
No seeps were found in the survey reach.
5.5.4
SEDIMENTS CHARACTERIZATION
Three sediment samples were collected in June, 1992 from the same downstream
locations in Cedar Creek as the surface water samples.
Results are shown in Table 5-4.
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TABLE 5-3
SUMMARY OF SUBSTANCES DETECI'ED IN SURFACE WATERS
SUBSTANCE DETECTION CONCENTRATION BACKGROUND
FREQUENCY RANGE CONCENTRATIONS
ORGANICS - pg/l
Acetone 1/24 12 ND
2-Butanone 1/24 120 ND
4-MethyJ-2-pentanone 1/24 14 ND
Toluene 2124 6.6 - 23 6.6 -7.1
Trichlorethene 1/24 1 ND
Bis-2(Ethylhexyl)phthaJate 3/24 14 - ISO 28-68
Xylenes 1/24 6 ND
INORGANICS. mg/l
Aluminum 17/24 .2 - .63 ND - .36
Barium 24/24 .019 - JY1.9 .019 - .028
Calcium 24/24 15 - 34 ND
Chromium 1/24 .024 ND - .024
Iron 24/24 .19 - .93 .19 - .f/)
Magnesium 24124 4.9 - 11 5-11
Manganese 24124 .032 - .081 .032 - .070
Potassium 2J24 1-1.1 ND
Sodium 24124 1.5 - 32 1.5 - 32
Zinc 2124 .018 - .093 ND - .093
ND = Non Detect
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TABLE 5-4
SUMMARY OF SUBSTANCES DETECTED IN SEDIMENTS
SUBSTANCE DETECTION CONCENTRATION BACKGROUND
FREQUENCY RANGE CONCENTRATIONS
ORGANICS - IIglkg
Acetone '116 13 - 68 68
Aroclor 1248 1/6 340 ND
INORGANICS. mglkg
Aluminum 6/6 2100 - 3780 2100 - 3780
Arsenic 5/6 2.7 - 6.8 4.9 - 6.8
Barium 5/6 20 - 40.2 26 - 40.2
Calcium '116 807 - 1300 ND - 807
Chromium 6/6 11 - 42.5 26 - 42.5
Cobalt 3/6 7.8 - 12 7.8 - 12
Copper 6/6 6.4 - 22.7 72- 22.7
Iron 6/6 7200 - 27000 12900 - 27000
Lead 6/6 21 - 84 40-68
Manganese 6/6 47 - 570 334 - 570
Vanadium 416 10 - 21 12.3 - 21
Zinc 6/6 40 - 170 43 - 53.6
ND = Non Detect
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Sediment samples indicated no Wlacceptable risks to human health and the
environment.
ORGANICS
Acetone was detected in one sediment sample Downstream-I, located adjacent to the
site. However, acetone was also detected in the backgroWld sediment sample at a
concentration five times higher than the downstream concentration (68 ug/kg and 13
ug/kg, respectively). Sample DSCLS-115B, an equipment rinse blank prepared
during the same event as sediment sampling, was reported to contain 11 JIg/L of
acetone. Acetone was not be considered a chemical of potential concern for sediment
due to detected concentrations in backgroWld and rinse blank samples.
No T~ semivolatile parameters were reported above detection limits in any of the
samples.
For Pesticide/PCB parameters, Aroelor 1248 was reported in one sample, collected at
the most downstream sampling station, at 340 JIg/kg (polychlorinated biphenyls
concentrations are evaluated relative to Aroelor compoWlds). None of the PCBs has
been detected in any sample collected at the Site in any medium. No arOOors were
detected in any other sample, in any other media or location at the Diamond
Shamrock site.
INORGANICS
Various TAL metal parameters were reported in all of the sediment samples.
Inorganic concentrations for downstream samples are similar to upstream samples,
although for several analytes (aluminum, antimony, arsenic, barium, beryllium,
cobalt, iron, manganese, and vanadium) the upstream samples tended to have higher
concentrations than the downstream samples.
Inorganic chemical concentrations were compared to background concentrations. The
results showed that none of the detected concentrations of inorganic chemicals were
statistically greater than backgroWld For this reason, no inorganic chemicals were
selected as chemicals of potential concern.
6.0
SUMMARY OF SITE RISK
CERCLA directs EP A to conduct a Baseline Risk Assessment (BRA) to determine
whether a Superfund Site poses a current or potential threat to human health and the
environment in the absence of any remedial action. A baseline risk assessment was
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conducted as part of the RI and provided the basis for determining whether or not
remedial action is necessary and the justification for performing remedial action.
The Summary of Site Risk Section includes only exposure pathways and chemicals of
concern if the results of the risk assessment indicate a potential current or future
significant risk. The criteria for determining a significant risk are those contaminants
that contributed to a pathway which exceeds a 1E-4 risk or Hazard Index (HI) of 1;
chemicals contributing risk to these pathways need not be included if their individual
carcinogenic risk is less than 1E-6 or their noncarcinogenic risk Hazard Quotient (HQ)
is less than .1. The only pathway meeting this criteria is the Future Residential
Ingestion of Ground Water Route.
6.1
HUMAN HEALTH RISKS
The human health risk assessment evaluated the nature and extent of the threat to
public health caused by the release or threatened release of hazardous substances
from the Site.
6.1.1
CONTAMINANTS OF CONCERN (COCS)
The following methodology was used for selection:
.
All organic chemicals- detected in soils and groundwater were considered to be
chemicals of potential concern (USEP A 1989a). All organic chemicals in
surface water and sediment downstream of the site were considered to be
chemicals of potential concern associated with the site unless also detected at
high concentrations in upstream samples.
.
Because many of the inorganic chemicals detected at the site occur naturally,
concentrations in site-related samples were compared to concentrations in
background samples. This statistical comparison could be made for data from
surface soil, surface water, and sediment samples. If less than three
background samples were collected (e.g., for groundwater at this site) or
detection limits for background were not provided (e.g., for subsurface soil),
maximum concentrations of inorganic chemicals detected at the site were
compared with two times the maximum background concentrations to
determine if the detected levels were elevated above background according to
Region IV guidance (1992c). If a chemical concentration within a medium and
area group was greater than two times the maximum site-specific or regional
background level (whichever was higher), then it was selected as a chemical of
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potential concern. This method was used for subsurface soil and groundwater
data.
.
Chemicals with low toxicity and no available USEP A validated toxicological
information relevant to human health were not considered. This includes
aluminum, calcium, cobalt, iron, magnesium, potassium, and sodium.
Most of the organic chemicals detected during the waste excavation/remediation and
during the remedial investigation were selected as chemicals of potential concern.
Organic chemicals which were detected historically in groundwater and surface water
samples were not selected as chemicals of concern if they were not detected in the
past two rounds of sampling in these media. Acetone was not selected as a chemical
of potential concern for sediment from Cedar Creek because it was detected at
elevated concentrations in sediment upstream of the site and in an equipment rinse
blank.' Inorganic chemicals were selected as chemicals of potential concern by a
comparison to site-specific and regional background data.
6.1.1.1
COCS IN GROUND WATER
Monitoring wells MW-10 is upgradient of the Site and provided background ground
water quality data. However, due to the substantial analytical differences and
variability in the background results, background water quality will need to be
confirmed during future ground water monitoring.
Metal concentrations in background ground water will be confirmed using low stress
sampling techniques during future ground water sampling.
Seven chemicals detected in the monitoring wells met the COC criteria: acetone,
barium, bis(2-Ethylhexyl)phalate, lead, manganese, toluene, and trichloroethene.
Chemicals of concern and their related exposure point concent1'anons for the Future
Residential Ingestion of Ground Water Route are summarized in Table 6-1
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TABLE 6-1 CONTAMINANTS OF CONCERN & EXPOSURE
POINT CONCENTRATIONS
Media and Chemical Exposure Point Concentrations
Frequency RME Background
of Detection
1 2
GROUND WATER J1g/1 JLg/1
Acetone 1/9 32 ND
Barium 5/14 228 81
Bis(2-Ethylhexyl)phalate 1/9 3 ND
Lead '1J9 8.2 3 ND
Manganese 4/14 1.970 160
Toluene 1/9 850 ND
Trichloroethene 1/9 8.5 ND
1 Frequency of detection indicates the number of wells that in
which the chemical was detected during sampling events 1/92
and 7/92 which were utilized in establishing point
concentrations in the risk assessment.
2 Reasonable Maximum Exposure (RME) defined as the 95%
upper confidence limit chemical concentration (UCL) on the
arithmetic mean (or maximum concentration when the UCL
exceeds the maximum).
3 RME for lead was the highest detected concentration.
6.1.2
EXPOSURE ASSESSMENT
Whether a chemical is actually a concern to human health depends upon the
likelihood of exposure, i.e. whether the exposure pathway is currently complete or
could be complete in the future. A complete exposure pathway (a sequence of events
leading to contact with a chemical) is defined by the following four elements:
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.
Source and mechanism of release;
.
a transport medium (e.g., Ground w~ter, surface water, air) and
mechanisms of migration tluough the medium;
.
the presence or potential presence of a receptor at the exposure point;
and
.
a route of exposure (ingestion, inhalation, dermal absorption).
If all four elements are present, the pathway is considered complete.
The two major constituent release and transport mechanisms potentially associated
with the Site are as follows:
.
Infiltration of precipitation tluough the residual chemical affected soils
from waste storage and the percolation of the resulting leachate into the
ground water; and,
.
release of affected soil by seeps/leachate run-off to surface waters, .
sediments, and soils.
Because of infrequent and low detection of VOCS in surface soils, any exposure via
inhalation to constituents in-air transport is not considered significant.
An evaluation was undertaken of all potential exposure pathways which could
connect chemical sources at the Site with potential receptors. All possible pathways
were first hypothesized and evaluated for completeness using the above criteria. The
current pathways represent exposure pathways which could exist under current Site
conditions while the future pathways represent exposure pathways which could exist,
in the future, if the current exposure conditions change.
6.1.2.1
CURRENT EXPOSURE
The following pathways were evaluated under current land-use conditions:
.
Incidental ingestion of surface soil by trespassers and workers at the site;
.
Dermal absorption of chemicals from surface soil by trespassers and workers
at the site;
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.
Incidental ingestion of sediment by trespassers near the site; and
Dermal absorption of chemi~ from sediment by trespassers near the site.
Excess upperboW\d lifetime cancer and noncarcinogenic risks associated with the
above exposures were all less than EPA's benchmark and are not likely to occur.
Inhalation risks from exposures to chemicals volatilizing from surface soil were not
quantified because volatile organic compounds were detected infrequently, at low
concentrations, and because the site is fairly well vegetated.
.
GROUND WATER
Under current land use conditions, no nearby residents or workers are known to use
groundwater for drinking water. Residents in the area use Polk County and
Cedadown municipal drinking water supplies. Therefore, exposures via the use of
groundwater for ingestion was not be considered under current land-use conditions.
6.1.2.2
FUTURE EXPOSURE
Changes of land use associated with the site which may result in exposure and risk
to the chemicals of potential concern were addresses. It was assumed that the
Diamond Shamrock Site could potentially be developed in the future. The type of
development considered to pose the greatest potential for health risks is residential;
accordingly, for the exposure pathway analysis, it has been assumed that a
hypothetical future residence would be built directly on the site in the area of the
former trenches. Potential future exposure scenarios included all the exposures
examined under current conditions. Exposure assumptions were considered the same
in evaluating future conditions as were used in evaluating current conditions.
The table below summarizes the exposure pathway analysis for hypothetical future
land use conditions.
.
Ingestion of groundwater by hypothetical residents living on the site;
.
Incidental ingestion of surface soils by hypothetical residents living at the site;
Dermal absorption of chemicals from surface soils by hypothetical residents
living at the site;
.
.
Incidental ingestion of sediment by hypothetical residents at the site; and
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.
Dermal absorption of chemicals from sediment by hypothetical residents at the
site.
GROUNDWATER
The only pathway indicating an unacceptable human health risk is the Future
Residential Ingestion of Ground Water Route. Under future land-use conditions, a
hypothetical on-site resident could install a well and be exposed to groundwater from
the site.
Routes of exposure associated with groundwater could include ingestion of drinking
water, inhalation of chemicals that have volatilized from groundwater during use
(e.g., while showering, cooking, watering the lawn); and dermal contact with
groundwater during in-home use (e.g., while bathing, washing dishes). According to
USEPA (1992b), dermal contact with most chemicals in water during bathing will
usually result in lower exposures than direct consumption of the same water.
Inhalation exposure to volatile chemicals in groundwater tends to be on the same
order of magnitude as exposure from direct consumption of the same water. Only
the ingestion of drinking water exposure pathway was evaluated quantitatively in the
assessment with the understanding that inhalation exposures will occur at a level
comparable to ingestion exposures.
Below indicates the exposure medium, source and/or release mechanism, exposure
point, potential receptor and route of exposure for ground water under the future
land-use scenario.
Medium:
Groundwater
Source and mechanism:
Leaching of contaminants from soils to groundwater
Potable use of ground water
Exposure Point:
Potential Receptor:
Route of Exposure:
Resident Adult/Child (1-6yrs)
Ingestion/inhalation while showering
6.1.2.3
EXPOSURE POINT CONCENTRATIONS
Exposures were. estimated for each of the wells that contained chemicals of concern
using data from the RI. The Reasonable Maximum Exposure (RMB) concentration
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defined as the 95% upper confidence limit chemical concentration (UCL) on the
arithmetic mean (or maximum concentration when the DCL exceeds the maximum)
for each chemical of concern is shown in Section 6.1.1, Table 6-1 (p.33).
For organic chemicals of concern, the exposure point concentration was based on
concentrations in each well. MW-9 was only sampled once, so the concentrations of
acetone and bis(2-ethylhexyl)phthalate detected at that time were used as the
exposure point concentrations. MW-4 was sampled eight times and the exposure
point concentration for this well was based on recent trends in sampled
concentrations. The concentration of toluene in MW-4 was 6.5 ug/L in January 1992,
and increased to 850 ug/L in June 1992. The value of 850 ug/L was conservatively
used as the exposure point concentration, rather than the mean of these two detects
since the dramatic increase in concentration may indicate the presence of a chemical
slug moving across the area, and the concentration of toluene may continue to
increaSe.
MW-1 was also sampled eight times. In MW-1, the concentration of trich1oroethene
(TCE) has fluctuated within a range during the past five samples collected: 13 ug/L
(7/90), 9.3 ug/L (1/91), 5.8 ug/L (6/91), 12 ug/L (1/92), <5 ug/L (7/92). Although
TCE was not detected in the most recent sample, concentrations have dropped close
to the detection limit in the past and then increased again. For this reason, the
nondetect was assumed to be a temporary drop in the concentration of TCE in MW-1,
and one-half the detection limit for the 7/92 nondetect was included in calculating
the arithmetic mean. This arithmetic mean of TCE concentrations detected in the
samples from 7/90 to 7/92 was used as the exposure point concentration.
Exposure point concentrations for the inorganic chemicals of potential concern are
based on the concentration measured in the June 1992 sampling event.
The future residential ingestion of ground water exposure scenario assumed a 30 year
duration (6 years as a child), and an exposure frequency of 350 days per year. The
assumed ingestion rates for an adult and a child were 2 liters and 1 liter, respectively.
Body weights were 70 kg for adults and 15 kg for a child
6.1.3
TOXICITY ASSESSMENT
A cancer slope factor (CSF) and a reference dose (RID) are applied to estimate the
potential risk of cancer from an exposure and the potential for non-carcinogenic
effects to occur from the exposure.
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CSFs have been developed by EPA's Carcinogenic Assessment Group for estimating
excess lifetime cancer risks associated with exposure to potentially carcinogenic
contaminants of concern. CSFs which are expressed in units of (mg/kg/day)-., are
multiplied by the estimated intake of a potential carcinogen in mg/kg/day, to
provide an upper-boW1d estimate of the excess lifetime cancer risk associated with
exposure at that intake leveL The term "upper-bound" reflects the conservative
estimate of risks calculated from the CSF. Use of this approach makes
W1derestimation of the actual cancer risk highly unlikely. CSF 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.
This increased cancer risk is expressed by terms such as 1E-6. To state that a
chemical exposure causes a 1E-6 added upper limit risk of cancer means that if
1,000,000 people are exposed, one additional incident of cancer is expected to occur.
The ca1culations and assumptions yield an upper limit estimate which assures that no
more than one case is expected and, in fact, there may be no additional cases of
cancer. USEP A policy has established that an upper limit cancer risk falling below or
within the range of 1E-6 to 1E-4 is acceptable.
RIDs have been developed by EP A for indicating the potential for adverse health
effects from exposure to contaminants exhibiting noncarcinogenic effects. RIDs which
are expressed in units of mg/kg/ day, are estimates of lifetime daily exposure levels
for humans, including sensitive individuals, that are likely to be without appreciable
risk of an adverse health effect. Estimated intakes of COCS from environmental
media (e.g. amoW1t of COCS ingested from contaminated ground water) can be
compared to the RID. RIDs 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 (e.g. to account for the use of animal data to
predict effects on humans). H the estimated exposure to a chemical expressed as
mg/kg/ day is less than the RID, the exposure is not expected to cause any
non-carcinogenic health effects, even if the exposure is continued for a lifetime. In
other words, if the estimated dose divided by the RID is less than 1.0, there is no
concern for adverse non-carcinogenic health effects.
The toxicity values which were used to calculate human health risks are summarized
in Table 6-2.
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TABLE 6-2 CONTAMINANTS OF CONCERN TOXICITY ASSESSMENT
Media and Chemical Toxicity
CSFz RfD 1
l/(mg/kg/day) mglkg/day
GROUND WATER
Acetone * .1
Barium * .07
bis(2-Ethylhexyl)phalate 1.4E-02 .02
Manganese * .005
Trichloroethene 1.1E-02 .074
Toluene * .2
1 Reference doses (RfDs) have been developed by EPA for indicating the potential for adverse
health effects from exposure to chemicals exhibiting non-carcinogenic effects. Adapted from
USEPA IRIS, January 1993 except 10r Trichloroethene (1987 Office of Drinking Water, Health
Advisory).
2 Cancer potency factors (CPFs) have been developed for estimating excess lifetime cancer
risks associated with exposure to potentially carcinogenic chemicals. Adapted from USEPA
IRIS, January 1993 except for Trichloroethene (Memo from EPA, Chemical Mixture Assessment
Branch, Joan Dollarhide. July 1992).
* NOT APPLICABLE
6.1.4
RISK CHARACTERIZATION
For carcinogens, risks are estimated as the incremental probability of an individual
developing cancer over a life-time as a result of exposure to the carcinogen. Excess
life-time cancer risk is calculated from the following equation:
RISK = CD! X CSF
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where:
risk = a unit less probability (e.g., 2 X 1et5) of an individual developing cancer;
CDI = chronic daily intake averaged over 70 years (mg/kg-day); and,
CSF = slope-factor, expressed as (mg/kg-day)-l
These risks are probabilities that are generally expressed in scientific notation (e.g.,
1X10"' or 1£'). An excess lifetime cancer risk of 1 X 10"' indicates that, as a
reasonable maximum estimate, an individual has a 1 in 1,000,000 chance of
developing cancer as a result of site-related exposure to a carcinogen over a 7o-year
lifetime under the specific exposure conditions at the Site.
The potential for noncarcinogenic effects is evaluated by comparing an exposure level
over a specified time period (e.g., lifetime) with a reference dose derived for a similar
exposure period. The ratio of exposure to toxicity is called a hazard quotient (RQ).
By adding the HQ's for all COCS that affects the same target organ within a medium
or across all media to which a given population may reasonably be exposed, the
Hazard Index (HI) can be generated.
The HQ is calculated as follows:
Non-cancer HQ = CDI/RID
where:
CDI = Chronic Daily intake
RfD = Reference Dose; and,
CDI and RID are expressed in the same units and represent the same exposure
period (i. g., chronic, subchronic, or short-term).
To evaluate the estimated cancer risks, a risk level lower than lxlQ-6 is considered a
minimal or deminimis risk. The risk range of 1xlO"' to lxl
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further evaluation. For example, although the hazard quotients of the several
chemicals present are added and exceed 1.0, further evaluation may show that their
toxicities are not additive because each chemical affects different target organs. When
total affects are evaluated on an effect and target organ basis, the hazard index of the
separate chemicals may be.at acceptable levels.
Carcinogenic risks and non-carcinogenic hazards were evaluated for potential
exposures to media-specific chemicals of concern in surface soil, surface water,
surface sediment and ground water. Receptor populations were potentially exposed
workers, trespassers and area residents that could, theoretically, use ground water for
a household water source.
Estimated potential exposure to chemicals of concern in surface water, surface soil
and surface sediments did not result in unacceptable carcinogenic risk or
non-carcinogenic hazard.
Estimated potential added non-carcinogenic risks from the use of contaminated
ground water for household use are in an unacceptable range.
TABLE 6-3: SUMMARY OF UNACCEPTABLE RISK - GROUND WATER
INGESTION a
Chemical
. Lifetime Excess Cancer Risk
N/A
N/A
2E-07
N/A
N/A
1E~
Hazard Quotient
.02
.2
.01
30
Acetone
Barium
bis(2-Ethylhexyl)phalate
Manganese
Toluene
Trichloroethene
0.1
.08
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6.1.5
IDENTIFICATION OF UNCERTAINTIES
The following primary sources of uncertainty were associated with the estimation of
chemical uptake from exposure to ground water:
.
Environmental sampling and analysis, and selection of chemicals;
Exposure parameter estimation; and
Toxicological data.
.
.
The important sources of uncertainty in this assessment are discussed below. As a
result of the uncertainties described below, this risk assessment should not be
construed as presenting an absolute estimate of risk to persons potentially exposed to
chemicals at the site. Rather, it is a conservative analysis intended to indicate the
poten~al for adverse impacts to occur.
Environmental Sampling and Analysis, and Selection of Chemicals
Environmental chemistry analysis error can stem from several sources, including
errors inherent in the sampling or analytical methods.
.
Systematic or random errors in the chemical analysis may yield erroneous
data.
.
The maximum detected site concentration was compared to 2 times the
maximum background level when less than three site-specific background
samples were available.
Many of the samples in the Diamond Shamrock data had non-detects associated with
high detection limits. This may result in an underestimation of risk if chemicals were
not detected, and thus not evaluated, because of the elevated detection limits. High
detection limits were particularly associated with semi-volatile chemical analysis in
soils, due both to matrix interference and high concentrations of phenol
Additional uncertainty is associated with chemicals reported in samples at
concentrations below the reported quantification limit, but still included in data
analysis. No qualifier was used in the validation of Diamond Shamrock data to
denote which concentrations were below the quantification limit. However some
reported concentrations were below detection limits shown for non-detects in other
samples indicating that some of the concentrations were probably estimated.
A limited number of samples for background and for some potentially-affected
environmental media may result in an over- or under-estimation of risk. For
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groundwater, only one well (MW-10) was at a great enough distance from the site to
be considered background. This well was only installed in 1992 and was sampled
once for inorganics and twice for volatile organic chemicals (V0Cs).
Exposure Parameter Estimation
There are two major areas of uncertainty affecting exposure parameter estimation.
The first relates to estimation of exposure point concentrations. The second relates to
parameter values used to estimate chemical exposures (as either average daily doses
or inhalation exposure concentrations).
(1)
Estimation of Exposure Point Concentration Uncertainties
.
Environmental concentrations were based on data available from the RI.
.
Chemical concentrations reported as non-detected were included as one-
half the detection limit in calculating concentrations.
The 95% upper confidence limit on the population mean or maximum
(whichever was lower) was used as the exposure point concentration.
.
The approach used to select exposure point concentrations may overestimate
potential exposures and thus risks. The exposure point concentration for a
specific chemical in a particular medium was based on the 95% upper
confidence limit (UCL) on the population mean, or the maximum detected
concentration, whichever was less. Since the 95% UCL is highly unstable from
a mathematical standpoint, and is strongly influenced by the sample size and
geometric standard deviation (GSD) of the chemical concentrations being
evaluated, the approach to estimating exposure point concentrations often
results in the default use of the maximum detected concentration. The use of
maximum concentrations in the risk assessment resulted in conservative
estimates of exposures and risks.
When calculating exposure point concentrations from sampling data, 1/2 of the
reported detection limits for non-detect samples were included in the
calculation of the 95% UCL if 1/2 of the detection limit was not greater than
the maximum measured value. Any approach dealing with non-detected
chemical concentrations is associated with some uncertainty. Non-detect
results do not indicate whether the chemical is absent from the medium,
present at a concentration just above zero, or present at a concentration just
below the detection limit.
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(2)
Parameter Values (chemical exposures) Uncertainties
.
Exposures were assumed to occur on a regular basis for each selected
pathway.
.
Frequency of exposure was based on consideration of site-specific
conditions.
.
Default USEP A assumptions regarding body weight, duration of
exposure, and life expectancy may not be representative for the site area
population.
.
Exposures were estimated assuming no migration of residents out of the
facility area for 30 years.
.
Default reasonable maximum exposure (RME) values were used for soil
ingestion rates.
.
The dermal absorption of chemicals from soils/sediment through skin
was based on default USEP A Region IV assumptions.
Uncertainties are inherent in the selection of pathways for evaluation. It was
assumed that individuals in the site area would engage in certain activities that
would result in exposures for each selected pathway. This assumption is
conservative. It may-be likely that the activity patterns assumed to occur in
this analysis only occasionally occur. Furthermore, even if an individual were
to engage in an activity, it is not necessarily true that an exposure would be
experienced. It may be unlikely that every time an individual trespasses on
the site (assuming this were to occur), he or she will contact and incidentally
ingest surface soils.
Evaluation of the dermal exposure pathway is also affected by uncertainties in
many of the exposure parameters. Assumptions were made about which
portions of the body's skin surface areas would be exposed. The choice of
exposed body parts may slightly under- or over-estimate risk. Significant
uncertainties are also associated with the use of the dermal absorption fraction
related to contact with sediment and soil. The limited information available on
the dermal absorption of chemicals from contacted soil under realistic
environmental conditions may result in an under or an over-estimation of risk.
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Toxicological Data
Toxicological data uncertainties are presented below.
.
Quantitative toxicity criteria were not available for all of the selected chemicals
of concern.
.
Cancer slope factors derived from animal studies are based on upper 95th
percentile confidence limits derived from the linearized multi-stage modeL
.
Uncertainties in the design, extrapolation and interpretation of toxicological
experimental studies.
.
. Conservatively derived reference doses were used to assess risks.
.
Risks were assumed to be additive although they may potentially be
synergistic or antagonistic.
The dermal exposure pathways were evaluated using oral toxicity criteria in
conjunction with oral absorption factors obtained from ATSDR where
available, or default oral absorption factors from Region IV.
In the hazard and risk evaluations, the risks or hazards presented by several
chemicals reported for the same exposure have been added to provide a sum of
estimated total risk or hazard for that particular exposure. This is a conservative
assumption and is scientifically accurate only in those instances where the health
effects of individual chemicals are directed at the same effect and same target organ.
The effects may be additive, synergistic or antagonistic. Since a large number of
chemicals have no similarity as to their non-carcinogenic action or the target of their
action, this approach may over-estimate risk.
.
There is a degree of uncertainty regarding the RID for manganese in the ground
water ingestion scenario. There is currently a debate whether it is appropriate to
separate the exposures from food and water as currently done by IRIS for some
chemicals, and whether it is appropriate to separate the exposure from food and
water as presently done for manganese (and some other inorganics) by IRIS. Due to
the high degree of uncertainty associated with the present RID of 0.005 mg/kg/ day
for manganese, the RID determination is scheduled for future EP A review. The
current EP A RID for manganese in water of 0.005 mg/kg! day was used to evaluate
risks concerning manganese drinking water intake.
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6.2
ENVIRONMENTAL ASSESSMENT
The environmental assessment evaluated impacts to ecological receptors caused by
the release or potential release of hazardous substances from the Site. The
approaches used in the environmental assessment roughly paralleled those used in
the human health risk assessment.
All organic and inorganic chemicals present at levels greater than background were
considered for inclusion as chemicals of potential concern for the ecological
assessment. Chemical concentration, frequency of detection, and toxicity were then
used in choosing the chemicals of potential concern for the individual media.
6.2.1
TERRESTRIAL
The former waste trench area is predominantly meadow, with forested areas to the
north and to the west along Cedar Creek. The Site is fairly well vegetated, with a
few small bare spots in the field. Various reptiles, birds, and mammals have been
observed at the Site.
The Freshwater Wetlands and Heritage Inventory Program (FWHIP) of the Georgia
Deparbnent of Natural Resources and the U.S. Fish and Wildlife Service has indicated
that the endangered and threatened species presented below may be within Polk
County, the county in whi~ the Diamond Shamrock Landfill site is located.
An;mals
Hali4eetus leucocephalus
Myotis griseseenB
Myotis sodalis
Plants
lsotoria meldeoloides
Cypripdeium acaule
Cypripdeium calceo
Veratnun woodii
Lygodium palmatum
Silene regia
Trichomanes peteT'Bii
Bald Eagle
Gray Bat
Indiana Bat
Endangered
Endangered
Endangered
Small whorled pogonia
Pink lady's slipper
Yellow lady's slipper
Wood false hellebore
Climbing fern
Royal catchf1y
Dwarf filmy fern
Endangered
Unusual
Unusual
Endangered
Imperiled in State due to rarity
Critically imperiled in State due to extreme rarity
Imperiled in State due to rarity
The FWHIP also provided more detailed information for the topographic quadrangles
located within a five-mile radius of the site. This more detailed information indicated
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that the plant species listed below have not been observed at the site or in the
quadrangle that the site is located within. Also, some of the plant species on the list,
like the small whorled pogonia, prefer open understory, which does not occur at the
site due to the thick understory of swamp-privet. However, the FWHIP has only
inventoried approximately 5% of its data. Thus, the possibility of endangered or
threatened plant species occurring at the site cannot be precluded.
Gray bat, although listed in Polk County, was not listed in any of the quadrangles
within five miles of the site so the likelihood of its presence onsite is minimal.
Although Indiana bat could feed at Cedar Creek, the small size of the creek might
limit the number of bats that forage at the site. Bald eagles, although they prefer
nesting in areas near water, are unlikely to nest near Cedar Creek or spend much
time foraging there because the creek is extremely small compared to that typically
used by foraging bald eagles. The FWHIP and USFWS also provided endangered
species information for Floyd County. However, the likelihood of species of special
concern in Floyd County occurring at the site is minimal given the distance of over
four miles. Even animal species with large foraging ranges are unlikely to spend
much, if any, time at the site due to the small size, proximity to human activity, and
the partial fencing.
Only phenol was selected as a chemical of potential concern in surface soil because of
its concentration, frequency of detection, and toxicity. Contaminants in subsurface
soils were not evaluated, since these soils are generally inaccessible to plants and
wildlife at the Site.
Wildlife may be exposed to chemicals of potential concern in surface soils at the
Diamond Shamrock Landfill site by several pathways: 1) ingestion of contaminated
soil while foraging or grooming; 2) ingestion of food that has accumulated chemicals
from soil; 3) dermal absorption; and, 4) inhalation of chemicals that have volatilized
or been wind-eroded from soil. Terrestrial species most likely to be impacted by
chemicals in the soil at the Diamond Shamrock Landfill site are soil-dwe1ling
invertebrates (e.g., earthworms) and small mammals (e.g., shrews) because of their
intimate contact with the soil which can lead to dermal absorption and ingestion of
potentially contaminated soil and food (e.g., soil-dwelling invertebrates). Predatory
mammals and birds are unlikely to be adversely impacted because phenol does not
bioaccumulate in the food chain (i.e., bioconcentration factors <25).
Earthworm toxicity to phenol was evaluated by examining the toxicity of
pentachlorophenol, a chlorinated, more toxic form of phenol, which findings suggests
that earthworms would not be adversely affected by phenol concentrations at the site.
Data on small mammals were not available so they could not be quantitatively
evaluated. However, the presence of vegetation over most of the former waste trench
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areas suggests that contact by small mammals with surface soil would be minimal
and adverse effects are unlikely.
Due to lack of phytotoxicity data, a quantitative assessment of potential terrestrial
plant impacts was not performed However, the presence of vegetation over many of
the former waste trench areas suggests that current concentrations of phenol are not
adversely impacting plant species.
Terrestrial animals higher in the food web, such as birds or mammals, also could be
exposed to sediment contaminants via ingestion of aquatic organisms which have
accumulated sediment contaminants in their tissues. Since arodor-1248 (a PCB, with
a relatively high bioaccumulation potential) was found in a downstream sediment
sample, the potential risk of aroclor-1248 in sediment to birds feeding on aquatic
inverteprates was quantitatively evaluated. The results indicate that birds are not
expected to be adversely affected from levels of arodor-1248 in the sediments. There
is uncertainty associated with the dietary toxicity value and the estimated
bioaccumulation of PCBs in aquatic invertebrates. However, the single sample detect
of aroclor-1248 suggests that significant exposures to aroclor-1248 are unlikely given
the larger feeding range of bird species, especially migratory waterfowL
6.2.2
AOUATIC
Cedar Creek is the only permanent surface water body at the Site. The Site is
bisected by a broad swale which directs surface water runoff from the Site into Cedar
Creek. Also, ground water from beneath the Site discharges into Cedar Creek.
Various amphibians, reptiles, and fish have been observed in the creek, and a variety
of aquatic invertebrates are expected to occur there.
Arodor-1248, lead, and zinc were evaluated as chemicals of potential concern in
sediment; these chemicals were found at elevated concentrations at one downstream
sediment sampling location. The maximum detected value in sediments for these
constituents fall between NOAA ER-L and ER-M values indicating the potential for
adverse effects to aquatic organisms in Cedar Creek. Although the toxicity
comparisons suggest that any adverse impacts that might occur would only happen
to sensitive life stages and/or species, adverse impacts are unlikely due to only
detection of lead, zinc, and arodor 1248 in only one sediment sample. Therefore,
exposures would most likely be miriimaL Additionally, there is some uncertainty
associated with the sediment toxicity values since the levels of organic carbon in the
sediments have been estimated In addition the toxicity values for invertebrates are
based on studies on estuarine organisms. It is not known if the organisms at the site
are different in sensitivity than the estuarine organisms.
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No chemicals in surface water were selected for evaluation because the downstream
concentrations were within, or only slightly greater than, the upstream
concentrations.
Since there is a potential for ground water discharge into Cedar Creek; acetone,
barium, bis(2-ethylhexyl)phthalate, lead, manganese, toluene, and bichloroethene
were selected as ground water chemicals of potential concern and evaluated with
respect to potential effects on Cedar Creek biota. However, the absence of Site
related chemicals in surface waters during monitoring suggest that discharge of
chemicals from ground water does not appear to currently be occurring to any
measurable degree, and therefore, adverse effects are not expected. However, surface
water will be monitored to confirm that ground water contaminant discharges are not
occurring.
6.3
CONTAMINANTS OF CONCERN & PERFORMANCE STANDARDS
Estimated potential exposure to site chemicals in surface water, surface soil, and
subsurface soils, and sediments do not result in unacceptable cancer or non cancer
risks at the Diamond Shamrock Site. However; the estimated non-cancer risks from
future exposure to ground water exceeds EPA's cleanup target risk range and an HQ
of 1. Therefore, EP A established performance standards for chemicals in ground
water detected at levels above EPA's target risk range or Safe Drinking Water Act
MCL to ensure that any future ground water users would not be exposed to unsafe
levels of site-related contaminants. Performance standards for the remediation of
ground water are shown in Table 6-4. .
Since remediation below background levels is not technically feasible, additional
sampling will be conducted to confirm if data is indicative of background conditions
and evaluate if the ground water performance standard remains appropriate. If,
based on future sampling analysis, the background concentration for a contaminant
exceeds the MCL or established acceptable risk-based standard, amending the
performance standards to background groundwater contaminant concentrations
would be evaluated
Actual and threatened releases of hazardous substances from this Site, if not
addressed by implementing the response action selected in this ROD, may present an
imminent and substantial endangerment to public health, welfare, or the
environment.
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TABLE 6-4
SUMMARY OF REMEDY PERFORMANCE STANDARDS (GROUND WATER)
Contaminant ~ 8taDcIud (NIQ
118Di-- 200.
Tol- 1.000 18
1'IIcbIoJOetlaeae ,18
1.2. DIcIIJoroethaDe ,h
a- CalcaJated ...... .... OD - acceptUle risk 01'. BuanI Q18deDt (IIQ) of 1. ~w.. -~-
are . :a Utei' pel' clay lqestloD nte _cI . 70 kDo,....1MNty 1NJ&Iat.
18- .Safe DrIDkIDC Water Act Maw-f-am eo..-1n-t LeftI (IIa.).
7.0
DESCRIYfION OF ALTERNATIVES
The Feasibility Study Report evaluated possible alternatives for remediation of
conditions at the Diamond Shamrock Landfill Site. A total of four (4) alternatives
have been established for detailed analysis consideration. These alternatives were
selected to provide a range of remedial actions for the Site.
7.1
ALTERNATIVE GW-l: NO AcrION
EPA is required to consider the no action alternative by the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP), the regulation
implementing the Superfund law. It is used as a baseline for comparing other
alternatives. Under this alternative, EP A would take no action to minimize the
impact ground water contamination has on the area. There is no cost associated with
this alternative since no additional activities would be conducted.
7.2
ALTERNATIVE GW-2: INSTITUTIONAL CONTROLS AND
GROUND WATER MONITORING.
This alternative would include:
.
Implementation of deed restriction{s) or restrictive covenant{s) to prevent
ground water usage and drilling resulting in exposure to ground water
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contaminants;
.
Completion and maintenance of Site access restrictions (fencing and signage);
Ground and surface water monitoring program to confirm that natural
attenuation processes are effective and that contaminants would not migrate;
.
.
Performance of five year reviews in accordance with Section 121(c) of CERCLA
to assure that human health and the environment continue to be protected by
the remedy, that natural attenuation continues to be effective, and whether
ground water performance standards continue to be appropriate; ~d,
Continued ground water monitoring upon attainment of the performance
standards at sampling intervals to be approved by EP A The ground water
'monitoring program would continue until EP A approves a five-year review
concluding that the alternative has achieved continued attainment of the
performance -standards and remains protective of human health and the
environment..
.
IThe groundwater monitoring program would require additional sampling and
analysis to further define background groundwater concentrations of contaminants
and the effectiveness of natural attenuation. H, based on future sampling analysis,
the background concentration for a contaminant exceeds its MCL or acceptable risk-
based standard, EP A may evaluate whether ground water performance standards
continue to be appropriate and may consider amending the performance standards to
background groundwater contaminant concentrations. The installation of additional
well(s) may be required in evaluating background water conditions. Ground and
surface water samples would be collected at sampling points and intervals to be
approved by EP A. EP A, at its sole discretion, may revise sampling intervals of the
groundwater monitoring program. Low-stress sampling methods would be used
during the monitoring to determine whether contaminants continue to be a problem.
The present worth of this alternative is estimated at $461,331 (semi-annual sampling)
with a capital cost of $30,360 and annual Operation and Maintenllnce (O&M) costs
of $34,730 for 30 years.
7.3
ALTERNATIVE GW-3: GROUND WATER COLLECI10N WELLS
This alternative would include:
.
Institutional Controls described in Alternative GW-2;
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.
Active remediation of ground water. Ground water would be extracted,
treated and discharged until all performance standards are met for two
consecutive sampling events. Operation of the groundwater extraction systems
for an estimated period of 30 years. System to include:
.
Install extraction wells (estimated at 7 @ 45 feet deep). Pumping of a
total of approximately 100 gpm from the extraction wells;
.
Ground water discharge to Henkel Waste Water Treatment Plant;
.
Modifications to Henkel Waste Water Treatment plant for increased
capacity and to meet NPDES requirements; and,
.
Install pipe transfer systems from the well systems to the treatment
plant;
.
Performance of five year reviews and ground/surface water monitoring
program to ensure effectiveness of treatment and reduction in movement as
described in alternative GW-2;
.
Continued ground water monitoring upon attainment of the performance
standards at sampling intervals to be approved by EP A The ground water
monitoring program would continue until EP A approves a five-year review
concluding that the alternative has achieved continued attainment of the
performance standards and remains protective of human health and the
environment.
Contaminated groundwater would be extracted and discharged to the Henkel
wastewater treatment plant for treatment During the pump and treat operations, the
withdrawn groundwater would be stored in an equalization tank from which it
would be pumped to a treatment system. The equalization tank would provide
storage during times when a downstream treatment system might be shut down.
The number of wells, location, extraction rates, and WWTP modifications will be
determined during the RD and may require fwther characterization such as pump
tests and treatability studies. The final system and methods may be different due to
variations in the hydrogeologic conditions and will be determined during the design.
The present-worth cost of this alternative is estimated at $5,053,051 with a capital cost
of $662,682 and annual O&M costs of $353,804 for 30 years.
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7.4
ALTERNATIVE GW-4: GROUNDWATER COLLECI10N
TRENCHES
This alternative would include:
.
Institutional Controls described in Alternative GW-2;
.
Active remediation of ground water. Ground water would be extracted,
treated and discharged until all performance standards are met for two
consecutive sampling events. Operation of the groundwater extraction systems
for an estimated period of 30 years. System to include:
.
Construction of three collection trenches (estimated at 50 to 150 feet long
and 30 feet deep);
.
Pumping rate estimated at 150 gpm from the trenches; and,
.
Ground Water Treatment and Discharge as described in GW-3;
.
Performance of five year reviews and ground/surface water monitoring
program as described in alternative GW-2.
.
Continued ground water monitoring upon attainment of the performance
standards as described in GW-3.
Contaminated groundwater would be extracted and discharged to the Henkel
wastewater treatment plant for treatment During the pump and treat operations, the
withdrawn groundwater would be stored in an equalization tank from which it
would be pumped to a treatment system. The equalization tank would provide
storage during times when a downstream treatment system might be shut down.
The number of extraction trenches, final dimensions, pumping rate, and WWTP
modifications will be determined during the RD and may require further
characterization such as pump tests and treatability studies. The final system and
methods may be different due to variations in the hydrogeologic conditions and
would be determined during the design.
The present-worth cost of this alternative is estimated at $7,234,449 with a capital cost
of $881,184 and annual O&M costs of $511,987 for 30 years.
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7.5
APPLICABLE OR RELEVANT AND APPROPRIATE
REOUIREMENTS (ARARs)
The remedial action for the Diamond Shamrock Landfill Site, under CERCLA Section
121(d), must comply with federal and state environmental laws that are either
applicable or relevant and appropriate requirements (ARARs). Applicable
requirements are those standards, criteria or limitations promulgated under federal or
state law that specifically address a hazardous substance, pollutant, contaminant,
remedial action, location, or other circumstance at a CERCLA Site. Relevant and
appropriate requirements are those that, while not applicable, still address problems
or situations sufficiently similar to those encountered at the Site that their use is well
suited to the particular Site. To-Be-Considered Criteria (TBCs) are non-promulgated
advisories and guidance that are not legally binding, but should be considered in
dete~g the necessary level of cleanup for protection of health or the
environment.
The affected ground water in the aquifer beneath the Diamond Shamrock Landfill
Site has been classified by EP A as Class ITA. Oass llA ground water is a current
source of drinking water. It is EPA's policy that ground water resources be protected
and restored to their beneficial uses. A complete definition for ground water
classification is provided in the Guidelines for Ground water Classification under the
EP A Ground water Protection Strategy. Final Draft, December 1986.
While TBCs do not have the status of ARARS, EPA's approach to determining if a
remedial action is protective of human health and the environment involves
consideration of TBCs along with ARARs.
Location-specific ARARs are restrictions placed on the concentration of hazardous
substances or the conduct of activities solely on the basis of location. Examples of
location-specific ARARs include state and federal requirements to protect floodplains,
critical habitats, and wetlands, and solid and hazardous waste facility siting criteria.
Table 7-1 summarizes the potentiallocation-specific ARARs for the Diamond
Shamrock Landfill Site.
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TABLE 7-1
POTENTIAL LOCATION SPECIFIC ARARs
Location Citation
R&A Critical habitat upon Endangered Species Act of 1973
which endangered 50 CFR Parts 200 and 402
or threatened Fish and Wildlife Coordination Act
species depends 33 CFR Parts 320-330
R&A Area affecting Wild and Scenic River Act
stream or river 40 CFR Part 6.302(e)
STATE OF GEORGIA REGULATIONS
R&A Establishes facility Georgia Comprehensive Solid Waste Management
location standards Act, O.C.GA fi 12-8-20 et sea. and Rules, Chapter
. 391-3-4.
R&A Critical habitat upon Endangered Wildlife and Wildflower Preservation Act
which endangered of 1973 O.C.G.A. fi 12-6-172 et sea. and Rules,
or threatened Chapter 391-4-10.
species depends
A APPLICABLE REQUIREMENTS WHICH WERE PROMULGATED UNDER FEDERAL LAW
TO SPECIFICALLY ADDRESS A HAZARDOUS SUBSTANCE. POLLUTANT.
CONTAMINANT. REMEDIAL ACTION LOCATION OR OTHER CIRCUMSTANCE AT THE
DIAMOND SHAMROCK LANDFILL SITE.
R&A- RELEVANT AND APPROPRIATE REQUIREMENTS WHICH WHILE THEY ARE NOT
"APPLICABLE" TO A HAZARDOUS SUBSTANCE. POLLUTANT. CONTAMINANT.
REMEDIAL ACTION. LOCATION. OR OTHER CIRCUMSTANCE AT THE DIAMOND
SHAMROCK LANDFILL SITE. ADDRESS PROBLEMS OR SITUATIONS SUFFICIENTLY
SIMILAR TO THOSE ENCOUNTERED AT THIS SITE THAT THEIR USE IS WELL SUITED.
Action-specific ARARs are technology- or activity-based requirements or limitations
on actions taken with respect to hazardous wastes. These requirements are triggered
by the particular remedial activities that are selected to accomplish a remedy. Since
there are usually several alternative actions for any remedial Site, various
requirements can be ARARs. Table 7-21ists potential action-specific ARARs and
TBCs for the selected ground water remedy for the Diamond Shamrock Landfill Site.
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TABLE 7-2
POTENTIAL ACTION-SPECIFIC ARARs
CLEAN WATER ACT - 33 U. S. C. SS 1251-1376
R&A 40 CFR Part 131 - Ambient Ambient Water Quality Criteria: Ambient
Water Quality Criteria water standards for the protection of
human health and aquatic life.
R&A 40 CFR Part 122, 125 - Requires permits for the discharge of
National Pollutant Discharge pollutants for any point source into waters
Elimination System, 40 CFR of the United States.
Part 125, 40 CFR Part 131,
and 40 CFR Part 136.1
R&A 40 CFR Part 141 - National Specifies sampling, analytical and
Primary Drinking Water . monitoring requirements for public water
Standards systems.
R&A 40 CFR Part 403 - National Sets standards to control pollutants which
Pretreatment Standards pass through, interfere, or contaminate
treatment processes in public treatment
works.
RESOURCE CONSERVATION AND RECOVERY ACT - 42 U.S.C. SS 6901-6987
R&A 40 CFR 257 - 258 - Solid Establishes minimum levels of
Waste Management performance required of any solid waste
Regulations land disposal Site operation and including
operation and maintenance. .
R&A 40 CFR Part 261 - Characterizations of Treatment Facility
Identification & Usting of Generated Sludges.
Hazardous Wastes
R&A 40 CFR Part 262 - General requirements for identifying and
Standards Applicable to managing hazardous wastes and manifest
Generators of Hazardous requirements for hazardous wastes
Waste
R&A 40 CFR Part 263 - Establishes standards which apply to
Standards Applicable to transporting hazardous waste within the
Transporters of Hazardous U.S., if required under 40 CFR 262.
Waste
R&A 40 CFR Part 264 - Establishes minimum national standards
Standards for Owners and which define the acceptable management
Operators of Hazardous of hazardous wastes for owners and
WasteT~atment,Storage operators of facilities which treat, store or
and Disposal (TSD) dispose of hazardous wastes.
Facilities
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I TABLE 7-2 I
POTENTIAL ACTION-SPECIFIC ARARs
CLEAN AIR ACT - 42 U.S.C.15 7401-7642
R&A 40 CFR Part 61 - National Addresses hazardous air pollutants at
Emission Standards for their point of emission from specific
Hazardous Air Pollutants sources
STATE OF GEORGIA REGULATIONS
A Georgia Hazardous Site Requires corrective action for releases of
Response Act ~ O.C.G.A. hazardous waste, constituents, and
12-8-90 et sea. substances.
R&A Georgia Comprehensive Establishes minimum levels of
Solid Waste Management performance required of any solid waste
Act ~ O.C.GA 12-8-20 et land disposal Site operation and includes
sea. and Rules, Chapter operation and maintenance.
391-3-4.
R&A Georgia Hazardous Waste Establishes minimum state standards
Management Ad O.C.GA ~ which define the acceptable management
12-8-()0 et sea. and Rules, of hazardous wastes for owners and
Chapter 391-3-11. operators of facilities which treat, store or
dispose of hazardous wastes in the State
of Georgia.
A Water Well Ad of 1991 Establishes the requirements for the
O.C.G.A ~ 12-5-120 et sea. drilling and abandoning of monitoring
wells.
R&A Georgia Water Quality Pre-treatment standards and permit
Control Ad O.C.G.A. ~ 12- requirements for Publicly Owned
5-20 and Rules, Chapter Treatment Works, criteria and standards
391-H. for injection wells, and authorizes DNR to
issue discharge permits.
A APPLICABLE REQUIREMENTS WHICH WERE PROMULGATED UNDER FEDERAL
LAW TO SPECIFiCALlY ADDRESS A HAZARDOUS SUBSTANCE, POLLUTANT,
CONTAMINANT, REMEDIAL ACTION LOCATION OR OTHER CIRCUMSTANCE AT
THE DIAMOND SHAMROCK LANDFILL SITE.
R&A - RELEVANT AND APPROPRIATE REQUIREMENTS WHICH WHILE THEY ARE NOT
"APPLICABLE" TO A HAZARDOUS SUBSTANCE, POLLUTANT, CONTAMINANT,
REMEDIAL ACTION, LOCATION, OR OTHER CIRCUMSTANCE AT THE DIAMOND
SHAMROCK LANDFILL SITE, ADDRESS PROBLEMS OR SITUATIONS
SUFFICIENTLY SIMILAR TO THOSE ENCOUNTERED AT THE DIAMOND SHAMROCK
LANDFILL SITE THAT THEIR USE IS WELL SUITED TO THE SITE.
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Chemical-specific .ARARS are specific numerical quantity restrictions on individually-
listed chemicals in specific media. Examples of chemical-specific ARARs include the
MCLs specified under the Safe Drinking Water Act as well as the ambient water
quality criteria that are enumerated under the Oean Water Act. Since there are
usually numerous chemicals of concern for any remedial Site, various numerical
quantity requirements can be ARARs. Table 7-3 lists potential chemical-specific
ARARs for the Diamond Shamrock Landfill Site.
TABLE 7-3
POTENTIAL CHEMICAL-SPECIFIC ARARS
CLEAN WATER ACT - 33 U.S.C. IS 1251-1376
A 40 CFR Part 131 - Ambient Suggested ambient standards for the
Water Quality Criteria protection of human health and
. aquatic life.
R&A 40 CFR Part 403 - National Sets standards to control pollutants
Pretreatment Standards which pass through or interfere with
treatment processes in publicly-
owned treatment works or which may
contaminate sewage sludge.
RESOURCE CONSERVATION AND RECOVERY ACT - 42 U.S.C. IS 6901-6987
R&A 40 CFR Part 261_- Identification Defines those solid wastes which are
and Listing of Hazardous subject to regulation as hazardous
Wastes wastes under 40 CFR Parts 263-265
and Parts 124. 270. and 271.
R&A 40 CFR Part 262 - Standards Establishes standards for generators
Applicable to Generators of of hazardous waste.
Hazardous Waste
CLEAN AIR ACT - 42 U.S.C. IS 7401-7642
R&A 40 CFR Part 50 - National Establishes standards for ambient air
Primary and Secondary quality to protect public health and
Ambient Air Quality Standards welfare.
SAFE DRINKING WATER ACT - 40 U.S.C. IS 300
R&A 40 CFR Part 141 - National Establishes maximum contaminant
Primary Drinking Water levels (MCLs) which are health-
Standards based standards for public water
systems.
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TABLE 7-3
POTENTIAL CHEMICAL-SPECIFIC ARARS
R&A PL No. 99-339 100 Stat. 462 Establishes drinking water quality
(1986) - Maximum Contaminant goals set at levels of no known or
Level Goals (MCLGs) anticipated adverse health effects
with an adequate margin of safety.
STATE OF GEORGIA REGULATIONS
R&A Air Quality Act of 1978 O.C.G.A. Establishes standards for ambient air
~ 12-9-1 et sea. and Rules, quality to protect public health and
Chapter 391-3-1. welfare.
R&A Safe Drinking Water Act Establishes maximum contaminant
O.C.G.A. ~ 12-5-170 et sea. levels (MCLs) which are health-
and Rules, Chapter 391-3-5. based standards for pubUc water
systems.
R&A Georgia Water Quality Control Establishes treatment standards for
Act O.C.G.A. ~ 12-5-20 et sea. public water systems.
and Rules, Chapter 391-3-6.
A APPLICABLE REQUIREMENTS WHICH WERE PROMULGATED UNDER FEDERAL
LAW TO SPECIACALL Y ADDRESS A HAZARDOUS SUBSTANCE, POllUTANT, .
CONTAMINANT, REMEDIAL ACTION LOCATION OR OTHER CIRCUMSTANCE AT
THE DIAMOND SHAMROCK LANDFILL SITE.
R&A- RELEVANT AND APPROPRIATE REQUIREMENTS WHICH WHILE THEY ARE NOT
"APPLICABLE" TO A HAZARDOUS SUBSTANCE, POLLUTANT, CONTAMINANT,
REMEDIAL ACTION, LOCATION, OR OTHER CIRCUMSTANCE AT THE DIAMOND
SHAMROCK LANDFILL SITE, ADDRESS PROBLEMS OR SITUATIONS SUFFICIENTLY
SIMILAR TO THOSE ENCOUNTERED AT THE DIAMOND SHAMROCK LANDFILL SITE
THAT THEIR USE IS WELL SUITED TO THE SITE.
8.0
SUMMARY OF THE COMPARATIVE ANALYSIS OF
ALTERNATIVES
This section of the ROD provides the basis for determining which alternative
provides the best balance with respect to the statutory balancing criteria in Section
121 of CERCLA, 42 U.S.C. Section 9621, and in the NCP, 40 CFR, Section 300.430.
The major objective of the FS was to develop, saeen, and evaluate alternatives for the
remediation of the Diamond Shamrock Landfill Site. A wide variety of alternatives
and technologies were identified as candidates to remediate the contamination at the
Diamond Shamrock Landfill Site. These were screened based on their feasibility with
respect to the contaminants present and Site characteristics. After the initial
screening, the remaining alternatives/technologies were combined into potential
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remedial alternatives and evaluated in detail. The remedial alternative was selected
from the screening process using the following nine evaluation criteria:
.
Overall protection of human health and the environment;
.
Compliance with applicable and/or relevant and appropriate Federal or State
public health or environmental standards;
.
Long-term effectiveness and permanence;
.
Reduction of toxicity, mobility, or volume of hazardous substances or
contaminants;
.
Short-term effectiveness or the impacts a remedy might have on the
'community, workers, or the environment during the course of implementation;
.
Implementability, that is, the administrative or technical capacity to carry out
the alternative;
.
Cost-effectiveness considering costs for construction, operation, and
maintenance of the alternative over the life of the project, including additional
costs should it fail;
.
Acceptance by the State; and,
.
Acceptance by the Community.
The NCP categorizes the nine criteria into three groups:
(1)
Threshold Criteria - overall protection of human health and the environment
and compliance with ARARs (or invoking a waiver) are threshold criteria that
must be satisfied in order for an alternative to be eligible for selection;
Primary Balancin~ Criteria - long-term effectiveness and permanence;
reduction of toxicity, mobility or volume; short-term effectiveness;
implementability and cost are primary balancing factors used to weigh major
trade-offs among alternative hazardous waste management strategies; and
(2)
(3)
Modifyin~ Criteria - state and community acceptance are modifying criteria
that are formally taken into account after public comments are received on the
proposed plan and incorporated in the ROD.
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The selected alternative must meet the threshold criteria and comply with all ARARs
or be granted a waiver for compliance with ARARs. Any alternative that does not
satisfy both of these requirements is not eligible for selection and will be removed
from further consideration and comparison. The Primary Balancing Criteria are the
technical criteria upon which the detailed analysis of alternatives is primarily based.
The final two criteria, known as Modifying Criteria, assess the public's and the state
agency's acceptance of the alternative. Based on these final two criteria, EP A may
modify aspects of a specific alternative.
The following analysis is a summary of the evaluation of alternatives for remediating
the Diamond Shamrock Landfill Superfund Site under each of the criteria. A
comparison is made between each of the alternatives for achievement of a specific
criterion.
8.1
THRESHOLD CRITERIA
8.1.1
OVERALL PROTECfION OF HUMAN REALm AND mE
ENVIRONMENT .
The No-Action Alternative will not mitigate the risks associated with contamination
at or originating from the Diamond Shamrock Landfill Site. Therefore, this
alternative is not protective of human health and the environment and will no longer
be considered in this discussion.
Alternative GW-2 would restrict exposure to ground water through restrictions in
ground water usage and drilling until ground water monitoring indicates that ground
water performance standards have been met. Alternatives GW-3 and 4 would
provide for active restoration of the ground water. Alternatives 3 and 4 would
provide the best and most immediate protection of human health and the
environment.
Alternative GW-2 allows the ground water to attain the ground water performance
standards through natural attenuation. This alternatives protects human health and
the environment through preventing any potential exposure to contaminated ground
water and restoring the aquifer in time. Since there is not a current direct exposure
route to ground water and the source has been removed, institutional controls and
natural attenuation of the ground water contamination is protective. Continued
monitoring and performance of five year reviews would confirm that this remedy
remains protective.
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Alternatives GW-3 and 4 treat the contaminated ground water allowing the ground
water to attain performance standards through extraction and treatment. These
alternatives protect human health and the environment through restoring the aquifer
and preventing any potential migration. These alternatives would be the most
protective.
8.1.2
COMPLIANCE WITH ARARS
Alternatives GW-2, 3 and 4, will meet all of their respective ARARs.
Ground water ARARs include Maximum Contaminant Levels (MCLs) that establish
chemical-specific limits on certain contaminants in community water systems. Long-
term monitoring is included in Alternatives GW-2, 3 and 4. - Additional statistical
analysis of data will further substantiate the presence/absence of ground water
contamination.
For Alternative GW-2, remedial action would include further sampling and analysis
of ground water to assure that water beneath the Site would meet ARARs through
attenuation. Surface water currently meets ARARs.
Alternatives GW-3 and 4 would be able to meet all Federal and State standards for
contaminants and proposed actions.
8.2
PRIMARY BALANCING CRITERIA
8.2.1
LONG-TERM EFFECTIVENESS AND PERMANENCE
Alternatives GW-2, 3 and 4 would provide long-term effectiveness and permanence.
Alternative GW-2 would use institutional controls to prevent any potential exposure
to contaminated ground water. Effectiveness of the monitoring program and
attenuation would be evaluated during five-year reviews. Although this alternative
would require additional time to .meet the performance standards, it would likely be
as effective from a long-term standpoint and will be verified during the five-year
reviews. Alternatives GW-3 and 4 would use active ground water restoration and
treatment technologies to reduce hazards posed by the contaminants in the ground
water at the Site. Alternative GW-4 may be most effective since trenches would more
effectively extract contaminated ground water from the complex hydrogeologic
conditions.
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Alternatives GW-2,3 and 4 would require five-year reviews to verify that the cleanup
remained protective.
8.2.2
REDUcnON OF TOXICITY. MOBILITY. OR VOLUME TIfROUGH
TREATMENT
Alternatives GW-3 and 4 would provide for active ground water remediation and
treatment. Alternative GW-2 would not provide for ground water treatment, but
would likely reduce contaminants over time. Toxicity, volume, and mobility of
ground water would be reduced through active restoration in Alternatives GW-3 and
4.
Therefore, Alternatives 3 and 4 would best satisfy CERCLA's statutory preference for
treatment and use of treatment to reduce toxicity, mobility, and volume of
contaminants.
8.2.3
SHORT-TERM EFFECTIVENESS
Alternative GW-2 is expected to have the least short-term risk in execution because
its implementation presents minimal risk to workers, community, and the
environment. Its effectiveness would be achieved over a longer period of time,
although it is expected to achieve a comparable reduction in toxicity.
Alternatives GW-3 and 4 would also be effective in the short-term. Alternatives GW-
3 ~d 4 (ground water treatment) would need additional studies to determine ground
water treatment design specifications. However, these Alternatives would more
quickly remediate ground water contamination through extraction and treatment
The installation of ground water wells or trench excavation may impose risks by
disturbing the contamination in the soil or ground water; however, it is not expected
to pose unacceptable short-term environmental or health hazards, which could not be
controlled.
8.2.4
IMPLEMENTABILITY
Alternative GW-2 would be the simplest to implement and operate. Materials,.
services, capabilities, and specialists would be readily available for implementing the
institutional controls and monitoring program. The ground water monitoring
program would determine the effectiveness of attenuation of the contaminated
ground water.
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Alternative GW-3 and GW-4 would both be the most technically difficult to
implement and would require complex treatability studies and testing to define the
design parameters for these processes. These Alternatives would also likely require
off-site disposal of treatment sludges at regulated off-site facilities.
8.2.5
COST
Cost details are provided in the FS and are summarized below in Table 8-1.
Alternative GW-2, institutional contr918/monitoring, has the lowest present worth
cost and Alternative GW-3, ground water treatment, is high and Alternative GW-4
the highest. Alternatives GW-3 and 4 is significantly more expensive to construct and
operate because of the ground water extraction and treatment componenl Due to the
contaminant source being removed and local ground water flow control asserted by .
Cedar <:reek, Alternative GW-2 provides for the best ratio of costs to benefit received
through the permanent reduction of risks to human health and the environment.
TABLE 8-1
COMPARISON OF COSTS
30 Year Monitoring and
present.wonh Maintenance Cost
Alternative Cost Capital Cost AnnuaU30 year 1
GW-2: Institutional Controls - $ 461,331 $30,360 $ 34,730 I $430,971
and Ground water Monitoring
GW-3: Ground Water $ 5,053,051 $662,682 $353,804 I $4,390,369
Extradion with Wells
GW-4: Ground Water $7,234,449 $881,184 $511,987 I $6,353,265
Extradion with Trenches
1 30 years cost is net present worth cost based on a 79& discount rate.
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8.3
MODIFYING CRITERIA
8.3.1
STATE ACCEPTANCE
The State of Georgia has concurred with the selection of Alternative GW-2 to
remediate the Diamond Shamrock Landfill Site.
8.3.2
COMMUNITY ACCEPTANCE
Based on comments expressed at the March 22, 1994, public meeting and receipt of
one written comment duriitg the comment period, it appears that the Cedartown
community generally agrees with the selected remedy. Specific responses to issues
raised. by the community can be found in Appendix A, The Responsiveness
Summary. .
9.0
SUMMARY OF SELECTED REMEDY
Based upon consideration of the following requirements, EP A has selected
Alternative GW-2, institutional controls and ground/surface water monitoring for this
Site:
.
Trench closure- and soil sampling results confum that the source of
ground water contamination has been removed;
.
The concentrations, of ground water contaminants of concern, that are
above their respective MCLs and/or health-based standards are
variable, sporadic, or appear to be decreasing over time;
.
Cedar Creek appears to be exerting control of ground water flow at the
Site. Contaminated ground water appears to be localized on-site and is
not affecting the Cedartown Public Water. supply. Cedar Creek
sampling results confirm that no detectable levels of these contaminants
of concern are seeping to this surface water; and,
The alternative meets requirements of CERCLA, the NCP, the detailed
analysis of alternatives and public and state comments.
At the completion of this remedy, the risk associated with this Site will be protective
of human health and the environment.
.
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The selected alternative for the Diamond Shamrock Landfill Site is consistent with the
requirements of Section 121 of CERCLA and the National Contingency Plan. The
selected alternative will prevent the future exposure to contaminated ground water at
the Site while reduction of the mobility, toxicity, and volume of contaminated ground
water occurs through natural attenuation processes. In addition, the selected
alternative is protective of human health and the environment, and will attain all
Federal and State applicable or relevant and appropriate requirements, as well as
being cost-effective and utilizing permanent solutions to the maximum extent
practicable.
Based on the information available at this time, the selected alternative represents the
best balance among the criteria used to evaluate remedies. Alternative GW-2 is
believed to be protective of human health and the environment, will attain ARARs,
will be cost effective, and will utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum extent practicable.
A
GROUND WATER MONITORING/RESTORATION
Institutional controls will be implemented to prevent potential exposure to
contaminated ground water. Ground water monitoring will be implemented at this
Site to assess the movement of contamination through ground water.
A.I. I}\e maior components of grounq water monitoring/restoration to be
implemented include:
.
Long-term monitoring of ground water to consist of the following:
1
Ground and surface water monitoring program to confirm that
natural attenuation works and contaminants do not move.
2
Five-year reviews performed in accordance with Section I21(c) of
CERCLA by EP A to assure that human health and the
environment continue to be protected by the remedy, that natural
attenuation continues to be effective, and whether ground water
performance standards continue to be appropriate.
The ground/surface water monitoring program would require
further sampling and analysis to further define background
ground water concentrations of contaminants and the
effectiveness of natural attenuation. This remedy could require
the installation of additional welles). If, based on future sampling
3
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analysis, the background concentration for a contaminant exceeds
its MCL or acceptable risk-based standard, EP A may evaluate
whether ground water performance. standards continue to be
appropriate and may consider amending the performance
standards to background groundwater contaminant
concentrations. Ground/surface water samples would be
collected at intervals to be approved by EP A. Swface water
sampling shall be evaluated to ensure ground water contaminants
do not adversely affect the quality of Cedar Creek waters and
continue to meet Federal and State water quality ARARs. Proper
well construction and development techniques along with a low-
stress sampling method would be used during the ground water
monitoring to determine whether inorganic substances continue
to be a problem.
4
Continued ground water monitoring upon attainment of the
performance standards at sampling intervals approved by EP A.
The ground water monitoring program would continue until EP A
approves a five-year review concluding that the alternative has
achieved continued attainment of the ground water performance
standards listed in Table 9-1 and remains protective of human
health and the environment.
.
Placement of institutional controls to consist of the following to preclude
usage of gro~d water:
1
Implementation of deed restriction(s) or restrictive covenant(s) to
prevent ground water usage and drilling resulting in exposure to
contaminants of concernj and,
2
Completion and maintenance of Site access restrictions (fencing
and signage).
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TABLE 9-1
SUMMARY OF MONITORING PERFORMANCE STANDARDS
(GROUND WATER)
Contaminant Performance Standard (JIg/I)
Manganese 200 a
Toluene 1,000 10
Trich1oroethene 510
1,2, Dichloroethane 510
a - Calculated value based on an acceptable risk or a Hazard Quotient (HQ) of 1.
Exposure assumptions are a 2 liter per day ingestion rate and a 70 kilogram body
weight.
10 - Safe Drinking Water Act Maximum Contaminant Level (MCL).
c.
Compliance Testing
Ground water monitoring shall be conducted at this Site through demonstration of
compliance with all Performance Standards for 2 consecutive sampling events and
continued attainment through the five-year review at the wells approved by the EP A
as compliance points. The five-year reviews shall be performed in accordance with
Section 121(c) of CERCLA by EPA to assure that human health and the environment
continue to be protected by the remedy and that natural attenuation processes are
effective.
10.0
STATUTORY DETERMINATION
Under CERCLA Section 121, 42 US.c. S 9621, EPA must select remedies that are
protective of human health and the environment, comply with applicable or relevant
and appropriate requirements (unless a statutory waiver is justified), are cost
effective, and utilize permanent solutions and alternative treatment technologies or
resource recovery technologies to the maximum extent practicable. In addition,
CERCLA includes a preference for remedies that employ treatment that permanently
and significantly reduce the volume, toxicity, or mobility of hazardous wastes as the
their principal element. The following sections discuss how the selected remedy
meets these statutory requirements.
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10.1
PROTECfION OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy provides protection of human health and the environment by
eliminating, reducing, and controlling risk through engineering controls and/or
institutional controls and ground water treatment, if required as delineated through
performance standards described in Section 9.0 - SUMMARY OF SELECI'ED
REMEDY, subsection A (Ground water Restoration). Ground water monitoring will
be implemented in accordance with performance standards described in Section 9.0 -
SUMMARY OF SELECTED REMEDY, subsection A.l (Ground Water Monitoring) to
ensure that no exposure through ingestion of contaminated ground water occurs.
Institutional controls and ground water monitoring will prevent exposure to
contaminants while natural attenuation occurs over time.
10.2 .
ATI AINMENT OF THE APPLICABLE OR RELEVANT AND
APPROPRIATE REOUIREMENTS (ARARs)
Remedial actions performed under CERCLA, Section 121, 42 U.S.C. S 9621 must
comply with all applicable or relevant and appropriate requirements (ARARs). All
alternatives considered for the Site were evaluated on the basis of the degree to
which they complied with these requirements. The selected remedy was found to
meet or exceed ARARs identified in Tables 7-1,2,3 and 4. The following is a short
narrative in support of attainment of the pertinent ARARs.
Chemical-Specific ARARs -
Ground water restoration performance standards were SDW A MCLs for the
applicable contaminants of concern and surface water sampling shall be evaluated
with federal and State water quality criteria or standards which are consistent with
chemical specific ARARs listed in table 7-3.
Location-Specific ARARs
Performance standards are consistent with ARARs identified in Tables 7-1.
Waivers
Section 121 (d)(4)(C) of CERCLA,42 U.s.e. S 9621(d)(4)(c), provides that an ARAR
may be waived when compliance with an ARAR is technically impracticable from an
engineering perspective. While waivers are not anticipated to be invoked at this Site,
further analysis for verification that background average values will be required.
However, it is anticipated that the contaminated ground water will meet all ARARs
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through attenuation processes.
The selected remedy will require further sampling and analysis to further define
background ground water concentrations of contaminants. If, based on future
sampling analysis, the background concentration for a contaminant exceeds its MCL
or acceptable risk-based standard, EP A may evaluate whether ground water
performance standards continue to be appropriate and may consider amending the
performance standards to background groundwater contaminant concentrations. A
technical infeasibility or inability to attain the ARAR as caused by existing
background ground water conditions as supported by further background sampling
and analysis support may be evaluated as part of an amended performance standard.
Other Guidance To Be Considered
Other Guidance To Be Considered (TBCs) include health-based advisories and
guidance. TBCs have been utilized in estimating incremental cancer risk numbers for
remedial activities at the Sites and in determining RCRA applications to contaminated
media. TBCs for this Site include Guidelines for Groundwater Cassification under
the EPA Groundwater Protection Strategy. Fmal Draft, December 1986.
10.3
COST EFFECTIVENESS
EPA believes the selected remedy, Alternative GW-2 will eliminate the risks to
human health at an estimated cost of $ 461,331. Alternative GW-2 is expected to
achieve a comparable effectiveness at a substantially lower cost (although over a
longer period of time). Alternative GW-2 provides an overall eHectiveness
proportionate to its costs, such that it represents a reasonable value achieved for the
investment as discussed in Section 8.2.5.
10.4
UTIUZATION OF PERMANENT SOLUTIONS TO THE MAXIMUM
EXTENT PRACfICABLE .
EP A and the State of Georgia have determined that the selected remedy represents
the maximum extent to which permanent solutions and treatment technologies can be
utilized in a cost-effective manner for the final remediation at the Diamond Shamrock
Landfill Site. Of those alternatives that are protective of human health and the
environment and comply with ARARs, EP A and the State have determined that this
selected remedy provides the best balance in terms of long-term effectiveness and
permanence, reduction in toxicity, mobility, or volume achieved through treatment,
short-term effectiveness, implementability, and cost, while also considering the
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statutory preference for treatment as a principal element and consideration of state
and community acceptance. The statutory preference for remedies that employ
treatment as a principal element is not satisfied for this Site. The RI data and FS
concluded that remedies which employ treatment technologies are impracticable and
not cost effective at this Site due to low levels of organics and inorganic
contaminants, high volume of inorganic contaminants, and removal of the ground
water contamination source. The selected remedy provides for long-term
effectiveness and permanence, is easily implemented, reduces toxicity, mobility or
volume, and is cost effective.
10.5
PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The selected remedy utilizes treatment technologies to the extent practicable. The
statutory preference for remedies that employ treatment as a principal element is not
satisfied. The RI data and FS concludes that remedies which employ treatment
technologies are impracticable and not cost effective at this Site due to low levels of
organiCs and inorganic contaminants, high volume of inorganic contaminants, and
removal of the ground water contamination source.
11.0
DOCUMENTATION OF SIGNIFICANT CHANGES
There have been no significant changes in the selected remedy, Alternative GW-2,
from the preferred remedy described in the proposed plan.
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APPENDIX A:
RESPONSIVENESS SUMMARY - DIAMOND
SHAMROCK LANDFILL
RECORD OF DECISION
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APPENDIX A:
RESPONSIVENESS SUMMARY - DIAMOND SHAMROCK LANDFILL
RECORD OF DECISION
The U.S. Environmental Protection Agency (EP A) held a 3o-day public comment period from
March 4, 1994, through April 4, 1994 for interested parties to give input on EPA's Proposed Plan
for Remedial Action at the Diamond Shamrock Landfill Superfund Site in Cedar town, Georgia. A
public meeting was conducted on March 22~ 1994, at the Cedartown Public Ubrary, 245 East
Avenue, Cedartown, Georgia. At the meeting, EP A staff presented the results of the Remedial
Investigation and Feasibility Study (RIfFS) and explained EPA's preferred remedy for the Site.
A responsiveness summary is required to document how EP A addressed citizen comments and
concerns, as raised during the public comment period. All comments summarized in this
appendix have been factored into the final decision of the remedial action for the Diamond
Shamrock Landfill Site.
SUMMARY OF MAJOR QUESTIONS AND COMMENTS RECEIVED DURING THE PUBUC COMMENT PERIOD
AND EPA's RESPONSES
ISSUE
1.
How does the dye tracer test performed at the
Henkel waste water treatment plant affect the
results of the RI/Fs and selection of the clean-
up remedy?
EPA RESPONSE
The results of the dye tracer test were considered during the
selection of the remedy. Since RI/FS data indicates that the
source of ground-water contamination has been removed and
that Cedar Creek appears to be exerting control of ground-water
flow at the Site, that contaminated ground water appears to be
localized on-site, is not affecting the Cedartown Public Water
supply, and no significant levels of these contaminants of
concern are seeping to Cedar Creek. Therefore, the selection of
alternative GW-2 as the preferred alternative is protective of
human health and. the environment.
2.
What are the health effects of manganese in
drinking water?
3.
Were any fungicides referenced in the Eckhart
survey found in the landfill?
Per data from the toxicological profile provided in the Baseline
Risk Assessment, individuals who chronically (over the long
tenn) ingest drinking water from wells containing manganese
concen~tions of 1,600 to 2,300 JIg/I, showed a statistically
significant increase in minor neurologic effects (neurologic exam
scores) (I
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Responsiveness 5wnmaJy
Cedartown Municipal Landfill Site
Page ii
SUMMARY OF MAJOR QUESTIONS AND COMMENTS RECEIVED DUlUNG TIlE PUBUC COMMENT PERIOD
AND EPA's RESPONSES
ISSUE
4. Due to apparent high background levels of
manganese and the limited epidemiology
studies of health affects, is continued
monitoring of groundwater needed?
5.
Based on data collected, is potential surface
water contamination from the site-a concern?
6.
Table 1 on page 4 of the proposed plan fact
sheet is misleading in that Toluene,
Trichloroethene and 1,2 Dich1oroethane should
not be contaminants of ooncem.
EPA RESPONSE
A high level of manganese (Mn) were detected in the June 1993,
MW-10 (background well) ground water sampling result. After
reviewing the information, EPA concluded that the June 1993,
MW-10 sample was probably not representative for detennining
background ground-water concentrations and utilization for use
in determining ground water performance or clean-up standards.
Firstly, when comparing the filtered versus non-filtered data, it is
evident that there is a significant differenre in this data which is
not apparent in any of the other samples.
Secondly, in the previous and post samples of MW-10 and in the
. other background well (MW-1), Mn was detected at much lower
concentrations than 1800 ug/l. Sample results from other
sampling events (highest detected was 94 JIg/I) indicates the
spike of 1800 Jlg/I is not an accurate characterization of water
quality at this well.
Therefore, the remedy includes a ground-water monitoring
program to further define background ground water
concentrations of con1aminants. H, based on future sampling
analysis, the background concentration for a contaminant exceeds
its performance standard, EP A may evaluate whether ground
water performance standards continue to be appropriate and
may consider amending the performance standards 10
background ground-water contaminant concentrations.
Surface waters do not present a current unacxeptable health risk.
However, since contaminated water does discharge 10 Cedar
Creek, surface samples will continue to be collected 10 confirm
that contaminants ooncentrations do not present an unacceptable
risk 10 human health and the environment in this surface water.
Toluene, Trichloroethene, and 1,2 Dichloroethane have been
detected above their respective drinking water standard in
ground water during various RI/FS sampling events. While
none of these oontaminants were detected above their respective
detection limits during the January 1994 sampling event. it is
premature to conclude that these compounds are no longer
contaminants of ooncern and not should be analyzed for. H
future monitoring under the selected remedy indicate that these
constituents meet the ground water performance staIIduds, EP A
can discontinue analyzing for that particuJar oonstituent.
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Responsiveness Summary
Cedartown Municipal Landfill Site
Page ill
SUMMARY OF MAJOR QUESTIONS AND COMMENTS RECEIVED DURING THE PUBUC COMMENT PERIOD
AND ErA's RESPONSES
ISSUE
7. Table 1 on page 4 is misleading since
comparisons were made of the highest
detected concentration to the average
background for a particular contaminant.
8.
All background results should be considered
and data supports that the manganese in
ground water is likely naturally occurring.
9.
The perfonnance standard of 200 11g/1 is based
on a single epidemiological study and includes
a great deal of uncertainty.
EPA RESPONSE
The purpose of this table was to show what the contaminant
reasonable maximum exposure mncentration that was used in
the risk assessment process to determine if an unacceptable
health risk exists and to establish ground water clean up or
performance standards.
Since a comparison of reasonable maximum detection to average
background was utilized in the risk assessment process to
detennine if a mnstituent is a potential mntaminant of concern,
the average background concentration was represented in this
table.
The data does not support that manganese in ground water is
naturally occurring. MW-IO results indicate only one sample
above the performance standard of 200 pg/l as discussed in
response #4; therefore, EP A has concluded that additional
background data will be required as part of the selected remedy
to confinn and further define background water quality.
The perfonnance standard of 200 11g/1 for manganese will
remain as part of the selected remedy until and if future
sampling analysis indicates that background concentration for
manganese exceeds the acceptable risk-based standard of 200
11g/L EP A will evaluate this data and determine whether
ground water performance standards continue to be appropriate
and whether amending the performaI1Ce standards to
background ground-water contaminant concentrations is
appropriate.
EP A considered in the selection of this remedy that there is a
degree of uncertainty regarding the toxicity of manganese in the
ground water ingestion scenario.
Due to the uncertainty associated with the present RfD (the
amount that can be ingested daily without adverse affect) for
manganese, the RID determination is scheduled for future EP A
review. The current EPA RID for manganese in water of
O.oos mg/kg/day was used to evaluate risks concerning
manganese drinking water intake and in establishing clean-up
goals. EP A may evaluate and modify the clean-up standard as
stated in the selected remedy, if the RfD for manganese is
revised.
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Record of Dec:isicn
Cedartown Municipal Landfill Site
Page 78
APPENDIX B:
STATE OF GEORGIA CONCURRENCE LEITER
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SOUTH
SUPERFUND
ArR 5 I 11 rM. '9~,
R E: r~~ :: ~d A L
BRANCH
Mr. Richard Green
Associate Division Director
Office of Superfund
U.S. EPA, Region IV
345 Courtland Street, N.E.
Atlanta, Georgia 30365
Georgia Department of Natural Resources if'1
205 Butler Street, S.E., Suite 1154 Atlanta, Georgia 30334
Joe D. Tanner. Commissioner
Environmental Protection Division
Harold F. Reheis. Director
404/656-2833 404/656-7802
March 29, 1994
-I,,,,l t1;. k
/ / l CLj.(V IC' '
RE:
Record of Decision
Diamond Shamrock Landfill NPL Site
Dear Mr. Green:
The Georgia Environmental Protection Division (EPD) has reviewed the Record of
Decisior'l, Summary of Remedial Alternative Selection for the Diamond Shamrock Landfill
Site in Cedartown, Georgia. EPD concurs with the selected remedy in which the major
components include: a deed restriction or restrictive covenant for ground water usage,
completion and maintenance of site access restrictions, and a ground water and surface
water monitoring program.
If you have any questions, please contact Penny Mingst at (404) 656-2833.
Sincerely,
~Q \\~~\J
..
Harold F. Reheis
Director
HFR/pm
cc:
Jay V. Bassett
file: Diamond Shamrock Landfill NPL Site
. .
R:\PENNY\DIASHAM.NPL\ROD.L TR
. .
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