,
(/
United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
PB93-964101
EP NROD/R05-92/195
February 1992
J
&EPA
Superfund
Record of Decision:
Grand Traverse Overall
Supply, MI
u . ~. Environmental Protection Agency
ReglO~ 11/ Hazardous Waste
Techmcallnformatic)n Center
8~ 1 Chestnut St((}e~. 9th floor
PhIladelphia I PA ~910T
----
~----.....
.-
--- ----.....
-:;.~
EPA Report Collection
Information Resource Center
US EPA Region 3
Philadelphia, PA 19107
Hazardous Waste Correction
rnformatlon Resource Center
US EPA Region 3
Philadelphia" PA 19107
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','-
NOTICE
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement. but adds no further applicable information to
the content of the document. All supplemental material is, however, contained in the administrative record
for this site.
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"
50272-101
REPORT DOCUMENTATION 11. REPORTNO.
PAGE EPA/ROD/R05-92/195
I ~
3. Reclplent'8 ACC888Ion No.
~
4. Tille and SUb1I1Ie
SUPERFUND RECORD OF DECISION
Grand Traverse Overall Supply, MI
First Remedial Action - Final
7. AuIIIor(8)
5. Report Date
02/03/92
6.
8. Perlonnlng Organlzallon Rept. No.
9. Perlonnlng Orgalnlzallon Name and Addl'988
10. f'roIectfTaskIWork Unit No.
11. ConInIct(C) or Gr8nt(G) No.
(C)
1~ Spon8OrIng Organlzallon Name and Addre88
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
(G)
13. Type 01 Report & Pet1oc1 Covered
Agency
800/000
14.
15. Supplementary No1D8
PB93-964101
16. Ab81ract (UmIt: 200 Word8)
The 3.9-acre Grand Traverse Overall Supply (GTOS) site is an active commercial
laundering facility in Greilickville, Leelanau County, Michigan. Land use in the area
is residential, with an elementary school directly east of the site. The site
overlies both an unconfined aquifer and a semi-confined aquifer. Surface water in the
area includes Cedar Creek, which is dammed and discharges to the unconfined aquifer
located upstream of the dam, and ground water discharges into the creek downstream of
the dam. From 1953 to 1977, the GTOS facility discharged laundry and process wastes
from dry cleaning operations onsite to seepage lagoons and a dry-well. After 1977
laundry and process wastes were diverted to the sanitary sewer system. From 1968 to
1978, cooling water used in onsite dry cleaning operations was discharged to Cedar
Creek. In 1978, the state detected VOCs, including PCE, TCE, and 1,2 DCE, in the
water supply of the adjacent elementary school and condemned the well. Additional
well sampling by the state determined that, as a result of disposal operations, the
GTOS site was the likely source of the contaminants. From 1978 to 1980, the state
required GTOS to conduct removal actions, which included replacing the contaminated
drinking water wells and excavating the onsite dry well and adjacent contaminated
(See Attached Page)
17. DOCWMnt Analysl8 a. Descriptors
Record of Decision - Grand Traverse
First Remedial Action - Final
Contaminated Media: Not applicable
Key Contaminants: Not applicable
Overall Supply, MI
b. Idenafter81Open-Ended Terms
c. COSATI Reid/Group
18. AvailablUty StaIemenI
19. SecurIty Class (Th18 Report)
None
20. SecurIty Class (thIs Page)
None
21. No. 01 Pages
29
I
~ PrIce
(See ANSI-Z39.18)
See InstructlOlls on Reverse
OPTIONAL FORM 272 (4-77)
(Formerty NTlS03S)
Deplll1ment or Commerce
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EPA/ROD/R05-92/195
'Grand Traverse Overall Supply, MI
First Remedial Action - Final
~
Abstract (continued)
soil, followed by offsite disposal of excavated materials; filling three of the four
seepage lagoons with gravel, followed by paving; backfilling the remaining lagoon and
revegetating the area. In 1978, dry cleaning operations were discontinued, but the GTOS
site remains active and continues to discharge wastes into the sanitary sewer system.
This ROD addresses the potential risks posed by onsite ground water. As a result of
previous removal actions, organic compounds present in low levels in soil, and organic
and inorganic compounds present in ground water no longer pose an unacceptable risk to
human health or the environment; therefore, there are no contaminants of concern
affecting this site.
The selected remedial action for this site is the no action alternative; however, ground
water monitoring for inorganics will continue for 1 year.EPA has determined that
conditions at the site due to contamination by organic compounds pose no current or
potential threat to human health or the environment. There are no costs associated with
this no action remedy.
PERFORMANCE STANDARDS OR GOALS:
Not applicable.
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DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Grand Traverse Overall Supply Site, Greilickville, Michigan.
10
STATEMENT OF BASIS
This decision document presents the selected .remedial action for the Grand Traverse Overall
Supply Site, in Greilickville, Michigan, which was chosen' in accordance with the
Comprehensive Environmental Response, Compensation, and Liability act of 1980 (CERCLA),
as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA) and is
consistent with the National Oil and Hazardous Substances Pollution Contingency Plan (NCP)
to the extent practicable. This decision is based upon the contents of the Administrative Record
for the site.
The S tate of Michigan does not concur with this Record of Decision.
:".
DESCRIPTION OF THE SELECTED REMEDY
u.S. EPA (EPA) has selected "No Action."
DECLARATION
EP A has determined that conditions at the site due to contamination by organic compounds pose
no current or potential threat to human health or the environment. While the GTOS site does
appear to exhibit trace amounts of inorganic contamination which result in slightly elevated
calculations of potential future risk, EP A has also determined that the presence of these
compounds does not appear to pose an unacceptable risk to human health or the environment.
Accordingly, no further remedial action will be undertaken. EPA will, however, continue to
monitor the inorganic contaminants in the grou~dwater for a period of twelve months.
, .
As this is a decision for "No Action", the statutory requirements of CERCLA Section 121 for
~; :n1/;;: awfiab~ ~ no fiw y= -~ T"
DATE Valdas . Adamkus
Regional Administrator
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1.
II.
III.
IV.
V.
VI.
VII.
VIII.
~.
"
0'
TABLE OF CONTENTS
Site Description[[[ 1
Site History and Enforcement Activities..............................................
1
Highlights of Community Participation................................................ 4
Scope & Role of Response Action... ......................... .~. .......................4
Site Characteristics[[[ 4
Ftis]c }\ssesSDaent [[[ 17
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Figures
L
2.
...
3.
4.
5.
6.
7.
:.t 8.
Tables
2.
FlGURES and TABLES
Area Map.............................. ........ ................ ............................. 2
Site Map[[[ 3
Hydrologic Cross Section of GTOS site ............................................... 6
Phase I Soil Boring Locations[[[ 9
Phase II Soil Boring Locations[[[ 9
Stream Surface Water and Sediment Sample Locations ............................. 10
Monitoring Wells Locations[[[ 12
Residential Wells Locations............... ....... ............. ........................... 13
1.
Soil Background Data-Inorganic Contaminants in #Lglkg ........................... 7
Analytes Detected in Soil Samples at GTOS .......................................... 8
3.
Organic Analytes Detected in Sediment Samples at GTOS ........................ 10
4.
Analytes Detected in Groundwater Samples at GTOS .............................. 14
5.
Conceptual Exposure Model of Potential Human Exposure Pathways........... 20
6.
Summary of Noncarcinogenic Health Risks Associated with Site Worker and Site
T~r Exposure S~o [[[ 22
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GRAND TRAVERSE OVERALL SUPPLY
GREILICKVll..LE, MICHIGAN
SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
:.t
FEBRUARY 1992
. .
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..
DECISION SUMMARY
I. SITE DESCRIPTION
Grand Traverse Overall Supply Company (GTOS) site is located in Greilickville, Michigan,
approximately 1-1/2 miles north of the city limits of Traverse City, Michigan (Figure 1). The
3.9 acre site is in the SE 1/4 of section 28, T28N, RllW, Elmwood Township, Leelanau
County, located just west of Highway M-22, on the north side of Cherry Bend Road and south
of Cedar Creek (Figure 2).
..
The area surrounding the GTOS facility is primarily residential. The Norris Elementary School
is directly east of GTOS, and east of the school are residential homes. The Elmwood Volunteer
Fire Department is south of GTOS, followed by more residential homes. Residential homes
border GTOS to the west; to the north is Cedar Creek.
ll. SITE HISTORY AND ENFORCEMENT ACTIVITIES
~I
Grand Traverse Overall Supply Company performs commercial laundering for industrial
clothing. The laundry facility began operations in 1953. A dry cleaning facility was added in
1968. Until December 1977, the laundry wastes and process wastes from dry cleaning
operations were discharged to seepage lagoons and a dry-well on the site. Cooling water used
in dry cleaning operations was discharged to the Cedar Creek from 1968 to 1978. The
Company began discharging its laundry and process wastes to the sanitary sewer system in
December 1977, and the cooling water was also diverted to the sanitary sewer system beginning
in 1978. Dry cleaning operations at GTOS were discontinued in 1987. The company is
operating on the site at the present, and is discharging the wastes into the sanitary sewer system.
In April 1978, traces of perchloroethene (PCE), trichloroethene (TCE), and 1,2 dichloroethene
(1,2 DCE) were detected in the water supply of Norris Elementary School, located immediately
east of the GTOS site. The Michigan Department of Public Health condemned the school well
water for consumption and conducted sampling of additional wells in the area. The sampling
program confirmed the contamination of 10 drinking water wells. The GTOS site was
considered the likely source of the contaminants.
Remedial action was taken by GTOS under Michigan Department of Natural Resources (MDNR)
supervision from 1978 to 1980. This included replacing contaminated drinking water wells with
new wells that extended into a deeper uncontaminated semi-confined aquifer, and excavating the
on-site dry well and adjacent contaminated soils, with off-site disposal of excavated materials.
In additio.n, three of the four lagoons were gravel filled, covered with asphalt, and converted to
a parking lot. The fourth lagoon was backfilled and ultimately returned to a grassy area.
The MDNR performed a biological evaluation of the Cedar Creek in October-November of 1978'
to determine if wastewaters from the GTOS site, discharged into the lagoons and to the Cedar
Creek, had damaged the indigenous aquatic plant and communities in the creek. The study
concluded that the aquatic animal community in the Cedar Creek, downstream from GTOS was
seriously degraded compared to the upstream community.
1
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3
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".
The MDNR also conducted a hydrogeologic investigation of the site and surrounding area and
issued a repon of the investigation, in February 1981. The repon concluded that the GTOS site
had been the source of the TCE, PCE, and 1,2 DCE contamination of the shallow useable
unconfined aquifer in the area.
The site was placed On the National Priorities List (NPL) in September 1983 because of
groundwater contamination of the useable unconfined aquifer with PCE and TCE.
m. HIGHLIGHTS OF COl\1MUNITY PARTICIPATION
On November 29, 1989 EP A hosted a Remedial Investigation Kick-off Meeting at the Elmwood
Township Hall, Michigan. Approximately 30 citizens attended this meeting.
The Proposed Plan was released to the public for comment on October 15, 1991. The public
comment period concluded November 14, 1991. The Proposed Plan provided the public with
the opponuniry to request a Public Meeting to discuss the Remedial Investigation (RI) findings
and the proposed alternative.
:.1
The public panicipation requirements of CERCLA sections 113 (k) (2) (B) (i-v) and 117 have
been met in the remedy selection process. This decision document presents the selected remedial
action for the GTOS site, in Michigan, chosen in accordance with CERCLA, as amended by
SARA and, to the extent practicable, the NPL. The decision for this site is based on the
administrative record.
IV. SCOPE & ROLE OF RESPONSE ACTION
EP A recommends that no further remedial action be taken at the GTOS site for the following
reasons. Organic compounds, found in low levels in the soils, pose no current or potential
threat to human health or the environment. Levels of organic and inorganic compounds present
in groundwater do not appear to pose an unacceptable risk to human health or the environment.
No five year review will be undertaken, but EP A will continue the monitor the groundwater for
a period of twelve months.
V. SITE CHARACTERISTICS
, .
Tf1e RI was conducted in two stages. Stage I began November 1989 and was completed in
February 1990, stage II was completed in November 1990. The RI also included a Risk
Assessm~nt to evaluate the level of risk to human health and the environment. This section
summarizes the analysis presented in the RI report:
A) Site TOp02l"aDhy
The GTOS site is located near the base of the Leelanau Peninsula. The peninsula and
surrounding area are dominated by landforms left by the Wisconsin glaciation (Martin 1957).
The GTOS site is relatively flat, with an average ground surface elevation of 600 feet above
mean sea level (MSL; U.S.G.S., 1983). The relatively flat topography at the site is due to its
4
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being pan of ancestral lake beds formed when the Wisconsin glaciation retreated. To the east
of Highway M-22 (approximately 1,000 feet east of GTOS), the elevation sharply drops
approximately 20 feet to the shore of the West Arm of Grand Traverse Bay.
Approximately 1 mile west of the study area, the surface elevation begins to rise to a maximum
elevation of approximately 1,100 feet, and the topography becomes rolling hills. Sandy glacial
moraines and sand dunes along ancestral shorelines are also found west of the GTOS site.
..
B) Site GeOlO2V
The GTOS site is covered by glacial surficial deposits. The underlying bedrock formations in
the region are (in descending order) the Devonian Ellswonh shale, the Devonian Antrim shale,
~nd the Devonian Traverse limestone. These formations outcrop and pinch out from southeast
to nonhwest, respectively, as pan of the Michigan Basin structure.
:.1
The glacial surficial deposits form a sandy soil at the GTOS site. The soil is classified as
Kalkaska-East Lake loamy sand. These deposits are lacustrine in origin and were formed by the
glacial lakes ancestral to the Great Lakes.
According to boring logs, the subsurface sequence of formations at GTOS consists of 4' to 5 feet
of sand mined with gravel, overlying a 5 to 10 foot layer of sand and large cobbles. Beneath
this horizon is a layer of sand and gravel (Kimmel, 1981).
C) Site Surface Water Hvdrolo2v
The West Arm of Grand Traverse Bay, Cedar Lake, and Cedar Creek are the major surface
water bodies near the GTOS site. The surface and subsurface hydrology around the GTOS site
is controlled by these water bodies. The Cedar Lake watershed encompasses 3,946 acres, with
the lake occupying 253 acres. The maximum depth of the lake is 13.7 meters in a small area
near the outlet. The watershed is drained by Cedar Creek, a perennial stream. Cedar Creek
passes over a damlspillway located just east of Highway M-22, and then discharges to the West
Arm of Grand Traverse Bay. . . . '
D) Site Groundwater Hvdroloey
Two aquifers are located beneath GTOS: an unconfined aquifer that is about 45-65 feet thick and
a semi~orifined aquifer that is at least 55 feet thick, beneath the unconfined aquifer. Figure 3
represents a hydrologic cross section of the area of study. The flow of groundwater is generally
in a south/southeast direction. The unconfined aquifer is recharged by infiltration of
precipitation throughout the study area. Recharge to the lower semi-confined aquifer probably
occurs, via vertical infiltration through the confining unit.
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MDNR concluded that the creek was in a semiperched state above the dam and that some
groundwater therefore flows beneath the creek. Due to the dam located on Cedar Creek. the
creek discharges to the unconfined aquifer upstieam from the dam. Downstream from the dam.
the groundwater discharges to the creek.
eros rACllIN -
- NORRIS ElE"ENTARY
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HORIZONTAL SCALE
Figure 3 Hydrologic Cross Section of GTOS site
E} EXTENT OF CONTAMINATION
1)SJW.i
The flI'St stage of sampling of the RI included five soil borings and the collection of 67 soil
samples from depths of 3 to 68 feet. These samples were analyzed for YOCs, SVOCs, and
inorganics. During the second stage of sampling additional soil sampling was conducted in the
lagoon areas. A total of 16 auger borings were drilled, and 22 soil samples were collected for
analysis o{ YQCs.
The concentrations of inorganics detected on the soil samples fall within typical average
background concentrations for the State of Michigan (see Table 1).
Soil samp1~ taken from the five potential source areas, the dry well area and the four former
lagoons, exhibited slight contamination, primarily by organic compounds. Lagoon areas 2, 3,
and 4 have been converted to a parking lot. The dry well area and former lagoon No.1 are
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Table 1 Soil Background Data-Inorganic ContaminantS in
p.gJkg
..
COTllaminaTll
Michigan Background
Soil Data - Sands
U.S. National
Background
:1
Aluminum
Antimony
Arsemc
Barium
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Selenium
Silver
Thallium.
Vanadium
Zinc
1317
NA
0.8
10.5
NA
0.6
NA
3.3
2.5
4.6
1630
16.3
NA
199.3
0.04
6.1
NA
0.23
0.2
NA
NA
11.3
71000
6
5-6
430-500
6
0.06
13700
100
8
20-30 .
38000
29
5000
600-850
0.098
40
14000
0.4
0.4
0.2
100
50
..
used as storage areas. Figures 4 & 5 show soil sampling locations. Table 2 provides a
summary of the data. TCE and/or PCE were detected in the dry well area, former lagoon No.
1, and former lagoon No.3. Most of the concentrations were less than 400 p.g/kg, except in
a sample from former lagoon No.3, where tetrachloroethene was found at 3,500 p.glkg.
Samples from former lagoons No.2, No.3, and No.4 also contained BTEX compounds
(benzene, toluene, ethyl benzene, and xylene), which are major constituents of hydrocarbon
fuels. Concentrations of these compounds were less than 500 p.g/kg except for one detection of
xylene at 960 p.glkg in former lagoon No.2. In the dry well area and in the four fonner
lagoons, a number of organic Tentatively Identified Compounds (TICs) were found.
Concentrations of these TICs were "as high'as 24,000 p.glkg, although these were estimated
values. However, since several of the TICs detected in the source areas were also detected in
the background soil sample, some of the compounds may be naturally occurring. These TICs
were primarily long chain aliphatic hydrocarbons and aromatic compounds.
2) Surface Water and Stream Sediment
Six stream sediment samples and three surface water samples from the Cedar Lake Outlet were
taken during the" first stage of sampling of the investigation (See Table 3). Figure 6 shows
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Table 2 Analytes !>etected in Soil Samples at GTOS
Range of Detected
Frequency Concentrations
of
Chemical (J.Lg/Kg) Detection Minimum Maximum
Volatiles
Methylene Chloride 4/22 1 6
Acetone 6/23 8 38
Trichloroethene 1/3 4 4
T etrachloroethene 4/20 2 3500
Toluene 2/19 1 170
Ethyibenzene 1/18 41 41
Xylenes(total) 4/18 12 960
Semivolatiles
\1 bis(2- Ethylhexyl)Phtalate 3/4 640 15000
Di-n-Octyl Phtalate 1/1 43 43
Inor~anics (mg/Kg)
Aluminum 5/5 601 1330
Arsenic 2/4 0.31 0.68
Barium 5/5 3.4 18.7
Calcium 5/5 10700 78100
Chromium 5/5 3.2 8
Cobalt 1/1 4.4 4.4
Copper 5/5 9.3 46.3
Iron 5/5 1280 3300
Lead 5/5 - 0.99 44.1
Magnesium 5/5 3460 12000
Manganese 5/5 17.2 95.4
Mercury 1/3 0.59 0.59
Nickel 1/1 3.7 3.7
Potassium 2/2 127 187
Sodium 3/3 108 151
Vanadium 5/5 2.2 5.7
Zinc 5/5 7 37.6
8
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Table 3 Organic Analytes Detected in Sediment Samples at GTOS
. .
Chemical (~gll)
Frequency
of
Detection
Range of Detected
Concentrations
Minimum
Maximum
Volatiles
Acetone
Carbon Disulfide
2-Butanone
Toluene
2/5
1/5
1/5
5/5
72
46
66
65
520
46
66
1200
surface water and sediment sampling locations. Toluene was detected in sediments upstream and
downstream from the site. Except for a trace amount of toluene in an upstream sample, no
VOCs were detected in the surface water samples. The most likely source of the toluene in the
surface water and sediments is the use of fuel in boats on Cedar Lake. and possible releases
from storage facilities at service stations and marinas in the area.
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Figure 6 Stream Surface Water and Sediment Sample Locations
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3) Groundwater
",
While low levels of chlorinated hydrocarbons and BTEX compounds were detected in all three
of the groundwater monitoring zones of the field investigation: the shallow portion of the
unconfined aquifer, the deep portion of the unconfined aquifer, and the semi-confined aquifer,
the concentrations and quantities of contaminants detected were not the same for both rounds.
The concentrations detected on stage II were lower. Low levels of inorganic compounds were
also detected in the unconfined aquifer. However, no maximum contaminant levels (MCLs)
other than antimony were exceeded. The presence of antimony at levels greater than its MCL
of 10 /-Lg/I was not considered significant due to unreliable data resulting from the sample blanks
containing high levels of antimony. Antimony was eliminated from further consideration.
During the fIrSt stage of sampling, 43 groundwater samples were collected from 22 monitoring
wells and 36 samples were collected from 28 residential wells. These samples were analyzed
for Volatile Organic Compounds (VOCs) and Semi-Volatile Organic Compounds (SVOCs). Six
samples from the monitoring wells were analyzed for inorganics. In the second stage, samples
were collected from 10 monitoring wells and 10 residential wells and analyzed for VOCs.
..
:.t
Existing MDNR monitoring wells were paired with new EP A monitoring wells to form nests of
wells that would provide samples throughout the unconfined aquifer. The MDNR monitoring
wells were screened in the shallow part of the unconfined aquifer; monitoring wells installed by
EPA were screened in the deep part of the unconfined aquifer. Figure 7 shows the locations of
the monitoring wells. Most of the residential wells were screened in the semi-confined aquifer.
Figure 8 shows the location of the residential wells. Table 4 summarizes the results of the
groundwater stages of sampling. The results from stage I and stage II have been combined.
a) Unconfmed Aquifer
Very low concentrations of three semivolatile compounds were found samples taken from the
upper unconfined aquifer, indicating that the GTOS site does not contribute to semivolatile
contamination of the groundwater. In the stage I sampling of the shallow portion of the
unconfmed aquifer, trichloroethene, tetrachloroethene, cis-l,2-dichloroethene and toluene were
detected in low concentrations (0.6 to 3 /-Lgll) down gradient of the source areas of GTOS.
Similar concentrations of trichloroethene and cis-l,2-dichloroethene were also detected in the
background well upgradient of GTOS. In the stage II sampling, cis-l,2-dichloroethene, trans-
1,2-dichloroethene, trichloroethene, and 1,2-dichlorobenzene (0.5 to 3.3 /-Lg/I) were detected
down gradient of the source areas.
In the deep portion of the' unconfined - aquifer, the first stage of sampling detected
tetrachloroethene, trichlorofluoromethane, bromomethane, chlorobenzene, and 2-chlorotoluene
in low concentrations (0.07 to 0.7 /-Lgll) down gradient of the source areas of GTOS. In the
second stage of sampling for the deep portion of the unconfined aquifer, only tetrachloroethene
was detected (0.95 #Lg/I).
During stage I of sampling, low levels of inorganic compounds were detected in the shallow and .
deep portions of the unconfined aquifer. These included aluminum, arsenic, barium, calcium,
copper, lead, magnesium, manganese, potassium, silver, sodium, vanadium and zinc. Many of
these same inorganic compoUnds were also found in samples designated as background and in
the tap water obtained from the municipal water supply available at the Traverse City Fire
Station. The municipal water, used in the remedial investigation, is pumped from the East Arm
of Grand Traverse Bay and treated.
11
-------
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13
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. .
Table 4 Analytes Detected in Groundwater Samples at GTOS
"
Range of Detected
Frequency Concentrations
of
Chemical (~g/l) Detection Minimum Maximum
UPGRADIENT MONITORING WELLS
Volatiles
Methylene Chloride 2/2 1 2
1,2-Dichloroethene(total) 1/2 2 2
Trichloroethene 1/2 3 3
Semivolatiles
Phenol 1/1 1 1
....' Fluorene 1/1 0.09 0.09
bis(2- Ethylhexyl)Phtalate 1/1 0.1 0.1
Ino~anics
Antimony 2/2 18.6 21.1
Arsenic 1/2 1.4 1.4
Barium 2/2 12.8 28.2
Calcium 2/2 50600 77500
Chromium 2/2 6.1 7.6
Copper 2/2 4.6 7.7
Iron 2/2 81.3 428
Lead 1/2 3.9 3.9
Magnesium 2/2 15400 16700
Manganese 212 ' 3.8 52
Nickel 1/2 15.6 15.6
. Potassium 2/2 641 843
Selenium 1/2 2.5 2.5
Sodium 2/2 4900 6500
Thallium 1/2 1.1 1.1
Vanadium .2/2 3.4 5
Zinc 2/2 8.1 19.4
-14
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, .
Table 4 (Cont.) Groundwater Samples
Range of Detected
Frequency Concentrations
of
Chemical (~g/l) Detection Minimum Maximum
RESIDENTIAL WELLS
it
Volatiles
Bromomethane 2/24 0.29 0.38
1,1- Dichloroethene 1/24 0.33 0.33
1,2- Dichloroethene(total) 1/1 0.07 0.07
1,2-Dichloroethane 1/24 0.09 0.09
Carbon Tetrachloride 1/24 0.09 0.09
Bromodichloromethane 1/24 1.32 . 1.32
1,2-Dichloropropane 1/24 0.10 0.10
Trichloroethene 1/24 0.14 0.14
:; Dibromochloromethane 1/24 0.73 0.73
Bromoform 1/24 0.14 0.14
Tetrachloroethene 6/24 0.05 0.24 .
Styrene 2/24 0.09 0.10
Bromobenzene 1/24 0.08 0.08
Bromochloromethane 1/4 0.14 0.14
sec- Butylbenzene 1/24 0.13 0.13
tert- Butylbenzene 1/24 0.10 0.10
2-Chlorotoluene 3/24 0.12 0.15
4-Chlorotoluene 1/24 0.10 0.10
1,2-Dibromoethane 1/1 0.03 0.03
1,3-Dichloropropane 1/24 0.04 0.04
2,2-Dichloropropane 1/1 0.07 0.07
Isopropylbenzene 1/24 0.12 0.12
n-Propylbenzene 2/24 ' 0.15 44
1,1,1,2- Tetrachloroethane 1/24 0.06 0.06
1,2,3- Trichloropropane 1/1 0.06 0.06
1,3,5- Trimethylbenzene 1/24 0.11 0.11
1,2,4- Trimethylbenzene 1/24 0.10 0.10
Semivolatiles
1,2- Dichlorobenzene 1/24 0.09 0.09
1,3- Dichlorobenzene 1/24 0.07 0.07
1,2,4- Trichlorobenzene 1/24 0.58 0.58
. Hexachlorobutadiene 2/24 0.17 0.35
15
-------
. .
Table 4 (Cont.) Groundwater Sampies
Range of Detected
Frequency Concentrations
of
Chemical (~g/l) Detection Minimum Maximum
ON-SITE MONITORING WELLS
Volatiles
Methylene Chloride 6/20 0.5 0.9
Carbon Disulfide 4/20 2 4
1,2- Dichloroethene(total) 1/20 8.5 8.5
1, 1, 1-Trichloroethene 5/20 0.5 7
Trichloroethene 3/20 0.5 1.7
Bromodichloromethane 1/20 0.6 0.6
Toluene 1/20 0.6 0.6
T etrachloroethene 3/20 0.9 3.3
~.t
Semivolatiles
1 ~2-Dichlorobenzene 1/20 0.6 0.6
bis(2- Ethylhexyl)Phtalate 2/2 0.3 0.3
Ino~anics
Aluminum 5/6 79 797
Antimony 4/6 18 26.2
Arsenic 4/6 1.3 8.6
Barium 6/6 18.8 52.9
Cadmium 1/6 2.6 2.6
Calcium 6/6 .66100 93400
Chromium 1/6 ' 10.3 10.3
Copper 5/6 3.4 6.6
Iron 6/6 529 1960
Lead 6/6 1.2 23
Magnesium 6/6 13100 20800
Manganese 6/6 12.6' .. 204
Nickel 1/6 15.2 15.2
Potassium 6/6 725 1570
. Selenium 1/6 1.7 1.7
Silver. 5/6 9.2 12.6
Sodium 6/6 3510 8230
Vanadium 6/6 5.2 11.9
Zinc 6/6 5.2 1680
16
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. .
'.
b) Semi-commed Aquifer
In the semi-confined aquifer, 33 individual compounds were detected down gradient of the GTOS
site in low concentrations (0.09 to 0.58 ~g/l). The down gradient sample detected halogenated
compounds, commonly used as solvents, and substituted aromatic compounds, commonly used
in fuels. The upgradientsample detected substituted aromatic compounds only. No VOCs were
detected in the stage II of sampling of the semi-confined aquifer.
VI. RISK ASSESSMENT
The analytical data collected during the RI indicated the presence of contaminants in various
media. Pursuant to the NCP, a baseline risk assessment was performed based on present
conditions at the site. The baseline risk assessment determines actual or potential risks or toxic
effects the chemical contaminants at the site pose under current and future land use assumptions.
The risk assessment assumes no corrective action will take place and that no site use restrictions
or institutional controls such as fencing, groundwater use restrictions or construction restrictions
will be imposed. The baseline risk assessment included the following specific assumptions:
..
.
Contaminated aquifers may be used as a drinking water source;
.
The site may be used for residential development;
:i
.
Access restrictions such as fencing will not preclude potential trespassers from
getting into the site; and
.
No groundwater use restrictions will be enforced.
A) Contaminant Identification
The media of concern for human exposure were identified as groundwater, soil, sediment, and
surface water. A list of contaminants found at the site was developed to determine the
contaminants of concern for GTOS. Those contaminants that were reported very infrequently
and at low concentrations were eliminated from further consideration as contaminants of
concern. All carcinogenic contaminants were included as contaminants of concern. The
compounds selected as contaminantS of concern' for the baseline risk assessment include:
Methylene Chloride
Carbon Tetrachloride
Bromomethane
Bromodichloromethane
Dibromochloromethane
Bromoform
Carbon Disulfide
1,2- Dichloroethane
1,2-Dichloroethene (cis and trans)
1,1- Dichloroethene
1 , 1 , I-Trichloroethane
Silver
Trichloroethane
1,1,1,2- Tetrachloroethane
1,2-Dibromoethane
Acetone
1,2-Dichloroproparie
Toluene
2-Chlorotoluene
Xylenes (Total)
Ethylbenzene
Styrene
2-Butanone
Vanadium
17
1,2-Dichlorobenzene
Hexachlorobutadiene
bis(2- Ethylhexyl)phtalate
Di-n-Octylphthalate
Arsenic
Barium
Cadmium
Copper
Lead
Manganese
Mercury
Zinc
-------
Analytical data gathered from the residential wells and monitoring wells sampled indicated no
exceedances in groundwater of Federal MCLs for organic constituents. Among the inorganics,
only antimony exceeded the MCL; however, since the sample blank was contaminated, the
presence of antimony is questionable and antimony was not selected as a contaminant of concern.
B) ExDosure Assessment
Potential exposure to contaminants from the GTOS site was evaluated for the following potential
pathways or routes of exposure:
~
a) For site workers and site trespassers:
. Ingestion of soil
. Dermal absorption of contaminants in soils
. Incidental ingestion of sediments and surface water.
b) For residents:
. Ingestion .of soil
~I
. Ingestion of groundwater
. Dermal absorption of contaminants in soils
. Dermal absorption of contaminants in groundwater
. Inhalation of vapors from use of groundwater
. Incidental ingestion of sediments and surface water.
C) Calculation of Current and Future Risks
Current risks for receptor groups were based. on' concentrations of contaminants actually found
during monitoring in and around the site. For example, current risks for trespassers and site
workers use concentrations of contaminants found in the soil at the site during the RI. Current
risks to residents use concentrations found in the groundwater taken from residential wells.
Potential future risks for site workers and trespassers are based on the assumption that the known
current environmental concentrations remain the same. . Potential future risks for residents are
based on the conservative assumptions that future Concentrations of contaminants in residential
wells will be equal to the highest concentration of contaminants found in groundwater directly
under the site, and that a residence could be built directly on the site, potentially exposing adults
and children to contaminants in the soil through direct contact.
18
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o .
o
o.
D) Assumntions
..
Various assumptions were used for the perfonnance of the baseline risk assessment. By means
of the exposure assessment, actual and potential exposure pathways were identified to
characterize potentially exposed populations, and to determine the extent of exposure.
Behavioral and physiological factors influencing exposure frequency and levels are presented in
a series of exposure scenarios as a basis for quantifying contaminant intake levels by receptor
populations for each identified pathway ° The results of the exposure analysis are then applied
in the risk characterization. The scope of this risk assessment included an evaluation of both
current and future human health and environmental risks. All the assumptions used in the risk
assessment are explained in detail in the following sub-sections.
1. Exposure Pathways
The assessment of pathways by which human receptors may be exposed to contaminants from
the GTOS site includes an examination of possible contaminant source areas and existing
migration pathways and exposure routes, as well as those that may be reasonably expected in
the future. The determination of exposure pathways is made by a careful evaluation of the
current extent of contamination in and around the site in relation to local land and water uses,
and the results of a fate and transpon assessment that evaluates contaminant migration pathways.
:&0&
The site investigations perfonned at GTOS have confinned the presence of low levels of
contaminants of potential concern in soils and groundwater. The probable source of at least
some of this contamination, the former lagoons and the dry well located on site, have been
excavated and filled. The area has been covered in asphalt and gravel and is currently used as
a parking lot.
Contaminants detected at the GTOS site may migrate off site or may persist on site~ Some
contaminants of concern, such as the VOCs, are expected to be relatively mobile and may be
transponed from the soil to the groundwater. Once in the groundwater, these mobile
contaminants may be transponed down gradient. Other chemicals, such as the inorganics and
semivolatiles, are expected to be less mobile and may remain in the source area for much longer
periods of time.
Based on the evaluation of site characteristics it was determined that groundwater is the
contaminated medium of most concern on site and the most important mode of cont:tminant
transpon at OTOS. Fate processes, other than dispersion, volatilization, and adsorption, are
presumed to be insignificant in groundwater.
During rainy seasons, water can infiltrate contamina~ soils and carry dissolved organic and .
inorganic compounds with it. Part of the contaminants in the leachate is adsorbed by the soil
underneath the contaminated soil zone. The other part of the contaminants, which is desorbed
from the soil particles, continues to move downward and reaches the groundwater. However,
since the former lagoon areas at the site have been filled, and the area has been covered with
asphalt and gravel, percolation of rainwater through the asphalt is not expected.
19
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. 0
,
Contaminants in the surface soil are not expected to migrate directly from the GTOS site via
surface water as the site is relatively flat and the former lagoon areas are predominantly covered
with either asphalt or gravel.
".
Under current site conditions. volatilization is not expected to be significant because the asphalt
and gravel cover minimizes volatilization of the subsurface contaminants, and because the sandy
~oils at the site are more likely to lose contaminants through the leaching process.
Groundwater is expected to discharge to surface water with a significant loss of contaminants.
The distance from the site to the bay is less than 1/2 mile. As contaminated groundwater
migrates down gradient toward this discharge point, a significant loss of VOCs is expected
through volatilization, retardation and degradation.
Contaminants in the groundwater can volatilize to the soil pore spaces and finally reach the
surface of the soil and the surrounding air by diffusion. Volatilization from a water table aquifer
is affected by depth to the water table and moisture content of the unsaturated soil column.
Since the former lagoon areas have been covered with gravel and asphalt, volatilization from
groundwater to the air is not expected to be significant. .
:.i
Contaminants in groundwater which is pumped to the surface for use may volatilize directly to
the air. Contaminated groundwater used as a domestic or non domestic water supply could
result in a significant loss of contaminants through volatilization to the atmosphere. Through
agitation, heating, or other mechanical handling, VOCs would be expected to volatilize rapidly,
releasing contaminants. to the atmosphere.
A conceptual exposure model for the GTOS site, which integrates and summarizes the
information concerning source areas, contaminant migration pathways, and exposure routes into
a combination of exposure pathways is presented in Table 5. This model identifies the key
potential release mechanisms, transport media, exposure points, exposure media, exposure
routes, and receptors for each contaminated source. All potential exposure pathways and
receptors are included in this model, including some that were not quantified in the RI.
a) Risks from SoU
Site access is partially restricted by a 6 foot. fence which separates the site from the adjacent
schoolyard. This is not, however, expected to prevent 'children from entering the site.
Therefore, both site workers and child trespassers were examined receptor groups under the
current land use scenario.
Individuals entering the site for various reasons, including work activities or trespassing, may'
be exposed to contaminants by direct contact, especially during excavation activities.
Contaminants in the soils may be absorbed through the skin on contact or accidentally ingested
by unintentional hand to mouth activities.
Contaminants may be adsorbed through the skin as a result of direct contact with soil. The
degree of exposure is largely dependent on the concentration of the contaminant in the soil, the
exposed skin area, the absorption rate, and the frequency of contact with soil. Exposure is
expected to occur more frequently for workers, since the workers are present at the site more
20
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Tnhlr 5
Conceptual Exposure Modrl or
l.otrnll81l1umnn Exposure PlltI.woys
('ontaminated Release Transport Exposure Exposure Media/ Potential
Media Mechanisms Media Points Exposure Routes Receptors
Soil None None On-site Incidental Soil/Dust Ingestion She Worker I
I)ermal Absorption Trespasser I
Rcsident
{hollndwater None (jroundwater Off.site Ingestion and Derm.~ Residents
Absorption from Groundwater
{ifllllndwater Volatilization Air Ofr-sile Inhalation of Vapors while Residents
Showering
Sedimenls None NOlie Ofr.site Incidentallngcslioal Recreational.
Dermal Absorption Users/Residents/
Workers
Surface Water None NOllc Ort-site Incidenl allngcslioa/ Itccrealional
I>ermal Absorplion Users/Residenls/
Workers
"
,.
7.
.f
-------
. 0
regularly than children are. Adults are expected to receive' dermal exposures primarily while
conducting grounds maintenance, excavating, or trespassing at the site. Children may be
exposed to site contaminants while playing on the site grounds.
.0
b) Risks from Groundwater
Low levels of groundwater contamination have been detected in both down gradient residential
wells and down gradient monitoring wells. The highest concentrations of contaminants found in
the residential wells were the ones used to calculate risk under a current use scenario.
The use of groundwater for showering or other general washing and bathing activities may result
in inhalation exposures to contaminants rel~ as vapors. This is expected to be potentially
significant especially for the VOCs present in the aquifer. In addition, these same activities
result in either whole or partial body contact with contaminated water, potentially resulting in
absorption of contaminants through the skin.
The detailed quantification of exposures included analysis of water ingestion, inhalation, and skin
absorption. The current extent of exposure to residents by these pathways is low.
2. Recentors and Ouantification of Chemical Intakes
:J
The key receptor groups include the site worker, the child trespasser, and current and potential
future residents. Young children (0-6 years old) were chosen for evaluation based on their small
body size and increased sensitivity to contaminant exposure. Adults were also chosen for
evaluation, since certain exposures that would not be expected to result in adverse effects over
the shon term may result in potential problems after long term (chronic) exposure.
Estimated daily intakes of the selected contaminants of potential concern are calculated for each
of the exposed individuals identified for each exposure pathway. Daily intakes are calculated
separately for carcinogenic and non-carcinogenic effects in accordance with methodology
presented by EP A. Daily intakes for residential receptors are calculated separately for both a
child and an adult.
The degree of exposure via each pathway is determined by behavioral, chemical, and
physiological factors. Behavioral factors include the amount of time spent in contaCt with the
contaminants in soil and water. Chemical factors affecting the degree of exposure relate to the
tendency for a compound to be absorbed through the skin and the tendency for a chemical to
bioaccumulate, as well as the physical state of a chemical in the environment (e.g., solubilized
in water). Physiological parameters such as the condition of the skin (Le., degree of hydration
and skin breaks) and the ability of the body to metabolize, and eliminate the contaminants also
determine the amount and type of exposure that may occur.
D) Risk Characterization
The non-carcinogenic and carcinogenic health risks associated with each of the pathways and
potential receptors listed above have been evaluated. Basic toxicity information used to calculate
risk was derived from the Integrated Risk Information System (IRIS) and the Health Effects
Assessment Summary Tables (HEAST).
21
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" "
"
1. Non-cardnol!enic Health Risks
;,
Reference doses (RIDs) are daily exposure levels for humans, including sensitive individuals,
which have been developed by EP A for estimating the potential for adverse health effects from
exposure to chemicals exhibiting non-carcinogenic effects. RIDs are expressed in units of
mg/kg-day and are calculated for daily exposure over a lifetime. Estimates of actual intakes of
chemicals from environmental media (e.g., the amount of a chemical ingested from contaminated
drinking water) can be compared to the RID. RIDs are derived from human epidemiological
studies or animal studies to which uncertainty factors have been applied (e.g., to account for the .
use of animal data to predict effects on humans). These uncertainty factors help ensure that the
RIDs will not underestimate the potential for adverse non-carcinogenic effects to occur.
Potential concern for non-carcinogenic effects. of a single contaminant in a single medium is
expressed as the hazard quotient (HQ) (or the ratio of the estimated intake derived from the
contaminant concentration in a given medium compared to the contaminant's RID). By adding
the HQs for all contaminants within a medium or across all media to which a given population
may reasonably be exposed, the Hazard Index (HI) can be generated. The HI provides a useful
reference point for gauging the potential significance of multiple contaminant exposures within
a single medium or across media. Any HI value greater than 1.0 suggests that a non-carcinogen .
potentially presents an unacceptable health risk.
:.1
a) Noncarcinogenic I,Usks for Site Worker and Site Trespasser
The non-carcinogenic risks due to inorganic and organic contaminants associated with :site
worker and child trespasser exposures are summarized in Table 6. Current and future risks for
site worker and child trespasser exposures were calculated by assuming that future concentrations
of contaminants will be about the same as current levels. The total HIs for the site worker range
from 0.018 to 0.0026. The total HIs for the child trespasser range from 0.044 to 0.007. (Total
IDs are calculated by adding the RME inorganic to the RME organic, or by adding the RAE
inorganic to the RAE organic). Since all pathway specific and total non-carcinogenic HIs are
less than one, no significant non-carcinogenic health threat is expected. .
Table 6 Summary of Noncarcinogenic Health Risks
Associated with Site Worker and Site Trespasser
Exposure Scenario
Inorganic
RME- RAE-
Organic
RME RAE
Site Worker 0.0082 0.0018
. OJ)096 0.0008
Site
Trespasser
(Child)
0.024 0.0054
0.02
0.0016
* RME - Reasonable Maximum Exposure
.. RAE - Representative Average Exposure
22
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. 0
"
b) Noncarcinogenic Risks for Residents
The total non-carcinogenic HIs for current residential exposures range from 0.02 to 0.0084 for
adults and 0.047 to 0.024 for children. Since all pathway specific and total HIs are less than
one, there is no significant non-carcinogenic health threat associated with current residential use
of the groundwater.
The future noncarcinogenic risks associated with residential exposure for adults and children are
summarized in Table 7. The total adult HIs ranged from 0.99 to' 0.34. The total child HIs
ranged from 1.1 to 2.3. Although the total m does not exceed one for adults, the total m for
the child is greater than one. Ninety-five percent of this risk is derived from the inorganic
contaminants, including arsenic (HI=0.55) and zinc (HI=0.54). Arsenic exposure may result
in' dermal lesions. Zinc exposure has been found to lower the blood copper level, resulting in
hypocupremia. However, the toxicologies of the inorganic contaminants suggest that an organ
specific HI will not exceed one for the reasonably maximally exposed child.
~I
The primary exposure route under this scenario is ingestion of groundwater, the assumption.
being that the concentration of inorganic compounds found at the most contaminated monitoring
wells will become a source of drinking water. This could occur only if a drinking water well
were to be installed on-site directly into the upper, unconfined aquifer, or that contaminants
present in that aquifer were to migrate undiluted to an existing drinking water well off-site. No
drinking water wells presently exist in the unconfined aquifer from which the samples With
inorganic contaminants were taken.
Table 7 Total Future Noncarcinogenic Health Risks
Associated with Residential Exposure
for Adults and Children
Inorganic
RME RAE
Organic
RME RAE
Adults
Q.89 0.32
0.1
0.011
Children
2.1
1.1
0.26
0.04
2. Carcinol!enic Health Risks
Cancer potency factors (CPFs) have been developed by EPA's Carcinogenic Assessment Group
for estimating excess lifetime cancer risk associated with exposure to potentially carcinogenic
chemicals. CPFs, which are expressed in units of (mglkg-day)"l, are multiplied by the estimated
intake of a potential carcinogen, in mglkg-day, to provide an upper-bound estimate of the excess
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lifetime cancer risk associated with exposure at that intake level. The term "upper-bound"
reflects the conservative estimate of the risks calculated from the CPF. Use of this approach
makes underestimation of the actual cancer risk highly unlikely. Cancer potency factors are
derived from the results of human epidemiological studies or chronic animal bioassays to which
animal-to-human extrapolation and uncertainty factors have been applied (e.g., to account for
the use of animal data to predict effects on humans).
';0
Excess lifetime cancer risks for exposure to contamination at Superfund sites are determined by
multiplying the intake level with the cancer potency factor for each contaminant of concern.
These risks are probabilities that are generally expressed in scientific notation (e.g. 1 x lQ'6).
An excess lifetime cancer risk of 1 x 1 Q'6 indicates that, as a plausible upper-bound, an
individual has a one in one million chance of. developing cancer as a result of exposure to a
carcinogen over a 70 year lifetime under the specific exposure conditions at the site. EP A
generally attempts to reduce the excess lifetime cancer risk posed by a Superfund site to a range
of 1 x 10"" to 1 x 1~ (1 in 10,000 to 1 in 1 million), with emphasis on the most protective end
.( 1 x 1 Q'6) of the scale.
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Table 8 presents a summary of the carcinogenic risks due to inorganic and organic contaminants
associated with site soil exposure to both the site worker and child trespasser. The RI repon
assumed that the concentrations of contaminants in the soil and the land use assumptions are the
same for both current and future exposure scenarios. As a result, current and future risks were
assumed to be identical. The total carcinogenic risk to the site worker for all pathways (soil
ingestion and dermal absorption) combined range from 1.1 x 1~ to 8.0 X 10-8. Thereforei no
significant carcinogenic health risks to a site worker under these exposure scenarios are
expected. The highest cancer risk estimates are associated with the dermal absorption pathway,
which had a risk level of 1.1 x 1~ for the reasonably maximum exposure. Most of the
carcinogenic risk is due to bis(2-ethylhexyl)phthalate, which could potentially be a laboratory
contaminant. The total carcinogenic risk to the child trespasser for both pathways combined
range from 5.2 x 10-7 to 3.9 x 10-&. Under these exposure scenarios no significant carci~ogenic
health risks are expected to a child trespasser.
The total adult carcinogenic risk levels for all combined pathways under current residential
exposures range from 7.6 X 10"5 to 1.2 X 10"5. The highest cancer risks are associated with the
ingestion and dermal absorption of water. Similarly, the total child carcinogenic risk levels for
all pathways combined under current residential "exposure range from 3.2 x 1005 to 2.1 X 10"5.
Exposure to 1,2-dibromoethane accounts for more than 90 percent of the total pathway risk.
This contaminant was detected in one residential well (RW-30) at a level of 0.03 #Lgll. This
level is less than the proposed MCL of 0.05 #Lgll.
E) Environmental Risks
A preliminary ecological assessment was performed on the site. Based on the qualitative
analysis performed the risks associated with exposure to terrestrial, aquatic, and avian wildlife
species are .minimal. No species are currently, or expected in the future to receive, receiving
exposure to the contaminantS of concern.
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Table 8 Summary of Carcinogenic Health Risks
Associated with Site Worker and Site Trespasser
Exposure Scenario'
"
Inorganic
RME RAE
Organic
RME RAE
Site Worker NA
NA
l.lx10~ 8.0xlO-s
Site
Trespasser
(Child)
NA
NA
5.2x10.7 3.9xlO's
NA - Not Applicable
F) Risk Snmmarv
~.4
Based on the results of the Baseline Risk Assessment performed at the GTOS Site, EP A has
determined that conditions at the site due to organic compounds pose no significant current or
future risk to human health or the environment. The GTOS site does appear to exhibit u-ace
amounts of inorganic contamination which results in slightly elevated calculations of potential
future risk. The potential future risks discussed in the risk assessment are associated with
ingestion of drinking water contaminated with inorganic compounds, particularly arsenic and
zinc. Under this exposure scenario, the child future use, the HI would exceed one. The HIs
ranged from a RAE of 1.1 to a RME of 2.1.
It is important to note that the analysis performed is very conservative and that no contaminant
levels detected in any of the monitoring wells or residential wells exceeded MCLs. The Risk
Assessment assumes that the inorganic compound concentrations found in the groundwater will
eventually reach residential wells without dilution. This assumption is considered unlikely, as
the inorganic contamination was found primarily in the unconfined upper aquifer and all drinking
water wells are currently in the semi-confined'aquifer. Theoretically, the detected levels of
inorganics could be the result of background contamination.
. EP A makes risk management decisions based on a number of different factors, taking into
consideration specific site-related information as well as standardized methodologies for
calcul~tirig exposure and overall risk probability. In this, case, EP A has determined that the level
of inorganic contamination present at the GTOS site does not appear to pose an unacceptable
health risk to the public.
While EP A has determined that conditions at the site do not warrant further remedial action,
EP A will continue to monitor the groundwater for a period of twelve months.
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"
VIT. EXPLANATION OF SIGNIFICANT CHANGES
There are no significant changes from the recommended alternative described in the proposed
plan.
VITI. STATUTORY AUTHORITY FINDING
.
EP A has determined that conditions at the site due to contamination by organic compounds pose
no current or potential threat to human health or the environment. While the GTOS site does
appear to exhibit trace amounts of inorganic contamination which result in slightly elevated
calculations of potential future risk, EP A has also determined that the presen~ of these
compounds does not appear to pose an unacceptable risk to human health or the environment.
Accordingly, no funher remedial action will be undertaken. EPA will, however, continue to
monitor the inorganic contaminants in the groundwater for a period of tWelve months.
As this is a decision for "No Action", the statutory requirements of CERCLA Section 121 for
remedial actions are not applicable and no five year review will be undertaken.
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